Annual Report 1996 Concerning the Nuclear Safety and Radiological Protection in the Swiss Nuclear Installations

CH9800006

Annual report 1996 concerning the nuclear safety and radiological protection in the swiss nuclear installations

Hauptabteilung fur die Sicherheit der Kernanlagen Division principale de la Securite des Installations Nucieaires Divisione principale della Sicurezza degli Impianti Nucleari Swiss Federal Nuclear Safety Inspectorate -11

29- 08 Annual report 1996 concerning the nuclear safety and radiological protection in the swiss nuclear installations

May 1997 HSK-AN-3134 KSA-AN-1940

Cover picture The illustrated map showing ambient dose rates was cre- For design reasons, no key to the map is given on the ated from a combination of the existing radiometric data cover. It can be found with the illustration on page 86. (aerial gamma spectrometry, in situ gamma spectrometry, Ambient dose rate values vary in the range 50 to 450 laboratory measurements on rock and soil samples, and nSv/h, with a peak between 70 nSv/h and 110 nSv/h. The ambient dose rate measurements). A description of the highest values are found in the Alps, because both the methods used to create the map can be found in "L natural radioactivity of the alpine rock and the irradiation Rybach, G. Schwarz: Ground gamma radiation maps: due to cosmic rays are high. processing airborne, laboratory and in situ spectrometry The white points mane the locations of the Swiss nuclear data, First Break, Vol. 13, March 95". installations.

HSK Annual report 1996 Contents

Preface 5

HSK Terms off reference 7

Organization 8

1. Beznau Nuclear Power Plant 11 1.1 Operational data and results 11 1.2 Plant safety 11 1.3 Radiation protection 14 1.4 Personnel and organisation 15 1.5 Emergency preparedness 15 1.6 Radioactive wastes 15 1.7 Compliance with licensing conditions for KKB Unit II 16 1.8 Overall judgement by HSK 17 2. Muhleberg Nuclear Power Plant 21 2.1 Operational data and results 21 2.2 Plant safety 21 2.3 Radiation protection 23 2.4 Personnel and organisation 24 2.5 Emergency preparedness 24 2.6 Radioactive wastes 25 2.7 Fulfilment of licensing conditions 25 2.8 Overall judgement by the HSK 25

3. Gosgen Nuclear Power Plant 29 3.1 Operational data and results 29 3.2 Plant safety 29 3.3 Radiation protection 31 3.4 Personnel and organisation 32 3.5 Emergency preparedness 32 3.6 Radioactive wastes 32 3.7 Overall judgement by the HSK 33

4. Leibstadt Nuclear Power Plant 37 4.1 Operational data and results 37 4.2 Plant safety 37 4.3 Radiation protection 39 4.4 Personnel and organisation 40 4.5 Emergency preparedness 40 4.6 Radioactive wastes 41 4.7 HSK safety evaluation report on the power increase 41 4.8 Overall judgement by the HSK 41

5. Central Interim Storage, Wurenlingen 45 5.1 Review and assessment 45 5.2 Licence and licensing conditions 45 5.3 Supervision of construction 45 5.4 Waste from reprocessing 45

HSK Annual report 1996 6. Paul Scherrer Institute (PSI) 49 6.1 ThePSI in Villigen and Wurenlingen 49 6.2. Research reactors 49 6.3 Accelerator, proton beam channels and experimental areas 50 6.4 Hot Laboratory 50 6.5 Treatment of radioactive wastes 51 6.6 Storage of radioactive wastes 52 6.7 Particular events 52 6.8 Additional themes 53 6.9 Overall judgement by the HSK 53

7. Other Nuclear Installations 55 7.1 Ecole Polytechnique Federale de Lausanne (EPFL) 55 7.2 University of Basle 55 7.3 Experimental reactor at Lucens (VAKL) 55

8. Disposal of Radioactive Wastes 59 8.1 Wellenberg repository 59 8.2 Disposal of high-level wastes: preparatory measures 59

9. Transport of Radioactive Materials 61 9.1 Approvals according to transport legislation 61 9.2 Authorisations according to radiation protection legislation 61 9.3 Audits and inspections 61 9.4 Training and information 61

10. Emergency Preparedness 65 10.1 HSK emergency organisation 65 10.2 Training activities in the area of emergency protection 65 10.3 WINDBANK, ADPIC 65 10.4 MADUK.ANPA 66

11. Selected Aspects of Nuclear Safety and Radiation Protection 69 11.1 Guidelines 69 11.2 Instructive events in foreign nuclear installations 69 11.3 Ageing surveillance 70 11.4 Periodic safety review 71 11.5 Probabilistic safety analysis 72 11.6 Human factor and safety culture 73 11.7 Evaluation of events in nuclear installations 73

12. Research, Training and International Co-operation 77 12.1 Safety research 77 12.2 PSI Schools 81 12.3 Nuclear Safety Convention of the IAEA 82 12.4 Co-operation with other countries 82

Appendix A 87 Appendix B 115 List of Abbreviations 123 Pictures 126

HSK Annual report 1996 Preface

The Swiss nuclear installations are subject to central interim storage (ZZL) and took up the official surveillance by the Swiss Federal surveillance of the construction work. Nuclear Safety Inspectorate (HSK) in all mat- ters regarding nuclear safety and radiation pro- On 12 September 1996, Switzerland ratified tection. This surveillance involves supervision, the "International Convention on Nuclear inspections and various calculations and inves- Safety". This agreement came into force for tigations, which together allow an independent Switzerland on 11 December 1996. Those evaluation to be made of their safety. All the signatories to this convention which implement work of evaluation performed by the HSK in nuclear energy programs undertake to make 1996 provides a comprehensive picture of the nuclear safety a high priority. Switzerland state of Swiss nuclear installations with regard already meets most of the conditions of the to their nuclear safety and radiation protection. agreement. However, an improvement which Other scientific activities are undertaken by the should be reached concerns the independence HSK in preparation for later evaluations. of the nuclear safety authority-that is, the HSK -from bodies which represent the use and pro- The year 1996 was marked by the following duction of nuclear energy. First steps are being highlights: taken as part of the governmental reforms to give the HSK a status which ensures greater March autonomy and a more credible independence. The HSK completed its assessment of the application by the Leibstadt Nuclear Power Plant The decision taken in 1995 to reorganize the for an increase in power. This comprehensive HSK, was implemented in 1996. In the area of report can be accessed on the Internet. information it should be noted that, since April 1996, many HSK documents can be accessed April on the Internet at http://www.hsk.psi.ch. This marked the tenth anniversary of the Chernobyl catastrophe.This gave reason to In summary, it can be stated that 1996 has been draw a balance on the consequences and the a very dynamic year for the HSK. lessons learned.

May The HSK completed an assesment on the application for a final repository for low and medium level wastes in Wellenberg.

