Belgian Nuclear Research Centre Mol Belgium

Home , Balen, Dessel, Dolmen (miniseries), Geel, Kortenberg

BELGIAN NUCLEAR RESEARCH CENTRE MOL BELGIUM

30-49 SCK-CEN's core competence is nuclear research using complex infrastructures. The year 1997 saw the restart of our BR2 materials testing reactor after refurbishment (cover photograph) and the onset of the excavation of the second shaft to our underground research facility in clay. T"t ™ Y HE BELGIAN NUCLEAR RESEARCH CENTRE (SCK« CEN) is an institute y of public utility under the tutorship of the Belgian minister in JL charge of energy. About 600 highly qualified researchers and technicians realize an annual turnover of three billion Belgian francs, 50% being covered by a governmental subsidy and 50% by contract work and services for the Belgian and foreign industry and for the European Union.

The primary mission of SCK>CEN is research and development in the fields of the safety of nuclear installations, the safe handling and disposal of radioactive waste, and radiation protection and safeguards. It is converted in concrete projects, based on the current priorities of the Belgian authorities and of our customers.

The main current projects are, in the field of nuclear safety, • the behaviour of high-burnup and MOX fuel, mostly in collaboration with Belgonucleaire; • the embrittlement of reactor pressure vessels; • the irradiation-assisted stress corrosion cracking of reactor internals; • the irradiation effects on materials for fusion reactors; in the field of radioactive waste research, • the disposal in geological clay formations of high-level radioactive waste and of spent fuel; • the decommissioning of nuclear installations, in particular of the pressurized-water reactor BR3; • the study of alternative waste-processing techniques, such as transmutation; in the field of radiation protection and safeguards, • site and environmental restoration; • emergency planning and response; • scientific support to the programmes of the International Atomic Energy Agency (IAEA), of the Nuclear Energy Agency of the Organiza- tion of Economic Co-ordination and Development (NEA/OECD), and of the European Union.

Proper infrastructure is an important condition for the success of our scientific and technical projects. For our international programmes, the most important installations are the VENUS and BR2 reactors, and the underground research facility HADES.

The VENUS zero-power critical facility allows the detailed analysis of core configurations, including MOX fuel, and is used intensively by international programmes on reactor core code validation and on reactor pressure vessel dosimetry.

The BR2 reactor is a high-flux research reactor with thermal fluxes up to 1015 and fast fluxes up to 7 x lO^n-cm"2^"1. It is used for tests on structural materials and fuel in normal and accidental conditions for all types of reactors and for the fusion programme, and for the production of radioisotopes and the doping of silicon. After Board of Directors Scientific Co-ord. Frank Deconinck Frans Moons

Contract Mgmt Ludo Veuchelen General Manager Quality Assurance Paul Govaerts Peter Vermaercke General Secretary Operational Safety Robert De Cock Pascal Deboodt

Medical Services Luc Holmstock Radioactive Waste Reactor Safety & BR2 Operation & Cleanup Radiation Protect. Guy Collard Pierre D'hondt Pol Gubel

:. "Bernard Ne&rdael >< nfttimid: Aft: AbderraHim,; Technical Services Personnel, Marketing & ; Site;: ; ReacWr ;MateHa1s; -'"T]'^ Finances & Admin. Public Relations Jan Van der Auwera Christian Legrain Jef Vanwildemeersch : Nuclear;Chemistry; ; Reactor Experiments Leon XtarideVeide'.'•"•••.

; Radiatipriip : : replaced'ibyEr Roland Carchon "• Mark 166s ••'

Scientific Advisory Committee Yvan Bruynseraede, chairman Michel Giot, vice-chairman Paul Dejonghe Frank Deconinck, chairman of the board Paul Govaerts, general manager Frans Moons, scientific co-ordinator Chairmen of the DACs

;;; Departmental; Advisory Committees;(DACs) \

Waste Reactors Radiation Protect.

£ Vansant, chairman £ Mund, chairman C. Huyskens, chairm. J.De Schutter B. De Boeck F. Luykx L. Van den Noortgate C. Vandenberg A. Cremers J-Fuger W. D'Haeseleer P. Smeesters A Hermanne W. Bogaerts A. Janssens R. Jadot H. Van Dam A. Wambersie P. De Prefer D. Haas A. Piron

iv an intensive refurbishment programme, the reactor was restarted in April 1997 and is again at the disposal of international programmes for several years.

The underground research facility HADES, built in a deep clay layer 225 metres below our site, allows the study of the behaviour of clay, of waste containers, and of the migration of radionuclides in realistic conditions. In co-operation with the Belgian Waste Management company NIRAS/ONDRAF, an important extension of this laboratory is today under construction (the PRACLAY project), to demonstrate the feasibility of the disposal of heat-generating waste.

A study has been started with regard to the future construction of an accelerator-driven system, as a multipurpose neutron source for technological and medical applications, including research on transmutation of high-level radioactive waste (the MYRRHA project).

The current organization of SCK-CEN is tuned to the end users, with two major scientific divisions: • radioactive waste and cleanup, grouping the departments of waste and disposal, site restoration, nuclear chemistry, and safeguards; • reactor safety and radiation protection, grouping the departments of nuclear fuel, reactor materials, reactor experiments, and radiation protection.

The operation of the BR2 reactor, marketing, finances and administration, and general technical support are organized by specific divisions. Common support and control services such as scientific co-ordination, contract management, quality assurance, operational safety, and medical services are joined directly to the general management.

An external scientific advisory structure composed of experts in SCK-CEN's field of activities assists the board of directors, the general management, and the heads of divisions and departments. Its members are selected by the board of directors among the academic world and among senior actors of the nuclear community.

The scientific advisory structure is based on three departmental committees on radioactive waste, reactors, and radiation protection, overseen by a general scientific advisory committee. The latter can invite international experts to discuss specific topics.

This scientific report is structured according to specific activities in the above-mentioned scientific divisions and around BR2. Each chapter groups several related projects. Some cross-divisional activities are grouped under "Exploratory R&D." Each chapter indicates the general context and current achievements, the partners, and the scientific output. At the end of the report, indexes allow to search for individual partners and contributors. NEXT PAGE(S) left BLANK Abbreviations

Radiation Protection

Health-physics measurements 2 Radiological assessment and optimization 12 Radioecology 17 Environmental restoration 24 Health effects 26 Policy support on radiation protection 33

Reactor Safety

Nuclear fuel 36 Reactor physics 41 Reactor safety analysis 46 Reactor structural materials 48

Radioactive Waste and Cleanup

Waste management 60 Decommissioning of the BR3 PWR 69 Waste disposal 72 Safeguards 88 Radiochemistry 90

BR2 Operation

Refurbishment of BR2 (Phases 4 and 5) 94

Exploratory R&D

Fuzzy logic and intelligent technologies in nuclear science 100 Myrrha: a prototype accelerator-driven system 104 Improvement of in-pile instrumentation in experimental devices 106 Advanced instrumentation and teleoperation 107

Jesses 111 The following list explains the main abbreviations used in this report, such as SCK«CEN project names and common acronyms. By contrast, abbreviated names of organizations are explained in the index of partners, sponsors, and customers starting on page 118.

ABV Automatic Block Valves ADONIS Accelerator-Driven Operated New Irradiation System AES Auger Electron Spectroscopy ALARA As Low As Reasonably Achievable ARIANE Actinide and fission product Research In A Nuclear Element

BACCHANAL Burnup Accumulation for High-performing fuel ANALysis BACCHUS BACkfilling Control for High-level waste Underground Storage BIOMASS Biosphere Modelling and Assessment methods BIOMOVS Biosphere MOdel Validation Study BRl Belgian Reactor 1 BR2 Belgian Reactor 2 BR3 Belgian Reactor 3 BWR Boiling-Water Reactor

CALLISTO CApabiLity for light-water Irradiation in Steady-state and Transient Operation CARE Common Approach with regard to REstoration CERBERUS Control Experiment with Radiation for the BElgian Repository for Underground Storage CHIVAS CALLISTO Hot Irradiation of Vessel Alloy Steels CORiOLis COrrosion Related Irradiation Off-line for IASCC Susceptibility COSAC Contaminant Operation SAfety Capsule CRP Copper-Rich Precipitates CVN Charpy V Notch

DBTT Ductile-Brittle Transition Temperature DESTIN DEStructive Testing IN-pile loop DNA DeoxyriboNucleic Acid DOLMEN Device for On-Line MEasurement of Neutron flux D&D Decommissioning and Decontamination

ECLIPS Experimental Corrosion Loop for In-Pile Studies EDTA EthyleneDiamineTetraAcetate EIG Economic Interest Group EPMA Electron Probe MicroAnalysis

FL Fuzzy Logic FLC Fuzzy Logic Control FLINS Fuzzy Logic and Intelligent technologies in Nuclear Science

HADES High-Activity Disposal Experimental Site HLW High-Level Waste

IASCC Irradiation-Assisted Stress Corrosion Cracking ITER International Thermonuclear Experimental Reactor IVK Igarashi-Vitek-Kantha

VIII LFC Loss-Free Counting LHMA Laboratory for High- and Medium-level Activity LLW Low-Level Waste LOCA Loss-Of-Coolant Accident LWR light-Water Reactor

MOX Mixed OXide MPF Maturation Promoting Factor MTR Materials Testing Reactor

NAA Neutron Activation Analysis NDT Nil Ductility Temperature Nis Newly Independent States

OVERMOX OVERmoderated Mixed OXide

PCC Premature Chromosome Condensation PDWA Power Distribution Within Assemblies PEACE Programme for Evaluating the impact of Accidents Contaminating the Environment PHEBUS Phenomenology of Hydric Exchanges Between Underground atmosphere Storage host rock PHYMOL PalaeoHYdrogeology of the MOL site PIM Platelet Inhibitor Mixture PRACLAY PReliminAry demonstration test for CLAY disposal PSA Probabilistic Safety Assessment PWR Pressurized-Water Reactor

R&D Research & Development RECOVER RElevancy of COpse VEgetation for the Remediation of contaminated sites REDUP REDuction of 137Cs and 90Sr UPtake by grasses in natural meadows RESTRAT REstoration STRATegies RODOS Real-time On-line Decision support System RPV Reactor Pressure Vessel

SAFIR Safety Assessment and Feasibility Interim Report SAM Scanning Auger Microscopy SEM Scanning Electron Microscopy SPND Self-Powered Neutron Detector SPR SubPile Room SRC Short-Rotation Coppice

TF Transfer Factor TC ThromboGlobulin TGF Transforming Growth Factor TIA Time-Interval Analyser

VENUS Vulcain Experimental NUclear Study VIP VENUS International Programme VIPEX VIP Extension

WINES Water-Inelastic Neutron scattering Experimental Study

ix g§ „, M Mark Loos Health-Physics Measurements

TJT EALTH-PHYSICS MEASUREMENTS performs, Jk. A interprets, improves, and develops nuclear measurements related to people and the environment in normal and emergency situations. It bases its necessary expertise on in- depth research programmes and daily experience with complex and routine measurements.

Objectives • to improve health-physics measurement techniques by R&D, in particular in the field of neutron dosimetry, behaviour of radon progeny, and neutron activation analysis; m to maintain expertise in a wide range of health-physics measurements by continuous update of our competence; • to provide measurement services in the framework of both radiation protection and health-physics measurements.

Programme Health-physics measurements is divided into four areas, described separately hereafter: • neutron dosimetry; * radon in the indoor environment; • neutron activation analysis; • services.

Radiation Protection BE9900054 FUip VANHAVERE

Health-Physics Measurements Neutron Dosimetry

N RADIATION PROTECTION, there is growing neutron dosemeter covering the whole neutron Scientific staff I concern for neutron dosimetry. The ICRP 60 spectrum. We also looked at the influence Filip VANHAVERE publication introduced new, increased qual- of the new ICRP conversion factors (ICRP 60), Paul CUYNEN ity factors and lowered the annual dose lim- checked the sensitivity given by the manufac- Mark Loos its for radiation workers, thereby putting new turer, and concluded a three-year study on how demands on the already poor performance of ageing influences the bubble detectors' sensi- personal neutron dosemeters. tivity and temperature compensation.

Objectives Perspectives for 1998 While the study of the bubble detectors in neutron dosimetry • to improve the determination of neutron will be wrapped up in a PhD thesis, an auto- doses by studying neutron spectra, neutron matic reader will be developed for them. A new dosemeters, and shielding adaptations; project will study the possibilities of tissue- • to investigate the characteristics of bubble equivalent proportional counters for neutron detectors in order to use them as direct- measurements. reading neutron dosemeters.

Programme Our programme foresees • to conduct a dosimetric and spectral study Scientific partners Universiteit Gent (UG) — around the VENUS reactor; Institute for Reference Materials and Measure- • to evaluate the BD-PND and BDT bubble de- ments (IRMM) — Fraunhofer Gesellschaft, Institut tectors, in particular their lifespan and their fur Naturwissenschaftlich, Technische Trendanaly- dependence on temperature and energy; sen (FhG-INT) — Yale University — Vrije Universiteit Brussel (VUB) B to study the applications of the bubble detectors in practical situations.

Achievements The PGP albedo neutron dosemeter presently used around VENUS does Publications in 1997 not have a dose-equivalent response, thus requiring a correction factor dependent on F. VANHAVERE, M. LOOS, F. CALLENS, R. DEBUYST, the neutron spectrum. Because different ap- E. DE BOER, A. KLAASSEN, "A Local Intercomparison Study of ESR Dosimetry Using Tooth Enamel," Journal proaches yield different correction factors, the of Radioanalytical and Nuclear Chemistry 221:1-2, PGP neutron dosemeter may advantageously be 123-126 (1997). replaced by the more user-friendly bubble detector. This detector does not require a correc- F. VANHAVERE, F. VERMEERSCH, M. LOOS, H. THIERENS, tion factor, provides direct reading, and is as "The Calibration of Bubble Detectors," Proc. of the sensitive as a gamma dosemeter. During two int. conf. on Radiation Dosimetry and Safety, Taipei, years, we used both detectors in parallel, and Taiwan, Republic of China, 140-144 (1997). could map what activities cause doses to the workers. The bubble detectors are proposed Presentations delivered in 1997 as routine dosemeters around VENUS. F. VANHAVERE, "Evaluatie modellen van bellen- dosimeters en hun eigenschappen," Recente Evoluties We tested two types of bubble detectors: the in Neutronendosimetrie: Brussels, Belgium, April 18, BD-PND, sensitive to fast neutrons only (£ > 1997. 100 keV), and the BDT, predominantly measuring the thermal neutron dose. We determined F. VANHAVERE, "Measurement of the Energy Depen- the response of both to monoenergetic neutron dence of BD-PND and BDT Bubble Detectors Using beams, to thermal neutrons, and to four radio- Mono-Energetic Neutrons," Int. conf. on Nuclear Data nuclide sources. These results allowed us to for Science and Technology: Trieste, Italy, May 19-24, combine the two types into a dose-equivalent 1997.

Neutron Dosimetry BE9900055 Hans VANMARCKE

Health-Physics Measurements Radon in the Indoor Environment

Scientific staff URRENT ASSESSMENTS of health risks due trations with the three heads simultaneously. Johan PARIDAENS C to radon are based on epidemiological This yielded the relative response of the mea- Hans VANMARCKE studies of underground miners. A consensus suring heads: 1.00:1.056:1.055. Absolute cal- is growing that this is a questionable practice, ibrations were made by means of subsequent Supporting staff and efforts are being shifted towards a dif- alpha and gamma spectroscopy. The gamma Jean-Pierre AXZETTA ferent approach. There is a growing interest spectroscopy measurements were calibrated Paul WlLLEBORTS in performing epidemiological studies on the absolutely by means of a calibrated gamma general population, thus raising the question source of the same geometry as the measur- of assessing past radon exposures for such ing heads. They yielded absolute efficiencies populations. On the other hand, growing ef- of 13.1, 13.8, and 13.8% for the three mea- forts try to measure directly the amount of de- suring heads respectively, showing nice agree- posited radon progeny in different areas of the ment with the relative calibrations. respiratory tract. For the study of radon-progeny behaviour in radon chambers, we participated in an in- Objectives tercomparison exercise organized in the ani- • to investigate the deposition of radon prog- mal exposure chambers of the Laboratoire de eny in the human respiratory tract by means pathologie pulmonaire experimentale (LPPE) in of direct measurements as a function of Razes, near Limoges, France. Participants from aerosol conditions; Spain, Germany, France, Sweden, the United Kingdom, and Belgium measured radon con- • to assess the radon concentrations in build- centrations, equilibrium factors, and attached ings retrospectively with volume traps. and unattached fractions of radon decay products for various conditions in the two animal Programme The programme foresees the exposure chambers and in a separate animal direct measurement of deposited radon prog- room. We also used our bronchial dosemeter to eny in the human respiratory tract by means of assess the fractions of each of the radon decay the bronchial dosemeter, an instrument simu- products deposited in the nasal and bronchial lating the airflow in the respiratory tract. In a tract, for each of the conditions. One of the first stage, these measurements will take place purposes of this exercise was to assess the in- in the well-controlled environment of a refer- fluence of the presence of rats on the above- ence chamber, and in a second stage in real mentioned parameters. We found equilibrium field conditions (actual dwellings). factors between 0.18 and 0.47, nasal fractions between 2.0 and 16.8%, and bronchial fractions The retrospective assessment programme con- between 2.1 and 6.7% of total equivalent equi- sists in the development of the volume-trap librium concentration. No significant differ- technique, and is carried out in the frame- ences were seen between results with or with- work of the Radiation Protection Research pro- out rats present. All of the results are being gramme of the EC, more precisely as part of one elaborated centrally, and conclusions are ex- shared-cost action and two concerted actions. pected shortly.

Achievements In 1997, we calibrated the Figure 1 shows a typical curve for the deposited new measuring heads, developed to adapt the fraction of the equivalent equilibrium concen- bronchial dosemeter to the newly constructed tration as a function of the aerosol concentra- radon reference chamber. These calibrations tion in our own radon chamber. Future mea- had to be done with the utmost accuracy, be- surements will allow a better understanding of cause the results of the individual measuring the behaviour of radon decay products under heads have to be subtracted from one another various conditions. to assess the deposited fractions in different parts of the respiratory tract. We therefore per- Within the framework of the Radiation Protec- formed both relative and absolute calibrations. tion Research programme of the EC, we made The relative calibrations consisted in sampling further efforts to extend the applicability of the same mixture of radon-daughter concen- our volume-trap technique for assessing radon

Radiation Protection Figure 1 The deposited fractions of the equivalent for all of the considered sponges and still very equilibrium concentration as a function of the aerosol acceptable for the wood and cardboard sam- concentration in the SCK-CEN chamber. The nasal frac- ples. As we found, radon diffuses throughout tion increases markedly as the aerosol concentration sponges in only minutes, and through wood diminishes. and cardboard in typically a few hours. These times are always short compared to the lifetime of radon itself, which is a necessary condi- :;.; Deposited; fraction; { tion for the good functioning of a volume trap.

_• Nasal - All of this has largely increased our competence in retrospectively assessing past radon concentrations, making SCK>CEN a valuable partner for future epidemiological studies.

- -* • K i Bronchial • s Scientific partners Universiteit Gent (UG) — University of Lund — Swedish Radiation Protection ". i i i 1 i 1 • 1 1 1 • 1 Institute (SSI) — University College of Dublin — Commissariat a l'energie atomique (CEA)

Sponsor European Commission (EC), Radiation exposures in the past. More specifically, due to Protection Research programme, DGXII the great difficulties encountered in some areas to find spongy volume traps, we tried to extend the technique to other materials, such as wood or fibreboard. For this purpose, we performed new laboratory radon exposures on Presentations delivered in 1997 these two materials, with emphasis on using different types and densities of wood and fi- J. PARIDAENS, H. VANMARCKE, "Semi-Automatic breboard, of different sizes and shapes. The Counting System for Reading out Radon Measure- ments," European conf. on Protection against Radon idea was to see if a simple relationship between at Home and at Work: Praha, Czech Republic, June density, radon exposure, and measured 210Po 2-6, 1997. Proc, 164-167. activity could be found. The first results unfortunately indicate otherwise. It might how- F. TONDEUR, I. GERARDY, A. POFFIJN, G. MEESSEN, ever be possible to develop a simple test of H. VANMARCKE, J. PARIDAENS, S. OBERSTEDT, relatively short duration (a few days) to esti- S. HALLEZ, J.M. FLEMAL, A. DEBAUCHE, C. DE mate fairly accurately the relationship between LELLIS, "Belgian Intercomparison of Solid-State 210 radon exposure and detected Po activity for Radon Measurements," European conf. on Protection each separate sample. Therefore all samples against Radon at Home and at Work: Praha, Czech were first exposed separately to radon. From Republic, June 2-6, 1997. Proc, 262-266. subsequent exhalation data, information can be gained about the expected 210Po activity in H. VANMARCKE, M. VERLAAK, J. PARIDAENS, "Radon the sample. We will further investigate if this Concentrations in Limburg (Belgium)," European simple, straightforward test works for poten- conf. on Protection against Radon at Home and at tial volume traps of various kinds. Work: Praha, Czech Republic, June 2-6, 1997. Proc., 276-279. Another important characteristic of a good vol- Report published in 1997 ume trap is the speed at which radon can dif- fuse through the material. This has been tested J. PARIDAENS, "Semi-Automatic Counting System for for several types of sponges and for wood and Reading out Radon Measurements," SCK>CEN report fibreboard samples. The results were excellent (January 1997). BLG-729.

Radon in the Indoor Environment BE9900056 Stefaan POMME

Health-Physics Measurements

Neutron Activation Analysis with k0 Standardization

Scientific staff "K TEUTRON ACTIVATION ANALYSIS (NAA) is a ing, and measuring time, thus reducing cost Stefaan POMME i il sensitive and accurate tool for element and shortening the client's waiting time. Frank HARDEMAN analysis, complementary to non-nuclear ana- Jean-Pierre ALZETTA lytical techniques. The combination of the fa- As another further refinement of the fco meth- cilities of our gamma spectrometry laboratory odology, SCK- CEN developed a simple method and the reference neutron fields of our BRI re- for determining the burnup of certain neutron- actor constitutes an excellent framework for flux monitors in an unknown, intense neutron research on NAA. field. In particular, we showed how to evaluate the burnup effects involved in the neutron activation of 197Au prior to any neutron-flux Objectives characterization, based merely on the gamma- • to develop and implement the fco standardi- ray spectrometry of the 198Au and 199Au de- zation method for NAA, in close collabora- cay. In this way, the Au-Zr triple-monitor tion with scientific partners; method, which is the default neutron-flux characterization technique for fco-NAA,ha s been ex- • to exploit fully the inherent qualities of NAA tended to evaluate also the most extreme neu- such as accuracy, traceability, and multi- tron fluxes available in nuclear reactors. element capability, and to ensure its position as a competitive routine chemical In the trail of the fco-NAAresearch , the labo- analysis technique; ratory for gamma spectrometry benefits from m to acquire technical spin-off for our nuclear applying modern techniques, such as software measurements services, enhanced support to compute detector efficiencies for different possibilities to other internal projects, and geometries, a setup with fast electronics for be a stimulus for professional contacts with the spectrometry of rather active sources, and the international scientific community. Loss-Free Counting (LFC) modules with cus- tom spectrum-analysis software to correct for pulse count losses due to system dead time Programme In fco-NAA,th e normalization and pulse pile-up. Aspects of these advanced of the analytical result is based on so-called techniques are being scrutinized; for example, fco factors, associated with each gamma line SOOCEN participates in EUROMET Project 428 in the activation spectrum. These factors re- on the "Transfer of germanium detectors ef- place a series of nuclear constants, such as ficiency calibration from point-source geome- cross-sections and gamma-emission probabil- try to other geometries," using a (commercially ities, and are determined in specialized NAA available) semiempirical code. We also re- laboratories. This enhances the accuracy by search the statistics involved in time-distorted avoiding the unnecessary build-up of uncer- counting experiments of Poisson processes. tainties on the underlying physical constants. This pertains to about any nuclear measure- The fco factors are reactor- and detector-inde- ment with pulse losses due to dead time and pendent, and their values are agreed upon and pulse pile-up. Of special interest is the count- used by a growing number of fcouser s all over ing statistics found in LFC-corrected gamma the world. SCK»CEN is hosting an ongoing col- spectra. Our research already yielded unex- laboration with the university of Gent and DSM pected information, at variance with existing Research to determine fco factors for short- assumptions on nuclear counting processes. lived isotopes at the BRI fast-rabbit facility.

Achievements Together with IRMM, we took the first steps to (re)determine some fco factors. This fundamental work will make the Scientific partners Institute for Reference fco method applicable to additional elements, Materials and Measurements (IRMM) — Universiteit such as fluor, or to short-lived isotopes of Gent (UG) — Atomic Energy Research Institute of other elements, otherwise determined by their the Hungarian Academy of Sciences (KFKI) — DSM longer-lived isotopes. Using short-lived iso- Research BV — National Institute of Standards and topes drastically reduces the irradiation, cool- Technology (NIST)

Radiation Protection P. ROBOUCH, N. ETXEBARRIA, S. POMME, F. HARDEMAN, "The fco Newsletter," Proc. of the second int. fco Users Publications in 1997 Workshop, Ljubljana, Slovenia, September 30- October 3, 1996, 59-61 (1997). N. ETXEBARRIA, P. ROBOUCH, J. PAUWELS, S. POMME, F. HARDEMAN, "fco Achievements at IRMM and SCK- Presentation delivered in 1 997 CEN," Proc. of the second int. fco Users Workshop, Ljubljana, Slovenia, September 30-October 3, 1996, S. POMME, "Time Distortion of a Poisson Process and 137-141 (1997). Its Effect on Experimental Uncertainty," Int. Conf. on Radionuclide Metrology and Its Applications S. POMME, "Pulse Pileup and System Dead Time: (ICRM'97): Gaithersburg, Maryland, USA, May 19-23, Fundamental Aspects of Experimental Uncertainty," 1997. Proc. of the second int. fco Users Workshop, Ljubljana, Slovenia, September 30-October 3, 1996, 11-14 Reports published in 1 997 (1997). N. ETXEBARRIA, G. ARANA, P. ROBOUCH, S. POMME, S. POMME, F. HARDEMAN, N. ETXEBARRIA, P. ROBOUCH, "Analysis of Impurities in Ni Foils and Characteriza- "Performance Optimization of fco-INAA," J. Radioanal. tion of Neutron Flux in BR1-Y4," internal IRMM report Nucl. Chem. 215, 295-303 (1997). (1997). GE/R/MRM/02/97. S. POMME, F. HARDEMAN, P. ROBOUCH, N. ETXEBARRIA, S. POMME, F. HARDEMAN, P. ROBOUCH, N. ETXE- "The Application of Generalized Activation-Decay BARRIA, "Neutron Activation Analysis with fco- Formulas," Proc. of the second int. fco Users Standardization: General Formalism and Procedure," Workshop, Ljubljana, Slovenia, September 30 - SCK-CEN report (1997). BLG-700. October 3, 1996, 7-10 (1997). P. ROBOUCH, G. ARANA, N. ETXEBARRIA, S. POMME, S. POMME, A. SIMONITS, F. DE CORTE, P. ROBOUCH, "Mussel Tissue (CRM 278R) and Bovine Liver (CRM F. HARDEMAN, "Method for the Determination of 185R) by fco-NAA,"interna l IRMM report (1997). Neutron Field Monitor Burnup Effects by Gamma- GE/R/MRM/18/97. Spectrometry," Anal. Comm. 34, 133-135 (1997). P. ROBOUCH, G. ARANA, S. POMME, "PERM by fco-NAA: P. ROBOUCH, N. ETXEBARRIA, J.-P. ALZETTA, S. POMME, The Feasibility Study," internal IRMM report (1997). "A Step-by-Step fc0 Tutorial," Proc. of the second GE/MRM/19/97. int. fco Users Workshop, Ljubljana, Slovenia, Septem- ber 30-October 3, 1996, 71-74 (1997).

Neutron Activation Analysis with kg Standardization BE9900057

Frank HARDEMAN, Christian HURTGEN, Filip VANHAVERE, Hans VANMARCKE

Health-Physics Measurements Services

Scientific staff 1HE ACCURATE DETERMINATION of radiO- ibration of the apparatus by 1999. We revised Frank HARDEMAN Tactivity by direct or indirect measurement the Si(Li) measurement chain for X-ray analysis Christian HURTGEN of people and surfaces or by the measurement and prepared a variety of calibration sources of 55 Filip VANHAVERE of samples is an essential part of radiological Fe for an extensive calibration programme. Hans VANMARCKE protection. Being able to provide expertise in Jean-Louis GENICOT this domain for government and industry be- We summarized our systematic measurements Stefaan POMME longs to the mission of SCK«CEN. on radiocaesium contamination in air, rain, Freddy VERREZEN grass, milk, and humans in Belgium from the Jean-Pierre ALZETTA late 1950s to present day. The average impact Objectives Michel LAMPROYE of atmospheric nuclear weapon tests on the hu- Ludo MAES m to offer complete services in health-physics man body burden in our region was shown to Paul CUYNEN measurements according to international quality standards; Supporting staff B to improve continuously these measure- Karel HOFKENS i ;obd E ment techniques and to follow up inter- Beta in air Jef MERMANS national recommendations and legislation Edmond DUPUIS concerning the surveillance of workers; Karin JACOBS Myriam VERBIST • to support and advise nuclear and non- Rene VERKOYEN nuclear industry on problems of radioactive Diane VERSTREPEN contamination. August DAEMEN Eddy DANIELS Programme In the framework of health- Ingrld GEBOERS physics measurements, SCK>CEN provides sev- Paul WlLLEBORTS eral services, such as gamma spectrometry on Franciscus JANSSENS samples and humans, beta and alpha spec- : : Marcel VANDERLEYDEN trometry, dosimetry, and radon measurements. 1 000: 137Cs in grass Reinhard BOONS We also offer complementary services, valoriz- Marc VREYS ing existing infrastructure and competence: Julien VANDEWEYER instrumentation, calibration, standard source : i c Guy HOOYBERGS preparation, and neutron activation analysis. O;T :; - Raf AERTS

;ioo 137Cs in milk Gamma spectrometry SCK-CEN's gamma- spectrometry service performs measurements on low-radioactivity samples (environmental and reactor samples, foodstuffs, etc.), for internal and external clients. Since 1995, the service is accredited by Beltest as conforming 10 000: 137Cs body burden to the EN 45 001 standard for the quantification of gamma emitters by high-resolution gamma spectrometry.

In 1997, the number of gamma-spectrometry 1 1960:;; 1:970 ;: T980:: 1990" analyses on samples stabilized as compared to 1996: we performed a larger number of analyses for the BR2 and for external clients, but Figure 1 Monthly average of (from top to bottom) fewer for other research projects at SCK'CEN. beta activity in airborne dust measured at SCK'CEN, Mol, Belgium; 137Cs activity in airborne dust at SCK- At the end of 1997, we initiated the renewal of CEN; 137Cs activity in grass samples from a farm in the gamma-spectrometry section, by purchas- the vicinity of Mol (Dessel, Belgium); 137Cs activity in ing modern electronics equipment and soft- milk samples from the same farm; 137Cs body burden ware. We aim at a thorough update and recal- for a standard man of 70 kg.

Radiation Protection be more than six times that of the Chernobyl accident. The cumulated body burden from internal exposure to 137Cs was 154uSv between 1959 and 1986, and 25uSv between 1986 and 1997 (Fig. 1).

In 1997, some additional in situ gamma spectrometry measurements on the Belgian territory showed a clearer geographical correlation between the 137Cs activity level in soil and the rainfall on May 3, 1986 (Fig. 2). The ambient 137Cs gamma-ray field currently represents a dose of 0.6 to 7uSv a year.

Whole-body counting The laboratory for whole-body counting performs gamma spectrometry on humans to detect internal radioactive contamination. In 1997, we carried out a total of 1139 measurements: 959 with the large scintillator crystals for whole-body counting (523 for members of SCK« CEN and 436 We analysed over 1 500 urine and 30 faeces Figure 2 137Cs soil for others), 133 with the HPGe crystals for the 2 measurement of 241 Am in the lungs, 44 of ura- samples, not only for plutonium, but also contamination [Bq-m" ] for tritium, strontium, thorium, uranium, and measured at different lo- nium and 232/228-rh m tne iungs ^h Xhe 12" x americium. Eighty-five percent of these bio- cations in Belgium. The 4" scintillator and 3 of contaminated wounds. assay determinations were performed at the re- measured activity level quest of establishments outside SCK> CEN. The correlates well with the During 1997, we designed a new facility to per- remaining 15% were requested by SCK«CEN's rainfall on May 3, 1986. form the lung measurements in a tilted chair, Health-Physics Measurements group. We now instead of in supine position. This facility will perform all the actinide measurements by al- be operational at the beginning of 1998. pha spectrometry and have lowered the detection limit for plutonium down to 0.1 mBq per The research on the use of room-temperature 24 hours of urine. We analysed more than semiconductor detectors in in vivo counting 1 700 alpha spectra and routinely measured has been continued with the use of silicon airborne dust samples (daily), rainwater sam- diodes in array. The most important problem, ples (weekly), and environmental samples near namely the protection against electrical noise, nuclear facilities. has been mastered perfectly (Fig. 3). Different applications of CZT diodes have been studied In collaboration with ULg, we measured, after on actual cases: a wound contaminated with 241 tritium enrichment, very low activity levels of Am was controlled with a very low limit of tritium in underground water and in rain water. detection and a follow-up of the patient ad- 99m Some 110 water samples have been analysed in ministered with Tc for articulation control 1997. This tritium-dating facility is available to showed a long biological half-life of the marked geological and hydrogeological services. molecule in the tissues. Like previous years, we participated success- Beta and alpha spectrometry The Low- fully in an analysis intercomparison of tri- Level Radioactivity Measurement service uses tium, strontium, uranium, plutonium, ameri- low-background counters (liquid scintillators, cium, and curium in biological samples. We proportional counters, ZnS counters, and alpha also participated successfully in an intercom- spectrometers) to determine the low-level ac- parison measurement of "14C in the vent air of tivity of alpha- and beta-emitting radionuclides nuclear facilities" organized by Bundesamt fur in environmental and biological samples. Strahlenschutz (Germany).

Services Calibration The calibration service calibrates all radiation detectors at SCK»CEN. It also calibrates neutron monitors, gamma monitors, and electronic personal dosemeters for customers outside SCK'CEN. The Beltest accreditation of some calibration services is foreseen for 1998.

Instrumentation The instrumentation service is responsible for the maintenance of all the electronic measuring devices used in radiation protection at SCK«CEN. To install, for a client, a system to take representative and reliable samples in a new ventilation outlet, the instrumentation service studied the monitoring of the outlet, measured the air velocity, and constructed an isokinetic sampling tool. Figure 3 This array Dosimetry The dosimetry service is in of three silicon diodes charge of the personal dosimetry of more than Standard source calibration The standard with their preamplifier, 4 500 workers in different companies and hos- source calibration service of SCK'CEN can de- installed in a copper pitals, among which 800 are SCK« CEN workers. liver standards in almost any shape and ac- casing, is used for Moreover, we supply extremity and environ- tivity for most commonly available isotopes. the determination of mental dosemeters, all of which operate on the The radioactivity is traceable to international internal contamination thermoluminescence principle. reference laboratories. The absolute calibra- in humans. The left tion is based on a 4TT proportional counter part of the casing A test programme investigated the need for with gamma coincidence as primary technique hosts the noise filter the introduction of a special beta doseme- and a calibrated Nal well detector for integral circuit. ter as routine personal dosemeter. This beta gamma counting as secondary technique. A 2TT dosemeter has a special thin filter in front of windowless alpha detector is used for calibra- a thin TLD detector. Laboratory tests showed tion of solid alpha sources. that it indeed detects low-energy beta rays better than the normal routine dosemeter. Dur- Neutron activation analysis SCK-CEN ing a nine-month test period, these dosemeters performs elemental analyses for the industry were used by people working with low-energy and for research projects by neutron activation X-rays and beta rays in a hospital, showing min- analysis. The combination of the facilities of imal doses coming from beta rays to the work- our gamma-spectrometry laboratory and the ers. Nevertheless, the beta dosemeters are now reference neutron fields of our BRI reactor con- used in practice for a small number of people stitute an excellent framework for exploiting liable to receive some beta dose. this technique. The main achievement in 1997 was the implementation of the fco methodol- Radon measurements SCK>CEN's radon ogy; besides two HPGe detection setups for the group offers customized solutions in the area analysis of long-lived isotopes, we also assem- of radium and radon contamination. It can per- bled a new setup for short-lived isotopes at form long-term and short-term radon measure- the fast-rabbit system in channel S84 of the ments in indoor and outdoor environments on BRi reactor. A typical commercial applica- behalf of industry, authorities, and the general tion was the analysis of fluor (Ti/2 = 11 s) in population. liquids.

10 Radiation Protection S.A. MIHAI, G. SHAW, I.I. GEORGESCU, C. HURTGEN, "Correlated Concentration Distributions of Natural Scientific partners Universiteit Gent (UG) — Alpha Radionuclides in Sediment Samples along the Vrije Universiteit Brüssel (VUB) — Université de Romanian Sector of the Danube River and the Black Liège (ULg) — Belgoprocess (BP) Sea Coast," Journal of Radioanalytical and Nuclear Chemistry 221:1-2, 203-205 (1997). Customers Belgonucléaire (EN) — Franco-belge J. UYTTENHOVE, S. POMMÉ, B. VAN WAEYENBERGE, de fabrication de combustibles International (FBFC F. HARDEMAN, J. BUYSSE, J.-P. CULOT, "Survey of Int.) — Belgoprocess (BP) — Kerncentrale Doel (KCD) — the 137Cs Contamination in Belgium by In-Situ Centrale nucléaire de Tihange (CNT) — Institute for Gamma Spectrometry, A Decade after the Chernobyl Reference Materials and Measurements (IRMM) — Accident," Health Physics 73, 644-646 (1997). Contrôle de sécurité de l'Euratom (CCE)

Presentations delivered in 1 997

J.-P. CULOT, W. BLOMMAERT, C. HURTGEN, J.-P. MINON, "Follow-Up of an Old Contamination Case," Workshop Book published in 1997 on Intakes of Radionuclides Occupational and Public Exposure: Avignon, France, September 15-18, 1997. F. VERREZEN, C. HURTGEN, "Radioassay of Low-Level, Low Energy Beta Activity in Multilabeled Samples J.-L. GENICOT, "Room Temperature Semiconductor Containing High-Energy Impurities Using Liquid Detectors in Whole Body Counting," DOE Lung Scintillation Spectrometry," in: G.T. Cook ef al, Intercalibration Committee: Savannah River Site, eds., Liquid Scintillation Spectrometry, 381-389 South Carolina, USA, May 5-8,1997. (Radiocarbon 1996). J.-L. GENICOT, "Room Temperature Semiconductor Detectors: New Techniques for the Monitoring of Publications in 1997 Internal Contamination's and Applications in Nuclear J.-L. GENICOT, "Room Temperature Semiconductor Medicine," First scientific meeting of the Brazilian Detectors for In-Vivo Monitoring of Internal Contami- Society of Nuclear Biosciences and second scientific nation in Environmental Health Perspectives," Proc. meeting of Biophysics and Biometry: Rio de Janeiro, of the int. conf. on Radiation and Health, Beer Sheva, Brazil, November 17-20, 1997. Israel, November 3-7, 1996. Environmental Health S. POMMÉ, J. UYTTENHOVE, B. VAN WAEYENBERGE, Perspectives 105:6, 1423-1426 (1997). J.-L. GENICOT, J.-P. CULOT, F. HARDEMAN, "Radiocae- J.-L. GENICOT, J.-P. ALZETTA, "New Technique Using sium Contamination in Belgium," Fourth int. conf. Room Temperature Diodes for the Direct Assessment on Methods and Applications of Radioanalytical of Internal Contamination by Low Energy Gamma- Chemistry (MARC-rv): Kailua-Kona, Hawaii, USA, April Ray Emitters," Appl. Rad. Isot. 48:3, 349-358 (March 6-11, 1997. 1997). Report published in 1997 S.A. MIHAI, C. HURTGEN, "Plutonium and Americium in Sediment Samples along the Romanian Sector of M. Loos, M. LAMPROYE, "Studie van de schouwmoni- the Danube River and the Black Sea Coast," Journal toring voor gebouw 5 FBFC," contract study for FBFC of Radioanalytical and Nuclear Chemistry 222:1-2, (1997). AH/0054/2326/TD. 275-278 (1997).

Services 11 BE9900058

Theo ZEEVAERT, Alain SOHIER Radiological Assessment and Optimization

Scientific staff "ITHIN THE NUCLEAR-FISSION SAFETY do- to organize courses on off-site emergency Theo ZEEVAERT ' main, there are still ample needs for R&D response to nuclear accidents. Alain SOHIER work to optimize the radiological protection of Carlos ROJAS PALMA the population and the environment. Hildegarde Programme Within the framework of VANDENHOVE Radiological optimization is one of the basic the fourth EC Radiation Protection Research Bartel VAN DE WALLE principles in each radiation-protection system. Programme (DGXII), SCK«CEN co-ordinates the Lieve SWEECK It is a basic requirement in the safety stan- project RESTRAT (REstoration STRATegies for Nicolas LEWYCKYJ dards for radiation protection in the EC and radioactive-contaminated sites and their close Jan ROTS has been laid down in the legislation of many surroundings) and participates in the devel- European countries, including Belgium. How- opment of RODOS (Real-time On-line Decision Supporting staff ever, its implementation and practical applica- Support system), a comprehensive decision- Eliane VANGELDER tion still pose many problems, which SCK-CEN support system for nuclear accidents in Eu- Els TESSENS contributes to overcome through this project. rope. Rene BUBBE Radiological assessments constitute an impor- RESTRAT chiefly aims to develop a generic meth- tant part of radiological optimization. Areas odology for ranking restoration techniques as needing such evaluations include accidental re- a function of site characteristics in a radiologi- leases and environmental site contaminations, cal optimization framework. It uses five con- and land disposal of radioactive waste. In taminated sites as example cases: the Drigg case of an accidental release into the atmo- disposal site (United Kingdom), the Ravenglass sphere, expected radiological consequences to estuary (United Kingdom), the Ranstad tail- the population have to be assessed both in the ing site (Sweden), the lake Tranebarssjon at early phase, as soon as possible, and in the Ranstad (Sweden), and the river Molse Nete late phase, to introduce appropriate counter- (Belgium). measures or remedial actions. Techniques are under development to assimilate early off-site RODOS aims to assimilate and analyse continu- monitoring data to obtain a comprehensive pic- ously data and information (for example, plant, ture of the main contamination and dose fields. meteorological, and monitoring data) during the progression of an accident. It predicts the actual and future environmental contami- Objectives nation fields, establishes a ranked list of feasi- • to implement the ALARA principle in activi- ble countermeasures, based on preselected cri- ties with radiological consequences; teria, and indicates the advantages and draw- backs of each countermeasure, as guidance for • to develop methodologies for radiological decision-advisors and decision-makers. SCK- optimization in decision-aiding; CEN's contribution is related to the quasi real- • to optimize radiological assessment models time assessment of the radiological situation in by validation and intercomparison; the environment during the early phase, based on the comparison of model predictions with m to improve methods to assess in real time limited environmental-monitoring data sets in the radiological hazards in the environment the near field (less than 30 km). in case of an accident; • to develop methods and programmes to as- Our department also carries out, on behalf of sist decision-makers during a nuclear emer- the EC (DGXI), a study contract called CARE (in- gency; vestigation of possible basis for a Common Ap- proach with regard to the REstoration of areas • to support the policy of radioactive waste affected by lasting radiation exposure as a re- management authorities in the field of ra- sult of past or old practice or work activity). diation protection; The contract foresees four major tasks: the • to investigate (with a view to the applica- identification of areas concerned, the assess- tion) existing software programs in the do- ment of radiological impacts for normal evo- main of multicriteria analysis; lution and accidental scenarios, the identifica-

12 Radiation Protection tion, characterization, and selection of restora- • elaboration of a risk-assessment model; tion options, and the derivation of intervention • selection of restoration options; criteria. SCK»CEN contributes to Tasks 1 and 3 • elaboration of a manual. (physical restoration options). In addition, we have been mostly involved in In the field of impact assessment of radioactive documenting physical restoration techniques contaminations or releases of radioactive sub- and describing and characterizing the example stances in the environment, our department case of the river Molse Nete. optimizes models for evaluating biospheric concentrations and doses to man. To keep in The physical restoration techniques were clas- touch with the international developments in sified in four categories: physical removal that field and to upgrade our assessment mod- of sources; physical separation of contam- els, we are participating in international vali- inated fractions (soil washing, flotation, fil- dation studies (see BIOMASS in "Environmental tration); containment (capping, subsurface Restoration," page 24). barriers, wet covering, dry barriers); physical immobilization (cement-based immobiliza- On behalf of Belgian nuclear operators and in tion, grouting). Their relevant characteristics- consultancy with the responsible authorities applicability, performance, costs, and side- for the national emergency plan, SCK«CEN is effects—were determined and quantified. continuously involved in the definition of improved methodologies and new software tools The example site of the river Molse Nete has to assess the radiological consequences in case been described in geographical, geological, hy- of accidental releases. drological, pedological, meteorological, and demographical terms. The relevant physico- Radiological optimization studies are also re- chemical parameters have been identified and quired for the restoration of radioactively con- quantified. The radioactive source term and taminated sites (see "Environmental Restora- environmental contamination of the area were tion," page 24) and shallow-land burial of ra- documented. dioactive waste, as a support to the policy of the competent authorities (decision-aiding). As far as SCK«CEN's involvement is concerned, the characterization of the Molse Nete site will Regarding the behaviour of radiocaesium in be finalized in 1998, a list of applicable restora- soils (natural, seminatural, and agricultural tion techniques for the example sites drawn up, ecosystems), a PhD thesis aims to develop a dy- and their characteristics quantified. Also the namic multisite, multireaction retention model elaboration of the manual will be tackled. based on the fundamental physicochemical caesium sorption properties on clay minerals. This model will predict the time evolution of Real-time assessments Within the frame- the bioavailable fraction of the radiopollutant work of the RODOS project, we translated into present in the soil compartment as a function a stand-alone PC programme a global method- of the soil characteristics. ology to assimilate early environmental data in order to assess in quasi real-time the main en- The development of group support systems is vironmental contamination fields following a a new important item in our programme. release at a nuclear power plant. The methodology, already described in SCK-CEN's 1996 Scientific Report, is based on the compari- Restoration strategies In the framework son between off-site near-range monitoring of RESTRAT, SCK-CEN co-ordinates the tasks in data and the corresponding model predictions, the various working packages: and gives an estimate of the source term. • example case studies; This source term is subsequently used in a • physicochemical phenomena governing the dose/dispersion model to yield rapidly a global behaviour of radioactive substances; spatiotemporal picture of the contamination • documentation on restoration techniques; fields. Taking into account the likeliness of

Radiological Assessment and Optimization 13 obtaining off-site measurements in real time and titanium oxide industry, zirconium and ce- in sufficient amount, the use of simultaneous ramics industry, and disposal of building ma- short-term averaged gamma dose rates from terials. Existing information on the process, automatic real-time fence monitoring systems scale of the industry and levels of naturally oc- forms the kernel of the method. curring radioactive materials in feed materials and waste and by-products was collated and Because gamma dose rates are only liable to issues of past and old practices were empha- give information about the global source term sized. The radiological impact (releases and without differentiating into its composing ra- pathways), mainly of radionuclides of the 238U dionuclides, we examined whether the use of and 232Th decay series, was considered. The in situ gamma spectrometry to monitor a radio- occurrence in European countries was inven- active plume could generate the required com- torized. plementary information. In situ gamma measurements tracked the routine release of 41Ar Specific sites were selected and fully described from SCK>CEN's BRi reactor as a tracer. Using for the first five categories: Sillamae (Esto- the measurements and on-site weather mast nia) for uranium mining and milling; Mans- data in conjunction with developed methods, feld (Germany) for metal mining and smelt- the calculated source term estimations glob- ing; London (United Kingdom) for application ally gave satisfactory results, considering the of radium and thorium; Freital (Germany) for requirements of an accidental situation. Al- coal mining and power generation from coal; though more research is necessary to consider Tessenderlo (Belgium) for the phosphate in- the full complexity of a real accident, monitor- dustry. ing the cloud using in situ gamma spectrometry is thus liable to generate truly useful in- Radiological impact assessments are being per- formation for use during the early phase of a formed for these sites for the undisturbed case nuclear emergency. and after remediation, and the results generalized to the categories (Westlakes). They will be In 1997, the RODOS prototype version PRTY 2.0 used for the development of cleanup criteria has been installed at SCK>CEN. (Ris0).

In the future, we will refine the methodology As main task for 1998, SCK-CEN will draft the developed so far within the RODOS project to final report, intended to be submitted to and consider the complexity of real accidental sit- discussed within the Article 31 group. uations. We will implement the stand-alone module into RODOS and give some attention to the type of uncertainty which could be es- Modelling of radiocaesium behaviour in timated and transmitted to decision-makers soils During 1997, the dynamic three- during the acute phase of a nuclear emergency. site model developed in 1996 was improved; it now takes into account radiocaesium retention onto clay minerals on a long-term basis Common approach to restoration The (six months). On the basis of experimental contribution of SCK-CEN to the CARE study has results obtained under well-controlled labora- been mainly the identification of the areas of tory conditions (see "Radioecology," page 17), concern. We gave an overview of industrial ac- we added a process characterizing very rapid tivities involving the extraction and processing sorption and retention of radiocaesium on of materials which may contain enhanced lev- highly specific sites and adjusted the kinetic els of naturally occurring radioactive materials. constant describing the interactions between The different liabilities were subdivided in nine the different pools of sorption on a long-term categories: uranium mining and milling, metal basis, this for the four clay minerals studied in mining and smelting, application of natural 1996 (illite, bentonite, biotite, and vermiculite). radionuclides of radium and thorium, phosphate industry, coal mining and power gener- The model, tested on three other 2:1 clay mination from coal, oil and gas drilling, rare-earth erals (beidellites), allowed qualitative ranking

14 Radiation Protection of the different kinetic constants involved and sis and Modelling" and "Emergency Room" sub- the establishment of ranges of variation for projects of the new Emergency Planning and these parameters. The results were in very Policy Support project NORD at the Radiation good agreement with the clay structure of the Protection department. investigated materials. Training In the framework of the European We also focused our attention on the effect of Radiation Protection Education and Training competition occurring when different clay min- (ERPET) programme of the EC Radiation Protec- erals (illite, vermiculite, and biotite) are mixed tion Research programme (DGXI), we organized in different proportions (50-50% and 30-70%). a seventh training course on off-site emer- The competition effect between the different gency planning and response to nuclear acci- pools of sorption was clearly pointed out by dents at SCK'CEN in July. Under the auspices the values of the parameters provided by the of the same programme, SCK« CEN was invited modelling. to Ljubljana (Slovenia) by the Jozef Stefan In- stitute to give a similar course for an audi- Furthermore, we studied the effect of the pH ence from South-East Europe in September. An on radiocaesium retention. The results show eighth training course and a similar one in Ro- clearly that, at lower pH, desorption of radio- mania are foreseen for 1998. caesium occurs from the specific and highly specific sites.

