10. Emergency Preparedness

CH9900055 Annual report 1993 concerning the nuclear safety and radiological protection in the Swiss nuclear installations

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Hauptabteilung fur die Sicherheit der Kernanlagen Division principale de la Securite des Installations Nucleaires Divisione principale della Sicurezza degli Impianti Nucleari Swiss Federal Nuclear Safety Inspectorate

3 1-01 Annual report 1998 concerning the nuclear safety and radiological protection in the Swiss nuclear installations

May 1998 HSK-AN-3535 KSA-AN-2062

Cover picture The pictures show various activities of the Inspectorate (HSK) during 1998

HSK Annual report 1998 Content

Preface 6

Summary 9

Organisation 12

1. Beznau Nuclear Power Plant. 13 1.1 Operational data and results 13 1.2 Plant safety 13 1.3 Radiation Protection 16 1.4 Personnel and organisation 17 1.5 Emergency preparedness 17 1.6 Radioactive waste 18 1.7 Overall judgement by the Inspectorate 18 2. Miihleberg Nuclear Power Plant 19 2.1 Operational data and results 19 2.2 Plant safety 19 2.3 Radiation protection 23 2.4 Personnel and organisation 24 2.5 Emergency preparedness 24 2.6 Radioactive waste 25 2.7 Overall judgement by the Inspectorate 25

3. Gosgen Nuclear Power Plant . 27 3.1 Operational data and results 27 3.2 Plant safety 27 3.3 Radiation protection 29 3.4 Personnel and organisation 31 3.5 Emergency preparedness 31 3.6 Radioactive waste 31 3.7 Overall judgement by the Inspectorate 32

4. Leibstadt Nuclear Power Plant 33 4.1 Operational data and results 33 4.2 Plant safety 33 4.3 Radiation protection 36 4.4 Personnel and organisation 38 4.5 Emergency preparedness 38 4.6 Radioactive waste 39 4.7 Fulfilment of regulatory requirements 39 4.8 Overall judgement by the Inspectorate 39

5. Central Interim Storage, Wurenlingen 41 5.1 Supervision of construction 41 5.2 Review for operation license for the waste treatment plants .... 41 5.3 Waste from reprocessing 42 5.4 Provision of transport and storage casks 42

6. Paul Scherrer Institute (PSI) 43 6.1 The PSI in Villigen and Wurenlingen 43 6.2 Research reactors 43 6.3 Accelerator, proton beam channels and experimental areas 44 6.4 Hot Laboratory 46 6.5 Treatment of radioactive waste 46 6.6 Storage of radioactive waste 48 6.7 Emergency preparedness 48

HSK Annual report 1998 6.8 Particular events 49 6.9 Radiation protection 49 6.10 Personnel and organisation 49 6.11 Overall judgement 50

7. Other Nuclear Installations 51 7.1 Ecole Polytechnique Federale de Lausanne (EPFL) 51 7.2 University of Basle 51 7.3 Experimental reactor at Lucens (VAKL) 51

8. Disposal of radioactive waste 53 8.1 Wellenberg repository 53 8.2 Repository for high-level waste: preparatory measures 53

9.Transport of Radioactive Materials 55 9.1 Permits and approvals according to transport legislation 55 9.2 Authorisations according to radiation protection legislation 56 9.3 Inspections and audits 56 9.4 Training and information 56 9.5 Contamination associated with the transport of spent fuel 56

10. Emergency Preparedness 59 10.1 The Inspectorate's emergency organisation 59 10.2 Planning for protection in the case of emergencies 59 10.3 Training activities in the area of emergency protection 60 10.4 MADUK and ANPA 60 10.5 Basis for atmospheric dispersion calculations 61 10.6 Social aspects in connection with decision-making following an accident 62

11. Regulatory inspections 63 11.1 General aspects concerning regulatory inspections 63 11.2 Regulatory inspections in connection with the examination of probabilistic safety analyses 64 11.3 Unannounced technical regulatory inspection as a consequence of an event at the Muhleberg nuclear power plant (KKM) 65 11.4 Regulatory inspections in connection with aspects of radiation protection during periodic inspections at the Leibstadt nuclear power plant (KKL) 65

12. Selected Aspects of Nuclear Safety and Radiation Protection 67 12.1 Guidelines 67 12.2 Instructive events in foreign nuclear installations 67 12.3The year 2000 date change problem 69 12.4 Organisational factors and safety culture 70 12.5 Commission for the safety of nuclear installations 71 12.6 IRRT: IAEA experts assess the Inspectorate 71 12.7 Procedure in connection with the evaluation of events 72 12.8 Developments and tendencies in the area of periodic inspections 73

13. Safety research 75

14. PSI Schools 83 14.1 Reactor School 83 14.2 School for Radiation Protection 83

15. International aspects 85 15.1 "Convention on Nuclear Safety" (CNS) 85 15.2 Waste convention 86 15.3 Bilateral contacts with other countries 86

HSK Annual report 1998 Appendix A 89 Appendix B 119 List of Publications in 1998 128 List of Abbreviations.... 130

HSK Annual report 1998 in future, nuclear safety will be confronted, 3.74 Person-Sv), the most intensive supervi- world-wide, with significant and partly new sion by the Inspectorate (519 technical inspec- challenges. Various causes contribute to this: tions), but also a huge shock, which led to a crisis of confidence within the public. - The nuclear power plants are becoming The fact that patches of contamination on older and a discussion is going on concern- the casks, or on the railway wagons, occurred ing their possible lifetime extension. This relatively frequently during the transportation places high requirements on maintenance of spent fuel, and that this fact was neither and the surveillance of ageing. notified nor questioned, became a topic of media interest over many months. In Switzer- - Deregulation of the market for electricity land, the permits for transportation were sus- leads to enormous cost pressures, which pended and the whole situation was investi- must not be allowed to detract from safety. gated in great detail. The Inspectorate used the dynamics of this - The founder generation for nuclear power is situation to ask relevant questions about itself, now of pensionable age and this can lead to its work procedures and its priorities. It allowed a loss of know-how. Valuable pieces of com- itself to be audited by an International Regula- prehensive knowledge concerning cross- tory Review Team (IRRT), consisting of a group connections between various areas of nu- of eleven recognised experts from seven coun- clear safety threaten to become lost. tries. With the benefit of hindsight, the whole process can be seen as a painful, but very in- - In the western world, there are virtually no structive and stimulating exercise in reposition- large new projects in the area of nuclear ing. The IRRT taught us, in particular, that su- power, which leads to a lack of interest in pervision cannot be restricted to a mere universities, research institutes and engi- continuation of expert assessment. During neering firms. Collectively, specialist knowl- appraisal, the focus is on technology (plants, edge is shrinking; recruitment of new staff systems, components), whereas in the con- becomes more difficult. text of supervision, organisational aspects (operators and work procedures) become ever - In the near future, hard-wired instrumenta- more important. tion and control technology will have 1998 was also the year in which every coun- reached the end of its life-span. Already to- try, which had ratified the Convention on Nu- day, certain spare parts are not always avail- clear Safety, had to provide an assessment of able.The leap to digital technology for instru- its own position in the form of a report. Swit- mentation and control is unavoidable. New zerland satisfies the requirements of this con- types of event or accident sequences can vention. However, 2 of these requirements led occur because of the possibility of hidden to a variety of discussions, because they could bugs in the software and the concentration not be fulfilled, to date, without encountering of so many functions in the computers. difficulties:

The Inspectorate is meeting these challenges - Quality assurance and quality management in an engaged and positive way. It is active on in the Swiss nuclear power plants, and at all fronts in order to continue to carry out its the Inspectorate itself, are not yet of the tasks competently and reliably in the future. standard which one would ideally like them This is evident, e.g., in the establishment and to have attained. precise planning of our internal work procedures. - The independence of the Inspectorate, as In 1998 especially, certain of these chal- the Swiss nuclear regulatory authority, is not lenges already became perceptible. For us, it yet sufficiently established in law. This defi- was a year of superlatives: the fewest number ciency should rapidly be a thing of the past of classified events in the nuclear power plants as a result of the Federal Council's intention (only 5), the lowest collective dose for the to- to establish an independent "National tal personnel in the nuclear power plants (only Safety Agency" (NASA).

HSK Annual report 1998 Summarising, it can be said that certain challenges, which beforehand were only just becoming visible, appeared, with astonishing speed, in a concrete form during 1998 and tested our vitality and ability to react. We were shocked, but recovered and reacted in an en- ergetic way. The resulting improvement in ef- ficiency is still in progress.

Dr. S. Pretre, Director of the Swiss Federal Nuclear Safety Inspectorate (HSK).

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HSK Annual report 1998 Summary

General aspects the IRRT recommendations and suggestions The Swiss Federal Nuclear Safety Inspectorate will characterise the future work and the or- (HSK), hereafter called the Inspectorate, ap- ganisation of the Inspectorate. praises the Swiss nuclear installations and supervises their operators. It assesses the Regulatory activity nuclear safety and the radiation protection of Regulation of the Swiss nuclear power plants these plants.Through inspections, and through of Beznau, Gosgen, Leibstadtand Muhleberg, reports received from the operators, the In- as well as the nuclear installations of the Paul spectorate obtains an objective picture of their Scherrer Institute (PSI), was once again in the technical condition with regard to safety, as forefront of the Inspectorate's activity in 1998. well as of their adherence to prescribed pro- The main regulatory pronouncements and cedures and of their operational management. appraisals regarding the nuclear power plants The Inspectorate prepares guidelines which are to be found in Chapters 1 to 4 of the are of a directional nature for the operators. present annual report. Chapter 5 deals with the Together with other federal agencies, further central interim storage facility (ZWILAG) at regulatory documents concerning the use of Wurenlingen and Chapter 6 with PSI. Chapter nuclear power, nuclear plants, nuclear safety 9 is devoted to the transport of radioactive and radiation protection are prepared or, if nec- materials, whereby attention is paid, in particu- essary, updated. lar, to the problems of contamination which The Inspectorate writes expert reports for occurred on several occasions during the the attention of the Federal Council.These re- transport of spent fuel for reprocessing in La ports are used by the Council as a basis for Hague (F) and Sellafield (GB). deciding upon the approval of applications Safety technology has, in general, reached made by the operators of nuclear power a high level in the last decade. What is the situ- plants. ation, however, with the human beings who The Inspectorate maintains its own emer- operate machinery and plant? To what extent gency organisation, which goes into action in should human beings be regarded as a risk the case of a nuclear event in the Swiss nu- factor in the assessment of processes and clear installations. This is a part of the nation- safety requirements?The thought processes, wide emergency organisation. actions and behaviour of operational personnel The Inspectorate provides information, both ("the human factor") are included in such con- during normal operation and also in the case siderations. This aspect also forms part of the of incidents in Swiss nuclear power plants, on supervision and appraisal work of the Inspec- aspects of nuclear safety and radiation protec- torate. Explanations and assessments of this tion, as well as on its own activities. It attempts topic are dealt with in Sections 1.4 to 4.4 ("Per- to inform the media and the public compe- sonnel and organisation") and in Section 12.4 tently, rapidly, openly and in an expert manner. (organisational aspects and safety culture) of The considerable expertise, and the specialist the present report. knowledge, of its staff becomes part of the The nuclear power plants are also getting information products produced as, e.g., in the older, so that the question of the operational case of this annual report for 1998. behaviour of safety-relevant parts and compo- The year 1998 was characterised by the in- nents arises. The ageing surveillance pro- cidents of unallowable contamination during gramme, which was initiated by the Inspector- the transportation of spent fuel to the reproc- ate, has a special place in the regulation of essing plants in France and Great Britain. In nuclear power plants and deals with the age- December, the expert mission of an Interna- ing of various parts of the plant and compo- tional Regulatory Review Team (IRRT) from the nents, in the context of the plant maintenance International Atomic Energy Agency (IAEA) to concept. To date, investigations carried out the Inspectorate formed a milestone in the within this programme have revealed no par- Inspectorate's history. These specialists as- ticular gaps in the existing maintenance and sessed the work procedures, the organisation ageing inspection programmes. and the position of the Inspectorate. Several of

HSK Annual report 1998 Overall impression of the nuclear power radiation protection, and that the outside sur- plants faces of the casks had not been cleaned to a The Inspectorate describes its overall impres- sufficient extent. The transportation casks sion of the state and operation of the nuclear themselves, however, had been completely power plants at the end of Chapters 1 to 4, and leak-tight with all transports at all times; thus of PSI at the end of Chapter 6. In general, the no radioactivity from the transported fuel had Inspectorate concludes that the condition and entered the environment. operational management of all Swiss nuclear At the beginning of May, 1998, the Federal power plants is good with regard to nuclear Office of Energy (BFE) suspended all permits safety and radiation protection. It is satisfying for the transportation of spent fuel from Swit- that the values for yearly collective doses are zerland for reprocessing abroad. This suspen- low in all nuclear power plants. This is partly a sion was still in force at the end of 1998. Analy- result of the extensive radiological shielding ses were carried out as to the causes of the measures adopted, especially during the main- problem and the Swiss nuclear power plant tenance shutdown. Once again, during the operators were required to present measures year under review, the Inspectorate gave per- for the avoidance of contamination to the In- mission to re-start the nuclear power plant spectorate. In turn, the Inspectorate was re- units following their revision shutdowns. quired to produce an official report on this topic for the authorities. Expert reports Contamination during the transportation of The plant operators must submit applications, spent fuel became a topic of great public im- with accompanying safety documentation, for portance in the media and the parliaments of planned projects such as, e.g., construction of the affected countries. Public reaction was an interim storage facility for radioactive waste. very strong, even though the radiological sig- The Inspectorate examines these applications nificance and the risk associated with these and plans, and prepares expert reports of a incidents were extremely low. The Inspector- technical/scientific nature on them. In this ate reports in detail on contamination during work, the Inspectorate adheres to national the transportation of spent fuel in Chapter 9 of codes and to the established, international sta- this annual report. tus of science and technology. These expert reports of the Inspectorate serve the Federal Codes and assessment criteria Council as the basis for decisions upon the The Inspectorate's guidelines and recommen- granting of licences according to Swiss Atomic dations are the criteria used to assess the ac- Law. tivities and projects of the Swiss nuclear power During the year under review, the Inspector- plant operators. They also lay down what is ate started to prepare an expert report on op- required from the operator, e.g. with regard to eration of the conditioning plant, as well as the notifiable events, and what is expected of him. incineration and melting plant, at the central The guidelines are intended to provide a sound interim storage facility in Wurenlingen. This basis in law. expert report will be completed in 1999 (see During the year under review, the Inspector- Chapter 5). ate put into effect two revised guidelines, namely HSK Guideline R-12, concerning the Transportation of fuel assemblies measurement and notification of the doses During the last few years, unallowable con- received by personnel exposed to irradiation in tamination of casks and the inside of railway the nuclear power plants and the Paul Scherrer wagons had repeatedly occurred during the Institute, and R-25, concerning reporting re- transportation of spent nuclear fuel from Ger- quirements on the Paul Scherrer Institute, as man, French and Swiss nuclear power plants well as the federal and cantonal nuclear instal- to the reprocessing plants at La Hague (F) and lations. Sellafield (GB).The Inspectorate was informed of this at the end of April, 1998 by the French Preparatory measures for final storage nuclear safety authority DSIN. Contamination The project for the final storage of low and in- in excess of the internationally accepted, de- termediate level radioactive wastes atWellen- 2 rived limit of 4 Bq/cm had occurred during berg in the canton of Nidwalden is still blocked. 1997 and 1998 with seven transports under- In 1998, the Federal Government working way from the Swiss nuclear power plants to La group, in which the Inspectorate participates, Hague. The occurrence of such impurities with discussed fundamental questions concerning the consignments was attributable, in the the project and its continuation. It confirmed main, to the fact that loading of the casks has the probable suitability of the site for final stor- to be carried out under water, for reasons of age and recommended that further investiga-

10 HSK Annual report 1998 tions should be carried out in stages, the first maintains its own emergency organisation, involving construction of an exploratory tunnel. guaranteeing the continual availability of a spe- Research work was continued in preparation cialist shift technical advisor. In the case of for final certification concerning the final stor- severe accidents in nuclear installations, the age of high-level and long-lived, intermediate Inspectorate provides guidance and advice, in level waste. The National Co-operative for the particular to the national alarm centre (NAZ). It Storage of Radioactive Waste (Nagra) is work- relies, hereby, upon its own measurements, ing on basic aspects of this which concern the analyses and diagnosis. host rock formations opalinus clay and crystal- Decision-making criteria are made available line base.The emphasis in the near future will by the Inspectorate for the planning of emer- be on exploration of the opalinus clay in the Zu- gency protection measures. The Inspectorate rich Weinland area.. During the year under re- carries out special training and exercises in the view, work was started on the exploratory area of emergency preparedness for its own borehole at the Benken site (see Chapter 8). staff. Chapter 10 of the present annual report The Inspectorate is following this geological contains information on emergency prepared- work. ness, emergency exercises, the MADUK measuring network, etc.. Safety research and the current status of science and technology IRRT - IAEA experts visit the Inspectorate The Inspectorate's basis for assessing safety How does the Swiss nuclear regulatory author- in the Swiss nuclear installations includes con- ity work? In what way are the tasks assigned sideration of the current status of science and to this authority dealt with? How is the author- technology. Certain requirements concerning ity organised? In the first half of December, measures to improve safety in the plants also 1998, an international team of experts (IRRT) result from this. In order to deal appropriately from the IAEA looked into these and related with this aspect of its work, the Inspectorate questions. This team examined and assessed initiates and supports both national and inter- the work procedures, duties, and degree of national research projects in the area of regu- expertise of the Inspectorate, as well as the latory safety research. framework within which it operates. The mis- These projects are of practical value to the sion took place as the result of an official invi- Inspectorate in its supervisory and appraisal tation, issued by the head of department at the work. Within the framework of safety research, Federal Department for Environment, Trans- a broad range of topics is covered, spanning port, Communication and Energy (UVEK).The the areas of radioecology, radiological sensitiv- experts gave the Inspectorate good marks in ity, the behaviour of radionuclides in rivers, the areas of safety analyses, technical assess- stress corrosion cracking, the HRA project ments, radiation protection and emergency (which considers the effect of human actions preparedness. They expressed criticism, on the course of nuclear events), and investi- among other things, with regard to the way in gations into the behaviour of fuel and compo- which the Inspectorate has, to date, carried out nents within the nuclear power plants. Chap- inspections in the plants. Further details on this ter 13 describes the safety research projects are contained in Section 12.6. supported by the Inspectorate. Personnel and training activities Emergency preparedness Training and further education of personnel is In Switzerland, who is responsible, in what way an area of special importance to the Inspector- and to what extent, if radioactivity is released ate, both with regard to its own staff and staff to the environment as the result of an acci- from the nuclear plants. In particular, the In- dent? Among other things, this is dealt with by spectorate supervises the training of special- the regulation on emergency organisation for ist personnel in the plants, e.g. operators.The the case of increased radioactivity (VEOR).This Inspectorate's staff act as experts and exam- regulation governs the responsibility, organisa- iners in the context of specialist examinations tion and assignment of federal agencies in at the PSI reactor and radiation protection cases of increased radioactivity.The Inspector- schools (see Chapter 14). ate has an advisory role in this context and

HSK Annual report 1998 11 Swiss Federal Nuclear Safety Inspectorate (HSK)

Organisation Director: S. Pretre, Dr. 1. Deputy: W. Jeschki 2. Deputy: U. Schmocker, Dr. March 1999

Team leaders

Section Staff Head: S. Pretre, Dr. Head: G. Schwarz, Dr. W. Jeschki A. R. Schneider Dir. secretary: U. Schmocker, Dr. Computing: Head: P. Schmid J. Noggerath, Dr. Information and Safety Research Swiss Federal Nuclear G. Schwarz, Dr. Library Head: A.Treier and International Safety Commission: Programmes (SFI) Scientific Advisor Secretariat (KSA) Head: S. Chakraborty R. Gilli Head: B. Hollenstein

Division for Mechanical and Division for Reactor Design Division for Radiation Protection and Electrical Equipment (MELA) and Safety Analysis (RASA) Emergency Preparedness (SANO)

Head: J. Noggerath, Dr. Head: U. Schmocker, Dr. Head: W. Jeschki Deputy: A. Voumard Deputy: W. van Doesburg, Dr. Deputy: J. Hammer, Dr.

Supervision PS1 Secretariat | Secretariat J. Hammer, Dr.

Section for Section for Section for Section for Section for Section for Section for Section for Section for Section for Coordination Electrical and Mechanical Reactor and Prob. Safety Personnel, Accidents Radiation Occupational Radioactive of NPP Control and Civil Safety Analysis and Organisation conseq. and Measurement Radiological Waste Supervision Engineering Engineering Technology Accident and Safety Emergency Techn. and Protection Management Management Culture Preparedness Radioecology (KOA) (ELT) (MBT) (RST) (PSA) (MOS) (SUN) (MER) (RAS) (ERA) Head: Head: Head: Head: Head: Head: Head: Head: Head: Head: H. G. Lang A. Voumard J. Nbggerath, Dr. W. van Doesburg, Dr. U. Schmocker, Dr. A. Frischknecht, Dr. M. Baggenstos F. Cartier, Dr. M. Furrer, Dr. A. Zurkinden, Dr. 1. Beznau Nuclear Power Plant

Units 1 and 2 of the Beznau nuclear power plant. In the foreground can be seen the new interim storage building for radioactive waste ZWIBEZ.

1.1 Operational data and The thermal energy fed into the district heat- results ing supply system (REFUNA) amounted in The Beznau Nuclear Power Plant (KKB), belong- 1998 to a total of 151.1 GWhth for both units. ing to Nordostschweizerische Kraftwerke During the year under review, Unit 1 had no (NOK), consists of two virtually identical, dual- unplanned reactor scram. Afaultinthe control loop, pressurised water reactor units (KKB1 system of one turbine unit led to a reduction and KKB 2) which went into operation in 1969 to 50 % reactor power. A mistake during main- and 1971 respectively. As a result of different tenance work on the control circuitry led to a backfitting measures with corresponding im- brief power reduction of 15% in one turbine provements to the power rating of both units, unit. the net electrical outputs are as follows: Unit Unit 2 also had no unplanned reactor scram. 1 with 365 MW and Unit 2 with 357 MW. Ad- During start-up after the annual maintenance ditional data are summarised inTables A1 and revision, a reactor power reduction to 50% B3 of the Appendix. Figure B1 shows the func- occurred as a result of a turbine scram in the tional diagram of a pressurised water reactor course of final tests on a generator excitation plant. system. Power was also reduced by 20% in Units KKB 1 and KKB 2 performed in 1998 order to repair a cooling water leakage in the with a load factor1 of 99.7 % and 87.0% remain condenser of one turbine unit. spectively and availability factors2 of 100 % and 88.9 % respectively, whereby the proportion of unproductive time for Unit 2 is due pri- 1.2 Plant safety marily to the planned revision outage for refuelling and maintenance. 1.2.1 Particular events The revision outage for refuelling and main- The following notifiable events were reported tenance, which, due to lengthened operational by the operator, according to the Inspector- cycles, was only carried out this year in Unit 2, ate's Guideline R-15. lasted 41 days. In Unit 1, the following event was allocated to class B according to the Inspectorate's Guideline R-15 and to level 0 on the interna- Load factor (in %): energy actually produced as a per- tional nuclear event scale, INES (see Section centage of rated power at 100% availability. 12.7 and Appendix, Table B2). : Availability (in %): time that the plant is operating or is - A non-allowable deviation of the set values available for power generation. from the requirements of the technical

HSK Annual report 1998 • Beznau Nuclear Power Plant 13 specifications, which had been in existence since 1988, was noted during testing of two main steam pressure switches, which took place for the first time during power operation. Organisational deficiencies were the cause of the faulty setting. The deviation was so small that it would have had no negative effects on main steam isolation in the case of required operation. The set values were corrected immediately. In Unit 2, one event was also allocated to class B according to the Inspectorate's Guideline R- 15 and to level 0 on the international nuclear event scale, INES. - During preparation for reactor start-up following the maintenance revision, the reserves of borated water required, according to the technical specification, during filling of the primary circuit were not adhered to and the time period allowed for refilling was exceeded. The causes were deficiencies in internal communication and in the system for managing the supply of borated water. After supplementing the reserves of borated water, the operator prescribed measures to improve the weak-points discovered in the organisation and in the operating instructions. Evaluation of the 1998 events shows that improvements in the human/machine interface and in the technical organisation are necessary to avoid such events.

1,2.2 Work during the refuelling outage in Lifting the reactor pressure vessel closure head, includ- Unit 2 ing the control rod drives. Temporary lead shielding pro- Routine tasks, such as refuelling, electrical and tects the personnel against radiation. Source NPP Beznau mechanical testing, periodic inspections and tests of components and systems, as well as replacement of the steam generators. Further maintenance and modification work, were car- work included backfitting of the crane within ried out during the shutdown outage of Unit 2 the containment for transport of the steam from April 6th till May 15th. generators and the relaying of cable ducts in- One central activity was periodic inspection cluding cables. The access areas to the future of the reactor pressure vessel (RPV). Both the steam generator manholes were modified. flange weld and the circumferential dome weld Extensive revision work was carried out in of the RPV head were tested ultrasonically the area of the recirculation sump, which is im- using mechanised procedures. No indications portant for safety injection. In the course of relevant to safety were found during this first this, ferritic components were replaced in cor- volumetric inspection since manufacture. rosion-resistant material and the base and The tubing of both steam generators was walls of the sump were protected by suitable subjected to eddy current testing for the last coatings. time before their replacement in 1999. As a result of these inspections, 106 tubes were re- 1.2.3 Plant modifications paired using explosive sleeves and 3 tubes were During the year under review, plant modifica- sealed at both ends using expansion plugs. tions were made in Unit 2. Significant are: Preparation work for the planned steam - Oil collection and drainage devices were generator replacement in 1999 already played backfitted in order to prevent ignition of oil a major role during the shutdown. Preparatory on the hot pump casing in the event of a activities were carried out in order to facilitate continuous loss of oil from the bearings of a transport penetration in the missile protec- the main reactor coolant pump motors. tion wall of the containment so as to permit

14 HSK Annual report 1998 • Beznau Nuclear Power Plant - The complete core instrumentation for the determine the effect of plant and specification source and intermediate ranges was re- modifications, or of Inspectorate require- placed by a broadband neutron measurements, on the risks.The Inspectorate supports ment system.This state-of-the-art modifica- these activities, since they enable a more bal- tion required extensive installation work and anced assessment of safety in the context of careful testing, which was monitored risk-informed regulation. closely by the Inspectorate. Commissioning In the course of an audit, KKB answered the was carried out as planned. Inspectorate's questions with regard to the - The work on modernisation of the systems present situation and to future projects in the for site demand and emergency supply, framework of systematic introduction of Se- which had been started in previous years, vere Accident Management Guidance (SAMG). was more or less completed this year with SAMG represents a systematic extension of replacement of the transformers for site de- the regulations for dealing with malfunctions mand and excitation systems, including the and accidents towards guidelines for use even associated cabling. with very serious accidents involving core meltdown. In particular, efforts have been 1.2.4 Fuel elements and control rods made in this area to develop a guideline for There were no indications of fuel defects in control of the hydrogen problem with severe either of the KKB Units during the year under accidents. The goal here is to guarantee con- review, since no increased concentration of tainment integrity, as the last barrier for hold- fission products was measured in the reactor ing back radioactive substances, during all con- coolant. ceivable accident sequences. No refuelling was carried out in Unit 1 because of the extended fuel cycle. The three 1.2.6 Ageing surveillance programme fuel rods from three fuel assemblies which had Since 1996, KKB has followed an ageing sur- failed in this unit in 1997 (see the 1997 annual veillance programme (ASP) as a permanent report) were inspected in detail by the fuel task for its safety-relevant plant components. supplier. The primary cause of damage could In the area of mechanical engineering compo- only be established in the case of one rod.This nents belonging to safety class 1, the Inspec- was due to a manufacturing defect. torate examined and assessed the ASP docu- During refuelling in Unit 2, 32 new fuel as- mentation for reactor coolant piping, reactor semblies were loaded. The reactor core con- coolant pumps and the pressuriser during the tains 4 uranium/plutonium mixed oxide fuel year under review. Furthermore, technical dis- assemblies (MOX). 108 of the 121 fuel assem- cussions were carried out concerning special blies include a debris filter in the lower tie plate. questions of ageing effects on mechanical Measurements of the control rod drop inser- components. 1 E classified electrical compo- tion times showed that the reactor can be shut nents (e.g. pressure transducers, valve drives, down as required. motors, cables and plugs) are monitored for During the year under review, no transport ageing effects in KKB according to a guideline shipments of discharged fuel assemblies for approved by the Inspectorate. This ageing sur- reprocessing were made. veillance programme was continued in an appropriate way, including the provision of inter- 1.2.5 Probabilistic safety analysis (PSA) mediate reports on long-term experiments. and Accident Management In the area of structural engineering, the In accordance with an Inspectorate require- Inspectorate also examined the ASP documen- ment of 1990, KKB submitted its plant specific tation for the reactor building. Base-line inspec- PSA study for the plant modes of start-up, tions of buildings within the earthquake clas- shutdown and cold shutdown (Low Power and sification 1 (EK1) are in progress according to Shutdown (LP&S) PSA) at the end of 1998. The an ASP guideline approved by the Inspector- Inspectorate will commence its expert assess- ate. ment of this study in 1999. In 1998, KKB con- To date, the ASP documentation examined tinued revision work on the PSA study for op- by the Inspectorate has not revealed any eration of the plant at full power. In the course safety-relevant gaps in the maintenance proof 1999, KKB intends to submit to the Inspec- grammes. Furthermore, the present results torate an updated, full power PSA according to indicate that no unacceptable reduction in the state of the art. safety-related properties is to be expected in KKB now uses the PSA study as an addi- the near future. tional criterion in the context of applications for modifications and in providing answers to the Inspectorate's questions. The goal here is to

HSK Annual report 1998 • Beznau Nuclear Power Plant 15 1.3 Radiation Protection Dose-relevant tasks and measured Person- collective dose mSv 1.3.1 Protection of personnel Opening/closing the RPV head and fuel 48 For the calendar year 1998 (1997 values in movements brackets) the following values of collective Periodic inspections (in particular RPV 44 doses were determined for KKB. closure head and steam generators)

KKB1 Maintenance on steam generators 61 Preparations for the steam generator Activities Person-Sv 11 replacement Planned outage 0.00 (0.54) Operation 0.07 (0.07) Annual collective dose 0.07 (0.61) The highest person dose due to external radiation amounted in 1998 to 10.6 mSv (1997: 10.8 mSv). Details are given inTablesA5 to A10and KKB 2 Figures A5 to A9. Activities Person-Sv There was no spread of contamination or Planned outage 0.41 (0.00) contamination of persons which could not be Operation 0.07 (0.08) removed immediately using normal methods, e.g. showering. The screening measurement Annual collective dose 0.48 (0.08) through "quick counters" resulted in no findings which would have required further incor- KKB 1 and 2 poration analyses. Activities Person-Sv Total There were no radiological incidents, classi- fiable under Guideline R-15, during 1998 in ei- Planned outage 0.41 (0.54) ther of the units. Operation 0.14 (0.15) Annual collective dose 0.55 (0.69) 1.3.2 Release to the environment and direct radiation In Unit 1, where an operational cycle of 18 The limiting values for the release of radioac- months was used for the second time, no tive materials from KKB, the yearly release in maintenance shutdown occurred in 1998. On 1998, and the doses calculated according to the basis of measurements carried out before the Inspectorate's guideline R-41 for individual temporary installation of lead shielding, the persons in the vicinity are all listed inTable A4a. radiological conditions in Unit 2 continue to The radioactive releases via the exhaust gas show the downward trend to lower dose rates system in the form of aerosols, iodine and observed in the last few years. No damage to noble gases were well below the limits set. fuel assemblies occurred during the last cycle This also applied to the waste-water releases and this resulted in low dose rates with maxi- apart from tritium, where the tritium release, mum values of 0.03 mSv/h over the flooded typical of pressurised water reactors, reactor pool. amounted to approximately 15% of the limit- During outage work, about 65 tonnes of ing value. Table A4b shows the releases of temporary lead shielding was again installed. noble gases and iodine via the exhaust gas This allowed savings of about 0.24 Person-Sv. system and for tritium and remaining radioac- In addition, new shielding of the RPV head, as tive substances via the waste water during the already used successfully for periodic inspec- last five years. Release values less than 0.1 % tions in Unit 1, was carried out this year. This of the release limits are not shown. shielding will be used in future during all work The calculated yearly worst dose for indi- on the reactor head, including opening and vidual members of the population in the vicin- shutting of the reactor pressure vessel. The ity of KKB is approximately 0.001 mSv for work was planned in detail, with the usual adults and 0.002 mSv for infants. These values dose optimisation for all dose-relevant jobs. lie well below the guideline dose of 0.2 mSv per Daily checks continued to be applied in a thor- year according to the Inspectorate's guideline ough way on the dose, including comparison R-11. Articles 5 and 6 of the Radiation Protec- of actual to planned values, with continual deri- tion Ordinance state that activities which result vation of corrected measures for work proce- in an effective dose of less than 0.01 mSv per dures. Taking into account the dose-relevant year for the persons concerned are deemed work described below, the collective dose dur- justified and optimised. This means that no ing the maintenance shutdown of 0.41 Person- further efforts are necessary to reduce radio- Sv can be regarded as especially low. active release and the resulting doses for the population.

16 HSK Annual report 199 Beznau Nuclear Power Piam The quarterly measurements carried out by and the planned computerised emergency pro- the Inspectorate as a check, and the half yearly cedures COMPRO.The KKB compact simula- comparison measurements of the Section for tor was used intensively and a new pro- Radiation Monitoring, Freiburg (SUeR) on aero- gramme for training of reactor operators by sol and iodine filters, as well as on exhaust gas their shift supervisors was started in the year and waste-water samples, showed good under review. agreement between the results and the KKB Employees of all departments refreshed values. their technical knowledge, trained their practi- The dose rate monitoring network (MADUK) cal skills and underwent personal development in the vicinity, and the quarterly measurements in a variety of further courses. Of particular at the perimeter of KKB, detected no signifi- note here is the schooling of instructors from cant increase above the level of the back- the training department in methodology and ground radiation. Thus the limiting emission didactics carried out at the simulator training values for direct radiation outside the plant site organisation in Essen, Germany. (1 mSv per year for living, recreation and work rooms, and 5mSv per year in other areas), 1.4.2 Organisation and operational given in Article 102, Clause 3 of the Radiation management Protection Ordinance, were again adhered to At the end of 1998, a new group "Central Plan- during the year under review. ning" was established in KKB within the operational department in order to administer and 1.3.3 Radiation protection instrumentation supervise the way in which maintenance and All measuring instruments to monitor the ac- shutdown work are carried out. With the em- tivity and radiation level in the plant, as well as ployment of 11 new colleagues, who are in- radiation releases to the environment, person- tended to become operators in the future, the nel monitors and personnel dosimetry sys- members of the operational department have tems, worked satisfactorily in the year under received strong reinforcement. The workforce review. KKB participated successfully in the at the plant was 459 at the end of the year annual comparison measurements for person- (1997:461). nel dosimetry departments organised by the In February, a team from the IAEA estab- Federal Commission for Radiation Protection lished, in the context of the OSART follow-up (EKS) and was able to provide proof of the re- inspection, that the suggestions and recom- quired measurement accuracy. mendations from the OSART mission in De- cember 1995 have been carried out to a large extent. 1.4 Personnel and organisation Together with KKL, KKB has developed and introduced a programme (SAFE) to encourage 1.4.1 Personnel and training safety consciousness in the workforce. Fur- During the year under review, one shift tech- thermore, KKB and KKL have established a nical advisor (STA), one shift supervisor and working group to investigate possible one reactor operator passed stage A, and eight synergistic effects in certain areas and to de- reactor operators passed stage B of their li- termine the possibilities for closer co-opera- cence examinations. Three technical school tion. Examples of this are co-operation in the (HTL) engineers also completed the reactor field of maintenance and common use of the engineering course of the PS I reactor school active laundry facilities.The Inspectorate wel- and were awarded diplomas accordingly. comes this co-operation, since it supports the Six of the licensed, stage B reactor opera- exchange of information. tors are technical school (HTL) engineers, KKB has also started a programme to support whose training to become shift technical advi- notification of "near events". In the year under sors was continued according to plan in 1998. review, several near events were analysed as to The large number of new licences, as well as their causes. In this way, weak-points can be the intensive training and further education of discovered at an early stage and eliminated. The plant operators, is of great importance due to Inspectorate regards this activity as providing an the expected level of retirement. Table A2 lists important contribution to safety. the present numbers of licensed personnel. The licensed shift personnel intensified their knowledge of reactor physics in refresher 1.5 Emergency preparedness courses lasting four days at the PSl reactor school. Once again, simulator training for li- In November, KKB carried out the emergency censed personnel in Pittsburgh, USA in 1998 works exercise "VAPORETTO" under observa- concentrated upon the alarm system AWARE tion of the Inspectorate.