September On the basis of the Federal Council authorisation, dated 21 August 1996 and issued to the "Zwischenlager Wurenlingen AG (ZWILAG)", the HSK gave the first execution permit for the Dr. Serge Pretre, Director of the HSK

!®ff 11LA&K

HSK Annual report 1996 HSK Terms of reference

Mission Conduct and style

We supervise and judge the Swiss nuclear in- In our contacts with the operators of nuclear stallations with regard to nuclear safety and installations and their agents we are vigilant, radiation protection, right through from the plan- critical and consistent. Our conduct is noted ning stage, to construction, to operation, to for being open and factual. decommissioning and dismantling. We control compliance with legal binding regulations and with the conditions laid down by the licensing Relationship to science and authority. Furthermore, we consider the experience and the latest, worldwide state of science technology and technology. We know, and promote, the international state of science and technology in all areas of nuclear safety and of radiation protection, and we make Objective use of this in the performance of our tasks. At no time should any Swiss nuclear installation pose a threat to people or to the environ- Relationship to politics and ment through the emission of ionising radiation. A nuclear installation may operate only economics when this objective is fulfilled, as far as is In the performance of our tasks, we are inde- humanly possible. pendent of political or economic interests. Our decisions serve to protect the public, the personnel of nuclear installations, and the envi- Means and authority ronment.

We have available the necessary financial means and human resources to perform our Relationship to the public mission and we have the authority and the means to enforce our requirements. We pay careful attention to public needs for rapid, correct and understandable information. Organization

In order to perform our tasks, we are divided into areas related to various scientific and technical disciplines. Interdisciplinary internal communication is of the greatest importance. As part of a nationwide emergency organization, we stand ready to mobilize for action within a short time, around the clock.

HSK Annual report 1996 00 Swiss Federal Nuclear Safety Inspectorate (HSK) Organisation Director: S. Pr§tre, Dr. Section Staff Deputy: W. Jeschki April 1997 Head: G. Schwarz, Dr. U. Sch mocker, Dr. Dir. secretary: A.R. Schneider Administration: Head: A. Kramer Computing: Head: P. Schmid Information & Library: Head: A. Treier Safety Research Swiss Federal Nuclear and International Safety Commission: Scientific Advisor Programmes (SFI) Secretariat (KSA) R. Gilli Head: S. Chakraborty 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 PSI 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 ofNPP 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 G. Prantl, Dr. W. van Doesburg, U. Schmocker, Dr. A. Frischknecht.Dr. M. Baggenstos F. Cartier, Dr. M. Furrer, Dr. A. Zurkinden, Dr. Dr. Kontaminationskontrolle neuer Brenneiemente nach deren Aniieferung Controle de contamination d'assemblages combustibles neufs apres leur livraison Contamination check of fresh fuel bundles upon delivery 1. Beznau Nuclear Power Plant

1.1 Operational data and there was one unplanned power reduction, caused by a fault in the 220 kV grid. results During the year under review, Unit II had two The Beznau Nuclear Power Plant (KKB), be- unplanned reactor scrams during full power and longing to Nordostschweizerische Kraftwerke one during partial power. Four planned power (NOK) consists of two virtually identical dual- reductions occurred during power operation to loop pressurised water reactor units (KKB I and repair leaks in the areas of the pre-heater and KKB II), each with a net electrical output of of a turbine control unit, and to locate a fault in 350 MW, which went into operation in 1969 and the area of the generator. One unplanned power 1971 respectively. During recent years the out- reduction was, as in Unit I, caused by the fault put of both units has been improved following in the 220 kV grid. back-fitting work, making it necessary to rede- fine the power rating. With the thermal reactor power output remaining the same, the follow- 1.2 Plant safety ing net electrical outputs are now being achieved: Unit I 365 MW and Unit II 357 MW. 1.2.1 Particular events From 1 October 1996, these newly defined The following notifiable events were reported output figures serve as the basis for all energy by the operator according to Guideline R-15. statistics, and especially for establishing the load factor. In Unit I there were the following four events: Additional data are summarised in Tables A1 - Two events which both led to a reactor and B3 of the Appendix; Figure B1 shows the scram, one during a test at 100%, one at functional diagram of a pressurised water re- 90% power, were caused by faults in the area actor plant. of the reactor trip breaker3. In both cases, Units KKB I and KKB II performed with a load insufficient locking of the release mechanism factor1 of 88.9% and 89.4% respectively and of the low voltage coil was discovered to be availability factors2 of 88.2% and 90.1% respec- the cause. To remedy this, in future, special tively. The proportion of unproductive time is inspections will be made of the locking due, primarily, to the planned outage for refuel- mechanism during revision work on the re- ling and maintenance. actor trip breakers. The refuelling and maintenance outage - A fault in the area of temperature control of lasted 43 days for Unit I and 36 days for Unit II. the cooling water of a diesel powered emer- The thermal energy fed into the district heat- gency electricity generator resulted in the die- ing supply system (REFUNA) amounted to a sel motor being switched off during a monthly total of 141.1 GWh in 1996 for both units. functionality test. This was caused by the late During the year under review, Unit I had one opening of the inlet valve of the supplemen- unplanned reactor scram under full power, one tary cooling water system which supports during low power and one during start-up after diesel engine cooling when outside tempera- the revision outage. The latter occurred during tures are high. The valve opening point was a test at low power. Scrams of this kind have then set lower so that additional cooling of little impact on the primary cycle structures and the diesel motor is triggered sooner. core installations. During power operation two - The fourth event occurred when, after the planned power reductions occurred, one was revision outage, at 1 to 2% of reactor power, to remedy a fault in the turbine area and the the new protection system for both the Unit I other to repair a leak in the pre-heater area; and its internal power supply was to be started up with a test programme. During 1 Load factor (in %): Energy actually produced as a per- synchronisation with the new protection centage of rated power at 100% availability. equipment, one of the two turbo groups in- advertently increased the load, and this 2 Availability (in %): Time that the plant is operating or is caused a rise in reactor power to 12.6%. available for power generation. Since only the auxiliary feedwater pumps are 3 Reactor trip breaker: Breaker causing reactor scram in operation during low power, the amount