Finally, we analysed the effect of inert material for radiocaesium sorption and retention, by mixing quartz to illite in different propor- Scientific partners Forschungszentrum tions. The sorption and desorption processes Karlsruhe (FZK) — National Radiological Protection were slowed down as a function of the quartz Board (NRPB) — Riso National Laboratories — content. These results show the need to im- University of Leeds — University of Manchester — prove the model for such interactions. University of Warwick — Electricite de France (EdF) — KEMA Nuclear — Centre d'etudes sur 1'evaluation de la protection dans le domaine nucleaire (CEPN) — Nuclear emergency plan Within the frame- Scientific Production Association Typhoon (SPA work of the Belgian nuclear emergency plan, Typhoon) — EC Joint Research Centre (JRC) — SCK> CEN started to develop the PC model Nood- Jozef Stefan Institute — Universite catholique de plan Doel V2.0 on behalf of the Doel nuclear Louvain (UCL) — Universiteit Gent (UG) — Westlakes power plant. The model follows up a radio- Scientific Consulting (WSC) — Studsvik Eco&Safety — active release based on real-time stack moni- Forschungszentrum Rossendorf (FZR) toring and meteorological data. It is able to differentiate between the total dose expected and other participating institutes in BIOMOVSII from the release and the dose still avertable by forthcoming intervention. This PC model will Sponsor European Commission, Radiation be finalized in 1998. We started negotiating Protection Research programme, DGXI and DGXII the construction of a similar programme for the Belgian Institut des radioelements (ERE). Customers Electrabel — Belgoprocess (BP) — Belgonucleaire (BN) — Institute for Reference Ma- terials and Measurements (IRMM) — Nationale Croup support systems As regards the Instelling voor Radioactief Afval en Verrijkte Splijt- development of group support systems, one of stoffen/Organisme national des dechets radioactifs our sientific researchers paid a six-month visit et des matieres fissiles enrichies (NIRAS/ONDRAF) to the Collaborative Systems Laboratory at the New Jersey Institute of Technology. He studied the technology and the theory of group support systems, and in particular analysed their decision analytic opportunities. Applications are being developed for the "Decision Analy-

Radiological Assessment and Optimization 15 C. ROJAS PALMA, A. SOHIER, J. PAULY, "Current Devel- opments in Off-Site Source Term Estimation for Nu- Publications in 1 997 clear Emergencies," Conf. on Severe Accident Risk and Management: Piestany, Slovakia, June 16-19, 1997. M. AHLBRECHT et al, A. SOHIER et ah, "Decision Support Issues in RODOS: The Needs of Deci- A. SOHIER, A. JONES, I. HASEMANN, J. VAN DER sion Makers," Radiat. Prot. Dosim. 73:1-4, 81-84 STEEN, "On the Use of the Avertable Dose Concept (1997). in COSYMA," Technical committee on Special Topics Related to Level-3 PSA/Dose Calculations: Vienna, C. ROJAS PALMA, A. SOHIER, "Off-Site Consequence Austria, August 25-29, 1997. Analysis Based upon the Projected Doses Associated with Different Core Damage Scenarios," Radiat. Prot. B. VAN DE WALLE, B. DE BAETS, E. KERRE, "A Dosim. 73:1-4, 269-272 (1997). Comparative Study of Completeness Conditions in Fuzzy Preference Structures," Seventh Int. Fuzzy J. SMITH ef ai, C. ROJAS PALMA, A. SOHIER, Systems Association world congress (IFSA'97): Praha, "Probabilistic Data Assimilation within RODOS," Czech Republic, June 25-29, 1997. Proc. 4, 74-79. Radiat. Prot. Dosim. 73:1-4, 57-59 (1997).

A. SOHIER, C. ROJAS PALMA, X. Liu, "Towards Thesis published in 1997 a Monitoring Framework for the Source Term J. PAULY, C. ROJAS PALMA, A. SOHIER, "Source Term Estimation During the Early Phase of an Accidental Estimation Based on In-situ Gamma Spectrometry Release at a Nuclear Power Plant," Radiat. Prot. Using a High Purity Germanium Detector," final-year Dosim. 73:1-4, 231-234 (1997). thesis, Nuclear Engineering (Fachhochschule Aachen), 1997. Presentations delivered in 1997

B. DE BAETS, B. VAN DE WALLE, "Fuzzy Preference Lectures taught in 1 997 Modelling Based on Continuous de Morgan Triplets," A. SOHIER, "Off-site Emergency Planning and First int. workshop on Preferences and Decisions: Response to Nuclear Accidents," ERPET Training Trento, Italy, June 5-7, 1997. Proc, 15-20. Course: Mol, Belgium, June 23-27, 1997 and B. DE BAETS, B. VAN DE WALLE, "Minimal Definitions Ljubljana, Slovenia, September 29-October 3, 1997. of Classical and Fuzzy Preference Structures," Annual B. VAN DE WALLE, "Beslissingen onder onzekerheid," meeting of the North American Fuzzy Information Seminar Series in Statistics: Universiteit Gent, April Processing Society (NAFIPS'97): Syracuse, New York, 14, 1997. USA, September 21-24, 1997. Proc, 299-304. B. VAN DE WALLE, "Decision analysis": New Jersey B. DE BAETS, B. VAN DE WALLE, E. KERRE, "A Two- Institute of Technology, Computer and Information Parameter Class of Fuzzy Preference Structures," Int. Science Department, September-December 1997 conf. on Methods and Applications of Multicriteria (ten lectures). Decision Making: Mons, Belgium, May 14-16, 1997. Proc., 196-199. B. VAN DE WALLE, "Wiskundige programmering en multi-criteria analyse," Tweede licentie economis- N. LEWYCKYJ, B. DELVAUX, "A Quantification of the che wetenschappen en toegepaste economische Time-Dependent Retention of Radiocaesium Traces wetenschappen: Universiteit Gent, April 1997 (two in Different Clay-Solution Systems," 27th annual lectures). meeting of the European Society for New methods in Agricultural research (ESNA), jointly organized Report published in 1997 with the Union Internationale de Radioecologie (UIR). Working Group 3: Soil-Plant Relationships: Gent, Th. ZEEVAERT, A. BOUSHER, "Restoration Techniques: Belgium, August 29-September 2, 1997. Proc., Characteristics and Performances," RESTRAT, Techni- 128-134. cal Deliverables 3 and 4 (October 1997). KNT9095 672.

16 Radiation Protection BE9900059

Christian VANDECASTEELE Radioecology

OOD CHAINS are important contributors to The Woodmode project, a bilateral scientific Scientific staff F the radiological dose of populations ex- collaboration between SCK>CEN and PSI, con- Yves THIRY posed to radionuclides released from the nu- cerns the study and the modelling of radio- Christian VANDECASTEELE clear fuel cycle. To assess reliably the radiocaesium and radiostrontium accumulation in Hildegarde VANDENHOVE logical exposure through the diet, to suggest timber wood of pine forest trees. Indeed, the May VAN HEES sound remedial actions to limit the contami- forest ecosystem, like other perennial cultures Nicolas LEWYCKYJ nation levels in aliments and/or to rehabili- with a high biomass density, acts as a reser- Gao JIMING (trainee) tate contaminated areas, one must gain knowl- voir of radionuclides. Forests, including the Annick GOMMERS edge of the radionuclides' behaviour in the en- contaminated forests in the NIS, are generally Nadia WAEGENEERS vironment and of their transfer mechanisms exploited for their wood. Reliably predicting through the ecosystem components. the production of contaminated biomass from Supporting staff polluted forests is the main challenge for for- Paul BENS est management strategies. The effect of tree Jozef SANNEN Objectives age and growth yields on the accumulation • to evaluate, by means of laboratory and field of radionuclides in timber is capital, but few experiments, the mechanisms and dynam- models, even in the NIS, adopted a rigourous ics (fluxes) of radionuclide transfers in the approach to validate or illustrate their impor- biosphere, considering all circumstances af- tance. fecting the transfer parameters and their variability (source term and ecosystem, sea- Finally, the group develops expertise on the sonality, ageing, countermeasures, etc.); application and effectiveness of countermeasures through internal R&D programmes (PhD m to suggest the most appropriate counter- theses and postdoctoral work) and makes it measures to reduce the transfer of radio- available to students and professionals from nuclides through the human and animal related fields (public and private) through lec- food chain and to test experimentally their tures at the universities of Brussels and liege feasibility and effectiveness; and through training courses. • to provide the national and international authorities with adequate information, enabling them to assess reliably the conse- PEACE The PEACE (Programme for Evalu- quences of routine and potential accidental ating the impact of Accidents Contaminating releases for populations, and to select the the Environment) programme studies the soil- most adequate mitigating actions; plant interface processes governing the transfer of radiocaesium and radiostrontium to food • to educate professionals, students, and the crops after an accidental deposition of radio- public on the different aspects of radioactive aerosols. In case of soil radiocaesium ecology through lectures, conferences, and contamination, a considerable part of the vari- pamphlets. ation in soil-to-plant Transfer Factors (TFs) can be related to variations in the solid-liquid par- Programme The Radioecology research tition coefficient Kdsim. This parameter inte- team is involved in several international collab- grates different processes governing the radio- orative programmes supported by EC contracts caesium mobility in soil and depends on the (PEACE, REDUP, RECOVER). These programmes soil solution composition. Soil moisture con- deal with the transfer of radionuclides in agri- tent plays an important role since it affects the cultural ecosystems and ultimately aim at de- concentration of both the radionuclides and fining the most effective countermeasures. their competitive cations. SCK«CEN investigates the quantification of the dynamics of the soil- In addition, the team also researches, under solution composition, in terms of both concen- contract from NIRAS/ONDRAF, the biospheric trations of major competitive cations and ra- pathways of 14C released from buried radio- dionuclides' Kdsitu values. The experimental active waste, in order to identify the critical work, partially carried out in the PEACE facilities pathways to plants and to determine the pa- at CEA in Cadarache, France, consists in charac- rameters for assessment models. terizing the water-retention properties of se-

Radioecology 17 lected European soils and determining KdSitu Table 1 Grasses selected in the REDUP programme. from soil and soil-solution analyses of samples from the lysimeter facilities. In these, different Species Type Cultivar plant species (bean, lettuce, spring barley) are Lolium perenne early diploid also cultivated. The relationship between soil Merbo water content and radionuclide and cation con- tetraploid Merlinda centration in soil solution and plant are used half-late diploid Merganda to characterize better and to model the radio- tetraploid Meradonna nuclide root uptake. late diploid Melvina tetraploid Tivoli 137 REDUP The REDUP (REDuction of Cs and Phleum pratense Erecta 90 Sr UPtake by grasses in natural meadows) Festuca pratensis Merifest programme aims at proposing technically and Dactylus glomeratus Lemba economically suitable countermeasures to be Poa pratensis Mervel applied at field scale in meadow ecosystems, Bromus inermis in order to decrease the mobility and transfer Trifolium pratense Violetta of radionuclides, mainly 137Cs and 90Sr. It also investigates the effect of the countermeasures applied on the mineral (macro- and micro- • We found no differences in dry weight pro- nutrients) status of the plants and, hence, their duction and TF between early, half-late, and nutritive value for cattle feeding. late cultivars of either diploid or tetraploid ryegrass (Lolium perenne), so we pooled the Investigations carried out after the accident data from the three cultivars. at the Chernobyl nuclear power plant have • We found no difference in dry weight pro- demonstrated that meadow ecosystems are duction and TF between diploid and tetra- one of the most important contributors to ploid ryegrass; because these species have both external and internal irradiation of peo- both the highest biomass production and a ple living on radioactively contaminated ter- rather low TF, they could represent an inter- ritories. This result stresses the need for esting solution to improve the meadows. the development of optimal restoration strategies on meadows. These are considered from a Poa and Phleum have the lowest TF, but also two viewpoints: the application of agricultural the lowest yield. practices and countermeasures at soil level, to change the soil-solution composition and • Bromus has a low yield and a rather high TF, soil adsorption-fixation properties, by fertil- so it is not a good choice. izing, liming, and adding other soil amend- • Despite high biomass production, clover ments (clays, zeolites, sapropel, etc.); and the (Trifolium) has a very high caesium incor- selection of forage plant species for investi- poration and, hence, is not recommended. gation, since transfer also depends on plant species. • Both Dactylus and Festuca have high yields, but also high contamination levels. The selected grasses included six different types of ryegrass cultivars, given their impor- RECOVER The RECOVER (RElevancy of COpse tance (Table 1). The soil (Orthic Podzol) is ho- VEgetation for the Remediation of contami- mogeneously contaminated with a 134CsCl so- nated sites) project aims at a radioecological lution. The vegetation is cut at about three and economical validation of Short-Rotation weeks, and dry weight, contamination levels, Coppice (SRC) for energy production as a real- and mineral status are determined. istic alternative for the remediation (rehabilita- tion) of radioactively contaminated farmland. Our preliminary conclusions, to be confirmed by future harvests and additional measure- To fulfil its overall objective, RECOVER elabo- ments on harvested material, are the following. rates in four domains:

18 Radiation Protection • radioecology: flux of radiocaesium and its (740Bq-kg l). This concentration is assumed chemical analogue, potassium, in the cop- to decrease in the course of each rotation, since pice ecosystem and during biomass com- the proportion of the nutrient-rich bark will bustion; decrease (transfer factors to bark about five times higher than to wood). Despite chemical m dosimetry: doses during the culture main- analogies, radiocaesium and potassium do not tenance, harvest, and combustion; behave likewise in a coppice ecosystem. Fur- • agrotechnology: comparison of SRC with ther evolution of radiocaesium flux in the cop- other crops for energy production at agro- pice ecosystem can thus not be deduced or pre- technical level, for both West- and East- dicted from information on potassium cycling. European conditions; Sites with coppice stands of different matu- • economics: cost-benefit analysis for SRC rity, established on different soil types after and other crops for energy production, in- the Chernobyl accident, are selected in Swe- cluding sensitivity and optimization analy- den to allow predictions of the radiocaesium sis with emphasis on NIS conditions. behaviour in the long term (25 years). For the sites analysed at present, the soil-to-wood TFs The above studies will identify different pa- ranged between 4 xlO"6 and 7xlO"4m2-kg"1 rameters affecting the application of the SRC (comparable to TF values found on the lysime- concept for site remediation. The ranking of ters). These preliminary data showed that the these parameters will, in turn, allow us to val- variability in TF was mainly due to differences idate this remediation option critically. Our in soil type and culture maturity, culture vari- role in this project (co-ordinated by SCK« CEN) ety playing only a minor role. More data will is predominantly related to the radioecologi- be collected to allow firm conclusions on the cal aspects and the economic evaluation (with effect of stand maturity (and clone) and soil the Energy Technology Support Unit from AEA characteristics on the TF. Technology as subcontractor). In spring 1997, experimental trials were es- In May 1996, we set up lysimeters with wil- tablished in Belarus on two soil types (sandy low on two soil types (sandy and loamy), con- and peaty, with about 1.5 and 5.7MBq-m~2 taminated with lOMBq-m"2 of 134Cs. Regular of 137Cs, respectively) with four willow clones. sampling of the different radiocaesium pools The first-year results showed no effect of va- during the first two growth seasons allowed riety on the TF, but the TF was significantly us to follow the radiocaesium and potassium higher on the peaty soil (2.5 x 10~3m2-kg~1) dynamics in the ecosystem. The soil compart- than on the sandy soil (6.1 x 10"4m2-kg"1), ment is the major radiocaesium reservoir. Af- resulting in wood radiocaesium concentrations ter two years, only 0.006% (loamy soil) and of 14 500 and SSSBq-kg"1, respectively, levels 0.034% (sandy soil) of the soil radiocaesium considerably above the exemption limit for fuel was incorporated in plant material. The five wood in Belarus. It is still too early to discuss times lower total radiocaesium uptake on the scientifically the radiocaesium soil-to-plant TF loamy soil was related with the higher reten- obtained for willow at the different sites. tion capacity and lower concentration in the soil solution of this soil. For both soils, the The last aspect considered in the evaluation ex- major radiocaesium fraction was incorporated ercise is the study of the energy balance and in the plant parts below the surface (roots and the economic cost-benefit analysis of SRC and cuttings). An important fraction of the radio- other crops for energy production for West- caesium (about 65%) recycled back to the soil European and Belarus conditions. For that rea- during litter fall in autumn and leached off son, data were and are still being collected as from leaves with rain. The lowest radiocaesium input for two subprojects: RECAP, designed to concentration was in the wood: after two grow- model the economics of SRC for production of x ing seasons, 19Bq-kg~ for the loamy soil and energy or heat, and CRISP, developed to model -1 615Bq-kg for the sandy soil, thus below the production of oilseed rape, sugar beet, and the exemption limit for fuel wood in Belarus wheat, and their conversion to liquid befouls.

Radioecology 19 Carbon 14 14C is present in a variety of ra- To investigate the first parameter, we used dioactive waste streams, including spent fuel, a sprinkler fed with NaH14CO3-contaminated spent ion-exchange resins, and reactor retub- water and collected the irrigation water at in- ing and decommissioning wastes. It has been creasing distances from the sprinkler (up to identified as a major fuel-cycle radionuclide, 15 m). The activity in the deposited water was one that contributes significantly to human ex- compared with the 14C content sampled from a posure over long timescales. The management loop located immediately before the sprinkler and disposal of 14C has become an impor- head. The results show that the fraction of ra- tant issue because of its potential inventory, dioactivity lost is proportional to the concen- rapid volatility (CO2, CH4, etc.), long half-life tration of the H2CO3 and dissolved CO2 forms, (5 730 years), and ease with which it is assimi- which, in turn, is ruled by the pH (Fig. 1). The lated into biological systems. Performance as- losses also increase with the outside tempera- sessment modelling for 14C from radioactive ture. Finally, the radiocarbon concentration in waste burial is, however, impaired by some the irrigation water tends to increase with the poorly documented contamination pathways. distance from the sprinkler (Fig. 2). Much of the modelling has evolved from analyses of atmospheric sources and is not appro- Activity released^ priate for underground sources such as buried : i . : ' i • • i :• • i : : • | . : . | : • . radioactive waste. Large uncertainties are as- 1 1 sociated with the contamination of plants by « 22-C • ** 14 C from soil (soil-root pathway), the contami- - nation via the soil-atmosphere-plant pathway, and the contribution of irrigation with 14C-contaminated water.

During the last two years, we investigated the mechanism of 14C uptake by the plant roots from the soil solution (see SCK-CEN's 1996

Scientific Report). We are now considering 1 the irrigation pathway using 14C-contaminated groundwater, which appears, according to assessments applying mean parameters, as a ma- 14 jor contributor to the total doses from C via Figure 1 The mean loss of radiocarbon fraction in ingestion of irrigated food crops and animal water deposited onto the soil is ruled by the pH. foodstuffs. We intend to quantify the contamination of vegetation by irrigation with surface or underground water contaminated by releases of 14C from radioactive repositories and to define the mechanisms by which 14C accu- mulates in plants.

The study focuses on the following parameters: direct loss of 14CC>2 from irrigation water to the atmosphere prior to contact of water with aerial plant parts or soil surfaces; uptake of 14C by plants from the contaminated water adhering on their aerial organs; behaviour of the 14C deposited on the soil surface (penetration into the soil and release to the atmosphere); and validation of the previous observations in a mixed scenario including depo- 14 sition of C-contaminated water on both the Figure 2 Effect of the distance from sprinkler on aerial plant organs and the soil surface. the residual radiocarbon activity in irrigation water.

20 Radiation Protection We tested the direct uptake by leaf surfaces of The effect of mixing different pure clay min- H14CO3 present in water by dipping the aerial erals was also investigated. Clay minerals parts of maize and pea into contaminated wa- were mixed in different proportions; illite/ver- ter. The 14C uptake is linear with time at rela- miculite (50/50), illite/vermiculite (70/30), il- tive rates of 0.47 and O.SOBq-min"1 per gram lite/biotite (50/50), and illite/biotite (30/70). of leaf dry matter for maize and pea, respec- The competition arising between the differ- tively, for a concentration of 1 Bq-ml"1 in wa- ent radiocaesium retention pools of the min- ter in contact with the leaves. erals was clear and, again, the results obtained with the model were coherent with the physicochemical properties of the minerals. WOODMODE With the technical assistance of IPEP, we collected tree samples in the Vetka To study the effect of an inert material on forest (Belarus) affected by the Chernobyl fall- the sorption and retention dynamics of radio- out. The sample collection allows us to eval- caesium by clay, we mixed an illite clay with uate the changes in radiocaesium distribution pure quartz in different proportions (1, 2, 4, in trees; in addition, we developed dendro- 8, 16, and 32%). Both sorption and desorption chemistry methods to establish a preliminary were clearly retarded. The model we had de- model of radiocaesium and radiostrontium ac- veloped failed to represent such a scenario and cumulation in the trunk. needs updating to take this kind of process into account. R&D programmes We studied the behaviour of radiocaesium in soil and, especially, its re- Finally, we further investigated the effect of tention by pure clay minerals. Dynamic sorp- pH on radiocaesium sorption-desorption pro- tion and desorption experiments were carried cesses. For illitic clay minerals, the acidity out under well-controlled conditions, provid- has a clear effect; we determined the compart- ing information about the sorption and reten- ments most affected by the protons. tion kinetics on the different sorption pools considered onto a 2:1 clay mineral. The experimental results were used to develop and improve a dynamic, mechanistic, simple multisite, multireaction, retention model for the 2:1 Scientific partners Atomic Energy Authority (AEA clay minerals (see "Waste Disposal," page 72). Technology) — Atomic Energy of Canada Ltd, Chalk River Laboratories (AECL) — Commissariat a l'energie The sorption and retention of traces of radio- atomique (CEA) — Imperial College — Institute of caesium were studied in 1996 on four different Power Engineering Problems (IPEP) — Katholieke clay materials characterized by different min- Universiteit Leuven (KUL) — McAulay Land Use Re- eralogical structures and properties: a smec- search Institute (MLURI) — Mouchel & Partners Ltd — tite (bentonite), two micas (illite and biotite), Polessky State RadloEcological Reservation (PSRER) — and a vermiculite containing mica-vermiculite Russian Institute for Agricultural Radiology (RIAR) — mixed layers. The experimental observations Research Institute of Radiology (RIR) — Rise National led us to assume the existence of at least three Laboratories — Swedish University of Agricultural kinds of sorption sites: the nonspecific, spe- Sciences (SLU) — University of Barcelona — Universite cific, and highly specific sites. In 1997, to catholique de Louvain (UCL) — Ukrainian Institute for complete this set of clay minerals, we inves- Agricultural Radiology (UIAR) — University of Lund tigated three beidellite ones: the first was artificial, the second extracted from real soil layer, Sponsors European Commission (EC), Radia- and the last extracted from a geological layer. tion Protection Research programme — Nationale The results obtained by combining sorption- Instelling voor Radioactief Afval en Verrijkte Splijt- desorption experiments and modelling were in stoffen/Organisme national des dechets radioactifs good agreement with the differences in min- et des matieres fissiles enrichies (NIRAS/ONDRAF) — eralogical structures (interlayer distances and Paul Scherrer Institute (PSI) layer charges) of the clays tested.

Radioecology 21 CM. VANDECASTEELE, P.J. COUGHTREY, R. KIRCH- MANN, "Environmental Consequences of the Cher- Books published in 1997 nobyl Accident," Proc. of the int. conf. Ten Years After The Chernobyl Catastrophe, Minsk, Byelorussia, Y. THIRY, M VAN HEES, S. DE BROUWER, C. M. VANDE- NIS, October 7-12, 1996, 110-125 (1997). CASTEELE, "Prospect of Alternatives in Agro-Chemical Site Restoration," in: C. Ronneau and 0. Bitchaeva, CM. VANDECASTEELE, P.J. COUGHTREY, R. KIRCH- eds., Biotechnology for Wastes Management and Site MANN, "Impact of the Chernobyl Accident on Restoration: Technological, Educational, Business, the Environment and Management of Contaminated Political Aspects 34, 213-219 (Kluwer Academic Areas," Ann. Ass. Beige Radioprot. 22:1, 59-81 (1997). publ., NATO ASI Series, 1997). CM. VANDECASTEELE, E. VALCKE, M. VAN HEES, C. M. VANDECASTEELE, O. BURTON, R. KIRCHMANN, H. VANDENHOVE, Y. THIRY, "Amendments as "Agricultural Remedial Actions: Ecological Bases and Agricultural Countermeasures," Proc. of the int. conf. Problems Associated with Their Implementation," Ten Years After The Chernobyl Catastrophe, Minsk, in: OECD-NEA, ed., Agricultural Aspects of Nuclear Byelorussia, NIS, October 7-12, 1996,139-146 (1997). and/or Radiological Emergency Situations, 97-111 H. VANDENHOVE, M. VAN HEES, C. BACQUOY, (1997). CM. VANDECASTEELE, "Usefulness of AFCF as a Countermeasure for Radiocaesium Transfer from Publications in 1997 Loamy Soil to Ryegrass and Clover," Sci. Tot. Environ. Y.A. IVANOV, N. LEWYCKYJ, S.E. LEVCHUK, 37:2, 193-200 (1997). B. S. PRISTER, S.K. FIRSAKOVA, N.P. ARKHIPOV, H. VANDENHOVE, M. VAN HEES, S. DE BROUWER, A.N. ARKHIPOV, S.V. KRUGLOV, R.M. ALEXAKHIN, CM. VANDECASTEELE, "Effect of Ammonium- J. SANDALLS, S. ASKBRANT, "Migration of 137Cs and Ferric(m)-Hexacyano-Ferrate(H) and Faeces Addition 90Sr from Chernobyl Fallout in Ukrainian, Belarussian on Yield and Soil-Plant Transfer of Radiocaesium to and Russian Soils," /. Environ. Radioactivity 35, 1-21 Ryegrass," Sci. Tot. Environ. 37:2, 235-246 (1997). (1997).

E. VALCKE, B. ENGELS, A. CREMERS, "The Use Presentations delivered in 1 997 of Zeolites in Radiocesium and Radiostrontium A. GOMMERS, H. VANDENHOVE, Y. THIRY, C. M. VAN- Contaminated Soils: A Soil-Chemical Approach. DECASTEELE, E. SMOLDERS, R. MERCKX, "Uptake and Part I: Cs/K Exchange in Clinoptilolite and Mordenite," Partitioning of Radiocaesium in a Short Rotation Zeolites 18, 205-211 (1997). Coppice Culture of Willows," 27th annual meeting of E. VALCKE, B. ENGELS, A. CREMERS, "The Use the European Society for New methods in Agricultural of Zeolites in Radiocesium and Radiostrontium research (ESNA), jointly organized with the Union Contaminated Soils: A Soil-Chemical Approach. Internationale de Radioecologie (UIR): Gent, Belgium, Part II: Sr/Ca Exchange in Clinoptilolite, Mordenite, August 29-September 2, 1997. Proc., 208-214. and Zeolite," Zeolites 18, 212-217 (1997). N. LEWYCKYJ, B. DELVAUX, "A Quantification of E. VALCKE, M. VIDAL, A. CREMERS, Y. IVANOV, the Time Dependent Retention of Caesium Traces G. PEREPELAYTNIKOV, "The Use of Zeolites in in Different Clay-Solution Systems," 27th annual Radiocesium and Radiostrontium Contaminated meeting of the European Society for New methods Soils: A Soil-Chemical Approach. Part III: A Soil- in Agricultural research (ESNA), jointly organized Chemical Test to Predict the Potential Effectiveness with the Union Internationale de Radioecologie (UIR): of Zeolite Amendments," Zeolites 18, 218-224 Gent, Belgium, August 29-September 2, 1997. Proc., (1997). 128-134.

E. VALCKE, A. ELSEN, A. CREMERS, "The Use of Zeolites Y. THIRY, B. DELVAUX, "Effects of Organic Acids on in Radiocesium and Radiostrontium Contaminated Radiocaesium Retention by Vermiculitic Minerals Soils: A Soil-Chemical Approach. Part IV: A Potted Soil of Micaceous Origin," 27th annual meeting of the Experiment to Verify Laboratory-Based Predictions," European Society for New methods in Agricultural Zeolites 18, 225-231 (1997). research (ESNA), jointly organized with the Union Internationale de Radioecologie (UIR): Gent, Belgium, August 29-September 2, 1997. Proc., 135-141.

22 Radiation Protection H. VANDENHOVE, M. VAN HEES, CM. VANDECAS- TEELE, "Efficacy of AFCF in Reducing the Soil-Plant Transfer of Recently Deposited or Aged 134Cs and Consideration of Possible Site Effects," 27th annual meeting of the European Society for New methods in Agricultural research (ESNA), jointly organized with the Union Internationale de Radioecologie (UIR): Gent, Belgium, August 29-September 2,1997..Proc, 196-202.

Theses published in 1997

J. DAMMEN, "Radiocesiumsorptie-desorptieprocessen op 2:l-type kleimineralen," final-year project, Chemistry (Katholieke Hogeschool Kempen, Geel), June 1997.

Y. THIRY, "Etude du cycle du radiocesium en ecosysteme forestier: distribution et facteurs de mobilite," PhD thesis, Agronomical Sciences and Bioengineering (Universite catholique de Louvain), June 1997.

D. TURBANG, "Modelisation de la retention du radiocesium par les mineraux argileux de type 2:1," final-year project, Industrial Engineering (Institut Superieur Industriel de Bruxelles), September 1997.

Lectures taught in 1997

C. M. VANDECASTEELE, "Countermeasures in Agri- cultural Ecosystems," ERPET training course: Mol, Belgium, June 23-27, 1997 and Ljubljana, Slovenia, September 29-October 3, 1997.

CM. VANDECASTEELE, "Countermeasures," UIR Summer School on Radioecology: Neptun, Romania, September 13-23, 1997.

CM. VANDECASTEELE, "Freshwater Radioecology," UIR Summer School on Radioecology: Neptun, Romania, September 13-23, 1997.

C. M. VANDECASTEELE, "Cours de Radioecologie," Universite Libre de Bruxelles and Universite de Liege. 160 pages.

C. M. VANDECASTEELE, "Risque nucleaire et agricul- ture," Triennal of the Federation des associations beiges d'ingenieurs (FABI): Liege, Belgium, October 1, 1997.

Radioecology 23 BE9900060

Theo ZEEVAERT, Hans VANMARCKE Environmental Restoration

Scientific staff NVIRONMENTAL RESTORATION shows im- of NIRAS/ONDRAF in the framework of our ra- Theo ZEEVAERT E portant needs and opportunities. In Bel- diological impact assessments for radioactive Hans VANMARCKE gium, these are primarily the need for restoring waste disposal or discharges, and are leading Lieve SWEECK radioactively contaminated sites and the need the working group on remediation assessment Mark Loos for assessing the radiological impact of waste in the second theme. Geert VOLCKAERT disposal or discharges. Participation in international programmes is necessary for keeping In nuclear site restoration, we are also co- Supporting staff in touch with important developments. ordinating the RESTRAT project in the fourth Freddy GEENEN EC Radiation Protection Research programme (DGXil) and carrying out the CARE study for Objectives DGXI (see "Radiological Assessment and Op- • to optimize and validate models for the im- timization," page 12). Related projects are pact assessment from environmental, ra- PEACE, REDUP, RECOVER, and WOODMODE (see dioactive contaminations, including waste "Radioecology," page 17). disposal or discharges; In the framework of policy support for radio- • to support the policy of national author- active waste management, we also study the ities for public health and radioactive waste radiation-protection aspects of land disposal management. at the request of NIRAS/ONDRAF and perform studies for other clients. Programme As a result of the operation from 1922 till 1969 of one of the world's largest radium extraction plants, radium has Achievements On behalf of the Federal been dispersed in Sint-Jozef-Olen and Geel (Bel- Government (DBIS/SPRI), SCK« CEN wrote a com- gium). An extensive radiological characteri- pilation of all relevant information, so that the zation programme identified several contam- competent authorities can decide on the nec- inated sites. The parties concerned agree in- essary licences to carry out the environmental creasingly in favour of a global restoration restoration in Sint-Jozef-Olen and Geel. The plan, not because of the current population ex- waste volumes to be removed depend on the posure but because most of the scenarios con- selected action levels (Table 1). cerning the future use of these areas show enhanced exposure of future generations. Our radiological assessment of five options to restore the dumping ground used as selection The site of Olen, around the Bankloop brook, criteria the cost of the restoration, the sur- is also the test scenario of BIOMASS (Biosphere face area of the new storage facility, the col- Modelling and Assessment methods), an IAEA lective dose of the intervention workers, and programme providing an international focal the individual dose for people who will be point in biospheric assessment modelling. The living above the storage facility after the pe- two major themes of BIOMASS are indeed ra- riod of institutional control. The best solu- dioactive waste disposal and environmental re- tion turned out to be displacing the waste to leases, the latter further divided into dose re- a nearby place (with the radioactive waste un- construction and remediation assessment. We der the chemical one) and applying a multi- are participating in the first theme on behalf layer cover. The cost for the global restoration plan is estimated at 370MBEF, of which Table 1 Summary 81% for restoring the dumping ground and con- of the proposed action Contaminated Action level Waste structing the storage facility, 17% for cleaning site (y dose rate, tiSv/h) [103m3] levels and the result- up the river, and 1% each for the streets and for ing (rounded) waste Dumping ground 0.2 125 the dwelling and building ground. The munici- volumes. The dump- River 0.15 10 pal authorities of Olen decided to clean up the ing ground can have (Farmland not considered 30) Kapellekensstraat in 1998 and to discharge ra- 0.4uSv/h if dug deeper Streets 0.2 1 dioactively contaminated soil onto the dump- than one metre and then ing grounds. This cleanup work will be moni- Total 136 covered with clean soil. tored by SCK« CEN.

24 Radiation Protection In BIOMASS, Theme 1 Radioactive waste disposal, we participate in three working groups, reporting on principles for defining hypotheti- Scientific partners Atomic Energy Author- cal groups (a continuation of the work on refer- ity (AEA Technology) — Electric Power Research ence biospheres in the BIOMOVSII study), prin- Institute (EPRI) — Institut de protection et de surete ciples for applying data to assessment mod- nucleaire (CEA-IPSN) — Studsvik Eco&Safety — els, and model developments. Reports for the Paul Scherrer Institute (PSI) — Swedish Radiation first two working groups are being drafted and Protection Institute (SSI) — National Radiological will be finalized in 1998. The third one will Protection Board (NRPB) — Mouchel & Partners start only after the first two complete their Ltd — National Institute of Public Health and Envi- work. ronmental Protection (RIVM) — Central Laboratory for Radiological Protection (CLRP) — University of In BIOMASS, Theme 2 Environmental releases, Veszprem — Nuclear Research Institute (NRI) — the working group we are leading is following Scientific Production Association Typhoon (SPA two approaches. The first assesses the influ- Typhoon) — Senes Oak Ridge Inc. (SENES) — Centro ence of a remedial action carried out in the de Investigaciones Energeticas, Medioambientales y past (deep ploughing) with respect to the 226Ra Tecnologicas (CIEMAT) — Empresa Nacional de Resid- contamination of cow milk and compares the uos Radioactivos SA (ENRESA) — Technical Research modelling results with measured values. The Centre of Finland (VTT) — Gesellschaft fur Strahlen- predicted 226Ra concentrations in milk were und Umweltforschung (GSF) shown to be generally higher than the observed concentrations, either because the modellers and other participating institutes in BIOMASS underestimated the effect of deep ploughing or because the measures of soil contamina- Customers Nationale Installing voor Radioactief tion before deep ploughing are little represen- Afval en Verrijkte Splijtstoffen/Organisrae national tative. We will take new cores at the Bankloop des dechets radioactifs et des matieres fissiles in Olen. The second approach assesses the ef- enrichies (NIRAS/ONDRAF) — Dienst voor Bescherming fectiveness of potential remedial actions and tegen Ioniserende Stralingen/Service de protection compares the modelling results to each other. contre les radiations ionisantes (DBIS/SPRI) We drafted a detailed scenario for two remedial actions: the removal of the soil at the most contaminated areas and the capping of the contaminated soil with a clean clayey soil layer. Presentations delivered in 1997

Th. ZEEVAERT, M. LOOS, H. VANMARCKE, L. SWEECK, In BIOMASS, Theme 3 Biosphere processes, we "Initial Case in Remediation Assessment. Case RAOl: participate in the working group on Fruit Tree Olen, Radium Extraction Site," BIOMASS meeting, En- Modelling. The first efforts were devoted to vironmental Releases: Mol, Belgium, June 9-13, 1997. collecting and reviewing information needed to assess the importance of fruit in the food Th. ZEEVAERT, L. SWEECK, H. VANMARCKE, P. DE- chain. BOODT, "Etude d'impact d'une decharge industrielle contaminee en radium 226," Journees sur la gestion des dechets de tres faible activite: enjeux et impacts The biosphere parameter literature review car- (SFRP-ABR): Lille, France, November 13-14, 1997. ried out in 1991 for the performance assessments of near-surface disposal of LLW (on be- Reports published in 1 997 half of NIRAS/ONDRAF) is being updated and extended for use in performance assessments of H. VANMARCKE, "Sanering van de omgevingsbesmet- deep geological disposal of HLW. The literature ting met radium-226 te Olen en Geel," DBIS/SPRI con- review of biosphere parameters in the frame- tract KNT9096808, final report (June 1997). R-3179. work of performance and safety assessments of deep geological waste disposal will be final- H. VANMARCKE, "Evaluatie van de stralingsbelasting ized in early 1998 and used in the SAFIR 2 re- van de stortplaats Canivet te Haasrode," VITO contract port. KNT90 96876, final report (July 1997).

Environmental Restoration 25 BE9900061

Lucile MAHIEU Health Effects

Scientific staff T) ADIATION EPIDEMIOLOGY and radiation bi- a to document the feasibility of retrospective Sarah BAATOUT -t\. ology are two key areas that must interact cohort studies in Belgium; Louis DE SAINT-GEORGES to allow an understanding of the effects of low a to participate in the IARC study. Hilde ENGELS doses of radiation. LUC HOLMSTOCK For radiobiology, we intend Paul JACQUET A retrospective epidemiological study (1953- Lucile MAHIEU 1994), in progress at SCK-CEN, includes five • to elucidate the mechanisms of the effects Hubert REYNERS Belgian nuclear facilities: SCK>CEN, Belgonu- of ionizing radiation on the mammalian em- Eric VAN MIEGHEM cleaire, Belgoprocess, and the power plants of bryo during the early phases of its develop- Elva GlANFELICI DE Doel and Tihange. This work will be part of ment; REYNERS an international multicentre programme, co- • to assess the genetic risks of maternal ex- (guest scientist) ordinated by the International Agency for Re- posure to ionizing radiation; Jiekun YAN search on Cancer (IARC/WHO, Dr E. Cardis) in (guest scientist) Lyon and combining data on radiation work- • to elucidate the mechanisms by which dam- Jean VANKERKOM ers from 14 countries. Such a large-scale study age to the brain and mental retardation are (VITO, part time) aims at estimating the cancer risk of prolonged caused in man after prenatal irradiation. exposure to low doses of ionizing radiation. Supporting staff In addition, the Health Effects study group has Arlette MICHAUX By its multidisciplinary approach, radiobiol- • to keep abreast of new advances that are po- Jasmine BUSET ogy provides the indispensable scientific back- tentially relevant for SCK- CEN with regard to Werner SCHOONJANS ground for radiation protection, radiotherapy, the medical applications of ionizing radia- Christophe VERDONCK and nuclear medicine, and thereby contributes, tion and radionuclides; Ingrid VAN in a crucial manner, to public health. With REGENMORTEL regard to radiation protection, radiobiological • to advise authorities and to provide the gen- research aims at improving the evaluation of eral population with adequate information the potential risks of low doses delivered at concerning the health risks arising from ra- low dose rates by exploring the mechanisms diation exposure. of action of ionizing radiation at the molecular and cellular levels and the consequences on the organism. Several crucial problems re- Cancer risk among nuclear workers in Bel- main to be solved, in particular those related to gium In 1997, we further completed the radiation-induced developmental defects and data collection and control in the five partic- genetic damage in the child in utero and soon ipating facilities. We also strived to obtain, for after birth. Our research programmes focus scientific purposes, a direct access to the Na- primarily on the radiosensitivity of the devel- tional Population Registry, in order to allow fu- oping mammalian organism and are supported ture follow-up (cancer mortality) of the study by the Nuclear Fission Safety programme of the cohort: we started the procedure and had the EC and by the Belgian Federal Services for Sci- Ministry of Science approve the scientific im- entific Policy. portance of the study.

Our activities, carried out in close collaboration Moreover, the participation of the Belgian nu- with the Belgian and European scientific com- clear workers study in a concerted action munity, are essential for maintaining at SCK- "Studies of Cancer Risk among Radiation Work- CEN the scientific know-how needed to provide ers in the Nuclear Industry," in collaboration national and European authorities with advice with the IARC and four European countries (Bel- concerning potential hazards from exposure to gium, France, Germany, and the United King- ionizing radiation in normal and accidental sit- dom), was approved by the EC Nuclear Fission uations. and Safety programme.

In 1998, we will analyse the data of the nuclear Objectives For epidemiology, we intend workers study and write the final report, in col- • to study cancer mortality and morbidity in laboration with UCL (Prof. A. Wambersie). We nuclear workers in Belgium; will also update the cancer mortality study on

26 Radiation Protection populations living in the Mol-Dessel region and rest whose duration was proportional to the initiate the follow-up (cancer mortality) study dose delivered. After a dose of 2.5 Gy, the ef- of the nuclear workers cohort. fects of radiation were even more pronounced than those obtained in BALB/C embryos, in that almost no recovery occurred in irradiated em- Mechanisms of the effects of ionizing ra- bryos. At a dose of 1 Gy, however, the G2 arrest diation on the mammalian embryo Expo- was much less, and all embryos were able to sure to ionizing radiation can induce a delay in undergo a mitosis after a corresponding delay. the cell cycle, either before DNA synthesis (Gl arrest) or after DNA synthesis (G2 arrest). The The modifications of MPF activity during G2 ar- G2 arrest delays cells from entering division, rest were studied in embryos of the Heiligen- thereby, presumably, allowing time to repair berger strain, using the "histone Hi kinase as- DNA damage. Recently, the molecular mecha- say" developed last year for BALB/c oocytes and nisms of cell-cycle control in eucaryotic organ- embryos. In this test, MPF activity is evaluated isms have been partially elucidated, shedding on the basis of its capacity to phosphorylate new insights into the mechanisms of radiation- the histone Hi protein. Histone Hi kinase ac- induced G2 arrest. Research in this area at tivity of irradiated Heiligenberger embryos re- SCK'CEN is integrated into a co-operative EC mained at a very low level during G2 arrest, programme with five European institutes. Our while this level was slightly, though not sig- laboratory contributes to this project by study- nificantly lower than that of the controls during, in mouse preimplantation embryos, vari- ing delayed mitosis. Results obtained last year ous factors involved in the cell-cycle control. with BALB/c embryos suggested that a relation- In 1997, we pursued investigations on Matura- ship could exist between the levels of histone tion Promoting Factor (MPF), a protein complex Hi kinase activity in mitosis and the health sta- whose activity determines the passage from tus of the embryo: levels of activity lower than the G2 stage to mitosis. In the context of normal would be indicative of some remaining the other studies carried out in the EC con- damage incompatible with the embryonic sur- tract, an understanding of radiation effects on vival; the lower the level of activity, the quicker this factor in the early embryo promises new the embryos would die after division. The ex- insights, not only on how radiation damage act link between these two parameters remains could be transmitted to later embryonic, foetal, to be denned for the Heiligenberger strain. and postnatal stages of development but, more generally, on how radiation-induced changes in Preliminary results have also been obtained on the feedback control of the cell cycle affect the the levels of histone HI kinase activity in BALB/C evolution from the initial DNA damage to per- embryos irradiated at the two-cell stage. These manent cellular modifications. studies will be completed in 1998, and similar investigations will be performed in Heili- One-cell embryos of the BALB/c strain exhibit genberger embryos. In addition, we intend to a peculiar sensitivity towards the radiation- extend the comparison of histone Hi kinase ac- induced G2 arrest. Thus, in contrast to most tivities to one-cell and two-cell embryos from a other cells, the proportion of blocked em- third strain, chosen on the basis of a very low bryos, and not the duration of the block, in- sensitivity to the radiation-induced G2 arrest. creases with the dose of radiation. Even after a dose as high as 2.5 Gy, some embryos are The activity of the cdc2 subunit of MPF changes still able to escape completely the drastic G2 ar- throughout the cell cycle and these changes of rest and to divide in time. In 1997, studies on activity are accompanied by modifications in the radiation-induced G2 arrest and its mech- the state of phosphorylation of the subunit. anisms were extended to one-cell embryos of Immunoblotting is the method of choice to the Heiligenberger strain, in collaboration with study such changes in early embryos. It is cur- our EC contract partners from Essen. Heiligen- rently being used to study the state of phos- berger embryos reacted to irradiation in a more phorylation of the protein present in lysates of "classical" way than BALB/c embryos, in that control oocytes and embryos. The next step, nearly all irradiated embryos suffered a G2 ar- planned for 1998, will be to investigate the

Health Effects 27 changes in the state of phosphorylation of cdc2 aberrations. For each individual group, at in function of the state of G2 arrest in the first least 100 oocytes are analysed. The results embryonic cell cycle from sensitive (BALB/C and obtained in 1997 suggest that the sensitivity Heiligenberger) and nonsensitive (CFl or C57 of the guinea-pig oocyte to the induction of black) strains. This work will be done in collab- translocations and other chromosome aberra- oration with our EC contract partners of Munich tions diminishes as the time interval separating and Essen. them from ovulation increases, i.e., when less and less mature oocytes are irradiated. This is The G2 arrest is considered as an active re- particularly evident when one considers the response of the cell to irradiation, allowing time sults obtained with the highest dose of X-rays to repair DNA damage before division. In 1998, (one week before ovulation: 20% of oocytes DNA repair will be studied in irradiated one- with translocation(s); two weeks before: 12%; cell embryos undergoing a G2 arrest, using the three weeks: 8%). However, this has still to be "comet assay" (which measures DNA repair at confirmed for the following time intervals (4, the biochemical level) and the techniques of 8, and 15 weeks before ovulation), for which "Premature Chromosome Condensation" (PCC, only partial results are available at present. which measure DNA repair at the chromosome Oocytes irradiated two days before ovulation level). These studies will be performed in col- showed the highest sensitivity, with about 35% laboration with our contract partners at Essen of cells with one or more translocations after and Athens, respectively. a dose of 1 Gy. In experiments undertaken in 1996 and completed this year, we found that all youngs originating from guinea-pig females Genetic risks of maternal exposure to ion- irradiated with 1 Gy two days before ovulation izing radiation Developmental abnormali- were morphologically normal and did not show ties such as malformations or dwarfism could any translocations in their germ cells. This arise as a result of various types of chromo- suggests that either all oocytes carrying chro- some aberrations induced by radiation in fe- mosome aberrations are eliminated before fer- male germ cells and then transmitted to the tilization, or that the embryos resulting from embryo. The genetic radiosensitivity of the the fertilization of such oocytes are selectively different stages of female germ cells and the eliminated before birth. role of chromosome aberrations in the aetiol- ogy of developmental anomalies remain, how- Data on the induction of chromosome aber- ever, poorly defined due to the lack of a suit- rations in the guinea-pig oocyte at different able animal model. We could demonstrate in stages of growth and maturation will be com- our laboratory that the structure and sensitiv- pleted in 1998, so that a precise dose-effect ity of guinea-pig female germ cells correspond relationship is obtained for the various stages much better to those of the human female tested, from the immature stage up to the pre- than those of the mouse used previously. Our ovulatory one. Our results, together with those studies on radiation-induced translocations in obtained in the progeny of irradiated females, parental oocytes and in the guinea pig embryo will provide a better basis for the estimation of aim at providing a better estimate of the ge- the genetic risks in irradiated women. netic risks in irradiated women.

Our investigations on the sensitivity of the Effects of ionizing radiation on the central guinea-pig oocyte to the induction of trans- nervous system Low doses of ionizing ra- missible chromosome aberrations by radiation diation can induce mental retardation in chil- were pursued. Oocytes are X-irradiated by 1, 2, dren, particularly when radiations have been or 4 Gy at different stages of follicular growth delivered between weeks 8 and 15 of prena- (0, 1, 2, 3, 4, 8, or 15 weeks before ovulation). tal life. To elucidate the mechanisms and the Two days before ovulation, they are collected, risks of this effect, the EC is supporting the ef- cultured in vitro to the MI stage (the metaphase forts of SCK»CEN to co-ordinate the works of of the first meiotic division), fixed, and anal- eight other European radiobiological laborato- ysed for translocations and other chromosome ries also involved in this area, dealing in par-

28 Radiation Protection ticular with the extent of damages and repair tion but, at that time, all apoptotic cells had al- in the brain DNA, the mapping of radiosensitive ready disappeared. Finally, the p53 antigen (a cerebral areas, the up- and down-regulation of marker of the integrity of the DNA) was found a series of genes or gene products, and the ben- to be up-regulated in many apoptotic bodies eficial effects of the addition of growth factors four hours after irradiation but, here too, the in vitro. It has been shown that brain produces dose required was high: 400 mGy of X-rays. during its development a considerable amount of superfluous or redundant nerve cells which One of two future objectives aims at linking die naturally (by apoptosis) and are eliminated; function with structure target. The quantita- the reasons for such a waste of cellular mate- tive evaluation of the density of the electro- rial are still unclear, but the newly produced chemical connections between nerve cells (the brain cells apparently compete for establishing synapses) has now been developed for the hip- cellular contacts or connections between each pocampus of the rat; the present method is other and only those dividing more rapidly sur- based on a quantitative automatic image analy- vive this struggle. The outcome is controlled sis of a specific deposit of gold microparticles by a series of growth factors. In the future, on the synapses. However, the exact time of the understanding of the signalling pathways maximum radiosensitivity for this parameter is involving these growth factors and their recep- still unknown. Such an information is required tors should pave the way to a possible compen- for correlating synaptic losses with the mem- sation for the cell losses caused by a prenatal ory failures observed in the functional and be- irradiation. Testing this hypothesis in the ro- havioural tests carried out at the NRPB. dent brain could also help reach a better understanding of the laws that rule the complex The other objective regards the control of nat- development of the human brain. ural and radiation-induced cell death (apoptosis). This two-step study will involve a map- Recent advances were registered along four ping of the regions where apoptotic cells are lines of investigation; they confirm the great seen during normal brain development, and variability in radiosensitivity of the develop- an assessment of the time schedule for such ing brain according to the morphological area events. This knowledge is requested for the studied, the time at observation, and the end- future projects which will aim at stopping or point investigated. First, we noted that the at- reducing cell death in the irradiated brain in or- rophy of the cingulum (the most radiosensi- der to compensate for cell losses due to radia- tive area of the rat brain) induced by a prenatal tion death: a regenerative attempt based on the irradiation increased markedly after birth, be- specific brain capabilities for neuron overpro- tween the ages of one and three months, after duction and the natural elimination of redun- dose levels as low as 200 mGy. The mechanism dant cells during the prenatal development. for this late consequence of the irradiation remains unknown but, as we found out, the origin of this atrophy is to be searched for out- Medical applications of ionizing radiation side the cingulum, most probably in the cere- and radionuclides Contacts of a general bral cortex. Second, in the hippocampus of nature with specialists in nuclear medicine and the adult rat, the density of the synapses (la- radiotherapy may be useful to advise the man- belled by synaptophysin) was found to have de- agement on new developments and potential creased after a prenatal irradiation at day 17 opportunities for SCK'CEN. On the other hand, of the pregnancy (El 7) but, here, the dose re- uncertainties remain about the radiobiological quired is very high: 800 mGy of X-rays. Third, foundation and consequences of techniques the strong expression of a cell proliferation using X- or y-rays and radionuclides for med- marker, the PCNA antigen, was down-regulated ical diagnosis and treatment. A study related to zero four hours after an El 5 or El 7 prenatal to the mechanisms of radiation-induced fibro- irradiation, except in the dying apoptotic cells. sis was initiated in 1995, as part of the long- Such apoptosis was often detected even after standing scientific collaboration with the radio- doses as low as 100 mGy of X-rays. PCNA la- therapy department of ULg. Our study aims at belling reappeared 24 hours after the irradia- establishing whether determination of circulat-

Health Effects 29 ing Transforming Growth Factor y (TGF-y) lev- part of the programme will be limited to the els before, during, and after treatment of pa- determination of TGF-y in the blood plasma of tients for lung cancer may be helpful to predict irradiated animals. patients at risk for the development of pneu- monitis and late normal-tissue injury.