HSK Annual report 1998 • Beznau Nuclear Power Plant 17 The main goals of the exercise were training of teamwork, testing of a STA engineer candi- date in the areas of accident analysis, emergency management and transfer of this to the emergency team, management and co-operation with the exercise shift on the compact simulator, as well as the training of various emergency groups both with the regard to technical issues and in co-operation with other groups. The assessments of the situation were carried out correctly and in a timely manner, both by the shift technical advisor and the team. Instructions for the necessary measures were given. Possibilities for optimisation became apparent in the communication between the emergency team and the action group, as well as in the overall co-ordination of the action groups. In the opinion of the Inspectorate, the goals of the exercise were reached. Container for the transport of depleted fuel elements. The Inspectorate confirmed the prepared- The container is carefully lowered onto the railway ness for action of the emergency communica- wagon and brought to the horizontal position. Source Beznau NPP tion systems to the Inspectorate and to other external bodies in the course of an appropriate inspection. Construction of the building for high-level waste at the ZWIBEZ interim storage site, which was approved in 1991 by the Federal 1.6 Radioactive waste Council and licensed in 1996 by the Inspector- ate is almost complete. This is a storage facil- During the year under review, the quantity of ity for depleted fuel assemblies and for high- raw, radioactive waste was as expected from level waste from reprocessing, as well as for the experience of previous years (see Table the temporary storage of steam generators. A11). Sludge from the waste-water treatment plant, as well as filter cartridges, were routinely cemented. In preparation for the 1999 cam- 1.7 Overall judgement by the paign, used resins were solidified with polystyrol and filled into 100 litre packages Inspectorate which were stored in a suitable room. Mixed The Beznau plant condition and the operational wastes were brought to PSI for processing. At management can be rated as good with regard PSI, combustible wastes were incinerated and to nuclear safety and radiation protection. The the incineration residues, together with small notifiable incidents which occurred were of amounts of non-combustible wastes, ce- minor relevance to nuclear safety. Their causes mented. The resulting packages of conditioned lay predominantly in the area of human behav- wastes were returned to KKB. iour and organisational management. Thus, KKB is in possession of updated releases further efforts are needed in order to recognise according to the Inspectorate's Guideline R-14 problems in these areas in good time and to for all types of waste packages currently pro- close any gaps here. duced.The required, amended documentation The use of extensive shielding, together for waste packages, which are no longer pro- with the way in which the work was planned, duced, will be prepared according to an agreed were the main reasons that the collective dose schedule. The data needed for this are stored for internal and external personnel again in such a way that no loss of information will reached only a very low value. The amount of occur later when the amended documentation radioactive material released to the environ- is produced. ment lay well below the limits set by the au- Pending processing at a later date, various thorities. Thus, the radioactive doses for the raw wastes were stored under appropriate population were insignificant. conditions in designated areas in the controlled zone. Conditioned waste packages were routinely brought to and kept in the temporary storage building and the low-level, waste-storage hall (SAA hall) of the ZWIBEZ.

18 HSK Annual reoort 1998 • Beznau Nuclear Power Plant 2. Miihleberg Nuclear Power Plant

Aerial view of the nuclear power plant Muhleberg

2.1 Operational data and 2.2 Plant safety

results 2.2.1 Particular events The Muhleberg Nuclear Power Plant (KKM), According to the Inspectorate's Guideline R-15 belonging to BKW FMB Energy AG, started dealing with "Reporting on the operation of commercial operation in 1972 and is a boiling nuclear power plants", one notifiable event was water reactor with a net electrical output of assigned to class B. On the international nu- 355 MW. Additional data are summarised in clear event scale, INES (see Section 12.7 and Tables A1 and B3 of the Appendix; Figure B2 Appendix Figure A3 and Table B2), it was as- gives a functional diagram of a boiling water signed to level 1 because of its safety rel- reactor plant. evance. In 1998, the Muhleberg power plant reached The event occurred on June 23,1998 during a load factor of 85.3 % and an availability fac- the quarterly testing of the local dose rate tor of 90 %. The revision work with refuelling measurement system at the main-steam lines, lasted 35 days and was of significant impor- which is prescribed by the technical specifica- tance for the non-availability of the plant. One tions. This involves automatic closure of the turbine unit was shutdown already 21 days drain valves in the main-steam lines. During before the maintenance outage in order to re- manual opening of the valves following the place the condenser tubing on this unit in the test, the operator opened, by mistake, a main- course of improvements to the plant. steam blowdown valve instead of a drain valve. The "Steinriesel" residential district re- The operator attempted immediately to shut ceived 1.4 GWh of thermal energy for domes- the valve, which had been opened erroneously, tic heating. As well as planned reductions in by closing the pilot valve, since the blowdown order to carry out periodic inspections, an un- valve can only be controlled via the pilot valve. planned reactor scram from 100 % power oc- The blowdown valve, however, remained open, curred. In addition, a disturbance in the turbine since the main-steam pressure, which acts test equipment, during a monthly test, led to against closing of the valve, was not reduced a brief, unplanned power reduction. quickly enough. Steam flowed through the open blowdown valve and condensed in the torus, which led to warming-up of the water in the torus and, finally, after about 14 minutes, to an automatic reactor scram via the signal "torus temperature high".The drop in pressure

HSK Annual report 1998 • Muhleberg Nuclear Power Plant 19 associated with the scram closed the procedure which allows ultrasonic and eddy blowdown valve. current inspection from the inside of the core The procedure corresponding to the distur- shroud was used for the first time. This results bance was not followed in a timely manner by in a definite improvement, in comparison with the shift team. As a consequence, an auto- previous years, since those circumferential matic reactor scram occurred. According to the welds most affected by cracking can now be procedure, the pressure should first have been 100 % inspected, in part using diverse meth- lowered and, if the valve had remained open ods (visual, ultrasonic, eddy current). Further- after five minutes, the reactor scram should more, the longitudinal welds in the central part have been initiated manually. The causes for of the core shroud can now be inspected with the disturbance and for the less-than-optimum ultrasonic and eddy-current methods. way in which this was dealt with are to be Using the new technology, the known found in both inadequately marked require- cracked areas of both of the above-mentioned ments in the procedure and ergonomic factors. circumferential welds were subjected to repeat Furthermore, inadequate training of personnel inspection, together with the longitudinal welds and the alarm concept in the control room con- in the central part, which, to date, had only been tributed to this event. The fact that the shift visually inspected (video). team did not deal with the situation according All known cracks were confirmed in the in- to procedures was also the reason that this spected circumferential welds. In comparison event was assigned to INES level 1 on the in- with 1997, the increase in crack length in the ternational nuclear event scale, even though central weld amounted to 145 mm. With the the risk to safety was low as a result of the other circumferential weld, an increase of ap- automatic reactor scram. proximately 80 mm was registered in compari- Immediate countermeasures to prevent rep- son with the result obtained in 1996. The in- etition of such a disturbance, as proposed by crease in length in both welds is within the KKM and required by the Inspectorate, were range expected on the basis of the experience put into practice by KKM. Inspection of the of previous years. The crack depths in the cir- blowdown line showed no damage as a result cumferential welds continue to lie in the typical of the event (see also Chapter 11). range of between 10 and 20 mm and thus do not penetrate the wall thickness. The inspected lon- 2.2.2 Work during the refuelling outage gitudinal welds revealed no signs of damage. The planned tasks undertaken during the revi- As in earlier revision shutdowns, visual in- sion, such as refuelling, testing, periodic inspections using a special underwater video spections, functional tests on components and camera were again carried out in the year un- systems, maintenance work, etc. were carried der review within the reactor pressure vessel out. The special activities and results were as and on the reactor internals. No cracks or other follows: indications were found, which could have an The core shroud was inspected visually for influence on operational safety of the plant. cracks using an underwaterTV camera. This Furthermore, no discrepancies which might resulted in no new findings. In the course of affect safety were found during the remaining ultrasonic testing of core shroud welds, a test periodic material inspections of the reactor pressure vessel, the reactor pressure vessel head and bolts, the welds of the recirculation loop and main-steam piping, the core spray lines and the supports of the reactor pressure vessel. With regard to the electrical equipment, periodic examinations were carried out on the instrumentation and control of the emergency cooling system and the reactor protection system, and discharge tests were performed on all batteries in the operating and emergency buildings. No safety-relevant defects were found in these inspections.

2.2.3 Plant modifications The main changes to the plant were:

New fuel elements are stored in a dry storage facility Battery replacement until they are required. When new fuel elements are delivered, they are subjected to optical and mechanical Since routine measurements on individual cells quality Controls. Source: 8KVV FMB Energy AG, Bern of the 125 V battery in train 1 of the DC current

20 HSK Annual report 1998 • Muhleberg Nuclear Power Plant pump impellers, coolers, pump heads and seal- ing water heaters were used. Visual inspections of the inside of the pump casings using an underwater camera gave no indications. The casing bolts were not replaced. In 1999, these must be subjected to a comprehensive ultrasonic inspection.

Replacement of torus penetrations and submerged pipes of the high-pressure injection systems (RCIC) A and B Corrosion damage had occurred to the torus penetrations and the submerged pipes of the RCIC systems A and B, which, to date, had been made of ferritic material. These components were therefore replaced using ones made of austenitic material. Non-destructive inspection of the new welds and pressure testing were carried out without indications.

Replacement of the six blowdown lines in the torus The ferritic parts of the blowdown lines in the torus, which had shown signs of corrosion, were replaced by new piping using the same material. Base-line inspection of the new The reactor pressure vessel head is lifted slowly after welds gave no indications. all the 60 nuts have been removed. Access to the fuel elements and core internals in the reactor pressure vessel is now possible. Source: BKW FMB Energy AG, Bern Partial replacement of the suction lines of the circumferential torus piping supply, carried out during the previous opera- The piping sections, including the torus gate tional period, had shown discrepancies, KKM valves, were replaced up to the suction nozzles replaced this battery during the shutdown pe- of the pumps. Non-destructive examination of riod after approximately 80 % of its expected the new welds and pressure testing were car- life with a battery of the same type. ried out without indications.

Reactor manual control and rod position Tubing replacement in the main con- indicator denser of turbine unit A The newly installed systems RMCS (Reactor The main condenser of turbine unit A was sub- Manual Control System) and RPIS (Rod Posi- jected to replacement of most tubing using ti- tion Information System), which are based on tanium tubes. The stainless steel tubes at the modern, computerised control technology, edge of the condenser were also replaced. The were installed and put into operation. Replace- tubeplates and the whole support structure ment of the older systems also involved instal- were renewed. The old brass tubing had led to lation of new switches and indicators in the a high copper content in the feedwater. This control room and the associated cabling. reduces the effectiveness of the planned hy- Both systems were extensively tested and, drogen injection, which, together with deposi- after minor modifications, now fulfil the neces- tion of noble metals, is intended to prevent sary functions. The final test required by the stress corrosion cracking of reactor internals. Inspectorate, namely prevention of rod removal because of too high a local neutron flux 2.2.4 Fuel elements and control rods density, was successfully carried out at 32 % It can be concluded from the low concentra- power during start-up of the plant. tion of activity in the reactor water and exhaust gas from the turbine condensers throughout Modification of the reactor recirculation the year that no fuel element cladding defects pumps A and B occurred. Of a total of 240 fuel assemblies in Both pumps were thoroughly overhauled in the core, 40 were replaced for the 26th fuel order to prevent crack formation in the shafts cycle (1998/99). 32 of these new fuel assem- and pump heads as a result of thermal fatigue. blies have a 9x9 fuel element configuration and Components of improved design, such as 8 are prototype fuel assemblies with a 10x10

HSK Annual report 1998 • Muhleberg Nuclear Power Plant 21 element configuration. During the 1998 main- The ageing surveillance of buildings within the tenance shutdown, 6 exhausted control rods earthquake classification 1 (EK1) is being car- were replaced with new ones. ried out according to a guideline approved by 18 fuel elements, which had been in serv- the Inspectorate. ice for different lengths of time, were in- To date, the ASP documentation examined spected with an underwater camera during the by the Inspectorate has not revealed any revision outage in order to check the opera- safety-relevant gaps in the maintenance pro- tional behaviour of the fuel assemblies with a grammes. Furthermore, the present results view to possibly raising the burn-up. All the fuel indicate that no unacceptable reduction in assemblies inspected were in good condition. safety-related properties is to be expected in the near future. 2.2.5 Probabilistic safety analysis (PSA) and accident management (AM) 2.2.7 TUV expertise on the core shroud At the beginning of 1998, KKM submitted a Particular attention is being paid to monitoring revised version of its PSA for the plant condi- cracks in the core shroud of the Muhleberg tions low-load and shutdown. The revised nuclear power plant. The core shroud is a cy- study is still being evaluated by the Inspector- lindrical component made of austenitic steel ate. With regard to bringing the full-load PSA which is inserted into the reactor pressure (project MUSA 2000) up to date, KKM has re- vessel and separates the zone containing the quested from the Inspectorate a more precise fuel assemblies from the zone of the jet description of the way in which external initia- pumps. It is exposed on both sides to reactor tion events are to be treated. In this connec- water and is not a pressure boundary. tion, the Inspectorate carried out a plant in- The Federal Department of the Environ- spection in KKM, with the main focus being on ment, Energy and Communication (UVEK) or- earthquake stability and safety, and produced dered aTUV expertise on the safety relevance a corresponding technical report. It became of the cracks in the core shroud of the apparent that the earthquake risk analysis from Muhleberg nuclear power plant in autumn 1989 must be revised by KKM according to the 1997 as an independent, second opinion. The state of the art. TUV report, dated February 1998, confirms in In the context of systematic introduction of full the evaluations carried out by the Inspec- "Severe Accident Management Guidance", torate. Fracture mechanics analyses show that KKM answered the Inspectorate's questions, the cracks present today do not result in any which had arisen from an audit, with regard to reduction in safety either for normal operation present status and future projects. of the plant, or for the hypothetical case of the occurrence of a safety-related earthquake to- 2.2.6 Ageing surveillance programme gether with a pipeline failure. The essential KKM continued with its ageing surveillance Internal area programme (ASP) in the area of mechanical (fuel elements. engineering components by submitting docu- coolant flow) mentation on the core internals. This will be examined by the Inspectorate together with Tensile anchors the documentation for the reactor pressure vessel, the containment and the recirculation Weld seams lines.The documentation concerning the main number 4 and 5 steam, feedwater and core spray systems has not yet been submitted. In the electrical engineering area, a number of revised documents on class 1 E components (concerning, among others, temperature sensors, limit switches and electrical penetrations) were submitted together with several new documents (for cabling, transducers, electronic components, etc.). The ASP for the electrical components is Weldseams being carried out according to a guideline ap- number 2 and 3 Reactor pressure proved by the Inspectorate. vessel (section) In the area of structural engineering, the ASP documentation for the reactor building was examined by the Inspectorate. During the year under review, the corresponding base-line Simplified computer-generated picture of the core- inspections were carried out and documented. shroud showing the attached tensile anchors.

22 HSK Annual report 1998 • Muhleberg Nuclear Power Plant protection goals of safe shutdown and ability recirculation lines in comparison with the pre- to cool the core are also maintainable during vious year. The measures taken to reduce en- the next fuel cycles. The tie rods, which were try of cobalt into the system, in particular re- added in 1996, are able to guarantee the integ- placement of the pins and rollers of all control rity of the core shroud even in the case of rods with sliding pieces low in cobalt, continue cracking through the full wall thickness at the to show a favourable effect on the radiation circumference. The additional inspections of level in the drywell even four years after they the core shroud stabilisation required by the were completed. TUV were carried out in the presence of the Numerous radiation sources were temporar- regulatory authority and were successful. ily shielded with a total of about 70 tonnes of lead sheeting and lead tiles during the outage in order to reduce the dose rate in all working 2.3 Radiation protection areas, but chiefly in the dryweil. This led to a net reduction in dose, as estimated by the 2.3.1 Protection of personnel operator, of around 0.75 Person-Sv. Since the For the calendar year 1998 (1997 values in activity in the primary coolant was low due to brackets) the following values of collective the intact fuel assemblies over many cycles, dose were determined for KKM: contamination in the turbine building was, as in previous years, low and this facilitated the Activities ; Person-Sv work done there. Planned outage 0.83 (1.18) There were no individual doses which ex- Operation 0.46 (0.40) ceeded the limit. The highest individual dose Annual collective dose 1.29 (1.58) from external radiation in 1998 was 14.6 mSv. The comparable value for 1997 was 14.2 mSv. The collective dose received during the revi- Further details can be found inTables A5 to A10 sion outage was kept to a very low value, tak- and Figures A5 to A9.The incorporation screening into account several operations relevant to ing measurements of internal and external the dose.This was achieved by efficient radia- staff using the "quick counter" before and af- tion protection, the use of extensive shielding, ter spending time in KKM gave no findings. and making a daily comparison between target There was no spread of contamination or con- and actual doses in all fields of work, in order tamination of persons which could not be re- to permit any necessary corrections to work moved using normal cleaning. No notifiable procedures. The dose was well below the fore- radiological events occurred according to cast dose of 1.3 Person-Sv for the outage. The Guideline R-15 during 1998. total annual collective dose is also low and lies well below the Inspectorate's Guideline of 4 2.3.2 Releases to the environment and Person-Sv. direct radiation A collective dose of more than 0.05 Person- Table A4a shows the prescribed limits for the Sv was predicted for the following areas of release of radioactive materials from KKM, the work and a corresponding radiation protection annual releases for 1998 and the doses calcu- plan was produced according to the Inspector- lated for individuals in the vicinity on the basis ate's Guideline R-15. of the Inspectorate's Guideline R-41.The radioactive releases via the exhaust gas system in Dose-relevant tasks and measured Person- collective dose mSv the form of aerosols, iodine and noble gases were well below the limits set. This also applied Maintenance of condensor A 96 to the waste-water releases for tritium and for Revision of the reactor recirculating 86 other radioactive substances.Table A4b shows pumps the release of noble gases and iodine via the The effective collective dose for backfitting the exhaust system and, for tritium and remaining condenser was well below the planned value, radioactive materials, via the waste-water sys- since the time in which the personnel would tem during the last five years. No further de- have to stay in the (low) radiation field at the tails are given for releases of less than 0.1 % condenser was overestimated. In order to over- of the release limits. haul the reactor recirculation pumps, these The calculated yearly worst dose for indi- were first decontaminated chemically together vidual members of the population in the vicin- with the reactor water clean-up system. In this ity of KKM is approximately 0.008 mSv for way, the local dose rate in the areas where the adults and 0.007 mSv for infants, even taking work was carried out was able to be signifi- into account deposition from previous years. cantly reduced. Once again, reduced dose These values lie well below the guideline dose rates (by about 7 %) were measured at the of 0.2 mSv per year according to the Inspec-

HSK Annual report 1998 • Miihleberg Nuclear Power Plant 23 torate's Guideline R-11.The proportion of the KKM successfully completed the course for calculated doses from the release in 1998 radiation protection technicians (earlier desig- amounts to 0.001 mSv for adults and infants. nation: chief radiation protection inspector) at Articles 5 and 6 of the Radiation Protection the PSI radiation protection school. The large Ordinance state that activities involving an ef- number of new licences is of great importance fective dose of less than 0.01 mSv per year for due to the expected level of retirement. The the persons concerned are deemed justified number of licensed personnel is given inTable and optimised. This means that no further ef- A2. forts are necessary to reduce radioactive re- All shift groups completed two training ses- leases and the resulting doses for the popula- sions, each lasting four days, on the KKM simu- tion. lator. The shift technical advisors were involved The quarterly checks carried out by the In- in this simulator training. The lessons learned spectorate, and the half-yearly comparison from the incident which occurred on June 23, measurements of the Section for Radiation 1998 (see Section 2.2.1) were taken into ac- Monitoring, Freiburg (SUeR) on aerosol and count during training and for improvements to iodine filters, as well as on exhaust gas and the simulator. waste-water samples, showed good agree- Employees of all departments refreshed ment between the results and the KKM val- their technical knowledge, trained their practi- ues. cal skills, and underwent personal develop- The dose rate monitoring network (MADUK) ment in a variety of further courses. Training in detected no significant increase above the the area of quality management is of special level of background radiation in the vicinity of mention here. KKM. In close proximity to the nuclear power plant, the ambient dose rate is higher due to 2.4.2 Organisation and operational direct and indirect radiation from the turbine management building and the waste storage facility. The There were no changes in the organisation at measured values at the perimeter fence were KKM during the year under review. The plant at normal levels as in previous years. The lim- personnel amounted to 291 people at the end iting emission values for direct radiation out- of 1998(1997: 292). side the plant site (1 mSv per year for living, The KKM quality management system was recreation and work rooms, and 5 mSv per completed in the year under review and is now year in other areas), given in Article 102, Clause in use. It is based to a large extent on the ISO- 3, of the Radiation Protection Ordinance, were 9000 Standard, but also takes into account the again adhered to during the year under review. requirements of the IAEA document "Quality Assurance in Nuclear Power Plants and other 2.3.3 Radiation protection instrumentation Nuclear Installations" (Safety Series 50-C/SG- All measuring instruments to monitor the ac- Q, 1996). Presentation according to the proc- tivity and radiation level in the plant, as well as esses involved makes it easier both for plant radiation releases to the environment, person- employees and for external personnel to ob- nel monitors and personnel dosimetry sys- tain a good insight into the activities at KKM. tems, worked satisfactorily in the year under During the year under review, KKM partici- review. KKM participated successfully in the pated actively in the research project "Deter- annual comparison measurements for person- mination of Safety Awareness" of the Psycho- nel dosimetry departments organised by the logical Institute at the University of Berne. Federal Committee for Radiation Protection Members of staff were interviewed in the (EKS) and was able to provide proof of the re- course of a pilot experiment.The results of the quired measurement accuracy. study are expected to become available at the beginning of 1999 and should allow the plant to improve assessment of the safety aware- 2.4 Personnel and organisation ness area.

2.4.1 Personnel and training Two shift supervisors, six reactor operators at 2.5 Emergency preparedness level A and four reactor operators at level B were licensed after passing the appropriate In May, an emergency plant exercise "COLA" examinations. Two of the newly licensed reac- was carried out in KKM under the observation tor operators are technical school (HTL) engi- of the Inspectorate. This concentrated on the neers and one is a physicist. Their training to three areas "intervention from outside" become shift technical advisors was continued (EW3), fire and communication. according to plan in 1998. One participant from

24 HSK Annual report 1998 • MQhleberg Nuclear Power Plant The aims of the exercise were the use of be- ages. Mixed wastes were transferred to PSI, havioural measures and the appropriate reac- where the combustible wastes were inciner- tion to the situations arising during negotia- ated and the incineration residue cemented. tions with a blackmailer, fire-fighting in the The resulting packages of conditioned waste controlled area, the introduction of safety were returned to KKM. measures decided upon by the emergency In February, the Inspectorate approved re- management in connection with operation of lease of the waste package type "Steam Sepa- the plant, and the passing on of information rator Bolts". With the exception of two types of (both internally and externally) in a timely man- waste package, KKM has now obtained up- ner, with support from external press offices. dated release approvals according to the In- The training scenario was dealt with in a spectorate's Guideline R-14 for all types of satisfactory manner by the emergency man- waste package which are currently produced. ager and by members of the emergency team. In 1999, KKM will prepare specifications for the The newly established, trial team organisation two waste package types not yet licensed by provided a good framework for efficient team- the Inspectorate. The amended documenta- work. Co-operation, behaviour, and the issuing tion for waste packages which are no longer of orders to others involved, were generally produced will also be prepared in 1999. good. Different raw wastes, awaiting later treat- Those involved in the COLA exercise worked ment, are stored appropriately in an uncondi- well. Further possibilities for optimisation were tioned form in premises in the controlled zone. discussed in the areas of communication be- This applies in particular to resins (2480 drums) tween individual, internal departments, in the and residues (59 drums), which are in interim availability of current documentation (e.g. mis- storage and are intended to be conditioned in sion documents for the fire brigade), as well as the CVRS for final storage. All conditioned in certain details related to the requirements of waste packages are routinely brought to and radiation protection during fire brigade missions held in the interim storage building. in the controlled zone. Furthermore, it was suggested that the tested team organisation be finally introduced before the emergency exercise 2.7 Overall judgement by the in 1999. In the opinion of the Inspectorate, the aims of the exercise were achieved. Inspectorate The Inspectorate confirmed the prepared- The condition of the Muhleberg plant and the ness for action of the emergency communica- operational management can be rated as good tion systems to the Inspectorate and to other with regard to nuclear safety and radiation pro- external bodies in the course of an appropriate tection. The reduction in nuclear safety mar- inspection. gins associated with the incident classified according to INES 1 was minor. Corresponding measures for improvement have been carried 2.6 Radioactive waste out. Checks on the core shroud using extended During the year under review, the quantity of inspection methods, together with theTUV raw radioactive waste (seeTable AH) was as expertise, have shown that the cracks continue expected from the experience of previous to cause no reduction in safety. years.The new amounts of ion-exchanger res- In the area of radiation protection, the meas- ins arising from operation were conditioned ures taken to reduce doses showed further routinely to the final storage state in the Ce- success. The collective dose (internal and ex- ment Volume Reduction and Solidification plant ternal personnel) again reached only a low (CVRS). In addition, 197 drums with old resins value for a boiling water reactor of this type. from the intermediate storage facility were The amount of radioactive material released to cemented into 216 packages using the CVRS the environment lay well below the limits set plant. Fuel-assembly casings and other reactor by the authorities.The radioactive doses for the internals were also conditioned into 52 pack- population are thus insignificant.

HSK Annual report 1998 • Muhleberg Nuclear Power Plant 25 3. Gosgen Nuclear Power Plant

Work on the supply valve to the fuel element cooling pool.

3.1 Operational data and automatically and functioned correctly according to design and expectations. After two results hours, the plant was able to return to full The Gosgen nuclear power plant (KKG) is a 3- power. No unplanned reactor scram took place loop pressurised water reactor with a net elec- during the year under review. trical output of 970 MW. It went into operation in 1979. Additional technical data are summarised inTables A1 and B3 of the Appendix; Fig- 3.2 Plant safety ure B1 shows the functional diagram of a pressurised water reactor plant. 3.2.1 Particular events In 1998, KKG achieved a load factor of Based on the Inspectorate's Guideline R-15, 92.8 % and an availability factor of 93.4 %.The "Reporting on the operation of nuclear power planned annual outage lasted 24 days and was plants", no event had to be notified. the main cause of non-availability of the plant. During the year under review, the plant deliv- 3.2.2 Work during the refuelling outage ered 155 GWh process heat to the local card- All the planned activities such as refuelling, board factory. testing, periodic inspection of mechanical and Plant operation was interrupted by an un- electrical components, functionality tests of planned power reduction. During work in the components and systems, maintenance, etc., ATEL switching plant, the unit switch opened were carried out. erroneously. Through this, the transfer of en- Some of the more important activities were ergy to the electricity network was interrupted as follows: and KKG switched into isolated operation. All - Periodic pressure testing of the reactor cool- measures foreseen for this case were initiated ant system, which has to be carried out

HSK Annual report 1998 • Gosgen Nuclear Power Plant 27 every ten years, took place during the year under review. Upon reaching the test pressure, a leakage was detected in the area of a measurement transducer. After dealing with this, the pressure test was successfully completed. Following pressure testing, ultrasonic inspection was performed on two circumferential welds, selected regions of the base material and the cladding, and parts of the supports of the reactor pressure vessel (RPV).The test results corresponded within the measurement tolerance, to previous data. From the results of pressure testing and ultrasonic inspection, the reactor pressure vessel is in very good condition. In 1995, an indication was found in a weld of the primary circuit, whereby the possibility of it being caused by a crack could not be eliminated. In 1997 the region of the indica- Preparing a mechanical test device for the weld seams tion was instrumented with potential on the reactor pressure vessel. source: Gosgen NPP probes. This measuring technique is based on the change in electrical voltage in an area - No particular findings arose from tests of carrying current as a result of crack forma- the instrumentation and control system or tion or crack growth. No crack growth was of the reactor protection system. apparent either during operation or during The findings of the other inspections, exami- the previously mentioned pressure test of nations and tests gave no cause for concern. the reactor cooling system. The fracture mechanics evaluation of the indication, car- 3.2.3 Plant modifications ried out earlier using conservative assump- During the year under review, the main tions, shows that a possible crack which changes were as follows: might be present as a cause of the indica- - The last five of the total of 31 drives, tion would have no safety relevant influence planned for exchange, were replaced in or- during the 1998/99 operational cycle. der to guarantee long-term reliability of For the first time, all main coolant lines run- motor-driven valves within the containment. ning from the reactor pressure vessel to the With this, the improvement programme has steam generators and to the main coolant been completed. pumps were subjected to an internal, visual - Brittleness of the insulation of the coil-con- inspection using a remote-controlled, under- necting cables was found during inspection water video camera. No safety-relevant in- of control rod drives. As a result of these dications were found. findings, it was decided to replace the old Several weld seams of the pressuriser were cables using ones with a higher temperature subjected to volumetric ultrasonic inspec- stability. This work was carried out on the tion and examination for surface cracks us- last 15 of a total of 48 drives. ing magnetic powder testing. All were found - Two pool connections, the containment to be in order. penetrations and part of the mechanical and In 1994, all three shafts of the main reactor electrical assembly work were carried out in coolant pumps were replaced by ones of im- connection with backfitting of the third, in- proved design which permit testing for crack dependent, pool-cooling circuit. The system formation without dismantling the pumps. will be completed during 1999 and commis- During the year under review, the third sioned during the shutdown. pump shaft was also re-examined ultrasonically, via the central borehole, for the first 3.2.4 Fuel elements and control rods time.There were no indications. For the 20th operating cycle (1998/99), 44 of Major overhauls of the motors of one main the total of 177 fuel assemblies were replaced reactor-coolant pump, one main condensate during the revision outage by new ones. pump, one main feedwater pump and one Among the latter were 20 uranium/plutonium, high-pressure supply pump of the volume mixed oxide fuel assemblies (MOX); with this, control system were carried out without sig- 28 MOX fuel assemblies are present in the nificant findings. core.The fuel elements of the new fuel assem-

28 HSK Annual report 1998 • Gosgen Nuclear Power Plant blies have a cladding whose surface has been the framework of systematic introduction of provided with a protective layer to retard cor- Severe Accident Management Guidance. rosion. In the 19th operating cycle (1997/98), the 3.2.6 Ageing surveillance programme presence of cladding damage to a fuel rod was During the year under review, KKG submitted suspected because of increased activity in the the documentation for the pressuriser as part reactor coolant. During the maintenance shut- of the mechanical engineering section of the down, this finding was confirmed in the course ageing surveillance programme (ASP), which of fuel assembly inspections on a corner rod the Inspectorate has required to be submitted. of a fuel assembly from the 16th core loading. The Inspectorate has examined and evaluated The damage was caused by fretting wear as a the four documents presently available on age- result of fracture of a spring in the lowest sepa- ing surveillance of the main coolant lines, main rator. The spring fracture resulted from earlier coolant pumps, core internals and the damage to the separator which had taken pressuriser. The documentation promised by place during loading of a neighbouring fuel KKG on the reactor pressure vessel and the assembly. steam generators has not yet been submitted. Test fuel rods with different cladding mate- Three ASP documents on valve drives, cables rials continue to be exposed in order to inves- and the hydrogen monitoring system with dif- tigate the behaviour of fuel rods at higher burn- fusion measurement cells were submitted by up. All fuel cladding has shown good KKG in the area of 1 E-classified electrical com- operational behaviour to date. ponents. The first two have already been as- During the revision outage, the cladding of sessed by the Inspectorate. all 48 control rods was again examined for In the area of structural engineering, the damage using diametrical measurement and Inspectorate also examined the ASP documen- eddy-current procedures. As a result of these tation for the reactor building. Base-line inspec- measurement results, four control rods were tions of buildings within the earthquake clas- replaced by partly-depleted control rods which sification 1 (EK1) are in progress according to were still suitable for use. the ASP guideline approved by the Inspector- During the year under review, 12 depleted ate. fuel assemblies were sent away for reprocess- The Inspectorate now expects rapid con- ing. tinuation of the ASP through the submission of further documents on safety-relevant electrical 3.2.5 Probabilistic safety analysis (PSA) & and mechanical engineering components, as accident management (AM) well as on auxiliary buildings of earthquake In 1998, the Inspectorate virtually completed class I. Schedules for the introduction and re- a detailed examination of the Gosgen PSA alisation of the programmes have still to be (GPSA) for full load.The essential results of the submitted to the Inspectorate. GPSA were confirmed by this examination.The To date, the ASP documentation examined frequency of core damage which could arise by the Inspectorate has not revealed any from internal incidents in the Gosgen plant is safety-relevant gaps in the maintenance pro- very low and belongs to the best results ob- grammes. Furthermore, the present results tained world-wide. indicate that no unacceptable reduction in As a result of checks carried out in 1997, the safety-related properties is to be expected in Inspectorate had required the earthquake the near future. analysis of the GPSA to be subjected to revision according to the state of the art. KKG has already submitted the first documentation for 3.3 Radiation protection this. In connection with this revision, KKG carried out, together with experts, a plant walk- 3.3.1 Protection of personnel down lasting several days in order to obtain For the calendar year 1998 (1997 values in data for the component-specific earthquake brackets), the following values of collective analysis. The Inspectorate has examined this dose were determined for KKG: work and the methodology used for it by Gosgen. A preliminary, qualitative evaluation of the Activities Person-Sv GPSA for low load and shutdown was carried Planned outage 0.61 (0.58) out during the periodic safety inspection. Operation 0.21 (0.16) In the course of an audit, KKG answered the Annual collective dose 0.82 (0.74) Inspectorate's questions with regard to the present situation and to future projects within

HSK Annual report 1998 • Gosgen Nuclear Power Plant 29 In addition to normal refuelling work (opening calculated on the basis of the Inspectorate's and shutting of the reactor pressure vessel, as Guideline R-41 for individuals in the vicinity of well as exchange of fuel assemblies), the pe- the plant. Radioactive releases via the exhaust riodic pressure test of the primary circuit made gas, in the form of aerosols, iodine and noble an important contribution to the collective gases, lay well below the limiting values. This dose. A detailed radiation protection plan was was also true for radioactive releases in waste prepared and periodic comparisons of planned water, excluding tritium. Releases of tritium, and actual values were carried out for this typical for a pressurised water reactor, were work. In the Inspectorate's opinion, this made about 20 % of the limiting values. Table A4b an essential contribution to the low collective shows the releases of noble gases and iodine doses for the work carried out. The annual col- via the exhaust gas system, and for tritium and lective dose is the fourth best, annual value, remaining radioactive substances via the including plant commissioning, and lies well waste water, during the last five years. Release below the Inspectorate's guideline value of values less than 0.1 % of the release limits are 4Person-Sv. not shown. The numerous measurements made in the The calculated yearly worst dose for indi- primary circuit showed that the doses at points vidual members of the population in the vicin- of importance for radiation protection had ei- ity of KKG is approximately 0.001 mSv for ther remained constant, compared with the adults and infants. This values lies well below previous year, or continue to increase slightly. the guideline dose of 0.2 mSv per year accord- Temporary lead shielding was again used lo- ing to the Inspectorate's Guideline R-11. Arti- cally. In 1998, a total of 7 tonnes of lead cles 5 and 6 of the Radiation Protection Ordi- sheeting was installed, in particular for protec- nance state that activities which result in an tion in working areas at the valves of the pri- effective dose of less than 0.01 mSv per year mary circuit. The effective saving in collective for the persons concerned are deemed justi- dose is estimated by the operator as about fied and optimised.This means that no further 63Person-Sv. efforts are necessary to reduce radioactive There was no significant spread of contami- releases and the resulting doses for the popu- nation in the plant. Release of radioactive ma- lation. terials into the building environment occurred The quarterly measurements carried out by briefly in connection with the periodic pressure the Inspectorate as a check, and the half-yearly test and reduction of the water level in the comparison measurements of the Section for reactor pool.This release was dealt with with- Radiation Monitoring, Freiburg (SUeR) on aero- out problems using the usual measures for the sol and iodine filters, as well as on exhaust gas controlled zone. A new design of plastic shield and waste-water samples, showed good proved effective in significantly reducing the agreement between the results and the KKG release of radioactive aerosols and noble values. gases into the containment environment upon The dose-rate measuring probes of the dose opening the reactor pressure vessel head. monitoring network (MADUK) in the vicinity of In one case, contamination of personnel the plant, and the quarterly measurements at could not be eliminated immediately using the the perimeter of KKG, showed no significant normal methods (washing and showering). increase above the level of the background One day later, this contamination was below radiation.Thus the limiting emission values for the guideline value according to the Radiation direct radiation outside the plant site (1 mSv Protection Ordinance. The resulting dose lay per year for living, recreation and work rooms, below 0.1 mSv. and 5 mSv per year in other areas), given in In no case did individual doses exceed the Article 102, Clause 3 of the Radiation Protec- limits. In 1998, the highest personal dose tion Ordinance, were again adhered to during through external radiation was 16.0 mSv. The the year under review. corresponding value for 1997 was 11.0 mSv. Further information can be found in Tables A5 3.3.3 Radiation protection instrumentation to A10 and Figures A5 to A9. In 1998, there All measuring instruments to monitor the ac- were no radiological events to be notified un- tivity and radiation level in the plant, as well as der the Inspectorate's Guideline R-15. radiation releases to the environment, personnel monitors and personnel dosimetry sys- 3.3.2 Releases to the environment and tems, worked satisfactorily in the year under direct radiation review. KKG participated successfully in the Table A4a presents the admissible limits for the annual comparison measurements for person- release of radioactive materials from KKG, the nel dosimetry departments organised by the 1998 annual releases, and the dose values Federal Committee for Radiation Protection

30 HSK Annual report 1998 • Gosgen Nuclear Power Plant (EKS) and was able to provide proof of the re- course of a pilot experiment.The results of the quired measurement accuracy. study are expected to become available at the beginning of 1999 and should allow the plant to improve assessment of the safety aware- 3.4 Personnel and organisation ness area. Two representatives of the IAEA visited KKG 3.4.1 Personnel and training and the Inspectorate in order to prepare and The licensed members of the shift groups took discuss procedures for the intended OSART part in simulator revision training during one- mission to KKG in November 1999. week courses on the simulators of the simulator school (GFS) in Essen, Germany. They were supervised by a KKG shift technical ad- 3.5 Emergency preparedness visor and by GFS personnel. Special courses were carried out to prepare the shift technical The emergency exercise carried out by KKG in advisors for their role as supervisors. The ba- the course of the overall emergency exercise sic simulator course was also carried out in "GAIA" is described in detail in Section 10. Essen for one future reactor operator. From the year 2000, it is intended that training will be carried out on KKG's own simulator, 3.6 Radioactive waste which is currently being installed. During the year under review, repeat train- During the year under review, the quantity of ing of licensed personnel in the area of reac- raw radioactive waste (see Table A11) was as tor physics, with special emphasis on the use expected from the experience of previous of MOX fuel assemblies, was completed in years. Distillation residues were conditioned three courses at the PSI reactor school. Sev- with bitumen in this period and mixed wastes eral thermohydraulic courses were carried out were sent to PSI for sorting and treatment. for licensed personnel in Biblis, using a glass There, the combustible wastes were inciner- model of a pressurised water reactor. Several ated and the ashes and non-combustible shift electricians from the operational depart- wastes were cemented.The packages of con- ment maintained their specialised knowledge ditioned wastes produced and the separated, at a high level through temporary assignment compressible wastes were returned to KKG. to the electrical department. In February, the Inspectorate approved the Employees of all departments refreshed up-dated release for a modified type of waste their technical knowledge, trained their practi- package, involving mixed wastes compressed cal skills, and underwent personal develop- under high pressure, according to the Inspec- ment in a variety of further courses. Of particu- torate's Guideline R-14. KKG has prepared lar note is the simulator training carried out for specifications for three further types of waste members of the electrical department. package, which are being produced in small quantities at PSI for KKG, and the correspond- 3.4.2 Organisation and operational ing release procedures are in progress. With management the exception of these three waste package There were no changes in the KKG organisa- types, KKG has now obtained updated release tion during the year under review. The approvals, according to Guideline R-14, for all workforce of the plant at the end of 1998 was types of waste package which are currently 377 persons (1997: 377). produced. The additional documentation on KKG has started with the introduction of a older types of resin waste package, submitted formal quality management system and has by KKG, has been examined and released by submitted a first draft of the quality assurance the Inspectorate. Nagra is examining the suit- handbook to the Inspectorate for review. The ability for final storage of three further waste system is based upon the IAEA document package types, for which additional documen- "Quality Assurance in Nuclear Power Plants tation has been provided. and other Nuclear Installations" (Safety Series The raw waste collected with a view to later 50-C/SG-Q, 1996). It is intended that the sys- treatment was kept under appropriate condi- tem be put into use during the second half of tions in premises in the controlled zone. Con- 1999. ditioned wastes were routinely brought to and During the year under review, KKG partici- kept in the interim storage facility. pated actively in the research project "Deter- mination of Safety Awareness" of the Psycho- logical Institute at the University of Berne. Members of staff were interviewed in the

HSK Annual report 1998 • Gosgen Nuclear Power Plant 31 3.7 OveralB judgement by the Inspectorate The condition of the Gosgen plant and the operational management can be rated as good with regard to nuclear safety and radiation protection. There were no notifiable incidents in this year. The annual collective dose for internal and external personnel again reached only a very low value. The amount of radioactive material released to the environment lay well below the limits set by the authorities. The radioactive doses for the population are thus insignificant.