HSK Annual report 1996 • Beznau Nuclear Power Plant 11 of water supplied was insufficient to feed the teria "low water level in steam generator" and steam generator, with the result that "low "feedwater-steam flow mismatch", causing water level in steam generator" caused an the reactor scram. automatic reactor scram. The inadvertent de- - During the monthly functionality test of the mand on the turbo group was caused by an channels of the reactor protection system, a unforeseen reaction of the automatic turbine reactor scram occurred. For the test, the one controller. Besides, the reactor already went channel to be tested has to be brought into critical at 251 °C instead of at the prescribed the trip position. At the same time, a spuri- minimum temperature of 276°C. Although ous signal occurred in another channel. this caused no danger - no safety criteria Thus, for a short time, two channels were were infringed - this occurrence is classi- activated, starting the reactor scram. The fied as level 1 on the international INES cause of the spurious signal could not be scale, because an operational limit was not found. A permanent recorder was installed adhered to and a regulation was not obeyed. to log the event should it recur and provide more detailed information. In Unit II there were five events, as follows: - A reactor scram was caused at 35% power Two events, which did not lead to a reactor by "high water level in steam generator" while shutdown, were caused by faults during the shutting down the plant for refuelling. The monthly functionality tests. cause was in a feedwater control valve which - During verification for the availability of the did not throttle the feedwater supply to a gen- safety injection system, the 6 kV breaker of erator when discharging the turbo groups. the emergency recirculation pump could not This caused an overfeed to steam genera- be operated in the test. The cause was found tor A, consequently leading to the reactor to be a fault in the solenoid of the in-coil of scram. The malfunctioning of the control the breaker. To remedy this, a backfitting pro- valve was caused by thick deposits of mag- gramme was introduced for breakers of this netite in the valve seating which prevented type and was completed by the end of 1996. the full closure of the valve. The valve was The availability of the emergency re- overhauled during the refuelling outage. circulation system was only slightly impaired It can be seen from the nine events reported by this incident, since the pump can be that six events arose in connection with inspec- started from the on-site switchgear. tions, of which three events were caused by - The second event concerned the failure of faulty components, one by setting the nominal the emergency well-water pump during value of a control armature too low, one by preparations for the functionality test of the human error, and one event where the cause ultimate emergency cooling system. After an of the fault could not be identified. The three operating time of about 6 seconds with nor- remaining events were reactor scrams caused mal operating values, the pump was by the failure of technical components. switched off by the protection signal "over- The above notifiable events in both units load". A renewed attempt to start the pump were all categorised as Class B according to produced the same signal, and the pump HSK criteria. One was placed at level 1 of the could not be started. While the fault was international INES scale (see section 11.7 and being located, the supply of well-water was Table B2 in Appendix B). kept on standby by connecting up to the well supply of Unit I. The investigation revealed 1.2.2 Work during the refuelling a faulty contact in the plug connection in the outages control circuit of the 0.4 kV switch on the In both units the tasks, such as refuelling, elec- emergency well-water pump. The fault was trical and mechanical inspections of compo- rectified by appropriate corrective measures. nents and systems, periodic examinations and Three events each led to a reactor scram. functionality tests of components and systems, - A short circuit in the induction coil of the bo- and maintenance work, were carried out as ric acid flow meter to the boric acid mixer planned. caused a drop in voltage in the correspond- Since cracks had been found in austenitic ing instrumentation train. In accordance with steel pipe weld seams in German nuclear procedures, the control equipment supplied power plants, the HSK required random check by this train was switched to manual and the programmes to be carried out in the Swiss reserve supply to the affected train put into plants. During the outages of KKBI and II, X-ray operation. However, after a short time, an examinations were performed on welds of the overload shut off this secondary supply. This pressurizer spray pipe and on welds of the caused a loss of voltage to the steam gen- safety injection pipe. The areas having indica- erator level control, finally leading to the cri- tions were subjected to detailed examination,

12 HSK Annual report 1996 • Beznau Nuclear Power Plant including some destructive testing. The evalu- riod of this report, KKB applied for the ap- ation showed that the indications were not proval of a concept for a further software im- cracks but gaps of less than 0.5 mm depth, provement phase, within the ANIS system. caused during assembly. These do not jeop- This would involve the installation of the com- ardise the safety of operation. The sections re- puter supported AWARE alarm system and moved for destructive testing were replaced. of the computerised emergency procedures In Unit I, major tasks were the work in con- COMPRO. Both projects are safety related nection with the problem area of "Protection of as defined in the HSK Guideline R-35. The the containment from failure resulting from ex- two computer programs prepare and present cess pressure in the annulus", the ultrasonic process data to assist staff in the control tests for cracks below the seams of all fillet room, without intervening in the process it- welds of the main steam and feedwater piping self. The particular significance of this is that ducts. No evidence was found of the presence it would provide operators with greater sup- of any cracks below the seams. port in the recognition and control of incidents Since the original steam generators are still than presently with ANIS, due to the im- in operation in Unit II, two further tests were proved presentation of data. carried out in addition to the previous tests. Spe- In Unit I, the ESTER project (Replacement of cial revolving probes were used to detect cracks protection, transformer and exciter systems) in the 5000 steam generator tubes. The result- deserves special mention. During the outage, ing data showed that 81 tubes had to be re- as part of this project, the protection system paired with sleeves and 69 closed with sleeves for the unit and internal electrical supply as well and expansive plugs. The amount of tubing as the synchroniser and high-speed switch-over damage was about the same as in the previ- installations were replaced. The completion of ous year. The newly discovered damage rep- this stage of the project improved both the resents an operational rather than a safety emergency electricity supply and the supply to problem, and supports the operator's decision the bus bars of the unit. to replace the original steam generators with new ones in 1999. During the 1996 outage, 1.2.4 Fuel and control rods work was carried out in preparation for this re- The low concentrations of activity in the reactor placement. water and exhaust gases for KKB Unit II through- In the case of the electrical installations, par- out the year lead to the conclusion that no fuel ticular attention was paid to the revision of the rod defects had occurred in KKB Unit II. reactor trip breakers, since faulty operation of Since the start of the new cycle in KKB Unit I, this kind of breaker had resulted in two reactor the activity values of inert gases and iodine iso- scrams. topes have increased compared with the previous cycle. The values in December indicated 1.2.3 Plant modifications the presence of a single fuel rod defect. The modifications made this year were mainly For the 12-month cycle of operation in based on the findings of the latest studies and KKB Unit I, 36 fuel assemblies were replaced on the requirements of the HSK safety evalua- by new ones, for the 18-month cycle of operation report on the application for an unlimited tion in KKB Unit II, it was 48. In the course of operating license for Unit II. The most signifi- refuelling the number of uranium/plutonium cant modifications and backfittings carried out mixed oxide fuel assemblies (MOX) in KKB Unit on the two units are listed below: I was reduced from 37 to 32; as before, the - Specific improvements were made to reduce KKB Unit II reactor core contains no MOX. Of pressure drops in the primary auxiliary cool- the current 121 fuel assemblies in each Unit, ant water system. The charging pumps thus 104 and 116 respectively, are fitted with a filter became unnecessary and were dismantled. for foreign objects. - Latest findings show that cooling and heat- The behaviour of the control rods gave no ing of the annulus are unnecessary, so that indication of any damage. No obstructions to here too, the system components could be movement of the control rods, as was observed removed. in 1996 in some foreign pressurised water re- - Some years ago the ANIS plant information actors, were found in either of the two units. system was installed to replace the original This was verified by means of additional meas- process computer. Process parameters are urements of the control rod fall times. currently displayed in various forms with a During the year under review, three trans- high degree of visualisation. The addition of ports, each of 12 depleted fuel assemblies, various surveillance and monitoring pro- were sent for reprocessing grammes to ANIS has made further improvements over the old system. During the pe-