The effectiveness of human cancer treatment is usually limited by the tolerance of normal tis- Scientific partners Institut fur Strahlenhygiene, sues to high doses of radio- or chemotherapy. Bundesamt fur Strahlenschutz — National Centre TGF-y is a key cytokine involved in the cascade for Scientific Research Democritos — Universitat- of events that leads to radiation-induced fibro- sklinikum Essen — Paul Scherrer Institute (PSI) — sis. Recent studies suggest that fibrogenesis University of Aachen — University of Athens — is mediated by the local production of TGF-y University of Barcelona — University of Freiburg — in normal tissue, but is also increased by TGF- University of Krakow — University of Uppsala — Com- y produced by the tumor and released in the missariat a l'energie atomique (CEA) — International circulation: TGF-y has been shown to function Agency for Research on Cancer (IARC) — National Ra- in an autocrine and a paracrine manner, but it diological Protection Board (NRPB) — Institut national may also have endocrine effects. The results de la sante et de la recherche medicale (INSERM) — of a pilot study clearly indicated that the evo- Deutsches Krebsforschungszentrum (DKFZ) — Uni- lution of serum TGF-y paralleled the platelet versite catholique de Louvain (UCL) — Universite de counts, due to the large amount of TGF-y in the Liege (ULg) y-granules of platelets.

Sponsors European Commission (EC), DGXII — In 1997, methods for drawing blood and pre- Federale Diensten voor Wetenschappelijke, Tech- paring plasma were specially designed to minimize platelet degranulation, using different nische en Culturele Aangelegenheden/Services anticoagulants; the y-ThromboGlobulin (y-TG), federaux des affaires scientifiques, techniques et a sensitive y-granule marker, was measured culturelles (DWTC/SSTC) in parallel in each plasma sample by a quantitative Enzyme-Linked ImmunoSorbent Assay (ELISA) technique. Plasma was collected by different operators in a large series (over 50) of voluntary blood donors; the values of TGF-y, Books published in 1997 using EthyleneDiamineTetraAcetate (EDTA) as S. BAATOUT, "Isolation of Megakaryocytes Using anticoagulant, were highly dependent on the Magnetic Cell Separation," in: U. Hafeli ef al., eds. dexterity of the technician; much better results Scientific and clinical applications of magnetic were obtained by using a complex Platelet In- carriers, 261-268 (Plenum Press, New York, 1997). hibitor Mixture (PIM). Moreover, the y-TG levels were about 10 times higher in the EDTA than H. ENGELS, A. WAMBERSIE, "Neutron RBE for Cancer in the PIM plasma, confirming a significant con- Induction and Other Late Effects: A Review of tamination by degranulated platelets in the for- Radiobiological Data," Chapter 3 in: Recent Advances mer samples. in Cancer Management. Recent Results in Cancer Research (Springer-Verlag, Heidelberg, 1997). In 1998, the methodology will be applied to pri- Publications in 1997 mary lung-cancer patients, before and during treatment, but also to patients suffering from S. BAATOUT, "Endothelial Differentiation Using miscellaneous pulmonary diseases, in order to Matrigel," Anticancer Research 17, 451-456 (1997). assess whether the plasma TGF-y level may be S. BAATOUT, "Thrombopoietin: A Review," Haemosta- considered as a prognostic indicator or as a sis 27, 1-8 (1997). marker of therapeutic efficacy or side effects. Experiments using rats, irradiated at the Radio- S. BAATOUT, "Meeting report of the annual meeting therapy Unit of ULg, will be carried out in paral- of the American Association for Cancer Research," lel. The contribution of our laboratory to this Gene Therapy 5, 5-7 (1998).

30 Radiation Protection S. BAATOUT, N. CHETA, "Useful Tools to Study S. BAATOUT, P. JACQUET, "Protein Kinase Activity of Endothelial Differentiation," Rom. J. Intern. Med. 34, the Cyclin/Cdkl Complex in Relation to the State 263-269 (1996). of G2-Arrest in One-Cell Embryos," Seminar of EU contractants for the project "Evolution of Genetic S. BAATOUT, N. CHETA, "Permeafix™: A Useful Tool Damage in Relation to Cell Cycle Control: Molecular to Detect Antigens and DNA in Flow Cytometry," Rom. Analysis Mechanisms Relevant for Low Dose Effects": J. Intern. Med. 35, 133-135 (1997). Munich, Germany, February 3-4, 1997.

S. BAATOUT, P. JACQUET, L. DE SAINT-GEORGES, S. BAATOUT, P. JACQUET, "Changes in Cyclin/Cdk L. BAUGNET-MAHIEU, "Le cycle cellulaire chez les Complexes after Radiation in Preimplantation Mouse mammiferes," Louvain Medical 116, 144-161 (1997). Embryos," Seminar of EU contractants for the project S. BAATOUT, P. JACQUET, L. DE SAINT-GEORGES, "Evolution of Genetic Damage in Relation to Cell L. BAUGNET-MAHIEU, "Le controle du cycle cellulaire Cycle Control: Molecular Analysis Mechanisms dans les cellules de mammiferes," Reme des Relevant for Low Dose Effects": Essen, Germany, Questions Scientifiques 168, 49-59 (1997). December 15-16, 1997.

L. DE SAINT-GEORGES, P. JACQUET, J. VANKERKOM, S. BAATOUT, P. JACQUET, T. JUNG, A. MICHAUX, S. BAATOUT, J. BUSET, L. BAUGNET-MAHIEU, "Con- J. BUSET, L. DE SAINT-GEORGES, L. BAUGNET-MAHIEU, genital Anomalies in the Offspring of Low Dose "One Dimensional Gel Electrophoresis Analysis of X-Irradiated Mouse," Radioprotection-Colloques the Histone HI Kinase Activity in Single One-Cell 32:C1, 424 (1997). Embryos after X-trradiation," Electrophorese Forum '97 organized by the French, Swiss, and German P. JACQUET, L. DE SAINT-GEORGES, J. BUSET, Societies of Electrophoresis: Strasbourg, France, S. BAATOUT, J. VANKERKOM, L. BAUGNET-MAHIEU, November 25-27,1997. Book of abstracts, 29. "Cytogenetic Effects of X-Rays in the Guinea Pig Female Germ Cells. I. The Immature Oocyte," S. BAATOUT, P. JACQUET, A. MICHAUX, J. BUSET, Mutation Research 391, 189-192 (1997). C. VANDECASTEELE, L. DE SAINT-GEORGES, L. BAUGNET-MAHIEU, "Histone HI Kinase Activ- P. JACQUET, L. DE SAINT-GEORGES, J. BUSET, ity in One-Cell Mouse Embryos Blocked in the S. BAATOUT, J. VANKERKOM, L. BAUGNET-MAHIEU, G2-Phase by X-Irradiation," Annual meeting of the "Cytogenetic Effects of X-Rays in the Guinea Pig American Association for Cancer Research: San Female Germ Cells. II. The Maturing Oocyte," Diego, California, USA, April 12-16, 1997. Proc. 38, Mutation Research 391, 193-199 (1997). 18. P. JACQUET, L. DE SAINT-GEORGES, J. BUSET, N. BARTHELEMY, L. BAUGNET-MAHIEU, P. BARTSCH, S. BAATOUT, L. BAUGNET-MAHIEU, "The G2-Arrest in J.-L. DAVID, F. HERION, A. MICHAUX, A.-M. MASSAR, the BALB/C Embryo: Relationship with Transcription," J.-M. DENEUFBOURG, "Transforming Growth Factor y, Radioprotection-Colloques 32:C1, 179 (1997). a Predictor of Fibrosis in Lung Cancer Patients H. REYNERS, E. GIANFELICI DE REYNERS, Treated by Radiation and/or Chemotherapy?," 28th F. STYLIANOPOULOU, "Does a Continuous Prena- annual meeting of the European Radiation Research tal Irradiation Specifically Increase the Incidence of programme: Oxford, United Kingdom, September Brain Tumours in the Adult Rat?," Radioprotection- 24-26, 1997. Book of abstracts, 167. Colloques 32:C1, 291 (1997). N. BARTHELEMY, L. BAUGNET-MAHIEU, L. BOSQUEE, P. BARTSCH, J.-M. DENEUFBOURG, "Pulmonary Presentations delivered in 1997 Function in Patients with Lung Cancer Treated by S. BAATOUT, "Effects of Radiation on Cell Cycle Radiation and Chemotherapy," Seventh int. congress Regulation in the Early Mammalian Embryo," Topical on Anti-cancer Treatment: Paris, France, February day on the Biological Effects of Radiation: SCK- CEN, 3-7, 1997. Book of abstracts, 228. Mol, Belgium, May 15, 1997. Book of abstracts, A. BENEKOU, E. BOZAS, B. POULAKI, 10-11. F. STYLIANOPOULOU, H. REYNERS, "Molecular S. BAATOUT, "Radiation Effects on the Cell Cycle Changes Induced in the Developing Rat Brain by In Regulation in the Early Mammalian Embryo," Seminar Utero Irradiation," 17th European winter conf. on at the Universite de Liege: Liege, Belgium, June 6, Brain Research: Bourg-Saint-Maurice, France, March 1997. 8-15, 1997. Book of abstracts, 66.

Health Effects 31 A. BENEKOU, H. PHILIPPIDIS, F. STYLIANOPOULOU, H. REYNERS, "Prenatal Brain Radiobiology," EC con- E. GIANFELICI DE REYNERS, H. REYNERS, "In Utero tractor meeting, contract FI4P-CT95-0008: Brussels, Irradiation Induced Changes in IGF Gene Expression Belgium, April 18-19, 1997. in the Rat Brain," 20th summer school for Brain H. REYNERS, "Efficiency of Low Dose Rates of Foetal Research. Degeneration and Regeneration: Amster- Irradiation to Induce Brain Atrophy and DNA Repair dam, the Netherlands, August 25-29, 1997. Book of Mechanism," 28th annual meeting of the European abstracts, 29. Radiation Research: Oxford, United Kingdom, E. BOZAS, A. BENEKOU, F. STYLIANOPOULOU, E. GIAN- September 24-26, 1997. Book of abstracts, 37. FELICI DE REYNERS, H. REYNERS, "Apoptose and p53 H. REYNERS, "In Utero Irradiation of the Foetal Gene Expression in the Developing Rat Brain after Rodent Brain: Early Effects," EC Steering Committee In Utero Irradiation," 13th annual meeting of the and Joint Association between the Gesellschaft Hellenic Society for Neuroscience: Athens, Greece, fur Strahlen und Umweltforschung (GSF) and the December 11-14, 1997. Book of abstracts, 46. National Radiological Protection Board (NRPB): L. DE SAINT-GEORGES, "Ionizing Radiation: A Major Brussels, Belgium, October 14-15, 1997. Concern for the Developing Brain," 17th European H. REYNERS, E. GIANFELICI DE REYNERS, J. YAN, winter conf. on Brain Research: Bourg-Saint-Maurice, H. COFFIGNY, "Prenatal Brain Irradiation: Effects of France, March 8-15,1997. Book of abstracts, 104. Acute Compared to Continuous Exposures," 17th H. ENGELS, "Epidemiological Factors for Hadron European winter conf. on Brain Research: Bourg- Therapy in the Western European Countries," Annual Saint-Maurice, France, March 8-15, 1997. Book of meeting of the European Hadron Therapy Group abstracts, 54. (EHTG'97): Innsbruck, Austria, October 8-11, 1997. H. REYNERS, E. GIANFELICI DE REYNERS, J. YAN, H. ENGELS, "Risk Assessment for Cancer Induction J. VANKERKOM, "Brain Cancer Incidence after after Low- and High-LET Therapeutic Irradiation," Prenatal Irradiation of the Rat," 17th European Annual meeting of the European Hadron Therapy winter conf. on Brain Research: Bourg-Saint-Maurice, Group (EHTG'97): Innsbruck, Austria, October 8-11, France, March 8-15, 1997. Book of abstracts, 55. 1997. Reports published in 1 997 P. JACQUET, "Effects of Radiation on the Developing Organism," Topical day on the Biological Effects of S. BAATOUT, P. JACQUET, "Topical Day on the Radiation: SCK-CEN, Mol, Belgium, May 15, 1997. Biological Effects of Radiation," SCK-CEN report (May Book of abstracts, 5. 1997). BLG-739.

P. JACQUET, L. DE SAINT-GEORGES, J. BUSET, P. JACQUET, "Etude de la sensibilite des cellules S. BAATOUT, L. BAUGNET-MAHIEU, "Checkpoint germinales femelles a l'irradiation par les rayons X, Controls for DNA Damage in Oocytes and Early Em- avec une attention particuliere pour les aberrations bryos," Workshop of the European Molecular Biology chromosomiques pouvant conduire a des anomalies Organization (EMBO): Cuenca, Spain, September 4-7, congenitales dans la descendance," SSTC contract 1997. Book of abstracts, 38. KNT9095693, annual report (March 1997).

H. REYNERS, "Protracting Radiation Injury: Putting H. REYNERS, H. COFFIGNY, I. FERRER, R. FERRER, Prenatal Neurons under the Question," EC contractor C. JANECZKO, "Effects of Protracted Exposures meeting, contract FI4P-CT95-0008: Freiburg, Germany, to Low Doses of Radiations during the Prenatal January 30-31, 1997. Development of the Central Nervous System," Nuclear Fission Safety (1992-1994). EC contract H. REYNERS, "The Development the Prenatal Brain FI3P-CT92-OO15, final report 2, 2763-2803 (1997). and Its Extreme Radiosensitivity," 17th European EUR 16769 DE/EN/FR. winter conf. on Brain Research: Bourg-Saint-Maurice, France, March 8-15, 1997. Book of abstracts, 21. H. REYNERS, E. GIANFELICI DE REYNERS, J. YAN, H. COFFIGNY, "Prenatal Brain Irradiation: Effects H. REYNERS, "In Utero Irradiation of the Foetal Rodent of Acute Compared to Continuous Exposures," Brain: Early Effects," EC/NRPB Steering Committee Feedback Transactions (the Journal of EC project meeting: Chilton, England, March 20-21, 1997. FI4P-CT95-0008) 4, 6 (January 1997).

32 Radiation Protection BE9900062

Frank HARDEMAN Policy Support on Radiation Protection

AS ALL OTHER MEMBER STATES of the ElITO- soil around the Flemish nuclear sites, and of Scientific staff iipean Union, Belgium has to guarantee, to milk, mosses, aquatic plants, and fish. Fur- Frank HARDEMAN both its own population and the other coun- thermore, we published reports on the survey Mark Loos tries, that it respects high levels of radiologi- of the triennial low-water period of the upper Philippe ANTOINE cal safety every day. This includes, among oth- river Meuse (1995)—a very suitable period for Christian HURTGEN ers, the monitoring of the levels of radioactivity intensive sampling—and on the radioecologi- Freddy VERREZEN in the environment, especially near nuclear in- cal impact of 30 years of activity at Chooz A. Alain SOHIER stallations, and emergency preparedness. In Hans VANMARCKE this respect, the know-how of SCK- CEN in radia- Also for DBIS/SPRI, SCK«CEN—in collaboration Willy SLEGERS tion protection, measurement techniques, and with IRE and the private company Cons-Ervi— Pascal DEBOODT emergency planning is offered to and used by was invited on several occasions to advise on Christian VANDECASTEELE the Federal Authorities. technical and scientific aspects of the Telerad May VAN HEES monitoring network. Our main contribution re- Noel PAUWELS garded the setting of alarm levels for gamma Paul GOVAERTS Objectives dose rate on the various types of monitors. • to support and advise the Belgian author- Supporting staff ities on specific problems concerning exist- SCK-CEN and AVN were consulted by the Bel- Eliane VANGELDER ing and potential hazards from exposure to gian Ministry of Internal Affairs for advice on Els TESSENS ionizing radiation in normal and accidental nuclear emergency planning: we transferred a situations; report to the authorities in September 1997. This report contains advice on the spending of • to improve and support nuclear emergency- funds, comments on the emergency plan of the response decisions in industrial areas from Belgian sites, procedures for the organization an economic point of view. of the evaluation cell and measurement cell, and a generic table of contents for Emergency Programme Our 1997 programme built Plans of other services acting within the Belgian on three main pillars. For the federal service emergency organization. for the protection of the population against ionizing radiation (DBIS/SPRI), SCK«CEN contin- As regards the allocation of funds, SCK- CEN and ued its share of the radiological survey pro- AVN organized a contact meeting at the supe- gramme near the Belgian nuclear installations. rior institute for emergency planning (HIN/ISPU) For the Ministry of Internal Affairs, and in col- at Florival for representatives of the provinces, laboration with AVN, SCK-CEN wrote an exper- of the army, and of various services within the tise report about the organization of the off- federal administration. On the basis of the site nuclear emergency planning in Belgium. Fi- emergency plans available, we generated a list nally, in the framework of a PhD thesis in Ap- of potential needs; then, using a formal scheme plied Economic Sciences, we developed and ap- for priority determination, used by five inde- plied methodologies to provide valuable infor- pendent members of the contractors and IRE, mation to decision-makers, in particular for ir- we generated a final list of needs and priorities. reversible emergency-response decisions (such We advised to give priority to the creation of as evacuating or shutting down a neighbouring a dynamic structure based on conventions be- chemical plant) that must be taken under con- tween all possible partners and the authorities, siderable uncertainty. We paid special atten- and on working procedures for all intervening tion to the decision problem of evacuating an cells in the emergency organization. We also industrial area when the latter is threatened by stressed the Importance of education, training, a nuclear alarm. maintenance, and all other permanent tasks to maintain a vivid emergency system.

Achievements The radiological surveillance The study of the compatibility between the of the Belgian territory was continued in 1997. emergency plan of the nuclear sites and that By order of DBIS/SPRI, we monitored the radio- of the authorities for all aspects related to the activity of rainwater, airborne dust, water, and evaluation cell and the measurement cell re- sediments of the rivers Scheldt and Nete, of sulted in a list of actions for all sites, and in

Policy Support on Radiation Protection 33 the advice to foresee a similar exercise for the emergency plans at the provincial level. In dialogue with the members of both cells, we Publication in 1997 wrote organizational procedures. During this N. PAUWELS, F. HARDEMAN, K. SOUDAN, "Assessing first step towards a working manual, we listed the Economic Impact of the Decision to Evacuate shortcomings and more detailed procedures or an Industrial Area. Do the Existing Models Ap- instructions needed. We also advised to repeat ply?," Annalen van de Belgische Vereniglng voor this exercise for the other cells in the Belgian Stralingsbescherming 22:2, 171-194 (1997). emergency organization: the crisis committee, responsible for the decision-making, and the Presentations delivered in 1997 information cell, responsible for informing international organizations and the media. We N. PAUWELS, B. VAN DE WALLE, F. HARDEMAN, also wrote a generic emergency plan for all ser- K. SOUDAN, "Emergency Response in Industrial vices involved in nuclear emergency planning. Areas. A Multiple-Objective Two-Stage Decision Tree Finally, we added a list of observed shortcom- Analysis," Eighth int. conf. on the Foundations and ings to the Royal Decree describing the nuclear Applications of Utility, Risk and Decision-Making emergency plan for the Belgian territory. (FUR VIII): Mons, Belgium, July 1-5, 1997.

N. PAUWELS, B. VAN DE WALLE, F. FIARDEMAN, At present, SCK»CEN intends to improve the K. SOUDAN, "A Multiple Attribute Decision Tree collaboration with IRE and AVN and with the Model for Nuclear Emergency Response in Industrial authorities (DBIS/SPRI, the Federal Agency for Areas," Joint int. meeting EURO XV/INFORMS XXXIV: Nuclear Control, the Ministry of Internal Af- Barcelona, Spain, July 14-17, 1997. fairs) in order to guarantee the functioning of the Telerad network, the continuation of an ef- N. PAUWELS, Th. ZEEVAERT, "Decision-Aiding ficient surveillance programme, and the real- in Nuclear Site Decommissioning. A Flexibility ization of the suggestions related to emergency Approach," First European ALARA Network Workshop: planning made during the 1997 study. Saclay, France, December 1-3, 1997. Thesis published in 1997 A PhD project applied the "options thinking" concept—so far only used in the context of cap- F. VAN LAER, N. PAUWELS, K. SOUDAN, "Risico-analyse ital investment and environmental decision— van nucleaire installaties. PC-COSYMA: Analyse van to nuclear emergency-response decisions in inde economische parameters voor Belgie," final- dustrial areas. The results so far are very year thesis, Commercial Engineering (Universitaire promising, so this approach will be further de- Faculteiten Sint-Ignatius Antwerpen), June 1997. veloped at a theoretical level in 1998. Fur- thermore, a survey in (petro)chemical factories Reports published in 1997 will assess particular parameters of the model, R. KIRCHMANN, 0. BURTON, M. DEPESTEL, P. Go- thus increasing the practical applicability of VAERTS, E. VANGELDER, J.-P. SAMAIN, J.-M. LAMBOTTE, the models developed. "Chooz-A: bilan radioecologique des 30 annees d'existence de la centrale electronucleaire des Ardennes," progress report 1986-1996 (1997).

M. Loos, F. HARDEMAN, P. DEBOODT, Ph. ANTOINE, J.-J. VAN BINNEBEEK, H. VAN HOVE, H. DRYMAEL, Scientific partners AIB-Vincotte Nuclear (AVN) — D. DEGUELDRE, "Studie betreffende nucleaire nood- Institut des radioelements (IRE) — Wetenschappelijk planning (Toestand 1997)," contract KNT9097912, Instituut Volksgezondheid/Institut Scientiflque de la expert report for the Ministry of Internal Affairs Sante Publique, Louis Pasteur (wrv-LP) — Universitaire (August 1997). (In Dutch and in French). Faculteiten Sint-Ignatius Antwerpen (UFSIA) E. VANGELDER, R. KlRCHMANN, F. HARDEMAN, Customers Dienst voor Bescherming tegen "Radiological Survey of the Belgian Upper Part of Ioniserende Stralingen/Service de protection contre the Meuse River—Report on the Triennial Low Water les radiations ionisantes (DBIS/SPRI) — Ministry of Period September 1995," contract KNT9095718.00 Internal Affairs with DBIS/SPRI (August 1997).

34 Radiation Protection

BE9900063

Pierre D'HONDT Nuclear Fuel

Scientific staff ALTHOUGH SCK-CEN already could irradiate accidental conditions. The ability to predict Leonard SANNEN /"Ik fuel in its high-flux BR2 Materials Testing fuel behaviour at high burnup under station- Paul VAN UFFELEN Reactor (MTR) and could perform high-quality ary and transient conditions will increase both Klaas VAN DER MEER postirradiation examinations, it had not em- the safety and the efficiency of LWR fuel in gen- Marc VERWERFT phasized modelling. Presently, it is making a eral, and of MOX fuel in particular. Philippe BENOIT great effort to enhance its ability to model the Baudouin ARIEN fuel behaviour up to high burnup, under sta- SCK«CEN wants to improve existing fuel mod- Serge BODART tionary and transient irradiation conditions, in elling tools by looking more closely at im- Luc BORMS view of the following considerations: proved modelling of fission-gas release, at im- Louis COHEUR proved modelling and more accurate parame- s the utilities pledge for improving the gen- Albert DANIELS ters for thermal conductivity, at basic physical eral availability of nuclear power plants in Charles DE RAEDT phenomena involved in fission-gasrelease , and terms of load following and extended op- Albert DELBRASSINE at relevant experimental tools for studying fuel eration at reduced power, with subsequent August GYS in incidental situations and even in accidental restoration of nominal power; Simone HEUSDAINS ones. Edgar KOONEN • fuel designers and cladding manufacturers Luc MIES continuously explore new products (nuclear Jean-Louis PUZZOLANTE fuel, cladding materials, new concepts, etc.); Modelling of fission-gas release in LWR Vitali SOBOLEV fuel We began developing an improved • economics and prudent use of natural re- Sven VAN DEN BERGHE fission-gas-release model in 1994. In a first sources provide strong incentives for ex- Frans VAN DEN PUT step, we recapitulated the different mecha- tending the average burnup levels of fuel in Eddy VANHOOF nisms for fission-gas release in nuclear fuel. In commercial reactors. Marcel WEBER a second, we made an overview of the relevant Victor WILLEKENS models, from which we proposed a new one. These tendencies might impact fuel integrity Hamid AÏT ABDERRAHIM and, accordingly, safety. The answer to these The model we proposed for fission-gas release questions largely relies upon models contain- Supporting staff consists of two modules. The first, termed ing many parameters, tuned to yield the ex- Rudy BERTELS intragranular, tackles the transport of the fis- perimental results, but with little understand- sion gases in the grains of the UO2 matrix. It Guido BES ing of the physical mechanisms involved. A Gerry COOLS incorporates three mechanisms: gas atom dif- strong correlation between thermal, mechan- Ludovicus DEKIEN fusion in the grain, resolution and trapping as- ical, and chemical performances of the nuclear Alex FRANSEN sociated with intragranular bubbles, and reso- fuel makes the analysis even more complex. Jozef GEUKENS lution of fission products from bubbles situ- While integral experiments provide useful in- Jan GILISSEN ated at the grain faces into a resolution layer formation for validating the models, there is a Guido HAESEN adjacent to the grain boundary. The second need for extending the knowledge of the un- Marc MATTHEUWSEN module, termed intergranular or macroscopic, derlying basic phenomena and for improving Roger MERTENS handles the transport of the fission gases at the the models. This theoretical approach in turn Jozef MEYNEN grain boundaries. requires a more sophisticated scientific analy- Ludwig NAEGELS sis and more experimental data on separate Theo NOELS effects, especially at high burnup (in excess We implemented the microscopic and macro- Jozef OEYEN of 60GWd/Mt). These effects include ther- scopic module by means of a finite-element Josephus PEETERS mal and nonthermal fission-gas releases, fuel code, and compared the global model with ex- Jozef SANNEN swelling, fuel thermal conductivity, fuel spe- perimental results. Without surprise, this ex- René SNEYERS cific heat, size (relocation) and thermal conduc- ercise suggested further improvements, in ac- Frans SWINNEN tance of fuel-pellet gaps, fuel rim effects (ther- cordance with the initial proposal. A discus- Leopold TRUYENS mal conductance and gas release), and chemi- sion on the role of grain-boundary diffusion Jef VALENBERGHS cal and mechanical fuel-cladding interactions. led us to introducing secondary phases at the André VAN BAELEN grain boundary and to formulating additional Herman VAN EYCK improvements mathematically, in addition to René VAN HOOF Objective The present R&D programme developing an alternative macroscopic module. Jos VERACHTERT aims at better predicting quantitatively the op- Jozef WAUTERAERTS erational limits of nuclear fuel and at assess- The first improvement, namely the trapping ing the behaviour of fuel under incidental and and resolution of fission products at inter-

36 Reactor Safety granular phases or traps (such as bubbles or even at very low burnup. This analysis con- metallic precipitates), is currently being im- cluded that, though the theoretical description plemented. We tested the precision of sev- of the thermal conductivity need not be re- eral routines by comparing their results with evaluated, the fitting parameters should be de- an analytical solution under particular condi- termined more accurately. In view of this, our tions. We chose and implemented the routine research programme limits itself to the devel- D03PDF from the NAG library, and started to op- opment of an innovative, more accurate mea- timize the numerical parameters in the model, surement technique of the fuel thermal con- in terms of precision and calculation time. ductivity. This technique is applicable in both in-pile and out-of-pile conditions, so the pro- From the experimental point of view, we de- gramme considers both. fined a test matrix for validating the assumptions regarding the behaviour of fission prod- Our approach to determine the thermal prop- ucts at the grain boundaries and for calibrat- erties of fuel, called power-variation method, ing the final model. The first series of mea- applies periodic temperature variations to the surements will be performed at the Labora- fuel rod and measures the response on, for tory for High and Medium-level Activity (LHMA), example, the fuel central temperature. In whereas the second was already performed in this way, it distinguishes between the thermal the Halden BWR programme. properties of the fuel and those of the gap and cladding. It requires such basic techniques as Perspectives for 1998 We will further opti- the instrumentation of the fuel rod and the mize the numerical parameters in the fission- ability to produce temperature variations in it. gas-release model and complete a parametric study to point out the dominant factors in the For developing the power-variation method, we release of fission products. We will then im- validated the heat-transport code HEATING for plement the other improvements and compare several cases of temperature variation in a fuel the model with experimental results. We will rod, by comparing its results with those of an also start implementing the alternative macro- analytical expression, for both in-pile and out- scopic module. of-pile cases. The modelling of the fuel rod was limited to the fuel column only, while the The validation of the underlying assumptions cladding and gas gap were simulated by means in the fission-gas-release model is planned to of the boundary conditions. This approach was start in early 1998, while the calibration of the required by the lack of analytical expression final model is planned for the end of 1998. describing the fuel rod in more than one material zone with a variable fuel power.

Thermal conductivity The temperature The irradiation programme BACCHANAL (Bur- is in itself an important parameter for fuel- nup Accumulation for High-performing fuel rod safety. Moreover, because it strongly in- ANALysis) aims at obtaining a set of fuel rods fluences many other fuel parameters (such with several burnup values for subsequent use as fission-gas release and pellet-cladding me- in the fuel research programme. It uses the chanical interaction), its accurate description is CALLISTO loop. In this framework, we irradiated also indispensable for the description of these several fuel rods from BR3 in BR2 during three parameters. Our research programme, started cycles. After the first and second cycles, we in 1995, aims to improve the description of the unloaded the fuel rods and performed gamma- thermal conductivity and hence the descrip- spectrometric measurements to determine the tion of the temperature distribution in the fuel linear power of each rod. A comparison with rod. neutronic calculations showed that the calculation of the relative power distribution was cor- A theoretical analysis of various descriptions rect within 3%. of the thermal conductivity reported in the literature revealed differences of 50 to 100°C in Perspectives for 1998 With the help of the the prediction of the fuel central temperature, code HEATING, we will investigate a realistic

Nuclear Fuel 37 model of fuel rod under temperature variation structural internals) have to be qualified. The and determine basic design parameters for an qualification of these highly radioactive ob- irradiation rig. As regards BACCHANAL, we will jects requires specialized infrastructure, quali- also irradiate nine fuel rods for five cycles. fied techniques, and appropriate expertise—all available at SCK«CEN'S LHMA. The project aims to provide independent expert services based Basic physical phenomena A better mod- on our extensive experience in Postirradiation elling of the fuel behaviour and, particularly, Examinations (PIES). of the fission-gas release requires a better understanding of the basic physical phenomena The CALLISTO programme, studying the overall involved. SCK«CEN currently studies two top- behaviour of advanced PWR fuel, was success- ics: gas bubbles and fuel grain boundaries. fully completed, with the remaining mechanical tensile tests on the fuel-rod claddings. It The local analysis of retained noble gas in nu- resulted in the following spin-offs: clear fuel is inherently difficult because the physical form under which it is stored varies m the STEAM programme analyses how irradi- from atomic dispersion to bubbles with a diation influences the precipitate size distri- ameter of several hundred nanometres. The bution of a new type of Zircaloy cladding; Electron Probe MicroAnalysis (EPMA) technique, • the INC A programme investigates at the mi- applied since more than twenty years, yielded crostructural level the material characteris- many important results, but its application to tics leading to unusual corrosion or hydrid- highly inhomogeneous materials is limited. We ing of a particular fuel-rod cladding; therefore developed a method to analyse a system of gas bubbles distributed in a solid ma- • for the international FIGARO programme, trix, based on multiple-voltage EPMA measure- we performed microstructural fuel exami- ments combined with a Scanning Electron Mi- nations to elucidate the basic phenomeno- croscopic (SEM) analysis of the bubble-size dis- logical mechanisms that govern the fission- tribution. A more accurate analysis of gas re- gas behaviour in high-burnup PWR MOX fuel; tained in bubbles leads to a better insight in the gas release of power-bumped fuel rods, espe- • microstructural examinations on the BR2 cially in relation to the role of grain boundaries. driver fuel addressed the presence of localized corrosion on some driver-fuel plates; One particularly interesting item in the safe • we characterized and qualified former BR3 exploitation of nuclear fuel at higher burnup rods, to be irradiated in the CALLISTO loop is the behaviour of volatile fission products. of BR2 for future R&D programmes on the The theoretical study presently conducted at thermal characteristics of nuclear fuel and SCK«CEN showed that some transport mech- the fission-gas behaviour; anisms are little established experimentally. • we provided various hot-cell services on re- The present study aims at a more thorough quest of both internal and external clients. investigation of grain boundaries and the role they can play in the transport of fission prod- Achievements The SEM examination of the ucts. In collaboration with the Universite de size distribution and number density of inter- Limoges and the EG Transuranium Institute, metallic Zr(Fe,Cr)2 precipitates in Zircaloy, a we initiated a surface analytical study of grain main parameter governing the alloy's corro- boundaries in both UO2 and MOX fuel. sion and related hydrogen uptake, turned out to be a challenge: there was no straightforward Postirradiation examination for fuel per- sample-preparation procedure, giving rise to formance assessment Nuclear fuel ven- appropriate SEM images adequately reflecting dors and operating nuclear power plants con- the precipitates population. Although we suc- tinuously endeavour towards higher perfor- cessfully established an appropriate procedure mance, reliability, and safety. To that end, both on unirradiated samples, the transfer of this current and new improved primary core com- procedure to hot-cell conditions for applica- ponents (such as fuel rods, control rods, and tion on irradiated specimens proved very diffi-

38 Reactor Safety cult. Specifically, it was difficult to control the cleaire, and SEM energy-dispersive spectrom- exact timing of the successive etching and rins- etry analysis of a vitrified waste sample coring steps. As a consequence, only part of the roded in situ (HADES) and of the laser traces on irradiated specimens could be examined suc- a Zircaloy tube on behalf of FBFC International. cessfully in 1997. Perspectives for 1998 We will complete the Optical microscopy, SEM, and EPMA of a partic- SEM evaluation of size distribution and num- ular CALLISTO fuel rod revealed its detailed cor- ber density of secondary precipitates in irra- rosion and hydriding characteristics (extent, diated Zircalloy cladding, perform comprehen- morphology, and chemistry). sive EPMA and SEM research on the FIGARO fuel to elucidate the basic phenomenological mech- In the framework of the FIGARO programme, anisms governing the fission-gas behaviour, four instrumented MOX fuel segments were carry out additional research to address fur- transported from Halden to our laboratory. ther the localized corrosion of some BR2 driver- Out of each segment, we manufactured a speci- fuel plates, and evaluate, on behalf of MOX fuel men, conditioned it for microstructural exami- vendors, fresh MOX fuel in terms of plutonium nation, and performed a general optical micro- homogeneity and porosity characteristics. Sev- scopic survey before submitting it, next year, eral international programmes are also being to elaborate EPMA and SEM research on the fuel. negotiated with external customers.

Extended microstructural examinations of the grain structure and secondary-phase particles Conceptual studies of incidental and acci- in the aluminium cladding of several BR2 driver- dental fuel experiments Increasing the al- fuel plates allowed us to exclude metallurgical lowed burnup of nuclear fuel can provide con- effects and intergranular attack as the possible siderable savings on the fuel-cycle costs of nu- corrosion mechanisms. Galvanic or deposition clear power plants. However, one must in- corrosion were assessed by EPMA. Despite a vestigate the behaviour of high-burnup fuel, clear tin contamination on one particular sam- particularly under severe transient conditions, ple, subsequent investigations did not confirm to ascertain that the operation margins are this mechanism as responsible for the local- safe. Such an investigation requires represen- ized corrosion phenomena of some BR2 driver- tative in-pile experiments. The project there- fuel plates. In view of the high costs involved fore aims to investigate the industrial needs in a systematic (destructive) microprobe inves- for, assess the feasibility of, and develop in-pile tigation of a large number of samples, we are rigs allowing severe tests on LWR fuels, with a now running a nondestructive analysis cam- high probability of fuel failure or even melt- paign. ing and in representative thermohydraulic conditions. It envisages two irradiation devices: Thirty-seven former BR3 MOX fuel rods, with COSAC for single-rod and DESTIN for multirod different plutonium contents and with a burn- testing, respectively. up ranging from 12 to 20GWd/tM, have been characterized in view of their anticipated ap- COSAC (Contaminant Operation SAfety Cap- plication in future fuel R&D programmes; they sule) is inspired by our existing pressurized- were found to be qualified for their further ir- water capsules. The modifications aim at radiation in the PWR-simulating CALUSTO loop reaching the prototype stage of the thermo- in BR2. Out of them, fifteen rods selected for hydraulic irradiation conditions in the capsule, irradiation in BR2 cycles 1/97 and 2/97 were by adding a so-called jet-pump system that im- analysed nondestructively for the power expe- proves the circulation along the fuel rod, not rienced during their irradiation. unlike a BWR'S primary water circulation. In addition, we will adapt the waste-water treat- Several miscellaneous hot-cell services have ment of the device to allow destructive tran- been provided on behalf of both internal and sients and the operation of leaking rods over external clients, among which SEM MOX pow- periods of several days. In 1997, we started ders characterization on behalf of Belgonu- the concept definition and feasibility study.

Nuclear Fuel 39 DESTIN (DEStructive Testing IN-pile loop) is a compact integrated PWR loop installed in the central channel of BR2, which can accommo- Presentations delivered in I 997 date 3 x 3 or 5 x 5 test fuel bundles. This modular installation can be used in a wide spec- Ph. BENOIT, A. DELBRASSINE, B. ARIEN, Ch. DE RAEDT, trum of experiments, with only adaptation of "Destin—An Integrated PWR Loop for the Destructive (relatively) inexpensive internal parts. Thanks Testing of Fuel Bundles," TopFuel'97: Manchester, to the unique geometry of the BR2 core, it can United Kingdom, June 9-11, 1997. accept actual-size PWR fuel rods, beside re- L. BORMS, P. DE REGGE, A. GYS, V. WILLEKENS, "Vali- fabricated and instrumented ones. It is cur- dation of a New Method for Burn-Up Determination rently targeted at three main fields of appli- by Means of Gamma-Spectroscopy," Annual meeting cation: RiA-type tests, fuel-bundle degradation on Nuclear Technology, German Nuclear Society: processes (for example, during LOCA events), Aachen, Germany, May 13-15, 1997. and behaviour of severely degraded fuel. In- pile fuel quenching is an application where an J. C. GARCIA, P. VAN UFFELEN, "Analysis of Halden integral experiment would help address still Fuel Experimental Data with the ENIGMA Code," open questions. Meeting of the Sociedad nuclear espanola 1997: La Corona, Spain, November 5-7, 1997.

In 1997, work on DESTIN focused on establish- V. SOBOLEV, P. VAN UFFELEN, K. VAN DER MEER, ing contacts with potential partners. An inter- "Problems of In-Pile Measurement of the Nuclear Fuel national programme called FATE, aiming at the Thermal Properties," TopFuel'97: Manchester, United verification of the criteria for the high-burnup Kingdom, June 9-11, 1997. fuel in case of a LOCA, was proposed in co- operation with Belgonucleaire. The Forschung- Y. VANDERBORCK, L. MERTENS, J. DEKEYSER, zentrum Karlsruhe / Institute fur Reaktor- L. SANNEN, "Fuel R&D International Programmes, sicherheit (Germany) and the Institut de Pro- a Way to Demonstrate Future Fuel Performances," tection et Surete Nucleaire (France) showed an TopFuel'97: Manchester, United Kingdom, June 9-11, initial interest, to be further concretized. 1997. M. VERWERFT, C. MARTENS, L. SANNEN, A. DELBRAS- Perspectives for 1998 The COSAC project will SINE, "Quantifying Xe in Nuclear Fuel: (Im)Possible be proposed for first-phase approval to SCK- by Microprobe Techniques?," Topical day on Fuel CEN's Committee for Examination of Experi- Behaviour: SCK-CEN, Mol, Belgium, November 5, 1997. ments (CEE) in early 1998. This should lead to a decision to proceed with the detailed study. Thesis published in 1997

D. SCHROYEN, "Validation du code HEATING pour The DESTIN team will continue its efforts to as- une pastille de combustible soumise a des flux sess the needs for international safety experi- sinusoidaux," final-year project, Industrial Engi- ments and to stimulate the interest of possi- neering (Institut Superieur Industriel de Bruxelles), ble partners and sponsors, both in Belgium and September 1997. abroad. The fifth framework programme of the EC should be the occasion to concretize project proposals. Reports published in 1997 P. VAN UFFELEN, "An overview of fission product release mechanisms," internal SCK-CEN report (1997). R-3144.

Ten reports were also issued to our customers. They Scientific partner Belgonucleaire (BN) are commercial and confidential, and may not be released to third parties. Customers Belgonucleaire (BN) — British Nuclear Fuels Ltd (BNFL) — Franco-beige de fabrication de combustibles International (FBFC int.) — Mitsubishi Heavy Industries Ltd (MM) — Nuclear Fuel Industries Ltd (NFI)

40 Reactor Safety BE9900064

Hamid AIT ABDERRAHIM Reactor Physics

HP HE FUEL RESEARCH department gathers ex- Achievements The VIPEX configuration con- Scientific staff Apertise in different reactor-physics fields, sists of a central 17x17 MOX fuel assembly sur- Hamid AIT ABDERRAHIM among which neutronics calculations, reactor rounded by four 17x17 UO2 fuel assemblies Klaas VAN DER MEER dosimetry, reactor operation, reactor control, in a cross configuration. At its periphery, three Daniel MARLOYE and nondestructive analysis on reactor fuel. rows of 4% enriched UO2 rods make it critical Pierre D'HONDT This expertise is applied to own research pro- at a water level of about 40 cm. Luc BORMS grammes, using the VENUS critical facility for YVO BORTELS MOX fuel-core physics or the BRI reactor for The thermal neutron flux in the centre of a UO2 David DE MAEYER ex-core neutron transport and shielding prob- assembly is about twice the flux in the centre Charles DE RAEDT lems for qualification and validation within an of a MOX assembly, resulting in a large flux gra- Edouard MALAMBU international partnership. It is also used in dient (or flux tilt) at the boundary between UO2 Georges MINSART programmes of other departments, such as and MOX assemblies. The largest flux tilt, found Olivier PICAVET (trainee pressure-vessel steel, BR2 dosimetry, irradia- in a comer rod of the MOX assembly, causes from EdF) tion experiments preparation and interpreta- a large difference in power distribution inside Luc VAN DEN DURPEL tion in BR2, and BR3 dismantling. The follow- the rod. This is of importance for operation Pieter VANMECHELEN ing sections report on the activities in four do- and safety, because the highest rod power is a Bernard VERBOOMEN mains: limit for the power of a whole assembly and, in Victor WlLLEKENS • core physics; the same way, the highest power in a rod can be • ex-core neutron transport; a limit for the maximum allowable rod power. Supporting staff m experiments in MTRS; Herman GEENS • international benchmarks. The flux tilt has been measured by the very fine Jozef VERREES gamma scanning of an irradiated pellet from Jozef LEEUWS the above-mentioned corner rod. It was ver- Raymond MERMANS Core physics: the VIPEX programme The ified by a measure of fission products origi- Jozef OEYEN VIP (VENUS International Programme), executed nating from the outer border of the pellet, as Ludovicus VERSTREPEN from 1990 to 1992, aimed at determining ba- caught by an aluminium foil surrounding it. Ivo VERWIMP sic parameters of PWR and BWR MOX core configurations for licensing purposes. Though it The original VIPEX configuration simulates the successfully reached its aims, some issues re- water density in a PVVR at full power by alu- mained unsolved, particularly in the field of re- minium rods placed between the fuel rods. We actor operation. The delayed neutron fraction measured the reactivity effect of the water den- and related reactivity effects are little known, sity, which is a measure of the difference in re- but of great interest for reactor operation and, activity between the so-called "hot" and "cold" to a lesser extent, for safety. The VIPEX (VIP conditions of a power reactor, by unloading in Extension) programme will determine some of several steps the aluminium density-reduction the most interesting parameters for operating rods. After each step, we measured the criti- PWR MOX reactor cores. cal level and reactivity effect of the water level variation, to determine the reactivity change. Objective • to determine experimentally parameters of The power of a fuel assembly in a power reactor primary importance for reactor operation is monitored by a fission chamber, placed in its and to provide experimental data from rep- centre. The response of the chamber in a MOX resentative "clean" experiments for the de- assembly is different from that in a UO2 assem- velopment, improvement, and validation of bly, because of the different neutron flux and calculation methods for reactor operation. spectrum. Because the response measured in VIP showed a discrepancy between calculated Programme VIPEX foresees two phases. and experimental values, a new measurement Phase 1, started in 1996, determined the ameri- was suggested, together with additional irradi- cium effect, the control rod worth, and the ation of manganese and gold activation foils delayed neutron fraction. Phase 2, executed to determine the relative contributions of the in 1997, measured the flux tilt, the reactivity thermal and epithermal neutron fluxes. An effect of water density, and the detector re- additional power run determined the relative sponse and fission rate distribution in the core. power of the MOX and UO2 assemblies.

Reactor Physics 4T Perspectives for 1998 We will issue a final Perspectives for 1998 We will issue a final report on the second phase of VIPEX in the first report on the measurements of both configu- half of 1998. We also proposed several VIPEX rations in the first half of 1998. BWR programmes, similar to the old VIP BWR one, except for more advanced configurations. Core physics: OVERMOX Since the decision to recycle the plutonium produced by Core physics: the VENUS NBN programme LWR power plants, a little more than 20% of The VIP BWR programme aimed at determining the assemblies loaded in the Belgian reactors basic parameters of BWR configurations with of Tihange 2 and Doel 3 contain MOX fuel 8x8 fuel elements. It investigated UO2, MOX, rods. For safety reasons, the loading of a and Island-MOX configurations. As a prolon- full MOX core was not considered, because the gation, the VENUS NBN programme investigates present nuclear power reactors were not de- the same basic parameters for UO2 and MOX signed for them, but rather for full UO2 load- configurations of 9 x 9 fuel elements: the criti- ing. The OVERMOX (OVERmoderated Mixed OX- cal water level, the reactivity effect of the water ides) project, initiated in January 1997, aims to level, and the axial and horizontal fission-rate study the use of full MOX cores in LWRS. distribution using gamma scanning. The VENUS critical facility is the right tool to Objective perform this study. Nevertheless, it required some adaptations. To keep the power at a con- • to provide a series of benchmarks for val- stant level, comparable to that of a full UO2 idating nuclear reactor codes, especially loading, one must increase the pitch of the with respect to criticality calculations and full MOX loading. This overmoderation also al- fission-rate distributions in BWR MOX core lows to maintain the efficiency of the control configurations with 9x9 fuel assemblies. through the absorber rods. Programme We investigated two configura- Programme The OVERMOX project is divided tions, somewhat different from our previously in two major steps. First, a feasibility study published descriptions. Both consist of 16 fuel must estimate the necessary adaptations to assemblies in a 4 x 4 array, with the twelve VENUS (number of MOX rods necessary to make outer assemblies consisting mainly of 3.3% en- the reactor critical given the maximum pluto- riched UO2 fuel with an outer row of 4% en- nium weight that may legally be loaded, grid riched UO2 fuel. The configurations differ in pitch, cost of new grids, downloading of the the four inner assemblies, which have a 3 x 3 grids to flood more than 50 cm of fuel length water hole in the centre. The VENUS NBN UO2 and related adaptation of the control rods, wa- configuration has two inner UO2 assemblies ter level switches, etc.) Then, once the VENUS fa- with gadolinium rods and two without gadolin- cility has been adapted, the measurements can ium, positioned diagonally with respect to each take place: critical level, reactivity, fc ff> void other. The VENUS NBN MOX configuration re- e coefficient, boron reactivity effect, etc. places the UO2 assemblies with gadolinium by MOX fuel assemblies, containing medium (10%) enriched MOX (M-MOX), low (5%) enriched MOX Achievements At the moment, though the (L-MOX), gadolinium fuel, and a few UO2 rods. feasibility study is still ongoing, the measurements have been initiated: potential partners have shown interest for the b ff and void co- Achievements We determined the critical wa- e efficient measurements. The OVERMOX project ter level, the reactivity effect of the water level, thus follows the path of the VTPEX and VIPO pro- and the axial and horizontal fission rate dis- grammes. With the present MOX fuel inven- tribution using gamma scanning, for both the tory available at VENUS, we can achieve a crit- UO2 and the MOX configurations. During the ical loading using only high (14%) and medium determination of the UO2 horizontal fission- (9.6%) enriched MOX; we are also considering rate distribution, some results appeared out- configurations with boric acid. side the expected uncertainty range, so we performed an additional measurement campaign.