32 HSK Annual report 1998 • Gosgen Nuclear Power Plant 4. Leibstadt Nuclear Power Plant

Aerial view of the nuclear power plant Leibstadt

4.1 Operational data and 4.2 Plant safety

results 4.2.1 Particular events The Leibstadt nuclear power plant (KKL) is According to the Inspectorate's Guideline R-15 equipped with a boiling water reactor and (" Reporting on the operation of nuclear power started commercial operation in 1984. In 1998, plants"), two notifiable events were allocated it originally had a net electrical output of 1030 to class B and to level 0 on the international MW. KKL carried out a power uprating during nuclear event scale, INES (see Section 12.7 the year under review. On October 31, 1998, and Table B2 of the Appendix). Both events KKL, as a first step, increased thermal power occurred during periodic functionality testing. by 6 % from 3138 MW to 3327 MW, on the One related to the failure to start of an emer- basis of approval by the Federal Council and gency power supply unit, the other to the fail- licensing by the Inspectorate. The net electri- ure to close of an isolation valve in the reactor cal power now amounts to 1080 MW. Addi- water sampling system. Both events were of tional data concerning the plant are summa- minor, safety-related importance and led to no rised in Tables A1 and B3 of the Appendix; restrictions on plant operation. Figure B2 shows the functional diagram of a boiling water reactor plant. 4.2.2 Work during the refuelling outage In its 14th year of operation, the Leibstadt During the outage from July 31 to August 26, nuclear power plant reached a load factor of the usual tasks were performed, such as refu- 89.2 % and an availability factor of 92.9 %.This elling, maintenance work, periodic inspections year, the revision outage lasted 26 days. Dur- of components, plant modifications, examina- ing power operation, a disturbance in the tions and functionality tests of systems and course of periodic testing of a turbine bypass components. valve led briefly to an automatic reduction in All pipe welds of the ten input nozzles (N3 reactor power to 80 %. During the period un- nozzles) of the recirculating lines to the reac- der review, there was no unplanned reactor tor pressure vessel were subjected to periodic scram. ultrasonic inspection. The automated inspection procedure and the inspection personnel had previously been qualified using a mock-up

HSK Annual report 1998 • Leibstadt Nuclear Power Plant 33 4.2.3 Plant modifications During the year under review, backfitting of safety-relevant, motor-driven valves was carried out as an important plant modification.This was necessary since recent findings had shown that loads on the valves in the case of an accident could be higher than originally assumed. The most extensive modification was to the high pressure, core-spray injection system, in which the injection gate valve and the minimum flow valve were replaced together with their injection drive units. The welds of the gate valve were subjected to a base-line ultrasonic inspection after they had been welded into the piping. The necessary measures from the backfitting programme for motor driven valves were carried out on more than 40 valves. Among other things, these involved the replacement of shafts, shaft locking nuts or drives, as well as new drive settings or higher closure torques for the casing bolts.

Mechanised weld seam testing on a pressure nozzle of The second of the two emergency exhaust a reactor recirculation pipe Source- NPP Leibstadt gas units was equipped with pressure-resistant filters for suspended solids, in order to facility. Furthermore, the core shroud and other improve stability and functional safety in the reactor internals were inspected using under- case of severe accidents. water video cameras. No indications were Further important plant modifications were found which would relate to cracks or other carried out to the instrumentation and control defects. The required leak-tightness of the systems, both in order to achieve operational containment was demonstrated by leakage improvements and to cope with the KKL tests on the containment seals. power uprating. These included: Replacement with improved T-pieces in the - Replacement of 16 pressure transducers in hydraulic control units of the control rod drives the containment by ones with higher resist- was continued on 36 of the total of 149 drive ance to radiation in the context of the age- units. ing surveillance programme. The cushioned check valves were tested in - Alterations in the control systems for reac- one feedwater line and showed leakages. Af- tor water circulation, water level, and ter increasing the clearance of the cushioning feedwater in order to avoid a reactor scram pistons, they were tight. in the case of loss of a feedwater pump. Four of sixteen blowdown lines from main- - Alterations in the control systems for the tur- steam safety relief valves were checked using bine and the feedwater to take account of an endoscope in the course of the ageing sur- the increased flows of steam and feedwater veillance programme. Furthermore, wall thick- arising from the power uprating. ness measurements were carried out on two distribution heads in the condensation pool. 4.2.4 Fuel elements and control rods Wall thickness measurements of piping in In the 14th fuel cycle (1997/98), the activity of the secondary area of the plant were contin- the reactor water and exhaust gas gave indi- ued as part of the programme to analyse for cations of fuel-assembly damage. One defec- weak spots due to erosion corrosion. During tive assembly was identified during shutdown this revision, the previous programme of visual for the annual revision and subsequent leak- inspections and ultrasonic examinations was tightness testing of all fuel assemblies. Fric- supplemented by radiographic examination of tional wear due to debris was determined to smaller diameter piping. No reductions below be the main cause of damage. the prescribed values were found. In the spring of 1998, the Inspectorate laid During the maintenance work, examinations down criteria for renewed insertion of the and inspections, no defects were found which SVEA96 fuel assemblies, which had shown would impair the safety of the plant. increased, localised, cladding corrosion (see 1997 annual report).These criteria require that the remaining wall thickness of the fuel-element cladding in the spacer regions, at the end

34 HSK Annual report 1998 • Leibstadt Nuclear Power Plant of life, is at least 50 % of the manufactured wall For the first time in cycle 15 (1998/99), a sig- thickness. This results in the requirement that nificant proportion of the fuel assemblies (92 the residual wall thickness at the beginning of from a total of 648) has been fitted with filters insertion be at least 70 %, which is to be dem- against debris in order to avoid fuel assembly onstrated by measurement. damage, which has been caused, to date, in Furthermore, the insertion period of the KKL primarily by frictional wear. SVEA96 assemblies has been limited initially to During the present 15th cycle, there have five cycles, with the exception of a few test been no indications of fuel-assembly damage, assemblies. This requirement resulted from including the period after power uprating to the investigation of four assemblies which had 106 % on October 31, 1998. been exposed for six years, after the 13th op- During the year under review, one shipment erational cycle (see 1997 annual report), where consisting of 32 depleted fuel assemblies, was cladding defects as a result of increased, local- sent for reprocessing. ised corrosion were found. The reduction in the permissible thermal loading of the SVEA96 4.2.5 Probabilistic safety analysis (PSA) & assemblies after the 4* cycle of use has been accident management (AM) retained. In the spring of 1998, KKL submitted a revised During the revision shutdown, extensive PSA Level 2 analysis to the Inspectorate. Quali- eddy current measurements of the oxide layer tative evaluation of this study by the Inspector- thicknesses in the spacer regions of fuel rods which had been exposed for one to four years were carried out and the residual wall thicknesses were determined. These measurements served to demonstrate adherence to the Inspectorate's criteria and to assess effectiveness of the modified water chemistry. The procedure for determining the residual wall thickness was qualified by destructive examination of individual fuel rods in the PSI hot laboratory. Statistical evaluation of all measurements showed adherence to the Inspec- torate's criteria, so that further use, in particular, of the four-year-old SVEA96 fuel assemblies is justified. Furthermore, the measurements of oxide layer thickness indicate that the progress of localised corrosion has been significantly reduced since the change in water chemistry at the beginning of cycle 14 (September 1997). This supports the hypothesis that too low a content of iron in the reactor water (so-called "iron deficiency") is a major cause of the increased, localised, cladding corrosion. During the shutdown, 191 of the total of 648 fuel assemblies were replaced for the 15th operational cycle (1998/99), including all 184 fuel assemblies with an 8x8 fuel rod configuration. The fuel rod cladding has been subjected to special pre-treatment ("autoclaving")forallof the 104 newly inserted fuel assemblies of the SVEA type.This measure is expected to result in a lower susceptibility to increased, localised, cladding corrosion. Furthermore, 77 four-year- Transport container for spent fuel elements old SVEA96 assemblies, which had been pro- <"• c N=P t d visionally removed during the 1997 shutdown, ate showed that it takes account of the main were reloaded into the core, since they satisfy physical/chemical phenomena which are ex- the Inspectorate's criteria. For test purposes, pected to occur in connection with a severe two five-year-old SVEA96 assemblies and 8 accident, but that several points still require new (10x10) assemblies from another manu- clarification. facturer were inserted. The revision to the PSA study for externally initiated events, required in the Inspectorate's

HSK Annual report 1998 • Leibstadt Nuclear Power Plant 35 expertise on power uprating, was subjected to in progress according to the ASP guideline intensive evaluation by the Inspectorate at the approved by the Inspectorate. end of 1997 and during 1998. This evaluation To date, the ASP documentation examined essentially confirmed that the analysis was by the Inspectorate has not revealed any correct, both in a qualitative and a quantitative safety-relevant gaps in the maintenance pro- way. During the next few years, a new evalua- grammes. Furthermore, the present results tion of the danger from earthquakes will be indicate that no unacceptable reduction in carried out for all Swiss nuclear power plant safety-related properties is to be expected in sites. It remains to be seen whether this new the near future. evaluation at the Leibstadt site will have an influence on the PSA study for externally initiated events. At the end of 1998, KKL submitted a revised version of the Human Reliability Analysis (HRA) part of the Leibstadt PSA.The Inspectorate will deal with this study in 1999. In the course of an audit, KKL answered the Inspectorate's questions with regard to the present situation and to future projects in the framework of the systematic introduction of Severe Accident Management Guidance.

4.2.6 Ageing surveillance programme The existing documentation on the ageing surveillance programme for the mechanical engineering area of the main-steam and feedwater systems was examined and assessed by the Inspectorate. The Inspectorate paid close at- Exchange of an emergency supply diesel motor. The emergency power supply aggregate is being unloaded tention to the way in which ASP measures after its delivery to the nuclear power plant. have been put into practice. KKL has submit- Source: NPP Leibstadt ted further documentation on the ASP of the reactor pressure vessel. A pilot project was started on the ASP of components belonging to safety classes 2 to 4. In the course of this 4.3 Radiation protection pilot project, those components belonging to safety classes 2 to 4 which are of the greatest 4.3.1 Protection of personnel relevance to safety will be selected on the For the calendar year 1998 (1997 values in basis of probabilistic, engineering, and radia- brackets), the following values of collective tion protection criteria.They will then be evalu- dose were determined for KKL: ated with regard to their ageing behaviour so as to provide a basis for possible modifications Activities ; Person-Sv to maintenance activities.The procedure being Planned outage 0.72 (0.83) developed in the KKL pilot project for mechani- Operation 0.37 (0.46) cal engineering components belonging to Annual collective dose ' 1.09 (1.29) safety classes 2 to 4 will also be adopted, in future, in the other Swiss nuclear power In the main, only routine maintenance work plants. was carried out in this year, so that the dose In the area of 1E electrical components, the was lower than in the previous year.The annual ASP continues to be developed in the context collective dose lies well below the Inspector- of the guideline approved by the Inspectorate. ate's Guideline value of 4 Person-Sv. During the year under review, the Inspectorate Among other activities, a highly detailed, received documentation on penetrations, limit radiation protection plan for periodic inspection switches and electrical contact thermometers. of the N3 nozzles at the reactor pressure ves- Furthermore, it assessed the ASP documenta- sel was prepared and submitted to the Inspec- tion for transmitters and valve drives. torate. Furthermore, the intended work was In the area of structural engineering, the practised in advance under conditions simulat- ASP documentation for the reactor building, ing the in-situ work situation. Nevertheless, the and for various auxiliary buildings within the planned values were exceeded.This was due, earthquake classification EK1, was examined on the one hand, to increased dose rates at the by the Inspectorate. Base-line inspections are work location and, on the other hand, to the

36 HSK Annual report 1998 • Leibstadt Nuclear Power Plant considerable difficulties encountered, in part, 4.3.2 Releases to the environment and during the inspection (see also Section 11.4). direct radiation In general, the radiological condition of the Table A4a shows the limit values for the re- plant largely corresponded to that of the pre- lease of radioactive materials from KKL, the vious year. With respect to the alpha contami- total amount released in 1998 and the result- nation caused by fuel assembly damage in pre- ing dose values for individuals in the vicinity of vious years, it had to be expected that similar the plant, calculated according to the Inspec- conditions would again prevail as in the outage torate's guideline R-41. Radioactive releases via revision work from 1994 to 1996. The alpha the exhaust gas, in the form of aerosols, iodine measurement programme, which was satis- and noble gases, lay well below the limiting factorily tested in previous years, was re- values.This was also true for tritium and other peated. This showed a slight increase in the radioactive releases in waste water. Table A4b radiological toxicity of the nuclide mixtures shows the releases of noble gases and iodine compared with the previous year. via the exhaust gas system and for tritium and The mean value of the dose rate at the remaining radioactive substances via the recirculation loops of 2.23 mSv/h (1997: waste water during the last five years. Release 2.1mSv/h) has again increased slightly com- values less than 0.1 % of the release limits are pared with the previous year. It lies above the not shown. guideline value of 2.0 mSv/h in the operating The calculated yearly worst dose for indi- licence.This dose rate can be correlated with vidual members of the population in the vicin- the Co-60 concentration in the reactor water, ity of KKL is approximately 0.002 mSv for which was higher during the last cycle than the adults and 0.004 for infants. These values lie mean value in the previous year as a result of well below the guideline dose of 0.2 mSv per renewed insertion of older GE-8 fuel assem- year according to the Inspectorate's Guideline blies. The mean value of the dose rate in the R-11. Articles 5 and 6 of the Radiation Protec- recirculating loops must be exactly monitored tion Ordinance state that activities which result in connection with the changed water chem- in an effective dose of less than 0.01 mSv per istry (see Section 4.2.4). If necessary, further year for the persons concerned are deemed measures must be introduced in order to con- justified and optimised. This means that no tinue to keep the personnel doses low. The further efforts are necessary to reduce radio- dose rates at those reactor pressure vessel active releases and the resulting doses for the components which have been monitored over population. many years show slightly falling, or constant The quarterly measurements carried out by values. the Inspectorate as a check, and the half-yearly To reduce the dose rate, 59 tonnes of tem- comparison measurements of the Section for porary shielding were installed, of which Radiation Monitoring, Freiburg (SUeR) on aero- 49tonnes were lead. During the shielding sol and iodine filters, as well as on exhaust gas work, a total of 34 Person-mSv were accumu- and waste-water samples, showed good lated. This is more than offset by the dose re- agreement between the results and the KKL duction of about 1 Person-Sv. Individual doses values. never exceeded the limit. In 1998, the highest The dose-rate measuring probes of the dose individual dose from external radiation was monitoring network (MADUK) in the vicinity of 12.7 mSv (1997:12.8 mSv). For further details, KKL showed no significant increase above the refer toTables A5-A10 and Figures A5-A9 of the level of the background radiation. In close prox- Appendix. imity to the nuclear power plant, the ambient A total of 1174 persons were subjected to dose rate is higher due to direct and indirect entry and exit measurements using the incor- radiation from the turbine building. The meas- poration monitor; no cases of gamma doses ured values at the perimeter fence were at above the screening threshold were found. As normal levels as in previous years.Thus the lim- a result of the gamma/alpha ratio determined iting emission values for direct radiation out- externally at various components, there were side the plant site (1 mSv per year for living, also no indications for incorporation of alpha recreation and work rooms, and 5 mSv per emitters. There was no spread of contamina- year in other areas), given in Article 102, Clause tion in the plant and no contamination of per- 3 of the Radiation Protection Ordinance, were sonnel which could not be eliminated by nor- adhered to. mal washing. During 1998, there were no radiological 4.3.3 Radiation protection instrumentation events notifiable under the Inspectorate's All measuring instruments to monitor the ac- Guideline R-15. tivity and radiation level in the plant, as well as radiation releases to the environment, person-

HSK Annual report 1998 • Leibstadt Nuclear Power Plant 37 nel monitors and personnel dosimetry sys- KKL has offered early retirement to works tems worked satisfactorily in the year under staff and this was accepted by several employ- review. KKL participated successfully in the ees.The resulting vacancies were filled, in part, annual comparison measurements for person- by hiring new staff. nel dosimetry departments organised by the KKL and KKB have established a working Federal Committee for Radiation Protection group to investigate possible areas for co-op- (EKS) and was able to provide proof of the re- eration through the common use of material, quired measurement accuracy. Furthermore, personnel and equipment in both plants. One the personnel dosimetry department was sub- examples of this is exchange of specialised jected to renewed checks by an expert from personnel in the field of maintenance. The In- the Inspectorate (Institute of Radiophysical spectorate welcomes this co-operation, since Applications) according to Article 46, Clause 3 it supports the exchange of information. of the Radiation Protection Ordinance, which KKL continued its efforts to intensify the limits the validity of certification to five years. level of safety awareness of plant employees. Certification of the KKL personnel dosimetry With the help of special seminars, personnel department was extended for a further five are being trained to be prepared for the unex- years as a result of this inspection. pected also during routine work. The basic at- titudes involved here provide an effective approach to early detection of possible 4.4 Personnel and organisation weaknesses and thus provide an additional barrier in the overall safety concept. 4.4.1 Personnel and training KKB continued its programme to investigate One shift technical advisor and three level A "near events" and identify human deficien- reactor operators passed their licence exami- cies, and was able to derive several improve- nations in the year under review. The number ments from this. The Inspectorate welcomes of licensed personnel is given in Table A2. the fact that the reporting level for incidents is Training was completed on the KKL simula- being set so low, and regards the knowledge tor in the area of those systems which were gained from this activity and from the meas- not modelled on the simulator used previously ures introduced as providing an important con- in Madrid. Furthermore, ten-day simulator tribution to plant safety. courses on start-up and shut-down of the whole plant were carried out, in particular for deputy shift-supervisors. The first phase of 4.5 Emergency preparedness training on the KKL simulator, started in 1996, was successfully completed in 1998; all of the During the year under review, KKL carried out licensed shift personnel attained a uniform the works security exercise "LIBERTY" under level of training. the observation of the appropriate Federal Employees of various departments took Office of Energy (BFE) department responsible part in courses at an appropriate level at the for security. PSI radiation protection school and were thus The aim of this exercise was to test team- able to bring their knowledge of radiation pro- work, and permit practice, under difficult con- tection up to date. Prior to the revision shut- ditions, using the relevant, prepared documen- down, those supervising external personnel tation. Furthermore, it was desired to assess were instructed in safety at work and in fire the capabilities and requirements of the vari- protection. ous people involved, both internally and exter- Employees of all departments refreshed nally, such as the KKL emergency team and the their technical knowledge, trained their practi- Cantonal police department, in the context of cal skills, and underwent personal develop- a concrete problem. ment in a variety of further courses. Of particu- The responsible BFE department concluded lar note were seminars for new managers and that the goals of the exercise were reached, seminars for shift personnel on the theme of whereby co-operation with the cantonal police "near events". department should, in future, be practised more often. 4.4.2 Organisation and operational The Inspectorate confirmed the prepared- management ness for action of the emergency communica- There were no changes in the organisation at tion systems to the Inspectorate and to other KKL during the year under review. The KKL external bodies in the course of an appropriate workforce at the end of the year was 418 per- inspection. sons (1997: 406).

38 HSK Annual report 1998 • Leibstadt Nuclear Power Plant 4.6 Radioactive waste In particular, the following requirements were satisfied prior to approval of the first stage of During the year under review, the quantity of power uprating: raw radioactive waste (seeTable A11) was be- - Evaluation of plant operation over approxi- low the experience of previous years. Modifi- mately one year prior to power uprating con- cations to the condensate polishing equipment firmed trouble-free performance, including led to a reduction in the amount of waste from the behaviour with regard to fuel-assembly ion-exchange resins.The amounts of combus- damage. tible and compressible wastes arising in the - The technical specifications were appropri- context of the annual revision shutdown were ately modified to suit the altered boundary significantly reduced by tightening up waste- conditions. management procedures. Ion-exchange resins - Those plant modifications necessary in the were routinely cemented with concentrates, context of power uprating were submitted according to the corresponding approval per- to the Inspectorate and approved by it. They mit of the Inspectorate. Mixed wastes were include alarm settings and instrument set- taken to PSl, where the combustible wastes tings in the primary and secondary parts of were incinerated and the ash residue ce- the plant. The Inspectorate satisfied itself mented. The conditioned waste packages that the plant modifications and changes to were returned to KKL. settings had been correctly carried out and in January, the Inspectorate gave provisional function correctly. approval, according to its guideline R-14, to a - KKL prepared a monitoring and inspection new type of waste package, in which concen- program which, among other things, in- trates are treated without ion-exchange resins. cludes core behaviour and performance of KKL will prepare a limited number of such pack- the whole plant. It also covers instructions ages, as required, in order to carry out testing for the preparation, monitoring and evalua- of the package type. In June, the Inspectorate tion of each power uprating increment with approved an updated release for the combus- regard both to safety and radiological con- tible residues cemented at PSl. KKL is thus in sequences. Thus, the conditions and re- possession of updated release approvals for all quirements applying to the first stage of types of waste packages currently produced. power uprating have been fulfilled. Different raw wastes, awaiting later treatment, are stored under appropriate circum- stances in an unconditioned form in premises 4.8 Overall judgement by the within the control zone. Conditioned waste packages, especially the cemented resins and Inspectorate concentrates, are routinely brought to and held The Leibstadt plant condition and the opera- in the interim storage facility. tional management can be rated as good with regard to nuclear safety and radiation protection. The power uprating by a 6% increment 4.7 Fulfilment of regulatory was carefully planned and carried out according to expectations. The two notified events requirements were of minor relevance to nuclear safety and The approval, dated October 28, 1998, for led to no operational restrictions. power uprating was linked to various condi- The collective dose (internal and external tions and requirements, which apply already to personnel) again reached only a low value for the 1st stage of the increase to 106 %. Fulfil- a boiling water reactor of this type, as a result ment of these requirements took place as fol- of dose-reducing measures. The amount of lows: radioactive material released to the environ- - The approval involved no change to the lim- ment lay well below the limits set by the au- its for release of radioactive materials to the thorities. The radioactive doses for the popu- environment. KKL monitoring of these relation are thus insignificant. leases corresponds to the state of the art. - In recent years, KKL has introduced systematic measures to reduce the radiation exposure of works employees. This has been apparent from the low collective and individual doses. It is expected that these efforts to j HIM? PJICllSfSl optimise radiation protection be continued in such a way that the personnel radiation doses I Eelft BLMMK remain low following the power uprating.

HSK Annual report 1998 • Leibstadt Nuclear Power Plant 39 5. Central Interim Storage, Wurenlingen

Aerial view of the construc- : tion site for the interim storage facility for radioactive waste (ZWILAG)

5.1 Supervision of construction systems, equipment and components was in- On August 21, 1996, the Federal Council spected. gave a license to the Zwischenlager Wuren- During the year under review, construction lingen AG (ZWILAG) for the construction and work largely proceeded according to plan and operation of interim storage facilities for radio- without delay. The ZWI LAG plans foresee that active waste, including the associated auxiliary individual parts of the plant will go into opera- installations, as well as for the construction of tion in 1999 and 2000. a conditioning plant and of an incineration and melting plant in Wurenlingen. Construction of all these plants, together known as the central 5.2 Review for operation interim storage facility (ZZL), is subject to the supervision of the Inspectorate. license for the waste In the course of its supervisory activity, the treatment plants Inspectorate has examined numerous docu- The operation license for the conditioning fa- ments (plans, certificates and calculations, de- cility and forthe incineration and melting plant sign specifications for systems and for individual has not yet been granted by the Federal Coun- pieces of equipment, etc.). After demanding and cil. The relevant application, together with the obtaining all necessary supplements, changes associated safety report, were submitted by and corrections, the Inspectorate has approved ZWILAG on December 15,1997. Some supple- and released these documents, insofar as they ments required by the Inspectorate and the took due account of the current status of tech- KSA were submitted during the course of nology and were in accordance with the condi- 1998. The review by the Inspectorate was de- tions set in the license. Regular site inspections layed by other activities and could not be com- have been carried out by the Inspectorate, or by pleted in 1998.This work will be finished by the structural engineering experts acting upon its middle of 1999, so that the Inspectorate's re- behalf, since the beginning of construction work view report will become available during the at the ZZL. Furthermore, assembly work on summer of 1999.

HSK Annual report 1998 • Central Interim Storage, Wurenlingen 41 5.3 Waste from reprocessing

Spent fuel from the Swiss nuclear power plants is routinely reprocessed in La Hague (France) by the COGEMA company. Once again in 1998, production reports from COGEMA show that the amount of waste produced was smaller than had been anticipated from the earlier specifications. The corresponding reprocessing plant in Sellafield (United Kingdom), belonging to the BNFL company, has been in operation since 1995; however no fuel from Swiss nuclear power plants has yet Container storage hall for high-level waste and spent fuel elements Source- ZWILAG. Baden been reprocessed there. The waste arising at COGEMA and BNFL from reprocessing of fuel assemblies from the came apparent that the substitution of all low- Swiss nuclear power plants has to be returned level and intermediate-level wastes by vitrified to Switzerland. Vitrified high-level waste from high-level waste, as proposed by BNFL, has reprocessing at COGEMA is ready for return. advantages not only with regard to reducing However, it can only be brought back to Swit- the number of transports, but also in terms of zerland if a suitable, interim storage facility is the safety aspects of further waste manage- available. The cask storage buildings at ZZL in ment. Wurenlingen and at ZWIBEZ at the Beznau NPP have been constructed for this reason. Furthermore, the conditions set out in earlier 5.4 Provision of transport governmental decisions concerning the preliminary assessment of the suitability for im- and storage casks port of this waste must be satisfied com- The concept which has been approved for the pletely, and suitable transport and storage interim storage of spent fuel assemblies and casks must be available. of vitrified high-level waste from reprocessing BNFL has proposed that the low-level and foresees that these wastes will be contained intermediate level wastes from reprocessing within massive transport and storage casks be retained in the United Kingdom, because of (TS casks), which will be brought to the ZZL their large volume, and that this should be from the nuclear power plants, or from the re- compensated for by returning an additional processing plants, and stored there in the cask amount of vitrified high-level waste to the cus- storage building. In accordance with the li- tomers. According to the proposed principle of cense of the Federal Council dated August 21, equivalence, the approximately 2000 m3 of 1996, these TS casks must satisfy the require- low-level and intermediate-level wastes should ments which were defined by the Inspectorate be substituted for by an additional 15 % (i.e. in its relevant review report. The shareholders approximately 6 m3) of high-level waste. The of ZWILAG started acquisition of suitable TS Swiss customers of BNFL would like to take casks already in 1996. To date, the Inspector- advantage of this offer and have submitted a ate has approved the choice of two types of corresponding application, which has to be cask for spent fuel assemblies and for vitrified assessed by the authorities with regard to vari- high-level waste from reprocessing. In 1998, ous technical, legal and political questions.The the Inspectorate supervised the design and Inspectorate has examined the proposed prin- the manufacture of TS casks for spent fuel as- ciple of equivalence with regard to the safety- semblies. At the Inspectorate's request, the relevant consequences of such a substitution Swiss Association for Technical Inspections on waste management in Switzerland. It be- (SVTI) has followed acceptance testing in detail.

42 HSK Annual report 1998 • Central Interim Storage, Wurenlingen 6. Paul Scherrer Institute (PSI)

Construction site for the Swiss synchrotron-light ~.f"> source (SLS). This is a large project at the Paul t Scherrer Institute. Source: PSI. Villigen

6.1 The PSI in Villigen and 6.2 Research reactors

Wurenlingen 6.2.1 PROTEUS The Paul Scherrer Institute is a multi-discipli- The PROTEUS research installation had been nary research institute for natural sciences and shut down since the completion, as planned, of engineering with fields of work in the areas of the HTR experiments in June 1996. In the mean- elementary particle physics, biological sci- time, the reactor was modified for light water ences, solid-state research, materials science, reactor (LWR) experiments.The Inspectorate's nuclear and non-nuclear energy research, as permit for operation of the modified LWR-PRO- well as environmental research related to the TEUS (power of approximately 1 kW at the production and use of energy. It consists of the maximum, permissible neutron flux) was East sector (located in Wurenlingen) and the subject to regulatory conditions. After these West sector (located in Villigen), which are con- conditions had been satisfied, operation nected together by a bridge overthe river Aare. recommenced at the beginning of November Supervision by the Inspectorate covers nuclear 1998, initially up to 1 % of the maximum li- installations, as designated by Federal Atomic censed neutron flux. During the year under re- Law, in the East sector and all other installa- view, the reactor was operational for 551 hours. tions in both sectors, insofar as they are rel- At the end of the reporting period, the li- evant to the Radiation Protection Law. censed personnel amounted to two reactor In addition to various laboratories, and accel- physicists, one reactor technician and an operator installations with the spallation neutron erator. Three people took part in a training pro- source SINQ, the Inspectorate's supervision, gramme for radiation protection experts and during the year under review, also covered the inspectors, organised by the PSI radiation pro- PROTEUS research reactor, the hot laboratory, tection school (see also Chapter 14). At the end the decommissioned DIORIT research reactor of December 1998, one reactor physicist left and the SAPHIR research reactor (no longer in the licensed staff as detailed above; however, operation), the disposal of radioactive waste, and he is still available, as necessary, during reac- the federal interim storage facility BZL. On the tor operation. Training is in progress of a reac- basis of a safety report and further documenta- tor physicist, whose licensing by the Inspector- tion, the Inspectorate was able to approve the ate is foreseen for spring 1999. In this way, the major PSI project on a synchrotron light source intended quota of licensed personnel for PRO- (SLS), with regard to the Radiation Protection TEUS will again be attained. Ordinance, and this facility is currently under con- The modification of the research reactor struction. In the facility for medical radiation ap- from HTR-PROTEUS to LWR-PROTEUS in- plications, surveillance is carried out jointly with cluded four important alterations to the core the Federal Office for Public Health (BAG). Ac- configuration. These were: cording to the valid radiation protection law, the - a doubling in the number of the safety/shut- Inspectorate is also the supervisory authority for down rods from 8 to 16; radiopharmacy devices.

HSK Annual report 1998 • Paul Scherrer Institute (PSI! 43 - the inclusion of a moveable test tank for 6.2.2 SAPHIR 4.5 m long boiling water reactor fuel assem- The SAPHIR research reactor has not been in blies of the KKLtype; operation since the beginning of 1994. During - the assembly of a new heavy water tank for the year under review, one group of rooms in the driving zone; the plant was backfitted with regard to safety - the assembly of the new D2O and H2O cir- according to current technology. cuits. During 1998, PSI pursued its intention of Furthermore, a new storage facility for the KKL preparing SAPHIR for decommissioning. On fuel assemblies and a gamma scanning appa- December 9th, 1998, PSI submitted an applica- ratus were built and put into operation. tion for approval of plant decommissioning. The collective dose for the four licensed This application was accompanied by a de- operators and a further five people for 1998 commissioning report, which described the was 1.4 Person-mSv. This arose primarily from way in which the plant would be returned to a preparations for the return of nuclear fuel "greenfield site" in five stages. (FDWR-MOX and spherical HTR fuel elements) Looking after the plant (shut-down reactor to their owners abroad. and nuclear fuel storage) continues to require The plant operated without any problems, an adequate number of trained personnel. Li- and without any events notifiable according to censed personnel must continue to be avail- the Inspectorate's Guideline R-25. able as long as the plant remains within the jurisdiction of the nuclear operating licence. The collective dose in 1998, for three people in SAPHIR, was 0.5 Person-mSv. During the period under review, no notifiable events occurred.

6.2.3 DIORIT The DIORIT research reactor ceased operation in 1997. During the year under review, a further step was taken towards the decommissioning approved in 1994: the core components water shield, reactor tank 1 and reactor tank 2 were removed, dismantled and subjected to final conditioning. In the course of this conditioning, a total of 3930 kg of aluminium was melted in a crucible, situated in a newly built disposal plant at DIORIT and poured into concrete containers. In 1998, construction of a dismantling plant in the second underground floor of DIORIT was essentially completed. The collective dose accumulated by the dismantling squad (seven employees) was 7.2 Person-mSv during the year under review. No notifiable incidents occurred in 1998. During the year under review, the outside of the DIORIT building was renovated and all win- dows in the reactor hall were replaced. At present, the DIORIT building is being used by approximately 50 employees of various research groups, both as office space and for non-nuclear experiments.