HSK Annual report 1996 • Beznau Nuclear Power Plant 13 1.2.5 Ageing surveillance programme - Completion of the cable route work As required in condition 3.8 of the operating - Grinding down the weld seams of the authorisation for KKBII, KKB has examined the pressurizer spray line in preparation for their main components as required by HSK, as part periodic examination of its ageing surveillance programme and submitted the relevant document to HSK for as- Unit II sessment (cf. section 1.7 and, section 11.3). - Grinding down the weld seams of the pressurizer spray line in preparation for their 1.3 Radiation protection periodic examination, as for Unit I - Repair work on the steam generators 1.3.1 Protection of personnel - Preparatory work for the replacement of the For the calendar year 1996 (1995 figures in steam generators brackets) the following collective doses were determined for KKB: The highest individual dose from external radiation in 1996 was 13.6 mSv (1995:14.7 mSv). KKB I Details can be seen in Tables A5 to A10 and Plant status man-Sv Figures A5 to A10. There was no spread of contamination or contamination of persons Planned outage 0.40 (0.37) which could not be removed immediately us- Power operation 0.11 (0.14) ing normal methods, e.g. showering. Using the Annual collective dose 0.51 (0.51) newly acquired "quick counter" both internal and external staff were checked for incorporation KKBI related to the tasks they had performed. There were no findings necessitating a further incor- Plant status man-Sv poration analysis. Planned outage 0.58 (0.72) With regard to the mode of operation used Power operation i 0.11 (0.14) in KKB II with the lengthened fuel cycle (18 Annual collective dose 0.69 (0.86) months instead of 12 months), the operator investigated whether any detrimental effects of long fuel cycles on radiation protection (higher KKBI + II dose rate on components, increased radioac- Plant status Total man-Sv tive release into the environment) are known Planned outages 0.96 (1.09) internationally. No negative effects were re- Power operation 0.22 (0.28) vealed by this survey or by findings at the plant. There were no radiological incidents classi- Annual collective doses 1.20 (1.37) fiable under Guideline R-15 during 1996 in In Unit I the radiological conditions during either of the units. the outage remained about the same as in the previous year and in Unit II the downward trend 1.3.2 Releases to the environment for the primary component dose rate contin- and direct radiation ues. The second 18-month cycle in Unit II again Quarterly monitoring by the HSK, and partly had no influence on the radiological conditions also by SUeR, of aerosol and iodine filters and in the plant. of waste water samples were continued during During outage work in both units, about 70 this year. The results from all the laboratories tonnes of temporary lead shielding was again concerned showed good agreement. set up. This allowed savings of about The annual releases of radioactive materi- 0.5 man-Sv in each plant. Moreover, the work als into the environment are listed in Table A4. was planned in detail, with dose optimization, They were below the limits set. In the case of training on mock-up for steam generator work the waste water, a comparison of the last five in Unit II, and modern radiation protection with years shows a significant reduction in radioac- a comparison made every day between tive releases, with the exception of tritium. The planned and actual doses for each specific task. releases were lower primarily because outage This resulted in the values shown in the table, work was less extensive. As in previous years, a record low for a year with one revision per the tritium release, typical of water-pressure each unit, even though some of the tasks were reactors, was slightly below 20% of the limit. significant with regard to dose rate, such as: Table A4 shows the calculated worst case dose for individual members of the population. Unit I For the whole of the year under review this is - Replacement of electrical cables of the approximately 0.001 mSv for adults and pressurizer heater 0.002 mSv for infants. This corresponds to

14 HSK Annual report 1996 • Beznau Nuclear Power Plant about 1% of the guideline dose of 0.2 mSv per The OSART inspection of KKB in 1995 re- year for KKB according to HSK Guideline R-11. vealed positive features in the KKB organisa- Articles 5 and 6 of the Radiation Protection tion and also offered some suggestions and Ordinance state that activities which result in recommendations. KKB formed an internal an effective dose of less than 0.01 mSv per study group to evaluate these suggestions and year for the persons concerned are deemed recommendations and, where practical, to im- justified and optimised. This means that no fur- plement them. For 1998 KKB has planned a ther efforts to reduce radioactive release or the follow-up inspection by OSART to check and resultant dose for the population are necessary. evaluate the measures implemented. The dose rate monitoring network (MADUK) in the vicinity of KKB and the quarterly measurements at the perimeter detected no signifi- 1.5 Emergency preparedness cant increase in the ambient dose rate above the background radiation. During the year under review a staff emergency exercise in the field of security (physical pro- 1.3.3 Radiation protection tection) was carried out at KKB under the name instrumentation "JANUS". This was designed mainly to check As part of the maintenance programme, the how well the picket engineers had been trained ongoing improvement of fixed radiation meas- to take the lead in an emergency, and to drill all uring devices continued with updating of moni- the emergency staff at KKB in co-operating with tor software and enhancement of protection the police. The objectives of the exercise were against electromagnetic interference. In par- achieved. ticular, the tasks which can be executed only during the outage have been completed. All personal monitors and other radiation protection measuring equipment performed properly. KKB 1.6 Radioactive wastes successfully participated in the annual com- During the year under review the quantity of parative measurements of personal dosimetry raw radioactive wastes was as expected, judg- services organised by the EKS, and provided ing from the experience of previous years (see evidence of the required degree of accuracy of Table A11). Sludge from the waste water treat- measurements. ment plant and filter cartridges were routinely cemented. In preparation for the planned 1997 campaign for solidification in polystyrol, the 1.4 Personnel and organisation designated 100-litre containers were filled with exhausted resins and stored in a suitable area. 1.4.1 Personnel and training Mixed wastes were removed to the PSI for During the year under review two reactor processing. At PSI, combustible wastes are operators, a shift chief and a picket engineer incinerated and the incineration residue were licensed. The total number of licensed cemented. Small amounts of non combustible personnel is given in Table A2. The total work and non-compressible wastes, e.g. concrete force at the plant was 460 at the end of the fragments, were cemented at PSI. The resulting year (1995: 453). packages of conditioned wastes were returned For the purpose of further training of shift to KKB. staff, several courses were held on the com- The final specification for the waste pack- pact simulator in Beznau and on the full-scope age of the type "cemented incineration residue" simulator at Westinghouse's plant in Pittsburgh, planned for 1996 was postponed until 1997. USA. Various internal and external courses Pending processing at a later date, various were held to give shift staff extra theoretical raw wastes were stored, untreated, in areas in training. the controlled zone. This includes particularly Again, during the year under review, many compressible wastes being collected for the employees in specialist departments attended next campaign, as well as aluminium, corun- various training courses in order to keep their dum and glass bead wastes, which will be specialised knowledge up to date with the lat- treated later in the plasma furnace at ZWILAG. est technical advances. Conditioned waste packages were routinely brought and held in the temporary storage build- 1.4.2 Organisation and operational ing and the low-level waste storage hall (SAA management hall)oftheZWIBEZ. There were no changes in the organisation at On the basis of the documentation submit- KKB during the year under review. ted, on 7 August, the HSK was able to grant the execution permit to start building the HAA/