42 Reactor Safety Ex-core neutron transport As part of the the concrete backscattering, should be consid- Reactor Physics programme, we conduct both ered for the ex-vessel dosimetry. experimental and theoretical activities, mainly to maintain and improve through experimen- Beside using LEPRICON, we worked in 1997 on tal validation the calculational tools (codes and improving the benchmark database, containing cross-section libraries) used for ex-core neu- reference experimental data, and on adding to tron transport, particularly those used for the LEPRICON the experimental data of the VENUS-l assessment of the pressure-vessel fluence. benchmark experiment. Before starting this work, we showed the validity of the linearity The WINES (Water Inelastic Neutron scattering assumption used in the adjustment module. Experimental Study) experiment, conducted in the BRi reactor in 1995-1996, delivered ex- Experiment preparation in MTR The perimental data for validating the ability of preparation of experiments to be conducted or the calculational tools to treat the fast-neutron performed in the BR2 MTR aims at characteriz- transport through large thicknesses of water. ing the neutron and gamma fields around the From the relative experimental data obtained experimental devices. by means of miniature fission chambers (238U, 23SU, 237Np, and 232Th), we showed a large underestimation of the calculated fast flux and To determine the nuclear characteristics of a an overestimation of the thermal flux when series of new irradiation devices, projected for, the penetration in the water became important. or actually irradiated in, BR2, the computa- Therefore, an extension of the WINES experi- tional team of the Fuel Research department ment, conducted in 1997, measured absolute performed neutron and gamma calculations. fission rates using the same fission chambers Because these irradiation devices will mainly be and completed a full gamma tomography of introduced into strongly excentric channels of the fission source (a 93% 235U plate). These the BR2 core (for example, at the fuel-reflector complementary measurements revealed a fast interface or in the peripheral large H chan- neutron contribution in the water container nels) or even outside the reactor, most calcu- (1 m x 1 m x 1 m) coming directly from the BRi lations were performed in two-dimensional ge- core. Supplementary measurements of the in- ometry with the DORT 3.1 multigroup neutron cident thermal flux on the fissile plate were also and gamma particle transport (SN) code. The completed. These experimental data will allow main devices thus studied were a full modelling of the experimental device, in- • the CALLISTO loop, in which nine water- cluding part or all of the BRi reactor, to take cooled fuel rods (in a square lattice) are ir- into account the reactor contribution. radiated in PWR conditions; • the PRF irradiation device, with highly en- In the field of pressure-vessel fluence assess- riched uranium parallel-plate targets, for ment, two analyses were carried out simulta- the production of molybdenum; neously during 1997: the in- and ex-vessel dosimetry of Saint-Laurent des Eaux, a French • the projected CEPHEID loop, possibly to be 900 MWe PWR. The analysis, conducted us- irradiated in the peripheral large H5 chan- ing the LEPRICON code system, showed that the nel, in which large modules of gas-cooled present version of the code appropriately as- lithium compounds, flanked on two sides by sesses the pressure-vessel fast fluence (uncer- beryllium pebble beds, could be irradiated; tainty around 20%) and can adjust these fluences and reduce their uncertainty by a fac- • the MERLIN pool-side facility, possibly to tor 4 (to less than 5%) when using in the adjust- be built just outside the reactor vessel at ment module results coming from an in-vessel the reactor mid-plane level, to allow large (surveillance capsule) position. This version is amounts of steel samples to be irradiated however less trustworthy for the adjustment of in the framework of reactor vessel embrit- the pressure-vessel fluence based on ex-vessel tlement research programmes. dosimetry; the sensitivity matrices should be revisited and supplementary biases, such as

Reactor Physics 43 Other studies refined the methods applied to scheme as a whole. For instance, the two- determine the fuel rod fission power, in par- group coarse-mesh codes designed for core cal- ticular by calculating the fission density in a culations use "equivalence procedures" (or dis- fuel rod from the fast or thermal flux measured continuity factors) to modify the cell and as- by a dosemeter in a position close to the fuel sembly parameters in such a way as to com- rod. Here, the calculations were performed pensate for possible errors due to homoge- with the one-dimensional multigroup neutron nization, mesh effects, group collapsing, etc. transport (SN) code DTFIV. The data upon which cross-section libraries are based need to be validated for MOX/UO2 assemblies. International benchmarks To maintain the expertise of and train the staff involved in For all the above reasons, the second phase reactor physics, SCK»CEN is either taking part of the PDWA benchmark proposed to compare in international benchmark exercises or orga- the results obtained by different contributors, nizing such events on both theoretical and ex- starting from the beginning of their computa- perimental aspects. In 1997, we participated tional scheme, that is, from detailed geometri- in two theoretical benchmarks organized by cal and physical data of the reactor core con- the Nuclear Science Committee of NEA. The figuration. first one concerns the power-distribution calculation within UO2 and MOX assemblies and Fourteen contributions, testing more than fif- the second one is dealing with ex-core neutron teen computational schemes, have been sub- dosimetry and is organized by the NSC Task mitted from ten countries. The methods dif- Force on Computing Dose and Modelling of Nu- fer in the nuclear reactor design: they build on clear Radiation-Induced Degradation of Reac- collision probabilities, SN transport finite dif- tor Components (TFRDD). ferences, diffusion finite differences, nodal diffusion, or power reconstruction. All but The Nuclear Energy Agency/Nuclear Science SCK«CEN contributors have used cross-section Committee benchmark on Power Distribution libraries based on up-to-date nuclear data eval- Within Assemblies (PDWA) was proposed in the uations SUCh as JENDL-3.2, JEF-2.2, or ENDF/B-VI. framework of the working party on Plutonium The SCK> CEN home library, by contrast, is based Recycling organized by the OECD/NEA Nuclear on old evaluations, namely the ABBN and the Science Committee. It aims to determine the KEDAK libraries. For core calculations, the pin-by-pin power distribution in a reactor core first contributor from SCK-CEN has used the containing both UO2 and MOX fuel assemblies. well-known DORT two-dimensional SN trans- A first stage (1991) was devoted to whole- port code, while the second tested a home- core calculations, starting from provided sets developed nodal diffusion code. of two-group cell-homogenized data—a task made difficult by three factors: the required The analysis of this second phase of the PDWA neutron spectrum is highly space-dependent, benchmark indicates that our 40-group library especially near the boundary between MOX and is still good for transport calculations relevant UO2 assemblies; the definition of cell-by-cell to UO2 cells and UO2-dominated core loading, diffusion coefficients (radial and axial) is not but not for MOX lattices, for which the cell pa- always well-founded; and the procedure to de- rameters depart significantly from the average rive homogeneous equivalent cell parameters (and best) trend. as well as the transport cross-sections can become a major source of errors. Generally, In the framework of the NSC TFRDD, SCK-CEN one first calculates the assemblies involved in provided the data of two benchmarks, VENUS-1 the reactor core (cell calculations) using trans- and VENUS-3, to allow participants to check port codes (to solve an integral or integrod- the validity of their calculational tools to as- ifferential transport equation) with a hetero- sess the neutron fluence at critical positions, geneous description of the cells and a fine such as the pressure vessel of a reactor. Using treatment of the energy variable. To this end, the LEPRICON code system, SCK-CEN also con- one must consider a neutronic computational tributed its results for the VENUS-I benchmark.

44 Reactor Safety K. VAN DER MEER, H. AlT ABDERRAHIM, D. MAR- LOYE, G. MINSART, P. D'HONDT, Th. MALDAGUE, Scientific partners Belgonucleaire (BN) — J. BASSELIER, "Recent Benchmark Experiments for Korean Atomic Energy Research Institute (KAERI) — LWR Pu-Recycle," American Nuclear Society Winter British Nuclear Fuels Ltd (BNFL) — Mitsubishi Heavy Meeting: Albuquerque, New Mexico, USA, November Industries Ltd (MHI) — Central Research Institute 16-20, 1997. of Electric Power Industry (CRIEPI) — Nuclear Fuel Industries Ltd (NFI) — Electricite de France (EdF) Reports published in 1997

H. AIT ABDERRAHIM, "Computing Radiation Dose to Reactor Pressure Vessel and Internals" (1997). OECD NEA/NSC/DOC(96)5.

Publications in 1997 A. BALLESTEROS, H. AIT ABDERRAHIM, L. DEBARBERIS, T. LEWIS, C. SCIOLLA, M.J. VALO, "Neutron Dosimetry L. H. BAETSLE, Ch. DE RAEDT, "Limitations of Actinide and Damage Indexation in European Reactors" Recycle and Fuel Cycle Consequences: A Global (December 1997). AGE-MADAM(97)D2. Analysis. Part 1: Global Fuel Cycle Analysis," Nuclear Engineering and Design 168, 191-201 (1997). L. BORMS, "WINES(EX) Total Fission Rate Determination from Highly Enriched Uranium Converter Used in L.H. BAETSLE, Ch. DE RAEDT, "Limitations of Actinide WINES(EX) Experiment," SCK'CEN report (September Recycle and Fuel Cycle Consequences: A Global 1997). R-3210. Analysis. Part 2: Recycle of Actinides in Thermal Reactors: Impact of High Burnup LWR-UO2 Fuel Ch. DE RAEDT, E. MALAMBU, "CALLISTO 1997 (cycle Irradiation and Multiple Recycle of LWR-MOX Fuel on 01/97A): Neutronic Calculations Performed by the Radiotoxic Inventory," Nuclear Engineering and SCK'CEN: Situation April 30, 1997," internal SCK'CEN Design 168, 203-210 (1997). report (June 10, 1997). TN-0005; chDR-EM/chdr- em/CALL; D081003/260/97-03. L. H. BAETSLE, Ch. DE RAEDT, "Some Aspects of Risk Reduction Strategy by Multiple Recycling in Fast E. MALAMBU, Ch. DE RAEDT, ""MO Production Burner Reactors of the Plutonium and Minor Actinide in the BR2 MTR: Neutronic Calculations," internal Inventories," Nuclear Engineering and Design 172, SCK'CEN report (November 14, 1997). EM.CDR/em- 359-366 (1997). 34/D0255016/208/97-03.

D. MARLOYE, K. VAN DER MEER, P. D'HONDT, Presentations delivered in 1 997 "VIPEX: Experimental Results of Phase 1," SCK'CEN Ch. DE RAEDT, S. VAN WINCKEL, J. BASSELIER, confidential contract report (February 1997). Th. MALDAGUE, "Validation of Actinide Cross- D. MARLOYE, K. VAN DER MEER, P. D'HONDT, "VENUS Sections for LWRs in the Framework of the ARIANE BWR-NBN: Experimental Results of the MOX Mock-Up," Programme: Work Performed by SCK'CEN and by SCK'CEN report (April 1997). R-3208 revised. Belgonucleaire," Int. conf. on Nuclear Data for Science and Technology: Trieste, Italy, May 19-24, 1997. 0. PICAVET, H. AIT ABDERRAHIM, "Application du Proc, 7. LEPRICON a la dosimetrie interne de Saint-Laurent des Eaux-1," SCK'CEN report (December 1997). R-3235. Ch. DE RAEDT, R. CARCHON, G. MINSART, T. AOUST, "Burn-up Assessment of Spent Fuel Assemblies by K. VAN DER MEER, D. MARLOYE, P. D'HONDT, "VENUS Analysis of the Neutron Emission. Comparison of BWR-NBN: Experimental Results of the Additional Measured and Calculated Data," OECD topical meeting Horizontal Fission Rate Distribution Measurement on Safety of the Nuclear Fuel Cycle: Newby Bridge, of the UO2 Mock-Up," SCK'CEN report (April 1997). United Kingdom, October 28-30, 1997. Proc, 8. R-3192rev. 1.

0. PICAVET, H. AIT ABDERRAHIM, P. RISCH, "Validity of K. VAN DER MEER, D. MARLOYE, P. D'HONDT, "VENUS the Linearity Assumption in the LEPRICON Adjustment BWR-NBN: Experimental Results of the UO2 Mock-Up," Module," American Nuclear Society Winter Meeting: SCK'CEN report (April 1997). R-3164. Albuquerque, New Mexico, USA, November 16-20, 1997. Proc. 77 TANS AO77 1-560, 339-340.

Reactor Physics 45 BE9900065

Baudouin ARIEN Reactor Safety Analysis

Scientific staff ISK ASSESSMENTS of nuclear installations sition rates. For that purpose, we built a Baudouin ARIEN R require more and more accurate safety library of the frequently used probability Anne DE BREMAECKER and reliability analyses to estimate the conse- density functions. The program can also Jean-Luc DELCOUX quences of accidental events and their proba- handle a state-dependent ageing of the com- Nathalie DESSARS bilities of occurrence. ponents. Other results have been obtained Simone HEUSDAINS in the field of variance reduction. This work Dominique LAMY is carried out in the framework of a PhD the- Objective Kamreddine OULIDDREN sis. Marc VANDEGEHUCHTH • to develop expertise in probabilistic and de- terministic reactor safety analysis. Aid to diagnosis of pressurized-water loop tran- sients This work, carried out in the framework of a PhD thesis, focused in 1997 on Programme The research programme re- the modelling dependencies in complex sys- lates to four main activities: tems. The approach of modelling dependen- m developing a software for reliability analysis cies in real application was developed and im- of large systems; plemented on real examples, taken from the experimental facility CAJLLISTO. By then, the PhD • developing an expert system for the aid to thesis was ready to be submitted. diagnosis; • developing and applying a probabilistic re- Probabilistic Reactor Dynamics The relia- actor dynamics method; bility study of a dynamical system needs to consider many sequences or branches of a * participating in the international PHEBUS-FP dynamic event tree. The difficulty linked to programme for severe accidents. the many possible orderings of the branching points corresponding to failures or control actions is compounded by the fact that many un- Achievements The achievements encom- certain parameters influence the results of the pass several aspects. analysis.

Development of CAMERA CAMERA is a software A first method to deal with uncertain parame- for computer-aided reliability analyses of large ters which are exclusively transition times has systems using two optional techniques, the already been developed, in collaboration with Markovian approach and the Monte Carlo sim- ULB, and applied on a simple model of a level-1 ulation, both allowing the treatment of much PSA scenario. In the framework of another PhD more general systems than the classical fault- thesis, we are extending the method to every tree method. The software is developed in col- kind of uncertain parameter, to allow the com- laboration by ULB (Markovian processor) and putation of level-2 accidents in which many pa- SCK>CEN (Monte Carlo simulation module and rameters are poorly known (for example, those preprocessor aiming at a user-friendly intro- coming from expert judgment). duction of the data describing the system to be analysed). Severe accidents To acquire expertise in severe accident modelling, SCK-CEN participates SCK'CEN's contribution in 1997 consisted in in the international PHEBUS-FP programme. Of • completing the coupling of the Markovian the six scheduled experiments, two have al- processor with the preprocessor; ready been performed. SCK-CEN initiated its participation some years ago by detaching one « improving the preprocessor by adding op- scientist to CEN Cadarache for the phenomeno- tions (for example, various models for the logical understanding of the degradation, no- common-cause failures); tably by post-test examinations, and another • further developing the Monte Carlo simula- one to JRC Ispra for the modelling of the tests tion processor to broaden the application with the ICARJE2 code. The phenomenologi- field of the software; the program can now cal work showed the importance of nonmod- handle components with nonconstant tran- elled factors such as the interactions of the

46 Reactor Safety structural and absorber materials with the fuel. These lead to a higher degradation than expected and to a strong lowering of the corium Scientific partners Universite Libre de Brux- melting temperature (2 500 K, compared to the elles (ULB) — Vrije Universiteit Brussel (VUB) — 2 800K foreseen by the classical UO2/ZrO2 University of Maryland — Tractebel Energy En- phase diagram). gineering (TEE) — European Commission (EC) -— Forschungszentrum Karlsruhe (FZK) SCK-CEN is now using the RELAPS/SCDAP code for similar modelling and will compare the results with those produced by ICARE2. To this end, it also initiated a collaboration with FZK. The simulation of the first test FPTO with Publication in 1997 RELAPS/SCDAP has been started. J.-L. DELCOUX, P.E. LABEAU, J. DEVOOGHT, "Ap- proximate Zero-Variance Monte Carlo Estimation of Perspectives for 1998 The application Markovian Unreliability," Annals of Nuclear Energy of CAMERA to real problems in nuclear power 25:4-5, 259-283 (1998). plants is now investigated. Living PSA seems to be one of the most promising applications, in Presentations delivered in 1 997 particular for the reliability analysis of systems involved in the safety of the nuclear power B. AMEN, "The CAMERA Software in Markovian plant and placed in outage situations. In a Reliability," Topical day on Safety Studies: SCK-CEN, first step, demonstrative examples will prove Mol, Belgium, December 10, 1997. the feasibility of such analyses. J.-L. DELCOUX, "Variance Reduction for Simultaneous Monte Carlo Estimation of Many Markovian Unrelia- The Monte Carlo module will be coupled with bility Functionals," Int. conf. on Advances in Safety the CAMERA software. It will be further de- and Reliability (ESREL'97): Lisbon, Portugal, June veloped to take into account different mainte- 17-20, 1997. Proc, 2123-2128. nance policies and will be applied to a concrete case, to be selected. J.-L. DELCOUX, "A Variance Reduction Method for Function Estimation and Its Application to System Reliability Analysis," Workshop on Rare Event In Probabilistic Reactor Dynamics, the method able to treat the parameter uncertainties will Simulation: Aachen, Germany, August 28-29, 1997. be implemented in a C program and will be ap- J.-L. DELCOUX, "Application of the Monte Carlo plied first on a level-1 PSA scenario. Methods to the Non Markovian Cases," Topical day on Safety Studies: SCK-CEN, Mol, Belgium, A model of a level-2 scenario with realistic December 10, 1997. data will be developed in collaboration with ULB and proposed as a benchmark exercise. We N. DESSARS, "Dynamic Reliability—The Influence of will then compare the results obtained by our Uncertain Parameters," Topical day on Safety Studies: method to those obtained, for instance, by a SCK'CEN, Mol, Belgium, December 10, 1997. Monte Carlo simulation. N. DESSARS, J. DEVOOGHT, "Role of Time Delays in Event Trees," Int. conf. on Advances in Safety and The participation in the PHEBUS-FP programme Reliability (ESREL'97): Lisbon, Portugal, June 17-20, will continue. Pre- and post-test calculations 1997. Proc, 2105-2112. with ICARE2 at JRC Ispra will proceed and the modelling of the second test FPTi with RELAP5/ K. OULIDDREN, A. NOWE, "Incremental Fuzzy Modelling of Dependencies in Complex Physical SCDAP will be undertaken. Systems," Annual meeting of the North American Fuzzy Information Processing Society (NAFIPS'97): Syracuse, New York, USA, September 21-24, 1997. Proc., 136-141.

Reactor Safety Analysis 47 BE9900066

Jose VAN DE VELDE, Albert FABRY, Eric VAN WALLE, Rachid CHAOUADI

Reactor Structural Materials Reactor Pressure Vessel Steels

Scientific staff Tp HE STRATEGIC IMPORTANCE of permanent material were within the trend set by the pre- Albert FABRY A assurance of the integrity of nuclear Re- vious capsules. The relative shifts for the weld Eric VAN WALLE actor Pressure Vessels (RPVS) has always been and heat-affected zone were smaller than that Jose VAN DE VELDE acknowledged. Plant Life Management (PLIM) of the upper-core-shell base metal. Rachid CHAOUADI concepts, of increasing importance to the nu- Jean-Louis PUZZOLANTE clear world, emphasize first of all the degra- The surveillance capsule Tihange II/3 arrived Theo VAN RANSBEECK dation issue of irreplaceable structures, such at our premises. Early 1998, we will dismantle Hamid AIT ABDERRAHIM as the RPV. The research on the susceptibil- it, then test the specimens mechanically and Jean-Pierre WANNIJN ity of the RPV steels to neutron-irradiation em- evaluate them. Paul DE BAKKER brittlement, the understanding of the under- Kristel VAN OUYTSEL lying degradation mechanisms and method- In the framework of standardization, our labo- Pieter VANMECHELEN ologies to ensure safe exploitation constitute ratory performed instrumented impact test- Marc VERWERFT an important activity of the Reactor Materi- ing of CBR (Community Bureau of Reference, Frans VAN DEN PUT als research department. Our programme fo- EC contract) reference specimens for charac- Marc SCIBETTA cuses on the consolidation of the enhanced terization of Batch-4 specimens of high energy surveillance technology that encompasses ad- (nominal 160J). Supporting staff vanced fracture-toughness mechanical testing Theo NOELS and microstructural interrogation supported For the Brazilian Navy, CTMSP, we designed the Ronny VOSCH by modelling and micromechanics. "INAP Reactor Vessel Surveillance Programme," Marc EYKMANS which includes concepts of enhanced surveil- Peter BECKERS lance. This programme was the first part of our Objectives In support of the RPV integrity Guido BES international co-operation and support pro- assessment, Jan GILISSEN gramme, and will continue till 1999. Jozef MEYNEN to develop enhanced surveillance concepts Jozef VERAGHTERT by applying micromechanics and fracture- A co-operation agreement, sponsored by the Leo VAN HOUDT toughness tests to small specimens, and by Belgian Office for Scientific, Technical, and Cul- Antonio PELLETTIERI performing damage modelling and micro- tural Affairs, was established between SCK« CEN Joseph DEYEN structure characterization; and the Bulgarian Academy of Sciences. The agreement involves support, training, and con- to demonstrate our methodology on a broad sultancy on surveillance issues related to the database; Korloduy nuclear power plants. to achieve regulatory acceptance and industrial use. programme The enhanced RPV surveil- Pressure vessel steel surveillance The lance strategy developed in Belgium combines main surveillance activities are state-of-the-art micromechanical and damage modelling to the evaluation of Charpy V notch • to assure the follow-up of the RPV steel of (CVN) load-deflection signals, tensile stress- the Belgian nuclear power plants by eval- strain curves, and slow-bend tests of reconsti- uating mechanical tests and neutron do- tuted, precracked Charpy specimens. A prob- simetry, using state-of-the-art testing and abilistic micromechanical model has been es- calculation methodologies; tablished for static and dynamic transgranu- lar cleavage initiation fracture toughness in the • to implement the quality procedures in or- ductile-brittle transition temperature range. der to obtain EN 45 001 accreditation in 1998; This model allows to project toughness bounds • to commercialize these programmes on the for any steel embrittlement condition from the international market. corresponding CVN and static tensile properties, using a single scaling factor defined by We evaluated the Doel III/3 capsule (fluence of imposing agreement with toughness tests in 5.72 x 1019 n-cm"2) and presented the surveil- a single condition. This "toughness transfer lance report with the complete mechanical test- model" incorporates an outstanding finding: ing and dosimetry analysis. The transition- the microcleavage fracture stress is affected temperature shifts of both base metal and weld by temperature in the ductile-brittle transition

48 Reactor Safety and this influence is strongly correlated to the praised and consolidated our probabilistic mi- flow stress; this explains phenomenologically cromechanical transfer model for transgranu- both the shape of the K\Q,Ku-temperature lar initiation fracture toughness (see SCK>CEN's curves and the actual magnitude of the strain 1996 Scientific Report). rate and irradiation effects. Furthermore, CVN crack-arrest loads and fracture appearance are As regards experimental techniques in sup- also taken advantage of to estimate K]a degra- port of modelling and micromechanics, our dation. Last but not least, the CVN tensile load- 1997 efforts were directed towards mechanical temperature diagram provides substantial in- spectroscopy. Because 57Fe Mossbauer spec- formation used for the modelling of in-service troscopy could not uniquely identify differ- steel strengthening, of intergranular fracture ences in the measured parameters between as- susceptibility, and of other irradiation-induced received, thermally treated, neutron-irradiated, and ageing effects. Systematic application and neutron-irradiated annealed conditions, of this enhanced surveillance approach is ex- we decided to embark no longer on this re- pected to contribute to the improvement of search. Regretfully, one of the members of our the engineering and regulatory predictive ca- research team had to leave, bringing positron- pability, while allowing optimal use of the lim- annihilation investigations to a standstill. Be- ited inventory of available surveillance mate- cause we wish to study this field further, a new rial. This year's emphasis has been on fracture- member will strengthen our group in 1998. toughness testing and evaluation on unirradi- A feasibility study of Small-Angle X-ray Scat- ated and irradiated reference materials. The tering (SAXS) for investigating damage mecha- master-curve concept has been applied to var- nisms in RPV steels was inconclusive. ious sets of data and the results have been compared to the regulation based on the ASME The mechanical spectroscopy (internal friction) reference-curve procedure. research was furthered in two main directions: we constructed a torsion pendulum and we The enhanced surveillance technology contin- studied RPV steel from the Doel I and II reactors ues to be actively validated. An important el- under different annealing conditions before ement in this effort is the BR2/CHIVAS acceler- and after irradiation. The torsion pendulum ated irradiation and testing programme, with is now being tested and calibrated. The study already six irradiation campaigns. To modify of the Doel I and II RPV steels was conducted the relative importance of the various damage by means of an inverted torsion-pendulum ap- mechanisms in RPV steel embrittlement and to paratus at the EPFL in Switzerland. Measure- help identify and separate their contributions, ments of the ratio Q"1 of the dissipated en- we exposed reference materials to representa- ergy to the elastic energy stored in the spec- tive fluences at different irradiation tempera- imen and of the frequency F of the system tures. The main activities in 1997 were the have revealed that the technique is well-suited postirradiation testing and evaluation of the to characterize relaxation phenomena due to different reference materials. In the frame- long- or short-range dislocation-defect inter- work of an IAEA programme and a PhD work, actions. The results indicate a marked in- the CHIVAS-6 irradiation allowed us to compare crease in the yield strength of an unirradiated the fracture toughness derived from different weld specimen after a one-week thermal treat- specimen geometries. ment at 450°C, but no appreciable effect of hardening after a similar treatment at 343°C. Conceptual approach to enhanced surveillance Thermal treatment at 343°C of an irradiated Damage modelling offers a comprehensive way specimen resulted in substantial thermal age- to rationalize in-service steel strengthening ing. At 450°C, the additional hardening result- and allows one to anticipate the increase of the ing from thermal ageing was almost entirely room-temperature static tensile yield strength compensated by annealing. Because Doel RPV depending upon materials and environmen- steels have too few interstitial atoms in solid tal factors, in order to relate change in frac- solution, strain ageing does not play a major ture toughness and yield strength in a micro- part in their embrittlement processes. Fur- mechanical model. In 1997, we further ap- thermore, the internal-friction results compare

Reactor Pressure Vessel Steels 49 very well with tensile-test and impact-test reconstitution on the fracture toughness to be sults and with a three-component model for very small already with only 3 mm of virgin ma- the yield strength. In addition, they quite unex- terial. For these materials, the J?XNDT shift was pectedly led to a review of standardized meth- found to be very similar to the To shift. ods of analysis of impact-test results. Inter- nal friction has withstood four years of exten- To evaluate the master-curve approach statisti- sive scepticism. Within the framework of en- cally better, we selected two well-characterized hanced commercial surveillance, the technique and well-documented RPV steels: has contributed to a better understanding of the complex physical processes involved in RPV • the 22NiMo37 steel (plate used in the in- steel embrittlement. ternational round robin related to fracture toughness in the transition regime); Reconstitution technology The reconstitution • the A533B steel (low upper-shelf RPV steel technique was routinely applied. On one occa- tested within a Japanese round robin orga- sion, the voltage polarity of our reconstitution nized by the Japan Society for the Promo- setup was incidentally changed, causing larger tion of Science). melt-off of insert material. Verification of the consequence on fracture-toughness measure- Besides the precracked Charpy specimen, an- ments with finite-element analysis showed that other geometry, the circumferentially-cracked this should not influence the results, although round bar, was extensively investigated on larger scatter of the results was detected. We these two reference materials, with particular executed the reference testing and tempera- attention on the size effect and loss of con- ture tests within the RESQUE project. straint. The results obtained on 22NiMoCr37 after normalization to lT-size indicate that the Fracture toughness research A large ef- fracture-toughness behaviour in the transition fort was made to qualify the three-point bend regime can be characterized with small sam- technique on precracked Charpy specimens to ples if both size and constraint effects are measure fracture toughness of irradiated RPV taken into account (Fig. 1). steels. Hence, we successfully tested three materials, namely the JRQ irradiated in the Doel IV IAEA capsule, the 73W weld irradiated in the BR2/CHIVAS-0, and the Doel base from the surveillance capsule Doel H/4. A comparison between the shift of the transition curve ;:40i3.i!: and the tf TNDT shift clearly shows that the regulation is conservative (Table 1).

Table 1 Comparison between irradiation-induced shift as determined from fracture-toughness measurements and the application of the regulation based on the KTNDT shift.

Material 4>[n ATb AKTNDT

73W 3.8 X 1019 124 155 JRQ 1.2 X 1019 66 109 9 Doel base 3.6 X 101 50 77 •!"$":

We applied our methodology to the Chooz A Figure 1 Results obtained on the 22NiMoCr37 af- base metal and the Doel weld material (Doel 1/4 ter normalization to lT-size, compared to the mas- and Doel II/5), reconstituting most of the spec- ter curve (solid line) and associated 5% and 95% con- imens from 10 x 10 x 10 mm3 inserts. Finite- fidence bounds (dashed lines). The CRB specimens element analysis showed the influence of re- (hollow circles) are corrected for loss of constraint.

50 Reactor Safety Embrittlement mechanisms and micro- aged at 290°C. A quadratic superposition of the mechanics of Doel I and II pressure-vessel strengthening by the other obstacles has been welds (Phase ill) We consolidated our adopted. Parallel application of the model R&D effort on the Doel I and II pressure-vessel to the correlation monitor HSST-02 and to the weld material, which displays an outlier be- Doel forgings indicates that the mean irradia- haviour of in-service embrittlement relative tion temperature of the surveillance capsules to regulatory predictions (USNRC Guide 1.99 is closer to 3O5°C than to 290°C. Rev. 2, French Code, etc.). Using the three-point bend technique, we determined the fracture The Doel I and II forging specimens are by far toughness of Doel I and II precracked Charpy- the most sensitive ones to the irradiation tem- size baseline and irradiated samples. We also perature. This behaviour is explained by their tested specimens of the surveillance capsules relatively low copper content (0.085%) and high Doel 1/4 and Doel II/5, after applying the recon- nickel content (0.79%); for such a composition, stitution concept on small (10 x 10 x 10 mm3) the role of the damage mechanism responsi- inserts; we analysed them according to the ble for the temperature sensitivity is govern- master-curve procedure. ing. For the weld, an "effective" copper content of 0.15% has been taken, even though the Our approach regarding the strengthening and bulk content may vary from about 0.13% ("low- embrittlement of Doel I and II steels consisted copper" coupons) to about 0.4% ("high-copper" in three steps: defining steel strengthening by coupons). This choice is consistent with the means of the damage model, relating strength- extensive AEAmicrostructural characterization ening to the Ductile-Brittle Transition Temper- programme, which revealed not only that a sig- ature (DBTT) shift ("initiation" model), and re- nificant proportion of copper has been pre- lating strengthening to the Pellini drop weight precipitated by the weld heat treatment (high- (Nil Ductility Temperature or NDT) and to crack copper coupons), but also that the sizes and arrest. The results for the Doel welds, summa- number densities of the irradiation-induced rized in Figures 2 and 3, are briefly discussed Copper-Rich Precipitates (CRPs) are similar in below. all weld coupons: only the CRP composition changes (more copper in the CRPs from high- copper coupons), which does not affect the steel strengthening (see SCK'CEN's 1996 Scien- tific Report). These high-resolution observations by Field Emission Gun Scanning Trans- mission Electron Microscopy (FEGSTEM) provide a scientific rationale to explain why no copper effect was found by the CVN reconstitution of both low- and high-copper coupons. The weld is little sensitive to the irradiation temperature because of its low nickel content (0.125%). The CRP morphology and composition is probably not affected by a change of temperature from 305°C to 290°C.

Embrittlement versus strengthening: DBTT "initiation" model Literature papers generally Figure 2 In-service strengthening of Doel I and II assume that one can estimate the DBTT shift submerged arc welds (damage modelling). (as approximated by the 41J CVN shift) by mul- tiplying the RT yield strength increase AafT Damage modelling In this work (Fig. 2), by a constant of the order of 0.5 to 0.7°C- strengthening from thermal ageing (weld) has MPa"1. In practice, such ratio is neither con- been assumed to follow a time-exponent V3 stant nor unique, and can have values ranging kinetics and has been normalized to the ob- from 0.4 to 1.2. To estimate the applicable val- servations from the steam-generator capsule ues, we developed a micromechanical model

Reactor Pressure Vessel Steels 51 referring to the well-known Davidenkov dia- bound of +95°C (TA = +115°C). The median gram, which defines DBTT as the temperature NDT increase of 103°C is at least 40% lower in at which the uniaxial yield stress intersects the this case than the 41J CVN shift. These val- microcleavage fracture stress a*. Our work ues pertain to an extended end-of-life maxi- further defines DBTT as TI, the temperature at mum neutronic exposure of 5.0 x 1019 n-cm"2 which the shear fracture appearance begins to (£ > 1 MeV) at 290°C, and indicate a substantial exceed zero. We found for instance that the safety margin of 55°C. By contrast, application ratio of shift to strengthening is much lower of the current regulatory concepts to this ves- for irradiation at 150°C than for irradiation sel leaves almost no margin. at 300°C: this does not stem from different damage mechanisms at the two temperatures, but from the temperature dependence of the BR2/CHIVAS irradiations of reference mate- microcleavage fracture stress. We also found rials Well-targeted test reactor experiments that, for a same amount of strengthening, the are valuable in establishing PWR plant-specific Doel I and II welds are predicted to shift more embrittlement trend curves; in particular, they than the forgings. yield information at high neutron fluences, en- large the fracture-toughness database, and allow the assessment of the kinetics of damage Nil: ductility: temperaujret'C] mechanisms, including phenomena such as in- 100;: cubation fluences. In 1997, we evaluated part of the available irradiated reference-material specimens and compared it to baseline data. reconstituted* We also carried out new irradiations on IAEA 50: annealed • / material to evaluate fracture toughness from cylindrical specimen geometries. as received

EC R&D prog rammes We are involved in five international programmes of the EC, related to nuclear fission safety:

-50 H the development of advanced methods for :600 the evaluation of irradiation embrittlement RtiyieldI stress MPa of WER 1000/320 type (a consortium gather- ing Belgatom, EdF, Rosendorf, and Siemens Figure 3 Embrittlement of Doel I and II welds (mi- Kvvu); cromechanics correlation). • REFEREE (relation between different mea- Emhrittlement versus strengthening: crack ar- sures of exposure-induced shift in ductile- rest By contrast to initiation, there is no sim- brittle transition temperatures), which aims ple, well-established framework to model crack to obtain high-quality data on different ma- arrest. Nevertheless, an approximate rationale terials in order to compare Charpy impact has been derived and the results for the Doel shifts, dynamic fracture-toughness shifts, welds are shown in Figure 3. The NDT is de- and quasi-static fracture-toughness shifts; rived from the CVN arrest load on the basis of a • RESQUE (reconstitution techniques qualifica- physically validated and statistically grounded tion and evaluation to study ageing phe- correlation to both Pellini drop-weight tests nomena of nuclear pressure-vessel materi- and fracture-mechanics crack-arrest measure- als), which aims to qualify different recon- ments. Returning to Figure 2, one can see that stitution techniques stepwise in order to the unirradiated RT yield strength of 428MPa come to a European guideline; has increased in service up to an upper bound value of 570 MPa, while the unirradiated NDT of • MADAM (conversion table of material neu- - 30° C (identical for the drop-weight and the Fa tron damage indexation for all different Eu- master-curve method) has increased to a con- ropean reactor types), which aims to vali- servative estimate of +73°C, with a 2cr upper date better dosimetry calculations against

52 Reactor Safety measured data from dedicated reactor dosimetry benchmarks and to improve the analysis of the impact of uncertainties for Publication in 1997 specific reactors and RPV steel embrittle- P.M. A. DE BARKER, V. SLUGEN, E. DE GRAVE, E. VAN ment; WALLE, A. FABRY, "Differences between Eastern and PLAN (thematic network on "Life Manage- Western-Type Nuclear Reactor Pressure Vessel Steels ment of Industrial Plant, Components and as Probed by Mossbauer Spectroscopy," HyperSne Infrastructure"). Interactions 190:9, 11-16 (1997).

Presentations delivered in 1 997 IAEA R&D programme We are involved in R. CHAOUADI, "Fracture Toughness Measurements • the CRP-rv coordinated research programme in the Transition Regime Using Small Size Samples," on "Assuring Structural Integrity of RPVs," ASTM int. symp. on Small Specimen Test Techniques: with emphasis on the determination of frac- New Orleans, Louisiana, USA, January 13-15, 1997. ture toughness properties from small specimens to verify the master-curve approach; A. FABRY, "Characterization by Notched and Pre- cracked Charpy Tests of the In-Service Degradation a the "Round Robin Exercise on WWER 440 of Reactor Pressure Vessel Steel Fracture Toughness," RPV Weld Material Irradiation, Annealing and Re-embrittlement," which is Research ASTM int. symp. on Small Specimen Test Techniques: Agreement 9594. New Orleans, Louisiana, USA, January 13-15, 1997. A. FABRY, R. CHAOUADI, J.-L. PUZZOLANTE, J. VAN DE VELDE, "Embrittlement and Annealing of Reactor Pressure Vessel Steels; Comparison of BR3 Surveil- lance and Vessel Plates to the Surrogate Plates Repre- Scientific partners Atomic Energy Authority (AEA sentative of the Yankee Rowe Vessel," ASTM/STP 1325: Technology) — Electricite de France (EdF) — Electra- 18th int. symp., Effects of Radiation on Materials. bel — Electric Power Research Institute (EPRI) — K. ONIZAWA, E. VAN WALLE, "Round-Robin on Materials Engineering Associates Inc. (MEA) — Oak Reconstitution Critical Analysis," ASTM int. symp. Ridge National Laboratory (ORNL) — Tractebel Energy on Small Specimen Test Techniques: New Orleans, Engineering (TEE) — Kurchatov Institute — United Louisiana, USA, January 13-15, 1997. States Nuclear Regulatory Commission (USNRC) — Technical Research Centre of Finland (VTT) — M. SCIBETTA, "Fracture Toughness Derived from Yankee Atomic Electric Company — Universiteit Small Circumferentially Cracked Bars," ASTM int. Gent (UG) — Universite catholique de Louvain (UCL) — symp. on Small Specimen Test Techniques: New Rijksuniversitair Centrum Antwerpen (RUCA) Orleans, Louisiana, USA, January 13-15, 1997.

M. SCIBETTA, A.M. YAN, "Experimental and Customers Electrabel — Tractebel Energy Theoretical Determination of the h-Factor for Engineering (TEE) — Centro Tecnologico da Marinha Circumferentially-Cracked Round Bars," Fourth Bel- em Sao Paulo (CTMSP) — Electricite de France (EdF) — gian congress on Theoretical and Applied Mechanics: European Commission (EC) Belgium, May 22-23, 1997. BLG-737.

K. VAN OUYTSEL, A. FABRY, R. DE BATIST, R. SCHALLER, "Amplitude Dependent and Independent Internal Friction of Reactor Pressure Vessel Steels: Ef- fects of Neutron Irradiation and/or Thermal Ageing," Q-l: Puidoux, Zwitserland, March 19-21, 1997.

K. VAN OUYTSEL, A. FABRY, R. DE BATIST, R. SCHALLER, "An Internal-Friction Study of Reactor Pressure Vessel Steel Embrittlement," Specialists meeting on Irradiation Effects and Mitigation: Vladimir, Russia, MS, September 15-19, 1997.

Reactor Pressure Vessel Steels 53 Reports published in 1 997 L. VANDEVELDE, J. VAN DE VELDE, F. VANDERLINDEN, Th. VAN RANSBEECK, "Mesures d'activites sur des H. AIT ABDERRAHIM, P. VANMECHELEN, "International echantillons de la cuve de Chooz A," contract Neutron Field Characterisation at KORPUS Facility. KNT9096777 (August 1997). R-3195. Opportunity for Inter-Laboratory Neutron Dosimetry Calibration," SCK-CEN report (July 1997). R-3172. P. VANMECHELEN, "Neutron Dosimetry of the Surveillance Capsule Doel 0/5 (position 33713°)," R. CHAOUADI, "Fracture Toughness Analysis of the SCK-CEN report (April 1997). R-3151. Doel 1/4 Weld Material (1J2: Phase 1)," contract KNT9096 823 with TEE (April 1997). R-3169. P. VANMECHELEN, "Neutron Dosimetry of the Surveillance Capsule Doel III/3 (position 33713°)," R. CHAOUADI, "Fracture Toughness Analysis of the SCK-CEN report (October 1997). R-3205. Doel II/5 Weld Material (1J2: Phase 2)," contract KNT9096 856 with TEE (June 1997). R-3170. P. VANMECHELEN, "Neutron-Dosimetry Results at the Doel 2 Ex-Vessel Location -10° for Activation R. CHAOUADI, "Fracture Toughness Test Results Dosimeters Irradiated together with Sapphire of Irradiated RPV Steels," SCK-CEN report (under Damage Dosimeters," SCK-CEN report (May 1997). convention with Electrabel) (September 1997). R-316S. R-3201. P. VANMECHELEN, H. AIT ABDERRAHIM, "Dosimetrie R. CHAOUADI, "Fracture Toughness Test Results of neutronique retrospective de la cuve de Chooz A," the 22NiMoCr37: 0.5 T-CT Specimens at CTC," EC SCK-CEN report (December 1997). R-3215. Materials & Testing project, SCK-CEN report (May 1997). BLG-740. K. VAN OUYTSEL, "Report on the Internal Friction Measurements Carried out on BL633 Thyssen and R. CHAOUADI, A. FABRY, M. VERWERFT, J.-P. WANNIJN, RW9 NiMo (B) Weld Steel. Addendum on the Snoek E. VAN WALLE, J. VAN DE VELDE, "Analyse de la Relaxation in Steels," SCK-CEN report (October 1997). tenacite de la Virole C de la cuve du reacteur BLC-751. Chooz A," contract KNT3080 54 with EdF (March 1997). R-3159. K. VAN OUYTSEL, "Reports on the Internal Friction Measurement Periods at the Ecole Polytechnique P. D'HONDT, "93Nb (n, n')Nb-93m Measuring Method, Federate de Lausanne from 1994 to 1997," SCK-CEN Revised on Basis of the DAVIS-BESSE Intercomparison report (October 1997). BLG-752. Exercise," SCK-CEN report (March 1997). R-3152. E. VAN WALLE, R. CHAOUADI, M. SCIBETTA, J.- M. SCIBETTA, R. CHAOUADI, "Effect of Reconstitution L. PUZZOLANTE, A. FABRY, J. VAN DE VELDE, "Belgian on Fracture Toughness Measured with PCCv," Contribution on the lAEA-CRP-rv Programme on SCK-CEN report (April 1997). BLG-749. Assuring Structural Integrity of Reactor Pressure J. VAN DE VELDE, E. VAN WALLE, A. FABRY, J.- Vessels," contract KNT9096 821 OOP (October 1997). L. PUZZOLANTE, Th. VAN RANSBEECK, "Nuclear Power BLC-754. Station Doel II Pressure Vessel Steel Surveillance M. VERWERFT, "Comparative Fractography of Programme: Capsule Doel II/5," contract KNT90 96847 Soudotenax Weld: Irradiated and Irradiated-Annealed (February 1997). TEC97/50.B031057/08. Samples," contract KNT9096 773 with TEE (October J. VAN DE VELDE, E. VAN WALLE, J.-L. PUZZOLANTE, 1997). TEC97/51.B031008/40/MV. Th. VAN RANSBEECK, "Nuclear Power Station Doel III Pressure Vessel Steel Surveillance Programme: Capsule Doel III/3," contract KNT9096848 (July 1997). TEC97/50.B031058/28.

54 Reactor Safety BE9900067 Frans MOONS

Reactor Structural Materials Irradiation-Assisted Stress Corrosion Cracking

rradiation-Assisted Stress Corrosion Crack- a water chemistry at pH 6.9 to 7.4 including Scientific staff Iing (IASCC) has become a critical concern 400ppm B, 2.1 ppm Li, and 30ccSTP/kg H2, Frans MOONS 1 for LWR internals. It affects iron- and nickel- and a flux of 8 x lO^n-cnr^s" (E > lMeV). Walter BOGAERTS (KUL, based austenitic alloys, used for a wide va- We foresee to unload in autumn 1998 at an es- scientific adviser) riety of structural and nonstructural appli- timated 1.5 dpa. Postirradiation examination Rik-Wouter BOSCH cations in the core. It manifests itself as will look for the intergranular corrosion and Pascal BOYDENS intergranular cracking and differs from other radiation-induced changes in the specimen. Rachld CHAOUADI stress-corrosion-cracking phenomena by the Ludo EYSERMANS evolution of microstructure with time caused Steven MELLEMANS CORONA The CORONA (COrrosion Research by fast neutrons and by the influence of ioniz- Leonard SANNEN ONline Assembly) project aims at instrumented ing radiation on the environmental chemistry. Frans SCHELLES irradiation in a PWR loop in BR2. It aims at on- Bart SMOLDERS line crack-initiation detection on pressurized- Marc VANKEERBERGHEN Objective tube specimens (both prepressurized and ac- Jose VAN DE VELDE tively pressurized ones). The applied stress • to predict the behaviour of LWR core inter- Rudi VAN NIEUWENHOVE level is one and a half times the yield stress Marc VERWERFT nals with respect to IASCC. at 300°C. Materials are stainless steels AISI 304 Marcel WEBER (sensitized, solution-annealed) and 316 LN (ITER Programme SCK- CEN's project on corrosion, grade). Water penetration and electrochemical Supporting staff initiated in 1996, focuses on modelling IASCC noise are used to detect crack initiation. On and on developing in-pile electrochemical sen- top of proven instrumentation, that is, thermo- Willy DIERCKX sors and diagnostic equipment. The experi- couples and activation monitors, we will irra- Andre GASTMANS mental programme goes along the line of pro- diate experimental miniature gamma thermo- Guido LIEVENS totype design, laboratory tests, and in-reactor meters, in-pile hydrogen sensors, and electro- Gerard VAN ESCH tests with a growing complexity. The scientific chemical noise detectors. programme consists of experimental data review and evaluation, IASCC understanding and The design and construction of tubes, gamma modelling, development of mitigation strate- thermometers, hydrogen sensors, and electro- gies, and interpretation of sensor behaviour. chemical noise detectors are complete. We now perform laboratory tests both under ambient conditions and in a PWR loop, and plan to start CORIOLIS The CORIOLIS (COrrosion Related the irradiation in late 1998 or early 1999. Irradiation Off-line for IASCC Susceptibility) project is a neutron irradiation performed in In the same framework of developing electro- a PWR loop in the BR2 materials testing reac- chemical sensors and diagnostic equipment, tor. It aims at positioning ourselves in the in- a two-year research project recently started. ternational IASCC research and at making a link In a first stage, it investigates the suitability, with in-house knowledge on fracture mechan- for monitoring initiation and propagation of ics. It does so by (re-)establishing the know- IASCC, of electrochemical techniques such as how in IASCC experimental techniques such electrochemical impedance spectroscopy, pos- as swelling mandrels, that is, ceramics-filled sibly together with electrochemical noise and tubes: the ceramics swells under neutron irra- corrosion potential measurements. In a sec- diation, creating stresses in the tube, leading to ond stage, it will extrapolate the techniques IASCC. We irradiated stainless steel AISI 304 and for use in a nuclear environment, aiming at on- Incoloy 800HT, differing mainly in nickel con- line surveillance of IASCC under PWR conditions tent, under three forms: notched specimens (high temperature, high pressure, and neutron for crack-initiation studies, precracked spec- and gamma fluxes). imens for crack-initiation, crack-growth, and fracture-mechanics studies, and smooth tensile specimens as reference. ECLIPS Because the operating PWR loop in the BR2 reactor does not allow off-normal chem- We started the CORIOLIS irradiation in early istry conditions, we are designing ECLIPS (Ex- 1997 in the following water environment: a perimental Corrosion Loop for In-Pile Studies), pressure of 15MPa, a temperature of 300°C, a facility that will allow pressurized-water and

Irradiation-Assisted Stress Corrosion Cracking 55 fusion-reactor conditions of temperature and of VUB, we started a study of thermally sensi- pressure; pressurized-water reactor, fusion- tized SS304. When austenitic stainless steel al- reactor, and alternative (novel) water chem- loys are annealed between 600 and 750°C, they istry; loading of radioactive specimens; simul- become susceptible to intergranular corrosion. taneous exposure to coolant of samples in and This well-known phenomenon is related to out of the neutron flux; f ast (E > 1 MeV) flux up the formation of chromium carbides at grain to 4x 1014 n-cm"2 -s"1; and in-pile instrumen- boundaries and the concurrent chromium de- tation and monitoring. The commissioning of pletion of the adjacent regions. A similar the loop is scheduled for late 1999. mechanism occurs during neutron irradiation and is considered one of the phenomena leading to IASCC. Before tackling the more diffi- IASCC mitigation Alternative water chem- cult problem of irradiation-induced effects, we istries are a potential route for IASCC mitiga- started with an AES study of thermally sensi- tion in existing nuclear power plants. A re- tized material. search programme started on Zr-compound injection. In a first stage, it will perform po- The study used the same material as for the tentiodynamic experiments, in an autoclave at CORIOLIS irradiation programme. Samples were different Zr-compound concentrations and for first solution-annealed, then heat-treated for a range of pH values, on stainless steel 304, 24 hours at 621°C. To allow the study of free Incoloy 800, and Inconel 600—three materi- grain boundaries, the samples were loaded als that have an equal level of chromium, with hydrogen prior to fracturing. Hydro- while their nickel content ranges from 10 to gen embrittlement causes partial intergranular 60%. Surface composition and structures are cleavage of low-temperature fractured sam- analysed by microscopic surface analysis tech- ples. The free grain boundary facets are eas- niques such as Auger Electron Spectroscopy ily recognized in the Auger microscope when (AES), Scanning Auger Microscopy (SAM), and operated in SAM mode. We are currently in- microspot Electron Spectroscopy for Chemical vestigating the influence of the surface rough- Analysis (ESCA). In a second stage, we will per- ness on the quality of the depth profiles. The form slow strain-rate testing at distinct wa- first results indicate that this roughness may ter chemistries and under controlled electro- indeed prevent a correct evaluation. chemical conditions to correlate the protective properties of the surface layer to the resistance to stress corrosion cracking. Then, in Furthermore, in collaboration with EdF, an SCK- stage three, we will compare the stress corro- CEN trainee started validating an EdF-CEA code sion cracking behaviour of unirradiated mate- on radiation-induced segregation in austenitic rial and material irradiated in ECLIPS. Finally, stainless steels at EdF. we will incorporate the electrochemical data thus gathered into a simulation model.

The laboratory equipment for stage one has Scientific partners Katholieke Universiteit been acquired and is operational. Leuven (KUL) — Vrije Universiteit Brussel (VUB) — Laborelec Modelling A first modelling effort consisted in applying advanced neural networks to evalu- Sponsor Tractebel Energy Engineering (TEE) ate data of an international databank on IASCC. We embarked on mechanistic corrosion modelling using electrochemical software to solve simultaneously ion transport by diffusion, convection, and electromigration in an aqueous Presentation delivered in 1 997 PWR core environment. P. BOYDENS, "Analysis of Irradiation-Assisted Stress Corrosion Cracking Data by Use of Neural Networks," In co-operation with the department of Metal- Eurocorr'97: September 22-25, 1997. Proc. II, lurgy, Electrochemistry, and Materials Science 197-202.

56 Reactor Safety BE9900068 Frans MOONS

Reactor Structural Materials Fusion Reactor Materials

USION RESEARCH in Europe is co-ordinated • the four beryllium grades cannot be clearly Scientific staff Fby the European Commission (DGX1I, Fu- distinguished, except S200 VHP, which be- Philippe BENOIT sion Office). At SCK-CEN, the fusion activi- haves differently. The Hot Isostatic Pressed Rachid CHAOUADI ties focus on environmental tolerance of opto- (HIP) material shows higher strength than Louis COHEUR electronic components (see "Advanced Instru- the Vacuum Hot Pressed (VHP) one; Emelina COLINO (trainee) mentation and Teleoperation," on page 107), Pascal DEBOODT • irradiation drastically reduces the fracture materials characterization, and neutron irradi- toughness, in particular in the 400 to 500°C Frank DRUYTS ation services. Sergei GAVRILOV (secondee temperature range. In this range, unirradiated samples failed by stable crack growth from IRTM, RRC Kurchatov Institute) Objective and irradiated ones by unstable fracture. Frank JOPPEN • to contribute to the knowledge on the be- Frans MOONS haviour, during and after neutron irradia- Modelling the helium behaviour in irra- Jean-Louis PUZZOLANTE tion, of fusion-reactor materials and com- diated beryllium at atomic scale The Jose VAN DE VELDE ponents. Igarashi-Vitek-Kantha (IVK) potential, on which Pierre VAN ISEGHEM the current cohesion model is based, incor- Alfons VERSTREPEN rectly describes the vacancy migration energy Marc VERWERFT Programme Our programmes foresees and the surface energy in the case of beryllium. • to study the fracture mechanics of neutron- In close co-operation with ULB, SCK>CEN there- Supporting staff irradiated beryllium, based on tensile and fore concentrated on improving the rvK poten- Theo NOELS compact tension tests and on microstruc- tial. An analytical and an empirical approach Kris PENASSE tural evaluation; applied on three different cases gave consis- Jozef VERAGHTERT tent results. • to describe the helium behaviour in irradiated beryllium at atomic scale; In the first case, the elastic constants, the co- • to define the kinetics of beryllium reacting hesive energy, the c/a ratio, and the equilib- with air or steam; rium atomic volume are matched to experimentally measured values. However, the inhomo- • to perform a feasibility study for the testing geneous contribution to the elastic constants of integrated blanket modules under neu- vanished and the calculated vacancy migration tron irradiation. energy was still unphysically high.