6.3 Accelerator, proton beam channels and ex- Sectional view of PROTEUS as it is configured for the light water reactor (LWR) experiments. In the centre perimental areas there is a test tank, movable in the vertical direction. In the year under review, the operating licence This contains the LWR fuel elements to be examined. for the PSI accelerator was renewed. In addi- The tank is surrounded by buffer and thermal driving zones. In the side reflectors there are the shutdown, tion to the beam intensity of 1.5 mA in routine control and safety systems of the reactor operation, short operational periods at higher

44 HSK Annual report 1998 • Paul Scherrer institute (PS!) beam intensity are now possible for the ring accelerator.This is subject to a condition set by the Inspectorate, namely that operational instructions be prepared and subjected to release by the management. During the year under review, operation of the PSI proton accelerator was characterised by a long interruption due to improvement work in the area of the beam splitter. Stable operation of the PSI accelerator plant became possible in the second half of the year. The Philips cyclotron (variable energy up to 70 MeV) operated without interruptions over about 5150 hours for experiments (nuclear physics, medical research, radiochemistry, materials research, high-energy physics, detector development, astrophysics), as well as an injector for high-energy experiments with polarised protons. Injector II (72 MeV) was in operation Spallation neutron source SINQ. The experimental devices for 3860 hours and fed mainly into the ring are in the foreground. source: PSI. viiiigen cyclotron, but was also used, to a smaller extent, for radioisotope production.The 590-MeV possibility for measurement of the tempera- ring cyclotron operated for 3740 hours in 1998 ture in representative target rods. Up to the and reached weekly proton beam current av- end of the year, this second target was oper- erages of up to 1.45 mA. Beam losses mostly ated with a proton current, integrated over responsible for scattered radiation and activa- time, of 2 Ah without any unexpected side-ef- tion were able to be reduced further. fects. The figure shows the operational history, Operation of the accelerator installations whereby it should be noted that this relates to with the associated experiments, involving the start of routine operation of a large, com- many internal and external research groups, plex, non-commercial, research plant. was carried out without any events notifiable In 1998, experimental operation com- according to the Inspectorate's Guideline R25. menced for the small-angle scattering plant, At the accelerator installation (excluding the time-of-f light spectrometer and the single- radiopharmacy and medical applications), the crystal diffractometer, as well as for the beam collective dose for 158 PSI employees was equipment (gas jet and package-per-tube dis- 56.8 Person-mSv in 1998. However, some of tribution system). A reflectometer, the neutron these people were also occupied in other fields radiography plant and a powder diffractometer of radiological work at the Institute, in addition are under construction. to their work with the accelerator. The highest individual dose within this group of people amounted to 4.8 mSv. The collective dose for 600 the approximately 380 national and foreign 500 experimenters during the same period was < 18Person-mSv. c 400 6.3.1 Spallation Neutron Source (SINQ) 03 During the long shut-down period of the accel- 300 erator at the beginning of the year under re- 03 view, the computer-based SINQ control sys- JO tem was renewed and successfully tested on 2 200 the basis of the operational experience from 03 1997. In the second half of the year under re- 100 view, unmanned plant operation was started following functionality testing and release by the Inspectorate of the personnel safety instal- 03 03 CD XI -Q £ _Q £ O E E lation for the SINQ experimental area. A sec- 03 "o 03 CD O O ond target of the same type was put into op- g CD s03. Q eration. In comparison with the first target, this CO z contains a number of experimental rods of Beam operation of the PSI spallation neutron source slightly different material composition and the SINQ in 1998

HSK Annual report 1998 • Paul Scherrer Institute (PSI) 45 During the year under review, the quantity of radioisotopes in circulation at the centre of Radiopharmacy (ZRP) has increased compared to previous years. An essential role in this was the distribution of 1-131 in the context of a commercial co-operation for the development of radioactively marked antibodies for radio-im- mune therapy goals. Otherwise, production involved chiefly radioisotopes for PSI's internal research and applications (PET), or work with radioisotopes which were bought-in. The collective dose for employees in Experimentalists of the laboratory for neutron scattering radiopharmacological production and medical use the neutron beam of the SINQ for their research work. applications (112 persons) was 32.1 Person- Source- PSI. Villigen mSv in 1998, with the highest individual dose being 8.3 mSv. During the year under review, In 1998, the collective dose for the 36 em- no events, which have to be notified according ployees involved in operating the SINQ-instal- to the Inspectorate's guideline R25, were relation was 1.8 Person-mSv.The 39 experiment- ported from the PET ZRR OPTIS and proton- ers from the neutron scattering laboratory therapy installations. accumulated 2.1 Person-mSv. No notifiable events were reported by those responsible for the SINQ plant during the year under review. 6.4 Hot Laboratory

6.3.2 Installations for medical applications Since its commissioning in the early sixties, the (PET, OPTIS, proton therapy) and hot laboratory has been used to an equal ex- radiopharmacy (ZRP) tent for basic research and for applied research The Federal Office for Public Health (BAG) and in the field of material technology of nuclear the Inspectorate co-ordinate their supervisory power plants. Furthermore, it is available for activities for the medical radiation applications important service activities, in particular in the at PSI.The BAG checks solely activities involv- area of safety-relevant investigations of mate- ing irradiation of persons, while the Inspector- rials and fuel assemblies from nuclear power ate is the responsible supervisory authority for plants, as well as for work on industrial and other aspects of radiation protection, espe- medical radiation sources.This PSI installation cially for operational radiation protection. is equipped to handle all common types of ra- Research in the context of the Positron dioactive materials (nuclear fuels and activated Emission Tomography Programme (PET) fo- materials). In addition to routine operation, cused on the neurological sciences. In com- preparations for a backfitting project, to be parison with the previous year, however, there carried out over the next few years, were a was a clear reduction in the number of PET further focus of activities during the year un- scans, whereby primarily the investigations der review. This project is a consequence of with F-18 continued to be carried out. A pack- the backfitting of safety equipment in the hot- age-per-tube distribution system for the rapid laboratory building complex required by the In- transfer of radioactive compounds went into spectorate. operation, for the first time, in 1998. In particular, radioactive laboratory waste During 14 weeks, distributed over the year from the laboratory itself was dealt with in under review, 266 persons and 5 animals, suf- several waste-conditioning programmes (see fering from eye melanoma, underwent radio- Sections 6.5.2 and 6.5.3). therapy in the OPTIS installation. The 2700th No notifiable event occurred in the hot labo- patient was treated during the year under re- ratory in 1998. During the year under review, view. the collective dose for the 71 employees sub- Ten persons underwent therapy with the jected to dosimetric control was 41.0 Person- spot-scanning technique in the 200 MeV pro- mSv; the highest individual dose was 4.1 mSv. ton therapy plant GANTRY, whereby top rota- tion of the treatment table was also used for the first time. The localised, therapeutic, total 6.5 Treatment of radioactive doses used were in the region of 30 to 72 CGE (Cobalt Grey Equivalent). All therapy treat- waste ments were carried out without complications, The PSI has a wide variety of waste types to using the established operational procedures. treat. These include radioactive waste from

46 HSK Annual report 1998 • Paul Scherrer Institute (PSI) federal and cantonal research installations, wastes (MIR waste) from the BAG collection from medicine and industry, and also some campaign was resumed in 1998, after approval from Swiss nuclear power plants. In this con- by the Inspectorate. Approximately one tonne text, the waste is conditioned to a state which of raw waste was incinerated in this context. is suitable for interim and final storage. In the operation box of the waste laboratory, radioactive waste falling within Federal respon- 6.5.1 Release procedures sibility (medical, industrial and research (MIR) in July, the Inspectorate released the pre-con- waste from the BAG collection campaign and ditioning of the beryllium reflector elements from PSI itself) were treated; e.g., the residues from the SAPHIR research reactor on the ba- from incineration were routinely cemented sis of the PSI specification and the positive according to the specification. A key focus in assessment by Nagra. Furthermore, the In- 1998 fell on sorting, compressing and cement- spectorate approved the retrospective docu- ing the MIR waste accumulated since 1994 mentation for compressed waste packages from the BAG collection campaign.The Inspec- from the hot laboratory which are, however, no torate was once again able to approve condi- longer produced. During the year under review, tioning of these wastes, after PSI had fulfilled PSI prepared the specifications for a further the pre-conditions set for this, namely connec- type of waste package from the hot laboratory tion of the exhaust system to the main chim- which is already being produced. These are ney, complete radiological monitoring, and the currently being examined by Nagra and by the requirements of a new licence for the release Inspectorate. of radioactive substances to the environment. To date, the Inspectorate has approved, ac- In 1998, PSI conditioned 398 drums with BAG cording to HSK Guideline R-14, releases for 8 raw waste into 248 drums suitable for final of the 11 types of waste package currently storage. At present, 123 drums containing BAG being produced. The specification of one type raw wastes await processing. of waste package is currently being examined A collective dose of 24.1 Person-mSv was by Nagra and by the Inspectorate. Further- accumulated by 13 persons during waste treat- more, PSI has submitted the specification for ment in the incineration plant and the waste a type of waste package to be produced in the laboratory; the highest individual dose was future. 3.4 mSv.

6.5.2 Incineration plant and waste 6.5.3 Further conditioning of waste in the laboratory sector PSl-East In the PSI incineration plant, during the year Liquid wastes containing a total of 174 gram- under review, a total of 59 tonnes of radioac- mes of plutonium were solidified with cement tive waste from Swiss nuclear plants, the PSI mortar and filled into 2892 packages of 1 litre and the BAG were incinerated in the 142 days each in the hot laboratory, according to the so- of operation of the two incineration cam- called FIXBOX procedure, from 1994 up to the paigns, no. 38 and no. 39. During 1998, the end of 1998. Production of these small pack- incineration plant functioned satisfactorily and ages was carried out according to programme its operation has been improved in comparison and without delays; final conditioning of these with previous years. As a result of the new QA is intended to take place in 1999.The two peo- systems, those delivering the wastes have ple carrying out these activities have accumu- sorted these well. In this way, lower amounts lated a collective dose of 13 mSv during this of damaging substances, whose vapours, time. The hot laboratory has already made aerosols and dusts could block the ceramic fil- preparations for solidification of the plutonium- ters, entered the incineration oven. Since the containing liquid wastes with a high proportion damage to the bearings of the exhaust fan, of (3 and y nuclides in the FIXBOX plant during which was observed earlier on one occasion, 1999. did not re-appear, better availability and higher The hot laboratory continued the campaign, through-put were attained in the incineration begun in 1997, for the compression of fuel plant. The collective dose of the operating per- wastes having high a, fi and 7 activities. Com- sonnel was kept low as a result of suitable pression activities had to be interrupted for shielding during loading of the oven. several months in order to carry out the nec- The incineration waste residues (ash), and the essary repairs to the crane in the hot cell dedi- ceramic filter cartridges arising from flue gas cated to these activities. Nonetheless, all ac- cleaning, were conditioned with cement mor- cumulated wastes were able to be tar into 52 packages of a specified type and compressed up to the end of 1998. In the returned, proportionally, to the plants. Incinera- main, the compressed packages were filled tion of the medical, industrial and research into steel containers, which are being stored

HSK Annual report 1998 • Paul Scherrer Institute (PSI) 47 in the hot laboratory awaiting their final condi- point for a short time. The untreated, radioac- tioning. tive, medical, industrial and research wastes The radioactive aluminium wastes arising (residual stocks from BAG collection cam- from decommissioning of the DIORIT plant paigns carried out from 1994 until 1998) are were melted down according to programme kept in storage buildings A and B until they are and the resulting ingots cemented into three treated. At the end of 1998, there were 123 16 tonne, KC-T12 containers (of 12 cm wall waste packages of various sizes in storage thickness) in accordance with the specifica- there. At this time, 238 packages containing tions. PSI has already made extensive prepa- various types of waste, as well as 6 m2 of bulk rations to further dismantle the DIORIT reac- waste, were stored in building C. 136 waste tor and to cement into KC-T12 containers the containers of 200 litres each, conditioned with steel, cast-iron, graphite and concrete parts cement mortar, were stored in the stockyard. arising from this. During the year under review, 74 packages were transferred from there to storage build- 6.5.4 Sector PSI-West ing C in specially prepared containers. Using remote manipulation equipment, PSI has broken down the dismantled parts from 6.6.3 Stockyard PSI-West the target-E reconstruction and packed these The temporary stockyard in the West sector, into two KC-T12 containers. It is intended that in which accelerator installation wastes in con- these be stored in a temporary stockyard at crete containers are stored, went into opera- PSI-West. tion in 1996. During the year under review, 2 large containers and 9 small containers with 6.5.5 Materials clearance unconditioned components were stored there. In 1998, inactive and/or uncontaminated mate- At the end of 1998, this stockyard contained rials from controlled zones in PSI with a weight 3 large containers and 23 small containers. of 86.9 tonnes (including 19.1 tonnes of steel, 23.4 tonnes of lead and 27.0 tonnes of concrete) were cleared for unconditional further 6.7 Emergency preparedness use. During the year under review, two Institute emergency exercises, under the Inspector- 6.6 Storage of radioactive ate's observation, were carried out to take account of the postponement of the 1997 exer- waste cise. 6.6.1 Federal Interim Storage Facility The Institute emergency exercise ORAWILA The federal interim storage facility (BZL) has in March corresponded to the exercise post- been in regular use for storage since the end poned from 1997. The main goals of the exer- of 1992, and now contains conditioned waste cise were to examine and use the new con- in 200 litre drums up to about one third of its cept for the PSI emergency organisation, nominal capacity. At the end of 1998, 3677 involving the emergency team, the affected treated standard drums (of 200 litres each), members of staff, the alert organisations, and packed in lots of 9 apiece, and 24 containers the internal fire brigade, together with external (of 4.5 cubic metres each) holding untreated, support. solid wastes from PSI-West were in storage at The chosen scenario was that a smoulder- the BZL facility. ing fire occurred in one hot cell during work in During the year under review, PSI prepared the isotope production laboratories at PSI- a revised safety report for the BZL and submit- West and that this led to release of smoke and ted this to the Inspectorate in December. The radioactive substances. Inspectorate will examine this report and give The Inspectorate reached the conclusion its opinion. that the PSI teams involved in the exercise had worked well.The new concept is well suited to 6.6.2 Further storage facilities at PSI-East emergency situations and permits a rapid and Storage buildings A, B and C, the stockyard and effective response, including the involvement the transfer point are used for short-term and of trained emergency personnel.The goals of medium-term storage of either treated or un- the exercise were attained. Possibilities for treated, low and medium-level active wastes. improvement were recognised, among others, The inventory in these storage areas fluctuates in the area of fire-brigade documentation greatly. The raw wastes from Swiss nuclear (building plans and the information on reliabil- plants, intended for incineration, are delivered ity and consequences of measures such as the as part-shipments and remain at the transfer electrical isolation of buildings). In connection

48 HSK Annual report 1998 • Paul Scherrer Institute (PSI) with the exercise, PSI was also required to The approvals for the release of radioactive clarify the fire-protection details in the existing substances and for direct radiation from PSI, work areas A and B in the building chosen for together with the monitoring requirements for the exercise and, if necessary, to improve these, were revised and put into operation on these in accordance with the relevant legisla- January 1, 1998. On the basis of the 1994 Ra- tion. Furthermore, it was recommended that diation Protection Ordinance, the conditions the emergency help, which was available at for this approval for the PSI site lay down a the time of the exercise only in a provisional source-related dose guideline value of 0.3 mSv way, become permanent without delay. per year and, for the release of radioactive The Institute emergency exercise 1998 substances, a dose proportion of 0.2 mSv per "EVA in PSI-East" took place in November of year. Table A4a shows the release of radioac- the year under review.The goal of the exercise tive substances for the PSI installation and the was to examine the evacuation concept from dose, calculated according to the methods of the exercise buildings within PSI-East, taking the Inspectorate's Guideline R-41, assuming a into account aspects of radiation protection. worst-case situation with regard to the most Attention was also paid to the logistic prepa- exposed person in the vicinity. For 1998, the ration in the area of security personnel, the calculation for the whole installation results in behaviour and the supervision of the people a dose of 0.003 mSv for infants and 0.004 mSv evacuated, and the co-operation with external for adults. Thus, the requirements for protec- personnel. tion of the population were adhered to. The assumed scenario was a fire, caused by During the year under review, checking of maintenance work, in the central power and the PSI personnel dosimetry department, as heating building of PSI-East, which led to sev- required every five years by the Radiation Pro- eral injured persons and to a loss of electrical tection Ordinance, became due. For this rea- power. son, an inspection of the dosimetry systems In the Inspectorate's opinion, those involved was carried out in December 1998 in the pres- in the exercise dealt well with the situation and ence of an external expert of the IRA (Institut met most of the goals of the exercise. Among de radiophysique appliquee, Lausanne) other points, possibilities for improvement charged by the Inspectorate with this task. The were identified in the evacuation area in con- renewed certification of PSI personnel dosi- nection with the work of the radiation protec- metry became applicable at the beginning of tion team. 1999.

6.8 Particular events 6.10 Personnel and For the first time since its foundation in 1988, organisation there were no notifiable events, according to The number of licensed personnel at PRO- the Inspectorate's guideline R-25, at PSI during TEUS, the only PSI research reactor still in the year under review. operation, was at its lowest level and consisted, at the end of 1998, of two reactor physicists, one reactor technician and one reactor 6.9 Radiation protection operator. One reactor physicist is being trained and will complete the licence examination in Throughout the whole of PSI in the year under 1999. review, a radiation dose of 239.5 Person-mSv The department of radiation protection and (1997: 351 Person-mSv) was accumulated: disposal ASE, formed in 1997 by combining the 1474 Person-mSv at PSI-West and 92.1 Per- areas of radiation protection, decommissioning son-mSv at PSI-East. The highest individual projects, and the PSI waste disposal depart- dose was 8.3 mSv (1997: 7.4 mSv). As in the ment, was transferred, as an organisational previous year, no new work with any significant unit, from the main research department Bio- effect on dose rate was undertaken. logical Sciences to the newly formed main During their work, the radiation protection department Logistics and Marketing. This teams of the department for radiation protec- change in organisation was carried out without tion and disposal (ASE) themselves received a the agreement of the Inspectorate with regard collective dose of 10.3 Person-mSv in 1998 to the operational requirements of radiation (1997: 18.3 Person-mSv). Further information protection. In the Inspectorate's opinion, direct about dose values can be found in Tables A5 allocation of the ASE to PSI management to A10and in Figure A6. would better reflect the importance of this department. In the course of its supervisory

HSK Annual report 1998 • Paul Scherrer Institute (PSI) 49 activities, the Inspectorate will check whether 6.11 Overall Judgement the radiation protection department retains sufficient power within the new main depart- The condition of the PSI installations and the ment to continue to guarantee the protection operational management can be rated as good goals for personnel and the environment. with regard to nuclear safety and radiation pro- Within the radiation protection department tection. In the evaluation of the operation of ASE, the personnel situation is unsatisfactory those installations supervised by the inspec- with regard to the number of radiation protec- torate, there was, for the first time since foun- tion specialists. The Inspectorate has pointed dation of the PSI in 1988, no notifiable event. out bottlenecks and expects that the number However, the nuclear installations still oper- of personnel allocated to radiation protection ated at PSI, and the other areas and equipment will be increased. In the opinion of the Inspec- subject to radiation protection legislation, de- torate, a further personnel bottleneck exists in mand a high standard of safety awareness the area of disposal activities, and this will in- from management, from direct supervisors crease during 1999 if some of the ZWILAG and from the operating staff. In the Inspector- personnel are no longer available to PSI, as has ate's opinion, this high standard is not present been planned contractually. The Inspectorate convincingly in all areas. will therefore act here according to the basic Due to the staff and financial shortages in principle that work which involves the creation those organisational units important to safety, of radioactive waste may only be begun if the and their allocation to the main department treatment, conditioning and interim storage of "Logistics and Marketing" in the PSI organisa- this waste is guaranteed, both from the point tional chart, a decrease in the importance of of view of material and personnel. radiation protection could easily occur. The In- In the course of the reorganisation carried spectorate could not tolerate such a change out in October 1998, the departments Proton and has thus established, and will continue to Accelerator, Experimental Installations and prescribe, relevant requirements in connection Spallation Neutron Source were combined to with approvals and project releases. form a main department "Large Research In- stallations", together with the technical service units directly associated with them. In this context, the Inspectorate expects closer co- operation between the management of the installations.

50 HSK Annual report 1998 • Paul Scherrer Institute (PS!) 7 Other Nuclear Installations

7.1 Ecole Polytechnique school at PSI (see also 14.1) and the HTL technical college in Brugg-Windisch use the Basle Federate de Lausanne facility for much of their reactor practical work. (EPFL) Employees of the cantonal laboratory Basle- The Institute de Genie Atomique (IGA) oper- Land also took part in a training session which ates three nuclear installations at the Swiss involved operation of the reactor. During the Federal Technical University (EPFL) in year under review, the reactor was in operation Ecublens, near Lausanne: the research reactor for 46.3 hours.This meant that only about 1 % CROCUS, and the neutron sources LOTUS and of the authorised weekly limit of 30 kWh was CARROUSEL. The research reactor CROCUS used. was in operation for 390 hours during 1998 for Operation of the Basle nuclear installation practical training {reactor physics) for students was trouble-free and there were no notifiable of the EPFL and of the engineering school of events according to the Inspectorate's Guide- Geneva (EIG).The PSI reactor school (see also line R-25.The collective dose for the four reac- Section 14.1) used the installation for practical tor staff was 0.0 Person-mSv in 1998. work on the subject of reactor kinetics. During the year under review, 166 Wh of thermal energy were produced. 7.3 Experimental reactor at The arrangement with a neutron source surrounded by a moderator (CARROUSEL) is used Lucens (VAKL) by students for the preparation of practical Since the formal decision by the Federal Coun- work on reactor physics. The LOTUS plant, a cil on 12 April 1995, the site of the former ex- subcritical 14 MeV neutron source powered by perimental reactor at Lucens (VAKL), with its an accelerator, was not operated in 1998. underground and above-ground buildings, is no The operation of the installation, and of the longer subject to atomic law and now belongs type B laboratory area, took place without to the canton of Waadt.The inauguration of the problems and without notifiable events accord- converted plant, which is now used by the can- ing to the Inspectorate's Guideline R-25. One ton for the storage of objects of cultural and ar- part of the controlled zone (IFUAS hall), which chaeological interest, took place already in is now being used for experiments without 1997. radiation, could be de-classified and is now Since the site of the Lucens experimental accessible without restrictions since this reactor is no longer a nuclear installation ac- change. The collective dose for the 10 persons cording to atomic law, the Inspectorate has working on the nuclear installations at the In- been relieved of its supervisory responsibili- stitute was 0.4 Person-mSv in the year under ties. However, the Federal Council has in- review. Releases, including tritium, via the at- structed the Section for Radiation Monitoring, mosphere and waste water were insignificant Freiburg (SUeR), to carry out further radiologi- during this period. cal monitoring of the site during the next 30 years. The SUeR is, of course, responsible for the surveillance of environmental radioactivity 7.2 University of Basle in the whole of Switzerland. A small area of the Lucens installation, on In 1998, the small research reactor of type which six steel containers with radioactive AGN-211-P in the basement of the physics fac- waste from the shutdown and dismantled re- ulty at the University of Basle was used, as actor are stored, continues to be a nuclear in- intended, for teaching purposes (radiophysics stallation in a special sense. It belongs to the practicals). In addition to the tasks carried out national association for the industrial promo- internally for the university, irradiation work tion of nuclear technology (NGA).These waste was performed for the cantonal laboratory containers remain under the surveillance of Basle-Stadt. In Switzerland, there are only two the Inspectorate. The waste containers are to small plants (this one and CROCUS) available remain at the Lucens site until they can be for training. For this reason, both the reactor transferred to the central interim storage facil-

HSK Annual report 1998 • Other Nuclear Installations 51 ity (ZZL) of ZWILAG in Wurenlingen (see also Chapter 5), which is nearing completion. During the year under review, no events of a radiological or safety-related nature occurred at the site of the earlier experimental reactor, in 1998, the only remaining member of the surveillance group still registered as being occupationally exposed to radiation accumulated a dose of 0.9 mSv during inspection tours.

52 HSK Annual report 1998 • Other Nuclear Installations 8. Disposal of radioactive waste

8.1 Wellenberg repository project would have a positive effect on the region and proposed a new allocation scheme for The procedure for a general license, which had payment for the public services which would been initiated on June 29, 1994 for a reposi- have to be provided. tory for low and intermediate level wastes The project modifications, mentioned (SMA) at Wellenberg in the canton of Nidwal- above, are described in the Nagra technical den, was suspended on June 4 by a decree report NTB 98-04, dated October 1998. from the Federal Department for Environment, Transport, Energy and Communication (UVEK). The realisation of the project is blocked due to the refusal, in 1995, of the canton of Nidwal- den to provide a necessary concession to the project applicant, "Genossenschaftfurdie Nu- kleare Entsorgung Wellenberg" (GNW). In June 1996, in the course of the review of the project, the Inspectorate came to the conclusion that, according to existing information, the chances were good that the Wellenberg site would be suitable for constructing such a repository, taking into account the need to protect the population and the environment. The review report empha- sised that an underground exploration tunnel is necessary to confirm this prospect. Positive results from investigations in this exploration tunnel are also a pre-condition for resumption The geological layer "opalinus clay" derives its name from the approximately 179 million year old ammonite of the procedure for a general license. fossil "Leioceras opalinum " found at a depth of 652 m At the request of UVEK, the Federal Office during a Nagra test drilling in Benken. of Energy (BFE) established working groups of Source: Comet, Zurich; Nagra, Wettingen the Swiss Federation and the cantons of Nidwalden and Obwalden in order to clarify various questions associated with the project. 8.2 Repository for high-level These working groups were: the Technical Working Group Wellenberg, the Economic waste: preparatory meas- Working Group Wellenberg and a steering ures committee, which published the final reports In accordance with the decision of the Federal of the working groups on September 17,1998. Council on the "Gewahr" project, research The technical working group, in which the In- activities for demonstration of the feasibility of spectorate participated, confirmed the prob- disposal were continued with regard to the able suitability of the site for a SMA repository, disposal of high-level and long-lived intermedi- but recommended that the further investiga- ate-level waste. In this context, Nagra is carry- tions be carried out in various stages. In the ing out basic work on the two host rock forma- first stage, an exploratory tunnel should be tions: the crystalline basement and the built. A decision on construction of the reposi- opalinus clay. tory should only be reached after the results During January and February 1998, Nagra from the exploratory tunnel investigations be- filled in the exploratory crystalline borehole come available. The working group acknowl- situated at Riniken, in which the measurement edged positively the changes to the project programme had been finished. The Inspector- proposed by the GNW, which take more ac- ate supervised this work and was able to sat- count of the current desire to provide for moni- isfy itself that the f illing-in work was carried out toring and retrieval of the waste. The economic in a technically correct manner and in accord- working group came to the conclusion that the ance with the permit given in 1997. The Riniken

HSK Annual report 1998 • Disposal of radioactive waste 53 Volumetric aspect of the geological layers in the Zurich Weinland created with help from 3-dimensional seismic data. The cut-out shows the most remark- able disturbance in the area where the opalinus clay displaces the bedrock by about 12 m. Source: Nagra, Wettingen

surveillance commission met for the last time within the opalinus clay host rock. The Inspec- in December 1998 and adopted its final report torate followed the scientific aspects of these concerning the filiing-in. The commission's preparatory measures. In order to co-ordinate work was thus finished. Final reports on filling- the supervisory activities of the various au- in of the Schafisheimand Siblingen boreholes, thorities, the Federal Council has established which was carried out in 1997, were also pre- a co-ordinating commission which is chaired by pared and will be adopted in 1999. The filling- the Inspectorate. During the year under re- in work at both of these sites also proceeded view, this commission met on four occasions. without problems. Long-term observations will Nagra has pushed ahead with geological continue at the four remaining, crystalline interpretation of the seismic reflection record- boreholes as long as the systems are still in- ings carried out in the Zurich Weinland area. tact. In October, the annual common meeting The results obtained are of excellent quality of the relevant surveillance commissions was and allow a detailed geological characterisation carried out under the chairmanship of the In- of the investigated area. spectorate. The experimental programmes were contin- Since the Leuggern/Bottstein site is no ued at the rock laboratories. In the Grimsel rock longer of immediate interest for further crys- laboratory, in which crystalline rock is tested, talline boreholes, the Federal Council ap- eight new experiments belonging to the inves- proved, on February 11, 1998, the Nagra appli- tigation phase 5 were started under the partici- cation to suspend the licensing procedure for pation of twelve partners from eight countries. exploratory boreholes at this site. In June, af- A new cavern was excavated for the gas migra- ter completion of field work in the region of the tion test (GMT) in the engineered barrier sys- Mettauer valley (canton of Aargau) and assess- tem. The Inspectorate followed the Nagra work ment of the results, Nagra decided not to sub- and carried out on-site inspections. mit further applications for exploratory bore- At the MontTerri rock laboratory in the can- holes in the crystalline basement in the near ton of Jura, which is located in opalinus clay, future. Instead, it intends to shift the empha- phase 3 of the investigations was continued sis of field work, in the near future, to explora- and preparations were made for experiments tion of the opalinus clay in the Zurich Weinland of the phase 4. The main focus of work at the area. beginning of the year was the excavation of the After receipt, in spring, of the legally valid new exploratory tunnel, which involved numer- construction permit, Nagra was able to start ous experiments. 36 boreholes were made in work at the Benken borehole site in the can- the opalinus clay in connection with the newly ton of Zurich. The exploratory work itself was planned experiments. The Inspectorate fol- started on September 3, 1998 and proceeded lowed the work at MontTerri.The new explora- according to plan; at the end of the year the tory tunnel was presented to the public on borehole had reached a depth of 623 metres September 17, 1998.

54 HSK Annual leport 1998 • Disposal of radioactive waste 9. Transport of Radioactive Materials

I After loading on the railway wagon, the transport I container for spent fuel el ernents is again carefully measured and protocolled.

9 1 Permits and approvals materials of class 7 will be modified on the according to transport ^ of ST"1 and wi"probably go int0 force in legislation jhe main responsibility for complying with The Swiss regulations governing the transport the transport regulations, and for radiological of radioactive materials are based, inter alia, on safety, lies with the consignor. In the case of international legislation for the transport of the transport of nuclear fuel, or other highly hazardous materials. The IAEA recommenda- radioactive materials, regulations demand that tions (SS6)1 for the safe transport of radio- the consignor obtain, in advance, a permit or active materials apply to all modes of transpor- approval certificate from the competent au- tation. The SS6, together with further thority. The permits or approval certificates international codes was brought up to date refer, according to the case concerned, to the with regard to the current state of scientific package and/or to the shipment, and technical knowledge and has been pub- The Inspectorate is the competent Swiss lished, in the meantime, by the IAEA as ST-12. authority in charge of issuing such permits and The legislation for the transport of hazardous approval certificates according to transport legislation, irrespective of whether they concern M^Zsafety-Series 6: Regulations for the SafeTransport the transport of radioactive materials from of Radioactive Material, 1985 Edition (asamended 1990) nuclear power plants or from other installa- ' IAEASAFETYSTANDARDS SERIES ST-1: Regulations for tions- ln the case of Package approvals, the the SafeTransport of Radioactive Material, 1996 Inspectorate relies, in most cases, upon the

HSK Annual report 1998 • Transport of Radioactive Materials 55 certificates issued by the competent authority moval of nuclear fuel. Apart from insignificant of the country of origin. In all cases, the Inspec- deviations, no cases were found in which the torate verifies, beforehand, that packaging and transport regulations had not been adhered to. contents comply with the specifications. During the year under review, the Inspector- ate assessed 51 applications concerning ship- 9.4 Training and information ments or packages. In October 1998, the 8th course was held for plant employees responsible for the dispatch 9.2 Authorisations according of radioactive materials in their installations. The five-day course was held at the PSl school to radiation protection for radiation protection, whereby the Inspector- ate participated by the provision of instructors. According to Article 2 of the radiation protec- On January 1, 2000 the EU guideline 96/35/ tion law of March 22,1991, the transportation EG will go into force. Among other things, this of radioactive materials is an activity subject to guideline requires each firm transporting haz- authorisation. The conditions for granting such ardous materials, including class 7 (radioactive an authorisation are laid down in the radiation materials), to have available a trained respon- protection law and in the radiation protection sible person for hazardous materials. Switzer- ordinance of June 22, 1994. The Federal Office land has decided to implement this guideline of Energy has delegated responsibility for the to a large extent and will also be training spe- issue of such authorisations related to nuclear cialists for hazardous materials.The Inspector- installations to the Inspectorate. No applica- ate is participating in the preparation of a cor- tions were made and, correspondingly, no such responding training guideline for Switzerland. authorisations were issued in 1998.