HSK Annual report 1996 • Beznau Nuclear Power Planl 15 BE hall at ZWIBEZ for which the authorisation worked out for testing during operation. This had already been granted in May 1991 by the concept is to be presented to the HSK. Federal Council. Building work on the storage - From 1995, verification of the safeguard sys- facility started immediately. tem during the revision outage is to include full testing of all trip signal combinations. The concept was presented on schedule. As 1.7 Compliance with licensing required, the complementary verifications are carried out periodically during operation. The conditions for KKB Unit II second point of this licensing condition, de- The status of compliance with the licensing manding complete testing of all trip signal com- conditions in connection with the operating binations during the revision outage, has been licence of December 12 1994 is as follows: running successfully since 1995. Licensing condition 3.4. is fulfilled. The HSK will follow Condition 3.3 this up. Methods to examine the presently untestable weld seams on the reactor cooling circuit are Condition 3.5 to be investigated; a suitable method is to be The auxiliary feedwater system is to be im- presented to the HSK by 31 December 1995. proved with regard to system reliability and system capacity so that, in addition to residual heat The proposal was presented on schedule. removal, it should be possible, at the same time, - Two circumferential weld seams at the base to speed up plant shutdown, taking into con- of the reactor pressure vessel and two on sideration the single failure criteria. Proposals the vessel head were concerned. During the for the system improvements are to be handed 1995 refuelling outage, the two circumfer- to the HSK by 30 June 1995. ential seams of the vessel base were exam- The concept proposal, submitted on sched- ined and this examination has been inte- ule, for improving the auxiliary feedwater sys- grated into the periodic inspection tem was commented upon by the HSK and then programme. The feasibility study for the ex- revised by the NOK. The revised technical re- amination of the vessel head circumferen- port for an additional emergency feedwater train tial weld, submitted at the end of 1995, has was presented to the HSK, who granted the been put in concrete terms so that during execution permit at the beginning of Decem- the next Unit I outage, examination can start ber 1996. Implementation has started and it on these seams. should be completed in 1999. - In the case of the reactor coolant pipes, the planning phase is longer because of the Condition 3.6 complexity of the examination problem and Plant service supply and emergency electrical the state of technology. For this reason, the supply HSK detailed the investigation and planning The following improvements in the plant serv- steps that were needed as evidence that ice supply and emergency electrical supply are NOK had fulfilled the licensing condition by to be completed by 31 December 1996: the end of 1995. From the study submitted - Completion of the automatic generator in response, it could be seen that, with the breaker function and elimination of the auto- current state of technology, examination is matic feedback from 1EtoOE buses; feasible, and appropriate offers have been - Creation of an independent and reliable obtained from specialist firms. The study lists emergency power supply for train 24; further steps demonstrating the feasibility of - Improvement of the disconnecting device of the examination. the main feedwater pump on train 24 in the With the above findings and the existing docu- operating mode "emergency electrical sup- mentation, the licensing condition 3.3 is formally ply"; completed. Within the frame of its supervision - Completion of the systematic allocation of the HSK will follow up on further action to be 1E equipment to the diverse trains. taken. These four requirements were fully met during the 1995 outage. Condition 3.4 Licensing condition 3.6 also implies a fifth Safeguard system requirement: - Additional verifications in the safeguard sys- Investigations have to be made by 30 June tem are to be made at regular intervals dur- 1995 on the safety benefits and feasibility of ing each subsequent fuel cycle. By the 1995 planning a further supply for the NANO sys- revision outage a concept should have been tem.

16 HSK Annual report 1996 • Beznau Nuclear Power Plant This requirement was also met on sched- into operation - even though both units were ule. The investigation showed that the safety shut down for revision. Also, the release of ra- benefits to be expected from a further NANO dioactive materials to the environment lay well supply would be very slight. The HSK and KSA below the limits set by the authorities. came to the same conclusion. Licensing con- The events which occurred, including the one dition 3.6 is therefore fulfilled. classed as INES level 1, were of low significance for nuclear safety. Condition 3.7 The cloakrooms for the controlled zones are to be adapted according to the concept of HSK Guideline R-07. Special attention must be paid to the consistent segregation of "hot" and "cold" changing room areas. All adaptations must be completed by 31 December 1997. The rebuilding work on the cloakrooms is already so far advanced that the deadline for completion, the end of 1997, will be met.

Condition 3.8 A systematic programme, specific to KKB, for ageing surveillance is to be devised and followed. This programme is to be presented by 31 December 1995 for the main structures and for the electrical and mechanical installations affecting safety. The most important parts of the ageing surveillance programme required by the HSK were delivered on time. Programmes have been drawn up for both power plant units. This means that ageing surveillance has become a permanent task for KKB and will continue to be followed up by the HSK. Licensing condition 3.8 is therefore fulfilled.

Condition 3.12 The applicant is to make a systematic examination and evaluation of the safety culture within the organisation and to present the results to the safety authorities by 31 December 1997. KKB is currently working on this licensing condition.

Remark: Although all the above licensing conditions are legally applicable to KKB II, the operating organisation will also apply them to KKB I.

1.8 Overall judgement by HSK

The condition of both units with regard to nuclear safety and radiation protection and also to their operation can be rated as good. The safety status of the plant was improved, particularly with regard to the emergency power supply. The use of extensive shielding was the main cause that the collective dose, both for own and external personnel, reached the lowest level since the Beznau nuclear power plant came

HSK Annual report 1996 • Beznau Nuclear Power Plant 17 Blick in den Kommandoraum des Kernkraftwerks Muhleberg Coup d'oeil dans la salle de commande de la centrale nucleaire de Muhleberg View of the control room of NPP Muhleberg 2. Muhleberg Nuclear Power Plant

2.1 Operational data and according to Guideline R-15 and as level 0 on the international INES scale (see section results 11.7 and Table B2 of Appendix B). The Muhleberg Nuclear Power Plant (KKM) - One Saturday, an alarm was triggered by two belonging to BKW FMB Energie AG is a boil- electronic comparators of the mass flowing water reactor with a net output of 355 MW. through monitor of a main steam line from This has been the official electrical power since two channels for initiating isolation of the 1 January 1994, as the thermal power was in- main steam lines. This alarm had no influ- creased by a total of 10% in 1993. KKM started ence on plant operation. Following test in- commercial production in 1972. Additional data structions the analogue values of the trans- are summarised in Tables A1 and B3 of the mitter and the reference voltage values were Appendix; Figure B2 gives a functional diagram checked, with no sign of any anomalies. A of a boiling water reactor plant. fault was assumed to lie in the signal com- In 1996 the Muhleberg power plant reached parison and therefore no further steps were a load factor of 84.5% and an availability factor instigated at that time. On the following Mon- of 89.3%. The annual revision with refuelling day, the anomaly was eliminated by replac- lasted 38 days. ing the limit signal controller. The defective The "Steinriesel" residential district received device was sent to the manufacturer for 3.1 GWh of thermal energy for domestic heating. tests, which showed that the limit signal con- The plant experienced one planned outage troller would not have been functional in case and one unplanned reactor scram during the of demand. year under review. During power production, Further investigations have shown that there were three planned power reductions to the protection system would have functioned allow for routine tests or functionality tests, and according to design, if needed. Despite the four power reductions resulting from failure of fault, the single failure criterion was always recirculation pumps. The causes of these fail- fulfilled, since there is a hydraulic coupling ures were rectified. of the main steam lines, which are connected in pairs. The operator made improvements in the methods used for localising anoma- 2.2 Plant safety lies and for checking whether the protection channels are in working order. 2.2.1 Particular events The incident was categorised in class B The following two notifiable events were re- at HSK and on INES level 0. ported by the operator according to reporting Guideline R-15: 2.2.2 Work during the refuelling - During a periodic functionality test involving outage three single tests at reduced reactor power, The normal tasks undertaken during the revi- an anomaly in the feedwater controls led to sion, such as refuelling, inspections, periodic a high level of reactor water, causing a examinations, functional tests on components turbine trip which in turn produced a reactor and systems, maintenance work, etc., went scram due to increased neutron flux. according to plan. The main activities and re- The cause of the fault was the failure of an sults are: analogue computer for measuring feedwater - Examination of the core shroud flow. The defective computer was replaced In 1990, cracks were found, for the first time, and checked. Furthermore, the operator is in the core shroud, a non-pressure bound- endeavouring to avoid any future faults of ing component in the interior of the reactor this type by changing the procedure for these pressure vessel (RPV). As a precautionary functionality tests. Since the behaviour of the measure, during the 1996 outage the core plant during reactor shut down was normal, shroud was fixed with tie rods (see also sec- and no operating instructions were infringed, tion 2.2.3 Plant modifications). The condi- this event was of little significance for safety. tion of the weld seams is being followed up The event was categorised as class B