Fracture mechanics of neutron-irradiated In the second case, in addition to the previous beryllium Brush Wellman, USA, fabricated constraints, consistency with the measured Ra- compact tension and tensile specimens from man frequency was imposed on the inhomo- four species of beryllium differing in both geneous contribution to the elastic constants. beryllium-oxide content and powder-consoli- Although the set of parameters for the IVK po- dation method. These specimens were irradi- tential was more realistic, the vacancy migra- ated at 200, 400, and 600°C up to neutron flu- tion energy was still too high. ences ranging from 0.8 to 2.1 x 1021n-cm~2 (E > lMeV) or 250 to 750appm helium. The In the third case, in addition to the previ- same number and kind of specimens, called ous constraints, the IVK potential function was thermal-control specimens, were aged under modified to provide a more realistic descrip- the same time-temperature profile as the irra- tion of the close atomic interactions. The first diated specimens. attempts gave reasonable results on migration energy. The tensile and fracture-toughness tests on the irradiated material lead to the following con- However, further development is required to clusions: ensure reasonable excess energies associated with extended defects and interfaces. • irradiation results in classical effects on tensile properties: loss of ductility and strengthening of the material;

Fusion Reactor Materials 57 Kinetics of beryllium reacting with air or steam We have acquired, installed in a controlled zone, and calibrated a thermo- Presentations delivered in 1997 gravimetric/differential temperature analyser R. CHAOUADI, F. MOONS, J.-L. PUZZOLANTE, "Tensile (TGA/DTA). The first tests on unirradiated and irradiated dense beryllium show linear kinetics and Fracture Toughness Test Results of Neutron at 600 and 700°C and a parabolic law at 800°C Irradiated Beryllium," Third IAEA int. workshop and above. Tests are continuing on irradiated on Beryllium Technology for Fusion: Mito, Japan, porous material and in steam at 1 bar. October 22-24, 1997. F. MOONS, R. CHAOUADI, J.-L. PUZZOLANTE, "Fracture Behaviour of Neutron Irradiated Beryllium," Fourth Integrated blanket modules under irradi- Int. Symp. on Fusion Nuclear Technology (ISFNT-4): ation Which type of tritium-breeder blanket to use in the future thermonuclear fusion Tokyo, Japan, April 6-11, 1997. reactors is still an open issue. Two concepts C.H. WU, J.P. BONAL, H. KWAST, F. MOONS, G. POTT, are currently in competition for ITER and DEMO. H. WERLE, G. VIEIDER, "EU Results of Neutron Effects The first is based on beryllium and lithium of PFC Materials," Fourth Int. Symp. on Fusion Nuclear orthosilicate pebble beds, cooled by helium. Technology (ISFNT-4): Tokyo, Japan, April 6-11, 1997. In the second, tritium is generated in liquid Proc, 161. lithium-lead, cooled by pressurized water. Fea- sibility studies are performed for the irradia- Reports published in 1997 tion of integrated blanket modules in the BR2 materials testing reactor, relevant for both con- Ph. BENOIT, "The Cepheid Project—Conceptual cepts. The study leads to a preliminary tech- and Feasibility Study," Task WP B.3.3.2, final report nical concept of the experimental facilities. It (February 1997). BLG-733. includes a budget for the whole project (con- R. CHAOUADI, F. MOONS, J.-L. PUZZOLANTE, "Tensile struction, operation, and dismantling of the fa- and Fracture Toughness Test Results of Neutron cilities in BR2) and extends until mid-1998. Irradiated Beryllium," ITER taskT23 (December 1997). BLG-757. The module should include representative seg- E. COLINO, " Beryllium Environmental Levels in ments of the actual breeding material, of the Countries of the European Union: A Case Study," neutron multiplier, and of the first wall, operated with the actual coolants at relevant pro- SEAL sub task 1.1 (March 1997). cess pressure and temperature. Such integral F. DRUYTS, P. VAN ISEGHEM, F. MOONS, L. COHEUR, experiments aim at confirming the general be- P. DEBOODT, "Interaction of Beryllium with Air/Steam: haviour of the system and, in particular, the tri- Laboratory Setup," SEAL subtask 1.1 (March 1997). tium production, release, permeation, and recovery rates in an environment as close as pos- F. MOONS, "Beryllium Validation," ITER task T23, final sible to the designed blanket operation condi- report (November 1997). BLG-767. tions. M. VERWERFT, "Irradiation Effects in Beryllium: A Comparison of Powder Types and Consolidation Techniques," ITER task T23, progress report (February !'I97). BLG-735.

Scientific partners Forschungszentrum Karlsruhe (FZK) — EC Joint Research Centre (JRC) — Commissariat a l'energie atomique (CEA) — Universite Libre de Bruxelles (ULB)

Sponsor European Commission (EC), Fusion Directorate, DGXII

58 Reactor Safety

Guy COLLARD Waste management

T k TASTE MANAGEMENT performs, interprets, ¥ ¥ improves, and develops nuclear measurements related to people and the environment in normal and emergency situations. It bases its necessary expertise on in-depth research programmes and daily experience with complex and routine measurements.

60 Radioactive Waste and Cleanup BE9900069 Luc NOYNAERT, Aime BRUGGEMAN, Andre RAHIER

Waste management Prevention and Minimization of Waste Production

THE SOUND MANAGEMENT of both radio- superheated, followed by desublimation at a Scientific staff JL active and conventional waste and of the temperature slightly above the dew point of the Johan BRAET environment starts by reducing the waste pro- steam. Aime BRUGGEMAN duction in all three phases of the life cycle of Sieglinde CATTOIR nuclear installations: design, operation, and In 1997, SCK'CEN andKralovopolska-RlA (Czech Rene CORNELISSEN decommissioning. SCK* CEN develops new pro- Republic) collaborated to develop and propose Roger HARNIE cesses and technologies to reduce the produc- a boron-recycling installation for the nuclear Sven HARNIE tion of radioactive waste. power plant of Mochovce. Luc NOYNAERT Jef MARIEN Benoit PETITFOUR Objectives The general objective of the pro- Treatment of metallic sodium Although Andre RAHIER gramme Prevention and Minimization of Waste processes for the treatment of contaminated Frans SMAERS Production is to contribute to reducing the vol- sodium coming from liquid-metal fast-breeder Veerle VAN ALSENOY umes and costs of nuclear waste. It also aims to reactors and R&D programmes already exist, provide reliable data and models to the design they are not optimized in terms of safety and engineers with a view to determining the final waste conditioning. Supporting staff plant characteristics. In the long term, these Eric AEGTEN objectives will be extended to other nuclear ap- SCK»CEN therefore developed and patented a Gerard CASTELYNS Alfons FONTEYNE plications. Medium-term objectives are dedicated, safe treatment process, fully compatible with acceptable immobilization tech- Dirk QUIRIJN • to demonstrate a process for the removal of Sally SCHRAEYEN niques. It has signed a contract with EdF, which boron from PWR waste and to purify boric Domien SMETS sponsors the research since there is a lack of acid for recycling; Eric SNOECKX safe techniques on the market. The first ver- Raf VAN AMMEL • to define and assess adequate treatment sion of the design of the fluidized-bed reactor Ronny VAN BAEL and conditioning techniques for exotic ma- has been finished and the reactor has been or- Winand VAN DEN RUL terials such as aluminium, beryllium, lead, dered. Further efforts have been made to fi- Robert VANDEVOORDE tritium, radium, and other isotopes if nec- nalize the flow sheet and to prepare the pro- essary; cess control and the preliminary safety report. Qualification tests are going on with both the • to define and assess an effective deactiva- liquid-metal spray nozzle and the gas-injector tion process to be applied to activated met- system. The pilot plant is being constructed als; in the Technology building. We intend to per- H to demonstrate and apply existing technol- form the cold feasibility demonstration test in ogy and technology developed in house to the first semester of 1998 and the hot demon- the recycling of contaminated materials; stration in 1999. • to define and assess new soil-restoration techniques. Electrodestruction of organic waste Or- ganic waste represents a problem in terms of conditioning and safety under disposal condi- Boron recovery from reactor effluents At tions. It can be destroyed by Ag2+. In the past, most PWRS, evaporation of the Low-Level Liquid we successfully elaborated a theoretical model Waste (LLLW) guarantees high decontamination describing the selectivity of the anode and de- factors and thus low releases of radioactivity. signed an adequate electrochemical cell. However, the boron concentration in these effluents limits the volume-reduction factor; In 1997, we managed to solve the difficult ques- the boron-containing evaporator concentrates tion of the analytical speciation of the electro- thus represent an important fraction of the nu- chemical mediator. For this purpose, we com- clear waste. pared extensively the determinations obtained by three methods and carried out a success- SCK«CEN therefore developed a process involv- ful statistical analysis of the results, which ap- ing the separation of boric acid from evapora- peared to be coherent. We conceived a statis- tor concentrates. This process separates and tical experimental design to finalize the mod- purifies solid boric acid by volatilization with elling of the process. Furthermore, we used a

Prevention and Minimization of Waste Production 61 pilot loop to assess the electrodestruction of tend to dismantle them in the Central Buffer methanol and observed that its efficiency in- Zone. Then, scrap metal will be decontami- creases at lower temperatures. We interpret nated and/or recycled according to its radio- this result through the difference in activation logical and geometrical characteristics. energy for the reactions of the mediator with water and with the organic species, respectively.

Sponsor Electricite de France (EdF) Decontamination of metallic pieces The cerium process, based on the use of Ce4+ as strong oxidant, was selected as chemical decontamination process for the stainless steel coming from the dismantling of the BR3 reactor. Electrodialysis experiments carried out at Publication in 1 997 pilot scale have confirmed that up to 95% of the A. BRUGGEMAN, J. BRAET, F. SMAERS, P. DE REGGE, sulphuric acid present in the effluents of the "Separation of Boric Acid from PWR Waste by cerium process can be recycled. This approach Volatilization during Evaporation," Separation proved economical, but only in the case of an Science and Technology 32:1-4, 737-757 (1997). adequate on-site conditioning of the effluents by separation of the contaminated metals from V. FEDERICI, A. BRUGGEMAN, C.P. JONES, A. SEVERO, the aqueous phase, for instance by precipita- R. ROOFTHOOFT, "Advanced Processes for the tion. Treatment of Low-Level-Liquid Waste," Proc. of the fourth conf. of the EC on the Management and Disposal of Radioactive Waste, Luxembourg, Grand Recycling of contaminated material Re- Duchy of Luxembourg, March 25-29, 1996, EUR 17543 use and recycling are more and more recog- EN, 149-164 (1997). nized as very good methods to reduce waste and costs safely during decommissioning ac- Presentations delivered in 1 997 tivities. Thirty-six tons of scrap metals coming from SCK«CEN were recycled in the SEG S. HARNIE, L. NOYNAERT, "Decommissioning a Hot melting facility in Oak Ridge (Tennessee, USA), Cell Used for Post Irradiation Research," European into shielding blocks for other nuclear pro- working group on Hot Laboratories and Remote grammes. Handling: Nykoping, Sweden, June 5-6, 1997. L. NOYNAERT, V. VAN ALSENOY, R. CORNELISSEN, An easy way to reduce waste production is to "Decommissioning Plan of a Nuclear Research Centre: sort scrap material as a function of the avail- Practical Experience," Fifth Int. Conf. On Nuclear able reuse, recycle, and decontamination pro- Engineering (ICONE 5): Nice, France, May 26-30, 1997. cesses. A building, called the Central Buffer Proc, 2252. Zone, was specially designed to perform these A. RAHIER, M. KLEIN, M. PONNET, "Theoretical and activities at SCK-CEN. It will become operational in early 1998. By sorting the remaining Experimental Study of the Selective Oxidation of waste, we intend also to enhance the filling fac- the Cerous Ion on a Pt-Ti Anode in Sulphuric Acid tor of the waste drums. Solutions," Symp. on Electrochemical Processing (ICI): Barcelona, Spain, April 14-18, 1997.

Based on the results obtained with the decom- A. RAHIER, M. KLEIN, M. PONNET, "Regeneration missioning of hot cell #10 in the Laboratory de l'ion cerique en milieu sulfurique," Journees for High- and Medium-level Activity (LHMA), we d'Electrochimie 1997: Polytechnic Institute of are convinced that on-site decommissioning of Montreal, Montreal, Quebec, Canada, July 2-5, 1997. glove boxes and cells after a first decontamina- Proc., H3C 3A7, C04-3. tion is very promising in terms of safety and of waste and costs minimization. Up to now, we have only carried out the first decontamination of three glove boxes and two hot cells. We in-

62 Radioactive Waste and Cleanup Theses published in 1997 Reports published in 1997

V. BARBU, "Mise au point d'une méthode de dosage J. BRAET, A. BRUGGEMAN, J. VANWILDEMEERSCH, de l'aluminium en milieu aqueux par polarographie," "Boron Recovery from PWR Waste by Volatilisation final-year thesis (Ecole Nationale Supérieure de during Evaporation in the Mochovce NPP, Slovak Chimie de Rennes), August 1997. Republic," contract KNT9096852 (June 1997). R-3187.

L. BOSSART, "Mesure polarographique du cobalt M. BRUGGEMAN, S. BODEN, R. HARNIE, "Afval- dans les aciers inoxydables," final-year project, karakteriserings-methoden voor de afvalstromen Industrial Engineering (Institut Supérieur Industriel SCHXXX-N van het SCK-CEN," SCK-CEN report (1997). de Bruxelles), June 1997. R-3108.

A. CAMPSTEYN, "Dosage de l'aluminium par polaro- A. BRUGGEMAN, C. JONES, R. ROOFTHOOFT, A. SEVERO, graphie," final-year project, Laboratory Assistant "Advanced Processes for the Treatment of Low- (ISET), June 1997. Level-Liquid Wastes at a Pilot Plant Scale" (1997). EUR 17446 EN. S. DRIESEN, "De veilige behandeling van tri- tiumhoudende methanol," final-year project, S. CATTOIR, "De recuperarte van zwavelzuur Industrial Engineering in Chemistry (Katholieke uit gecontamineerde oplossingen door elektro- Hogeschool Limburg, Hasselt), June 1997. elektrodialyse," SCK-CEN report (May 1997). BLG-744.

G. GRAMS, "Détermination analytique de l'espèce M. LECLERCQ, "Dosage du médiateur argentique en AgONOj et étude cinétique de l'oxydation contrôlée milieu nitrique par voltamétrie cyclique," trainee du méthanol, du graphite et des résines," final-year report, Université de Liège (September 1997). project, Laboratory Assistant (ISET), June 1997. B. PETITFOUR, "Déconvolution de pics polaro- S. MARQUES, "Conception et étude du système graphiques par régression multiparamétrique," Ecole d'injection des réactifs gazeux utilisés pour oxyder Nationale Supérieure de Chimie de Rennes (August le sodium métallique contaminé," final-year thesis 1996). BLG-742. (Ecole Nationale Supérieure de Chimie de Rennes), B. PETITFOUR, "Etude des conditions idéales de August 1997. vitrification de déchets sodés après oxydation sur lit S. SAUVAGE, "Récupération de l'acide sulfurique fluidisé," Ecole Nationale Supérieure de Chimie de issu de la décontamination des pièces métalliques Rennes (August 1997). BLG-759. par électro-électrodialyse," final-year project, V. VAN ALSENOY, "Analytical Determination of Ag++," Industrial Engineering (Institut Supérieur Industriel SCK'CEN report (January 1997). BLG-730. de Bruxelles), June 1997.

F. VAN PETEGEM, "Ontmanteling van de BR2- Patent applied for in 1 997 reactorkuip," final-year project, Industrial Engi- A. RAHIER, V. VAN ALSENOY, "Procédé d'oxydation neering in Nuclear Sciences (Katholieke Hogeschool d'au moins un métal alcalin," Belgian patent Limburg, Hasselt), June 1997. application #9700039 of January 15, 1997, in the name of SCK> CEN. Lecture taught in 1997

A. RAHIER, "La gestion d'un projet de recherche en technologie nucléaire," Course given at the Institut des Hautes Etudes Commerciales: Liège, Belgium, April 24, 1997.

Prevention and Minimization of Waste Production 63 BE9900070 Leon VANDEVELDE, Roland CARCHON

Waste management Early Identification and Characterization of Waste

Scientific staff THOROUGH KNOWLEDGE of the waste pro- We further developed suitable separation and 99 129 241 Peter DE REGGE >.duced is of primary importance for both measurement techniques for Tc, I, Am, 242 244 Leon VANDEVELDE an optimized predisposal management of ra- Cm, and Cm and investigated several pu- 99 Mireille GYSEMANS dioactive waste and the quantification of the rification methods for low amounts of Tc Frank VANDERLINDEN source term of future repositories. To this in complex matrices. Solvent extraction us- Freddy VERREZEN end, SCK«CEN develops destructive and non- ing tri-n-octylamine in xylene yielded the most Peter BAETEN destructive analytical techniques, and correla- promising results. The presence of an exces- 106 Michel BRUGGEMAN tion models based on key isotopes. sive amount of Ru, however, interferes with Roland CARCHON the measurements, even with additional purifi- Wim DE BOECK cation steps. Objectives The programme aims to mea- Robert MANDOKI sure the inventory of critical and key nuclides Klaas VAN DER MEER The method previously developed to separate in different waste streams and to identify and 129I is not suited to determining concentra- develop correlations between those isotopes. Supporting staff tions below 5 Bq per ml of solution. At higher 129 Maureen GROMMEN concentrations, the I can be measured by Magda OOMS Determination of the disposal-critical nu- gamma spectrometry and the separation yield 129 Jozef GERITS clides in waste from PWR power plants can be monitored with an I tracer. For Nadine VERSTRAELEN The presence of long-lived nuclides poses a very low concentrations, however, the amount major safety problem for the long-term stor- of 129I is insufficient for gamma spectrome- age of radioactive waste. Unfortunately, their try and the salt content of the sample impedes low content, their low specific activity, or the neutron activation analysis. particular characteristics of their radiation currently make them difficult to measure because Destructive measurements of alpha emit- of the presence of other highly active nuclides. ters in radioactive waste The alpha- Advanced separation techniques are therefore emitters content of radioactive waste is preva- necessary to allow their immediate determina- lent for its classification. However, the deter- tion without interferences. mination of trace amounts of alpha emitters in strong beta- and gamma-emitting waste is The critical nuclides are produced in nuclear subject to interferences. A standard proce- reactors either by activation (3H, 14C, 39Ni, dure for their measurement needed therefore 63Ni, 94Nb) or by fission and transmutation to be set up to allow one to define a reference (90Sr, "Tc, 129I, 133Cs, 234U, 233U, 236U, 238U, 239p 240p 241 ^ 242 244 _ . level for a possible declassification. This pro- Ui U| Cm> Cm) Their con cedure includes a dissolution method for dif- centration may be correlated to so-called key ferent types of conditioned and unconditioned nuclides, presently measurable with a good ac- waste forms, separation techniques to isolate curacy and representative for activation (60Co) 137 the alpha-emitting isotopes, and the choice of or fission ( Cs) reactions. We determined the suitably sensitive measurement techniques. scaling factors for most of the critical nuclides with respect to the key nuclides in evaporator Within the framework of Working Group 5 concentrates, ion-exchange resins, and coolant on Chemical and Radiochemical Destructive particle filters from the power plants of Doel Analysis of the EC, we started an international and Tihange. programme, together with laboratories from Germany, Italy, Spain, and the United Kingdom, In 1997, we also focused our efforts on devel- to set up a standard procedure for measuring oping a more efficient dissolution technique, traces of alpha emitters. We ordered a new al- based on microwave digestion. We developed pha spectrometer with increased sensitivity to suitable dissolution schemes for resins, ce- measure the expected low activities and should ment, and incinerator ashes, leading to clear receive it in early 1998. solutions in a minimized volume. The resulting matrix, simpler than in the fusion- dissolution method, simplifies the further use of separation techniques.

64 Radioactive Waste and Cleanup Modelling and development of gamma and Figure 1 Relative ;Relativejdeviatibh;i neutron assay techniques Passive neutron deviation (Pumeasured - coincidence counting for the nondestructive PUdeclared)/PUdeclared as Foam assay of fissile material or plutonium-bearing measured with the TIA waste is commonly performed using the shift- method for the foam, i : : : register technique, which allows one to count CO sand, and iron matrices. the real coincident neutrons emitted by the I The (1 - a) error flags spontaneously fissioning plutonium isotopes. show the reported To determine the plutonium content in a waste uncertainty. drum with the shift-register technique, the detection efficiency of the neutron counter with Sand its sample must be known. This efficiency can however vary from waste drum to waste • ;6.'b;; drum because of unknown neutron interac- iI I T I I tions in the waste, and is generally unknown. To determine the actual neutron detection efficiency for each measurement, we therefore developed the Time Interval Analysis (TIA) tech- Iron - nique, which allows absolute neutron assays. -0.0:: — Neutron measurements are however subject 11 to important biases such as the neutron die- away process, the dead-time effects, and the I I 1)1 I cosmic spallation. These effects were extensively studied and appropriate correction algo- .:"•:: :::-::.-'i'Sensors.:"":—••:- rithms were developed and incorporated in the TIA technique. To validate this technique, we performed measurements with our "hexagon" We also contribute to an EC project on the op- neutron counter, which contains 60 3He detec- timization of neutron assay of waste. One of tors embedded in polyethylene. The measure- the objectives of this project is to quantify bet- ments (Fig. 1) proved that TIA is an unbiased ter the localized neutron activity in a 220-litre measurement technique for plutonium masses waste drum using nondestructive techniques. 240 as low as 100 mg Pueff. For high-count-rate We therefore developed a model and the nec- applications, Monte Carlo simulations showed essary numerical tools to determine the actual that TLA has not only a more accurate dead-time location of a neutron point source in a waste correction, but also a better statistical preci- drum with an accuracy better than 10%. This sion than competing techniques. model uses the individual count rates of the detectors of the neutron counter to derive the Numerical simulation is an important tool for angular and radial position of the point source. developing nondestructive techniques and sys- When the neutron activity is not a point source tems and predicting the systems' response. To but has a finite volume distribution, the model broaden our knowledge in this field, we par- finds the center of gravity of the localized activ- ticipated in the ESARDA Reals Prediction Bench- ity with an accuracy generally better than 15%. mark Exercise. This exercise aims at predict- It allows accurate quantification of the pluto- ing the real neutron coincidence count rate for nium content of a waste drum regardless of its a fresh PWR fuel assembly placed in a neutron distribution. coincidence collar. We developed a model and working procedure to predict this count rate on For another EC project, on the optimization the basis of parameter estimates obtained from of gamma assay of waste, we are develop- simulations with the Monte Carlo code MCNP. ing a fast and user-friendly computer code, This model describes the different origins of called SOLIDANG, to calculate relative system neutron correlation and the time and spatial responses of gamma waste assay systems. In aspects of neutron multiplication in the fuel. particular, this code calculates gamma-attenu-

Early Identification and Characterization of Waste 65 ation correction factors as a function of differ- As a routine activity, we continued to assay ent sample-related parameters (waste matrix waste drums of SCK-CEN for waste manage- density, composition and distribution, shield- ment purposes in an overall site restoration ef- ing layers, activity distribution). The beta ver- fort, and measured more than 60 waste pack- sion of the code has been released among the ages on request of external clients. project partners, to be tested and validated.

Measurements and validation of waste assay techniques Following the principles m of sound quality assurance for nondestruc- Scientific partners Belgonucleaire (BN) — tive measurements concerning gamma spec- Belgoprocess (BP) — Euratom — European Com- troscopy by both the segmented gamma scan- mission (EC) — Franco-beige de fabrication de ner and the low-level waste assay system Q2 combustibles International (FBFC Int.) — Interna- on 220-litre waste drums, we established work- tional Atomic Energy Agency (IAEA) — Nationale ing procedures and participated in two inter- Instelling voor Radioactief Afval en Verrijkte Splijt- national interlaboratory tests. The first, orga- stoffen/Organisme national des dechets radioactifs et des matieres fissiles enrichies (NIRAS/ONDRAF) nized within the ESARDA Nondestructive Assay working group, dealt with the determination of the uranium enrichment of UO2 samples via gamma spectroscopy. The other is organized within an EC project on the assay of 220-litre waste drums using neutron and gamma assay Publication in 1 997 systems. We already measured eight drums P. BAETEN, M. BRUGGEMAN, R. CARCHON, "Single- and and expect to measure eight more and evalu- Multi-Deadtime Parameter Corrections of One- and ate the results by the end of 1998. Two-Dimensional Rossi-Alpha Distributions for Time Interval Analysis in Neutron Coincidence Counting," Working procedures and analysis software are Nuclear Instruments and Methods A 390, 345 (1997). continuously revised and improved to attain the highest accuracy and confidence. Upgrad- Presentations delivered in 1 997 ing of the equipment is ongoing. P. BAETEN, M. BRUGGEMAN, R. CARCHON, "Consider- ations on the Neutron Die-Away Time and Counting The decommissioning of nuclear installations Losses due to Dead Time Effects in Neutron Assay of produces huge amounts of waste. In view of Fissile Material," 19th Annual symp. on Safeguards its high disposal costs and because of environ- and Nuclear Material Management: Montpellier, mental concerns, the waste that is apt for free France, May 13-15, 1997. Proc, EUR 17665 EN, release is carefully selected, possibly after ra- 473-481. diological decontamination of the surface. The way to decide finally on commitment with free- M. BRUGGEMAN, P. BAETEN, W. DE BOECK, R. CAR- release criteria that come essentially from in- CHON, "Computed Neutron Coincidence Counting ternational consensus is by a nondestructive Applied to Passive Waste Assay," Fifth Nondestruc- assay of the items under consideration. In re- tive Assay and Nondestructive Examination Waste lation to the decommissioning of the BR3 re- Characterization conf.: Salt Lake City, Utah, USA, actor, several devices have been examined for January 14-16, 1997. Proc, CONF-951091, 137-151. their performance, precision, accuracy, detection limits, and measurement time. Several de- M. BRUGGEMAN, P. BAETEN, W. DE BOECK, R. CAR- tector types were investigated such as a ger- CHON, "Computed Neutron Coincidence Counting manium detector and Nal(Tl) scintillators, that Applied to Passive Waste Assay," 19th Annual were used to perform nondestructive measure- symp. on Safeguards and Nuclear Material Manage- ments on waste items from the dismantling opment: Montpellier, France, May 13-15, 1997. Proc., erations. Data analysis is in progress, as well EUR 17665 EN, 531-536. as an evaluation of how these measurements P. DE REGGE, F. VANDERLINDEN, R. BODEN, F. VER- can support the free-release criteria. REZEN, R. GENS, "Measurements and Correlations of

66 Radioactive Waste and Cleanup Disposal Critical Nuclides in Belgian Nuclear Power Th. BUCHERL, K. KREBS, Ch. LlERSE, C. VlCINI, Plant Low-Level Waste," Waste Management'97 HLW, G. GROSSI, A. LYOUSSI, A. MARIANI, J. P. COULON, LLW, Mixed Wastes and Environmental Restoration: J. ROMEYER DHERBEY, P. FlLSS, G. CASPARI, S. GULD- Working towards a Cleaner Environment: March 2-6, BAKKE, H. KLEIN, P. BAETEN, M. BRUGGEMAN, R. CAR- 1997, Tucson, Arizona, USA. CHON, F.V. FRAZZOLI, R. REMETTI, "Improvement of Passive and Active Neutron Assay Techniques for K. VAN DER MEER, R. CARCHON, "A Safeguards the Characterisation of Radioactive Waste Packages," Approach for a Closed Geological Repository for annual progress report 1996 (1997). Technische Spent Fuel," IAEA symp. on International Safeguards: Universitat Munchen, Institut fur Radiochemie, RCM Vienna, Austria, October 13-17, 1997. Proc, 00197. See also EUR 17852 EN, p. 277. IAEA-SM-351/102. Th. BUCHERL, K. KREBS, Ch. LlERSE, T. NEUKEL, Reports published in 1 997 C. VICINI, G. GROSSI, P. FILSS, G. CASPARI, J. KUHNE, S. GULDBAKKE, H. KLEIN, P. BAETEN, M. BRUGGEMAN, P. BAETEN, M. BRUGGEMAN, R. CARCHON, "An R. CARCHON, F.V. FRAZZOLI, R. REMETTI, A. LYOUSSI, Investigation of the Neutron Die-Away Time in A. MARIANI, J. P. COULON, "Improvement of Passive Passive Neutron Waste Assay Systems," SCK-CEN and Active Neutron Assay Techniques for the report (1997). BLG-732. Characterisation of Radioactive Waste Packages," P. BAETEN, M. BRUGGEMAN, R. CARCHON, "Localisation third progress report, period covered (1997). of Neutron Point-Sources in Waste Packages," Technische Universitat Munchen, Institut fur EC contract FI4W-CT95-0011, annual progress report Radiochemie, RCM 00997. 1996 (1997). R-3146. R. CARCHON, "Belgian Support Programme to the IAEA M. BRUGGEMAN, "Solidang 2.0: Software User's for Safeguards Implementation," progress report, Manual," SCK'CEN report (1997). R-3207. March 1995-March 1997 (1997). R-3153.

M. BRUGGEMAN, P. BAETEN, R. CARCHON, "Bench- R. CARCHON, P. BAETEN, M. BRUGGEMAN, W.P. VOOR- mark Exercise for Reals Prediction: Layout of the BRAAK, W.E. FREUDENREICH, C.P. DEURWAARDER, Algorithms," SCK'CEN report (1997). R-3129. P. HOLKAMP, "Feasibility Study on the Detection and Monitoring Systems and Procedures to Prevent Illicit M. BRUGGEMAN, R. CARCHON, W. DE BOECK, Trafficking of Radioactive and Fissile Materials at Sea P. BAETEN, "Uranium Enrichment Measurements Ports in EU Member States," SCK'CEN report (1997). with a Coaxial Ge-Detector," SCK'CEN report (1997). R-3211. R-3161. R. CARCHON, M. BRUGGEMAN, P. BAETEN, "Neutro- M. BRUGGEMAN, J. GERITS, R. CARCHON, J. CRUSTIN, nencoincidentie metingen op MOX-stalen," SCK- CEN W. DEN HOND, "Bepaling van de a-activiteit in 20 1 report (1997). R-3168. afval," SCK'CEN report (1997). R-3161. H. J. SANDEN, M. BRUGGEMAN, Th. BUCHERL, G. PINA, M. BRUGGEMAN, J. GERITS, R. CARCHON, J. CRUSTIN, "Optimization of Gamma-Assay Techniques for the W. DEN HOND, "Bepaling van de a-activiteit in Quality Checking of Radioactive Waste Packages," 20 1 afvaleenheden met de Q} voor selectie van EC contract FI4W-CT96-0036, first progress report de afvalklasse A2X of A3X," SCK'CEN report (1997). (July 23, 1997). Forschungszentrum Julich. R-3214. L. P. M. VAN VELZEN, J. BLOEM, J. DELEPINE, B. CHA- Th. BUCHERL, K. KREBS, Ch. LlERSE, C. VlCINI, BALIER, G. BRUNEL, A. MORALES, G. PlNA, G. BAR- G. GROSSI, A. LYOUSSI, A. MARIANI, J. P. COULON, DONE, B. PEDERSEN, H.J. SANDEN, P. FILSS, R. ODOJ, J. ROMEYER DHERBEY, P. FlLSS, G. CASPARI, S. GULD- Th. BUCHERL, Ch. LlERSE, P. VAN ISEGHEM, P. BAETEN, BAKKE, H. KLEIN, P. BAETEN, M. BRUGGEMAN, M. BRUGGEMAN, A. LEWIS, S. DAISH, J. P. HENDRIX, R. CARCHON, F.V. FRAZZOLI, R. REMETTI, "Im- J. BOTTE, "Round Robin Test for Non Destructive provement of Passive and Active Neutron Assay Assays of 200 Litres Radioactive Waste Packages," Techniques for the Characterisation of Radioactive contract KEMA 41281-NUC 97-5096, annual progress Waste Packages," first six-month progress report report 1996 (1997). See also EUR 17852 EN, p. 269. 1996 (1997). Technische Universitat Munchen, Institut fur Radiochemie.

Early Identification and Characterization of Waste 67 BE9900071 Luc NOYNAERT, Roger HARNIE

Waste management Tools for Waste Management and Decommissioning

Scientific staff CK-CEN is optimizing its multientry model Rene CORNELISSEN S for computing the decommissioning costs. Roger HARNIE This model uses an interactive database cover- Luc NOYNAERT ing the physical and radiological inventory of nuclear installations, available decommission- Supporting staff ing techniques, operational unit costs deduced Ronny VAN BAEL from own experience and external projects, Winand VAN DEN RUL costs of further management of waste, etc. Like the previous release, the current model allows us to simulate different decommissioning strategies, with special attention to the waste produced and the operation costs. It intro- duces the waste and decommissioning aspects in the design and the choice of new processes, equipment, and infrastructure.

With the previous release of our model, we have already evaluated the decommissioning strategies and costs of SCK-CEN'S nuclear installations, including the BR3 reactor, and of the Tihange 2 reactor. We intend to use the new version to actualize SCK- CEN's decommissioning plan by the year 2000.

The database containing the physical and radiological inventory of SCK- CEN's nuclear installations is used to set up a priority list of the waste problems. This list helps decide which R&D programmes to launch.

Presentations delivered in 1997

L. NOYNAERT, R. HARNIE, "The Management of Waste in a Nuclear Research Centre": Mol, Belgium, December 5, 1997.

L. NOYNAERT, V. VAN ALSENOY, R. CORNELISSEN, S. HARNIE, "Decommissioning Plan of a Nuclear Research Centre: Lessons Learned by the SCK'CEN," Waste Management'97 HLW, LLW, Mixed Wastes and Environmental Restoration: Working towards a Cleaner Environment: Tucson, Arizona, USA, March 2-6, 1997.

Report published in 1997

R. HARNIE, "Het beheer van radioactief afval in een nucleair onderzoekscentrum" (1997). BLG-760.

68 Radioactive Waste and Cleanup BE9900072

Vincent MASSAUT, Michel KLEIN Decommissioning of the BR3 PWR

PART OF the cleanup and restoration of Programme Through the BR3 decommis- Scientific staff ^previously contaminated sites and prem- sioning project, aiming at a complete cleanup Jerome DADOUMONT ises, the Decommissioning and Decontamina- of the site of the first European PWR plant, Yves DEMEULEMEESTER tion (D&D) activities aim at declassifying instal- SCK«CEN develops the necessary tools, tech- Roger HENDERIX lations formerly devoted to industrial or sci- niques, and methods of D&D and builds impor- Michel KLEIN entific production (such as power plants, fuel tant know-how in this domain. These devel- Robert MANDOKI fabrication plants, waste conditioning plants, opments and know-how are then made avail- Vincent MASSAUT and research installations) and having used ra- able to the industry, to perform the actual large Sven MOERS dioactive isotopes or contained sufficient ra- projects using the best up-to-date methods and Charles PLATEAU dioactivity to be submitted to regular controls. knowing their cost. This collaboration with the Mathieu PONNET Nowadays, there are about 400 nuclear power industry is mainly carried out through partner- Jan SWINNEN plants and as many research or pilot reactors ships or actual industrial projects. Moreover, Pierre VALENDUC in the world, as well as many nuclear industries the experience thus accumulated and the skills Jean-Marc BROSSARD and laboratories. Many of them are already thus developed are also useful for the regula- (Framatome) shut down or will be within a few years. The re- tory bodies and international or national insti- Alain LEFEBVRE (Belgatom) quired technologies and procedures must now tutions in charge of defining the limits of and be developed and optimized to be ready for de- constraints on the future activities in this field. Supporting staff commissioning these installations. Christian BEAUFILS Paul DE CRAECKER SCK«CEN has three main nuclear reactors, of Achievements The main achievements for Guy DIELS which BR3, a pilot PWR, was the only one to 1997 can be classified in three fields: Danny GEERINCKX produce electricity. After 25 years of suc- Bart GILISSEN • the pilot dismantling project, which mainly cessful operation, this reactor was definitively Anja HAESEN focuses on developing and testing tools shut down in June 1987. In 1989, it was Victor HELSEN and methods for the D&D of nuclear power selected by the EC as one of its four pilot Henri-Rose MEYNEN plants and installations; projects in the framework of its five-year Re- Roger MOELANS search and Technological Development pro- • the management and minimization of the Roger NIJS gramme on the decommissioning of nuclear in- generated D&D waste; Jan NUYTS stallations. This contract was renewed in 1996, Joannes POUDERS * the valorization of the accumulated expe- with two German partners: EWN-Greifswald Jan RUTS rience through contracts with international and KRB-Gundremmingen. Wilfried SMOLDERS institutions and industrial partners. Jean VANHEES Within the BR3 decommissioning project, we Jef VAN HOOF Objectives The main objective of the de- Rene VAN SWEEVELT reached the following six goals. commissioning programme is to contribute to Tom VERNELEN the activities needed to hand down a clean and • We dismantled the auxiliary equipments Vera VERSTRAELEN safe world to the next generations, in the most and loops, applying the ALARA principle to Roger WEYTJENS economical way. More specifically, this pro- all levels of the activity, and optimized the Ben WUYTS gramme aims to develop, test, and optimize methods used to minimize the production the required technologies and procedures for of waste (Fig. 1). the D&D of nuclear installations, in order to minimize the corresponding waste and the dis- Figure 1 The tributed doses. It also aims to minimize the technique selected to environmental impact of those activities. dismantle this internally contaminated auxiliary From the economical point of view, the op- loop ensures a low timization of the developed techniques and contamination of the methods aims at reducing the cost of the end- working area. of-life of the installation, but the ability to estimate precisely the actual cost of D&D is also an important factor for the acceptability of nuclear energy and for ensuring that enough money is available for the required cleanup.

Decommissioning of the BR3 PWR 69 Figure 2 This of the dismantled materials, thus drastically re- Health Physics worker ducing the generated waste. carries out the last measurement before the During the year 1997, some 200 tons of mate- free release of the rial were free-released thanks to the manage- concrete antimissile ment put in place, the sorting, measurements, slabs, to ensure an and decontamination using simple washing f trj^mr ^^^^^^P JHHHWii* independent measure. techniques or the wet abrasive blasting process for metals and the scabbling for concrete.

To ensure as good as possible a management of the waste and material stream and present a constant level of confidence, we are implementing a quality-assurance system for the whole dismantling process and for the mate- w We decontaminated, up to their free release, rial stream management. the concrete antimissile slabs used above the reactor pool (Fig. 2). Finally, to valorize the acquired experience and skills outside of SCK-CEN, we started or car- • We modelled the radiology of the primary- ried out different contracts and collaboration loop area in the plant container to simulate with international organizations and industrial the future dismantling operations and to partners. After commercial contracts in 1996 minimize the dose uptake by selecting the for D&D data and the estimations of decommis- most appropriate procedure and disman- sioning costs with Japanese and Belgian indus- tling plan. tries, 1997 saw the signature of a framework • We started to implement the quality-assur- contract with a large French industrial partner, ance procedure for dismantling loops and Framatome, in the field of D&D and radioactive equipments and for managing the waste. waste management. At the end of the year, a contract for the study of a decommission- • We compared thoroughly two methods for ing plan and management in five countries of dismantling the reactor pressure vessel ei- Central Europe was awarded by the EC to SCK- ther in situ or by removing it into the re- CEN and to other Belgian and European indus- fuelling pool and dismantling it afterwards. trial partners. We also carried out a study for We finally selected the latter as it includes decontaminating hot cells for a Belgian indus- far less technical uncertainty and allows us try and contacted a research institution to esti- to reuse existing tools as much as possible, mate the cost of the D&D of a research reactor. for instance during the dismantling of the reactor internals, and thus turned out to be much cheaper than the in situ method. De- tailed design and ordering of the main com- '> i ponents were already started. Scientific partners Belgatom — Framatome — • We began to remove the contaminated ther- Studsvik Radwaste — Belgoprocess (BP) — En- mal insulation of the primary loop contain- ergiewerk Nord GmbH (EWN) — KRB-A Kraftwerk — ing asbestos. The area should be declared Wetenschappelijk en Technisch Centrum voor het asbestos-free in early 1998. Bouwbedrijf/Centre scientifique et technique pour la construction (WTCB/CSTC) — University of Han- As regards the management of the generated nover — International Atomic Energy Agency (IAEA) D&D waste, we completed the detailed design of the chemical decontamination unit based on Sponsor European Commission (EC), DGXII and 4+ the Ce process and ordered the main compo- DGXI nents. This unit, based on the regeneration of 4+ the Ce for minimizing the secondary waste Customers Sumitomo — Institut des radioele- produced, will allow the free release of much ments (IRE)

70 Radioactive Waste and Cleanup Lectures taught in 1997

V. MASSAUT, M. KLEIN, "Research and Development Publication in 1997 in Decontamination and Dismantling Technology: Y. DEMEULEMEESTER, "Kernreactor ontmantelen," The Belgian Approach (Lecture 6.2)," IAEA Regional Natuuren Techniek jg.65, 5 (1997). Training Course on Decommissioning of Research Re- actors and Other Small Nuclear Facilities: Bucharest, Presentations delivered in 1997 Romania, June 9-20, 1997.

J. DADOUMONT, V. MASSAUT, "Comparison of Cutting V. MASSAUT, M. KLEIN, "Organization, Staffing and Techniques in the BR3 PWR Decommissioning Project," Training Requirements in the Decommissioning Seventh Int. Conf. on Cutting Technology (ICCT 7): of Research Reactors (Lecture 11.1)," IAEA Regional Hamburg, Germany, March 5-6, 1997. Training Course on Decommissioning of Research Re- actors and Other Small Nuclear Facilities: Bucharest, Y. DEMEULEMEESTER, V. MASSAUT, A. LEFEBVRE, Romania, June 9-20, 1997. "The Use of Mechanical Cutting Techniques in the Decommissioning of Highly Radioactive Reactor V. MASSAUT, L. NOYNAERT, R. CORNELISSEN, Internals," Fifth Int. Conf. On Nuclear Engineering J. MARIEN, S. HARNIE, "Decommissioning of Nuclear (ICONE 5): Nice, France, May 26-30, 1997. Laboratories and Other Facilities Supporting Op- eration of Research Reactors (Lecture 13.1)," IAEA Y. DEMEULEMEESTER, R. MANDOKI, M. KLEIN, Regional Training Course on Decommissioning of V. MASSAUT, S. MOERS, "The Management of the Research Reactors and Other Small Nuclear Facilities: Material Flow by the Dismantling of a Nuclear Bucharest, Romania, June 9-20, 1997. Reactor: Approach and Experience Gained during the Dismantling of the BR3 Pilot Dismantling Project," M. SCHRAUBEN, V. MASSAUT, "DES en genie nucleaire: Third European seminar on Melting and Recycling Declassement des installations nucleaires. le partie: of Metallic Materials Decommissioning: Nykoping, Principes et strategies (trois chapitres)": SCK«CEN, Sweden, June 11-13, 1997. Mol, Belgium, April 24-25, 1997.

V. MASSAUT, "Lessons Learned during the BR3 Expert Group contributions made in 1 997 European Pilot Decommissioning Project," Fifth int. conf. on Decommissioning of Nuclear Facilities: V. MASSAUT, "BR3 Decommissioning Project," report London, United Kingdom, February 19-21, 1997. to the TAG 22 (OECD/NEA) (November 1996-May 1997). 55Bis/97-04. V. MASSAUT, "The BR3 Decommissioning: Experience Gained and Lessons Learned," The BR3 PWR Decom- M. KLEIN, V. MASSAUT, "Dismantling Technologies in missioning Project, Ontmanteling van Kerncentrales: Decommissioning of the BR3 Reactor," IAEA experts Den Haag, The Netherlands, October 8, 1997. meeting on regional technical co-operation project on Planning and Management of Decommissioning V. MASSAUT, J. DADOUMONT, "The BR3 Decommis- for WWER NPP's Workshop: Bratislava, Slovakia, May sioning Project: A Pilot for Submarine Reactors. Risk 12-16, 1997. Prevention Approach and Lessons Drawn, Analysis of Risks Associated with Nuclear Submarine Decommis- M. KLEIN, V. MASSAUT, Y. DEMEULEMEESTER, sioning, Dismantling and Disposal," NATO advanced "Organizational Aspects of the BR3 Decommissioning, research workshop: Moscow, Russia, MS, November with a Focus on Waste Management," (same as above): 24-26, 1997. Bratislava, Slovakia, May 12-16, 1997.

V. MASSAUT, P. DEBOODT, F. VERMEERSCH, A. LEFEB- Reports published in 1997 VRE, M. KLEIN, "Optimization and Decommissioning: Challenge and Limits," First European ALARA network V. MASSAUT, M. KLEIN, "Evaluation de l'estimation de workshop, ALARA & Decommissioning: INSTN Saclay, couts de declassement de la Centrale Tihange 2 par France, December 1-3, 1997. NIS," contract KNT9096890 (1997). 38/96-12, R-3158.

V. MASSAUT, M. KLEIN, A. LEFEBVRE, "The BR3 PWR V. MASSAUT, D. MARTIN, H. STEINER, "RPV and Pilot Decommissioning Project: First PWR Dismantled Internals Dismantling Project (BR3-EWN-KRB-A)," EC in Europe," Int. conf. on Radwaste Management and contract FI4D-CT9S-0001, progress report, January- Env. Remediation: Singapore, October 12-16, 1997. June 1997 (August 1997). R-3197.

Decommissioning of the BR3 PWR 71 BE9900073

Bernard NEERDAEL, Jan MARIVOET, Martin PUT, Jan VERSTRICHT, Pierre VAN ISEGHEM, Marc BUYENS Waste Disposal

Scientific staff -HE PRIMARY MISSION of the Waste Dis- nomena that are almost certain to take place Marc AERTSENS Tposal programme is to propose, develop, will be treated in a normal-evolution scenario, Jean-Dominique and assess solutions for a safe and acceptable but eight altered-evolution scenarios were also BARNICHON disposal of radioactive waste. Geological dis- identified. Rudi BEAUFAYS posal is considered a realistic solution for the Frédéric BERNIER final disposal of high-level and long-lived ra- The PORFLOW code allows us to simulate the re- Sven BODEN dioactive waste, whereas shallow-land burial is lease of radionuclides from the near field and Paul BORGERMANS examined for the disposal of low-level radio- their migration through the host clay layer, in Marc BUYENS active waste. In Belgium, deep geological burial order to analyse the consequences of the dis- Didier DE BRUYN in clay is the primary option for the disposal of posal of vitrified HLW. An example of the cal- Pierre DE CANNIÈRE High-Level Waste (HLW) and spent fuel. culated radionuclide fluxes into the Neogene Mieke DE CRAEN aquifer is given in Figure 1 for the case of Dominique DELLEUZE the normal-evolution scenario. The transport Performance assessment The Perfor- Bernard DEREEPER of radionuclides released from the host clay mance Assessment project focuses on assess- Ann DIERCKX through the aquifer into the biosphere is simu- ing the long-term safety and the acceptability Frank DRUYTS lated with the Groundwater Modelling System of disposal systems by developing and apply- François-Xavier (GMS) package. Calculations of the flow paths ing validated methods to the modelling of the allowed us to determine the area and the rivers HOLVOET various phenomena controlling the release and that might be influenced by radionuclides re- Bruno KURSTEN the migration of radionuclides from the repos- leased from the geological repository. Serge LABAT itory to the biosphere. This assessment re- Karel LEMMENS quires reliable data on the different compo- Philippe LOLIVIER 2 : nents of the system and more particulary on "•': :'::;: •; : Flux:[Bqim- -a-'];:; • :":'"'•' : : : : ::'::: Norbert MAES the most critical elements of integrated repos- Dirk MALLANTS itory systems. The programme is therefore Jan MARIVOET divided into complementary projects dealing Pol MEYNENDONCKX with particular aspects. Yves MEYUS Hugo MOORS Programme Running performance assess- Bernard NEERDAEL ments are elaborated in the framework of the Lorenzo ORTIZ following contracts and research agreements Vera PIRLET with NIRAS/ONDRAF and the EC: Brigitte PITZ Martin PUT • a multiyear research programme for elabo- Alain SNEYERS rating the performance assessment of the 10 Elie VALCKE potential geological disposal of radioactive IQ5; 1Ö6 Pierre VAN ISEGHEM waste in the Boom Clay layer at the Mol '•• Timé [a] ; Jan VERSTRICHT site; Geert VOLCKAERT Figure 1 Calculated fluxes of selected radionuclides « the SPent fuel Assessment (SPA) project, a William WACQUIER released from the host clay layer into the Neogene performance assessment of the direct dis- Lian WANG aquifer. Isabelle WEMAERE posal of spent fuel at the Mol site; » complementary concept assessments for For the SPA project, we collected the basics for Supporting staff shallow-land burial in Belgium and abroad. the assessment into a topical report covering Patrick BOVEN the geology and hydrogeology of the site, the Ben GIELEN Achievements We are elaborating a de- spent-fuel inventories, the packaging policy, Constant HENDRICKX tailed performance assessment for the Mol and the repository design. The next step of Alex ISENBORGHS site, following a strict quality-assurance pro- this assessment will be to select and describe Kurt JANSSEN cedure. The first step of this assessment con- the scenarios to be analysed. Kris MOERKENS sists in a systematic scenario study. All phe- Jef PEETERS In the framework of an internal R&D project, we Kris PENASSE Monique VAN GEEL Louis VAN RAVESTYN collected clay cores in clay pits and measured Frans SLEGERS Marc VAN GOMPEL Regina VERCAUTER the vertical and horizontal hydraulic conduc- Frank VANDERVOORT Maria VAN GOMPEL Bert VREYS tivity of the clay. The results of these mea-

72 Radioactive Waste and Cleanup surements, together with those obtained from model of Northeastern Belgium. This cam- the measurements on clay cores taken during paign is complemented by an internal R&D a data-acquisition campaign, are essential for project that investigates the spatial variabil- defining the spatial variability of this parame- ity of the hydraulic conductivity of the Boom ter of the Boom Clay on a regional scale. Clay.