9.5 Contamination associated 9=3 inspections and audits with the transport of To ensure the safety of transport workers and spent fuel of the general public, any shipment of radioac- On April 29, 1998, the French nuclear safety tive materials must comply with the relevant authority (Direction de la surete des installa- regulations. Quality assurance programmes tions nucleates, DSIN) informed the Inspector- are intended to ensure compliance with regu- ate, by telephone, that contamination of trans- lations. Quality assurance covers the plans and port casks and railway wagons had often been the procedures of packaging designers and detected during the last few years at the manufacturers, consignors, carriers and the French transfer railyard in Valognes in the competent authorities, in order to achieve course of delivery of spent fuel assemblies for compliance with the regulations. reprocessing at COGEMA in La Hague. Mainly The quality assurance programmes of all shipments of spent fuel from French nuclear Swiss nuclear power plants, and of PSl, for the power plants were affected, but shipments transport of radioactive materials have been from German and Swiss nuclear power plants approved by the Inspectorate on the basis of had also been involved. DSIN confirmed this the inspections and checks carried out. In or- information by fax on April 30: the contamina- 2 der to maintain this approval, audits are carried tion limit of 4 Bq/cm according to the transport out at regular intervals in these nuclear instal- regulations had been exceeded, in part by a lations. During the year under review, no such considerable amount, during 1997 with six audits took place. shipments from Switzerland. In 1998, one As a result of the contamination found in Swiss shipment was involved. connection with spent fuel shipments to re- The international transport regulations state processing plants (see Section 9.5), the Fed- that the non-fixed contamination on the exter- eral Office of Energy suspended all authorisa- nal surface of a package shall not exceed the tions for the transport and export of spent fuel value of 4 Bq/cm2 for p/y activity. This is, how- assemblies on May 8, 1998. The transport of ever, a derived limit. In contrast to primary lim- other radioactive materials and, in particular, its for radiation doses, negative effects on hu- the delivery of new fuel assemblies to the man health do not necessarily result from nuclear power plants are not affected by this exceeding derived limits. For this reason, the decree. In 1998, 8 inspections were performed Swiss radiation protection legislation - in con- in the Leibstadt and Beznau nuclear power trast to the international transport regulations plants, and at PSl, during the delivery or re-

56 HSKAnnua! report 1998 • Transport of Radioactive Materials - defines guiding values rather than limits for October 1998, 151 persons were measured at contamination. PSI for incorporation. There were no findings. On May 1, 1998, the Inspectorate informed Furthermore, it was agreed that, in future, all the public that cases of contamination had Swiss railway personnel directly involved in the been detected in connection with the trans- transport of spent fuel would be measured, at port of spent fuel. In its media bulletin, the In- PSI, for incorporation twice per year. In addi- spectorate indicated that no radiological dan- tion, a radiation protection expert would ac- ger had existed either for personnel or for the company such shipments in Switzerland general public. It stated that the causes of throughout one year and determine the dose contamination had to be established. The received by the personnel. cause of contamination was not due to leakage A transport cask, intended for the shipment from the transport casks since these had been of spent fuel for reprocessing at COGEMA, found to be leak-tight. On the other hand, both was delivered to the Leibstadt nuclear power the casks and the wagons had always been plant at the beginning of May and returned checked for no contamination before leaving unloaded at the end of July. The return ship- the Swiss nuclear power plants. ment of the empty cask gave the plant opera- On May 8, 1998, the Federal Office of En- tor and the Inspectorate the opportunity to test ergy suspended all existing authorisations for a new, extensive, measurement procedure to the transport and export of spent fuel assem- provide proof of freedom from contamination. blies because of the existence of open ques- Representatives from the Swiss railways, the tions, in particular with regard to the causes of Swiss railway and transport personnel union contamination, and indicated that it would not and the Aargau cantonal police participated in issue such authorisations until further notice. this pilot experiment. Since the contamination problem appeared to At the suggestion of the German and French be of a generic nature, the suspension affected governments, an international working group all transports of spent fuel assemblies, i.e. of competent regulatory authorities was estab- both by rail and by road, and both to COGEMA lished with participation of Switzerland (the in La Hague (F) and to BNFL in Sellafield (GB). Inspectorate) and the United Kingdom to co- The Inspectorate's initial investigations re- ordinate the clarification of the causes of con- vealed that excessive contamination had occa- tamination of spent fuel transports and the sionally been detected upon the delivery of establishment of remedial actions. At the 5th empty casks to Swiss nuclear power plants. In meeting of this working group in October accordance with the transport regulations, this 1998, the conclusions of the common report contamination had always been removed be- were agreed upon and the report was pub- fore the cask was loaded and shipped. Follow- lished in November. In this report, the events, ing technical discussions with the power plant their causes and their effects are described on operators, the Inspectorate laid down, in a let- the basis of contributions from the individual ter dated June 8, 1998, the conditions to be countries. Furthermore, those remedial actions fulfilled for the resumption of transportation: already introduced, or being considered are Spent fuel transports can only be started again presented and recommendations are given for when the causes of the contamination are future activities. In particular, it was decided to established and measures to prevent contami- set up an international transportation database nation introduced. The plant operators were and to establish a group of experts for meas- required to describe both causes and remedial urement procedures. The intensified interna- measures in a report to be submitted to the tional exchange of information is judged as Inspectorate. Furthermore, additions to the suitable in order to improve supervision of notification requirements were established in transportation and information for the public. order to improve the exchange of information. The common opinion of the working group of At the beginning of May 1998, the Inspec- regulators of the four countries is that the torate measured the dose rate on the tracks of measures reported in the report allow safe the Muttenz railway station, where the loaded spent fuel transportation. railway wagons always stand. No increase in On August 21, 1998, the nuclear power the dose rate above the natural background plant operators presented and submitted to level was measured. In order to determine the Inspectorate the required reports describ- whether railway employees, who had been ing the causes of contamination and the meas- involved in transport of spent fuel, had incor- ures to prevent this. After thorough examina- porated radioactivity, the Inspectorate intro- tion, the Inspectorate gave its opinion on these duced a campaign for whole body monitoring, reports on October 19, 1998: an extensive in co-operation with the management of the amount of data had been collated, but the Swiss railways company. Between June and causes had not been definitively established

HSK Annual report 1998 • Transport of Radioactive Materials 57 and the remedial measures described were subjected to more thorough cleaning and ex- neither comprehensive nor concrete enough. tensive measurement programmes will be The Inspectorate thus demanded correspond- carried out to demonstrate freedom from con- ing additions and clarifications. tamination.The quality assurance programmes The answers to these requirements were of the nuclear power plant operators will be discussed at a meeting between the nuclear supplemented by these additional steps in power plant operators and the Inspectorate on work procedures. Furthermore, the operators December 18, 1998. The cause of contamina- will improve the awareness of their responsi- tion is now established: it arises from contami- bility as owners and consignors of the spent nated water from the fuel pool, in which the fuel assemblies. transport casks are immersed for loading. The operators submitted the report, modi- Despite their surfaces being covered, small fied to take account of the Inspectorate's ques- amounts of water can penetrate into the sur- tions, in January 1999. For its part, the Inspec- face roughness on the casks during this proc- torate described its assessment, in particular ess and be released later during transporta- of the remedial measures, in a report to the tion. In order to prevent the occurrence of Federal Office of Energy in March 1999. This unallowable contamination in future, improve- report will serve as the basis for a decision ments will be made to the way in which the upon the subsequent ending of the suspen- transport casks are covered for immersion in sion of transport authorisations. the fuel pool. Furthermore, the casks will be

58 HSK Annual report 1998 • Transport of Radioactive Materials 10. Emergency Preparedness

10.1 The Inspectorate's emer- - the Aargau and Solothum cantons - the Steering Committee for Radioactivity gency organisation (LAR) The Inspectorate's emergency organisation The scenario for this exercise was that a leak ensured its emergency preparedness by carry- had occurred in the primary circuit. Initially, the ing out staff training and an internal exercise, emphasis was on the way in which the plant by participation in a basic course "emergency dealt with the incident. After a certain period protection in nuclear power plants", by use of of time, the KKG emergency team was able to the relevant infrastructure in the context of the return the plant to a safe condition. Subse- overall emergency exercise "GAIA", and by quent damage to the reactor core, with the emergency exercises at the plants. During the release of radioactive materials into the envi- year under review, the infrastructure of the ronment, was assumed in order to give also Inspectorate's protected emergency bunker the external emergency organisations the op- GENORA was temporarily extended (e.g. in- portunity to practice. In this second phase, the stallations for video conferencing during the emphasis was on the establishment of meas- GAIA exercise) and adapted to the new re- ures for the protection of the population. quirements. For the first time, the most important data The Inspectorate's picket team consisted of from the plant, as well as the data on the re- 13 shift technical advisors, whereby the engi- lease of radioactivity into the environment, neer on duty was available round the clock. The was simulated through use of the MADUK- mustered members of the emergency organi- ANPA system. In order to ensure timely and sation were, in all cases, available in the In- mutual information of the authorities, the as- spectorate's emergency rooms within less sessments and decisions of the emergency than one hour after being summoned. The In- organisations were made available in a current- spectorate's picket team was mustered 13 situation report on an Internet web site. In this times as a result of notifiable events. The re- way, all involved organisations were rapidly sponsibility for notification is governed by the aware what decisions had been taken and Inspectorate's Guidelines R-15 and R-25. which protective measures had already been decided upon and carried out. A main focus of the exercise was the way in which information 10.2 Planning for protection was passed on to the general public. In this context, it became apparent that a press cen- in the case of emergen- tre should be established at the earliest oppor- cies tunity in the case of an accident in a nuclear 10.2.1 Overall emergency exercise GAIA power plant, in order to ensure co-ordination together with the Gosgen nuclear of the information distributed to the media and power plant to the public. On November 11, 1998, an overall emergency exercise, chaired by the Federal Committee for 10.2.2 Emergency protection concept 1998 Radiological and Chemical Protection (KOMAC), In March, the "concept for emergency protec- was carried out together with the Gosgen nu- tion in the vicinity of nuclear power plants", clear power plant. Such exercises, which take which had been revised under participation of place every two years are intended to practice the Inspectorate, the National Emergency and check out the co-operation between all Operation Centre and the Swiss Federal Nu- parts of the emergency organisation in the clear Safety Commission, was published by case of increased radioactivity. For GAIA, in the Federal Committee for Radiological and addition to the Gosgen nuclear power plant, Chemical Protection (KOMAC). On the one the following organisations were involved: hand, this takes account of newer measures - the Inspectorate of a legal nature (ordinance concerning iodine - National Emergency Operation Centre, tablets) and, on the other hand, it incorporates Zurich (NAZ/CENAL) the lessons learned from the emergency exer- - Federal Office of Energy, Bern (BFE/OFEN) cises carried out to date.

HSK Annual report 1998 • Emergency Preparedness 59 The cantons, which are responsible for four nuclear power plants, were broadcast via putting into practice the protective measures the teletext page 652 on the national television for the general public, are involved to a greater service for the German, French and Italian extent in the new concept. They must be in a speaking areas of Switzerland. position to order, directly, that protective meas- Increases, which were not due to heavy rain ures for the general public be carried out in the and associated deposits of the natural daugh- case of a nuclear event in which a danger to ter nuclides of radon, were registered in the the public quickly becomes apparent. A further, values measured by individual probes in a to- new measure, in the case of an accident, is tal of nine cases during 1998. In five of these that a contact point should be established for cases, these increases were found to be due medical and psychological advice to the gen- to functional tests of nearby NADAM probes. eral public. In four cases individual, clearly increased dose In addition to its participation with this con- rate values were measured. The Inspectorate cept, the Inspectorate also took part in various investigated each event extensively, although KOMAC working groups concerned with the increases were insignificant from a radio- putting into practice emergency protective logical point of view. In one case, it was dem- measures. onstrated by means of immediate repeat measurements that the probe was subject to malfunction. In three cases, well-known distur- 10.3 Training activities in the bance patterns relating to defective probes occurred and the probes were therefore re- area of emergency pro- placed. tection In summary, it can be concluded that the In 1998, in the area of emergency protection, probes in the vicinity of the nuclear power a total of 22 external training courses were plants showed high availability, and that no in- held, including participation in federal or can- creases in the measured data were apparent tonal training events. The central focus of the as a result of releases from these plants. training was the new concept for emergency protection in the case of increased radioactiv- 10.4.2 Plant data from ANPA and their use ity in the vicinity of the Swiss nuclear power Plant parameters from each of the five Swiss plants, as finalised by KOMAC in March. De- nuclear power plant units can be accessed by pending upon the qualifications of course par- the Inspectorate, as required, via the ANPA ticipants, the training in the emergency protec- system. In the case of an incident at a plant, tion concept was supplemented by lectures on the Inspectorate can receive and then display radiation protection and on the basic way in up to 25 relevant, key plant parameters, up- which nuclear power plants function. dated every two minutes, using ANPA. In the event of mobilisation, the emergency staff team has available the appropriate means to be 10.4 MADUK and ANPA kept rapidly informed about the nature and progress of the incident. ANPA was accessed 10.4.1 Measuring network for automatic in 1998 during an Inspectorate picket activity; dose-rate surveillance in the vicin- further access connections took place in the ity of nuclear power plants context of testing and for emergency exer- (MADUK) cises. During the year under review, the MADUK sys- The ADAM system (Accident Diagnostics, tem exhibited very high availability. Thanks to Analysis and Management), now being devel- the storage of measured values at the probes, oped, will provide the Inspectorate emergency only less than 0.1 % of measured data could organisation with support in interpretation of not be assessed as a result of disturbances or the ANPA data and indicate how the accident maintenance work at the probes. This result is developing and what its consequences may was achieved despite two complex, malfunc- be. ADAM uses simplified, plant-specific mod- tions of data transfer between the MADUK els and can determine the current plant status probes and the Inspectorate in the first quar- using the ANPA data. Based on plant-specific ter of the year. The MADUK station at the Stilli computer models for thermohydraulics, multi- sewage plant was out of operation from Feb- phase flow, heat transfer, hydrogen combus- ruary 10 to October 14, 1998, due to recon- tion, etc., the computer programme calculates struction work at the probe site. the course of an accident up to 100 times Each day, the daily average dose rates, from faster than a real-life accident would be ex- the previous day, measured by four, chosen pected to progress, thus allowing a prognosis MADUK probes in the vicinity of each of the to be given. The ADAM model, developed for

60 HSK Annual report 1998 • Emergency Preparedness KKG, was tested in 1998 and used successfully ured data in a location-specific way. The WIND- by the Inspectorate's emergency organisation BANK information, collated into databases, during the overall emergency exercise GAIA. In establishes the limits of the affected area in subsequent years, ADAM programmes will be the case of an incident and is part of the input developed for the plants, KKB and KKM. data for the ADPIC computer programme discussed below.

10.5 Basis for atmospheric 10-5-2 Calculation of the dispersion of dispersion calculations The ^Z^^Z^ZZn^ 10.5.1 Determination of wind fields using prompt assessment of possible radiological WINDBANK dangers to the public in the immediate vicin- The wind fields for zones one and two in the ity of the plant for the case of release of radio- vicinity of the Muhleberg, Beznau and Leib- active materials from a Swiss nuclear power stadt nuclear power plants, as well as PSI, plant due to an incident. In the case of an inci- were recorded by means of the permanent dent, the American dispersion model ADPIC measuring stations and those temporarily es- (Atmospheric Diffusion Particle-ln-Cell model), tablished in the area. Three-dimensional wind- which takes account of topography and three- field classes will be produced from the meas-

A timely judgement on the radiological danger to the population is made possible by ADPIC using updated meteorological data. The development with time of the near ground-level integrated air activity, during the fictive release of radioactive materials, is illustrated. (Source: HSK, vniigeni.

HSK Annual report 1998 • Emergency Preparedness 61 dimensional wind fields, will be used in addi- 10.6 Social aspects in con- tion to the MADUK dispersion calculation. nection with decision- In 1998, the ADPIC dispersion model, developed by the Lawrence Livermore National making following an Laboratory, was further adapted to Swiss con- accident ditions. The main goal here is to ensure the availability of ADPIC for real-time use in the In addition to technical, commercial or political vicinity of the Swiss nuclear power plants in considerations, those who have to decide the case of an emergency. A major part of the upon, or order, measures for the general pub- work concerns the on-line recording and auto- lic in the context of an accident in a nuclear matic use of current meteorological data, as power plant should take into account social, well as use of the measured wind fields from cultural and psychological aspects. This has the WINDBANK project. been recognised increasingly over the last few The three-dimensional wind-field classes for years world-wide. In January 1998, the Nuclear the Lower Aare Valley, determined in the Energy Agency (NEA), together with the In- WINDBANK project, were integrated into a spectorate, organised a three-day workshop wind-field database and can now be used for on this topic in Villigen, Switzerland. Experts dispersion calculations at any time.These wind from throughout the world took part in this fields are available, with various, localised reso- seminar and discussed in detail the multifari- lution levels, for the PSI, Beznau and Leibstadt ous aspects of situations following an accident. locations up to a maximum down-wind dis- The experience gained in re-locating the tance of 32 km. The selection of the correct population away from contaminated areas, as, wind-field class and the associated parameters e.g., with the Marshall Islands (1954) and Cher- takes place automatically on the basis of nobyl (1986), shows that the rapid, authorita- current meteorological data. In this way, suc- tive decision-making initially required must be cessful use of ADPIC, together with the WIND- replaced in a later phase by decisions which BANK methodology, was able to be demon- allow democratic participation of the people strated at the end of 1998. In 1999, it is affected. Furthermore, this experience shows intended that specific, local, turbulence infor- that the radiation dose cannot be the sole cri- mation should be determined from the meas- terion for the orders given. In particular, it was ured meteorological data and transformed into established that there is a large discrepancy, corresponding parameter values for ADPIC. initially, between the actual risk and the risk Appropriate pictorial representation of the which is regarded by the public as acceptable. results is very important in the case of an In the course of the workshop, it became event, in order to permit rapid interpretation of apparent that the role of the decision-makers the numerous data obtained. For this purpose, must be newly defined internationally with a menu-driven, graphic interface was devel- regard to the consideration of social and psy- oped for visualisation of ADPIC results. Further chological aspects. optimisation is planned with regard to user- friendliness.

62 HSK Annual report 1998 • Emergency Preparedness 11. Regulatory inspections

] An inspector of the Swiss \ Federal Nuclear Safety In- < spectorate (HSK) at work | in the nuclear power plant Beznau. i

11.1 General aspects COn- panied inspectors from the Inspectorate dur- cernina reaulatorv in9 their work in Swiss nuclear power plants cerning regu a y gnd vice versa |n previ0us years, common in- inspections spections had also been carried out with the The Inspectorate supervises the nuclear regulatory authorities in the German state of power plants and PSI, as well as part of the Baden Wurttemberg. transportation of radioactive materials, on be- On the basis of this information, the Inspec- half of the Swiss Federation. Regulatory in- torate has determined that it can optimise its spections are of essential importance in ena- inspections by means of improved procedures bling the Inspectorate to carry out this in the areas of: supervisory responsibility. Both the informs- - planning (the regulatory inspection pro- tion obtained from international contacts, and gramme); its own experience, have led the Inspectorate - formal preparation and subsequent evalua- to revise the way in which its inspections are tion (check-lists); carried out. In February and in June 1998, a - communication with the plants (regulatory seminar on the theme of regulatory inspec- inspection report); tions was held in this context and attended, in - an interdisciplinary procedure (team inspec- each case, by approximately 30 members of tions). the Inspectorate staff. The main focus of the In 1998, the Inspectorate's internal work in- lectures and group work lay on general aspects struction W-17, entitled " Procedures for inspec- of carrying out regulatory inspections and on tion activities of the Inspectorate", was revised, safety culture. and made more precise, in the context of the For the first time, during the year under re- above-mentioned optimisation. In this way, it view, so-called "Inspections Croisees" were can be ensured that all Inspectorate staff fol- also carried out, i.e. French inspectors accom- low uniform and co-ordinated procedures dur-

HSK Annual report 1998 • Regulatory inspections 63 ing regulatory inspections.The topics governed the case especially for earthquakes, fires and by the work instruction are planning, prepara- flooding, but may also apply to incidents such tion, performance and documentation of the as aeroplane crashes, gas explosions, turbine inspections themselves, as well as checks on failures, or extreme weather conditions. As a the way in which discrepancies revealed by the rule, a three to five day visit to the plant forms inspections, or requirements made, have been the core activity of the PSA regulatory inspec- dealt with.The experience to date has shown tion. This is carried out by four to eight mem- that further additions, including tighter speci- bers of the Inspectorate staff, from various fication, are required in the context of this work departments, together with one or two exter- instruction. This revision should contribute to nal PSA experts. the establishment of even more balanced and In preparation for the works visit, the Inspec- traceable procedures during the Inspectorate's torate forms a first impression on the extent inspections. Furthermore, the regulatory in- and quality of the relevant part of the PSA spection concept should be more clearly de- study on the basis of the PSA documentation fined, whereby a balanced distribution will be and associated paperwork.The comments re- established between routine inspections, risk- sulting from this are listed in a preliminary regu- based inspections, and inspections on the ba- latory inspection report, which is supple- sis of operational experience. mented by a list of questions and additional As a rule, the plant operator is informed be- pieces of information required. Furthermore, forehand when regulatory inspections will be the procedures and goals of the visit are de- carried out. However, they can also take place scribed, and the preparatory work to be carried without advance warning. The inspection ac- out by the plant is specified. tivities of the Inspectorate do not affect the The Inspectorate has several goals during fact that full responsibility for safe operation of the visit, which is documented with the aid of the plant lies with the plant operator. check-lists, notes, photographs and, in part, In the year under review, interdisciplinary with video records. For example, it is ascer- regulatory inspections, i.e. those involving dif- tained whether the plant-internal walk-downs, ferent technical departments of the Inspector- necessary for the preparation of the PSA ate, were carried out in a systematic way. It study, have been carried out and documented became apparent that such "team inspec- in the appropriate way, and whether all parts tions" permit a more balanced impression to of the plant involving possible risks have been be obtained of the way in which procedures correctly included. Furthermore, all safety-rel- are adhered to in the plants. In future, the In- evant components are inspected with regard spectorate will place greater emphasis on to their ability to function under the assumed team inspections. accident conditions. Of interest in this context, During the year under review, the Inspector- among other things, are the fitness-for-pur- ate carried out 519 regulatory inspections and pose of anchoring points and the correct instal- technical meetings in the nuclear power plants. lation of these, or how the interactions be- In the following, the way in which the Inspec- tween different parts of the plant can be torate carries out, and evaluates, regulatory influenced, e.g., by vibrations, smoke and inspections will be illustrated on the basis of fumes, or by flood-water. During the visit, it is examples chosen from 3 areas. also ascertained whether those weak-points in the plant, which were identified in the PSA study as being easily remedied, had, in fact, been dealt with. Last but not least, the walk- 11.2 Regulatory inspections downs are used to carry out a general visual in connection with the inspection of the plant and its vicinity, whereby examination of proba- attention is paid, e.g., to cleanliness and tidi- bilistic safety analyses ness (housekeeping problems). Technical discussions are also carried out with staff from The Inspectorate has an important role to play the nuclear power plant in the course of the in the examination of a plant-specific, proba- visit. These discussions are used to examine bilistic safety analysis (PSA study). In particu- additional documentation relating to the PSA lar, the Inspectorate uses the PSA regulatory and to the plant, to discuss open questions inspection to determine whether the assump- and, finally, to present the results of the visit tions made in the PSA study are in accord with to the plant personnel. the actual situation in the plant.This is particu- Following the visit to the plant, the results larly important in dealing with accident sce- of the walk-down, together with an up-dated narios initiated by events which can affect sev- list of questions, are provided to the plant. Af- eral parts of the plant simultaneously. This is ter the plant has answered these questions,

64 HSK. Annual report 1998 • Regulatory inspections the Inspectorate completes the regulatory in- 11.3.3 Observations and results spection report and derives from this the ap- The blowdown line was inspected over its propriate requirements relating to the PSA whole length on August 12, 1998, whereby the study and the plant itself. Inspectorate was accompanied by a member of the plant staff. No deviations from the con- 11.3 Unannounced technical dition of the other three blowdown lines, which had not been affected by the incident, were regulatory inspection as identified. In particular, no displacements, a consequence of an bends, dents or changes in surface colour event at the Miihleberg were discovered.The inspected blowdown line nuclear power plant was not damaged during the incident and can thus continue, in future, to fulfil its function to (KKM) the complete extent. In the course of the regu- 11.3.1 Reason for and goal of the Inspec- latory inspection, the Inspectorate was able to torate's regulatory inspection ascertain that KKM had already carried out an Event number 98-1 at KKM, which occurred on examination of the blowdown line on its own June 23, 1998 and has already been described accord. in Section 2.2.1, involved the erroneous open- The plant operator had brought forward by ing of the blowdown valve 02V71 C, which re- one year the test for correct response pres- mained open for about 14 minutes. During this sure (force measurement), originally scheduled period, approximately 100 tonnes of steam at for the 1999 shutdown, on the affected safety/ a temperature of 288°C flowed through the blowdown valve 02V71 C. After this, the valve valve and its connecting blowdown line and was dismantled, inspected and reassembled. were introduced into the condensation cham- This work was also carried out in the presence ber (torus). The water temperature in the torus of an expert from the Inspectorate. was around 22°C at the beginning of the incident. The vertical blowdown line, approximately 11.4 Regulatory inspections 30m in length, between the main-steam line and the torus ensures rapid depressurisation in connection with as- of the reactor during incidents, and is designed pects of radiation pro- for this purpose. Nonetheless, extreme me- tection during periodic chanical loading in the form of vibration, as a result of unstable condensation, cannot be inspections at the Leib- excluded, when it has to be used. stadt nuclear power The purpose of the unannounced regulatory plant (KKL) inspection on August 12, 1998, which was carried out by a member of the department of 11.4.1 Reason for and goal of the regula- mechanical and civil engineering (MBT), was to tory inspections establish, by inspecting the opened system, During the shutdown for refuelling at KKL, all whether changes, or even damage such as piping welds of the 10 pressure nozzles (N3 bending and denting, had occurred to the pip- nozzles) of the recirculation lines were sub- ing as a result of the incident. For comparison jected to a repeat ultrasonic inspection (see purposes, the condition of the other, unaf- Section 4.2.2).These periodic inspections take fected blowdown lines was also examined. place at locations with increased dose rates. The aim of the regulatory inspection was to 11.3.2 Preparation for the regulatory determine, and evaluate, the measures inspection adopted by the plant operator in order to keep As a first step, the question of whether the the doses as low as possible for the involved blowdown line could be inspected over its whole test personnel (reduction of radiation exposure length using existing scaffolding, ladders and and optimisation of work procedures). other access possibilities had to be clarified with the aid of cross-sectional drawings of the plant. 11.4.2 Preparation for the regulatory The line starts from the blowdown valve at a inspections level of +6.5m on the inside wall of the drywell In accordance with the requirements of the and drops down to the 0m level before entering Inspectorate's Guideline R-15, KKL had submit- the torus as an accessible ventpipe. During the ted a radiation protection plan for the work on 1998 shutdown, the torus itself was accessible, the N3 nozzles. The Inspectorate checked since it had been drained in order to carry out whether this plan contained all the necessary other maintenance work. elements for optimisation of radiation protec-

HSK Annual report 1998 • Regulatory inspections 65 tion.These include determination of the radio- During a second regulatory inspection at the logical situation at the workplace, assessment work location, the Inspectorate ascertained of the shielding measures and the protective that four workers were present on a platform, measures against contamination and incorpo- which was originally intended for two people, ration of radioactive materials by the person- and that they only spoke Spanish. Communi- nel, as well as estimation of the personnel cation in German or English with KKL person- doses. Furthermore, the work procedures and nel was hardly possible. The dose rates at the their optimisation, the suitability of the tools to workplace were higher than expected and be used and the test equipment, as well as the deviations were noted from the work proce- space situation, has to be reported. An essen- dures which had been planned and trained.The tial element of the radiation protection plan, to KKL radiation protection department con- which the Inspectorate also pays attention, is firmed to the Inspectorate that it had already training of the personnel.This takes place away introduced corrective measures. from the radiation field on practice mock-ups, In the course of a third regulatory inspection and covers both familiarity with the work following completion of the work, the Inspec- equipment and co-operation within the work torate ascertained that the corrective meas- team. ures had enabled the planned doses to be adhered to during inspection of the nozzles 11.4.3 Observations and results towards the end of the test programme. A first The Inspectorate followed personnel training analysis, carried out by the KKL radiation pro- during a first regulatory inspection at the start tection department, indicated that the training of the revision shutdown. It ascertained that mock-up had not been used in an optimum training was carried out in a serious manner, way: e.g., necessary alterations to tools had that the protective clothing specified for the not been recognised, and known difficulties workplace was worn, and that the teams in- with the doors of the biological shielding had volved were able to carry out their work within been underestimated. time periods corresponding to those planned. In its regulatory inspection report, the In- In the course of this first inspection, the In- spectorate concluded that it expects the radia- spectorate recommended that the workplaces tion protection department to learn the lessons be monitored using a television camera, so from this work in the usual way and required that the work teams could be directed from a that KKL produce a report on this. location protected from radiation.

66 HSK Annual report 1998 • Regulatory inspections 12. Selected Aspects of Nu- clear Safety and Radiation Protection

12.1 Guidelines 12.2 Instructive events in foreign nuclear installa- The Swiss guidelines and recommendations, valid at the end of the year under review, are tions given in Table B1 of this report. These were Of the events reported in 1998 in foreign nu- drawn up by the Inspectorate, in some cases clear installations, none were of such signifi- in collaboration with the Swiss Federal Nuclear cance as to require the immediate implemen- Safety Commission (KSA) and other federal tation of measures to improve the safety agencies. During the year under review, the provisions in Swiss plants. Nevertheless, some following guidelines were revised and came events are described below because they are into effect: instructive, and because the lessons learned from them can contribute to improving the • HSK Guideline R-12/d: Measurement and safety of Swiss installations. notification of doses received by personnel exposed to radiation in the nuclear installa- 12.2.1 Leak in the residual-heat removal tions and in the Paul Scherrer Institute system of a pressurised water reactor • HSK Guideline R-25/d: reporting by the In a European nuclear power plant, a drop in Paul Scherrer Institute and by federal and the water level in the pressuriser, with simul- cantonal nuclear installations taneous initiation of alarms, took place during residual-heat removal operation (reactor shut The Inspectorate's guidelines show how the down, pressure and temperature much lower safety authorities wish to implement their than in normal operation). A leak inside the con- statutory responsibilities in the areas specified. tainment was diagnosed. In accordance with They are intended to create a secure legal ba- the specifications for such cases, the primary sis in that they indicate which criteria the com- circuit was cooled down further and the pres- petent authorities will apply in evaluating an sure was also reduced. After this, it was pos- application and in performing their supervisory sible to establish the location of the leakage. tasks. The affected circuit (line) was isolated, Such guidelines are not binding: the appli- whereby the leak was closed off. Further re- cant is entitled to propose other solutions. moval of residual heat continued via the sec- These guidelines are also applied in the evalu- ond, intact line; heat removal via the steam ation of existing installations in order to iden- generators would also have been available, if tify deviations. Compliance with the guidelines required. Since the location of the leakage was makes it easier to verify the safety status, within the containment, all the coolant lost was while any departures from the guidelines have collected in the sump and would have been to be evaluated on a case-by-case basis. available, if required, for emergency cooling, The Inspectorate's procedural guidelines using the circuits intended for this purpose. HSK Guideline R-15 and HSK Guideline R-25 The cause of the leakage was found to be a are an exception to the above: they are in- crack in a pipe bend of the return line. The af- tended to indicate the manner of reporting fected piece of pipe was replaced and sub- desired by the authorities and do not, in gen- jected to metallurgical examination.The cause eral, permit any deviations. was not a manufacturing defect; instead the crack had occurred due to thermal fatigue. Water originating from the primary circuit flows, in part, via a cooler and, in part, via a

HSK Annual report 1998 • Selected Aspects of Nuclear Safety and Radiation Protection 67 bypass installation. Depending upon the set- (steam). Entry and exit of the operating me- tings for mass flow, cooling occurs to a greater dium to and from the controlling piston takes or lesser extent. Furthermore, deliberate place via electrically driven pilot valves. In the warming-up of the piping is possible in this important operating region, the forces involved way. Since only small amounts of water are in opening and shutting are so large with this required during warming-up of the system, the design that a defect (non or faulty opening, delivery capacity of the recirculation pumps is failure to shut) is highly improbable. Thus the heavily throttled back. This mode of operation closing pressure can be exactly set. The pre- tends to produce undesirable effects, such as condition for this, however, is that the control thermal stratification, and/or temperature lines to the connected valves are not isolated. changes at various flow levels, and was ascer- For hand-operated valves, an isolation system tained to be the basic cause of the problem. involving keys is installed in order to reduce the Crack propagation in the pipe bend occurred probability of such a mistake to a negligible relatively rapidly; the affected plant had only value.This functions according to the principle been in operation for half a year. Despite its that operation of the hand valve is only possi- minor consequences with regard to safety, the ble with the appropriate key. The key can only responsible regulatory authority assessed this be removed if the valve is in the correct posi- event as belonging to level two on the seven- tion with regard to safety requirements. The level INES scale (see also Section 12.7) be- positioning of the valves can be checked at a cause of its generic importance. central location on the basis of the boxes used Similar cooling systems exist in the Swiss to store the keys. In the case of the above- plants. The way in which they are operated was mentioned event, an administrative mistake optimised originally during commissioning of occurred during checking: the plant had been the plants. The plants have been in operation shut down over a short period to carry out a for many years and no defects have been de- repair and the affected control line had been tected during any of the periodic inspections switched into the repair mode. This had not carried out to date. Thus the lessons learned been reversed upon the resumption of opera- from this event have no direct consequences tion. for the Swiss plants. Nonetheless, they im- Because of the large safety reserves in this prove understanding and knowledge with re- plant (the steam generator safety and blow- gard to such undesirable effects and thus con- down valves exist in quadruplicate), the mis- tribute to the prevention of similar damage. take had only insignificant consequences with regard to safety. The event initiated an exten- 12.2.2 Non-availability, when required, of sive analysis of administrative procedures in a steam generator safety valve at a the affected nuclear power plant. This con- pressurised water reactor firmed that the basic concept was correct, but In a European nuclear power plant, the opera- that modifications were necessary in detail. tor initiated a turbine shutdown during turbine Although the consequences for safety were testing because of technical problems. In the low, the responsible regulatory authority allo- course of this, the turbine bypass line was put cated the event to level two on the INES scale, into manual operation and isolated. As was to thus attaching high importance to weak-points be expected, this produced an increase in the in the plant administration. steam pressure with initiation of a reactor With the exception of one plant, the safety scram and activation of the steam generator valves for overpressure protection of the main overpressure protection. Immediately after steam in the Swiss nuclear plants are operated this, the turbine bypass was again activated, directly by the force of springs and are com- which corresponded to the end of the tran- pletely independent of control lines. The one sient. plant, in which pilot valves for operation of the During the subsequent analysis of the safety valves are used, has three, redundant, course of this event, it was discovered that one control lines per safety valve. No common iso- of the four safety and blow-down valves had lation possibility exists for all three lines, as not opened.The investigation showed that the was the case in the affected foreign plant. In control line to the pilot valve, which is used to the Swiss plant, the administrative barrier to control the safety valve, had erroneously been check and prevent false positioning of the iso- isolated by means of a hand-operated valve. lation valves consists of a specially notched Thus the safety valve could not open as re- rod, which has to be mounted upon the open- quired. ing spindles in order to permit operation of the In this plant, opening and shutting of the valves.This rod is secured with a lock and can steam generator safety and blow-down valves only be mounted on the spindles if at least two is carried out using the operating medium valves are in the open position. Independently

68 HSK Annual report 1998 • Selected Aspects of Nuclear Safety and Radiation Protection of this, a check is carried out as to whether the which use only two numerals to form the year rod is mounted upon the spindles in order to in date functions. This is the case particularly ascertain readiness for operation. In this way, with older computer programmes, but the er- false positioning of the isolation valves can be ror cannot be excluded, on principle, even with avoided with a high degree of probability. A newer software. Furthermore, the possibility general lesson from the above-mentioned exists that other combinations of numbers, event is that administrative procedures must e.g. 9.9.99, may lead to disturbances. All such be capable of being checked in a simple man- error possibilities can also occur in systems ner. which contain built-in microprocessors (so- called "embedded systems"). 12.2.3 Possible gas bubbles in emergency The supervisory activities of the Inspector- cooling lines as a result of valve ate include the formulation of relevant require- leakages ments on the nuclear power plants in the con- Unexpected pressure peaks occurred during text of safety, the checking of documentation start-up of the low-pressure emergency cool- submitted by the plants on the allocation of ing systems in several foreign nuclear power systems, analyses/tests of the systems and plants equipped with pressurised water reac- further measures, participation in tests on Y2K tors. Such processes are undesirable since compatibility, and periodic enquiries of the they lead to high loads on the pressure-retain- plants as to the status of problem clarification, ing components.The operators of the affected or the treatment of individual aspects. plants carried out extensive investigations to The requirements which the Inspectorate determine the causes. As a rule, such proc- has made of the plants are appropriate, in an esses occur if gas has collected in a system international context, as shown by the results containing water.This was confirmed to be the of international surveys and the attention paid case here upon venting the systems, since by the Inspectorate to the status of efforts in unexpectedly large amounts of gas (nitrogen) other countries. This has also shown that the were found. The source of the gas was deter- time period, in which the problem is being dealt mined to be the borated water tanks (accumu- with, is approximately the same as in other lators), which are pressurised with nitrogen. countries (e.g. USA). These tanks are connected to the emergency In addition to the general supervisory pro- cooling systems via piping and a series of iso- cedure described above, the Inspectorate has lation and check valves. It became apparent also discussed, and in some cases itself inves- that one or more valves, lying in series, were tigated, those systems which affect radiation not leak-tight. Nitrogen, or water saturated protection with the nuclear power plants, PSI, with nitrogen, was thus able to enter the low- and further nuclear research installations. pressure systems and cause accumulations of Measures have been initiated with regard to gas. individual pieces of equipment affected (e.g. Similar effects are basically possible in the revisions to the MADUK-ANPA system, soft- Swiss pressurised water reactors, since these ware replacement with CIS/DAISY). are also equipped with borated water tanks In all Swiss nuclear power plants, systems containing a nitrogen atmosphere. To date no and software programmes have been, or are occurrences of this type have been observed being, analysed by the supplier, or system during operation of the low-pressure systems. manager, of the power station in a systematic Among other things, this is due to the fact that way with regard to the Y2K problem. If neces- particular attention is paid to possible lack of sary, they are being replaced or improved. leak-tightness during the maintenance of During 1998, various systems in all nuclear valves in the Swiss plants. power plants were subjected to a test for the change in date. Further examinations will occur in 1999. 12.3 The year 2000 date In general, the problem of the date change change problem affects only individual pieces of equipment within the safety systems of the Swiss nuclear Since the beginning of 1998, the Inspectorate power plants, since most of these systems are has been dealing with the year 2000 date hard-wired and thus not controlled by software change problem (Y2K problem) within its regu- programmes. Digitally instrumented and con- latory area. It has limited its considerations, in trolled safety systems are still the exception in the main, to questions of nuclear safety and the Swiss nuclear power plants. radiation protection. All other programmable digital systems in The basic cause for Y2K disturbances in the Swiss nuclear power plants are of minor computer systems are all software products relevance to safety, or are important only in

HSK Annual report 1998 • Selected Aspects of Nuclear Safety and Radiation Protection 69 terms of commercial operation.These include, 12.4 Organisational factors e.g., information and control systems for the plant. The nuclear power plants are designed, and safety culture with regard to safety, in such a way that they The organisation of a nuclear power plant has can be shut down safely, and held in a safe an important influence on the way its staff condition, without the use of these systems. behave. In recent years, much research effort Possible occurrence of a "Y2K problem" will has been put into the search for criteria and not affect realisation of the protection goals practical methods for the assessment of such "reactor shutdown" and "reactor cooling". influences, as well as into the appraisal of the Disturbing influences from outside are a organisation itself. These efforts at establish- particular aspect of the situation for a nuclear ing assessment criteria are not yet developed power plant: e.g., if the electricity network in to the point where they have been accepted the area of the power station breaks down and by a wide circle of users. As a result of this, switching to the nuclear power plant's internal few, generally valid indications with regard to supply system does not take place, the reac- the optimisation of organisations have been tor will be shutdown. Subsequently, the decay derived from this work to date. heat still being produced in the reactor core The interaction between the organisation has to be removed by the residual heat re- and safety will be of increased importance as moval system in a self-sufficient way, i.e. with a result of liberalisation of the electricity-gen- an internal electrical supply, which cannot be erating market and the associated cost-pres- affected from outside. This case was already sures. Optimisation of resources will be nec- considered in the design of the nuclear power essary. Experience in foreign plants has shown plants long before recognition of theY2K prob- that this optimisation can be problematic. In lem. To deal with it, the four Swiss nuclear several plants, the operator was no longer able power plants have multiple, internal emer- to adopt the organisational measures neces- gency-power diesel generators, which are in- sary to ensure safe operation; some plants dependent from the electricity network and have been shutdown, at least temporarily, for from one another. In addition to this power- organisational reasons.The new orientation in producing equipment, three nuclear power the energy sector thus requires the regulatory plant units also have independent supplies authority to be especially aware of organisa- from nearby hydraulic power stations. tional aspects. If the regulatory authority finds Despite the extensive system analyses, indications, which could lead to weak-points in tests and software replacements, unforeseen the organisation, it has the responsibility to operational disturbances cannot wholly be ex- make the operator aware of these and, if nec- cluded.The way in which such disturbances, or essary, to take direct action. external disturbances (e.g. breakdown of the This theme has been taken up by interna- electricity network, as described above), are tional organisations and discussed at special- dealt with must be prepared for in the context ist conferences, in order to prepare the regu- of so-called contingency planning for the nu- latory authorities for their task. The following clear power station. In particular, adequate pro- international meetings were relevant for the vision of personnel resources is required for Inspectorate here. this.The Inspectorate has thus demanded that In 1998, members of the OECD/NEA "Com- the plants make available sufficiently increased mittee for Nuclear Regulatory Activities" operating teams for the period of the critical (CNRA) worked on this topic under the chair- date change. manship of the Inspectorate.They produced a The Inspectorate will follow the activities of report defining the role of the regulatory au- the plants and, in particular, their contingency thority in the development and assessment of plans during 1999 and will ensure that the safety culture. This document will be published Swiss nuclear power plants are correctly pre- in 1999. pared for the year 2000 date change with re- The OECD/NEA "Committee for the Safety gard to system functionality, plans for meas- of Nuclear Installations" (CSNI) concentrates ures to be taken against possible events on the assessment of organisations and their caused by the date change, and the way in influence on the safe behaviour of staff. This which personnel resources are made available. committee has charged the permanent working group "Operational Experience and Human Factors" with the task of determining the status of science and technology in this area.The Inspectorate has taken on the leading role in this work and organised, in June 1998, a workshop on the topic "Organisational Factors -