HSK Annual report 1996 • Muhleberg Nuclear Power Plant 21 as part of the in-service inspection pro- systems. The examinations showed no in- gramme. admissible divergence from the required In 1996 the two circumferential seams most values. affected by cracks in the whole accessible area, about 80% of the circumference, were 2.2.3 Plant modifications subjected to the periodic ultrasonic exami- The main changes in the plant were: nation. This showed that since 1995 the - Modifications to the core shroud cracks had grown only minimally, i.e. about As a precautionary measure, the core shroud a millimetre. The crack depths have hardly was fixed by inserting four tie rods and changed over the past two years and in very spacers axially and radially in the RPV. The few places reach 60% of the wall thickness tie rods were installed on the outside of the of 31 mm. A short and shallow crack was core shroud. They were suspended from the found in a place that could not previously be uppermost flange of the core shroud and checked and that had only been made ac- tensioned down to the core shroud plate. In cessible in 1996. this way, even a complete crack round the In the upper part of the core shroud, visual circumference of the core shroud could be tests were carried out with a TV camera on kept under control. two vertical seams and on accessible areas - New neutron flux measuring system for of the core shroud support. No cracks were power operation found. During the outage, the existing neutron flux Visual examination inside the RPV measuring system for power operation was In the reactor pressure vessel, extensive replaced by the modern, programmable visual tests were carried out using remote Power Range Neutron Monitoring System controlled underwater video cameras. Apart (PRNMS), in which the Tracking Overpower from the above mentioned core shroud Protection System (TOPPS) was also imple- seams, the core spray pipes and the seams mented. The use of TOPPS improves reac- connecting the jet pump support with the tor monitoring with regard to slower tran- RPV wall were inspected. All these exami- sients. nations showed no indications of cracks. - Changes to the RPV water level measuring Examinations of the RPV and the system recirculation, feedwater and main steam In the 1996 outage, KKM replaced the con- pipes densate chambers with a newer type in the In the RPV the four main steam nozzles, a RPV water level measuring system. In addi- recirculation nozzle, a core spray nozzle, six tion, each of the two measuring sides has control rod penetrations, the vessel head been equipped with two reference legs with flange seam and half of the circumferential condensate chambers. The doubling up of seam between the vessel head cap and its the reference legs has made it possible to ring part were tested. Four weld seams of a equip each of the four redundancies of the recirculation pipe were tested. The wall thick- reactor protection system and the instrumen- nesses of the main steam and feedwater tation and control system for the ultimate lines in the drywell1 and the steam tunnel emergency cooling system with its own ref- were measured. These examinations were erence leg. With this set-up, a loss of steam done using ultrasonic and eddy current pro- or fluid from a reference leg can be control- cedures. led with no adverse consequences. All the test results obtained confirmed that - Shield wall ofthe steam tunnel the components examined were suitable for After mounting a sliding steel door at the per- further operation. sonnel entrance to the steam tunnel, the Electrical equipment shield wall in front of it in the reactor building With regard to the electrical equipment, is now protected from consequential dam- periodic examinations were done on the ages following a burst of the feedwater pipe instrumentation and control ofthe ultimate or main steam line in the steam tunnel. emergency cooling system and the reactor protection system. Further examinations and 2.2.4 Fuel and control rods checks were done on the diesel generator From the low concentration of activity in the sets ofthe emergency electrical supply and reactor water and exhaust gas throughout the of the ultimate emergency cooling system, year, it can be concluded that no fuel rod de- as well as on the switchgear. Necessary cali- fects occurred. Of a total of 240 fuel assem- bration work was also done on the safety blies in the core, 40 were replaced for the 24th fuel cycle (1996/97). All new fuel assemblies Drywell: Pressure chamber of the containment had a 9x9 fuel rod configuration.

22 HSK Annual report 1996 • Muhleberg Nuclear Power Plant During the 1996 outage, no depleted control make a significant contribution to the collec- elements were replaced. tive dose, since the work was done exclusively In order to check the operational behaviour underwater. of the fuel assemblies with a view to raising Compared with the previous year, the ambi- the discharge burnup, five fuel rods, that had ent dose rates on the recirculation pipes was been in service for different lengths of time, reduced by about 5%. This is in addition to the were inspected with an underwater camera 1995 reduction in the mean dose rate on the during the revision outage. All the fuel assem- recirculation pipes, which was almost 10% less blies inspected were in good condition. than in the previous year. The measures for reducing cobalt transport into the reactor wa- 2.2.5 Ageing surveillance programme ter are beginning to show a positive effect, two KKM continued with the ageing surveillance years after completing the replacement of the programme as required by the operating li- pins and rollers of all the control rods with new, cence. The documents concerning the main low-cobalt spacer sliders. components in the field of mechanical, electri- During the outage, to reduce the dose rate cal and civil engineering, were submitted to the in all working areas but chiefly in the dry well, HSK for assessment. The HSK will follow up in numerous radiation sources were again tem- greater depth on the implementation of ageing porarily shielded with a total of 70 tonnes of surveillance (cf. sections 2.7 and 11.3). lead sheeting. The permanent fixtures in the dry well for supporting the lead sheeting are now fully operational and allow the use of 2.3 Radiation protection thicker shielding and shorter installation times. The operator estimates that the dose saving 2.3.1 Protection of personnel achieved by using the temporary shielding, tak- The collective doses measured at KKM during ing into account the dose accumulated during the calendar year 1996 (1995 data in brackets) shielding work, is more than 1.2 man-Sv. were: Since the activity in the primary coolant was low, contamination in the turbine building was, Plant status man-Sv as in previous years, very low, which greatly Planned outage 0.89 (0.92) facilitated the work done there. Power operation 0.51 (0.56) There were no individual doses which exceeded the limit. In 1996, there were no radio- Annual collective dose 1.40 (1.48) logical events classifiable under Guideline The collective dose received during the outage R-15. The incorporation measurements of own was a record low, despite the extent of the work and external personnel using the quick coun- undertaken. This was achieved by efficient ra- ter before and after a period of time in KKM diation protection, the use of extensive shield- produced no significant findings. There was no ing and making a daily comparison between spread of contamination nor contamination of target and actual doses in all fields of work. persons which could not be removed by nor- The dose was well below the dose forecast for mal washing. the outage of 1.2 to 1.5 man-Sv. The total an- The highest individual dose from external ra- nual collective dose is also low and lies well diation was 11.8 mSv in 1996. The compara- below the HSK guideline of 4 man-Sv. ble value for 1995 was 13.5 mSv. Further de- In three special areas of work, the forecast tails can be found in Tables A5 to A10 and for the dose was over 0.05 man-Sv and, in line Figures A5 to A10. with HSK guidelines, appropriate measures for radiation shielding were taken. The effective 2.3.2 Releases to the environment collective dose in all areas lay well below the and direct radiation planned limit. The three areas of work con- Table A4 shows the prescribed limits for the cerned: releases of radioactive materials, the annual - Revision of armatures, valves and pumps in releases for 1996 and the worst-case dose the dry well, including the control rod drives calculated for an individual in the vicinity. No - Exchange of the reactor water level meas- limits were exceeded. Taking into considera- uring device tion the dose contributions from previous years, - Improvement of the snubbers of the main the calculated annual dose is 0.01 mSv for steam lines adults and 0.008 mSv for infants. Doses due to releases in 1996 were significantly lower. The work on the core shroud placed great de- Articles 5 and 6 of the Radiation Protection mands on the staff in terms of avoidance of Ordinance state that activities involving an ef- spread of contamination. It did not, however, fective dose of less than 0.01 mSv per year for