Perspectives for 1998 The performance as- In the PHYMOL (PalaeoHYdrogeology of the MOL sessments regarding the geological disposal of site) project, sponsored by the EC, we will look reprocessing waste in the Boom Clay layer at for indications, on the basis of the geochemical the Mol site are long-lasting and iterative pro- distributions, regarding the ground-water flow cesses which will have to continue for some in the Mol region during a glaciation. more years. In particular in 1998, we will analyse in detail the normal-evolution scenario for Achievements The fourth borehole of the the most important waste types. We will use hydrogeological data-acquisition campaign has these results in our contribution on environ- been drilled at Weelde in 1997. It reaches the mental impact assessment to the SAFIR 2 report, top of the leper Clay and has allowed us to take to be presented in 1999 by NIRAS/ONDRAF to the cores and to carry out geophysical loggings. Belgian authorities responsible for radioactive The hydraulic conductivity of clay cores taken waste disposal. at Zoersel and Mol is measured to study the variability of the hydraulic conductivity of the From 1998 until 1999, we will perform the Boom Clay with depth and to look for correla- consequence analyses of spent-fuel disposal in tion with the lithostratigraphy of the clay layer. clay in the framework of the EC's SPA project. Perspectives for 1998 We will resume the Characterization of the geosphere The regional hydrogeological modelling by taking host rock is the natural and the main barrier into account the results obtained from the against the migration of radionuclides to the large 1996-1997 data-acquisition campaign. In biosphere. Its characterization includes that this respect, we will also further determine the of the confining layers and requires hydraulic conductivity on clay cores. • to characterize the Boom Clay formation ad- For the PHYMOL project, we will interpret the equately and to study its homogeneity; results of the first series of geochemical and • to collect the geological, piezometric, and isotope analyses on ground-water samples and hydraulic data required for studying the hy- develop models to explain the observed iso- drogeological system in the Mol area and to tope distributions. develop a regional aquifer model for North- eastern Belgium; Characterization of the waste Character- • to test and validate computer codes used izing the source term is of primary importance in the performance assessments for simu- for assessing a waste disposal system. It relating water flow and transport of radio- quires nuclides in aquifers; • to assess, through in situ and laboratory • to build confidence in long-term predictions corrosion experiments, the performance of by developing natural-analogue studies on candidate overpack materials as physical the Boom Clay formation itself. engineered barrier; • to determine or verify various chemical and Programme The hydrogeological studies physical characteristics of radioactive waste sponsored by NIRAS/ONDRAF are piezometric forms relevant to the Belgian waste manage- measurements in the boreholes of SCK«CEN'S ment programme; hydrogeological network and the elaboration of a data-acquisition campaign needed for fur- • to improve or develop tools and methods ther developing the multilayer regional aquifer for characterizing radioactive waste;

Waste Disposal 73 • to assess experimentally or demonstrate in We proposed a final interpretation of the in situ, in parallel with modelling works, the situ corrosion tests on glasses started some long-term behaviour of various waste forms ten years ago, focusing on the tests yielding with regard to their geological disposal in contact with Boom Clay at 90°C. An extended clay. programme of surface and profile analyses using Scanning Electron Microscopy - Energy- Programme The programme comprises the Dispersive Spectroscopy (SEM-EDS), Electron- following activities: Probe MicroAnalysis (EPMA) with X-rays, and Secondary-Ion Mass Spectroscopy (SIMS) on the • the nondestructive assay of real LLW pack- corroded glass samples enabled us to inter- ages, as part of a round-robin campaign, pret the measured mass losses. We demon- and the measurement of the leaching sta- strated the meaningfulness of the in situ test bility of cemented ion-exchange resins; data as compared with laboratory simulation • the investigation of the effect of the ra- tests. We obtained new information on the diolythic degradation of bituminised waste dissolution mechanisms from the longer ex- and of the degradation products of contam- periments (until 7.5 years). The effect of the inated cellulose waste on the solubility of glass composition on its dissolution upon in- americium and plutonium in geological dis- teraction with Boom Clay increases with time, posal situations (clay or bentonite environ- the difference between the "best" and "worst" ment); glass being about a factor of 30. We propose three types of dissolution behaviour: a matrix- • the study of the corrosion mechanisms of controlled dissolution in case of the Cogema HLW glass in geological disposal media, with glass SON68, a selective, diffusion-controlled special emphasis on the leaching behaviour dissolution in case of the DWK PAMELA glass of neptunium and technetium, and on the SAN60, and a quite fast dissolution for the DWK geochemical and mathematical modelling PAMELA glass SM513 associated with secondary- of the corrosion; in complement to this, the phase formation. The total depletion depth of characterization of neptunium complexes the glasses after 7.5 years ranges between a formed when neptunium-doped glass and few hundred microns and some tenths of a mi- clay water interact; cron. We also observed that the glass corrosion • the determination of the solubility of UO2 in contact with Boom Clay is very sensitive to temperature. We propose a dissolution rate of in Boom Clay water, emphasizing the effect 1 of humic acids and carbonates; 0.3 urn-a" at the ambient temperature of 16°C, suggesting that the glass matrix is indeed a bar- • the study by electrochemical techniques of rier in the geological disposal system. the corrosion stability of stainless-steel container materials in geological disposal me- We developed a geochemical model to describe dia, considering the influence of the most the interactions between HLW glass and Boom important parameters on pitting corrosion; Clay. This model, based on the combination of • the study by in situ tests of the interaction two submodels (glass/water and clay/water), between cemented or vitrified waste and uses the PHREEQC geochemical code and as- Boom Clay or backfill materials. sumes that the cation concentration in solution is controlled by single minerals. Silicon, Achievements We had to expand consider- for instance, would be controlled by the chal- ably our laboratory infrastructure to accom- cedony phase in Boom Clay. We obtained a modate the new R&D programmes started in good agreement between the calculated and 1997. We purchased three glove boxes to per- measured composition of the interstitial clay form tests under anaerobic atmosphere (pure water. So far, we only applied the model to argon, occasionally with control of the CO2 the Cogema glass SON68. The main finding is pressure). They are used for the plutonium and that the calculated soluble silica concentration 3 7 americium solubility study, the UO2 solubility in solution, Ks = 10~ - , remains below the sat- 2 9 study, and the electrochemical corrosion study uration limit of amorphous silica, Ks = 10~ - on container-materials. (representative for the glass). This explains

74 Radioactive Waste and Cleanup the corrosion-enhancing effect of Boom Clay, Figure 3 Surface layer profile calculated by Monte which acts as a sink for silica released from the Carlo modelling for a Na/Si ratio of 0.4 after 0.2 days glass and thus prevents saturation of the solu- of leaching. tion. Further efforts will consider variations in glass composition and other glasses, to try to explain the different corrosion behaviours and the possible occurrence of secondary minerals.

We made significant progress in modelling the Silica glass corrosion with a Monte Carlo transport TO. I code used to solve the mathematics of the transition state theory. This model assumes that Sodium the glass consists of two kinds of particles: a network former (silicon) and a network modifier (sodium), arranged on a diamond lattice in contact with water. Our Monte Carlo model so far assumes three processes: silica dissolu- 40011 tion, ion exchange, and diffusion of silicon or 1 Position [lattice: I WriitSM 1 sodium in water. We choose the model parameters, the probabilities and thermodynamic constants of the various processes, and the time The electrochemical corrosion tests on candi- step. The model calculations show two types date overpack materials were started. We fo- of dissolution behaviour. For small concentra- cus on the AISI316L stainless steel recently pro- tions of the network modifier (sodium), disso- posed by NIRAS/ONDRAF and investigate to a mi- lution is congruent and the dissolution of the nor extent other materials such as other stain- network former (silicon) dominates the disso- less steels, carbon steel, and nickel and tita- lution process. For higher concentrations of nium alloys, using a standard corrosion cell. the network modifier, the dissolution is not The environmental conditions selected include congruent and large surface layers form. Typ- Boom Clay and bentonite media, aerobic and ical results from geochemical and Monte Carlo anaerobic conditions, various concentrations modelling are shown in Figures 2 and 3. of agressive agents (Cl~ and S2O3~), and temperatures of 16, 90, and 140°C. Polarization curves allow us to determine the characteristic potentials, for instance the critical potential for pit nucleation £np.

The new electrochemical corrosion programme started by establishing a procedure to fabri- cate crevice-free working electrodes. A method using a double epoxy-resin system for embed- ding the metal yields good results. Preliminary results in clay water under aerobic conditions show that only carbon steel corrodes (by uni- form corrosion) at 16°C, whereas more materials show signs of pitting corrosion at 90°C, for certain concentrations of Cl~ and S2O3".

Progress on new projects includes the follow- Reaction; progrfiss;[rridlgjassHI.~:|]::: ing achievements.

Figure 2 Measured (points) and calculated (line) • Five full-size LLW packages were assayed concentrations of silicon released from the SON68 by (nondestructive) gamma spectroscopy or glass in a Boom Clay / clay-water slurry, at 90'C. passive neutron counting.

Waste Disposal 75 • We started to qualify some real cemented Tube with 60Co sources ion-exchange resins produced by the Doel Heating element power plant regarding homogeneity and leaching. Filter a We performed radiolythic degradation tests Glass samples on inactive Eurobitum samples, by irradi- ating them for a total absorbed dose of 4.3 MGy in the BRIGITTE facility in BR2. The degradation products were fully analysed Backfill B and their effect on the americium and plutonium solubility studied. The project on Piezometers alpha-contaminated cellulose waste follows a similar rationale. Backfill A • New solubility tests on UO2 in various types of clay waters aim to investigate the effect of humic acids and carbonate. Within two months, we obtained uranium solubility data between 2 and 8 x 10~7 M. The real solubility might be slightly higher. m We started to investigate the neptunium Figure 4 Three-dimensional view of a CORALUS test complexes formed when HLW glass inter- tube. Backfill and outer porous support tube of mod- acts with Boom Clay water. This study in- ules B and C are cross-sectioned to show details of the volves leach tests with neptunium-doped inner support tube. glass, the determination of the complexation constant for Np(rv) with humic acids, Important milestones will however be achieved and the characterization of the complexes in 1998. In particular, we will submit our inter- formed by means of laser-induced photo- nal quality-assurance system to an external au- acoustic spectroscopy. dit for accreditation and we will complete the • We prepared new tests on cemented waste, round-robin campaign for nondestructive as- with a view to investigating its long-term be- say of full-size waste packages. haviour in disposal conditions in Boom Clay (in situ corrosion test tubes). Among the ce- For the waste forms relevant to the Belgian pro- ment formulations used, one incorporates gramme, we can further mention the reprocessed BR2 fuel. • the laser-induced photoacoustic spectro- • Another new in situ project, the CORALUS scopy analyses to be performed on the nep- experiment, investigates the interaction be- tunium complexes from the leach tests on tween alpha-doped waste glass and ben- the neptunium-doped glass, in collabora- tonite backfill or Boom Clay. As a special tion with Belgian and German institutions; feature, it includes 60Co gamma-radiation • the electrochemical and immersion tests to sources and instrumentation allowing solu- be started in the framework of the corrosion tion and gas sampling and analysis. The programme on canister materials; first test—a blank tube—will start during the first semester of 1998 (Fig. 4). • the new in situ corrosion tests to be installed with cement specimens and leach tests to be carried out on fully active ce- Perspectives for 1998 Since many experi- mented reprocessed BR2 fuel; ments developed within the programme on waste packages, such as the CORALUS experi- • the solubility and sorption tests with ameri- ment, are rather time-consuming, they will con- cium and plutonium to be performed for the tinue in 1998. bitumen and cellulose project.

76 Radioactive Waste and Cleanup Processes taking place (on the way) from anaerobic corrosion experiments in clay slur- the repository to the biosphere Assess- ries to study the corrosion rate of stainless and ing the performance of geological disposal sys- carbon steel in contact with Boom Clay. tems requires knowledge of the source term and the near field, but also understanding and More recently, the study of the influence of forecast of the migration of radionuclides in the organic matter present in the clay water clay, their transport in the aquifers, and their contributed substantially to the migration pro- potential release into the biosphere, as well as gramme. Migration tests study the diffusion any process which might lead to the creation of of actinides and fission products, and the mo- migration paths. Therefore the following four bility of the dissolved organic matter in the in- objectives are of primary importance: terstitial clay water. Experiments with labelled organic matter are also performed. • to develop, test, and validate a conceptual and a mathematical model for the migration Large-scale three-dimensional validation ex- of radionuclides in clay, resorting to both periments are in progress. Installed from the laboratory and large-scale in situ migration underground research facility, they use triti- experiments; ated water and 14C-labelled bicarbonate. • to develop, test, and validate a model for the thermohydromechanical and chemical be- In the framework of doctoral and postdoctoral haviour of an unsaturated clay-based back- theses, we develop electrokinetic methods to fill material; accelerate the time-consuming migration experiments (Fig. 5) and we study the Boom Clay m to study the generation of hydrogen gas formation as a natural analogue to increase the due to anaerobic corrosion of metals and confidence in the modelling results for very its subsequent migration through the clay long time spans. by diffusion and gas breakthrough; a to investigate the reaction of a clay environ- Regarding the near field, the first phases of ment to the temperature increase and the the CERBERUS project quantified the medium ef- radiation dose in case of disposal of repro- fects (Eh, pH, hydrogen production) induced by cessed HLW in the Boom Clay layer. a HLW canister simulated with heating elements and 60Co sources. After retrieval of the sources Programme As regards the far field, we ex- and hydration of the backfill, we are presently tended a few years ago the part of the pro- analysing the near-field effects on clay sam- gramme related to the clay host rock from the ples cored in the surrounding clay. The pro- migration of radionuclides in the Boom Clay gramme investigates further the performance formation to the study of gas migration. With of selected clay-based materials in different ex- regard to gas generation, we also performed perimental conditions and configurations.

Figure 5 Experimental setup of the electrokinetic migration experiments.

Waste Disposal 77 The RESEAL project aims at the large-scale in ;:Eu; Adsorption situ demonstration of the feasibility of sealing a repository in a clay formation. In co- operation with European partners, we will seal 100 :- an experimental shaft and test it for water and gas tightness. This experiment will also help us validate models for the calculation of water and gas flow through both clay seal and near- field clay.

The CATSIUS CLAY project is another validation and benchmark exercise for codes dealing with the hydromechanical and thermomechan- ical behaviour of unsaturated clays. To support code development, we continue to study ::PH: different clay-based backfill materials with Eu- ropean partners. In particular, for model val- Figure 7 Europium sorption on illite as a function idation, we propose the representative set of of pH and NaCIC>4 concentration. reference field data obtained through the in Situ test BACCHUS 2. • the statistical reliability of the migration parameters increases markedly; Achievements We continued the time-con- • soil characteristics such as the dispersion suming experiment allowing us to determine length and electro-osmotic mobility were the migration parameters in Boom Clay of the determined; radionuclides of major concern. • retardation coefficients for cationic species can also be obtained. We demonstrated and validated the applicability of the electrokinetic methods to determine To increase the confidence in the long-term diffusion coefficients in porous media (Fig. 6): model predictions of the radionuclides migra- • diffusion coefficients can be obtained by in- tion, we characterized in detail the mineralogy dependent calculation methods; and the geochemistry of the Boom Clay on sam- B the experimental time for diffusion studies ples of the Zoersel and Mol-1 drillings. We reduces markedly; paid special attention to the distribution and mobility of the trace elements (lanthanides,

v uranium, and thorium) naturally occurring in Bulk attii/itV: [tps g the Boom Clay; these can be considered as 1500 natural analogues of critical elements for the long-term safety of a radioactive-waste disposal site. We are presently characterizing the radiochemistry of the Boom Clay. 1000 -

To study the fundamental interactions of radionuclides and Boom Clay, we developed a 500 •- multisite sorption model for clay minerals. This model allows us to integrate a sorption database into a thermodynamics-based geochemical equilibrium calculation. Figure 7 :-4 shows the good agreement between the mea- Distance from source [m] sured and the modelled sorption data for an europium-illite system. The lines are cal- Figure 6 Distribution profiles after electromigration culated by the multisite model considering of 85Sr (72V-m"', 71 hrs), 22Na (84 V-rrr1, 20 hrs), both cation exchange and surface complexa- HTO(79V-m-', 20 hrs), 131I (81 V-rrr1, 20 hrs). tion sorption.

78 Radioactive Waste and Cleanup We continued to monitor and sample the large- regarding the composition (mineralogy, geo- Figure 8 scale in situ injection experiment with tritiated chemistry) of clay cores taken from the back- Experimental setup water, started in January 1988. After 10 years, fill material and drilled from the host clay in during the mounting of the measured tritium concentrations in the in- close contact with the canister wall. We also re- the clay blocks for the terstitial water still agree very well with the re- trieved the waste glass and container material borehole-sealing test. sults of the MICOF computer code simulation. samples embedded in the surroundings. Their analysis is in progress. Regarding our large-scale three-dimensional in situ migration experiment started in 1995, we The study of the gas generation caused by detected tritium in the filters located at one me- anaerobic corrosion and the gas migration in tre from the injection point, but the 14C level Boom Clay is in progress. Stainless steel 316L is still below the detection limit. shows almost no anaerobic corrosion in contact with a Boom Clay slurry. We continued our research on the mobility of the dissolved organic matter (humic acids) in In co-operation with different European part- the interstitial clay water using labelled or- ners, we developed and tested computer codes ganic matter in the framework of an EC con- for the hydromechanical and thermomechani- tract (TRANCOM-CLAY project). Two labels were cal behaviour of unsaturated clay-based back- tested for their stability in contact with Boom fill material; these codes were applied to the Clay: the 12SI label proved to be unstable, results of support laboratory experiments and whereas the experiments with the 14C one large-scale in situ tests, one of which is the BAC- showed a good stability. CHUS 2 test, already running successfully for four years. Percolation experiments through clay cores and a new large-scale in situ injection experi- After full hydration of the backfill, we mea- ment are being performed with14 C-labelled or- sured the hydraulic and gas transport param- ganic matter. eters and confirmed the homogeneity and the tightness of the hydrated backfill. The pH and £h of the Boom Clay are measured under real in situ physicochemical conditions: We obtained within the CATSIUS CLAY project clay water, at a hydraulic pressure of 11 bar, in the first simulations of the hydraulic pressure equilibrium with its inorganic carbon species and the stress evolution inside and around the (CO2 equilibrium partial pressure). We mea- BACCHUS 2 test. sured an in situ pH value of 8.2. We also continued two previous actions: As part of the study of the homogeneity of • confirming the first indication of desatura- the Boom Clay layer, the hydraulic conductivity tion recorded in clay around the PHEBUS test; and migration parameters for tritiated water this will require some more months of ven- and iodine were measured for clay cores sam- tilation through the large filter element em- pled over the whole thickness of the formation. bedded in clay;

In the near field, we investigated the influence • pursuing the long-term monitoring (water of both temperature and radiation on the mi- pressure, displacement, and radial, axial, gration properties of the Boom Clay through and total stresses) around the underground the results of an in situ migration experiment facility to control its stability and provide with 241Am and "Tc, in the surroundings of long-term geotechnical measurements for the CERBERUS demonstration test. The influ- the modelling of the clay behaviour. ence of these parameters on the migration properties appears to be negligible, confirming We developed a borehole-sealing test, as a previous direct measurements. preliminary action within the large-scale sealing experiment of the exploratory shaft in the After the hydration phase of the backfill of HADES infrastructure (Fig. 8). This test aims at CERBERUS, we launched a detailed campaign following the hydration process of two swelling

Waste Disposal 79 clay seals and at testing their water and gas tightness after saturation. The experimental setup, installed in a 15-metre-long borehole with a diameter of 25 cm, includes the two following seals: one with FoCa clay (a French bentonite) and one with Serrata clay (a Spanish bentonite). We will finalize the design of the shaft-sealing test on the basis of our results. The design of the host-rock instrumentation, including sensors for water pressure, ground stress, and displacement, is finished; the construction is in progress.

We performed a series of support laboratory experiments to measure the hydromechanical and gas flow parameters of the sealing materials and of unsaturated Boom Clay. These parameters are used for design calculations and blind predictions of the behaviour of the borehole and shaft seals. The simulations show the sensitive influence of the unsaturated hydraulic parameters and boundary conditions on the saturation time. Figure 9 The PRACLAY mock-up before installation of the cover flange. Perspectives for 1998 With regard to migration, the electrokinetic method will be applied to sorbed species, but some other devel- • to provide infrastructure and technical as- opments are awaited in the framework of new sistance to the experimenters, from the in- R&D proposals on site remediation. stallation phase to the follow-up of any demonstration or validation test. To study the exchange between mobile and im- mobile organic matter, we will perform migra- Programme The daily and medium-term tion experiments with doubly labelled matter. operation of the underground research facility under safe conditions requires maintenance and assistance works. Maintenance ensures Underground infrastructure SCK-CEN and improves the safety and stability of the fa- has constructed and operates a unique under- cility and its technical equipment, whereas as- ground research facility, called HADES, located sistance means support to experimenters for in the Boom Clay layer at a depth of 225 me- drilling activities, access to the experimental tres. In this facility, it carries out in situ ex- areas in representative conditions, and reliable periments, studies the disturbances due to the and traceable data acquisition. construction of infrastructures in clay, and optimizes the design and the construction of a fi- The real-scale simulation of a disposal gallery nal repository. Indeed, the infrastructure must (PRACLAY experiment) follows the current con- be adapted to its geological environment and cept of a concrete-lined gallery with a cen- plays an important role in the global perfor- tral stainless-steel tube containing the waste mance of the near field. It is therefore also forms. Bentonite-based backfill blocks fill the necessary gap between the central tube (diameter of m to improve the knowledge about digging 0.5 metre) and the lining (inner diameter of large excavations in deep clay in order to 2 metres). Whereas the actual disposal gal- select the most appropriate techniques for leries will be several hundred metres long, building a final repository and to get expe- the PRACLAY demonstration gallery will be re- rienced in safely operating such facilities; stricted to 30 metres. Electrical heaters will

80 Radioactive Waste and Cleanup simulate the generation of heat by the waste Pore pressure distribution in front of II • _ • • . :: • • | M forms, since the experiment will not use active FLAC (Version 3.30)

ones. The construction of the PRACLAY gallery LEGEND requires that of a second shaft and of a gallery connecting it to the current infrastructure. step 136000

Pore pressure contours (kPa) We built a five-metre-long surface mock-up I—I -1500 M -1000 having a cross-section similar to that of the dis- H "500 posal gallery as far as central tube and backfill R 500 Ml 100° 1 are concerned (Fig. 9). A steel liner will keep the g 1500 backfill under pressure when the latter starts Contour interval 500 kPa "£I!3^^^^^^^^^^^^^^^^^^^^^H- 3 to swell due to water uptake. Boundary plot -'Lual^^^^^^^^^^^^^^^^^^^^^^^^^^V

Achievements The activities of the support team were mainly core sampling, drilling and overcoring, preparation or installation of new SCK.CEN WASTE AND DISPOSAL UNIT experiments, and follow-up of running ones. I 3 S 7 9

Figure 11 Calculations of pore pressures in clay We provided assistance to the EIG PRACLAY, in during gallery excavation. charge of the extension of the underground facility, for such actions as defining the technical specifications for the construction of the The monitoring and modelling related to the second shaft, analysing the corresponding ten- excavation of the connecting gallery resulted ders, and, presently, following up the construc- in the European project CLIPEX, with French and tion works. In November, after such prelimi- Spanish partners, and co-ordinated by the EIG nary works as the freezing of the water-bearing PRACLAY. The project, started at the beginning sands down to a depth of 190 metres, the con- of 1997, will run until the end of 1999. tractor started to excavate the second shaft (Fig. 10). This shaft and its equipment should First estimates of the displacements and stress be put in operation in early 1999. We are now variations around the excavation (Fig. 11) al- providing similar assistance for drafting the lowed us to draft the final specifications for the specifications for the excavation of the con- instrumentation, such as the location and mea- necting gallery. suring range of the proposed instruments and sensors, of which some are already ordered (stress, displacement). We devoted special attention to the compatibility of the instrumentation with the future excavation works.

In April 1997, we started to install the backfill and the instrumentation of the mock-up, after acceptance of the mock-up structure in January and after final acceptance of the demonstration building. After installation of the cover -If," and installation and connection of the instru- •1* mentation racks, we flooded the mock-up at the beginning of December. We expect a sufficient hydration of the backfill by early 1998 to switch on the heating elements.

tl t> Perspectives for 1998 To optimize the planning and execution of drilling works, we will Figure 10 Construction of the hoisting equipment purchase a new coring equipment at the begin- for shaft sinking. ning of 1998.

Waste Disposal 81 The excavation of the second shaft will extend over the whole of 1998. In parallel, we will finalize the specifications for the excavation Scientific partners Atomic Energy Author- of the connecting gallery and of the PRACLAY ity (AEA Technology) — Association pour la recherche gallery, and analyse tenders. et le developpement des methodes et processus industriels (ARMINES) — Belgische Geologische Di- The installation of the CLIPEX instrumentation enst/Service geologique de Belgique (BGD/SGB) — related to the connecting gallery will take place British Geological Survey (BGS) — Commissariat a in the first quarter of 1998, from the exist- 1'energie atomique (CEA) — Centre beige d'etude ing underground structure (test drift); this will de la corrosion (CEBELCOR) — Chinese Institute for guarantee sufficient time for restoration of the Atomic Energy (CIAE) — Chalmers University of ground conditions around the measuring de- Technology — Centro de Investigaciones Energeti- vices before the start of the digging works, cas, Medioambientales y Tecnologicas (CIEMAT) — scheduled for the second semester of 1999. Centro Internacional de Metodos Numericos en A characterization and monitoring programme Ingenieria (CIMNE) — Clay Technology Lund AB — En- will be developed prior to this installation to ergieonderzoek Centrum Nederland (ECN) — Etudes- get more accurate data on some essential geo- recherches-materiaux (ERM) — Forschungszentrum mechanical parameters. This programme and Karlsruhe (FZK) — University of Aberdeen — Groupe- the associated interpretation will enable us ment pour l'etude des structures souterraines de to improve the current models on the hydro- stockage (G3S) — GEOCONTROL — Stockage souter- mechanical behaviour of the clay. rain (GEOSTOCK) — Gesellschaft fur Anlagen- und Reaktorsicherheit (GRS) — Institut de protection et de The heating of the PRACLAY surface mock-up surete nucleaire (CEA-IPSN) — Institute for Reference will most likely be launched during the first Materials and Measurements (IRMM) — Instituto quarter of 1998, depending on the evolution Sperimentale Modelli E Strutture (ISMES) — KEMA of the current hydration phase of the backfill Nuclear — Katholieke Universiteit Leuven (KUL) — material. University of Loughborough — Universite de Liege (ULg) — QuantiSci Ltd — Technical University of Delft — Tractebel — Teollisuuden Voima Oy, Development Office (TVO) — Universite catholique de Louvain (UCL) — University of Coruna — Uni- versite Libre de Bruxelles (ULB) — University of Roma — University of Birmingham — University of Exeter — Polytechnic University of Madrid (UPM) — Polytechnic University of Cataluna (UPC) — Uni- versite de Paris-Sud (UPS) — University of Wales, College of Cardiff (uwcc) — Vlaamse Instelling voor Technologisch Onderzoek (VITO) — Vrije Univer- siteit Brussel (VUB) — Technical Research Centre of Finland (VTT)

Sponsors European Commission (EC) — Electricite de France (EdF)

Customers Nationale Instelling voor Radioacrief Afval en Verrijkte Splijtstoffen/Organisme national des dechets radioactifs et des matieres n'ssiles enrichies (NIRAS/ONDRAF) —• Economic Interest Group PRACLAY (EIG PRACLAY) — Agence nationale pour la gestion des dechets radioactifs (ANDRA) — Empresa Nacional de Residuos Radioactivos SA (ENRESA)

82 Radioactive Waste and Cleanup F. BERNIER, V. LABIOUSE, "Performance of Gallery Construction Methods for the Disposal of High Level Book published in 1997 Waste," Topical day on Feasibility and Acceptability of Nuclear Waste Disposal in the Boom Clay Formation: P. VAN ISEGHEM, "Characterization of Radioactive SCK>CEN, Mol, Belgium, Jan. 29, 1997. BLG-726, 7-14. Waste Forms and Packages," Technical Reports Series 383 (IAEA, 1997, 138 pages). F. BERNIER, G. VOLCKAERT, "BACCHUS 2: A Valida- tion Experiment for Hydromechanical Models for Publications in 1997 Unsaturated Soils," Workshop on Environmental Geotechnics—Design Parameters for Computing D. DE BRUYN, L. VAN CAUTEREN, "De tweede schacht Applications: Warsaw, Poland, March 6-7, 1997. te Mol: Een eerste stap in de verdére uitbreiding Proc., 23-46. van een ondergronds onderzoekslaboratorium," Geotechniek l:n/4, 10-12 (1997). P. BORGERMANS, "The Use of Optical Fibre Sensors in the Geological Disposal of Waste," Topical day J. MARIVOET, I. WEMAERE, P. ESCALIER DES ORRES, on Feasibility and Acceptability of Nuclear Waste P. BAUDOIN, C. CERTES, A. LEVASSOR, J. PRIJ, Disposal in the Boom Clay Formation: SCK-CEN, Mol, K. H. MARTENS, K. RÖHLIG, "The EVEREST Project: Belgium, January 29, 1997. BLG-726, 77-85. Sensitivity Analysis of Geological Disposal Systems," Reliability Engineering and System Safety 57, 79-90 D. DE BRUYN, L. VAN CAUTEREN, "Thermo-Hydro- (1997). Mechanical Strength of Saturated Boom Clay: Lessons Learned from the '90 Studies," The Boom H. MOORS, N. MAES, A. DIERCKX, P. DE CANNIÈRE, Clay Seminar: Bilzen, Belgium, December 8-9, 1997. M. PUT, "Determination of the Apparent Molecular BLG-758, 77-80. Diffusion Coefficient of Ionic Species in Water Satu- rated Porous Media by Electrokinetic Amplification," D. DE BRUYN, J. VERSTRICHT, "The Design of the Handbook of preprints of papers for the third Eu- PRACLAY Experiment and the Behaviour of Boom Clay ropean Engineering Geology conf., "Geo-Engineering at Elevated Temperature," Topical day on Feasibility of Hazardous and Radioactive Waste Disposal", and Acceptability of Nuclear Waste Disposal in 355-368 (1997). the Boom Clay Formation: SCK-CEN, Mol, Belgium, January 29, 1997. BLG-726, 27-33. P. VAN ISEGHEM, M. AERTSENS, S. BODEN, K. LEMMENS, Ph. LOLIVIER, V. PlRLET, A. SNEYERS, E. VALCKE, P. DE CANNIÈRE, H. MOORS, A. DIERCKX, F. GASIAUX, "Determining Long-Term Stability of Radwaste upon M. AERTSENS, M. PUT, P. VAN ISEGHEM, "Diffusion Disposal in Clay," Nuclear Europe Worldscan 3-4, 56 and Sorption of 32Si-Labelled Silica in the Boom (1997). Clay," Sixth int. conf. on the Chemistry and Migration Behavior of Actinides and Fission Products in the Presentations delivered in 1 997 Geosphere (MIGRATION'97): Sendai, Japan, October 26-31, 1997. M. AERTSENS, P. VAN ISEGHEM, "Molecular Modeling of Glass Dissolution," Fundamentals of Glass Science A. DIERCKX, P. DE CANNIÈRE, M. AERTSENS, "Organic and Technology: Vaxjo, Sweden, June 9-12, 1997. Matter and Migration (TRANCOM-CLAY project)," The Proc, 444-449. Boom Clay Seminar: Bilzen, Belgium, December 8-9, 1997. BLG-758, 33-41. F. BERNIER, "Excavations in the Boom Clay Formation: Performance of Construction Methods," The Boom A. DIERCKX, P. DE CANNIÈRE, P. WARWICK, A. HALL, Clay Seminar: Bilzen, Belgium, December 8-9, 1997. M. J. PUT, "Stability of 12SI and 14C-Labelled Boom Clay BLG-758, 51-61. Organic Matter," Sixth int. conf. on the Chemistry and Migration Behavior of Actinides and Fission F. BERNIER, F.-X. HOLVOET, J. VERSTRICHT, G. VOL- Products in the Geosphere (MIGRATION'97): Sendai, CKAERT, "Area Where Parallel Non-Saturated Hydro- Japan, October 26-31,1997. Mechanical Codes Can Be Used in the Frame of High-Level Waste Repository in Boom Clay," Work- A. DIERCKX, H. MOORS, P. DE CANNIÈRE, N. MAES, shop on Tests and Applications of Computing Codes M. PUT, "Migration of Radionuclides," Topical day on Geoenvironmental and Civil Engineering Prob- on Feasibility and Acceptability of Nuclear Waste lems: Budapest, Hungary, September 25-26, 1997. Disposal in the Boom Clay Formation: SCK-CEN, Mol, Proc, 1-15. Belgium, January 29, 1997. BLG-726, 65-75.

Waste Disposal 83 F. DRUYTS, B. KURSTEN, P. VAN ISEGHEM, "Electro- Cleaner Environment: Tucson, Arizona, USA, March chemical Study of the Pitting Corrosion of Stainless 2-6, 1997. Steel Candidate Overpack Materials for the Disposal L. ORTIZ, F.-X. HOLVOET, "Gas Generation by of High-Level Radioactive Waste in Boom Clay," Sixth Anaerobic Corrosion in Clay," PEGASUS Progress int. symp. on Electrochemical Methods in Corrosion meeting: Mol, Belgium, May 27-28, 1997. Research (EMCR'97): Trento, Italy, August 25-29, 1997. L. ORTIZ, G. VOLCKAERT, "Multiphase Flow in the Boom Clay Layer," Topical day on Feasibility and V. LABIOUSE, "Hydro-Mechanical Behaviour of Acceptability of Nuclear Waste Disposal in the Boom Unsaturated Soil: Parameter Selection for an Clay Formation: SCK-CEN, Mol, Belgium, January 29, Elasto-Plastic Model," Workshop on Environmental 1997. BLG-726, 35-42. Geotechnics—Design Parameters for Computing Applications: Warsaw, Poland, March 6-7, 1997. L. ORTIZ, G. VOLCKAERT, "Gas Migration in Clay Proc, 76-90. under Isotropic Stress Conditions," PEGASUS Progress meeting: Mol, Belgium, May 27-28, 1997. V. LABIOUSE, "Numerical and Analytical Modelling of a New Gallery in the Boom Clay Formation," Sixth L. ORTIZ, G. VOLCKAERT, M. IMPEY, S. EINCHCOMB, int. symp. on Numerical Models in Geomechanics "A Phenomenologic Study of Multiphase Fluid Flow (NUMOG VI): Montreal, Quebec, Canada, July 2-4, through Water Saturated Boom Clay," Conf. on 1997. Proc, 489-494. Experimental Heat Transfer, Fluid Mechanics, and Thermodynamics 1997: Brussels, Belgium, June 2-6, V. LABIOUSE, F. BERNIER, "Hydro-Mechanical Dis- 1997. Proc., 4, 2407-2413. turbances around Excavations," Topical day on Feasibility and Acceptability of Nuclear Waste Dis- V. PIRLET, P. VAN ISEGHEM, A. DIERCKX, J.-F. DESREUX, posal in the Boom Clay Formation: SCK- CEN, Mol, "The Investigation of the Neptunium Complexes Belgium, January 29, 1997. BLG-726, 15-26. Formed upon Interaction of High-Level Waste Glass and Boom Clay Media," Actinides'97: Baden-Baden, V. LABIOUSE, C. GREGOIRE, "Predicted and Observed Germany, September 1997. Build-Up of Water Pressure Following the Installation of Piezometers in a Deep Clay Formation," Ninth int. M. PUT, A. DIERCKX, M. AERTSENS, P. DE CANNIERE, conf. on Int. Association for Computer Methods and "Mobility of the Dissolved Organic Matter through Advances in Geomechanics (IACMAG): Wohan, China, Intact Boom Clay Cores," Sixth int. conf. on the November 2-7, 1997. Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere (MIGRATION'97): Ph. LOLIVIER, K. LEMMENS, P. VAN ISEGHEM, "GeO- Sendai, Japan, October 26-31, 1997. chemical Modelling of the Interaction of HLW Glass with Boom Clay Media," xxith Scientific Basis for M. PUT, J. MARIVOET, G. VOLCKAERT, B. NEERDAEL, Nuclear Waste Management: Davos, Switzerland, "How Performance Assessment of a Geological September 29-October 2, 1997. Waste Disposal in Clay Has Contributed to Fo- cus the Radionuclide Migration Research," Waste N. MAES, H. MOORS, P. DE CANNIERE, M. AERTSENS, Management'97 HLW, LLW, Mixed Wastes and Envi- M. PUT, "Determination of the Apparent Molecular ronmental Restoration—Working towards a Cleaner Diffusion Coefficient of Ionic Species in Boom Clay Environment: Tucson, Arizona, USA, March 2-6, 1997. by Electromigration: A Feasibility Study," Sixth int. conf. on the Chemistry and Migration Behavior of R.L. SCHULTZ, D.E. CLARK, G.G. WICKS, A.R. LOD- Actinides and Fission Products in the Geosphere DING, P. VAN ISEGHEM, "Characterization of Savannah (MIGRATION'97): Sendai, Japan, October 26-31, 1997. River Glasses Buried in Boom Clay: The HADES Tests at Mol, Belgium," Int. symp. on Waste Management J. MARIVOET, "Uncertainty and Sensitivity Approach Technologies in Ceramic and Nuclear Industries: Used in the SPA Project," EC cluster meeting on Safety Cincinnati, Ohio, USA, May 4-7, 1997. Evaluation of Spent Fuel Disposal: Brussels, Belgium, November 13, 1997. A. SNEYERS, P. VAN ISEGHEM, "The Leaching Behaviour of Bituminized Radioactive Waste in the Geological B. NEERDAEL, G. VOLCKAERT, A. SNEYERS, "Past and Disposal Conditions of the Boom Clay Formation," Current R&D Program for Waste Disposal in Belgium," XXIth Scientific Basis for Nuclear Waste Management: Waste Management'97 HLW, LLW, Mixed Wastes and Davos, Switzerland, September 29-October 2, 1997. Environmental Restoration—Working towards a

84 Radioactive Waste and Cleanup P. VAN ISEGHEM, R. CARCHON, P. DE REGGE, "SCK-CEN L. WANG, P. DE CANNIERE, A. MAES, R. GENS, "Sorption as a Waste Characterization Laboratory," RADWAP'97: of Europium onto Mite: Mechanistic Interpretations," Wurzburg, Germany, June 23-26, 1997. NEA int. meeting on Chemical Modeling of Sorption in the Field of Radioactive Waste Management: Oxford, P. VAN ISEGHEM, B. KURSTEN, K. LEMMENS, A. SNEYERS, United Kingdom, May 6-8, 1997. "R&D on the Long-Term Stability of Waste Packages," Topical day on Feasibility and Acceptability of L. WANG, A. MAES, P. DE CANNIERE, J. VANDERLEE, Nuclear Waste Disposal in the Boom Clay Formation: "Sorption of Europium on Mite," Sixth int. conf. on the SCK-CEN, Mol, Belgium, January 29, 1997. BLG-726, Chemistry and Migration Behavior of Actinides and 55-65. Fission Products in the Geosphere (MIGRATION'97): Sendai, Japan, October 26-31,1997. P. VAN ISEGHEM, E. VALCKE, N. GODON, N. JOCK- WER, "CORALUS: An Integrated In Situ Corrosion J. WEI, P. VAN ISEGHEM, L. WANG, "The Adsorption Test on a-Active Glass," xxith Scientific Basis for of Humic Acids and Europium-Humate Colloids Nuclear Waste Management: Davos, Switzerland, onto Repository Components: Boom Clay, Bentonite September 29-October 2, 1997. and Fe2O3," XXIth Scientific Basis for Nuclear Waste Management: Davos, Switzerland, September 29 - G. VOLCKAERT, F.-X. HOLVOET, A. GENS, J. VAUNAT, October 2, 1997. Th. LASSABATERE, Ch. IMBERT, M. VILLAR, E. MOUCHE, A. GENTY, C. LEPOTIER, F. CANY, A. MILLARD, "RESEAL, I. WEMAERE, J. MARIVOET, "Role de l'hydrogeologie re- a Large-Scale Demonstration Test for REpository gionale dans un systeme d'enfouissement geologique SEALing in an Argillaceous Host Rock," Cluster de dechets radioactifs, en l'occurrence, l'Argile de underground research laboratories, EC seminar on In Boom," Colloquium CBGI: Leuven, Belgium, November Situ Testing in Underground Research Laboratories 18-20, 1997. for Radioactive Waste Disposal: Bilzen, Belgium, I. WEMAERE, J. MARIVOET, "Can We Extrapolate December 10-11, 1997. EUR 18323 EN, 39-57. Hydraulic Parameters of the Boom Clay from the G. VOLCKAERT, J. MARIVOET, I. WEMAERE, "Perfor- Local to the Regional Scale," The Boom Clay Seminar: mance Assessment of a Geological Radioactive Waste Bilzen, Belgium, December 8-9, 1997. BLG-758, 15-26. Repository in a Clay Layer," Topical day on Feasibility I. WEMAERE, J. MARIVOET, H. PITSCH, C. BEAUCAIRE, and Acceptability of Nuclear Waste Disposal in C. MARLIN, J.L. MICHELOT, A.C. PHILIPPOT, M. HAS- the Boom Clay Formation: SCK-CEN, Mol, Belgium, SANIZADEH, F. VAN WEERT, "The PHYMOL Project," NEA January 29, 1997. BLG-726, 43-55. workshop on Use of Hydrogeochemical Information G. VOLCKAERT, L. ORTIZ, F.-X. HOLVOET, "Gas Testing Groundwater Flow: Borgholm, Sweden, Migration through Clay-Based Backfill and Sealing September 1-3, 1997. Materials and Related In Situ Tests," PEGASUS progress meeting: Mol, Belgium, May 27-28, 1997. Lectures taught in 1997

G. VOLCKAERT, J. WALRAVENS, "Performance M. AERTSENS, "Modelling of Glass Dissolution with a Assessment of the Belgian Concept for the Shallow Monte Carlo Method," Summer University on Glass: Land Burial of Low-Level Radioactive Waste," INMM, Mejannes-le-Clap, France, September 1-6, 1997. Low-Level Radioactive Waste technical seminar: P. VAN ISEGHEM, "In Situ Corrosion Tests on HLW Glass Cordoba, Spain, October 8-10, 1997. as Part of a Larger Approach," Summer University W. WACQUIER, P. VAN ISEGHEM, "Characterization on Glass: Mejannes-le-Clap, France, September 1-6, of Cemented Evaporator Concentrates," RADWAP'97: 1997. Wurzburg, Germany, June 23-26, 1997. Theses published in 1997 L. WANG, P. DE CANNIERE, Ph. LOLIVIER, W. ZHOU, "Interaction of Radionuclides with Boom Clay L. CALLEWAERT, "Etude du comportement thermo- Components: Towards a Mechanistic Model," Topical hydro-mecanique d'un echantillon d'argile de day on Feasibility and Acceptability of Nuclear Waste Boom: Ameliorations technologiques de la mesure Disposal in the Boom Clay Formation: SCK-CEN, Mol, de pression interstitielle," final-year thesis, Civil Belgium, January 29, 1997. BLG-726, 77-85. Engineering (Universite catholique de Louvain, Louvain-la-Neuve), May 1997.

Waste Disposal 85 S. CAPEAU, V. CORTHOUTS, K. DE TORCK, P. LAMMAR, P. ESCALIER DES ORRES, J. MARIVOET, K.H. MARTENS, R. RAMDAS, "Radioactief afval: Een technisch J. PRIJ, N. CADELLI, "Sensitivity Analysis in Per- en maatschappelijk probleem," final-year thesis, formance Assessment of Geological Systems: The complementary diploma in Environmental Studies EVEREST Project," Proc. of the fourth conf. of the EC on (Universitaire Instelling Antwerpen), 1997. the Management and Disposal of Radioactive Waste, Luxembourg, Grand Duchy of Luxembourg, March N. CHARUE, C. ZECH, "Comportement à long terme 25-29, 1996 (1997). EUR 17543 EN, 663-680. de l'argile de Boom sous sollicitations thermiques et mécaniques: approche expérimentale et numérique," J. M. GOMIT, J. MARIVOET, P. RAIMBAULT, F. RECREO, final-year thesis, Civil Engineering (Université "EVEREST, Vol. 1: Common Aspects of the Study" catholique de Louvain, Louvain-la-Neuve), June 1997. (1997). EC, Luxembourg, EUR 17449/1 EN.

B. DEREEPER, "Développement de la maquette B. KURSTEN, B. CORNÉLIS, S. LÁBAT, P. VAN ISEGHEM, PRACLAY: test préliminaire de démonstration "Completion of the Corrosion Programme in Boom d'enfouissement des déchets radioactifs dans Clay: In Situ Experiments" (1997). EUR 17105 EN. l'argile," final-year project, Industrial Engineering A. K. LITTLEBOY, A.J. HOOPER, J.Y. BOISSON, P. DE (Institut Supérieur Industriel de Bruxelles), 1997. CANNIÈRE, L.Y. GRIFFAULT, F. PLAS, J. M. PALUT, "Site J. DOUWEN, T. FIERENS, "Elektromagnetische Characterisation: Methods and Approaches," Proc. meetmethodes ter bepaling van het vochtgehalte of the fourth conf. of the EC on the Management and in kleiformaties," final-year project, Industrial Disposal of Radioactive Waste, Luxembourg, Grand Engineering (Katholieke Hogeschool Kempen, Geel), Duchy of Luxembourg, March 25-29, 1996 (1997). 1997. EUR 17543 EN, 387-401.

G. MAES, W. STERCKX, "Instrumentatie en data- N. MAES, H. MOORS, P. DE CANNIÈRE, M. AERTSENS, acquisitie van de PRACLAY-maquette," final-year M. PUT, "Determination of the Diffusion Coefficient project, Electromechanlcs (Katholieke Hogeschool of Ionic Species in Boom Clay by Electromigration: Kempen, Geel), 1997. First Evaluation" (1997). BLG-736.

W. VERDICKT, "De interactie van europium en T. MANAI, G. VOLCKAERT, S.T. HORSEMAN, M. GHOR- uranium met Boomse Klei onder in situ omstandighe- EYCHI, "Gas Migration through Geological Media," den," final-year thesis, Chemical Bioengineering Proc. of the fourth conf. of the EC on the Management (Katholieke Universiteit Leuven), July 1997. and Disposal of Radioactive Waste, Luxembourg, Grand Duchy of Luxembourg, March 25-29, 1996 Reports published in 1997 (1997). EUR 17543 EN, 456-468.

F. BERNIER, V. LABIOUSE, J. VERSTRICHT, "Geotech- J. MARIVOET, R. BEAUFAYS, J. WALRAVENS, I. WE- nical Modelling and Instrumentation Programme of MAERE, Y. MEYUS, G. VOLCKAERT, "Geological the Connecting Gallery," contract OPD.PR 4 with EIG Disposal of Conditioned High-Level and Long-Lived PRACLAY, topical report (1997). R-3150. Radioactive Waste: Hydrogeological Modelling and Long-Term Performance Studies," NIRAS/ONDRAF C. CERTES, P. ESCALIER DES ORRES, P. GOBLET, contract CCHO-95-268/9094610 tasks 3.2, 6.1, and 6.2, A. LEVASSOR, J. MARIVOET, "EVEREST, Vol. 2b: Clay progress report, July - December 1996, Vol. 2 (July Formation, Site in France and Common Conclusions 1997). R-3139. on Clay" (1997). EC, Luxembourg, EUR l7449/2b EN. J. MARIVOET, G. VOLCKAERT, D. BUHMANN, R. STORCK, A. DIERCKX, "Boom Clay In Situ Pore Water Chemistry" T. VIENO, H. NORDMAN, "Performance Assessment (1997). BLG-734. of the Geological Disposal of Spent Fuel," Proc. of A. DIERCKX, M. PUT, P. DE CANNIÈRE, H. MOORS, the fourth conf. of the EC on the Management and M. VAN GOMPEL, L. VAN RAVESTYN, L. WANG, Disposal of Radioactive Waste, Luxembourg, Grand A. MAES, P. WARWICK, A. HALL, S. STEPHENS, Duchy of Luxembourg, March 25-29, 1996 (1997). V. PASHLEY, J. THOLEY, J. VANDERLEE, "Transport EUR 17543 EN, 647-662. of Radionuclides due to Complexation with Organic J. MARIVOET, G. VOLCKAERT, J. WALRAVENS, Matter in Clay Formations (TRANCOM-CLAY project)," I. WEMAERE, R. BEAUFAYS, "Geological Disposal of EC contract F14W-CT95-0013, progress report, January Conditioned High-Level and Long-Lived Radioactive 1997-June 1997 (1997). R-3181. Waste: Hydrogeological Modelling and Long-Term

86 Radioactive Waste and Cleanup Performance Studies," NIRAS/ONDRAF contract CCHO- M.J. PUT, P. DE PRETER, "Laboratory and In Situ 95-268/9094610 tasks 3.2, 6.1, and 6.2, progress Migration Experiments in Boom Clay," Proc. of the report, January - June 1996, Vol. 3 (February 1997). fourth conf. of the EC on the Management and R-3135. Disposal of Radioactive Waste, Luxembourg, Grand Duchy of Luxembourg, March 25-29, 1996 (1997). J. MARIVOET, G. VOLCKAERT, I. WEMAERE, J. WIBIN, EUR 17543 EN, 473-485. "EVEREST, Vol. 2a: Clay Formation, Site in Belgium" (1997). EC, Luxembourg, EUR 17449/2a EN. M. PUT, G. VOLCKAERT, F.-X. HOLVOET, L. ORTIZ, F. BERNIER, J.M. PALUT, M. DARDAINE, T. LASS- B. NEERDAEL, J. SCHNEEFUSS, "Backfilling Aspects ABATERE, E. MOUCHE, A. GENTY, F. HUERTAS, A. GENS, in Underground Repositories," Proc. of the fourth J. VAUNAT, M. VILLAR, P. LUIS MARTIN, P. RIVAS, conf. of the EC on the Management and Disposal of "RESEAL, a Large-Scale Demonstration Test for REpos- Radioactive Waste, Luxembourg, Grand Duchy of Lux- itory SEALing in an Argillaceous Host Rock," third embourg, March 25-29, 1996 (1997). EUR 17543 EN, progress report, May-October 1997 (1997). R-3216. 326-340. M. PUT, G. VOLCKAERT, L. ORTIZ, F. BERNIER, L. NOYNAERT, G. VOLCKAERT, P. DE CANNIERE, F.-X. HOLVOET, J. M. PALUT, M. DARDAINE, Th. LASS- P. MEYNENDONCKX, S. LABAT, R. BEAUFAYS, M. PUT, ABATERE, E. MOUCHE, A. GENTY, F. HUERTAS, A. GENS, M. AERTSENS, A. FONTEYNE, F. VANDERVOORT, J. VAUNAT, M. VILLAR, P. Luis MARTIN, P. RIVAS, L. WANG, "The CERBERUS Project: A Demonstration "RESEAL, a Large-Scale Demonstration Test for REpos- Test to Study the Near-Field Effects of a HLW-Canister itory SEALing in an Argillaceous Host Rock," first in an Argillaceous Formation," EC contract FI2W-CT90- annual report, May 1996-April 1997 (1997). R-3200. 0003B, final report, July 1990-December 1996 (1997). R-3166. H. R. THOMAS, A. GENS, G. VOLCKAERT, M. V. VILAR, Ch. IMBERT, "Testing and Modelling the Behaviour R. ODOJ, P. FILSS, G. GASPARY, J. KUHNE, R. MANDOKI, of Unsaturated Argillaceous Backfill and Sealing M. BRUGGEMAN, P. VAN ISEGHEM, "Determination of Materials," Proc. of the fourth conf. of the EC on Fissile Material by Neutron Transport Interrogation," the Management and Disposal of Radioactive Waste, final report (1997). EUR 17560 EN. Luxembourg, Grand Duchy of Luxembourg, March L. ORTIZ, "Etudes de performance a long terme. 25-29, 1996 (1997). EUR 17543 EN, 354-368. Analyse des donnees hydrauliques dans la zone P. VAN ISEGHEM, G. BRUNEL, Ch. LIERSE, A. MORALES, perturbee autour du laboratoire souterrain HADES," R. ODOJ, F. TROIANI, M. HUGON, "European Network NIRAS/ONDRAF contract CCHO-95/268, KNT90 94 610, of Testing Facilities of Radioactive Waste Packages," Annex 6, task 6.1 (1997). R-3162. annual report 1995 (1997). EUR 17559 EN. L. ORTIZ, G. VOLCKAERT, P. DE CANNIERE, M. PUT, J. VERSTRICHT, F. BERNIER, "Thermal Modelling of the A. SEN, S. T. HORSEMAN, J. F. HARRINGTON, M. IMPEY, Mock-Up," contract OPD.PR 2 with EIGPRACLAY, topical S. EINCHCOMB, "MEGAS: Modelling and Experiments report (1997). R-3124. on Gas Migration in Repository Host Rocks," final report, phase 2 (1997). EUR 17453 EN. W. WACQUIER, E. HOSKENS, L. SANNEN, A. DANIELS, D. HUYS, P. VAN ISEGHEM, "Leaching Behaviour of M. PUT, ed., "Geological Disposal of Conditioned Radionuclides from Homogeneous Cemented PWR High-Level and Long-Lived Radioactive Waste. Tasks Waste," final report for 1992-1996 (1997). R-3196. 1.2 to 5.2 and Operation and Maintenance of the URF," NIRAS/ONDRAF contract CCHO-95/268, KNT9094610, progress report, July - December 1996, Vol. 2 (of 2) (1997). R-3139.