70 HSK Annual report 1998 • Selected Aspects of Nuclear Safety and Radiation Protection Identification and Assessment", in which 27 - the current status report on questions con- specialists from twelve countries participated. cerning the disposal of radioactive waste in The report on this will appear in 1999 and con- Switzerland; tain an account of relevant organisational fac- - the commission's seminar on the topic of tors, as well as a description of assessment "increased burn-up, extended operational methods and their use in various countries. cycles and MOX fuel assemblies", with par- In June 1998, the IAEA organised a special- ticipation of foreign experts and experts ist meeting on the topic "Safety Culture Self- from the Swiss nuclear installations and the Assessment: Highlights and Good Practices". Inspectorate; The Inspectorate participated in this meeting - the expertise for the general secretariat of and presented the relevant Swiss experience the Federal Department for Environment, gained up to that point in the area of self-as- Transport, Energy and Communication sessment of safety culture. (UVEK) concerning the UVEK proposals for transfer of the Inspectorate to a "National Safety Agency" (NASA). 12.5 Commission for the Furthermore, the commission's assessments safety of nuclear instal- serve, in part, as a form of quality control for the Inspectorate, in particular since additional lations specialist knowledge and experience from out- The Federal Commission for the Safety of Nu- side the Federal Administration, and also from clear Installations (KSA) is an advisory body to outside the nuclear area, are introduced via the Federal Council and to the Federal Depart- this group of experts. ment for Environment, Transport, Energy and The activities of the Swiss Federal Commis- Communication (UVEK). It works in parallel sion for the Safety of Nuclear Installations are with the Inspectorate in assessing applications summarised annually in an appropriate report. for certification, tracking the operation of nuclear power plants with regard to basic aspects of nuclear safety, the release of specifications, 12.6 IRRT: IAEA experts as- and follows research, both within the country and abroad, in the area of nuclear safety. If sess the Inspectorate necessary, it prepares recommendations. At the request of the Inspectorate, the Federal The commission consists of a maximum of Department for Environment, Transport, En- 13 experts from the relevant, individual areas ergy and Communication (UVEK) invited an of science and technology. Its secretariat is International Regulatory Review Team (IRRT) to part of the Inspectorate for administration pur- observe in detail, and assess, the Inspector- poses. The Inspectorate prepares the neces- ate's work procedures, responsibilities, areas sary, additional information for the commission of competence, and the framework within to reach an opinion, if and as required. which it operates. This mission of the Interna- In particular, the commission also com- tional Atomic Energy Agency (IAEA) involved 11 ments on the corresponding expert reports of experts from Argentina, Belgium, Canada, Fin- the Inspectorate, in the context of giving its land, France, Great Britain, Spain, and the opinion with regard to applications for certifi- United States of America and took place at the cation. Furthermore, it always discusses and Inspectorate in Wurenlingen from November makes comments on the annual report of the 30 to December 11, 1998. At the end of Janu- Inspectorate concerning the Swiss nuclear in- ary 1999, the team delivered a comprehensive stallations. report to Switzerland containing its recommen- In the year under review, the following KSA dations and suggestions for improvement, as activities were of particular importance for the well as remarks on good working procedures Inspectorate: and practices of the Inspectorate. - the expertise for the Federal Department for The experts gave the Inspectorate good Environment, Transport, Energy and Com- marks in the areas of safety analyses, techni- munication (UVEK) concerning fulfilment of cal assessments, radiation protection and the conditions, with regard to fuel assembly emergency preparedness. However, they ex- damage, recommended in connection with pressed criticism with regard to the way in the possible increase in power of the which the Inspectorate currently carries out Leibstadt nuclear power plant; inspections in the plants.This criticism was not - the assessment of the first national report directed at the number of inspections, which on fulfilment of the IAEA Convention on Nu- reached the notable number of 519 in 1998, clear Safety, which has been ratified by but was concerned with the way in which they Switzerland; were carried out, indicating that this should be

HSK Annual report 1998 • Selected Aspects of Nuclear Safety and Radiation Protection 71 more systematic and formal. To date, the in- 12.7 Procedure in connection spections have basically been carried out during the operational shutdown of the nuclear with the evaluation of plants for maintenance and refuelling, in con- events nection with alterations to the plant, and in the 12.7.1 The Inspectorate's guidelines for context of work required after events. The ex- the notification of events perts recommend the introduction of a com- In accordance with the Inspectorate's Guide- prehensive, systematic concept and pro- lines R-15 and R-25, the operators of Swiss gramme for inspections, in which operational nuclear installations are obliged to notify the safety should also be tested to a greater ex- Inspectorate of any events which occur. The tent. Furthermore, the degree of authority, as purpose of this notification is threefold: well as the rights and the duties, of the inspec- - notification of events to allow early recogni- tors should be clearly established. tion of weak-points and their rectification; The experts also recommended that more - notification of accident conditions to alert emphasis be placed upon supervision of the the Inspectorate's emergency organisation transport of radioactive materials. They con- and other authorities; sider it necessary that the Inspectorate extend - notification of events of public interest to al- its supervision in the transportation area to all low the Inspectorate, as the supervisory types of radioactive materials, rather than it authority, to make an independent assess- being limited only to nuclear fuel. This point will ment and to provide the public with official be clarified together with the Federal Office of information in a rapid manner. Public Health (BAG), which is responsible for For practical reasons, and to achieve these radiation protection in the non-nuclear area. objectives, the established classification sys- Furthermore, the IAEA experts recommend tem has been retained. On the one hand, it that a classification system for radioactive takes into account the significance of events waste be established in a legally binding way. with regard to safety using the following cat- In addition, the experts propose that the egories U (unclassified), B (of minor relevance Inspectorate should have a more independent to safety), A (of relevance to safety) and S position with regard to those authorities con- (events which endanger the plant or its person- cerned with the use and promotion of nuclear nel, or which could have considerable radiologi- energy. This recommendation will be examined cal effects on the environment). On the other in the context of the formation of a National hand, it takes account of events which are of Safety Agency (NASA), whose activities could public interest (6 = (German) Offentlich: pub- include further safety-related tasks of the lic);These are, for example, incidents which are UVEK, in addition to the work of the Inspector- registered externally in an optical or an acous- ate. The IRRT recommendations confirm the tic way. correctness of this development and require corresponding alterations to the legal basis for 12.7.2 International Nuclear Event Scale, the Inspectorate's work. INES In advance of the IRRT mission, the Inspec- According to the International Nuclear Event torate had already taken action in some of Scale (INES), events are assigned to seven lev- these areas in order to improve the effective- els (level 1 to level 7) according to their conse- ness of its work and to diversify the regulatory quences. Level 7 events have serious conse- methods involved. Among other points, it is quences in the vicinity of the plant (e.g. intended to introduce a quality management Chernobyl). Level 1 events are of safety-rel- system for the Inspectorate's work. In the opin- evance for the plant, but have no effects on the ion of the IAEA experts, these efforts should environment. The INES scale, which was be intensified and accelerated. The Inspector- adopted definitively in 1992, has also been ate has produced an eight-point plan to satisfy extended down to level 0 for "normal events", the most important of the IRRT recommenda- such as, e.g., an automatic reactor scram with- tions. This plan concerns, in particular, the in- out further complications. Such events are re- troduction of a quality management system ported to the responsible national authority, and a systematic concept for inspections, as but are of no importance with regard to safety. well as more comprehensive supervision in The scale aims to inform the media and the connection with the transportation of radioac- public of events at nuclear plants by putting tive materials.These measures will be accom- them into their correct perspective with regard panied by a re-organisation of the Inspectorate. to safety.The INES User Manual was produced as the yardstick, with evaluation principles valid for all countries. The IAEA plays a central co- ordinating role in the exchange of event notifi-

72 HSK Annual report 1998 • Selected Aspects of Nuclear Safety and Radiation Protection cations. Each member state has undertaken to decade, the area of so-called periodic inspec- report all events from level 2 upwards to the tions has been undergoing extensive changes. IAEA for distribution of information to the other These involve a move away from fixed, detailed member states. The IAEA also organises ex- specifications and an increased emphasis on changes of experience between member greater flexibility and more focused proce- states in order to promote uniformity in the dures. The intention of this change is to in- use of the scale. Particularly at the lower end crease the effectiveness and information con- of the scale (level 0 to level 1, and sometimes tent of periodic inspections. On the one hand, even level 2), the criteria cannot be specified it affects the choice of the components and precisely enough to completely prevent differ- component parts to be inspected. Increasingly, ences in the engineering evaluations. With the the risk associated with the part to be in- large number of different plant types in the spected is taken into account (risk-informed participating countries, and the differing safety inspection). On the other hand, it affects the provisions, it is almost impossible to achieve requirements applying to inspection proce- complete standardisation of the safety rel- dures and inspection personnel, whereby evance of disturbances at the various plants, specifications on the inspection techniques even from a technical viewpoint. and procedures to be used are being replaced Switzerland, as a member of the INES or- by specifications concerning proof of the re- ganisation, has co-operated in the develop- quired level of performance. This proof is de- ment of the INES system from the beginning scribed in the USA as "performance demon- and uses the INES scale for nuclear power stration" and, in Europe, as "qualification". plants and nuclear research installations. This does not exempt the Swiss operators from 12.8.1 Periodic inspections of the "risk- notifying events in accordance with the Inspec- informed" type torate's Guidelines R-15 and R-25, but is in- In 1998, the American nuclear regulatory com- tended to provide additional information for the mission (US-NRC) published a regulatory guide public. describing the concept and the conditions for In principle, each INES level differs from the periodic inspection programmes of the risk-in- next by a factor of 10 to 100 in safety signifi- formed type. Interest, and preliminary changes cance.Three aspects are taken into considera- in this direction, also exist in Europe. A task tion: "degradation of safety measures" (ap- force from the Nuclear Regulators' Working plies from level 1 to level 3), "consequences Group of the European Union determined the within the plant" (level 2 to 5), and "radiologi- status of this topic, with participation by the In- cal consequences outside the plant" (level 3 to spectorate, and drafted a "current practices 7). The individual criteria are given in a simpli- document" in 1998. It is intended that this fied form in Table B2. Accidents start at level document be published in 1999. The existing, 4. qualitative, risk-informed aspects have been The INES system serves to enhance the more clearly identified, made more systematic, objective understanding of the consequences and given greater importance during revision of events abroad. It helps to avoid misunder- of the SVTI specification NE-14, which is the standings in reporting events in nuclear plants, Swiss guideline for periodic inspections. First and places them in their proper safety perspec- studies have also been carried out in a plant- tive. Nearly all countries comply with the INES specific way. The Beznau nuclear power plant reporting system, whereby their safety authori- ordered performance of the first phase of a ties notify the IAEA or at least check the appro- quantitative, risk-informed study on periodic priate report before it is sent.The INES system inspection of the reactor coolant piping. The is able to ensure a world-wide policy of public Leibstadt nuclear power plant is investigating information on events in nuclear installations the use of probabilistic safety analyses in the that is open and clear. selection, for ageing surveillance purposes, of components belonging to the safety classes 2 to 4. 12.8 Developments and ten- 12.8.2 The qualification of inspection dencies in the area of systems periodic inspections The ASME code requires that ultrasonic in- Periodic, non-destructive inspections are car- spection systems, i.e. inspection procedures, ried out on mechanical components, such as equipment and personnel, be qualified by the reactor pressure vessel and the piping of means of a standardised "performance dem- the main coolant circuit, which are classified as onstration". In 1999, this code requirement will important for safety. Since the beginning of the become binding for the American nuclear in-

HSK Annual report 1998 • Selected Aspects of Nuclear Safety and Radiation Protection 73 dustry. In Europe, in 1996, the representatives basic principles of the European methodology of the regulatory authorities of the European and thus serves as a pilot study, in which many Union countries and Switzerland formulated a aspects and problems related to practical ap- consensus document containing common re- plication can be recognised and investigated. quirements for the qualification of periodic in- An expert from the American "Performance spection systems. These requirements corre- Demonstration Initiative" programme gave spond to the so-called European qualification advice and support to the "Qualification Body" methodology, which the European Network for during preparation, performance, evaluation Inspection Qualification (ENIQ) published as a and documentation of the blind tests. This help revised, fundamental document in 1997. extended over several months during 1997 and The concept for qualification of inspection 1998 and was of decisive importance in ena- procedures, equipment and personnel requires bling the blind tests to be carried out both in a a change in the attitude of all involved and al- professional way and within the allotted time terations to their work procedures. The Euro- period.This was, incidentally, the first advisory pean qualification methodology also still has to activity of the "Performance Demonstration find its most appropriate practical form during Initiative" outside the USA. The project could actual use. For this reason, it is not advisable not rely upon existing proof of performance, to introduce strict qualification requirements since the inspection of mixed welds is still a abruptly and across the board. Since 1993, challenge, both with regard to inspection tech- several qualification procedures have been nology and to the tester. Several inspection carried out in the Swiss nuclear power plants, firms were involved and a number of mostly at the suggestion of the Inspectorate. optimisation phases were necessary before Increasingly, the European methodology being the qualification procedure could be success- developed has been applied to these proce- fully completed in the early summer of 1998, dures. three years after its initiation. This time-frame A project, initiated in 1995 by the Leibstadt corresponds to the experience also gained in nuclear power plant, for qualification of the Sweden, where a larger number of qualifica- ultrasonic inspection of mixed welds and tion procedures have been carried out in ac- austenitic welds at RPV nozzles was in its fi- cordance with the European qualification nal, decisive phase during 1998. From the be- methodology during recent years. ginning, it had been conceived according to the

74 HSK Annual report 1998 • Selected Aspects of Nuclear Safety and Radiation Protection 13. Safety research

The Inspectorate has to assess the safety of ished at the Novaggio (Tl) site. The labora- the Swiss nuclear installations according to the tory experiments were continued in order to current state of science and technology and characterise the way in which caesium is can, if necessary, require that measures are taken up by fungi mycellium and transported taken to further enhance the level of safety. In within this. Definitive results are not yet order to carry out this task in the most cost- available. effective way, the Inspectorate supports the following typical projects in the area of regula- 3. In 1998, a greenhouse experiment with fruit tory safety research: trees was planned in the context of the - research projects at the Paul Scherrer Insti- IAEA BIOMASS project (International pro- tute (PSI) and the technical universities; gramme on BlOsphere Modelling and - individual projects undertaken by national Assessment methods) in order to investi- and international engineering companies; gate the way in which radioactive caesium - participation in international projects. is absorbed into the fruit via the leaves.The All research activities supported by the Inspec- experiment had to be postponed until 1999 torate are of practical value for its supervisory because the trees exhibited too little blos- work. The projects provide new and important som formation and because the few remain- knowledge in areas as diverse as structural ing blossoms withered in spring. integrity (ageing of nuclear power plant components), the investigation of complex phe- 4. The age-dependent distribution of caesium nomena associated with the development of and strontium in tree trunks in the vicinity of events, the effects of radiation on people and Chernobyl was investigated in co-operation materials, and the influence of human factors with the Belgian Nuclear Research Centre on plant safety. This knowledge is of immedi- (SCK/CEN) in Mol. ate use for the regulatory work of the Inspec- torate. The results of this research project are continu- During the year under review, the following ally evaluated and put into practice. The work individual projects were supported: will be continued in 1999.

13.1 Radioecology: studies and scientific/technical 13.2 Co-operation with re- services provided by PSI gard to dosimetry and The goal of this PSI project is to expand both radioanalysis; PSI, theoretical and applied knowledge in the area Villigen of radioecology. The knowledge thus obtained is of importance for the assessment of the Together with the project "Co-operation with effects of radioactive releases, both during regard to Radioanalysis", the PSI project "Co- normal operation and following accidents. In operation with regard to Dosimetry" provides 1998, the main attention was focused on four valuable information for the improvement of topics: dosimetry and radiation monitoring. 1. In the CHECOSYS work group, a deeper In 1998, AC laboratory specialists from the understanding of the radioecological model Swiss army were also able to benefit from this was obtained by means of parameter stud- co-operation, since PSI organised two training ies. The amounts eaten were revised on the courses for them. As well as serving the direct basis of the "4th Swiss Report on Nourish- goal of training, these courses permit the ment". emergency preparedness of the special PSI laboratory, belonging to the emergency organi- 2. In the EU project SEMINAT (LongTerm Dy- sation for cases of increased radioactivity namics of Radionuclides in Semi-Natural (EOR), to be checked. Environments: Derivation of Parameters and Valuable operational experience was gained Modelling), the field experiments were fin- with the improved calibration equipment for

HSK Annual report 1998 • Safety research 75 tritium air-contamination monitors, which was cerning the population in which these cases developed by the measurement technology occur is just as important as registration of the section of the PSI department for radiation cases themselves. The only complete survey monitoring and disposal (ASE). for this is the census. For reasons of data pro- Calibration measurements at the thorax in- tection, the census and statistics on the corporation monitor of the Beznau nuclear causes of death are anonymous. It is of inter- power plant, using a dummy, showed that the est for epidemiology to relate individual pieces calibration methodology of such measuring of data from both data sources, since this al- equipment can be standardised.These results lows questions, which could not previously be will be of value in formulating the requirements analysed, to be investigated, and better atten- of the regulatory authority with regard to incor- tion to be paid to influencing and interfering poration measurements, in the context of the factors. In the context of this research agree- new dosimetry legislation. ment, the Inspectorate supported a project Development work on the neutron dosi- intended to enable the causes of death statis- metry system based on CR-39 (organic poly- tics and the census to be coupled and evalu- mer) has been completed and the system has ated, without detracting from data protection worked satisfactorily during routine operation for individuals. A feasibility study was carried at PSI. out and first results were obtained. These Furthermore, whole-body measurements showed that coupling via the date of birth, as were carried out at PSI on Swiss railway em- well as several further variables contained in ployees in the context of investigations of per- both databases, can be carried out success- sonnel dosimetry associated with the transpor- fully for the vast majority of cases of death. tation of depleted fuel assemblies. These measurements proved that no incorporation had occurred during transportation. 13.4 SVIolecular-biological Co-operation in these areas with PSI is of investigations of cellu- great interest in the context of on-going radiation monitoring. In particular, the alpha analy- lar radiosensitivity; PSS, ses, carried out for the nuclear power plants, Villagers are important for the Inspectorate. During the year under review, the focus of radioanalytical Damage occurs to the hereditary genes (DNA) work lay on development of analysis methods if one irradiates, e.g., the cells of mammals. to determine the isotopes Ni-63 and Sr-90 in The cells react to DNA damage by ceasing re- earth samples and plants, as well as to dem- production and attempting to repair the dam- onstrate the presence of actinides. At present, age. If this is impossible, or does not occur these new developments are being used for quickly enough, the cell decides to die in a the analysis of earth samples (baseline values) controlled manner, thus preventing damage to in the vicinity of the central interim storage the organism, e.g., through the creation of facility ZZL, which will shortly be completed cancerous cells. The cell often requires en- (accumulation of reference data for the zymes, which phosphate other proteins to ZWILAG project).These new methods replace control such processes. In this way, such en- the older procedures for the analysis of Sr-90 zymes alter the function of the proteins, and in the context of environmental monitoring at thus the behaviour of the cells. The so-called PSI and at the Beznau nuclear power plant. MAP cinases are an important group of these Co-operation will be continued in both of enzymes. In the last year, the only, highly sen- these specialist areas. sitive, non-radioactive activity test presently available for very different types of MAP cinases was developed in the course of this project. Such tests provide information about 13.3 Special epidemiologicaS the way in which cells transmit signals and questions: the Zurich thus permit understanding of the way in which cantonal cancer register cells respond to irradiation. For this reason, the Epidemiology (the study of the distribution of Inspectorate supports this research work at health conditions and their causes) is based on PSI. information obtained from very different sources: causes of death statistics, registration of the incidence of illnesses, hospital statistics, and surveys. To date, only the causes of death statistics are registered in a complete way throughout Switzerland. Information con-

76 HSKAnnua! report 1998 • Safety research 13.5 The role of "Vascular sult of the high-energy gamma radiation. This is a normal phenomenon for a boiling water Endothelial Growth Fac- reactor and was already take into account dur- tor" (VEGF) during the ing design of the plant. As in previous years, repair of cell damage the PSI site also showed higher count rates induced by irradiation; than in the vicinity. Outside the nuclear and research installations, however, no increased PSI, Villigen radioactivity, which could not be attributed to Blood-vesseis and capillaries are covered on fallout from atomic weapon testing or from the inside with endothelial cells, since these Chernobyl, was found throughout the whole are the precursor cells to capillaries and ves- country. The level of activity has not changed sels. Regeneration of vessels is a complicated in comparison with previous years. process, which is controlled by hormones such as VEGF. Damage to the vessels is, on the one hand, an important aspect of acute radiation 13.7 WINDBANK for the damage and, on the other hand, a promising starting point for cancer therapy in order to upper Aare valley; PSI, prevent the supply of blood to tumours. For Villagen this reason, the radiation sensitivity of en- The expression "WINDBANK" is an abbrevia- dothelial cells has become an interesting topic tion of the German word for a wind field data- of research. First experiments to determine base. The wind field situation in the zones 1 the radiation sensitivity of endothelial cells and 2 around the Muhleberg nuclear power have already been carried out in the context of plant is being recorded and classified accord- this new research project. VEGF is expected to ing to meteorological aspects, in the project support the repair of tissue damaged by radia- WINDBANK for the upper Aare valley. Three- tion and may thus be of therapeutic use in dimensional wind fields are being prepared connection with radiation damage. For this from this and stored in a database.This permits reason, the Inspectorate supports basic re- rapid determination of the danger areas for search onVEGF emergency radiation protection planning and, in conjunction with computer models (e.g. ADPIC), of the dispersion of damaging sub- 13.6 Further methodological stances in the case of an accident. This work development in aero- will be continued for the middle region of the Aare valley. radiometry; ETHZ The ability to assess natural and artificial radioactivity quickly, and over large areas, is being 13.8 Behaviour of further improved in this programme. For this purpose, the existing measuring equipment for radionuclides from nu- aerogamma spectrometry, including the asso- clear power plants in ciated software, is undergoing further develop- the rivers Aare and ment. Rhine, EAWAG, Aeroradiometric data are important to the Inspectorate in order to evaluate the radiation Dubendorf-Zurich situation in the vicinity of nuclear installations. At the end of 1998, the agreement between They are also important with regard to the ac- EAWAG and the Inspectorate, which had cumulation of evidence. During an emergency lasted for a total of six years, was terminated situation, it is desirable for the evaluated data with the publication, in the EAWAG report se- to be quickly available (in real time). A further ries, of the final report by A.AIbrecht entitled focus within this programme is the participa- "The Behaviour of Nuclear Reactor Derived tion in an international joint project. Metallic Radionuclides in the Aquatic System In 1998, the vicinity of the Beznau and of Switzerland". Leibstadt nuclear power plants was measured Due to the very comprehensive nature of within the framework of the annual measure- the final EAWAG report, it is, of course, only ment flights of the National Alarm Centre possible to provide a summary here. The over- (NAZ).The results show the same picture as all problem of the hydro-transport of radioac- was obtained in previous years. The Beznau tive materials is divided into 7 subsidiary as- nuclear power plant could not be seen on the pects as follows: activity maps. In contrast, the Leibstadt nu- - composition, and changes over time, of clear power plant could be identified as a re- waste water from the nuclear power plants

HSK Annual report 1998 • Safety research 77 exposed, during operation, to the reactor coolant. PSI has the necessary autoclaves and test equipment to carry out crack-growth experiments under controlled conditions with regard to mechanical loading and water chemistry. Under static, mechanical loading, the investigated reactor-pressure-vessel (RPV) steels exhibit high resistance to stress corrosion cracking when exposed (without irradiation) to simulated, BWR water chemistry of operational quality.These results were confirmed by an international Round Robin experiment in co- operation with the MPA Stuttgart (Germany), Siemens KWU (Germany) and the technical research centre VTT (Finland). The experimental PSI database on the stress corrosion cracking of ferritic RPV steels under BWR conditions is very extensive. Last year, these data were made available to the US Electric Power Re- search Institute (EPRI), at their request. Work The behaviour of radioactive materials in the rivers Aare planned for 1999 includes investigations of the and Rhein. Source: EAWAG, Diibendorf stress corrosion cracking of weld metal and heat-affected zone in comparison with the before its introduction into the aquatic sys- base material, as well as crack-growth-rate tem; experiments on the susceptibility of low-alloy - physical/mathematical modelling of the steels to strain-induced corrosion cracking. transport of radionuclides in river systems; It is important that the Inspectorate contin- - adsorption of metallic radionuclides, in par- ues to follow this work in connection with the ticular Co, on particles (chemical processes); assessment of the structural integrity of pres- - sedimentation and re-suspension of parti- sure-retaining components. cles in aquatic systems; - combined models to describe adsorption, sedimentation, and the physics of lakes and rivers; - results for further nuclides (Mn, Zn, Cs) apart from Co, which was the primary topic of investigation; - importance and use of the information obtained for monitoring in the vicinity of nuclear installations, The knowledge concerning the transport of radionuclides in aqueous media was improved and, in part, revised, as a consequence of the results obtained. Using this as a starting point, the environmental monitoring programme in rivers and lakes downstream from nuclear power plants could be optimised.

13.9 Stress corrosion cracking of steels for reactor components in high- temperature water; PSI, Villigen The goal of the research project is to study the stress corrosion cracking behaviour of steels Material testing in the hot cells of PSI. The mechanical which are used for pressure-retaining compo- properties of materials coming from the NPPs are nents in boiling water reactors (BWR) and are tested here. Source: PSI, Vil!igen

18 • Safety research 13.10 Control of Light Water 13.11 REVENT SI: influence of Reactor (LWR) contami- natural convection in nation; PSS, Villigen the containment, after During the year under review, projects were a severe core meltdown carried out with regard to specific questions accident, on controlled, concerning the interaction between austenitic stainless steels and BWR water containing filtered pressure relief; typical impurities. Furthermore, an assess- ETHZ, Zurich. ment, ordered by the Inspectorate, of water chemistry in KKL was worked upon and com- In the REVENT research project, the influence pleted. of so-called re-entrainment of radioactive ma- During the 1998 reporting period, particular terial and aerosols from the sump in the course attention was paid to the following areas: of a controlled, pressure-relief phase during a severe core meltdown accident is being experi- 1. Assessment of the measures proposed by mentally investigated. The results are impor- ABB (Sweden) to reduce the corrosion dam- tant for improved determination of the amount age (shadow corrosion) which has occurred of activity which could possibly be released in the region of the spacers on the fuel ele- externally as a result of such an accident. ment cladding in the Leibstadt nuclear A model containment of 5m3 capacity, power plant. However, the cause of the equipped with a venting system, is used as the shadow corrosion has not yet been finally experimental installation. A major goal of this established and requires further investiga- investigation is to clarify the way in which aero- tion. sols are carried into the venting system during start-up and steady-state operation of the pres- 2. Completion and evaluation of the experi- sure-relief system, taking into account natural mental screening test to clarify the influ- convection in the containment. ence of substances contained in the water In the first phase of the project (REVENT I), on the deposition of activity at components a model was developed for re-entrainment of in the primary circuit. The thickness of the aerosols from the sump water in the contain- corrosion layers, their chemical composition, ment atmosphere. It showed that the way in and their semi-conductive properties were which droplets are carried over depends measured on selected specimens. strongly on the diameter of the bubbles at the containment surface and on the hydrodynamic 3. Development and testing of electrochemical conditions in the containment atmosphere. measurement devices for in-line measure- Knowledge of the bubble diameter is therefore ments under high-temperature water condi- an important element in the determination of tions. Of particular note here was the further the re-suspended mass in the sump. The development and use of electrochemical in- REVENT installation was modified in order to line methods to answer questions concern- carry out further checks on the re-entrainment ing the way in which surface layers on stain- model. Following this, it was shown that the less steels are built up (corrosion, deposition distribution of bubble diameters in the sump is of activity, semi-conductive properties of the independent of the pressure, within the range oxides). of pressures examined. For a pure steam atmosphere, cooling of the containment has no Furthermore, on-going experiments were car- influence on the re-entrainment factor. In con- ried out to assess the effects of dosing noble trast, re-entrainment increases with rising metals into the water on the behaviour of pressure in the containment. structural materials with regard to corrosion and contamination. Work was continued at PSI, in the laboratory 13.12 Melt-structure-water for material behaviour (LWV) with regard to the interactions during control of contamination. The Inspectorate supports this work and recognises the efforts severe accidents in being made to help minimise radiation fields LWRs; KTH, Stock- and contamination in nuclear power plants. holm, Sweden The research project is supported financially by six international and national organisations including the US-NRC, the Swedish nuclear

HSKAnnual report 1998 • Safety research 79 safety authority (SKI), the EU and the Inspec- for a Swiss nuclear power plant. The renewed torate. It is managed by the Royal Institute of analysis was carried out with various HRA Technology (KTH), Nuclear Power Safety, methods and took into account plant-specific Stockholm, Sweden. Three areas were pur- boundary conditions. The probabilities for the sued during the research year 1998: occurrence of mistakes, determined by PSl, were two to sixteen times higher than the 1. Interactions between the melt and the reac- original values. In addition to the quantitative tor pressure vessel (RPV). conclusions, numerous practical recommenda- In order to simulate creep and deformation tions were made for use of the different HRA of the RPV in the case of a severe accident, methods.The results will now be subjected to up to 20 I of superheated oxide melt (corium an external quality assessment. substitute) are heated up under pressure in "Errors of Commission" (EoC): in co-opera- a model reactor pressure vessel.The results tion with the German research institution for show measurable deformation and move- plant and reactor safety (GRS), methods pro- ment in the RPV.These valuable data on the posed for the analysis of EoC were evaluated. behaviour with regard to creep, and the abil- Dynamic simulation: the work on develop- ity to cool the RPV during a severe accident, ment of a dynamic simulation of operator be- form the basis for the derivation of theoreti- haviour was continued in co-operation with the cal models. STARS project. A newly developed interface was tested: this permits coupling of the 2. Interactions between the fuel and the cool- OPSIM operator model to the RETRAN code. ant. The concept for a future simulation model was This experiment is concerned with the ques- prepared and implemented. tion of how the melt and the coolant (water) In addition, PSl participates in several inter- mix and in what way the melt undergoes national HRA activities, such as the new HRA fragmentation during this. It has been task of the OECD working group 5 and the shown that the temperature of the water is "concerted action" for new HRA methods decisive for the size of the melt particles. which is supported by the EU. During 1998, the IAEA co-ordinated research programme on the 3. The ability of corium to spread and be topic of HRA was completed. cooled. In the period under review, various experiments were carried out on this topic. These 13.14 Collaboration in the showed that the melt collects primarily at OECD Haiden Reactor the point where it flows out, as a result of solidification. Project in the area of software verification This work in the area of accident research will and validation; HRR be continued. Haiden, BMorway The human/machine interface can be decisive 13.13 Human Reliability for the safety of technical installations. Among other things, formal methods and techniques Analysis; PSB, Viiligen to improve software quality are being investi- PSl has been working since the beginning of gated in the OECD research centre at Haiden 1997 on the "Human Reliability Analysis" (Norway) in the context of corresponding re- (HRA), which is supported jointly by the Inspec- search. The Inspectorate has delegated an torate, PSl and the Swiss nuclear power plants. employee to the Haiden project in order to The HRA considers the effect of human ac- obtain knowledge on formal software develop- tions on the course of events as a component ment and experience on its practical use. part of the probabilistic safety analysis (PSA). In the first task, a graphic editor was pre- Individual actions, which are of decisive impor- pared for an algebraic specification language, tance for the way in which an accident devel- developed earlier in the Haiden project, with ops, are analysed in the HRA and the probabil- the goal of making available an improved opera- ity for the occurrence of mistakes determined. tor interface for this. The following work was carried out during the With the new techniques, it was shown that second year of the project: the specifications for programmes can be pro- Renewed evaluation of the probabilities for duced in a more precise way than is possible the occurrence of mistakes during selected without a formal description. Furthermore, the actions of the operator in the context of a PSA formal specifications produced can be used

80 HSK Annual report 1998 • Safety research directly to define further requirements for the supplement to both neutron fluence measure- subsequent phases of software development. ments and calculations in Switzerland. It thus However, the introduction and use of the forms an important element in the fracture methods requires considerable effort. It took mechanics analyses of the safety of reactor a relatively long time for the users to become pressure vessels with regard to brittle fracture. acquainted with the formal techniques. The results obtained were documented in work reports, which are also available to mem- 13.16 Use of the two-dimen- bers of the OECD Halden project. In this project, the use of formal techniques will be sional transport code further investigated and developed. HELIOS in the OECD Halden project; HRR Halden, Norway 13.15 Retention and expan- For Switzerland, the international Halden re- sion of expertise on search project (HRP) in Norway is an important neutron f luence meas- pillar in the areas of development, know-how urement; PSI, Villigen transfer and participation in international research projects. In 1998, the Inspectorate once Determination of neutron fluences is essential again had a representative at the HRRThe goal in order to estimate the effect of neutron irra- of the work was, and is, the introduction of the diation on the reactor pressure vessel (RPV) in new computer code HELIOS for the calculation a nuclear power station. It is well known that and design of the core in the Halden test re- high-energy neutrons, which are created dur- actor (HBWR). ing the fission of fuel, can have a negative ef- The results obtained in the year under re- fect on mechanical properties such as, e.g., the view show that the HELIOS code permits a fracture toughness, the ductile-to-brittle tran- clear improvement in the modelling and evalu- sition temperature, and the yield strength of ation of the experiments. The precision of the ferritic RPV steels. In this context, it is impor- calculations allows a corresponding accuracy tant to know how the neutron fluence has af- to be attained in the prediction of measured fected the changes in mechanical properties data. The HELIOS code must be incorporated measured, since these result in a reduction of into the existing HRP infrastructure for the safety properties.This is particularly important measurement and evaluation of experimental as a criteria for the RPV operating conditions data so that new HBWR experiments, with (temperature before applying pressure to the their specific reactor environments, can be RPV), so that sufficient material toughness calculated rapidly and without too much effort. remains guaranteed over the whole opera- In part, this process of incorporation has al- tional lifetime of the RPV. In this context, such ready taken place. information is also important for pressurised The HELIOS code was used for the calcula- thermal shock (PTS) studies. It is possible to tion and design of a series of experiments, in determine the changes in mechanical proper- particular for a PSI material test using special ties of the RPV as a function of the neutron "inert matrix fuel" (IMF/MOX fuel). fluence, and thus of the operational history of the nuclear power plant, by evaluating RPV specimens from surveillance capsules. In addition to standard dosimetry, so-called "scratch 13.17 Simulation model for specimens" from the RPV can also be used. the analysis of tran- Such scratch specimens provide a type of "in- sients in the Swiss situ" neutron dosimetry and are thus an addi- reactors (STARS III); tional, independent measurement method. Furthermore, this niobium method (Nb-93) has PSI, Villigen the goal of verifying and, if necessary, correct- The Inspectorate participates in the STARS ing the neutron fluence results obtained from research project with the goal of enabling PSI reactor physics calculations. to carry out work which is of value in perform- The work carried out at PSI will now allow ing independent checks on fuel and plant be- the niobium method to be introduced as a haviour in the Swiss nuclear power plants. This standard work procedure, which has been sub- is of great importance to the Inspectorate, jected, in part, to quality assurance. since it is unable to carry out such tasks with In the opinion of the Inspectorate, the its own resources. method established at PSI provides a valuable

HSK Annual report 1998 • Safety research 81 In the year under review, the calculation meth- The knowledge gained from the first ods used for the KKG, KKM and KKL plants PHEBUS experiments, e.g., the relatively large were further refined and tested, whereby the release of iodine, is of value in understanding modelling in the RETRAN-3D code was, in part, the physical and chemical behaviour of fuel, of newly formulated and validated. Furthermore, released radioactive substances, and of core the basis was provided for an uncertainty structures in the case of a severe reactor ac- analysis by means of a test application in the cident. The areas focused upon in the investi- area of thermohydraulics. gations were iodine chemistry, stability of sil- Development and validation of the plant ver iodide in the sump and iodine from aerosol models was also continued. Modelling of the deposits. KKL plant is complete. Revision of the models The Swiss contributions included testing, at for the KKM and KKB plants is in progress and PSI, of special filters for the next experiment this will be started soon for the KKG plant.The and designing and putting into operation a new plant models were verified on the basis of con- beta isotope source. With this, iodine reactions crete examples, e.g., through recalculation of can now be investigated, and preparations several tests at increased power carried out in made for further experiments. KKL. Calculation of the cause of a hypothetical accident in KKG occurred as a special case for 13.19 Severe accident pro- use of the STARS model, since this was required to support a current, emergency train- gramme (CSARP); US ing exercise. ftlRC, Washington, USA The QA plan for the STARS project was ex- The Inspectorate participates in the interna- amined by the Inspectorate and will be revised, tional programme on severe accidents in nu- and subsequently tested, on the basis of the clear power plants which is also supported by Inspectorate's comments. the US nuclear regulatory authority (NRC). During the year under review, work was continued on hydrogen deflagration and on various 13.18 PHEBUS fission phenomena which could occur in the reactor pressure vessel (RPV) during a severe acci- products agreement; dent. Further important aspects are fuel/cool- PSB,VHIagen ant interactions, direct heating-up of the Switzerland participates in the international containment upon failure of the RPV, and cal- programme PHEBUS FP (fission products) in culations of the release of radioactive sub- Cadarache, France. In the framework of this stances into the environment (source term) to agreement, the release of radioactive products be expected in the case of a serious accident during a severe core meltdown accident is with failure of the containment. On the basis being experimentally investigated. of recommendations from international ex- The on-going PHEBUS experiments are in- perts, the investigations on RPV integrity and tended to validate the calculation codes for the ability to cool the RPV during a severe ac- severe accidents. cident will be continued.