HSK Annual report 1996 • Muhleberg Nuclear Power Plant 23 the persons concerned are deemed justified control room, is a copy of the real KKM control and optimised. This means that no further ef- room. The lifelike simulation provided by the forts are necessary to reduce radioactive re- installation gives the shift staff an opportunity leases and the resulting dose for the general to exercise on operating modes and measures public. for controlling abnormal events which seldom The quarterly monitoring by the HSK and the occur in practice. This is of particular signifi- SUeR of KKM aerosol and iodine filters and of cance because, due to retirement, the number exhaust gas and waste water samples showed of operators with experience gained during the a good correlation of results in the three labo- start-up phase of the plant is declining. Also, ratories involved. the almost faultless operation of the plant pro- The dose rate monitoring network (MADUK) vides individual operators with very few oppor- detected no significant increase in the ambient tunities to experience plant behaviour during dose rate above the background radiation in such events or to use the information about the vicinity of KKM. In the immediate vicinity of event control gained during training. the nuclear power plant, the ambient dose rate Previously, KKM operators were trained on is higher due to direct radiation from the tur- the simulator of a similar plant in the USA. Now bine building and the waste storage facility. The the plant has its own simulator in operation, on emission limits, given in Art. 102 clause 3 of site and available to operators at all times. The the Radiation Protection Ordinance, of 5 mSv HSK welcomes the installation of this plant- per year and the guide value given in the HSK specific simulator, which, as a key element in Guideline R-11 of 0.1 mSv per week for the training, should contribute significantly to in- ambient dose from direct radiation were also creasing safety. adhered to in the year under review. The specialised departments also pay particular attention to training of specialist person- 2.3.3 Radiation protection instru- nel, as evidenced by the large number of train- mentation ing courses attended. They help to keep the During the year under review, monitors went specialist knowledge of KKM personnel up to into operation in the annexe of the south tur- the latest state of the technology. bine building for keeping track of dose rate and the aerosol activity. The other measuring de- 2.4.2 Organisation and operational vices for monitoring activity and radiation lev- management els in the plant, and also all radioactive releases As part of the rationalisation of the organisa- to the environment, the personnel monitors, and tion, KKM created a new Services Department, the individual dosimetry systems all functioned which includes the new Technical Services (pre- properly during the year under review. KKM viously: Technical Staff), Administration and successfully participated in the annual com- Plant Guard. parative measuring for individual dosimetry KKM has continued the quality management services organised by the EKS, producing evi- project and built up a system based on the re- dence of the required accuracy of measure- quirements of IAEA Safety Series No. 50-C-QA ments. together with sections of the ISO 9000ff standards. The KKM quality assurance manual has been sent to the HSK for assessment. 2.4 Personnel and organisation The HSK welcomes the implementation of a formal quality management system at KKM. It 2.4.1 Personnel and training will enable proper specifications to be given for Two reactor operators (level A) and a shift chief periodically occurring processes and the pro- were licensed after successfully passing the cedures connected with them. As a result, it examinations. Two persons successfully will be possible to follow up and optimize rou- passed the examination to become radiation tine activities in a controlled manner, and out- protection chief controllers. The total number siders, e.g. the HSK, will have a better over- of licensed personnel is given in Table A2. The view of the KKM's methods of conducting daily total work force at the end of the year under operations. review was 285 persons (1995: 284). On 3 July 1996, the KKM simulator was started up and handed over for operation. This 2.5 Emergency preparedness now makes possible an extremely accurate simulation of normal operation as well as op- The KKM plant emergency exercise "BERTA" erational occurrences and accident conditions was held in the autumn. The objective was to of the plant. The interface between the simula- control a postulated loss of coolant accident in tor and the shift team, which is the simulator the drywell with simultaneous failure of several

24 HSK Annual report 1996 • Muhleberg Nuclear Power Plant operational and safety systems. The scenario The raw wastes collected for later treatment assumed that the accident had led to core dam- are stored in an unconditioned form in rooms age resulting from lack of possibilities for cool- in the controlled zone. Conditioned waste pack- ant supply and coolant injection. This resulted ages are routinely brought to and held in the in a build-up and deposition of activity in the interim storage building. drywell with leakage from the drywell into the reactor building. Radioactive materials were released into the environment from the emer- 2.7 Fulfilment of licensing gency exhaust air system. During the "BERTA" exercise, the emergency team had their first conditions chance to work in the new rooms of the multi- Apart from the conditions of the current opera- purpose building. In the course of the exercise tion licence of 14.12.1992 demanding a peri- it was also possible, among other things, to odic plant safety review or update of important assess the suitability of this new infrastructure plant documents (safety report, risk study), for the tasks of the emergency team. some follow-up measures for fire protection and The new rooms proved to be basically sound. the ageing surveillance programme are still However, some alterations could still be made open. to the infrastructure to make it more suitable In the area of fire protection, the smoke and for use during emergency situations. The KKM heat removal devices required by the HSK in services which took part in the exercise co-op- the reactor building were upgraded. This meets erated well and demonstrated a high level of the licensing conditions concerning structural training. aspects and technical equipment for fire protection. Operational and administrative aspects remain open. 2.6 Radioactive wastes In the area of ageing surveillance, the licensing condition was basically met, but the opera- During the year under review the quantity of tor must, in future, give higher priority to the raw radioactive wastes (see Table A11) was as development of the follow-up and permanent expected, judging from the experience of pre- programme. vious years. Mixed wastes were transferred to the PSI, where combustible wastes were incinerated and the incineration residue 2.8 Overall judgement by cemented. The resulting packages of conditioned wastes were returned to KKM. the HSK The Cement Volume Reduction and Solidifi- The Muhleberg nuclear power plant can be cation plant (CVRS), for conditioning of resins, certified as being in a safe condition and well concentrates and slurries went into operation operated. The safety status of the plant was for the first time and ion exchange resins and further improved over the previous year by also sump and laundry slurry were cemented modifications made to the plant. From a radia- in accordance with the provisional execution tion protection point of view it is pleasing that permit granted by the HSK. Parallel to this, KKM the dose rate in the recirculation loops was drew up the final specifications for the six types again significantly reduced and also that, of CVRS package planned. NAGRA has evalu- despite extensive work, a low collective dose ated and certified these six types of waste pack- was achieved. Both the collective dose and the age as suitable for final storage. However, dur- release of radioactive materials into the envi- ing suitability evaluation, certain requirements ronment were well below the limits set by the were not met. KKM therefore carried out a cam- authorities. The two reported events had little paign in autumn 1996 to optimise the process, significance on nuclear safety. based on the results of trials and operational data available to date and on basic chemical considerations. The measurements and analyses of the complementary programme of examination and suitability testing for type approval will take until mid 1997. Until the method receives a final execution permit, the CVRS solidification plant will be used solely to process resins produced during operation. Routine cementing of unsolidified resins from previous years of operation, currently stored in the interim storage building, will start in autumn 1997.