Waste Disposal 87 BE9900074

Roland CARCHON Safeguards

Scientific staff AFEGUARDS is the generic wording for the The detection opportunities in sea ports as well Peter BAETEN S measures ensuring that nuclear materials as the needs and boundary conditions as iden- Michel BRUGGEMAN are not diverted from peaceful activities to the tified in work package WP01 provided the start- Roland CARCHON manufacture of nuclear weapons or other nu- ing point for the investigations. We kept in Wim DE BOECK clear explosive devices, within the context of mind that quantification of the content has Robert MANDOKI international treaties. These measures com- only a second-order priority: first a warning Klaas VAN DER MEER bine disciplines such as international law, sta- has to be issued about the presence of non- tistics, politics, but also analytical chemistry declared materials, and then a refined examina- Supporting staff and nuclear physics. Nondestructive assay tion could be applied with a proper identifica- Jozef GERITS techniques are used throughout the nuclear tion and quantification of the source. Contra- Nadine VERSTRAELEN fuel cycle for the verification of special nuclear band and accidental transport of contaminated material, besides process control. They are material must of course be distinguished. based on the detection of the radiation emitted by the radioisotopes. Safeguards activities Signatures of nuclear and radioactive materi- at SCK-CEN answer internal needs, support the als consist of spontaneous and induced radia- Belgian Authorities, and support the IAEA (with tions consisting essentially of gamma rays and Euratom as a partner) to improve the efficiency neutrons. This means in practice that, if radio- and to increase the effectiveness of safeguards. active materials or sources are to be detected, the detection method has to be sensitive to gamma rays: neutron detection alone is inad- Objectives equate. This distinction will affect the proper • to contribute to a prevention of the prolif- choice of the detection device. eration of nuclear materials by maintaining an up-to-date expertise in the field of safe- A desk research on detection techniques for guards and providing consultancy and guid- nuclear and radioactive materials used in other ance, and scientific and technical support to modes of transport (rail, road, air, and others) the Belgian Authorities and nuclear indus- will serve as reference for the application of tries; detection techniques in sea ports. Attention is paid to pedestrian and vehicle monitors. In- • to improve the qualification and quantifica- deed, in view of the volumes currently han- tion of nuclear materials via nondestructive dled, we decided to focus on the detection of assay. nuclear and radioactive materials in containers. These are loaded on trucks that must pass Illicit trafficking of radioactive and fissile a gate for administrative matters. The gate materials at sea ports In a contract with can be equipped with a monitor through which the EC (4.1020/D/96-007), we collaborated with charged trucks must pass. ECN Petten and Maritime Systems Technology (The Netherlands) on a "Feasibility study on the The analysis of detection techniques for use in detection and monitoring systems and proce- sea ports starts with the identification of the dures to prevent illicit trafficking of radioactive type of materials to be detected and the follow- and fissile materials at sea ports in EU member ing boundary conditions: type of cargo, pack- states." The contract was split in three, work age type, quantity of nuclear or radioactive packages: investigation of existing situation materials, radiation type, dose rate, and avail- and user requirements (WP01), investigation of able measuring time. The technical character- detection techniques and systems (WP02), and istics and detection capabilities of the detec- development of system layouts for detection tors and their boundary conditions are then and monitoring (WP03). studied. This review includes the following detection and monitoring characteristics: type of WP02, which was the responsibility of SCK-CEN, detectors, location of the detectors, use of pas- aims to give an overview of existing techniques sive or active detection techniques, assessment and practical methods for the detection and of signal components, counting rates, signal monitoring of nuclear and radioactive materi- data treatment, background signal strengths, als, including techniques under development. and decision algorithms.

88 Radioactive Waste and Cleanup Monte Carlo calculations are made to confirm or deny certain contradictory and conflicting findings in the literature. Passive and ac- Presentations delivered in 1997 tive systems are investigated for neutrons, and G. BlGNAN, M. BRUGGEMAN, P. BAETEN, P. CHARD, gamma rays are only considered in the passive mode. S. CROFT, A. DODARO, S. GUARDINI, M.S. Lu, A. MASIANI, S. NONNEMAN, D. PARKER, R. REMETTI, M. SWINHOE, "ESARDA-NDA Working Group Bench- Spent fuel detectors We have given sup- mark Exercise," 19th Annual symp. on Safeguards port to Euratom's verification programme of and Nuclear Material Management: Montpellier, spent fuel and fresh MOX fuel in reactor stor- France, May 13-15, 1997. Proc, EUR 17665 EN. age ponds, by manufacturing Fork detectors for PWR and BWR fuel assemblies and for fresh K. VAN DER MEER, R. CARCHON, "A Safeguards PWR MOX fuel. We also ensured maintenance, Approach for a Closed Geological Repository for repair, test, and upgrading of the existing Fork Spent Fuel," IAEA symp. on International Safeguards: detectors, to increase their performance and Vienna, Austria, October 13-17, 1997. Proa, reliability. IAEA-SM-351/102.

Generic Studies on the Fuel-Cycle Evolu- tion We continued on a modest scale the programme looking for reasonable and useful applications in civil nuclear reactors of the plutonium stocks existing in the world, whether they originate from civil applications or from the military circuit. If this plutonium is brought into the civil circuit, it will have a serious impact on the activities of national and international control organizations.

The activities were limited to a follow-up of the literature concerning general information about most commercial nuclear facilities, in view of an updating of the database of the code REACTOR, which was developed to study the build-up of plutonium stockpiles originating from the civil circuit. This database contains information about the reactors, their current status, expected lifetime, energy production, spent fuel discharges, and plutonium content. It also contains data about planned nuclear reactors, repository sites, reprocessing, and MOX production facilities.

Safeguards 89 BE9900075

Léon VANDEVELDE Radiochemistry

Scientific staff A FIRST REQUIREMENT for the safe process- ratories (SCK'CEN, TŰI, and PSI). SCK'CEN car- Peter DE REGGE /jLing and handling of radioactive materials ried out the analyses of the base programme Léon VANDEVELDE (fissile material, spent fuel, radioactive waste) (except for 99Tc) on one sample from TUI and Mireille GYSEMANS in the nuclear industry is a good characteriza- both samples received from PSI. In the exten- Stefaan VAN WINCKEL tion of the radionuclides present. This charac- sion of the programme, the 90Sr, 106Ru, 125Sb, Daniel HUYS terization requires reliable radiochemical and 147Pm, and lD5Gd content was determined in Renatus BODEN radioanalytical procedures that allow accurate four samples of dissolved irradiated fuel. To Peter THOMAS identification and quantification of the radio- this end, new analysis methods had to be de- Frank VANDERLINDEN nuclides. veloped for 147Pm and 135Gd. (The detailed re- Jozef LAEREMANS sults are all proprietary to the programme par- Karel VAN GILS ticipants.) As a part of the extension, two more Objectives The laboratory aims at provid- BWR MOX samples were successfully dissolved ing state-of-the-art measurement and separa- Supporting staff in a shielded cell, using the standard disso- tion methodologies to comply to customer re- lution procedures for burnup measurements. Luc GELENS quirements, in order Maureen GROMMEN The dissolver off-gas was directed through a Edward HELSEN a to provide reliable and accurate methods series of alkaline wash bottles to collect the io- Magda OOMS for the identification and quantification of dine for further analysis. André STUBBÉ alpha- and gamma-emitting radionuclides Ludo VANDENWEYER in a wide variety of matrices; The intercomparison with sample exchanged Eis VERHEYEN from the two other European laboratories dem- • to develop and to optimize the separa- onstrated the validity of our approach. tion schemes to meet the requirements for preparing sources for these measurement techniques; Anion exchange A novel anion exchanger consisting of a resin embedded in porous sil- • to maintain and improve the existing qual- ica beads shows very promising properties for ity-assurance procedures in the framework the recovery of actinide elements from spent of the Beltest accreditation. fuel. On request of the Institute of Research and Innovation (Japan), the resin was tested for plutonium separation at SCK-CEN. Differ- ARIANE The ARIANE project was initiated ent column experiments were carried out in a by Belgonucleaire to obtain extensive data for glove box and the separation behaviour and re- the isotopic composition of high-burnup LWR covery of Am(III) and Pu(IV) are being studied. fuels. These data are necessary for regu- The final measurements will be performed in latory and safeguards purposes, as well as early 1998. for criticality control, radiation shielding, and shipping-cask design. Moreover, the licens- Finally, besides analyses for the above research ing of disposal facilities requires the knowl- programmes, we performed analyses for other edge of transplutonium isotopics for criticality SCK-CEN departments and for the industry. A and safety reasons. Selected isotopes (see SCK- total of 320 analysis on a wide variety of low CEN's 1996 Scientific Report) were analysed in to highly radioactive material (nuclear fuels, low-enriched uranium and MOX fuel rods from resins, waste, solids or samples in solution) BWR and PWR reactors. were carried out in 1997. In 1997, we developed a new method to determine 237Np and applied it to all samples in Quality assurance The aim of the labo- order to complement the analyses of the base ratory is to perform accurate analyses within programme. We delivered the first report, in- the shortest possible delays through a constant cluding all the methods of analysis used in the performance evaluation of the equipment and base programme, the corresponding results, the operators. We develop new applications and an extensive uncertainty evaluation. to answer customer needs. By submitting selected methods to the accreditation by Beltest, Samples of dissolved irradiated fuel were ex- we are zealous to maintain and develop the changed between the three participating labo- quality of our work.

90 Radioactive Waste and Cleanup The validation of the new ion chromatograph, planned for 1997, was achieved for normal aqueous samples. The validation for clay- water samples containing humic acids needs further experiments and will be finalized at the beginning of 1998. It will then be fitted in a glove box for alpha-contaminated samples. We intend to include the method in the scope of accreditation.

The qualification of the Thermal Ionization/ Mass Spectrometer (TI/MS) has been finalized. It is now fully operational for the isotopic analysis of MOX fuel.

The Inductively Coupled Plasma/Mass Spec- trometer (ICP/MS) for glove box applications was purchased and delivered in December. It will be installed at the beginning of 1998. The validation procedure for the determination of impurities in nuclear fuels will be started immediately.

Many quality-assurance documents have been revised. The Beltest audit will take place in Jan- uary 1998.

Scientific partners Paul Scherrer Institute (PSI) — Transuran Institut (TUI)

Presentation delivered in 1997

Ch. DE RAEDT, S. VAN WINCKEL, J. BASSELIER, Th. MALDAGUE, "Validation of Actinlde Cross- Sections for LWRs in the Framework of the ARIANE Programme: Work Performed by SCK-CEN and by Belgonucleaire," Int. conf. on Nuclear Data for Science and Technology: Trieste, Italy, May 19-24, 1997.

NEXT PAGE(S) left BLANK Radiochemistry 91

BE9900076

Pol GUBEL, Jean DEKEYSER, Jan VAN DER AUWERA Refurbishment of BR2 (Phases 4 and 5)

Scientific staff CEN's HlOSt impor- ing, procurement of equipment, setup of ex- Hamid AIT ABDERRAHIM JLtant nuclear facility. It has been operated ecutive procedures, and detailed planning for Baudouin ARIEN since 1963 in the framework of many inter- the next phases. Phase 4 covers the actual Philippe BENOIT national programmes concerning the develop- realization of all the refurbishment works as Gilbert BERGMANS ment of structural materials and nuclear fuels planned during the long shutdown of the re- Rachid CHAOUADI for the various types of nuclear fission reac- actor (from mid-1995 to end of March 1997). Bernard COUPE tors and for fusion reactors. The qualities and Phase 5 completes the remainder of the refur- Antoon DE BOCK performance of the reactor also designated it bishment works which may be deferred until Jean-Luc DELCOUX for performing experiments aiming to demon- after the restart of BR2 in April 1997. Stefan DECLERCQ strate the safety of nuclear cores. Jean DEKEYSER All refurbishment works of Phase 5 foreseen Charles DE RAEDT The facility was shut down at the end of June initially in the refurbishment action plan 1998 Albert FABRY 1995 for an overall refurbishment programme and all new activities initiated to comply with Pol GUBEL covering all aspects necessary to compensate the requirements of the Licensing Authorities Simone HEUSDAINS for the ageing of the installations, to enhance should be completed respectively by mid-1998 Frank JOPPEN the reliability of operation, and to comply with and by late 1999. Edgar KOONEN modern safety standards. After an extensive Georges MINSART preoperational non-nuclear and nuclear testing Jose VAN DE VELDE phase, it was restarted according to plans in Achievements Upon completion of Phase 2 Marcel NOEL April 1997 for its first irradiation cycle. (detailed study), we defined an action plan cov- Bart SMOLDERS ering Phases 3 and 4 (and also Phase 5). This ac- Jan VAN DER AUWERA tion plan encompasses, on the one hand, all the Leon VANDEVELDE Objectives For Phase 4 of the refurbishment activities related to the safety and reliability of Peter VAN DE VELDE programme, the facilities and, on the other hand, those related to the normal maintenance. Jan VERMUNT • to carry out the various activities prepared Marc VERWERFT during Phase 3 (detailed design and prepa- At the request of the Licensing Authorities, ad- Alfons VERWIMP ration) of the programme. Marcel WEBER ditional assessments were initiated at the be- Jean-Marie CORBISIER • to plan the activities required to allow a re- ginning of 1996 and pursued in 1997: the leak- Camiel DECLOEDT actor startup at the beginning of April 1997. tightness of the subpile room and the assess- Richard LIESENBORGS ment of the seismic vulnerability of the instal- Andre SCHOUTEN For Phase 5 of the refurbishment programme, lations. Fernand MALLANTS * to complete the remainder of the refurbish- We also initiated a study to provide the storage Hans OOMS ment works (previously foreseen in the re- channel with a purification circuit: the detailed Jean-Louis PUZZOLANTE furbishment action plan) which may be de- engineering was performed in 1997 and the re- Filip RAMAEKERS ferred until the restart of BR2 in April 1997; alization should start at the beginning of 1998. Frans SCHELLES • to carry out the extra studies and upgrad- Lucien THIEREN ings required by the Licensing Authorities. The sections below present the main achieve- Marcel VAN BALEN ments for Phases 4 and 5 in 1997. Willy CLAES Jan DIERCKX Programme The overall refurbishment Roger STYNEN programme comprises five distinct phases, of Perspectives for 1998 Our objective for Karel LASKA which the detailed assessments according to 1998 is to complete Phase 5 of the refurbish- Angelo AQUINO the stated objectives concern only the sec- ment programme. Only those actions resulting Eduard GEYSEN ond. Phase 1 (completed in early 1992) had from requirements of the licensing authorities Marcel VAN HOOLST identified the critical plant items and systems and the construction of a new purification cir- Guido BOSSi to be studied in detail in Phase 2. Phase 3 cuit for the storage channel will be pursued un- Willy BEETS (from mid-1994 to about mid-1996) addressed til the end of 1999. Frans DE MULDER the preparatory activities: detailed engineer- Michel VAN HOOF Willy CORTHOUTS Yvan POULEUR Karel VAN EYNDHOVEN Shroud sampling To characterize better the Marcel VAN HOOF Bernard VERBOOMEN Gaston MESKENS vessel wall of BR2, we cut samples of the shroud Simon CLAES Bernard PONSARD Jean-Marie BAUGNET by electroerosion in 1994. (The shroud that

94 BR2 Operation constitutes a cooling jacket close to the vessel There are problems in calculating the heat wall is made of the same material as the vessel exchange for the natural-convection regime itself, namely aluminium 5052-0.) The sam- in RELAP5.mod3 ,ic. This flow regime requires ples taken from the weld were however found a more detailed nodalization, modelling the to be too few for the envisaged extensive test real concentric rings instead of the six fuel- programme. element rings modelled in only one vertical rectangle. In May 1997, we started a new sampling cam- The RELAP model for heat conduction is one- paign. With a specially designed supporting dimensional (in the radial direction): RELAP structure, fixed in the reactor pool, we cut two does not calculate the heat transfer in the plates of 140 x 140 mm comprising material of vertical axial direction (only for the reflood a longitudinal weld of the shroud, located at model). 180° from the one from which we took a plate of the same size in 1994. During the two cam- The energy produced in the fuel also seems paigns, a total of six such plates were cut off too large, although the power history was the shroud, out of which three comprise weld respected. This observation requires more material, yielding numerous test specimens, investigations, for example, to characterize both from the base material and from the weld the specific decay heat of the BR2 fuel. material. Samples from the first shroud sampling are being irradiated since the restart of BR2 (accelerated irradiation to increase the lead Ergonomy An ergonomy study of the two factor). A second irradiation basket will be BR2 control rooms, conducted in 1995 with Bel- loaded early next year. The first postirradia- gatom, led to recommendations and the defi- tion examination is foreseen around the turn nition of an action plan. In 1997, we studied, of the century. realized, and installed a new desk for the reactor control room, we studied and realized an emergency control panel, to be installed in Reactor vessel We have established a early January 1998, and we realized a new in- proactive surveillance programme for the alu- tegrated primary temperature regulation, to be minium vessel. This will allow us to foresee implemented in 1998. the evolution under further irradiation of the mechanical and metallurgical properties of the base metal and weld material. Regulating rods The two newly designed regulating rods were operational for starting The stress-intensity factors associated with the up the reactor in April 1997. Experience dur- indications detected during the in-service in- ing the three operating cycles of 1997 was very spection were evaluated: the adopted accep- positive. tance criteria are respected and there is no crack growth to be feared. Automatic block valves The Automatic Block Valves (ABVs), which are essential pri- RELAP studies An experimental test per- mary safety organs, have been made more re- formed on the BR2 primary cooling circuit in liable. The control and actuation systems have 1963 was simulated with the RELAP code. It been completely redesigned and modernized. consisted in a shutdown of the primary pump The reliability could only be further enhanced with a recording of the fuel cladding tempera- by a doubling of the valves themselves; this op- tures at different positions in the vertical axis. tion was ruled out as the achieved level of confidence is judged acceptable. The experimental and theoretical results are in good agreement in steady state, but show sig- The closure time of the ABVs of the primary cir- nificant discrepancies near the core midplane cuit has been considerably reduced, to prevent when natural convection occurs. Sensitivity any release of radioactivity outside of the con- calculations show that the discrepancies can tainment building even in the case of the most been induced by different factors. severe Loss-Of-Coolant Accident (LOCA).

Refurbishment of BR2 (Phases 4 and 5) 95 A comprehensive testing and commissioning sages of the different channels. In case of programme was carried out. An additional clo- LOCA, the water leakage of the reactor vessel sure command of the ABVS will be incorporated is compensated by the pool water, thanks to in the foreseen emergency control panel. the automatic opening of an ABV. The SPR must therefore be tight under a 23-metre water pressure to guarantee that the reactor core will re- Seismic analysis The seismic analysis main under water in case of LOCA. of the BR2 installations, completed in 1997, showed that most of the installations can with- In the framework of the BR2 refurbishment, dif- stand the reference earthquake of 0.1 g with a ferent tasks were carried out to guarantee the Regulatory Guide 1.60 spectrum. It covered the tightness: detailed drawings, inventarization, reactor building, the reactor pool, the reactor and control of the SPR penetrations; reinforce- vessel, and the storage channel for spent fuel. ment of the supports on the ventilation ducts The two components that would not withstand of the SPR, placement of isolation valves, and the reference earthquake are the primary loop, hydraulic testing; development of an easy and which lacks horizontal restraints, and the ve- quick procedure to test the tightness, to mea- hicle air lock of the reactor building, which has sure the global air leakage accurately, and to insufficient bearing and could cause an extra localize the position of the leakage with low air load on the containment building, leading to over- and underpressure in the SPR; develop- a leak. Additional restraints for the primary ment of a fluid model to convert the air leakage loop have now been designed and will be con- into water leakage and to extrapolate to high structed in 1998. Additional bearing for the pressure; reinforcement of the CALLISTO pen- vehicle air lock will be designed in 1998. etration and isolation with silicone; deep injection of polyurethane foam in the principal During an earthquake, damage could also re- cracks of the concrete to reduce the global leak- sult from the fall of heavy components. The age because of the nonsatisfactory injection of polar crane and the hot cell are calculated to epoxy resin; control of the tightness of all the resist, but several installations are likely to steel doors; simplified safety analysis of the cause damage. Though we completed much modifications on the ventilation system. of the modification work required, such as fix- ing ventilation ducts and shield walls, two areas of concern remain: the ventilation duct The situation of the SPR is now the following: bridge and the upper structure of the machine the final safety report has been published; the hall. Failure of the ventilation duct bridge drawings and flow sheet are correct; the pen- could damage the isolation valves of the reac- etrations are correctly numbered and labelled, tor building, so we will separate the ventilation and are tight; the tightness and the resistance duct bridge and the valves; we will design these of the other components of the SPR are under modifications in 1998. The upper part of the control; the leakage is reduced; the first injec- machine hall could also collapse under the ref- tions of polyurethane were very promising; the erence earthquake, thereby causing the fall of tightness can and must still be improved; the heavy pieces in the storage channel. Unfortu- tightness can be checked easily and regularly; nately, this construction cannot be made resis- the control instrumentation is improved; and tant to the reference earthquake. The possible the procedures before the start of the reactor consequences of such an event will be studied have been modified to guarantee the correct in detail, and judged together with the proba- closure of the manhole and the doors. bility of earthquake.

Demineralized water The demineralized- Subpile room The SubPile Room (SPR), situ- water plant must provide the demineralized ated under the reactor vessel, gives an easy ac- water for the primary and secondary loops of cess to the lower reactor cover. During the op- BR2, the reactor and storage pools, and other eration of the reactor, it must be watertight to marginal uses. The capacity of the plant is guarantee safety in case of a small or medium primarily determined by the secondary loop, LOCA on the reactor cover or through the pas- which requires 100 m3 of water per hour when

96 BR2 Operation the reactor is operated at high power. The of them are provided with a motor and a re- other circuits together require about 1 m3 per duction); a new electrical distribution board hour. on the bridge, fed by electric supply cables in a railroad; a precise positioning of the hook The most significant modifications, executed in measured with two lasers with displays on the 1996, were to adapt the installations to use mo- bridge; and a remote-control system for driv- bile demineralization units installed on trailers ing the bridge. and hired from a specialized company. The installation has been put in service in 1997. Flow trap The flow trap, installed on the Because the raw water was stored in a buffer primary cooling circuit of the reactor, has two tank, the iron present in the form of ferrous functions: the continuous removal of gases (es- iron oxidized to ferric iron, which is extremely pecially air at the filling of the primary circuit) insoluble and precipitates during water stagna- and an antisyphon working designed to avoid tion, causing inferior use of the demineraliza- draining of the reactor vessel and reactor pool tion units. To avoid the temporary storage of in case of LOCA. Both functions were assem- raw water, the frequency control on two pumps bled in one device, the operation of which was was adapted so that it is now possible to adapt not guaranteed because the removal of gases the flow to the water consumption, rendering demands a small outlet and the antisyphon the buffer tank for raw water unnecessary. working demands a large air inlet. To enhance its capabilities and reliability, we installed a Transfer chute The transfer chute allows new concept where both functions are sepa- the transport of irradiated fuel elements and rated and which allows regular testing and con- experiments between the reactor pool and the trol of the operating conditions. storage pool or hot cell. To enhance its reliability and as a result of a recent incident Mechanical works The following important caused by malfunctions, the drive and opera- mechanical works were carried out in 1997: tion units have been completely renewed. The we renewed the driving of the reactor pool most important modifications are a new con- bridge; renewed the drive and operation units cept of the gears attachment to the drive mech- of the transfer chute; installed two frequency- anism and the replacement of the vertical drive regulated pumps for the demineralized water axle; the installation of a digital position en- plant; installed a new flow trap on the primary coder to control the rotating part of the trans- cooling system of the reactor; renewed impor- fert chute; new detection switches on the po- tant parts of the heating and ventilation instal- sition of the reactor pool valve (closed or open) lation; inspected the 1" and 2" penetrations and the position of the expansion joint in the on the primary circuit, as a result of the rupture storage pool; the installation of a new pressure incidentin 1997; insulated the pressurizer and indication to control the pressure equilibrium preheaters T4-801 andT4-802; and replaced the between transfer chute and reactor pool, and seals of the primary pumps J4-402 and J4-403. transfer chute and storage pool; the renewal of the complete electrical switchboard and a new control panel with a programmable logi- Instrumentation The original pneumatic cal controller. instrumentation installed at the construction of the reactor and the one which had an automatic action on the reactor were replaced Reactor pool bridge The pool bridge, by electronic instrumentation. To this end, mounted above the reactor pool and running we installed 46 new penetrations containing on wheels along the parapet, provides a plat- 290 electrical connections through the wall of form for installing and removing fuel elements, the containment building, installed electrical control rods, and experiments; it is equipped power units (220 VAC, 24VDC), placed instru- with a 360 kg hoist device. We renewed the mentation and feeder cables as well as distri- complete drive installations, and in particu- bution boxes, etc. lar the driving mechanism, now equipped with four wheels on each side of the brigde (four

Refurbishment of BR2 (Phases 4 and 5) 97 Before installation, each new instrumentation The new purification circuit should begin to be has been tested and calibrated. After the in- installed in 1998. stallation, all modified instrumentation loops have been completely tested during the pre- Fire protection A new fire protection sys- operational non-nuclear testing campaign of tem was put into service in 1997 in the reactor the reactor, before startup. building and in the diesel building. It has been approved by an authorized organization (NVBB) Electrical installation The DC network in accordance with the Belgian regulation (NBN (110 VDC) is used for such applications as sig- S21-100) and includes components for both ac- nalling, alarms, and evacuation. To increase tive protection (detect a fire early) and pas- its reliability, the most important boards have sive protection (prevent the spreading of the been equipped with an extra battery/rectifier fire). Moreover, compartmentalization works unit. These units have been delivered and in- already started in the other BR2 buildings, and tailed in 1997. Configuration, testing, and cou- the ventilation building and substation were pling with the existing network are in progress. equipped with a fire-detection system.

To prevent the loss of vital network 380 VAC, Regarding active protection, optical smoke de- two diesel engines are always coupled with it. tectors and manual push-buttons have been in- When both diesel engines do not take over dur- stalled in the reactor building. The compo- ing a voltage cut-off, they cannot be restarted. nents are connected with two fire detection Therefore, we installed a new diesel engine, units, themselves connected to four control which can be started manually. This new en- panels (RCR, MCR, HIG, surveillance BR2), the last gine can also be coupled with several important two of which allow a quick visual survey of the electrical switchboards. The most important situation. We also installed an automatic fire- works are now finished but testing, operating extinguishing system coupled to a detector in procedures, and training of the personnel are the engine room of the lift in the reactor build- still in progress. ing, and optical smoke and flame detectors in the diesel building. The latter double-detection system is connected to an autonomous and au- Purification A microbiological and chemical tomatic fire-extinguishing system (deluge). pollution incident occurred in the storage circuit for the storage channel during the summer For passive protection, we started compart- of 1994 and could not be solved by the exist- mentalizing the BR2 reactor building. The ing channel purification circuit common to the glasses of the reactor control room have been storage channel and the reactor pool. SCK«CEN replaced by fire-resistant glass and the doors in then decided to study and implement a new pu- the reactor building have been replaced by fire- rification circuit for the storage channel alone. resistant ones. Complete compartmentalization (between the second and the third floors of The results of the study, made by Tractebel, the reactor building, and of the reactor control concluded that this purification circuit should room) is scheduled in 1998. have a flow of 60 m3^"1, two pumps in parallel, one filter (1 um) with an automatic cleaning circuit (PALL BFP-4 Septra), one uv filter with 254nm wavelength, and two ion exchangers (floating beds), one with 1100L cations and one with 1500L anions. The treated water Scientific partners Belgatom — GEC Al- 1 should have a conductivity of 0.5 uS-cm" and sthom — Atomic Energy Authority (AEA Technology) — 1 a COD lower than O.Smg-1" . The waste pro- Wetenschappelijk en Technisch Centrum voor het 3 duction is about 30 m of chemical waste (at Bouwbedrijf/Centre scientifique et technique pour 3 this moment, we produce about 100 m ) and la construction (WTCB/CSTC) — Compagnie generate 3 10 m of soft waste (at this moment, we pro- d'electricite (CEGELEC) — Elektrische Nijverheid 3 duce about 200 m ) per year. The overall cost Installaties (ENI) — Raadgevende ingenieurs voor amounts to about 40 MBEF. technische uitrusting van gebouwen (MARCQ & ROBA)

98 BR2 Operation

BE9900077

Da RUAN

Fuzzy Logic and Intelligent Technologies in Nuclear Science

Scientific staff TJ LINS, an acronym for Fuzzy Logic and Intel- and be only a step towards future FL appli- Da RUAN it ligent technologies in Nuclear Science, has cations in nuclear power plants. However, li- Xiaozhong Li been recognized since 1994 as a unique inter- censing this technology as a nuclear technol- national forum on Fuzzy Logic (FL) and intelli- ogy could be more challenging and time con- gent systems for nuclear science and industry. suming.

The main task for FUNS for the coming years Programme Started at the beginning of is to solve many intricate problems pertain- 1995, both fuzzy software and hardware spon- ing to the nuclear environment by using mod- sored by OMRON Electronics NV (Belgium) were ern technologies as additional tools and to successfully implemented in BRi. To be al- bridge a gap between novel technologies and lowed by the safety authorities to carry out the industrial nuclear world. Specific prototyp- our on-line fuzzy-control experiment at BRI, we ing of Fuzzy Logic Control (FLC) of SCK«CEN's made several off-line tests and a safety on-line BRi research reactor has been chosen as FLINS' test scheme. first priority. This is an on-going R&D project for controlling BRI'S power level. The project started in 1995 and aims to investigate the In the meantime, we have constructed a demo added value of FLC for nuclear reactors. In this model which is not only suitable for most con- framework, the availability of BRi greatly sim- trol algorithm testing experiments, but also for plifies the effort to validate the model descrip- simulating the power control principle of BRi. tion used. This allows us to concentrate on the optimal implementation of the overall control. Fuzzy logic application to BRi The internal R&D project on FLC of BRI was run according to planning: the hardware interfaces were de- Objectives Based on the progress of the BRi signed and made compatible with the OMRON project (see SCK-CEN's 1995 and 1996 Scientific hardware and with BRI; the experimental re- Reports), we are currently using a permission sults of both the existing control system and from AIB-Vingotte Nuclear to perform the real the FLC proved that the designed rule-base and FLC experiment on-line on BRI. We aim to ben- hardware interfaces provide a solid basis for efit the existing control systems by applying FL the further progress of this ongoing project. as an additional tool for both the safety and economic aspects in nuclear power plants. Based on the present research results, we are now starting the real FLC experiment on-line at The FLINS project reflects a special application BRI. We aim first to realize a real closed-loop domain of FL related to the need for the highest control at BRi, to be sure that both hardware safety standards in nuclear areas. Research in- and software work properly. To ensure the volved in this project will provide a real test maximum safety of the FLC experiment for the

(1, fine control)::

Figure 1 Electrical circuit connection of Fuzzy Logic Control (FLC) and Normal Control (NC).

100 Exploratory R&D reactor, we designed an automatic switch be- Fuzzy-control demo model The demo tween the FLC experimental operation and the model, based on the working principle of BRI Normal Control (NC) operation. The switch can power-level control, was constructed to show only be connected, automatically, with either the possibilities of using fuzzy-rule-based sys- FLC or NC, to keep at least the NC of BRi (Fig. 1). tems and to demonstrate the added value of practical applications of FLC. We proceeded Following the above step, we change the de- in three steps. The very first approach was a sired value in two directions (increase or de- normal fuzzy-control algorithm based on the crease) when the system becomes stable. We Mamdani model. Our second step was to work then further observe the reaction of the sys- out a PID algorithm and compare the two ap- tem, namely the output power of the reactor proaches. The results have shown that fuzzy and that of FLC. We however only consider a control is more flexible, more robust, and eas- reasonably low power level at BRi during this ier to update than the PID control. As a third very first test, which is acceptable because such step, our demo model can now simulate BRl's an experiment follows exactly the same work- exact control behaviour. That is, the water- ing principle as at the high power level. level control of the demo model is comparable with the power-level control of BRI. Our As shown in Figure 2, our safety design of FLC current research in the demo model permits at BRi requires extra support software. After further implementation of both fuzzy hard- turning the power on, the PLC always first reads ware and software at BRI. Moreover, one of the each input signal from the A/D unit. Then it self-learning systems, the automatic rule-base checks each signal against its corresponding built-up for BRi control, can be copied with this alarm boundary. If any of them is outside the demo model. boundary, it stops running and NC automatically takes over. Otherwise, it proceeds with An advanced fuzzy-control algorithm, called outputs to control the A-rods and C-rods. Since adaptive fuzzy control, is self-learning. Com- this process is run continuously during the ex- plex conditions, where fuzzy-control rules are perimental period, the FLC experiment at BRi difficult to define, require a dynamic controller will be safe. For extra safety, we set the alarm system of self-regulating fuzzy-control rules. boundary at a smaller value than that under Basically, the system can judge its former per- NC operation. formance and adjust control rules by itself. This algorithm has been successfully applied After having experienced off-line fuzzy-control to the demo model, showing a better perfor- test at BRi, we now foresee an on-line fuzzy- mance than normal fuzzy control when the control experiment at BRi for 1998. All tested fuzzy-control rules are not good. In the exam- algorithms in the demo model will be applied ple of Figure 3, the water level starts at 0 cm in the BRI project as soon as permission is and increases toward a set value of 20 cm, first granted, first in steady-state conditions, then under the analytic controller (near 0 cm), then in dynamic ones. under the fuzzy controller.

Actual power i>:; lofA-rd'cis::::: lOesireci power ^Pd IReactorperiod :P;6:sitiorl:of A-rbdsi -;w-'fc Ppsitiisri!

Figure 2 Extra yes;/'Any out of\no support software Normal control Fuzzy control i boundary? for safety design :{fuzzy: Cont;ii>l off) of FLC at BRI.

Fuzzy Logic and Intelligent Technologies in Nuclear Science 101 Following FLINS'94 and FUNS'96 (the first and Level I second international FUNS workshops), FLINS'98 (September 14-16, 1998) will aim to bring to- Fuzzy adaptive control gether scientists, researchers, and people from industry and to introduce the principles of intelligent systems and soft computing such Fuzzy control _ as FL, neural networks, genetic algorithms, and any combination of the three, knowledge- based expert systems, and complex problem- solving techniques within nuclear industry and related research fields. The FLINS'98 proceed- ings will be published as a book under the ti- tle Fuzzy Logic and Intelligent Technologies for 10: Nuclear Science and Industry (World Scientific, •Tirn:C[rninutes] iM.li Singapore).

Figure 3 Given a set of bad rules, the control effect with the learning function is much better than that without it. Scientific partners Universiteit Gent (UG) — Taking advantage of the demo model as a test Physics and Electronics Laboratory (TNO) bed for new algorithms, especially learning ones, we will further research a new algorithm Sponsor European Technical Centre (ETC-OMRON) based on neural networks.

Nuclear safety: the special issue of Fuzzy Logic and Intelligent Systems The spe- Books published in 1997 cial issue Nuclear Safety was edited upon in- vitation by FLINS and published in the Korea X. Li, D. RUAN, "Novel Neural Algorithms for Journal of Fuzzy Logic and Intelligent Systems. Solving Fuzzy Relation Equations," in: D. Ruan, ed., Also, FLINS has been invited to edit the special Intelligent Hybrid Systems: Fuzzy Logic, Neural issue Intelligent Systems at FLINS'96 for the In- Networks, and Genetic Algorithms, 59-89 (Kluwer ternational Journal of Intelligent Systems. Nine Academic, Boston, Massachusetts, USA, 1997). papers selected out of a total of 52 in the pro- ceedings of FLINS'96 have been reviewed and D. RUAN, ed., "Intelligent Hybrid Systems: Fuzzy will be published in 1998 in this special issue. Logic, Neural Networks, and Generic Algorithms" (Kluwer Academic, Boston, Massachusetts, USA, 1997). FLINS Volume 6 entitled Intelligent Systems: Fuzzy Logic, Neural Networks, and Genetic Al- D. RUAN, Guest Editor, "Nuclear Safety," Special gorithms was published by Kluwer Academic Issue of Korea J. Fuzzy Logic and Intelligent Systems Publishers. Designed as a natural continuation (Official publication of the Korea Fuzzy Logic and of the previous two FLINS volumes Fuzzy Set Intelligent Systems Society, 1997). Theory and Advanced Mathematical Applica- tions (1995) and Fuzzy Logic Foundations and Publications in 1997 Industrial Applications (1996), it aims to provide researchers and engineers from both aca- X. Li, D. RUAN, "Novel Neural Algorithms Based on demic world and industry with up-to-date cov- Fuzzy <5 Rules for Solving Fuzzy Relation Equations: erage of new results and with an overview of Part 1," Int. J. Fuzzy Sets and Systems 90:1, 11-23 co-operative models of intelligent hybrid sys- (1997). tems, FL, neural networks, and genetic algo- D. RUAN, "Fuzzy Logic in Nuclear Safety Issues," rithms, and some of their industrial applica- Korea J. Fuzzy Logic and Intelligent Systems 7:1, tions. 34-44 (1997).

102 Exploratory R&D Presentations delivered in 1 997

X. Li, D. RUAN, "Constructing a Fuzzy Logic Control Demo Model at SCK-CEN," Fifth European Congress on Intelligent Techniques and Soft Computing (EUFIT'97): Aachen, Germany, September 7-11, 1997. Proc, 1408-1412.

X. Li, D. RUAN, "A Novel Neural Algorithm and Its Application in Solving Fuzzy Relation Equations," Annual meeting of the North American Fuzzy Information Processing Society (NAFIPS'97): Syracuse, New York, USA, September 21-24, 1997. Proc, 356-361.

D. RUAN, X. Li, "Fuzzy Logic Control Applications SCK-CEN: From a Nuclear Reactor to a Demo Model," Joint Conf. of Information Sciences (JCIS'97): North Carolina, USA, March 1-5, 1997. Proc., 132-135.

D. RUAN, X. Li, "The Test of Fuzzy Logic Control with a Closed Loop at the BR1 Reactor," Seventh Int. Fuzzy Systems Association world congress (IFSA'97): Praha, Czech Republic, June 24-29, 1997. Proc. 4, 126-131.

Lectures taught in 1997

D. RUAN, "Fuzzy Logic in Nuclear Engineering," Invited plenary lecture at the Belgium/Fuzzy'97 workshop: Mons, Belgium, April 23-24, 1997.

D. RUAN, "Recent Developments in Intelligent Hybrid Systems," Invited lecture at the int. colloquium on New Technologies Based Learning and Employment Support: Gent and Leuven, Belgium, October 16, 1997.

D. RUAN, "From Fuzzy Set Theory to Intelligent Hybrid Systems," Invited lecture for the artificial- intelligence seminar at the Katholieke Universiteit Leuven: Leuven, Belgium, November 3, 1997.

D. RUAN, "Intelligent Hybrid Systems and Industrial Applications," Invited lecture at the Physics and Electronics Laboratory of the Nederlandse organisatie voor Toegepast-Natuurwetenschappelijk Onderzoek (TNO): Den Haag, The Netherlands, December 16, 1997.

Report published in 1997

X. Li, D. RUAN, "The Current Development of FLC Project at BRl and New Algorithms Design," SCK-CEN report (1997). D046000 95/97-36.

Fuzzy Logic and Intelligent Technologies in Nuclear Science 103 BE9900078

Luc VAN DEN DURPEL

Myrrha: A Prototype Accelerator-Driven System

! Scientific staff O ADDRESS the increasing energy demand fluxes primarily dedicated to radioisotope pro- Luc VAN DEN DURPEL Tand, specially, the demand for public ac- duction. During 1997, a more elaborate study William WACQUIER ceptability, nuclear energy must tackle such set actions to develop the needed expertise at Jean-Luc issues as making the installations absolutely SCK-CEN and marked the start of the engineer- BELLEFONTAINE proliferation-free. In that respect, the de- ing study for a prototype accelerator-driven Hamld AIT ABDERRAHIM velopment of a new type of nuclear installa- system. The next phase, covering 1998 and Fernand VERMEERSCH tion coping with both technological and socio- part of 1999, will finalize the study and the as- Bernard PONSARD economical constraints is most important for sessment of application domains, enabling us Georges MINSART the future of sustainable energy provision. to decide whether to realize the prototype. Serge BODART Accelerator-driven systems, coping with such Pierre D'HONDT constraints, can pave the way to a safer and more acceptable nuclear energy production. Achievements During 1997, we further Fundamental and applied R&D in this field re- explored the modelling of accelerator-driven quire appropriate prototype installations. systems, with special attention to the calculational tools used to assess the waste transmutation. From the engineering point of view, Similarly, nuclear science and engineering re- we looked more closely at the modelling of the quire research installations. Research reactors, windowless liquid lead-bismuth spallation tar- however, currently suffer from ageing, high op- get, the metallurgical aspects of liquid metals, erational costs, or the need for in-depth refur- and the safety assessment of such systems. bishment or even replacement. A new, inher- These studies identified the requirements and ently safe, economically viable, and modular priorities for future research. system is desirable. The application domains were assessed by a Objective scientific committee of experienced neutron- source users. Their conclusions lead to work- m to investigate the design, development, and ing groups related to medical applications and realization of a versatile neutron source to the transmutation of nuclear waste. based on an accelerator-driven system. Currently, the Myrrha project focuses on a Programme Our initial project, called 2 50 MeV, 2 mA cyclotron coupled to a sub- ADONIS, focused on radioisotope production critical facility (Fig. 1). This facility consists relying on an accelerator-driven system. It has of a central spallation target surrounded by been extended to the Myrrha project, for a a lead-moderated fast-neutron zone for trans- broader scope of applications and increased mutation research and a light-water thermal- scientific and technological knowledge. ADONIS neutron zone for light-water reactor research, started in 1995 with a global feasibility study. radioisotope production, and possibly other The second phase, in 1996, refined this study purposes. The respective fluxes could reach for a specific limited-scale system: a 150MeV, 2x lO^n-cm"2^-1 and 7x lO^n-cm"2^"1, 2 mA cyclotron feeding protons to a subcriti- depending on the specific assembly geometry. Figure 1 cal system of high-enriched uranium plates in Next to these neutrons, the accelerated pro- The researched light water, leading to high thermal neutron tons could also be used (Fig. 2). The current Myrrha system.

Linear accelerator Cyclotron Spallation target ;;::: '::: :•:'.:::: 250MeV: " 2 mA:: • •rfrr.:;:;|htegral experiments

'i-Ssv:!:.;! In-core experiments: --^•: : iNeutrph beams ]::; :

: lohifradiatiohs:::::::::Radidisotppes; Proton therapy Materials research: :i:i :i i: :•:::::::;::: i::::':

104 Exploratory R&D design will be detailed during the next engineering phase, leading to a detailed proposal of installation.

Perspectives for 1998 Continuing the above developments, our work will focus on • an elaborate engineering study and safety assessment report of the prototype, including possible experiments to be performed in an international context; • a detailed assessment of applications and experimental setups; • the further development of competencies related to the above development; • the final report on the proposed prototype and a proposal of long-term development programme (in 1999).

Presentations delivered in 1 997

L. VAN DEN DURPEL, "The Myrrha Project: A Small Figure 2 The subcritical assembly in a setup en- Scale ADS System for R&D," Int. workshop on abling a fast- and a thermal-neutron zone. Physics of Accelerator-Driven Systems for Nuclear Transmutation and Clean Energy Production: Trento, Italy, September 29-October 3, 1997.

L. VAN DEN DURPEL, H. AIT ABDERRAHIM, P. D'HONDT, Y. JONGEN, P. COHILIS, P. MOTTET, "An Alternative to Reactor-Based "Mo Production," Scientific meeting of the Belgisch Genootschap voor Nucleaire Geneeskunde: Brussels, Belgium, February 8, 1997. Driven Systems: Coupling of MC and Low Energy L. VAN DEN DURPEL, H. AIT ABDERRAHIM, P. D'HONDT, Neutron Transport Codes as Applied in the Field of G. MlNSART, J.-L. BELLEFONTAINE, S. BODART, ADS," IAEA technical committee meeting on Feasibility B. PONSARD, F. VERMEERSCH, W. WACQUIER, "The and Motivation for Hybrid Concepts for Nuclear Myrrha Project: Current Status," Topical day on Energy Generation and Transmutation: Madrid, Accelerator-Driven Systems: SCK-CEN, Mol, Belgium, Spain, September 17-19, 1997. September 10, 1997. Thesis published in 1 997 L. VAN DEN DURPEL, H. AIT ABDERRAHIM, P. D'HONDT, G. MlNSART, J.-L. BELLEFONTAINE, S. BODART, W. WACQUIER, "Determination of the Neutronic B. PONSARD, F. VERMEERSCH, W. WACQUIER, "A Gain of a Spallation Source: Application to ADONIS Prototype Accelerator-Driven System in Belgium: The Concept," final-year thesis,1 Nuclear Engineering Myrrha Project," IAEA technical committee meeting (Universiteit Gent / Katholieke Universiteit Leuven), on Feasibility and Motivation for Hybrid Concepts September 1997. for Nuclear Energy Generation and Transmutation: Madrid, Spain, September 17-19, 1997. Report published in 1997

L. VAN DEN DURPEL, H. AIT ABDERRAHIM, G. MINSART, L. VAN DEN DURPEL, "Myrrha, a Versatile Radiation w. WACQUIER, "Neutronic Description of Accelerator Source," internal SCK-CEN report (1997). 85/97-06.

Myrrha: A Prototype Accelerator-Driven System 105 BE9900079

Marcel WEBER

Improvement of In-Pile Instrumentation in Experimental Device:

Scientific staff CK« CEN has a long tradition of instrumented Achievements In 1997, we developed Marcel WEBER S experimental devices in the BR2 reactor. an experimental device called DOLMEN (Device Jean DEKEYSER A better knowledge of the phenomena occur- for On-Line MEasurement of Neutron flux), Camlel DECLOEDT ring during irradiation requires more scientific equipped with an assembly of sensors that can Hamid ALT ABDERRAHIM and sophisticated in-pile instrumentation. We be moved vertically in any BR2 channel. This in- Charles DE RAEDT therefore make every effort to extend and im- strumented rig contains Self-Powered Neutron Bernard PONSARD prove the on-line measurements. Detectors (SPNDs), a miniaturized fission cham- Frans SCHELLES ber, activation dosemeters, and gamma ther- Bart SMOLDERS mometers. Objectives Vitali SOBOLEV Rene VAN LOMMEL • to increase the scientific knowledge of the Beyond the mechanical design of DOLMEN, we Rudl VAN NIEUWENHOVE studied phenomena; theoretically studied the sensitivity of an SPND and analysed its measured electrical signal: we • to improve the interpretation of the data; Supporting staff examined, for example, the effects of gamma Josephus VALENBERGHS • to improve the piloting of experimental de- radiation and the decrease of leakage resis- Gerard VAN ESCH vices during irradiation; tance of the SPND itself. • to reveal and to understand possible un- suspected phenomena occurring during ir- Perspectives for 1998 In 1998, we will radiation. manufacture and test in the BR2 reactor the DOLMEN device for on-line measurement of nu- As part of our scientific approach, we model clear parameters. With this irradiation, we aim the probes' behaviour, select the most suitable to elaborate an algorithm leading to the actual sensor for each specific application, test the neutron flux from the measured electrical sig- measurement devices in the BR2 environment, nal, to identify the sensitivity of each param- and assess the whole instrumentation line. eter (neutron spectrum, gamma spectrum), to qualify a calibration method, and to assess the most suitable sensor for a specific application. Programme The programme rests on the following axes: we Based on the scientific needs of other projects • improve the existing techniques and meth- (such as those of "Nuclear Fuel," page 36, and ods; "Reactor Structural Materials," page 48), we will continue to improve and innovate the In-pile • develop innovative techniques; instrumentation; our next objectives are the • model the physical mechanisms of the sen- measurements of fuel-rod elongation and of sor system and the output signal; cladding temperature. • implement quality-assurance procedures.

We intend to investigate the on-line measurements of both the fuel-rod parameters and the environmental conditions (nuclear, coolant), in Scientific partners Commissariat a real time. l'energie atomlque (CEA) — OECD Halden Reactor Project (HRP) — Kurchatov Institute — Moscow State Engineering & Physics Institute (MEPM) — Studsvik Instrument

106 Exploratory R&D BE9900080

Marc DECRETON

Advanced Instrumentation and Teleoperation

EMOTE OPERATION for maintenance, re- radiation of radiation-hardened components Scientific staff R pair, and dismantling tasks is a well-es- previously assessed under gamma irradiation. Francis BERGHMANS tablished practice in the nuclear industry, be- For instance, we irradiated glass samples for Benoit BRICHARD cause radiation doses impede hands-on work radiation-hardened optical lenses in the BRI re- Simon COENEN 16 2 in some instances. However, even under less actor up to a total fluence of 7 x 10 n-cm~ Marc DECRETON extreme conditions, remote work minimizes (fast flux), but observed no neutron-specific Jan DE GEETER waste production, contamination risks, and oc- degradation so far. By contrast, the neutron Olivier DEPARIS cupational doses. Furthermore, in comparison irradiation of a radiation-tolerant multiplexer Alberto FERNANDEZ with purely manual control of telemanipula- circuit, built around space-graded chips (up FERNANDEZ 13 2 tors, a sensor-based and computer-aided ap- to a fluence of 5 x 10 n-cm~ in fast flux), Marc NOEL proach enhances safety, reliability, and perfor- showed a degradation behaviour quite differ- mance by helping the operator in difficult tasks ent from the one appearing under gamma irra- Supporting staff where remote perception is difficult. diation: the digital circuits appeared here more Dirk VAN BECKHOVEN sensitive than the analog ones. A comprehen- Stan VAN IERSCHOT sive neutron irradiation on displacement sen- Frans Vos Objectives The Advanced Instrumentation sors and strain gauges is still ongoing. and Teleoperation project aims at evaluating the potential of a telerobotic approach in a nu- Regarding ultrasonic sensors, we further im- clear environment and, in particular, the use proved the measurement technique and in- of advanced remote-perception systems. It fo- cluded a spectral response analysis of the cuses on two main difficulties: the tolerance of transducers. The results (at 7 MGy of gamma sensors to high radiation doses and the intelli- irradiation) show not only that the amplitude gent data processing needed to compensate for response of the transducers degrades, but also the limitations of the simpler but more robust that their resonance frequency shifts. A peak- radiation-hardened transducers. tracking detection would therefore greatly enhance the applicability of these sensors under Programme The project implies to set up high-dose background. An extensive irradia- a database for all sensitive components to be tion campaign on piezoelectric accelerometers used on a nuclear manipulator and to conduct was started. Preliminary results at 3 MGy show extensive tests under irradiation, with par- that the frequency response in the 30-3000 Hz ticular attention to optical-fibre components. range remains remarkably stable. It also develops position- and force-sensing strategies for computer-aided telerobotics, us- In collaboration with SdM, we increased the ir- ing specific radiation-hardened transducers. radiation of special bipolar transistor chips up The study of some of these sensors is extended to 750kGy. The tests confirmed this bipolar outside the scope of teleoperation to more gen- technology to be quite promising for high total eral applications of advanced instrumentation doses, but showed also the crucial importance in nuclear environments. of bias conditions on the radiation tolerance.