82 HSK Annual report 1998 • Safety research 14. PSI Schools

The East sector of the Paul Scherrer Institute knowledge in the area of reactor physics. Four (PSI) houses two schools, namely the Reactor repetition courses, with a total of 18 partici- School and the School for Radiation Protection. pants from the Gosgen nuclear power plant, were also concerned with reactor physics, taking special account of MOX fuel assemblies, as 14.1 Reactor School are to be used for the first time in KKG.

The reactor school provides basic theoretical knowledge and advanced training to the staff 14.2 School for Radiation of the Swiss nuclear installations. In particular, the reactor school runs a federally recognised Protection technical school (TS) specialising in nuclear For several years, the PSI radiation protection power plant technology. The school is under school has offered multi-level courses that are the supervision of the Union of Swiss Electric- recognised by the authorities. In 1998, again ity Producers (VSE), the BBT and the Inspec- more than 3000 people have taken part in torate. It has seven full-time employees and teaching sessions concerned with radiation ten external lecturers. protection. Of these, about 76% came from In April 1998, three engineers from the the medical profession and emergency organi- Beznau nuclear power plant successfully com- sations. The new training courses for doctors pleted their basic training, and received aTS were completed with the examination of 110 engineering diploma. participants. In 1998, there were five full-time The courseT-30 started in January 1998 and teachers at the school for radiation protection. will end in April 1999. Three trainee reactor The teaching material was tailored according to operators from the Beznau nuclear power practical use for the participants (e.g. measure- plant, two trainee reactor operators from the ment technology, fire brigade issues, trans- Muhleberg nuclear power plant, as well as one port, laboratory work etc.). ETH and oneTS engineer from the Leibstadt Courses with a total of some 750 partici- nuclear power plant, who are intending to take pants were held for persons from the area up a career as shift technical advisors, will ab- supervised by the Inspectorate (nuclear power solve their basic theoretical training in this plants and PSI). It is worth mentioning that 16 course.In six repetition courses, a total of 56 employees of the Inspectorate were able to participants from the Beznau nuclear power profit from these radiation protection training plant have further increased their in-depth courses during the year under review.

HSK Annual report 1998 • PSI Schools 83 15. International aspects

Today, more than ever, nuclear safety is an in- Within the framework of various pro- ternational task. In order to attain high safety grammes of help for eastern countries, the standards world-wide, it is necessary to have western regulatory authorities are required to a consensus of states and this can only be support the new regulatory authorities of the attained via international co-operation. A pre- East European countries and the Union of In- condition for the attainment of this goal is that dependent Soviet States by means of national specialists from established regulatory authori- and international co-operative programmes. ties participate in a credible way in international The goal here is that these new authorities bodies such as the IAEA, the OECD-NEA and should be in a position to carry out their super- the EU. visory activities and their safety assessments New challenges for the regulatory authori- in an independent way, in accordance with in- ties arise as a result of the unavoidable finan- ternational standards. cial pressure on the companies operating nu- The Inspectorate, insofar as it is able to, has clear power plants because of deregulation of been active within the framework of these the market for electrical power. For example, manifold international responsibilities for many it must be ensured that the high safety stand- years. As an example, several bilateral and in- ard of the Swiss nuclear power plants is main- ternational programmes of work are briefly tained despite cost pressures. described below. The effectiveness of the work of the regulatory authorities can be increased through the intensive transfer of know-how, through the 15.1 "Convention on Nuclear comprehensive exchange of experience, and through mutual, specialist support in the solu- Safety" (CMS) tion of specific safety questions. The current, The Convention on Nuclear Safety (CNS), fundamental papers of the IAEA and the OECD which was ratified by Switzerland on Decem- emphasise the importance of strengthening ber 11, 1996, establishes the basic principles and extending regulatory co-operation. of nuclear safety at an international level. The For the above reasons, the Inspectorate es- goal of this convention is to attain and maintain tablished, in September 1998, a forum for regu- a high standard of nuclear safety world-wide, latory authorities from countries with small in order to protect the population and the en- nuclear programmes (NERS). The authorities vironment from radiation damage.The conven- from Argentina, Belgium, the Czech Republic, tion is binding for the signatories and is re- Finland, Holland, Hungary, the Republic of stricted to civil nuclear power plants. The Slovakia, Slovenia, South Africa and Switzer- signatories are required to respect the basic land form a body committed to the mutual ex- safety rules within their own countries. change of help and advice in the areas of nu- Adherence to the convention is evaluated by clear safety and radiation protection.This body periodic meetings. For these conferences, is concerned, in particular, with specific prob- each signatory must produce an CNS report in lems arising from the small nuclear pro- which it demonstrates how the convention has grammes in the individual member countries. been put into practice within its area of juris- The Inspectorate is also a member of the diction. At the conference, the reports are mu- newly established association of regulatory tually examined and discussed by the signato- authorities from western countries (WENRA). ries in country groups ("peer review"). The As its first task, WENRA is charged with pro- conclusions of the conference are published. ducing a report on the status of nuclear safety In Switzerland, it is the Inspectorate's re- in those countries who wish to join the EU, in sponsibility to prepare these CNS reports and the framework of the planned eastern expan- to present these to the other signatories in the sion, and who must also satisfy various pre- course of the above-mentioned conferences. conditions, with regard to nuclear safety, in The scope and degree of detail of the status order to do this. In the year under review, the reports are established by the signatories in Inspectorate was not able to participate in the form of a guideline at a preparatory meet- WENRA meetings for priority reasons. ing before the conference. The report submit-

HSK Annual report 1998 • International aspects 85 ted by Switzerland to the IAEA on September tional law with regard to activities involving 23, 1998 adheres in its structure to the conven- spent fuel elements and radioactive waste. tion on nuclear safety, as required by the guide- Furthermore, the signatory countries commit line, and reports on the tangible safety rules themselves to periodic reporting on the extent laid down in articles 6 to 19 of the CNS. In sum- to which the specifications have been adopted, mary, the following areas are covered: and to the backfitting of installations, which do - existing nuclear power plants; not satisfy the requirements of the convention. - framework for law-making and enforce- Under the pre-condition of ratification by the ment; Swiss parliament, Switzerland already put its - suitable and independent, official authorities signature to this convention on September 29, for nuclear safety; 1997. The legal provisions and administrative - primary responsibility of the licence holder structures necessary for adoption of the com- for safety in his plant; mon convention, and for fulfilment of the com- - pre-eminence of safety and consideration of mitments resulting from this, are essentially human factors during the operation of nu- already in place. clear power plants; In 1998, the Federal Office of Energy pre- - quality assurance measures and systematic pared a submission to parliament in connection evaluations of safety during the construc- with ratification of the common convention. In tion, commissioning and operation of nu- parallel to this, preparations were made in Vi- clear power plants; enna with regard to the procedures for mutual - adherence to the basic principles of radia- checking and, in particular, the structure of the tion protection; reports to be submitted by the signatory coun- - emergency preparedness; tries. The common convention is not yet in - measures to guarantee safety during the force since the necessary number of choice of site, design, construction and op- ratifications has not yet been reached. eration of nuclear power plants. In a status report, available under www.hsk.psi.ch, it was confirmed that the nu- 15.3 Bilateral contacts with clear safety convention (CNS) is fulfilled in Switzerland. In his accompanying letter, federal other countries councillor Leuenberger gives the assurance 15.3.1 Germany that Switzerland will also continue to follow the The German-Swiss Commission on the Safety goals of the convention to their full extent in of Nuclear Installations (DSK) held its 16th future. Switzerland remains capable of learning meeting in St.Gallen in October 1998. On this in the safety area too, and prepares sugges- occasion, the two delegations informed each tions for improvement which are based on the other about the most important developments, current status of science and technology. activities, events, new codes, as well as organi- The first conference to check on application sational or legal changes. The four bilateral of the CNS took place in April 1999 at the IAEA working groups (AG) reported on their activities in Vienna. in the previous year, which involved the following key topics: - AG1 - Safety of installations: status and 15.2 Waste convention use of probabilistic safety analyses, corrosion damage to fuel assemblies, and cracks The final text of the "Convention on Safety in in core internal components. Handling Spent Fuel Elements and Safety in - AG2 - Emergency protection: evaluation of Handling Radioactive Waste", together known the KKL emergency exercise FORTUNA, as the "waste convention", was agreed upon in improvements to the channels of communi- the framework of a diplomatic conference in cation, and revised federal emergency pro- Vienna, in September 1997. The aims of this tection concept. common convention are to achieve and main- - AG3 - Radiation protection: monitoring of tain, world-wide, a high level of safety, to as- emissions from nuclear power plants, 18th sure effective protective measures against report on radiological monitoring in the vicin- possible dangers from radioactivity, and to pre- ity of KKL, and detection of the caesium-137 vent the occurrence of accidents. This com- cloud, which arose from a Spanish steel- mon convention follows on from the Conven- works. tion on Nuclear Safety (see also Section 15.1). - AG4 - Radioactive waste disposal: re- It establishes binding commitments under in- quirements on waste products, ZWILAG, ternational law for the transfer of internation- and contamination during the transportation ally accepted technical specifications into na- of depleted fuel assemblies.

86 HSK Annual report 1998 • International aspects The mandate of the four working groups was, (each processor is allocated its own memory), again, reconfirmed. parallel virtual machine (PVM) is used as a com- In the year under review, the intensive ex- puting procedure. The Inspectorate has del- change of ideas and information, practised for egated one member of staff to the US NRC several years between the Inspectorate and (Washington DC) for one year in order to pur- the supervisory authority of the German State sue this common computer project. of Bavaria (Bavarian State Ministry for Devel- opment and for the Environment - BStMLU), 15.3.4 Russia as well as its expertsTUV ET (TUV Energy and The SWISRUS project is intended to provide a SystemTechnology), was continued by means team of experts from the recently established of a one-day meeting at the Inspectorate. Russian regulatory authority GOSATOM- Among others, topics of current interest were NADZOR (GAN) with modern analytical tools to the transportation of depleted fuel assemblies, assess safety in their own nuclear power the use of austenitic materials in boiling water plants, and to train these experts in the use of reactors, questions arising in the supervisory these tools. The project is financed by the Di- area from operational experience of the plants, rection for Development and Co-operation ageing surveillance, probabilistic safety analy- (DEZA) and administered by the Inspectorate ses, and questions of safety culture. Such ex- with the support of western experts. pert meetings, held in an open atmosphere, Training of the Russian experts is being car- are of interest and use for both sides and will ried out by means of a probabilistic safety be continued in the future. analysis (PSA) for a 1000 MWe pressurised water reactor. This PSA consists of a compre- 15.3.2 France hensive safety analysis taking into account all The French-Swiss Commission on the Safety the parameters influencing safety of the plant, of Nuclear Installations (CFS) held its 9th meet- including human factors. The result of this ing in Mulhouse in June 1998. Both delega- analysis includes the consequences and fre- tions exchanged information about particularly quency of events and accidents, i.e. the risk important events, the occurrences of contami- applying to the plant. Furthermore, potential nation during the transportation of depleted weak-points in the plant can be identified on fuel assemblies, the definitive mothballing of the basis of these results and the necessary Superphenix, the caesium cloud from southern improvements indicated. By carrying out a PSA Spain, and the newest developments in the study for the Novovoronezh-5 plant, it can be area of disposal of radioactive waste. The pro- ensured that what is learned does not just re- gramme of the bilateral working group "inspec- main a "paper exercise", but is of concrete use tions croisees" was approved and supported. and enables the safety of the plant to be im- Following this, the CFS visited the Fessenheim proved on the basis of the results and knowl- nuclear power plant. edge obtained. During 1998, the first joint inspections (in- The first phase of the project was com- spections croisees) were carried out in Gosgen pleted in the spring of 1997 and concerned the and Bugey. It was confirmed that much can be risk of core damage arising from internal learned from this procedure and the pro- events.This study was examined at the end of gramme will be intensified. 1998 by an international group of experts under the direction of the IAEA.The result of this 15.3.3 United States of America (USA) examination was positive and motivated the SCDAP/RELAP5 is an integrated computer Russian specialists who were involved. The code, developed by the US N RC, for the simu- recommendations and suggestions of the ex- lation of a core meltdown in the reactor pres- pert group will be taken into account and the sure vessel (RPV). SCDAP models the core PSA model improved and modified in accord- meltdown itself, whereas RELAP5 calculates ance with these. The final model will then be the thermohydraulic boundary conditions exist- installed in the plant, so that the plant experts ing in the RPV. In the context of a common are able to carry out their own checks on safety project between the US NRC and the Inspec- on the basis of the PSA investigations. torate, it is intended to separate SCDAP from In a second phase of the project, begun in RELAP5 and then to re-couple both independ- the middle of 1997, external incidents, such as ent parts of the code using a newly developed, earthquakes, fires, flooding etc., are also being general interface. The idea here is to enable investigated. The main emphasis to date has SCDAP also to be used in future together with been on collating and evaluating the data nec- other thermohydraulic codes, for example with essary for such analyses. Among other things, TRAC-M. In order to be able to use powerful, several plant walk-downs were necessary for parallel computers with distributed memories this. The database existing to date solely for

HSK Annual report 1998 • International aspects 87 the analysis of fire dangers already contains its investigations even after the end of the several thousand entries, e.g., details on the project, the Safety Analysis Group has been fire susceptibility of individual rooms, fire pro- established as a separate department within tection measures, and cable ducting. the nuclear regulatory authority of the Repub- During the second phase of the project, lic of Slovakia (Urad Jadroveho Dozoru, UJD) which will continue up to the middle of 2000, reporting directly to the director. The Safety a stage two PSA analysis will be carried out. On Analysis Group consists of 7 scientists, who the one hand, this will enable the behaviour of have been trained by Swiss and American spe- the containment during severe accidents to be cialists in workshops and seminars carried out evaluated and, on the other hand, it will provide during the project. The recent examination of information on the amount of nuclide-specific the organisation, work methods and specialist activity set free in the course of an accident. competence of the Slovakian authority, carried The latter information is necessary in order to out by the IAEA, emphasises the importance assess the risk in the vicinity of the nuclear of this group within the authority and their power plant. substantial contribution to the safety of the When the results of the second phase of Slovakian nuclear power plants. The project the project are available, the Russian project goals mentioned above were attained. Today, team will be in possession of all the necessary the competence of the Slovakian authority is knowledge and the appropriate tools in order also recognised internationally and the Safety to conduct a comprehensive risk analysis. Analysis Group is now capable of carrying out complex safety analyses in an independent 15.3.5 Republic of Slovakia way. Within the framework of Swiss-Slovak Co-operation (SWISSLOVAK project), which is fi- 15.3.6 Finland nanced by the Direction for Development and In May 1998, the general director of the Finn- Co-operation (DEZA), the following aims were ish regulatory authority (STUK) visited the In- followed during the year under review: spectorate in order to intensify the existing co- - support during institutional reshaping of the operation and the exchange of specialist Slovakian nuclear regulatory authority to a information. During his visit the possibility of modern, competent organisation, which is exchanging staff between the two supervisory integrated into the international regulatory authorities was agreed upon. Furthermore, it network; was suggested that the development of guide- - transfer of specialist technical knowledge lines in the area of digital instrumentation and and management know-how to the new control technology (see also Section 12.1) Slovakian nuclear regulatory authority; should be the subject of mutual specialist dis- - creation of a group of young engineers and cussions and possible harmonisation. scientists within the nuclear regulatory au- In November, two PSA specialists from the thority and their training in the area of deter- Finnish regulatory authority visited the Inspec- ministic and probabilistic safety analysis torate. Various aspects and topics of PSA work ("Safety Analysis Group"). were discussed intensively over two days and Using modern methods, the above-mentioned intensified co-operation was proposed. In this group of young engineers and scientists has context, a PSA expert from the Finnish author- analysed the safety of the Bohunice and ity will spend one year working at the Inspec- Mochovce nuclear power plants and checked torate during 1999. for potential weak-points. In order to continue

88 HSK Annual report 1998 • Internationa] aspects Appendix A

Tables Table A1 Performance of the Swiss nuclear power plants (1998) 91 Table A2 Numbers of licensed personnel and grand total of personnel in the Swiss nuclear power plants as of end 1998 91 Table A3 Classified events 1998 92 Table A4a Summary of the releases of radioactive materials to the environment in 1998 and the resulting calculated individual doses 93 Table A4b Releases of the Swiss nuclear power plants in the last 5 years, compared to the release limits 96 Table A5a Nuclear power plants: Whole-body doses from external irradiation in 1998. Number of persons and average annual dose 97 Table A5b Research installations and nuclear power plants: Whole body doses from external irradiation in 1998. Number of persons and average annual dose 98 Table A6a Nuclear power plants: Whole-body doses from external irradiation in 1998. Annual collective doses in Person-millisievert 99 Table A6b Research institutions and nuclear power plants: Whole-body doses from external irradiation in 1998. Annual collective doses in Person-mSv 100 Table A7 Whole body doses from external irradiation in 1998. Number of individuals grouped according to age and sex. All NPP and research personnel, own and external considered 101 Table A8 Hand and foot doses, 1998: NPPs and research 102

Table A9 Committed effective dose E50, resulting from incorporation in 1998: NPPs and research 103 Table A10a Number of persons (plant own personnel in NPPs and research) whose accumulated total dose (life-dose) due to occupational exposure up to the end of 1998, exceeded 100 mSv.Totals and distribution according to dose interval and installations 104 Table A10b Number of persons (plant own personnel) whose accumulated total dose (life-dose) due to occupational exposure up to the end of 1998, exceeded 100 mSv (NPP and PSD.Totals and distribution according to age and dose interval 104 Table A11 Radioactive waste at the NPP's and PSI 105

Figures Figure A1 Availability and load factor 1989-1998 106 Figure A2 Notifiable, classified events 1989-1998 107 Figure A3 Number of reactor scrams (unplanned), 1989-1998 108 Figure A3a Causes for classified events in the Swiss NPPs per year 1989-1998 109 Figure A3b Causes of unplanned reactor scrams per year 1989-1998 109 Figure A4 Fuel element defects (number of elements) 1988-1998 110 Figure A5 Annual collective doses (Person-Sv/year) in the NPPs, 1980-1998 111 Figure A6 Annual collective doses (Person-Sv/year) in the NPPs: 1969-1998 112

HSKAnnual report 1998 • AppendixA 89 Figure A7 Number of persons with an individual annual whole-body dose over 20 mSv in theNPPs: 1984-1998 113 Figure A8 Average annual dose (mSv) of own and external personnel of the nuclear power plants: 1980-1998 114 Figure A9 Number of individuals (own personnel) of the nuclear power plants who at the end of each of the years between 1980 and 1998 have accumulated integrated doses (life-dose) exceeding 200 mSv 115 Figure A10 Calculated dose for the most affected person (adult) in the vicinity of the nuclear power plants: 1978-1998 116 Figure A11 Local dose rate in 1998, as measured by the MADUK probes 117

90 HSK Annual report 1998 • Appendix A Table A1 Performance of the Swiss nuclear power plants (1998)

KKB 1 KKB 2 | KKM KKG KKL

Thermal energy produced [GWh] 9885 8693 | 8197 24335 25094

Net electrical energy supplied [GWh] 3183 2718 \ 2660 7781 8046

Thermal energy supplied [GWh] 149.9 1.2 \ 1.4 155 -

Availability factor1 [%] 100 88.9 \ 90.0 93.4 92.9

Non-availability due to annual - 11.1 i 9.8 6.6 7.1 revision [%]

Load factor2 [%] 99.7 87.0 : 85.3 92.8 89.2

Number of unplanned scrams 0 0 i 1 0 0

Other unplanned shutdowns 0 0 0 0 0

Load reductions due to events or ; 2 2 1 1 1 failures (>10% PN)

1 Availability (in %): Time which the nuclear power plant was in use or in a usable condition. 2 Load factor (in %): Energy produced relative to the nominal power and a hundred percent availability.

Table A2 Numbers of licensed personnel and grand total of personnel in the Swiss nuclear power plants as of end 1998. In parentheses: 1997 values.

Job title KKB 1+2 KKM KKG KKL

B operator 23 (17) 11 (13) 9 (9): 12 (16)

A operator 16 (17) 13 (9) 20 (21); 11 (11)

Shift chief and deputy 21 (23) 11 (10) 20 (16): 18 (18)

Picket & operations engineers 11 (10) 8 (8) 12 (12) ; 15 (10)

Radiation protection controller 4 (5) 5 (6) 5 (5): 9 (9)

Radiation protection chief controller 5 (6) 6 (5) 4 (4): 6 (6)

Total personnel 459 (461) 291 (292) 377 (377) | 418 (406)

HSK Annual report 1998 • Appendix A 91 Table A3 Classified events 1998

Classification Installation / Date Event according to NPP INES Insufficient level of the borated water tank at startup after 15.05.1998 ;KKB2 0 refuelling Reactor scram due to a high temperature in the torus, 23.06.1998 : KKM caused by an erroneously opened blowdown valve Failure to start of a diesel emergency supply unit during a 17.08.1998 KKL function test Not closing of an isolation valve in the reactor water 24.10.1998 KKL sampling system, during a function test A non-allowable deviation from the set values given in the 04.11.1998 KKB 1 requirements of the technical specifications on two main steam pressure switches

Note; All of the above events are, according to the inspectorate's Guidelines R-15 and R-25, in the Class B

92 HSK Annual report 1998 • Appendix A Table A4a Summary of the releases of radioactive materials to the environment in 1998 and the resulting calculated individual doses. (See footnotes at the end of the tables).

Release limits Calculated effective (AL) according Actual releases2 equivalent doses3 to regulation1 NPP Medium Types of releases Bq/year \ Percent Adult Child (±50%) : of limit mSv/year mSv/year

Waste Nuclide mixture (without tritium) 4-10" 1.5-109 : 0.4% <0.001 <0.001 Water (36844m3) Tritium 7-10'3 1.1-10" : 15.7% <0.001 <0.001 KKB1 15 12 : and Noble gases MO 3.0-10 ; 0.3% <0.001 <0.001 KKB2 Aerosols 6-109 i <01% <0 001 <0 001 Exhaust air without 1-131, half life >8 days lodine-131 4-109 9.2-106 \ 0.2% <0.001 <0.001

Carbon-14 - 4.0-1010 i 0.0011 0.0018

Waste Nuclide mixture (without tritium) 4-10" 5.3-109 \ 1.3% <0.001 <0.001 Water (9520m3) Tritium 2-1013 4.3-10" 2.2% <0.001 <0.001 16 KKM Noble gases 2-10 2.M017 0.1 % <0.001 <0.001

Aerosols 2-10™ - <0.1% 0.0071 0.0055 Exhaust air without 1-131, half life >8 days lodine-131 2.10™ - <0.1% <0.001 <0.001

Carbon-14 - 2.0-10" - <0.001 0.0011

Waste Nuclide mixture (without tritium) 2-10" _ <0.1% <0.001 <0.001 Water 3 13 (7528m ) Tritium 7-10 1.3-1013 18.6% <0.001 <0.001 i i Noble gases MO16 1.2% <0.001 <0.001 total measurement beta Sto-io* KKG Aerosols M010 - <0.001 <0.001 Exhaust air without 1-131, half life >8 days lodine-131 7-109 5.7-10' 0.8% <0.001 <0.001

Carbon-14 - 1.0-10" - <0.001 0.0011

Waste Nuclide mixture (without tritium) 4-10" _ <0.1% <0.001 <0.001 Water (15226m3) Tritium 2-1013 5.9-10" 3.0% <0.001 <0.001

Noble gases 2-1015 5.3-1012 0.3% <0.001 <0.001 KKL Aerosols 2-1010 2.9-10' 0.1% <0.001 <0.001 without 1-131, half life >8 days Exhaust air lodine-131 2-1010 4.3-108 2.2% <0.001 <0.001

Carbon-14 - 4.1-10" - 0.0021 0.0034

HSK Annual report 1998 • Appendix A 93 t Table A4a (Continued) Summary of the releases from the Paul Scherrer Institute in 1998 and the calculated individual dosis of the population.

Radioactive Shed Main Central waste containing Waste stack Incinerator Saphir BZL stack Injector I Injector II Total PSI treatment Tritium water East West building equipment

Releases in waste water2-4 [Bq] Nuclide mixture (without tritium) ------1.5-108 1.5-108 Tritium 8.7-109 8.7-109 Releases to exhaust air2-4 [Bq] Noble gases and other gases 1.6-1012 8.0-1013 1.1-1010 1.3-10" 8.2-1013 BetaVGamma-Aerosols (without Iodine, 5.7-109 1.0-108 7.5-109 5.0-105 1.3-1010 half-life >8 hrs.) Alpha-Aerosols 2.4-106 2.4-106 Iodine (l-131-equ.) 1.6-109 9.2-106 4.8-107 1.4-105 1.7-109

9 10 7 10 Tritium (tritiated Water) 1.9-10" 7.0-10 3.4-10 1.6-10" 1.0-10 5.1-10" 4.3-10 II I 9.4-10" Annual dose [mSv/year] for:

Adults 0.0003 0.0002 <0.0002 <0.0002 <0.0002 0.0022 <0.0002 <0.0002 <0.0002 <0.0002 <0.003 Infants 0.0009 0.0003 <0.0002 <0.0002 <0.0002 0.0023 <0.0002 <0.0002 <0.0002 <0.0002 <0.004 Part of source-related dosis guideline 0.5% 0.1% <0.1% <0.1% <0.1% 1.1% <0.1% <0.1% <0.1% <0.1% <2% Table A4a (Footnotes)

1 Release limits according to the operating licence effective for the respective nuclear installation. The release limits have been laid down to keep the off-site exposure of the critical population group in the vicinity below 0.2 mSv/year. For the Paul Scherrer Institute (PSI) the releases are directly limited to 0.2 mSv/year via the source-related dosis approximate value according to a permission 6/97.

2 The measurement of the releases is carried out according to the requirements. ,,For the release of radioactive materials and the surveillance of radioactivity and direct irradiation in the environment of the ..." (given NPP) and the PSI.The accuracy of the measurements is about ±50%. Releases below 0.1 % of the annual release limits are regarded by the Inspectorate as not being relevant.

3 Annual dose is calculated for persons who live permanently at the critical location and take their total food produced at the location and all water requirements at a location downstream from the NPP. The calculations are done according to the Inspectorate's Guideline HSK-R-41; this contains a model and the defined parameters to use. Doses less than 0.001 mSv - equivalent to the dose accumulated in 10 h due to natural radioactivity - are, as a rule, not recorded. At PSI, the annual dose of the complete installation is shown as a total overall the release points although the critical locations of the single release points do not in general, come together.

4 By the type of release, the following is noted: Waste water: Releases in Bq/year are normalised to a reference exemption limit (LE) of 200 Bq/kg. The LE values for the individual nuclides are taken from Appendix 3 of the radiological protection ordinance (StSV). A LE value of 200Bq/kg corresponds to a reference nuclide with an ingestion dosis-factor of 5-10"8Sv/Bq Noble gases: Radioactive releases in Bq/year, normalised to a reference CA value of 2-105 Bq/m3, are given. The CA values for the noble gas nuclides are taken from Appendix 3 of the radiological protection ordinance (StSV). A CA value of 2-105 Bq/m3 corresponds to a reference nuclide with an immersion dosis-factor of 4.4-10"7 (Sv/year)/(Bq/m3). For NPP Gosgen (KKG), a {J-total measurement was carried out for balancing the noble gases (see the values in brackets); for the equivalent-exchange calculation, for this case, a mixture of 80% Xe-133, 10% Xe-135and 10% Kr-88 was taken.This mixture was also taken for calcu- lating the dose. Gases: At the PSI it is mainly the nuclides C-11, N-13, 0-15 and Ar-41 whose half-lifetimes are less than two hours. For the releases here, it is the sum of the radioactivity, without stand- ardising to a reference value, which are given. Aerosoles:The releases given correspond to the total of aerosol activity without standardis- ing to a reference value. The dose contribution of aerosols with a half-life time less than 8 days is negligible for the nuclear power plants. For NPP Beznau (KKB), a mixture of 50% Co-60 and 50% Cs-137 is taken for the dose calculation from aerosols. In the case of NPP Muhleberg (KKM), the main contribution to the dose stems from soil-de- posited aerosols which were unintentionally released in 1986.The dose contribution through aerosol releases in 1998 is small compared to this and lies within the order of magnitude of other Swiss nuclear power plants. Iodine: At PSI, the release as l-131-equivalent through a weighted total of the activity of the released iodine nuclides is given. Here the weighting factor is derived from the relationship between the ingestion-factor of the particular nuclide to that of the ingestion-factor from 1-131. The ingestion-dosis factors are taken from the StSV. Carbon-14:The C-14 releases given are based at NPP Leibstadt (KKL) on real measurements; by KKB, KKM and KKG they are based on measurements from previous years.

HSKAnnual report 1998 • AppendixA 95 Table A4b Releases of the Swiss nuclear power plants in the last 5 years, compared to the release limits

Exhaust air Noble gases

KKB KKG KKL KKM NPP

10'

Limit

Exhaust air

Iodine 108 .2

7 I -ftrr 1-10 L I I94 95 96 97 94 95 96 97 98 94 95 96 97 98 94 95 93 97 98 KKB KKG KKL KKM NPP

Limit -- --- Limit r 10' Limit Limit 13 10

CD m 12 10 lx Waste water OQ Tritium in waste water it *tM It: — 10 leas e CD I - 1010 rr P S3! 10* 94 95 96 97 IIilU [1 KKB 34 95 96 97 98 94 95 96 97 98 94 95 96 97 98 KKG KKL KKM NPP

CD CD

•& Waste water CO Other liquid-type releases _CD CD CC

KKB KKG KKL KKM NPP

96 HSKAnnuai report 1998 • Appendix A Table A5a Nuclear power plants: Whole-body doses from external irradiation in 1998. Number of persons and average annual dose

1 Dose distribution KKB 1+2 KKG KKL KKM Total NPP [mSv] E F E+F E F E+F E F E+F E F E+F E F E+F

0.0-1.0 271 484 755 218 392 610 228 674 902 164 519 683 881 1642 2523 > 1.0-2.0 57 37 94 22 46 68 54 74 128 36 138 174 169 273 442 > 2.0-5.0 38 41 79 29 39 68 67 85 152 52 106 158 186 260 446

6 64 149 CO > 5.0-10.0 2 8 23 29 52 15 18 33 20 25 45 85 > 10.0-15.0 1 1 3 3 3 3 5 3 8 9 8 17 > 15.0-20.0 1 1 1 1

• - > 20.0-50.0

> 50.0

Total persons 373 564 937 296 506 802 364 854 1218 277 791 1068 1310 2268 3578 Average per 0.8 0.4 0.6 1.3 0.9 1.0 1.2 0.8 0.9 1.6 1.1 1.2 1.2 0.9 1.0 person [mSv]

1 Individuals from external external personnel having worked successively in several installations are counted here only once. E = plant own personnel, F = external personnel; TL-dosimeters used in all plants.

CD CO CO Table Abb

Research installations and nuclear power plants: Whole body doses from external irradiation in 1998. Number of persons and average annual dose

Dose distribution University of Total Total NPP Total NPP und PSI EPFL imSv] Basel Research1 E+F Research2

0.0-1.0 1235 10 4 1250 2523 > 3663

> 1.0-2.0 43 43 442 485

> 2.0-5.0 27 27 446 j 473

> 5.0-10.0 3 3 149 • 152

I > 10.0-15.0 17 17 (7) > 15.0-20.0 1 i 1

> 20.0-50.0

> 50.0

Total persons 1308 10 4 1323 3578 \ 4791

Average per 0.2 0.0 0.0 0.2 1.0 ; 0.8 person [mSv]

1 This column contains the value for one person (0.9 mSv annual dose) working at the decommissioned experimental installation at Lucens. 2 Individuals from external external personnel having worked successively in several installations are counted here only once. E = plant own personnel, F = external personnel; TL-dosimeters used in all plants. Table A6a Nuclear power plants: Whole-body doses from external irradiation in 1998. Annual collective doses in Person-millisievert (Person-mSv)

KKB 1+2 KKG KKL KKM Total NPP1 Dose distribution [mSv] E F E+F E F E+F E F E+F E F E+F E F E+F

0.0-1.0 62.6 64.6 127.2 44.4 57.3 101.7 41.5 135.3 176.8 30.7 107.5 138.2 179.2 320.1 499.3

> 1.0-2.0 81.1 53.4 134.5 33.1 63.1 96.2 779 111.9 189.8 576 201.7 259.3 249.7 395.8 645.5

> 2.0-5.0 108.9 120.0 228.9 979 123.6 221.5 203.0 264.9 467.9 153.7 335.4 489.1 563.5 824.1 1387.6 in > 5.0-10.0 32.9 11.7 44.6 149.3 197.6 346.9 97.1 128.8 225.9 144.2 164.0 308.1 423.4 571.4 994.8 7 > 10.0-15.0 10.6 10.6 38.6 38.6 35.0 35.0 55.9 34.9 90.8 105.1 92.9 198.0

> 15.0-20.0 16.0 16.0 16.0 16.0

> 20.0-50.0

> 50.0

Total [person-mSv] 296.1 249.7 545.8 379.3 441.6 820.9 419.5 675.9 1095.4 442.0 843.5 1285.5 1536.9 2204.3 3741.2

Highest individual dose 10.6 6.6 10.6 16.0 9.2 16.0 7.5 12.7 12.7 14.6 13.0 14.6 16.0 13.0 16.0 [mSv]

1 External personnel that work in more than one installation are only counted once. Through the addition of the various doses collected in different NPPs, or the elimination of individual doses that have been reported on more than once, the collective doses change only slightly. E = plant own personnel, F = external personnel

CD o o Table A6b Research institutions and nuclear power plants: Whole-body doses from external irradiation in 1998. Annual collective doses in Person-mSv

Dose distribution • University of ; Total Total NPP Total NPP und PS I EPFL 1 [mSv] Basel ! Research E+F '•• Research2 0.0-1.0 80.2 0.4 ! ° ! 81.5 499.3 ! 570.9 > 1.0-2.0 64.0 64.0 645.5 709.0

> 2.0-5.0 78.5 i i 78.5 1387.6 i 1466.7

> 5.0-10.0 19.4 19.4 994.8 • 1014.2

> 10.0-15.0 198.0 1979

> 15.0-20.0 16.0 16.0 > 20.0-50.0 >50.0

Total 242.1 0.4 ; o.o ! 243.4 3741.2 3974.7 [person-mSv]

Highest individual 8.3 0.2 ; o 8.3 16.0 16.0 dose [mSv] :

' This column contains the value for one person (11 mSv annual dose), working at the decommissioned Lucens nuclear power plant. 7 External personnel that work in more than one installation are only counted once. Through the addition of the various doses collected in different NPPs, or the elimination of individual doses that have been reported on more than once, the collective doses change only slightly. E = plant own personnel, F = external personnel Table A7 Whole body doses from external irradiation in 1998. Number of individuals grouped according to age and sex. All NPP and research personnel, own and external considered.

Dose distribution 16-18 19-20 21-30 31-40 41-50 51-60 >60 [mSv] years years years years years years years M F M F M F M F M F M F M F Total 0.0-1.0 19 378 10 645 19 706 17 592 6 125 1 2523 > 1.0-2.0 77 1 140 1 138 74 8 442 > 2.0-5.0 67 155 1 146 68 9 446

CO 7 > 5.0-10.0 19 56 46 24 4 149 > 10.0-15.0 6 8 3 17 > 15.0-20.0 1 > 20.0-50.0 >50.0

> •o Total persons 6 21 541 11 1003 21 1044 17 761 6 146 1 3578 Average per 0.39 0.27 0.97 0.29 1.30 0.39 1.14 0.09 0.81 0.06 0.54 0.01 1.05 person [mSv] Collective dose 2.3 5.6 525.4 3.2 1302.1 8.3 1194.4 1.6 618.4 0.4 79.4 0.0 3741.2 [person-mSv]

M = male, F = female o Table A8 Hand and foot doses, 1998: NPPs and research

Total NPP KKB 1+2 ; KKG ; KKL KKM Total NPP PSI Dose distribution and PSI [rnSv] E F E+F E F E+F : E F E+F E F E+F E F E+F E+F 0-25 10 2 12 2 2:2 5 7 i 11 11 22 25 18 43 108 151 > 25-50 2 2 > 50-75 > 75-100 1 1 1 1 1 > 100-150 > 150-200 > 200-250 > 250-300 > 300-350 > 350-400 > 400-450 > 450-500 > 500 Total persons 10 2 12 i 2 2 ; 2 5 7 12 11 23 26 18 44 110 154

E = plant own personnel, F = external personnel Table A9

Committed effective dose E50, resulting from incorporation in 1998: NPPs and research

Committed effective dose Total NPP KKB 1+2 KKG KKL KKM Total NPP PSI and PSI Dose distribution LL J [mSv] E F E+F F E+F LJ J F E+F E F E+F E F E+F E+F 319 501 820 282 479 761 363 811 1174 263 750 1013 1227 2541 3768 358 4126 > 1.0-2.0

X > 2.0-5.0 CO > 5.0-10.0 > 10.0-15.0 > 15.0-20.0 > 20.0-50.0 >50.0 Total persons 319 501 820 282 479 761 363 811 1174 263 750 1013 I 1227 2541 3768 358 4126

Persons by which in the screening mesurement did not exceeded the predetermined threshold are noted in thisTable in the E6U dose distribution between 0-1.0 mSv.

o Table A 10a Number of persons (plant own personnel in NPPs and research) whose accumulated total dose (life-dose) due to occupational exposure up to the end of 1998, exceeded 100 mSv.Totals and distribution according to dose interval and installations.

Dose distribution Total : Total NPP KKB 1+2 KKG KKL KKM PSI [mSv] NPP ! and PSI > 100-150 36 16 15 27 94 : 20 114 > 150-200 26 15 5 21 67 ; 7 74 > 200-250 27 : 6 18 51 ; 5 56 > 250-300 16 2 1 7 26 1 27 > 300-350 14 : 1 4 19 : 1 20 > 350-400 5 3 8 8 > 400-450 5 \ 4 9 9 > 450-500 4 3 7 7 > 500-550 3 i 4 7 ; 7 > 550-600 1 ; 1 1 : >600 1 I 1 1 Total persons 138 40 21 91 290 34 324 including individuals who left during the course of 1998

Table AlOb Number of persons (plant own personnel) whose accumulated total dose (life-dose) due to occupational exposure up to the end of 1998, exceeded 100 mSv (NPP and PSI).Totals and distribution according to age and dose interval.

Dose distribution 21 -30 31 -40 41 -50 51 -60 >60 Total NPP [mSv] years years years years years and PSI > 100-150 * - "' 21 43 39 11 114 > 150-200 7 31 30 6 74 > 200-250 3 13 27 13 56 > 250-300 1 10 13 3 27 > 300-350 6 12 2 20 > 350-400 6 2 8 > 400-450 1 8 9 > 450-500 1 6 7 > 500-550 2 5 7 > 550-600 1 1 >600" 1 Total persons 32 107 147 ^ 38 324 including individuals who left during the course of 1997

104 HSK Annual report 1998 • Appendix A Table A11 Radioactive waste at the NPP's and PSI. (For PSI are also included here waste from medicine, industry and research); volume in m3

unconditioned conditioned Amount Total3 Production2 Total3 arising2 PSI 122 252 66 814 KKB 95 100 6 917 KKM 139 500 84 392 KKG 48 57 13 262 KKL 82 158 39 1161 Total 486 1067 208 3546

1 A reduction in volume occurs during conditioning burnable and compressible wastes 2 Volumes in reporting period, 1998 3 Volumes in storage facilities of the NPP's and PSI at the end of 1998

HSK Annual report 1998 • Appendix A 105 Figure A1

Availability and load factor 1989-1998 (in %)

100 Hi availability

95 CM :_J load factor 90 KKB 1, 2 85 -m

80 75 I 70 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998

100 availability 95 load factor 90

KKM 85 .. jtf

80 -{ r

70 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998

100 - I availability 95 oad factor 90 -M-fJJ-X, I:

85 r—i \ L KKG 1: ; : ; L__; 80 •-I| '"1 i E 75 i ; [ -- -.J I I : J U t 70 ;-a '•_.. [.,k iia : ! 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998

100 I availability 95 1 load factor 90 KKL 85 80 -! H 75 j 1 70 J 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998

106 HSK Annual report 1998 • Appendix A Figure A2 Notifiable, classified events 1989-1998 12 : M KKB 1: only events B 10 r 3 KKB 2: only events B

KKB 1, 2

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998

12 — I only events B 10 i—

KKM

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998

12 r I only events B 10

KKG

2 i-

0 t I 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998

KKL

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998

HSK Annual report 1998 • Appendix A 107 Figure A3 Number of reactor scrams (unplanned), 1989-1998

1KKB 1

2 KKB 2

KKB 1, 2

lij 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998

KKM

L 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998

KKG

1989 1990 1991 1992 1993 1994 1995 1996 1996 1997 1998

3 KKL 2 ''

i 1 L

0 1989 1990 1991 1992 1993 1994 1995 1996 1997

108 HSK Annual report 1998 • Appendix A Figure A3a Causes for classified events in the Swiss NPPs per year 1989-1998

25 D Spontaneous failure of equipment during operation 23 • Failure or deficiency dur ng periodic test ng or maintenance work a Failure due to human factors 20 0 Other events (e.g. severe accident, fire) 20 —

17 17 12 6 15

7 13 13 7

10 10 10 — 7 5 10 8 E 5 8 6 8 5 5 — 4 3 2 4 5 II! Hi HI i i IP I •MM 1 1 1 mm I I 1 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 Year

Figure A3b

Causes of unplanned reactor scrams per year 1989-1998

D Spontaneous failure of equipment during operation • Failure or def ciency during periodic testing or maintenance work S Failure due to human factors

6 6 5 5 5 5 4 a> c 4 c 4 Q. 3 3 3 3 C 3 1 5 2 2 2 1 1 3 3 3

ill •lii!* 111 n 1 1 I I I I I 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998

Year

HSK Annual report 1998 • Appendix A 109 Figure A4 Fuel element defects (number of elements) 1988-1998

GKKB 1: slight damage8 M KKB 1: larger damageb

KKB 1 KKB 2: no damage

......

4 :-

C] only slight damagea

KKM 2 i-—

88/89 89/90 90/91 91/92 92/93 93/94 94/95 95/96 96/97 97/98

18 10

•J slight damagea 3 :-- HI larger damageb KKG

0 '- 88/89 89/90 90/91 91/92 92/93 93/94 94/95 95/96 96/97 97/98

:_j slight damage6

H larger damage6 KKL us; a e.g. hair cracks b e.g. larger damage or i m breaks in the cladding p with fuel washout 88/89 89/90 90/91 91/92 92/93 93/94 94/95 95/96 96/97 97/98

110 HSK Annual report 1998 • Appendix A Figure A5 Annual collective doses (Person-Sv/year) in the NPPs, 1980-1998

10.3 6.5

power operation n shutdown for refuelling and maintenance

KKB 1, 2

1980 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 Year

6 r : ; ~ • | ; ; !S power operation shutdown for refuelling and maintenance

KKM

1980 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 Year

§3 power operation G shutdown for refuelling and maintenance

KKG I c o en

198081 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 Year

H power operation [j shutdown for refuelling and maintenance TO A CD 4

KKL C o s. 2

198081 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 Year

HSK Annual report 1998 • Appendix A 111 - Figure A6 Annual collective doses (Person-Sv/year) in the NPPs: 1969-1998

KKB 1 + 2 -•«•: KKG KKL KKM — PSI

12 !

1969 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 89 90 91 92 93 94 95 96 97 98 Year Figure A7 Number of persons with an individual annual whole-body dose over 20 mSv in the NPPs: 1984-1998

200

KKB 1, 2

1984 85 87 88 89 90 91 92 93 94 95 97 98 Year

200 :

KKM

1984 85 86 87 89 90 91 92 93 95 96 97 98 Year

Ofif) ___„ _...

ff. iRn ', ______c O cn | 120 KKG | 80 _ E : Z 40 -—

1984 85 86 87 88 89 90 91 92 93 94 95 96 97 98 Year

200

160 o | 120 •-- KKL o

40 r

_3 . 1 J^. 0 j 0 . 0 , _0 j 0 0 0 0 '•- t 1984 85 86 87 89 90 91 92 93 94 95 96 97 98 Year

HSK Annual report 1998 • Appendix A 113 Figure A8 Average annual dose (mSv) of own and external personnel of the nuclear power plants: 1980-1998 12 M plant own personnel 10 IZ external personnel 8

KKB 1, 2 6 4 S 1 2 13 n ' ! i i\

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12 ES< plant own personnel 10 I external personnel

KKL 6

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114 HSK Annual report 1998 • Appendix A Figure A9 Number of individuals (own personnel) of the nuclear power plants who at the end of each of the years between 1980 and 1998 have accumulated integrated doses (life-dose) exceeding 200 mSv

KKB 1, 2

% L pmiU All 198081 82 83 84 85 86 87 88 89 95 96 97 98 Year

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HSK Annual report 1998 • Appendix A 115 Figure A10 Calculated dose for the most affected person1 (adult) in the vicinity of the nuclear power plants: 1978-1998

C o a. 0.01 --

> E

0.001

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Place (locality) where the MADUK probes are situatet

160 140 KKL 120 100 Legend H Minimum daily value 80 ill Maximum daily value 60 ® Years average value 40 1 20 0

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HSK Annual report 1998 • Appendix A 117 Figure A11 (cont.)

Local dose rate in 1998, as measured by the IVIADUK probes

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11! HSK Annual report 1998 • Appendix A Appendix B

Tables Table B1 List of the Swiss Guidelines (R) and Recommendations (E) presently in force ... 120 Table B2 International Nuclear Event Scale (INES) 124 Table B3 Basic characteristics of the Swiss nuclear power plants 126

Figures Figure B1 Functional diagram of a nuclear power plant with a pressurised water reactor ..127 Figure B2 Functional diagram of a nuclear power plant with a boiling water reactor 127

Publications 128

List of Abbreviations 130

HSK Jahresbericht 1998 • Anhang B 119 Table B1

List of the Swiss Guidelines (R) and Recommendations (E) presently in force Languages: All guidelines originally written in German; guidelines noted/e, /f or /r translated into and available in English, French or Russian.

Date of current Guideline Title of Guideline issue

Aufsichtsverfahren beim Bau von Kemkraftwerken; Projektierung von Bauwerken R-04/d December 1990 (Supervisory procedures governing the construction of nuclear power plants: Design of buildings)

Aufsichtsverfahren beim Bau von Kernkraftwerken: mechanische Ausrustungen R-05/d October 1990 (Supervisory procedures governing the construction of nuclear power plants: Mechanical equipment)

Sicherheitstechnische Klassierung, Klassengrenzen und Bauvorschriften fur Ausrustungen in Kernkraftwerken mit Leichtwasserreaktoren R-06/d May 1985 (Safety classification, interface between classes and construction regulations concerning equipment of light water reactor nuclear power plants)

Richtlinie fur den uberwachten Bereich der Kernanlagen und des R-07/d : Paul Scherrer Institutes June 1995 R-07/r (Guideline for radiation protection zones in nuclear installations and in the Paul Scherrer Institute)

Sicherheit der Bauwerke fur Kernanlagen, Prufverfahren des Bundes fur die Bauausfuhrung R-08/d May 1976 (Safety of buildings for nuclear installations: Federal supervisory procedures for the construction

Ziele fur den Schutz von Personen vor lonisierender Strahlung im Bereich von Kernkraftwerken R-11/d May 1980 (Objectives of the protection of persons from ionising radiation in the vicinity of nuclear power plants)

Objectifs de la protection des personnes contre les radiations R-11/f July 1978 ionisantes dans la zone d'influence des centrales nucleates

Erfassung und Meldung der Dosen des strahlenexponierten Personals der Kernanlagen und des Paul Scherrer Instituts R-12/d (Determining and Reporting the doses of occupationally radiation October 1997 exposed personnel in nuclear installations and the Paul Scherrer Institut)

R-14/d Konditionierung und Zwischenlagerung radioaktiver Abfalle December 1988 R-14/r

R-14/e Conditioning and Interim Storage of Radioactive Wastes December 1988

Berichterstattung uber den Betrieb von Kernkraftwerken R-15/d (Reporting guideline concerning the operation of nuclear power August 1996 R-15/r plants)

Seismische Anlageninstrumentierung R-16/d February 1980 (Seismic plant instrumentation)

R-17/d Organisation und Personal von Kernkraftwerken August 1986 R-17/r (Organisation and personnel of nuclear power plants)

120 HSK Jahresbencht 1998 • Anhang B Table B1 (cont.) List of the Swiss Guidelines (R) and Recommendations (E) presently in force

Date of current Guideline Title of Guideline issue

R-21/d Schutzziele fur die Endlagerung radioaktiver Abfalle i November 1993

R-21/e Protection Objectives for the Disposal of Radioactive Waste | November 1993

Objectifs de protection pour le stockage final des dechets ' November 1993 radioactifs R-21/f Revisionen, Prufungen, Ersatz, Reparaturen und Anderungen an elektrischen Ausrustungen in Kernanlagen December 1993 (Revisions, testing, replacement, repair and modification of R-23/d electrical equipment in nuclear installations)

Berichterstattung des Paul Scherrer Institutes sowie der Kernanlagen des Bundes und der Kantone R-25/d (Reporting guideline concerning the Paul Scherrer Institut and the June 1998 nuclear installations of the Federation and the cantons)

Auswahl, Ausbildung und Prufung des lizenzpflichtigen ; R-27/d : Betriebspersonals von Kernkraftwerken i May 1992 (Selection, training and examination of NPP staff requiring a licene) ;

Aufsichtsverfahren beim Bau und Betrieb von Kernanlagen R-30/d (Supervisory procedures for construction and operation of nuclear July 1992 installations)

Aufsichtsverfahren beim Bau von Kernkraftwerken, E1 klassierte elektrische Ausrustungen R-31/d January 1994 (Supervisory procedures governing the construction of nuclear power plants: 1E classified electrical equipment)

Richtlinie fur die meteorologischen Messungen an Standorten von Kernanlagen R-32/d September 1993 (Guideline for meteorological measurement on sites of nuclear installation)

Aufsichtsverfahren beim Bau und Anderungen von Kernkraftwerken, Systemtechnik R-35/d May 1996 (Supervisory procedures governing the construction of nuclear power plants: System engineering)

Anerkennung von Kursen fur Strahlenschutz-Kontrolleure und -Chefkontrolleure; Prufungsordnung R-37/d May 1990 (Recognition of courses for radiation protection controllers and chief controllers; examination regulations)

Interpretation des Begriffs «abgeleiteter Richtwert fur Oberflachenkontamination» R-38/d July 1987 (Interpretation of the term "derived guideline value for surface contamination")

Erfassung der Strahlenquellen und Werkstoffprufer im Kemanlagenareal R-39/d January 1990 (Registration of radiation sources and material testers on a nuclear installation site)

HSK Jahresbericht 1998 • Anhang B 121 Table B1 (cont.) List of the Swiss Guidelines (R) and Recommendations (E) presently in force

Date of current Guideline Title of guideline issue

Gefilterte Druckentlastung fur den Sicherheitsbehalter von Leichtwasserreaktoren, Anforderungen fur die Auslegung R-40/d March 1993 (Filtered containment venting for light water reactors: design requirement)

Berechnung der Strahlenexposition in der Umgebung aufgrund von Emissionen radioaktiver Stoffe aus Kernanlagen R-41/d July 1997 (Calculation of the radiation exposure in the vicinity of nuclear installations due to emissions of radioactive materials)

Zustandigkeiten fur die Entscheide uber besondere Massnahmen February 1993 bei einem schweren Unfall in einer Kernanlage

Responsibility for decisions to implement particular measures to I mitigate the consequences of a severe accident at a nuclear • March 1993 installation I

Planung und Durchfuhrung von Notfallubungen in den R-45/d July 1997 schweizerischen Kernkraftwerken

Planning and Execution of Emergency Exercises in Swiss Nuclear R-45/e February 1998 Power Plants

Prufungen von Strahlenmessgeraten R-47/d October 1999 (Testing of radiation measuring devices)

Anlagezustande eines Kemkraftwerks R-100/d June 1987 (Nuclear power plant conditions)

Auslegungskriterien fur Sicherheitssysteme von Kemkraftwerken R-101/d May 1987 mit Leichtwasser-Reaktoren

Design Criteria for Safety Systems of Nuclear Power Plants with R-101/e May 1987 Light Water Reactors

Auslegungskriterien fur den Schutz von sicherheitsrelevanten R-102/d Ausrustungen in Kernkraftwerken gegen die Folgen von | December 1986 Flugzeugabsturz

Design Criteria for the Protection of Safety Equipment in NPP R-102/e December 1986 against the Consequences of Airplane Crash

Anlageinteme Massnahmen gegen schwere Unfaile R-103/d November 1989 (Plant internal measures against severe accidents)

122 HSK Jahresbencht 1998 • Anhang I Table B1 (cont.) List of the Swiss Guidelines (R) and Recommendations (E) presently in force

Recom- —.^ , _ , . : Date of current . .. Tit e of Recommendation . mendation : issue

Steuerstellen und Notfallraume von KKW: Anforderungen betr. : r_.,, : Ausfuhrungen und Ausrustungen fur Accident Management : „ . 1on_ E-04/d (OJ.I .J z Mr-,o • '•• December 1989 (Control centers and emergency rooms of NPP: requirements ; I on design and equipment for accident management) j

HSK JahresbencM 1998 • AnhangB 123 Table B2

International Nuclear Event Scale (INES) The international scale used to indicate accident severity in nuclear installations (International Nu- clear Event Scale INES jointly prepared by IAEA and NEA) was tested in a pilot scheme from the beginning of 1990 and has been in definitive use since 1992. The scale differentiates between the following seven levels of events depending on their relevance to safety.

Level Descriptor Criteria Examples

M External release of a large fraction of the Chernobyl, reactor core inventory typically involving a USSR, 1986 mixture of short- and long-lived fission products (in quantities radiologically equivalent to more than tens of thousands of 7 Major accident terabecquerels of iodine-131). Remark: Possibility of acute health effects. Delayed health effects over a wide area, possibly involving more than one country. Long term environmental consequences.

M External release of fission products (in quantities radioiogicaily equivalent to the order of thousands to tens of thousands of Serious 6 terabecquerels of iodine-131}. accident Remark: Full implementation of local emergency plans probably needed to limit serious health effects.

£1 External release of fission products (in Windscale, quantities radiologically equivalent to the order UK, 1957 of hundreds to thousands of terabecquerels of iodine-131). Accident with Remark: Partial implementation of emergency 5 off-site risk plans (e.g. local sheltering and/or evacuation) required in some cases to lessen the likelihood of health effects.

M Severe damage to a large fraction of the Three Mile Island core and major plant contamination USA, 1979 M External release of radioactivity resulting in a dose to the most exposed individual off-site of the order of a few millisieverts. Remark: Need for off-site protective actions Accident without generally unlikely except possibly for local food 4 significant off-site risk control. ™ Some damage to reactor core as a result of Saint Laurent, mechanical effects and/or melting. France, 1980 I! Worker doses likely to have acute fatal consequences.

124 HSK Jahresbencht 1998 e Anhang I Table B2 (cont.) International Nuclear Event Scale (INES)

Level Descriptor Criteria \ Examples

M External release of radioactivity above authorised limits, resulting in a dose to the most exposed individual off-site of the order of tenths of a millisievert. S Exposure of personnel sufficient to cause acute health effects. Severe spread of Serious incident 3 contamination inside the plant. H Incidents in which a further failure of safety Vandellos, systems could lead to accident conditions, or a Spain, 1989 situation in which safety systems would be unable to prevent an accident if certain initiators were to occur.

S3 Incidents with major failure of safety Sosnowy Bor, provisions, but still leaving sufficient safety Russia, 1992 margins to cope with additional faults. 2 Incident M An event resulting in a dose to personnel exceeding the statutory annual dose limit, significant contamination inside the plant which was not expected by design.

H Anomalies beyond the authorised operating 1 Anomaly regime. This may be due to equipment failure, human error or procedural inadequacies.

M Events where operational limits and conditions are not exceeded and which are properly managed in accordance with adequate procedures. Examples: Single failure in a redundant 0 No safety significance system. Human error with consequences like a single failure. Failures, detected in periodic inspections or tests (no multiple failure). Automatic Reactor Scram with normal plant behaviour. Events where operational limits and conditions are respected in accordance with adequate procedures.

HSK Jahresbericht 1998 « Anhang B 125 Table B3 Basic characteristics of the Swiss nuclear power plants

KKB 1 KKB 2 KKM KKG KKL

3138 from Thermal power [MW] \ 1130 ; 1130 1097 3002 31.10.98 3327

1085 from Electrical power [MW] 380 374 372 1020 31.10.98 1135

1030 from Net electrical power [MW] ; 365 357 355 970 31.10.98 1080

Reactor type PWR PWR BWR PWR BWR

. ,. : Westing- Westing- Reacton r suppher : , . GE KWU GE ^ house : house

Turbine supplier BBC BBC BBC KWU BBC

Generator rating [MVA] \ 2-228 2-228 2-214 1140 1318

cooling cooling Cooling river water river water river water tower tower

Start of commercial operation ; 1969 1971 1972 1979 1984

126 HSK Jahresbencm 1998 • Anhang B Figure B1 Functional diagram of a nuclear power plant with a pressurised water reactor

Reheater Pressuriser

Condenser

Feedwater Low-pressure pump feedheater

Figure B2 Functional diagram of a nuclear power plant with a boiling water reactor

Water separator

High-pressure Low-pressure turbine turbine Generator Recirculating pump Reactor High-pressure feedheater

Condenser

Feedwater Low-pressure pump feedheater

HSK Jahresbericht 1998 • Anhang B 127 Publications

List of Publications in 1998

Baggenstos, M. (HSK) 1998: Gefahrdung und Verhalten derTruppe bei einem KKW-Unfall in der Schweiz; Geb AK 3 - Zurich.

Baggenstos, M. (HSK) 1998: New Emergency Planning Concept in Switzerland; NEA Expert Group on Emergency Matters - Paris.

Baggenstos, M. (HSK) 1998: Notfallschutzplanung fur die Umgebung von Kernkraftwerken; SVA- Tagung Winterthur - Winterthur.

Baggenstos, M. (HSK) 1998: Zivile A-Bedrohung durch Kernkraftwerke; Ausbildung fur Frauen Stab BR InfoZen - Spiez.

Baggenstos, M. (HSK) 1998: Konsequenzen derTransportkontaminationen fur die Schweiz; AKN Tagung in Hamburg - Hamburg.

Bieth, M.; Birac, C; Comby, R.;Maciga, G.; Neumann, W. (HSK) 1998: Final results of the PISC III round robin test on steam generator tube inspection; First International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurised Components, 20.-22.10.1998-Am- sterdam.

Bitterli, P (HSK) 1998: Vom Kohlensumpf zum Wasserschloss; Badener Neujahrsblatter 1999. - Baden.

Bucher, В.; Rybach, L; Schwarz, G. (HSK) 1998: Environmental mapping: Comparison of ground and airborne gamma spectrometry results under Alpine conditions; Proceedings of the RADMAGS- Symposium, Stirling, June 1998 - Stirling.

Bucher; В.; Schwarz, G. (HSK); Rybach, L. Barlocher, Ch. 1998: Aeroradiometrische Messungen im Rahmen der Obung ARM97; Bericht fur das Jahr 1997 zuhanden der Fachgruppe Aeroradio- metrie (FAR); Interner Bericht, Institut fur Geophysik, ETH Zurich - Zurich.

Bucher; В.; Schwarz, G. (HSK); Rybach, L. Barlocher, Ch. 1998: Aeroradiometrische Aufnahmen in der Schweiz, in: Umweltradioaktivitat und Strahlendosen in der Schweiz 1997; Bundesamt fur Gesundheit, Bern; В 3.4.1 - В 2.4.5 - Bern.

Esmaili, H.; Orandi, S.; Vijaykumar, R.; Cazzoli, E. and Khatib-Rahbar, M. (ERI); Zuchuat, 0. and Schmocker, U. (HSK) 1998: A Much Faster than RealTime Approach to Accident Diagnostics, Anal- ysis, and Management (ADAM); Proceedings of the 4th international conference on probabilistic safety assessment and management, New York, September 13-18, 1998 - New York.

Hammer, J. (HSK) 1998: Regulatory aspects of neutron radiography; Proceedings of the Third International Topical Meeting on Neutron Radiography, March 16-19, 1998 in Lucerne Nucl. Instr. and Meth. In Phys. Res. A (1999); in print - Luzem.

Jeschki, W. (HSK) 1998: ICRP-64 Schutzkonzept gegen Ereignisse und Storfallvorsorge in der schweizerischen Strahlenschutzgesetzgebung. Expertentreffen Strahlenschutz.TUV-Akademie- Aschau.

Lioubarski, A.; Kouzmina, I.; Noskov D. (SEC NRS, Russia); Rozine, V. (NPP Novovoronezh, Rus- sia); Khatib-Rahbar, M.; Kuritzky, A. (ERI, USA); and Schmocker U. (HSK) 1998: Insights from Level- 1 PSA for Novovornezh NPP (Unit 5) and PSA-Based Modifications; Proceddings of the Interna- tional Conference on Topical Issues in nuclear, radiation and radioactive waste safety; 30 August - 4 September 1998 -Vienna.

Meyer, R; Schoen, G.; Zuchuat, 0.; Brosi, S.; Sardella, R. and Schmocker, U. (HSK); Kuritzky, A.; Cazzoli, E.; Ismaili, H.; Vijaykumar, R. and Khatib-Rahbar, M. (ERI) 1998: Regulatory Evaluation of Core Damage Frequency and Severe Accident Vulnerabilities of a KWU Pressurized Water Reac-

128 HSK Annual report 1998 • Publications tor; Proceedings of the 4* international conference on probabilistic safety assessment and management, New York, September 13-18, 1998 - New York.

MCiller, M.; Rudolf von Rohr, Ph. (ETH-Z); and Schmocker, U. (HSK) 1998: Aerosol Re-entrainment from Boiling Pool During Controlled Filtered Venting After a Severe Core Melt Accident; Proceed- ings 3rd OECD-Specialist Meeting on Nuclear Aerosols in Reactor Safety; June 15-18-Cologne.

Neumann, W. (HSK) 1998: Risiko-basierte Wiederholungsprufung aus Behordensicht; SGK- Generalversammlung, 18.6.1998 - Bern.

Neumann, W. (HSK); Gribi, M.; Schwammberger, R.;Tobler, R. 1998: Experience with a qualification project for dissimilar metal welds; First International Conference on NDE in Relation to Struc- tural Integrity for Nuclear and Pressurised Components, 20.-22.10.1998-Amsterdam.

Noggerath, J.; Wand, H. (HSK) 1998: Stellungnahme der HSK zur erhohten lokalen Korrosion an SVEA-96-Brennelementen im Kernkraftwerk Leibstadt; 3. Symposium zuratomrechtlichen Praxis in Bayern, Miinchen, 5./6.10.1998 - Munchen.

Noggerath, J.; Wand, H. (HSK) 1998: Risse im Kemmantel des Kemkraftwerks Muhleberg - bisherige Aktivitaten, sicherheitstechnische Bedeutung und aktueller Stand nach dem Revisions- stillstand 1998; 3. Symposium zur atomrechtlichen Praxis in Bayern, Munchen, 5./6.10.1998 - Munchen.

Ochs, M.; Boonekamp, M.; Wanner, H. (HSK); Sato, H.;Yui, M. 1998: quantitative model for ion diffusion in compact bentonite; Radiochem. Acta, 82 (1998), 437-443.

Pretre, S. (HSK) 1998: Decision-making in abnormal radiological situations;The Societal Aspects of Decision Making in Complex Radiological Situations; Workshop of OECD / NEA; 13-15 Janu- ary 1998 -Villigen.

Pretre, S. (HSK) 1998: Die Sicherheit der Kernenergie wird uns etwas kosten, Marktoffnung hin oder her; Interview in der Aargauer Zeitung; 1.9.1998 - Aargau.

Pretre, S. (HSK) 1998: Eviter le syndrome "Titanic"; Interview du journal Le Matin; 4 octobre 1998 - Ouest-Suisse.

Pretre, S.; Jeschki, W.; Noggerath, J.; Schmocker, U. (HSK) 1998: Kosten und Sicherheit; SVA- Vertiefungskurs zur Kostenoptimierung in Kernkraftwerken; 22.-24.4.98; Schweizerische Vereinigung fur Atomenergie (SVA) - Brugg / Windisch.

Rybach, L; Bucher, B.; Schwarz, G. (HSK) 1998: Airborne surveys of Swiss nuclear facility sites; Proceedings of the RADMAGS-Symposium, Stirling, June 1998 - Stirling. Rybach, L; Bucher, B.; Schwarz, G. (HSK) 1998: Airborne gamma ray spectrometry for nuclear safety and environmental applications: State of the art examples from Switzerland; Workshop on GIS, Airborne remote sensing and geospatial clearinghouse in Hungary, Budapest, February 19/ 20 1998- Budapest.

Schoen, G. (HSK) 1998: A Databank for PSA Data; International Workshop on Reliability Data Collection for Living PSA- Budapest.

Tipping, Ph.; Chakraborty, S. (HSK) 1998:Technical Note: Management of Resources and Collabo- ration in Nuclear Safety Research; Nuclear Safety, Vol. 38-No. 1, January-March 1997 (erschienen 1998); Technical Progress Journal prepared for the U.S. Nuclear Regulatory Commission.

Tipping, Ph.; Noggerath, J. (HSK) 1998: Materials ageing in nuclear power plants: Surveillance programmes and some mitigation stragies to enhance operational reliability and safety; Risk, Economy and Safety, Failure Minimisation and Analysis, Failures'98; R.K. Penny, Engineering Formation cc, Fish Hoek- Rotterdam, South Africa.

Van Doesburg, W.; Maeder, C; Wand, H. (HSK) 1998: Licensing of MOXfuel in Switzerland; Pro- ceedings of the International Topical Meeting on the Safety of Operating Reactors, October 11- 14, 1998-San Francisco; (ISBN 0-89448-630-6).

HSK Annual report 1998 • Publications 129 List of Abbreviations

AC Atomic and Chemical ADAM Accident Diagnostics, Analysis and Management ADPIC Atmospheric Diffusion Particle-ln-Cell model AM Accident Management ANPA System for automatic transmission of plant parameters from the NPPs to the HSK

ASE Department for Radiation Protection and Disposal ASME American Society of Mechanical Engineers ASP Ageing Surveillance Programme ATEL Aare-Tessin Electricity Co. Ltd. ATWS Anticipated Transient Without Scram AWARE Alarm system

B BAG Swiss Federal Office of Public Health BBT (OPET) Swiss Federal Office for Professional Education and Technology BFE Swiss Federal Office of Energy BIOMOVS Biospheric Model Validation Study BKW BKWFMB Energy AG BNFL British Nuclear Fuels Ltd. Bq Becquerel = radioactivity (1 Bq = 2.7-1CT11 Ci) BWR (SWR) Boiling Water Reactor BZL Swiss Federal Interim Storage Facility BZS Swiss Federal Office for civil defence

c CFS French-Swiss Commission on the Safety of Nuclear Installations CNS Convention on Nuclear Safety Co-60 Cobalt 60 (isotope) COGEMA Compagnie Generale des Matieres Nucleates, La Hague COM PRO Computerised Emergency Procedures CSNI Committee for the Safety of Nuclear Installations CVRS Cement Volume Reduction and Solidification

DEZA (SDC) Swiss Agency for Development and Co-operation DSIN French Nuclear Safety Authority DSK German-Swiss Nuclear Safety Commission

EAWAG Swiss Federal Bureau for Water Supply, Waste Water Purification and Water EKS Federal Commission for Radiation Protection EPFL Swiss Federal Institute of Technology, Lausanne EU European Union

France

GB Great Britain GE General Electric Company GFS Reactor Simulator School (Essen, Germany) GNW Co-operative for Nuclear Disposal Wellenberg GWh Gigawatthours = 109Watthours

130 HSK Annual report 1998 • List of Abbreviations List of Abbreviations (cont.)

HAA High-level waste HRA Human Reliability Analysis HSK Swiss Federal Nuclear Safety Inspectorate HTL HigherTechnical School HTR High Temperature Reactor

IAEA International Atomic Energy Agency INES International Nuclear Event Scale IRA Institut de Radiophysique Appliquee, Lausanne IRRT International Regulatory Review Team

K KKB Nuclear Power Plant Beznau KKG Nuclear Power Plant Gosgen KKL Nuclear Power Plant Leibstadt KKM Nuclear Power Plant Muhleberg KNE Commission for Nuclear Waste Disposal KOMAC Federal Committee for Radiological and Chemical Protection Kr Krypton KSA Swiss Federal Nuclear Safety Commission KUeR Swiss Federal Commission for Radioactivity Surveillance

LP&S Low Power and Shutdown LWR Light Water Reactor

M MAA Medium-level active waste MADUK Monitoring network for the automatic dose rate measurement in the NPPs' vicinity Man-Sv collective radiation dose (1 man-Sv = 100 man-rem) MBT Department of Mechanical and Civil Engineering MGy Mega-Gray = 106 Gray (1 Gray = 100 rad) MIR Medical, Industrial and Research (Waste) MMI Man-machine interaction MOX Mixed oxide (uranium-plutonium) jiSv Micro-Sievert = 10^ Sievert mSv Milli-Sievert = 10~3 Sievert MW Megawatt = 106Watt (power unit) MW3 Megawatt electrical power MWth Megawatt thermal power

N NADAM Network for automatic dose alarm and monitoring NAGRA National Co-operative for the Storage of Radioactive Waste NANO Emergency standby system and improved power supply at KKB NASA National Safety Agency NAZ National emergency operation center Nb-93 Niobium (isotope) NEA Nuclear Energy Agency NERS Network of Regulators of Countries with Small Nuclear Programmes Ni-63 Nickel (isotope) NOK Nordostschweizerische Kraftwerke AG NPP(KKW) Nuclear Power Plant NRC Nuclear Regulatory Commission (USA)

HSK Annual report 1998 • List of Abbreviations 131 List of Abbreviations (cont.)

OECD Organisation of Economic Co-operation and Development OSART Operational Safety Review Team (IAEA)

p PSA Probabilistic Safety Analysis PSE(PSU) Periodic safety examination PSI Paul Scherrer Institute, Wurenlingen and Villigen (East and West) PTS Pressurised Thermal Shock PWR (DWR) Pressurised Water Reactor

Q QA (QS) Quality assurance

R REFUNA Regional heat supply system of the lower Aare valley RMCS Reactor Manual Control System RPIS Rod Position Information System RPV Reactor Pressure Vessel

SAA Low-level wastes SAMG Severe Accident Management Guidance SKI Swedish Nuclear Safety Authority SMA Low- and Medium-level Active Wastes Sr-90 Strontium (isotope) SRM Source Range Monitor STA Shift Technical Advisor StSG Radiation protection law StSV Radiation protection Ordinance STUK Radiation and Nuclear Safety Authority of Finland SUeR Section for radiation monitoring, Freiburg SUSAN Special independent system for decay heat removal (KKM) Sv Sievert = equivalent dose unit (1Sv = 100 rem) SVP Flow distribution plate (steam generator) SVTI Swiss Association forTechnical Inspections

TBq Terabequerel (1TBq = 1012 Bq) THORP Thermal Oxide Reprocessing Plant TLD Thermal-Luminescent Dosemeter TS Storage Cask Type TUV German Technical Control Association

u USA United States of America US-NRC American Nuclear Regulatory Commission UVEK (DETEC) Department of Environment, Transport, Energy and Communication

VAKL Experimental nuclear power plant, Lucens VEOR Regulation on Emergency Organisation for the Case of Increased Radioactivity VSE Union of Swiss Electricity Producers

W WENRA Western European Nuclear Regulators' Association WINDBANK Wind Data Bank

132 HSK Annual report 1998 jst of Abbreviations List of Abbreviations (cont.)

x Xe Xenon

ZWIBEZ Interim Radwaste Storage Facility, KKB ZWILAG Interim Storage Facility, Wurenlingen ZZL Central Interim Storage Facility, Wurenlingen

HSK Annual report 1998 • List of Abbreviations 133 HSK, Wurenlingen (Switzerland) Postal address: HSK, CH-5232 Villigen-HSK Telephone: ++41 (0)56 310 38 11 Telefax: ++41 (0)56 310 39 95 and ++41 (0)56 310 39 07 Internet: www.hsk.psi.ch