Radiation tolerance for remote sensing Optical fibres and optical-fibre sensors Components of remote-sensing systems, which In view of the unique advantages that fibre- are mainly designed for sensor-based control optics communication and sensing systems of remote manipulators, have been further as- can bring to the monitoring of nuclear instal- sessed and tested in representative gamma and lations, we devoted further attention to the ra- neutron environments at high dose rates. Sev- diation tolerance of various photonic devices, eral irradiation campaigns were conducted in in close collaboration with VUB and FPMs. Be- the BRi reactor and in the BR2 and BR3 gamma sides current fibres, these devices cover spe- irradiation facilities (RITA, BRIGITTE, and GEUSE). cific fibre sensors for temperature, strain, dose measurements, fibrescopes, and crucial com- To compare the behaviour of various compo- ponents of an optical signal-processing sys- nents under gamma and neutron irradiation, tem, such as liquid-crystal variable retarders we devoted more attention to the neutron ir- for modulating the polarization of light.

Advanced Instrumentation and Teleoperation 107 When exposed to nuclear radiation, optical fi- In collaboration with the Russian FORC, we bres can suffer a strong increase in transmis- are studying the feasibility of optical-fibre do- sion loss. This radiation-induced loss results simetry, using phosphorus-doped fibres. We from the creation of so-called colour centres, test different dopant concentrations to obtain which are point defects in the fibres' vitreous a linear radiation-induced attenuation and a silica, generating absorption bands in the ultra- negligible recovery. violet and visible-light spectrum. Besides absorbed radiation dose, dose rate, tempera- Liquid crystals are also of major importance ture, and wavelength, the fabrication process in today's photonic technology, but very lit- of the fibre itself largely determines its radia- tle is known about their radiation tolerance. tion response. Earlier work focused on the Liquid-crystal variable retarders made of pla- transparency of optical fibres for applications nar nematic liquid-crystal cells were irradiated in the visible wavelength range, such as fi- up to 1.5 MGy. The characteristic retardance- brescopy. Now, in collaboration with the Kur- voltage curves shift to lower values as a func- chatov Institute (Russia), we realized a pro- tion of dose, mainly because of the degrada- totype fibrescope which can be used up to tion of the boundary cohesion of liquid-crystal total doses of 1 MGy. We extended our in- molecules with the polyimide alignment layer vestigations to particularly pure silica core or of the liquid-crystal cell. low-germanium-content core single-mode optical fibres for telecommunication. One particular problem was to interpret neutron ir- Computer-aided teleoperation Although radiation effects on polymer-coated optical fi- the tasks to be performed remotely are usu- bres. For apparently equal neutron and gamma ally similar to hands-on tasks in normal fac- doses, the neutrons induced higher attenua- tory workshops, the use of a telemanipulator tion than gamma rays. In collaboration with arm brings particular difficulties to the oper- FhG, we showed that this increased attenua- ator: the slave arm is but a poor copy of the tion was due to an additional dose contribution human one, and the remote sensors, particu- of neutron-induced recoil protons originating larly radiation-hardened ones, are but a poor from the polymer coating. substitute for the human senses. We continued our research on sensor-based control, to Optical-fibre sensors are also being upgraded develop an efficient aid to the human opera- to the nuclear constraints. Our attention fo- tors of a remote machine. cused on three types of commercially available optical-fibre temperature sensors, which we ex- In nuclear applications, full three-dimensional posed to gamma radiation. The most gamma- models of the environment are rarely available. radiation-resistant sensors appear to be the Usually, however, an accurate geometric infor- semiconductor absorption sensors, which re- mation is only needed very locally, close to the mained operational up to the end of the test object to handle. Our work therefore focused (400 kGy). A Fabry-Perot sensor on the other on task-directed geometric modelling of small hand degraded almost linearly as a function parts of the environment, made possible by of dose, whereas fluorescence sensors stopped active sensing, that is, by moving the sensors operating abruptly right at the start (250 Gy). around to build the needed information. Both failure modes could be related to a bad choice of the connecting fibre. Flitting another In 1997, we proposed a smoothly constrained fibre on the fluorescence sensor, for instance, Kalman filter, new extension of the well-known allowed us to increase its tolerance at least up Kalman filter to systems with constraints. Ob- to 50 kGy, which represents an improvement jects are described as a collection of simple by a factor of 2 000. The optimization of the primitives such as planes and cylinders, with sensor design for operation in more benign en- constraints defining their relative positions. vironments may thus work poorly under ra- This state description shortens design times, diation. For instance, a larger numerical aper- as a limited set of primitives suffices to de- ture of the connecting fibre to minimize optical scribe a wide range of objects and their inter- power injection loss yields a less tolerant fibre. action with the sensors.

108 Exploratory R&D Recently, we focused on data interpretation Filter," IEEE Transactions on Pattern Analysis and and developed a multiple-hypothesis tree, to Machine Intelligence (PAMI) 19:10, 1171-1177 solve the possible ambiguities on the origin of (October 1997). the measurements (that is, which part of which 0. DEPARIS, D. L. GRISCOM, P. MEGRET, M. DECRETON, object was observed by a given sensor). The M. BLONDEL, "Influence of the Cladding Thickness technique keeps track of different hypotheses on the Evolution of the NBOHC Band in Optical and eliminates them progressively with suc- Fibres Exposed to Gamma Radiations," Journal of cessive measurements. Our research concen- Non-Crystalline Solids 216, 124-128 (1997). trated on the best methods to prune the hypothesis tree and to rank the plausible inter- 0. DEPARIS, P. MEGRET, M. DECRETON, M. BLONDEL, pretations of the measurements. "660 nm and 760 run Bands Evidenced in a Low-OH Low-Cl Fibre by Gaussian Deconvolution of Radiation- We also tackled the active-sensing algorithm it- Induced Loss Spectra," IEE Electronics Letters 33:6, self, that is, the task-directed planning of the 522-523 (March, 1997). sensing actions to improve the reliability of the estimate and to obtain the precision required H. HENSCHEL, 0. KOHN, S. METZGER, M. DECRETON, by the task. Since the classical theory of opti- 0. DEPARIS, P. DEVOS, "Neutron Dose and Fluence mal experimental design shows definite short- Measurements by Optical Fibres, Neutrons in comings in the context of this work, we are now Research and Industry," SPIE Proc, 2867, 290-295 finalizing a new method, called energy-optimal (1997). experiment design. H. THIENPONT, B. VERWILGHEN, F. BERGHMANS, "Glasvezelsensoren komen in industriele fase: Realiteiten in vijandige omgeving. Les capteurs a fibres de verre entrent dans une phase industrielle: Realites dans un environnement hostile," Technisch Scientific partners Atomic Energy Authority (AEA Management / Technique ef Management, VI-X (June Technology) — Centro de Investigaciones Energeti- 1997). cas, Medioambientales y Tecnologicas (CIEMAT) — Fibre Optics Research Centre (FORC) — Fraunhofer Presentations delivered in 1 997 GeseUschaft (FhG) — Kurchatov Institute — National F. BERGHMANS, M. DECRETON, D. BOUEILH, A. CONDE Optical Institute/Institut national d'optique (NOI- REIS, Ph. JUCKER, M. VAN UFFELEN, "Space and INO) — Societe de microelectronique (SdM) — Nuclear Environment Tolerancing of Photonic Universite Libre de Bruxelles (ULB) — Vrije Uni- Devices: Three European Contributions," Invited versiteit Brussel (VUB) — Katholieke Universiteit paper, SPIE Advancement of Photonics for Space Leuven (KUL) — Faculte polytechnique de Mons (FPMs) conf.: San Diego, California, USA, July 27-August 1, 1997. Proc: SPIE Critical Reviews of Optical Science Sponsor European Commission (EC), Fusion and Technology, CR66, 155-183. Technology and Fusion Underlying Technology Programmes F. BERGHMANS, M. DECRETON, H. THIENPONT, 1. VERETENNICOFF, "Fibre-Optic Sensor Multiplexing Adapted to Monitoring and Remote Handling Applications in Nuclear Environments," Forum of the Union RadioScientiflque Internationale (URSI): Ghent, Publications in 1 997 Belgium, December 10, 1997. Proc., 3-5.

F. BERGHMANS, K. ZDRODOWSKI, T. NASILOWSKI, F. BERGHMANS, F. VOS, M. DECRETON, "Evaluation M. DECRETON, I. VERETENNICOFF, H. THIENPONT, of Three Different Optical Fibre Temperature "Influence of Gamma Radiation on the Electro-Optic Sensor Types for Application in Gamma Radiation Behaviour of Planar Nematic Liquid Crystal Cells," Environments," Fourth European conf. on the IEEE Photonics Technology Letters 9:4, 481-483 Radiations and Their Effects on Devices and Systems: (1997). Cannes, France, September 15-19, 1997.

J. DE GEETER, H. VAN BRUSSEL, J. DE SCHUTTER, M. DECRETON, "A Smoothly Constrained Kalman

Advanced Instrumentation and Teleoperation 109 S. COENEN, M. DECRETON, "Radiation Resistant Cables 0. DEPARIS, P. MEGRET, M. DECRETON, M. BLONDEL, Subject to Dynamic Stress in Highly Radioactive K. GOLANT, A. TOMASHUK, "Rad-Hard Optical Fibres Environments," Eurocable'97 conf.: Antwerp, for Diagnostics of Experimental Fusion Reactors," Int. Belgium, June 16-18, 1997. Proc, 109-115. workshop on Diagnostics for Experimental Fusion Reactors: Varenna, Italy, September 4-12, 1997. M. DECRETON, "Fiber Optic Applications in Decom- missioning Activities," Fourth European conf. on the 0. DEPARIS, M. NOEL, M. DECRETON, "The Behaviour Radiations and Their Effects on Devices and Systems: of Silica Fibres under Low Fast-Neutron Fluxes," Cannes, France, September 15-19, 1997. Fourth European conf. on the Radiations and Their Effects on Devices and Systems: Cannes, France, M. DECRETON, "Increased Need for High Radiation September 15-19,1997. Tolerance Components in Civil Nuclear Remote Handling Systems," European workshop on the V. MASSAUT, M. DECRETON, "Le demantelement du Commercialization of Military and Space Electronics: BR3: retour d'experience en telemanipulation et Nice, France, November 12-14, 1997. Proc, 7/29- en robotique," SFEN workshop on "Demantelement 7/42. et Application de la Robotique": Paris, France, January 23, 1997. M. DECRETON, S. COENEN, J. DE GEETER, "Radiation Hardened Sensor Implementation for Computer M. NOEL, "Neutron Dose Calculation in Plastic-Coated Aided Teleoperation in Nuclear Environments," IEEE Silica Optical Fibres," Special seminar: SCK«CEN, Mol, int. symp. on Industrial Electronics: Guimaraes, Belgium, May 22, 1997. Portugal, July 7-11, 1997. Proc., 278-284. Yu. TARABRIN, L. PAVLOV, 0. DEPARIS, M. DECRETON, J. DE GEETER, "Telemanipulation in Nuclear Applica- "Radiation Hardened Fibroscopy: A Technological tions: Our Experience," Int. workshop on Advanced Approach," Fourth European conf. on the Radiations Robotics and Intelligent Machines: Manchester, and Their Effects on Devices and Systems: Cannes, United Kingdom, March 25-26, 1997. France, September 15-19, 1997.

J. DE GEETER, J. DE SCHUTTER, M. DECRETON, Theses published in 1997 H. VAN BRUSSEL, "Sensor Action Planning Driven by Uncertainty: Application to Object Location with T. BALLET, "Ontwerp van een stralingsbestendige mul- Robust Local Sensors in a Nuclear Environment," tiplexer," final-year project, Industrial Engineering First int. conf. on Computing Anticipatory Systems: (Hogeschool Limburg, Hasselt), July 1997. Liege, Belgium, August 11-15, 1997. Proc., 37-40. 0. DEPARIS, "Etude physique et experimentale de la J. DE GEETER, H. VAN BRUSSEL, J. DE SCHUTTER, tenue des fibres optiques aux radiations ionisantes M. DECRETON, "Local World Modelling for Teleop- par spectrometrie visible-infrarouge," PhD thesis, eration in a Nuclear Environment Using a Bayesian Electromagnetism and Telecommunication (Faculte Multiple Hypothesis Tree," IEEE/RSJ int. conf. on Polytechnique de Mons), March 1997. Intelligent Robots and Systems: Grenoble, France, September 8-12, 1997. Proc., 3, 1658-1663. Reports published in 1997

0. DEPARIS, P. MEGRET, M. DECRETON, M. BLONDEL, S. COENEN, "ITERT-252 Irradiation Report on Cables "Temperature Sensitivity of Microbending Losses with In Situ Bending up to 130MGy," SCK-CEN report in Radiation-Resistant Optical Fibers," SPIE conf. (March, 1997). R-3156. on Photonics for Space Environments: San Diego, S. COENEN, "ITER T-252 Progress Report from the California, USA, July 27-August 1, 1997. Proc., 3124, European Home Team," April 1996-March 1997, 2-8. SCK>CEN report (March, 1997). R-3155. 0. DEPARIS, P. MEGRET, M. DECRETON, M. BLONDEL, M. NOEL, "SMIRNOF Experiment Report, Part one: "Toward a Reliable Metrology of the Radiation- Neutron Irradiation," SCK-CEN report (March, 1997). Induced Attenuation in Optical Fibres from Visible 27/97-25. to Near Infrared Ranges," Fourth Optical Fibre Measurement conf.: Teddington, United Kingdom, M. NOEL, "Neutron Fluence to Absorbed Dose September 29-October 1, 1997. Proc., 183-186. Conversion for Acrylate-Coated Silica Optical Fibres," SCK- CEN report (April 1997). R-3160.

110 Exploratory R&D

Scientific staff members

This index lists the SCK- CEN scientific staff members mentioned in this report. Page numbers typeset in boldface correspond to project managers.

AERTSENS, Marc, 72 DE BARKER, Paul, 48 AIT ABDERRAHIM, Hamid, 36, 41, 48, 94, 104, 106 DE BOCK, Antoon, 94 ALZETTA, Jean-Pierre, 6, 8 DE BOECK, Wim, 64, 88 ANTOINE, Philippe, 33 DEBOODT, Pascal, 33, 57 AQUINO, Angelo, 94 DE BREMAECKER, Anne, 46 ARIEN, Baudouin, 36, 46, 94 DE BRUYN, Didier, 72 DE CANNIÈRE, Pierre, 72 BAATOUT, Sarah, 26 DECLERCQ, Stefan, 94 BAETEN, Peter, 64, 88 DECLOEDT, Camiel, 94, 106 BARNICHON, Jean-Dominique, 72 DE CRAEN, Mieke, 72 BAUGNET, Jean-Marie, 94 DECRÉTON, Marc, 107 BEAUFAYS, Rudi, 72 DE GEETER, Jan, 107 BEETS, Willy, 94 DEKEYSER, Jean, 94, 106 BELLEFONTAINE, Jean-Luc, 104 DELBRASSINE, Albert, 36 BENOIT, Philippe, 36, 57, 94 DELCOUX, Jean-Luc, 46, 94 BERGHMANS, Francis, 107 DELLEUZE, Dominique, 72 BERGMANS, Gilbert, 94 DE MAEYER, David, 41 BERNIER, Frédéric, 72 DEMEULEMEESTER, Yves, 69 BODART, Serge, 36, 104 DE MULDER, Frans, 94 BODEN, Renatus, 90 DEPARIS, Olivier, 107 BODEN, Sven, 72 DE RAEDT, Charles, 36, 41, 94, 106 BORGERMANS, Paul, 72 DEREEPER, Bernard, 72 BORMS, Luc, 36, 41 DE REGGE, Peter, 64, 90 BORTELS, Yvo, 41 DE SAINT-GEORGES, Louis, 26 BOSCH, Rik-Wouter, 55 DESSARS, Nathalie, 46 Bossi, Guido, 94 D'HONDT, Pierre, 36, 41, 104 BOYDENS, Pascal, 55 DIERCKX, Ann, 72 BRAET, Johan, 61 DIERCKX, Jan, 94 BRICHARD, Benoît, 107 DRUYTS, Frank, 57, 72 BRUGGEMAN, Aimé, 61 BRUGGEMAN, Michel, 64, 88 ENGELS, Hilde, 26 BUYENS, Marc, 72 EYSERMANS, Ludo, 55

CARCHON, Roland, 64, 88 FABRY, Albert, 48, 94 CATTOIR, Sieglinde, 61 FERNANDEZ FERNANDEZ, Alberto, 107 CHAOUADI, Rachid, 48, 55, 57, 94 CLAES, Simon, 94 GENICOT, Jean-Louis, 8 CLAES, Willy, 94 GEYSEN, Eduard, 94 COENEN, Simon, 107 GOMMERS, Annick, 17 COHEUR, Louis, 36, 57 GOVAERTS, Paul, 33 COLLARD, Guy, 60 GUBEL, Pol, 94 CORBISIER, Jean-Marie, 94 GYS, August, 36 CORNELISSEN, René, 61, 68 GYSEMANS, Mireille, 64, 90 CORTHOUTS, Willy, 94 COUPÉ, Bernard, 94 HARDEMAN, Frank, 6, 8, 33 CUYNEN, Paul, 3, 8 HARNIE, Roger, 61, 68 HARNIE, Sven, 61 DADOUMONT, Jérôme, 69 HENDERIX, Roger, 69 DANIELS, Albert, 36 HEUSDAINS, Simone, 36, 46, 94

112 Indexes HOLMSTOCK, LUC, 26 PARIDAENS, Johan, 4 HOLVOET, François-Xavier, 72 PAUWELS, Noël, 33 HURTGEN, Christian, 8, 33 PETITFOUR, Benoit, 61 HUYS, Daniel, 90 PIRLET, Vera, 72 PITZ, Brigitte, 72 JACQUET, Paul, 26 PLATEAU, Charles, 69 JOPPEN, Frank, 57, 94 POMMÉ, Stefaan, 6, 8 PONNET, Mathieu, 69 KLEIN, Michel, 69 PONSARD, Bernard, 94, 104,106 KOONEN, Edgar, 36, 94 POULEUR, Yvan, 94 KURSTEN, Bruno, 72 PUT, Martin, 72 PUZZOLANTE, Jean-Louis, 36, 48, 57, 94 LÁBAT, Serge, 72 LAEREMANS, Jozef, 90 RAHIER, André, 61 LAMPROYE, Michel, 8 RAMAEKERS, Filip, 94 LAMY, Dominique, 46 REYNERS, Hubert, 26 LASKA, Karel, 94 ROJAS PALMA, Carlos, 12 LEMMENS, Karel, 72 RUAN, Da, 100 LEWYCKYJ, Nicolas, 17, 12 RUTS, Jan, 12 Ll, Xiaozhong, 100 LIESENBORGS, Richard, 94 SANNEN, Leonard, 36, 55 LOLIVIER, Philippe, 72 SCHELLES, Frans, 55, 94, 106 Loos, Mark, 2, 3, 24, 33 SCHOUTEN, André, 94 SCIBETTA, Marc, 48 MAES, Ludo, 8 SLEGERS, Willy, 33 MAES, Norbert, 72 SMAERS, Frans, 61 MAHIEU, Lucile, 26 SMOLDERS, Bart, 55, 94, 106 MALAMBU, Edouard, 41 SNEYERS, Alain, 72 MALLANTS, Dirk, 72 SOBOLEV, Vitali, 36, 106 MALLANTS, Fernand, 94 SOHIER, Alain, 12, 33 MANDOKI, Robert, 64, 69, 88 STYNEN, Roger, 94 MARIEN, Jef, 61 SWEECK, Lieve, 12,24 MARIVOET, Jan, 72 SWINNEN, Jan, 69 MARLOYE, Daniel, 41 MASSAUT, Vincent, 69 THIEREN, Lucien, 94 MELLEMANS, Steven, 55 THIRY, Yves, 17 MESKENS, Gaston, 94 THOMAS, Peter, 90 MEYNENDONCKX, Pol, 72 MEYUS, Yves, 72 VALCKE, Elie, 72 MIES, LUC, 36 VALENDUC, Pierre, 69 MINSART, Georges, 41, 94, 104 VAN ALSENOY, Veerle, 61 MOERS, Sven, 69 VAN BALEN, Marcel, 94 MOONS, Frans, 55, 57 VANDECASTEELE, Christian, 17, 33 MOORS, Hugo, 72 VANDEGEHUCHTE, Marc, 46 VAN DEN BERGHE, Sven, 36 NEERDAEL, Bernard, 72 VAN DEN DURPEL, LUC, 41, 104 NOËL, Marc, 107 VANDENHOVE, Hildegarde, 12, 17 NOËL, Marcel, 94 VAN DEN PUT, Frans, 36, 48 NOYNAERT, Luc, 61, 68 VAN DER AUWERA, Jan, 94 VANDERLINDEN, Frank, 64, 90 OOMS, Hans, 94 VAN DER MEER, Klaas, 36, 41, 64, 88 ORTIZ, Lorenzo, 72 VAN DE VELDE, José, 48, 55, 57, 94 OuLiDDREN, Kamreddine, 46 VAN DE VELDE, Peter, 94

Scientific staff members 113 VANDEVELDE, Leon, 64, 90, 94 VAN WALLE, Eric, 48 VAN DE WALLE, Bartel, 12 VAN WINCKEL, Stefaan, 90 VAN EYNDHOVEN, Karel, 94 VERBOOMEN, Bernard, 41, 94 VAN GILS, Karel, 90 VERMEERSCH, Fernand, 104 VANHAVERE, Filip, 3, 8 VERMUNT, Jan, 94 VANHEES, May, 17,33 VERREZEN, Freddy, 8, 33, 64 VAN HOOF, Marcel, 94 VERSTREPEN, Alfons, 57 VAN HOOF, Michel, 94 VERSTRICHT, Jan, 72 VANHOOF, Eddy, 36 VERWERFT, Marc, 36, 48, 55, 57, 94 VAN HOOLST, Marcel, 94 VERWIMP, Alfons, 94 VAN ISEGHEM, Pierre, 57, 72 VOLCKAERT, Geert, 24, 72 VANKEERBERGHEN, Marc, 55 VAN LOMMEL, Rene, 106 WACQUIER, William, 72, 104 VANMARCKE, Hans, 4, 8, 24, 33 WAEGENEERS, Nadia, 17 VANMECHELEN, Pieter, 41,48 WANG, Lian, 72 VAN MIEGHEM, Eric, 26 WANNIJN, Jean-Pierre, 48 VAN NIEUWENHOVE, Rudi, 55,106 WEBER, Marcel, 36, 55, 94,106 VAN OUYTSEL, Kristel, 48 WEMAERE, Isabelle, 72 VAN RANSBEECK, Theo, 48 WILLEKENS, Victor, 36, 41 VAN UFFELEN, Paul, 36 ZEEVAERT, Theo, 12, 24

114 Indexes Authors

This index lists the authors of the scientific output mentioned in this report. Because of the many scientific collaborations, not all authors listed are SCK-CEN staff members.

AERTSENS, M., 83, 84, 85, 86, 87 BOYDENS, P., 56 DAVID, J.-L, 31 AHLBRECHT, M., 16 BOZAS, E., 31, 32 DE BAETS, B., 16 AIT ABDERRAHIM, H., 45, 54,105 BRAET, J., 62, 63 DE BARKER, P. M. A., 53 ALEXAKHIN, R.M., 22 BRUGGEMAN, A., 62, 63 DEBARBERIS, L., 45 ALZETTA, J.-P., 7,11 BRUGGEMAN, M., 63, 66, 67, 87, 89 DE BATIST, R., 53 ANTOINE, Ph., 34 BRUNEL, G., 67, 87 DÉBAUCHE, A., 5 AOUST, T., 45 BÜCHERL, Th., 67 DE BOECK, W., 66, 67 ARANA, G., 7 BUHMANN, D., 86 DE BOER, E., 3 ARIEN, fi., 40, 47 BURTON, O., 22, 34 DEBOODT, P., 25, 34, 58, 71 ARKHIPOV, A. N., 22 BUSET.J., 31, 32 DE BROUWER, S., 22 ARKHIPOV, N.P., 22 BUYSSE, J., 11 DE BRUYN, D., 83 ASKBRANT, S., 22 DEBUYST, R., 3 CADELLI, N., 86 DE CANNIÈRE, P., 83, 84, 85, 86, 87 BAATOUT, S., 30, 31, 32 CALLENS, F., 3 DE CORTE, F., 7 BACQUOY, C, 22 CALLEWAERT, L., 85 DECRÉTON, M., 109, 110 BAETEN, P., 66, 67, 89 CAMPSTEYN, A., 63 DE GEETER, J., 109, 110 BAETSLÉ, L.H., 45 CANY, F., 85 DE GRAVE, E., 53 BALLESTEROS, A., 45 CAPEAU, S., 86 DEGUELDRE, D., 34 BALLET, T., 110 CARCHON, R., 45, 66, 67, 85, 89 DEKEYSER, J., 40 BARBU, V., 63 CASPARI, G., 67 DELBRASSINE, A., 40 BARDONE, G., 67 CATTOIR, S., 63 DELCOUX, J.-L., 47 BARTHELEMY, N., 31 CERTES, C, 83, 86 DE LELLIS, C, 5 BARTSCH, P., 31 CHABALIER, B., 67 DELEPINE, J., 67 BASSELIER, J., 45, 91 CHAOUADI, R., 53, 54, 58 DELVAUX, B., 16, 22 BAUDOIN, P., 83 CHARD, P., 89 DEMEULEMEESTER, Y., 71 BAUGNET-MAHIEU, L., 31, 32 CHARUE, N., 86 DENEUFBOURG, J.-M., 31 BEAUCAIRE, C, 85 CHETA, N., 31 DEN HOND, W., 67 BEAUFAYS, R., 86, 87 CLARK, D.E., 84 DEPARIS, 0., 109, 110 BELLEFONTAINE, J.-L., 105 COENEN, S., 110 DEPESTEL, M., 34 BENEKOU, A., 31, 32 COFFIGNY, H., 32 DE PRÊTER, P., 87 BENOIT, Ph., 40, 58 COHEUR, L., 58 DE RAEDT, Ch., 40, 45, 91 BERGHMANS, F., 109 COHILIS, P., 105 DEREEPER, B., 86 BERNIER, F., 83, 84, 86, 87 COLINO, E., 58 DE REGGE, P., 40, 62, 66, 85 BIGNAN, G., 89 CONDE REIS, A., 109 DE SAINT-GEORGES, L., 31, 32 BLOEM, J., 67 CORNÉLIS, B., 86 DE SCHUTTER, J., 109, 110 BLOMMAERT, W., 11 CORNELISSEN, R., 62, 68, 71 DESREUX, J.-F., 84 BLONDEL, M., 109,110 CORTHOUTS, V., 86 DESSARS, N., 47 BODART, S., 105 COUGHTREY, P. J., 22 DE TURCK, K., 86 BODEN, R., 66 COULON, J.P., 67 DEURWAARDER, C.P., 67 BODEN, S., 63, 83 CREMERS, A., 22 DEVOOGHT, J., 47 BOISSON, J. Y., 86 CROFT, S., 89 DEVOS, P., 109 BONAL, J.P., 58 CRUSTIN, J., 67 D'HONDT, P., 45, 54, 105 BORGERMANS, P., 83 CULOT, J.-P., 11 DIERCKX, A., 83, 84, 86 BORMS, L., 40, 45 DODARO, A., 89 BOSQUEE, L, 31 DADOUMONT, J., 71 DOUWEN, J., 86 BOSSART, L., 63 DAISH, S., 67 DRIESEN, S., 63 BOTTE, J., 67 DÄMMEN, J., 23 DRUYTS, F., 58, 84 BOUEILH, D., 109 DANIELS, A., 87 DRYMAEL, H., 34 BOUSHER, A., 16 DARDAINE, M., 87

Authors 115 ElNCHCOMB, S., 84, 87 HOLKAMP, P., 67 LOOS, M., 3, 11, 25, 34 ELSEN, A., 22 HOLVOET, F.-X., 83, 84, 85, 87 Lu, M. S., 89 ENGELS, H., 22 HOOPER, A. J., 86 Luis MARTIN, P., 87 ENGELS, H., 30, 32 HORSEMAN, S.T., 86, 87 LYOUSSI, A., 67 ESCALIER DES ORRES, P., 83, 86 HOSKENS, E., 87 ETXEBARRIA, N., 7 HUERTAS, F., 87 MAES, A., 85, 86 HUGÓN, M., 87 MAES, G., 86 FABRY, A., 53, 54 HURTGEN, C, 11 MAES, N., 83, 84, 86 FEDERICI, V., 62 HUYS, D., 87 MALAMBU, E., 45 FERRER, I., 32 MALDAGUE, Th., 45, 91 FERRER, R., 32 IMBERT, Ch., 85, 87 MANAI, T., 86 FIERENS, T., 86 IMPEY, M., 84, 87 MANDOKI, R., 71, 87 FlLSS, P., 67, 87 IVANOV, Y., 22 MARIANI, A., 67, 89 FIRSAKOVA, S.K., 22 MARIEN, J., 71 FLEMAL, J.M., 5 JACQUET, P., 31, 32 MARIVOET, J., 83, 84, 85, 86, 87 FONTEYNE, A., 87 JANECZKO, C, 32 MARLIN, C, 85 FRAZZOLI, F.V., 67 JOCKWER, N., 85 MARLOYE, D., 45 FREUDENREICH, W.E., 67 JONES, A., 16 MARQUES, S., 63 JONES, C, 62, 63 MARTENS, C, 40 GARCIA, J. C, 40 JONGEN, Y., 105 MARTENS, K. H., 83, 86 GASIAUX, F., 83 JUCKER, Ph., 109 MARTIN, D., 71 GASPARY, G., 87 JUNG, T., 31 MASSAR, A.-M., 31 GENICOT, J.-L., 11 MASSAUT, V., 71, 110 GENS, A., 85, 87 KERRE, E., 16 MEESSEN, G., 5 GENS, R., 66, 85 KIRCHMANN, R., 22, 34 MÉGRET, P., 109, 110 GENTY, A., 85, 87 KLAASSEN, A., 3 MERCKX, R., 22 GEORGESCU, 1.1., 11 KLEIN, H., 67 MERTENS, L., 40 GERARDY, L, 5 KLEIN, M., 62, 71 METZGER, S., 109 GERITS, J., 67 KOHN, O., 109 MEYNENDONCKX, P., 87 GHOREYCHI, M., 86 KREBS, K., 67 MEYUS, Y., 86 GlANFELICI DE REYNERS, E., 31, 32 KRUGLOV, S.V., 22 MICHAUX, A., 31 GOBLET, P., 86 KÜHNE, J., 67, 87 MICHELOT, J.L., 85 GODON, N., 85 KURSTEN, B., 84, 85, 86 MIHAI, S.A., 11 GOLANT, K., 110 KWAST, H., 58 MlLLARD, A., 85 GOMIT, J.M., 86 MlNON, J.-P., 11 GOMMERS, A., 22 LABAT, S., 86, 87 MINSART, G., 45, 105 GOVAERTS, P., 34 LABEAU, P. E., 47 MOERS, S., 71 GRAMS, G., 63 LABIOUSE, V., 83, 84, 86 MOONS, F., 58 GRÉGOIRE, C., 84 LAMBOTTE, J.-M., 34 MOORS, H., 83, 84, 86 GRIFFAULT, L.Y., 86 LAMMAR, P., 86 MORALES, A., 67, 87 GRISCOM, D.L., 109 LAMPROYE, M., 11 MOTTET, P., 105 GROSSI, G., 67 LASSABATERE, Th., 85, 87 MOUCHE, E., 85, 87 GUARDINI, S., 89 LECLERCQ, M., 63 GULDBAKKE, S., 67 LEFÈBVRE, A., 71 NASILOWSKI, T., 109 GYS, A., 40 LEMMENS, K., 83, 84, 85 NEERDAEL, B., 84, 87 LEPOTIER, C, 85 NEUKEL, T., 67 HALL, A., 83, 86 LEVASSOR, A., 83, 86 NOËL, M., 110 HALLEZ, S., 5 LEVCHUK, S.E., 22 NONNEMAN, S., 89 HARDEMAN, F., 7, 11, 34 LEWIS, A., 67 NORDMAN, H., 86 HARNIE, R., 63, 68 LEWIS, T., 45 NOWÉ, A., 47 HARNIE, S., 62, 68, 71 LEWYCKYJ, N., 16, 22 NOYNAERT, L., 62, 68, 71, 87 HARRINGTON, J.F., 87 LlERSE, Ch., 67, 87 HASEMANN, I., 16 LITTLEBOY, A. K., 86 OBERSTEDT, S., 5 HASSANIZADEH, M., 85 Li, X., 102, 103 ODOJ, R., 67, 87 HENDRIX, J. P., 67 Liu, X., 16 ONIZAWA, K., 53 HENSCHEL, H., 109 LODDING, A.R., 84 ORTIZ, L, 84, 85, 87 HERION, F., 31 LOLIVIER, Ph., 83, 84, 85 OULIDDREN, K., 47

116 Indexes PALUT, J.M., 86, 87 SEVERO, A., 62, 63 VANKERKOM, J., 31, 32 PARIDAENS, J., 5 SHAW, G., 11 VAN LAER, F., 34 PARKER, D., 89 SlMONITS, A., 7 VANMARCKE, H., 5, 25 PASHLEY, V., 86 SLUGEN, V., 53 VANMECHELEN, P., 54 PAULY, J., 16 SMAERS, F., 62 VAN OUYTSEL, K., 53, 54 PAUWELS, J., 7 SMITH, J., 16 VAN PETEGEM, F., 63 PAUWELS, N., 34 SMOLDERS, E., 22 VAN RANSBEECK, Th., 54 PAVLOV, L., 110 SNEYERS, A., 83, 84, 85 VAN RAVESTYN, L., 86 PEDERSEN, B., 67 SOBOLEV, V., 40 VAN UFFELEN, M., 109 PEREPELAYTNIKOV, G., 22 SOHIER, A., 16 VAN UFFELEN, P., 40 PETITFOUR, B., 63 SOUDAN, K., 34 VANVELZEN, L.P.M., 67 PHILIPPIDIS, H., 32 STEINER, H., 71 VAN WAEYENBERGE, B., il PHILIPPOT, A. C, 85 STEPHENS, S., 86 VAN WALLE, E., 53, 54 PlCAVET, 0., 45 STERCKX, W., 86 VAN WEERT, F., 85 PINA, G., 67 STORCK, R., 86 VANWILDEMEERSCH, J., 63 PlRLET, V., 83, 84 STYLIANOPOULOU, F., 31, 32 VAN WINCKEL, S., 45, 91 PlTSCH, H., 85 SWEECK, L., 25 VAUNAT, J., 85, 87 PLAS, F., 86 SWINHOE, M., 89 VERDICKT, W., 86 POFFIJN, A., 5 VERETENNICOFF, L, 109 VERLAAK, M., 5 POMMÉ, S., 7,11 TARABRIN, YU., 110 VERMEERSCH, F., 3, 71, 105 PONNET, M., 62 THIENPONT, H., 109 VERREZEN, F., 11,66 PONSARD, B., 105 THIERENS, H., 3 POTT, G., 58 THIRY, Y., 22, 23 VERSTRICHT, J., 83, 86, 87 VERWERFT, M., 40, 54, 58 POULAKI, B., 31 THOLEY, J., 86 VERWILGHEN, B., 109 PRIJ, J., 83, 86 THOMAS, H. R., 87 VICINI, C, 67 PRISTER, B.S., 22 TOMASHUK, A., 110 VIDAL, M., 22 PUT, M., 83, 84, 86, 87 TONDEUR, F., 5 VIEIDER, G., 58 PUZZOLANTE, J.-L., 53, 54, 58 TROIANI, F., 87 VIENO, T., 86 TURBANG, D., 23 VILAR, M. V., 87 RAHIER, A., 62, 63 VILLAR, M., 85, 87 RAIMBAULT, P., 86 UYTTENHOVE, J., 11 VOLCKAERT, G., 83, 84, 85, 86, 87 RAMDAS, R., 86 RECREO, F., 86 VALCKE, E., 22, 83, 85 VOORBRAAK, W. P., 67 REMETTI, R., 67, 89 VALÓ, M.J., 45 VOS, F., 109 REYNERS, H., 31, 32 VAN ALSENOY, V., 62, 63, 68 RlSCH, P., 45 VAN BINNEBEEK, J.-J., 34 WACQUIER, W., 85, 87, 105 RIVAS, P., 87 VAN BRÜSSEL, H., 109, 110 WALRAVENS, J., 85, 86 ROBOUCH, P., 7 VAN CAUTEREN, L., 83 WAMBERSIE, A., 30 RÖHLIG, K., 83 VANDECASTEELE, CM., 22, 23, 31 WANG, L, 85, 86, 87 ROJAS PALMA, C., 16 VAN DEN DURPEL, L., 105 WANNIJN, J.-P., 54 ROMEYER DHERBEY, J., 67 VANDENHOVE, H., 22, 23 WARWICK, P., 83, 86 ROOFTHOOFT, R., 62, 63 VANDERBORCK, Y., 40 WEI, J., 85 RÚAN, D., 102, 103 VANDERLEE, J., 85, 86 WEMAERE, I., 83, 85, 86, 87 VANDERLINDEN, F., 54, 66 WERLE, H., 58 SAMAIN, J.-P., 34 VAN DER MEER, K., 40, 45, 67, 89 WIBIN, J., 87 SANDALLS, J., 22 VAN DER STEEN, J., 16 WICKS, G. G., 84 SANDEN, H.J., 67 VANDERVOORT, F., 87 WILLEKENS, V., 40 SANNEN, L., 40, 87 VAN DE VELDE, J., 53, 54 Wu, C.H., 58 SAUVAGE, S., 63 VANDEVELDE, L., 54 SCHALLER, R., 53 VAN DE WALLE, B., 16, 34 YAN, A.M., 53 SCHNEEFUSS, J., 87 VANGELDER, E., 34 YAN, J., 32 SCHRAUBEN, M., 71 VAN GOMPEL, M., 86 SCHROYEN, D., 40 VANHAVERE, F., 3 ZDRODOWSKI, K., 109 SCHULTZ, R. L., 84 VANHEES, M., 22,23 ZECH, C, 86 SCIBETTA, M., 53, 54 VAN HOVE, H., 34 ZEEVAERT, Th., 16, 25, 34 SCIOLLA, C, 45 VAN ISEGHEM, P., 58, 67, 83, 84, 85, 86, ZHOU, W., 85 SEN, A., 87 87

Authors 117 Partners, sponsors, and customers

This index lists the scientific partners, sponsors, and customers mentioned in this report, together with their usual abbreviation or acronym.

ANDRA Agence nationale pour la gestion des dechets radioactifs (Fontenay-aux-Roses, France), 82 AVN AIB-Vincotte Nuclear (Brussels, Belgium), 34 ARMINES Association pour la recherche et le developpement des methodes et processus industriels (Paris, France), 82 AEA Technology Atomic Energy Authority (Culham and Harwell, United Kingdom), 21,25, 53, 82, 98, 109 AECL Atomic Energy of Canada Ltd, Chalk River Laboratories (Chalk River, Ontario, Canada), 21 KFKI Atomic Energy Research Institute of the Hungarian Academy of Sciences (Budapest, Hungary), 6

— Belgatom (Brussels, Belgium), 70, 98 BGD/SGB Belgische Geologische Dienst/Service geologique de Belgique (Brussels, Belgium), 82 BN Belgonucleaire (Brussels, Belgium), 11, 15, 40, 45, 66 BP Belgoprocess (Dessel, Belgium), 11, 15, 66,70 BGS British Geological Survey (Nottingham, United Kingdom), 82 BNFL British Nuclear Fuels Ltd (Sellafield, United Kingdom), 40, 45

CLRP Central Laboratory for Radiological Protection (Warsaw, Poland), 25 CRIEPI Central Research Institute of Electric Power Industry (Tokyo, Japan), 45 CNT Centrale nucleate de Tihange (Tihange, Belgium), 11 CEBELCOR Centre beige d'etude de la corrosion (Brussels, Belgium), 82 CEPN Centre d'etudes sur 1'evaluation de la protection dans le domaine nucleaire (Fontenay-aux-Roses, France), 15 CIMNE Centro Internacional de Metodos Numericos en Ingenieria (Barcelona, Spain), 82 CIEMAT Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (Madrid, Spain), 25, 82, 109 CTMSP Centro Tecnologico da Marinha em Sao Paulo (Sao Paulo, Brazil), 53 — Chalmers University of Technology (Goteborg, Sweden), 82 CIAE Chinese Institute for Atomic Energy (Beijing, China), 82 — Clay Technology Lund AB (Lund, Sweden), 82 CEA Commissariat a l'energie atomique (Cadarache, Fontenay-aux-Roses, and Saclay, France), 5, 21, 30, 58, 82, 106 CEGELEC Compagnie generate d'electricite (Antwerp, Belgium), 98 CCE Controle de securite de l'Euratom (Brussels, Belgium), 11

DKFZ Deutsches Krebsforschungszentrum (Heidelberg, Germany), 30 DBIS/SPRI Dienst voor Bescherming tegen Ioniserende Stralingen/Service de protection contre les radiations ionisantes (Brussels, Belgium), 25, 34 — DSM Research BV (Geleen, the Netherlands), 6

JRC EC Joint Research Centre (Ispra, Italy), 15, 58 EIG PRACLAY Economic Interest Group PRACLAY (Mol, Belgium), 82 — Electrabel (Brussels, Belgium), 15, 53 EPRI Electric Power Research Institute (Charlotte, North Carolina, USA), 25, 53 EdF Electricite de France (Paris, France), 15, 45, 53, 62, 82 ENI Elektrische Nijverheid Installaties (Aartselaar, Belgium), 98 ENRESA Empresa Nacional de Residuos Radioactivos SA (Madrid, Spain), 25, 82 ECN Energieonderzoek Centrum Nederland (Petten, the Netherlands), 82 EWN Energiewerk Nord GmbH (Greifswald, Germany), 70 ERM Etudes-recherches-materiaux (Poitiers, France), 82 — Euratom (Luxemburg, Grand Duchy of Luxemburg), 66 EC European Commission (Brussels, Belgium), 5, 15, 21, 30, 47, 53, 58, 66, 70, 82, 109 ETC-OMRON European Technical Centre ('s Hertogenbosch, the Netherlands), 102

FPMs Faculte polytechnique de Mons (Mons, Belgium), 109 DWTC/SSTC Federate Diensten voor Wetenschappelijke, Technische en Culturele Aangelegenheden/Services federaux des affaires scientifiques, techniques et culturelles (Brussels, Belgium), 30 FORC Fibre Optics Research Centre (Moscow, Russia, NIS), 109 FZK Forschungszentrum Karlsruhe (Karlsruhe, Germany), 15, 47, 58, 82 FZR Forschungszentrum Rossendorf (Dresden, Germany), 15 — Framatome (Paris, France), 70 FBFC Int. Franco-beige de fabrication de combustibles International (Dessel, Belgium), 11, 40, 66 FhG Fraunhofer Gesellschaft (Euskirchen, Germany), 3, 109

118 Indexes — GEC Alsthom (Grenoble, France), 98 — GEOCONTROL (Madrid, Spain), 82 GRS Gesellschaft fur Anlagen- und Reaktorsicherheit (Braunschweig and Koln, Germany), 82 GSF Gesellschaft fur Strahlen- und Umweltforschung (Neuherberg, Germany), 25 G3S Groupement pour l'etude des structures souterraines de stockage (Paris, France), 82

— Imperial College (Ascott, United Kingdom), 21 INSERM Institut national de la sante et de la recherche medicale (France), 30 CEA-IPSN Institut de protection et de surete nucleaire (Fontenay-aux-Roses, France), 25, 82 IRE Institut des radioelements (Fleurus, Belgium), 34, 70 — Institut fur Strahlenhygiene, Bundesamt filr Strahlenschutz (Munchen, Germany), 30 IPEP Institute of Power Engineering Problems (Minsk, Belarus, NIS), 21 IRMM Institute for Reference Materials and Measurements (Geel, Belgium), 3, 6, 11, 15, 82 ISMES Institute Sperimentale Modelli E Strutture (Bergamo, Italy), 82 IARC International Agency for Research on Cancer (Lyon, France), 30 IAEA International Atomic Energy Agency (Vienna, Austria), 66, 70

— Jozef Stefan Institute (Ljubljana, Slovenia), 15

KUL Katholieke Universiteit Leuven (Leuven, Belgium), 21, 56, 82, 109 — KEMA Nuclear (Arnhem, the Netherlands), 15,82 KCD Kemcentrale Doel (Doel, Belgium), 11 KAERI Korean Atomic Energy Research Institute (Taejon, South Korea), 45 — KRB-A Kraftwerk (Gundremmingen, Germany), 70 — Kurchatov Institute (Moscow, Russia, NIS), 53, 106, 109

— Laborelec (Linkebeek, Belgium), 56

MEA Materials Engineering Associates Inc. (Lanham, Maryland, USA), 53 MLURI McAulay Land Use Research Institute (Aberdeen, United Kingdom), 21 — Ministry of Internal Affairs (Brussels, Belgium), 34 MHI Mitsubishi Heavy Industries Ltd (Yokohama, Japan), 40, 45 MEPhI Moscow State Engineering & Physics Institute (Moscow, Russia, NIS), 106 — Mouchel & Partners Ltd (Surrey, United Kingdom), 21,25

— National Centre for Scientific Research Democritos (Athens, Greece), 30 RIVM National Institute of Public Health and Environmental Protection (Bilthoven, the Netherlands), 25 NIST National Institute of Standards and Technology (Gaithersburg, Maryland, USA), 6 NOI-INO National Optical Institute/Institut national d'optique (Quebec, Canada), 109 NRPB National Radiological Protection Board (Didcot, United Kingdom), 15, 25, 30 NIRAS/ONDRAF Nationale Instelling voor Radioactief Afval en Verrijkte Splijtstoffen/Organisme national des dechets radioactifs et des matieres fissiles enrichies (Brussels, Belgium), 15, 21, 25, 66, 82 NFI Nuclear Fuel Industries Ltd (Osaka, Japan), 40, 45 NRI Nuclear Research Institute (Rez, Czech Republic), 25

ORNL Oak Ridge National Laboratory (Oak Ridge, Tennessee, USA), 53 HRP OECD Halden Reactor Project (Halden, Norway), 106

PSI Paul Scherrer Institute (Villingen, Switzerland), 21, 25, 30, 91 TNO Physics and Electronics Laboratory (JG the Hague, the Netherlands), 102 PSRER Polessky State RadioEcological Reservation, 21 UPC Polytechnic University of Cataluna (Barcelona, Spain), 82 UPM Polytechnic University of Madrid (Madrid, Spain), 82

— QuantiSci Ltd (Henley-on-Thames, United Kingdom), 82

MARCQ & ROBA Raadgevende ingenieurs voor technische uitrusting van gebouwen (Brussels, Belgium), 98 RIR Research Institute of Radiology (Gomel, Byelorussia, NIS), 21 RUCA Rijksuniversitair Centrum Antwerpen (Antwerpen, Belgium), 53 — RiS0 National Laboratories (Roskilde, Denmark), 15, 21 RIAR Russian Institute for Agricultural Radiology (Obninsk, Russia, NIS), 21

Partners, sponsors, and customers 119 SPA Typhoon Scientific Production Association Typhoon (Obninsk, Russia, NIS), 15,25 SENES Senes Oak Ridge Inc.'(Oak Ridge, Tennessee, USA), 25 SdM Societe de microelectronique (Charleroi, Belgium), 109 GEOSTOCK Stockage souterrain (Rueil-Malmaison, France), 82 — Studsvik Eco&Safety (Nykoping, Sweden), 15, 25 — Studsvik Instrument (Nykoping, Sweden), 106 — Studsvik Radwaste (Studsvik, Sweden), 70 — Sumitomo (Tokyo, Japan), 70 SSI Swedish Radiation Protection Institute (Stockholm, Sweden), 5, 25 SLU Swedish University of Agricultural Sciences (Uppsala, Sweden), 21

VTT Technical Research Centre of Finland (Espoo, Finland), 25, 53, 82 — Technical University of Delft (Delft, The Netherlands)), 82 TVO Teollisuuden Voima Oy, Development Office (Helsinki, Finland), 82 — Tractebel (Brussels, Belgium), 82 TEE Tractebel Energy Engineering (Brussels, Belgium), 47, 53, 56 TUI Transuran Institut (Karlsruhe, Germany), 91

UIAR Ukrainian Institute for Agricultural Radiology (Kiev, Ukraine, NIS), 21 USNRC United States Nuclear Regulatory Commission (Washington, DC, USA), 53 UFSIA Universitaire Faculteiten Sint-Ignatius Antwerpen (Antwerpen, Belgium), 34 — Universitatsklinikum Essen (Essen, Germany), 30 UCL Universite catholique de Louvain (Louvain-la-Neuve, Belgium), 15, 21, 30, 53, 82 ULB Universite Libre de Eruxelles (Brussels, Belgium), 47, 58, 82,109 ULg Universite de Liege (Liege, Belgium), 11, 30, 82 UPS Universite de Paris-Sud (Orsay, France), 82 UG Universiteit Gent (Gent, Belgium), 3, 5, 6, 11, 15, 53,102 — University of Aachen (Aachen, Germany), 30 — University of Aberdeen (Aberdeen, United Kingdom), 82 — University of Athens (Athens, Greece), 30 — University of Barcelona (Barcelona, Spain), 21, 30 — University of Birmingham (Edgbaston, United Kingdom), 82 — University College of Dublin (Dublin, Ireland), 5 — University of Coruna (Coruna, Spain), 82 — University of Exeter (Exeter, United Kingdom), 82 — University of Freiburg (Freiburg, Germany), 30 — University of Hannover (Hannover, Germany), 70 — University of Krakow (Krakow, Poland), 30 — University of Leeds (Leeds, United Kingdom), 15 — University of Loughborough (Loughborough, United Kingdom), 82 — University of Lund (Lund, Sweden), 5, 21 — University of Manchester (Manchester, United Kingdom), 15 — University of Maryland (Maryland, USA), 47 — University of Roma (Rome, Italy), 82 — University of Uppsala (Uppsala, Sweden), 30 — University of Veszprem (Veszprem, Hungary), 25 UWCC University of Wales, College of Cardiff (Cardiff, United Kingdom), 82 — University of Warwick (Warwick, United Kingdom), 15

VLTO Vlaamse Instelling voor Technologisch Onderzoek (Mol, Belgium), 82 VUB Vrije Universiteit Brussel (Brussels, Belgium), 3, 11, 47, 56, 82, 109

WSC Westlakes Scientific Consulting (Moor Row, United Kingdom), 15 WTV-LP Wetenschappelijk Instituut Volksgezondheid/Institut Scientifique de la Sante Publique, Louis Pasteur (Brussels, Belgium), 34 WTCB/CSTC Wetenschappelijk en Technisch Centrum voor het Bouwbedrijf/Centre scientifique et technique pour la construction (Limelette, Belgium), 70, 98

— Yale University (New Haven, Connecticut, USA), 3 — Yankee Atomic Electric Company (Bolton, Massachusetts, USA), 53

120 Indexes Edition and typesetting JL Consulting, Kortenberg

Printing Enschede, Brussels

Editor responsible Paul Covaerts Boeretang 200, B-2400 Mol, Belgium Besides this Scientific Report, SCK-CEN publishes an annual report (available in English, Flemish, and French) and various brochures describing its activities. To obtain any of these documents, please contact Anne Verledens.

To better respect the environment, SCK-CEN prints its annual reports on chlorine-free paper.