HSK Annual report 1996 • Muhleberg Nuclear Power Plant 25 Montage von Steuerstabantrieben am Reaktordeckel des Kernkraftwerks Gosgen Montage des entrainements des grappes de commande sur le couvercle de la cuve du reacteur de la centrale nucleaire de Gosgen Montage of control rod drive mechanisms on the reactor pressure vessel upper head in NPP Gosgen 3. Gosgen Nuclear Power Plant

3.1 Operational data and loading pool. The top part of the rod was bent, but remained tight. No radiological results effect could be observed. The fuel rod lifting The Gosgen nuclear power plant (KKG) is a 3 equipment was fitted with a device to prevent loop pressurised water reactor with a net elec- falling. Its efficiency was proven during fur- trical output of 970 MW. It came into operation ther work on fuel rods. in 1979. At the beginning of the year, the net - During the monthly functionality testing of a output was adjusted upward by 5 MW in view diesel motor of the ultimate emergency cool- of the improved efficiency of the turbine. Addi- ing system, the motor tripped following the tional data are summarised in Tables A1 and aggregate protection signal, "pressure low", B3 of the Appendix; Figure B1 gives the func- from the cooling water circuit. The subse- tional diagram of a pressurised water reactor quent inspection revealed a cleaning rag plant. which had blocked the pipe from the surge In 1996, KKG achieved a load factor of tank. On removal of the rag, the functional- 93.6% and an availability factor of 93.4%. The ity test was successfully repeated. planned refuelling outage lasted 24 days and - While shutting down the plant for the annual was the main cause of non-availability of the revision, during a functionality test, a main plant. In the year under review, the plant deliv- steam safety valve did not open within the ered 142.2 GWh process heat to the nearby prescribed pressure range. During the sub- carton factory. sequent inspection, no defect could be found Plant operation was not interrupted by any on the main valve or on the control equip- unplanned reactor scrams and there were no ment. It can be assumed that the valve would significant power reductions. have opened in case of a higher pressure. The cause of the failure lay in the response pressure of the pilot valve being set too high. 3.2 Plant safety After consultation with the manufacturer, the minimum response pressure of all the pilot 3.2.1 Particular events valves was set lower. During the start up of Based on Guideline R-15, "Reporting on the the plant, the functionality test was success- operation of nuclear power plants", the opera- fully repeated: the main steam valve oper- tor gave notification of the following events: ated correctly. - During the last cycle, fuel rod damage was - A further event occurred during a periodic suspected due to the slight increase in ac- functionality test of a containment shut-off tivity in the primary circuit. This finding was armature of the sampling system. This confirmed by the fuel assembly inspection armature, which is open during normal performed during the annual outage; dam- operation, failed to close. The cause was age was found in two fuel rods in two fuel discovered to be a defective electronic com- assemblies of the 16th refuelling. None of ponent When this was replaced, the test the assemblies of that refuelling were re- was run successfully. used, they had been in service for one or The five notifiable events described above were two cycles. The damage was due to frictional rated as Class B according to HSK Guideline wear following stress corrosion cracking on R-15 and involved two human errors, a setting the spring in the lower spacer. As this type error and two component failures. The signifi- of damage had been discovered the previ- cance of the events with regard to safety was ous year in the 13th refuelling, the lower minimal. On the international INES scale (see spacer for the 16th refuelling was also re- section 11.7 and Table B2 in Appendix B) they placed by an Inconel spacer which is more correspond to level 0. resistant to stress corrosion cracking. - During the inspection of fuel assemblies of 3.2.2 Work during the refuelling the 13th refuelling, one rod slipped from the outage clamp fixture of the device used for remov- All the planned operations such as refuelling, ing fuel rods. The rod fell to the floor of the inspection, periodical examinations of mechani-

HSK Annual report 1996 • GAsgen Nuclear Power Plant 29 cal and electrical components, functionality total of 31 valve actuators have now been tests of components and systems, mainte- replaced. nance, etc. were carried out. - In all the three main feedwater pumps, the Some important activities are mentioned: pump shaft was replaced by one of better - In steam generators 1 and 3 all the tubes construction. were subjected to eddy current tests. Most - In order to increase the operating time of fuel of the significant findings were in the area assemblies in the core from 3 to 4 cycles above the tube sheet. They are virtually iden- and to allow the use of MOX fuel, the maxi- tical to the findings of previous tests. One mum boric acid concentration in the primary pipe had to be plugged. circuit water was increased and also the - Subjected to the ultrasonic tests during the boron-10 isotope enrichment was raised. 1995 revision outage, one of the weld seams This ensures that adequate sub-criticality is of the primary circuit gave results with one maintained during normal operation and in finding that required some clarification. The accident conditions. seam was again examined in 1996 using - The second water intake was improved. The routine and special ultrasonic testing proce- work on the second train was similar to that dures. The finding was easily reproduced. done on one train in 1994. The diesel motor No significant systematic change was ob- was replaced by the reserve motor, the mitre served. However, a crack cannot be ruled gear was completely overhauled and the lu- out with absolute certainty. The finding will bricating oil pump was converted to direct be followed up. Afracture mechanics assess- drive. On the pump itself, the housing and ment showed that operation can continue, the suction cap were replaced with an ero- without any cause for concern, from a safety sion resistant material and the pump shaft viewpoint. mounting was made of a new maintenance- - Following the incident in the previous year free design. when a low-load shut-off valve in the - Two valves with hydraulic drive, used to cut feedwater system failed, the valve was com- off unnecessary consumers in the interme- pletely dismantled to try to discover the diate cooling loop during a loss of coolant source of the fault. No cause for this unique accident, were replaced by motor driven malfunction was discovered. valves. - Examination of the recuperative heat exchanger in the volume control system pro- 3.2.4 Fuel and control rods duced no significant findings. For the 18th operating cycle (1996/97) of the - A high-pressure charging pump and a main total of 177 fuel assemblies, 60 were replaced condensate pump, including the motor, were by new ones. The fuel rods of the new fuel as- subjected to a complete overhaul. semblies have a cladding whose surface has - Examination of the instrumentation and con- been coated with a protective layer to retard trol system, the regulation systems and the corrosion. reactor protection system produced no In the section "Particular events", a report is anomalies. given on the fuel rod damage which occurred - In the turbine building, the generator was in the 17th cycle. In the present 18th cycle, up completely overhauled. to the end of December 1996, inert gas activity The findings of the other inspections, exami- has increased slightly, indicating a fuel rod de- nations and tests gave no cause for concern fect. The nuclide-specific primary water activ- for safety. ity lies however, as in the previous year, well below the limits. 3.2.3 Plant modifications As before, working in co-operation with the In the year under review, the main changes fuel suppliers, various test fuel rods with differ- were as follows. ent material compositions for the cladding were - All the magnetic pilot valves on the last of inspected after being in use in the reactor core. the three main steam isolation valves were In general, the cladding behaviour was good. exchanged, together with their control Again, as last year, during the revision out- blocks. This leads to improvements in the age all 48 control rod assemblies were exam- magnetic force and to the position indicator. ined for weaknesses in the cladding using eddy - In order to ensure in accident situations over current procedures. There was no objection to the long-term reliability of the valve actua- the reuse of all control rods. tors, a further group of nine valve actuators No restrictions in the movement of control among those designated for replacement in rods, such as that seen in some foreign pres- the containment, were exchanged; 18 of the surised water reactors, have been observed.

30 HSK Annual report 1996 • Gosgen Nuclear Power Plant This was confirmed by additional fall time tests and refuelling), the following tasks also con- at the end of the 17th cycle. tributed to the doses: - Eddy current and ultrasonic examination of 3.2.5 Probabilistic safety analysis steam generators 1 and 3 (PSA) - Secondary side inspection of steam genera- As part of the periodic safety review (see also tors 1 and 3 section 11.4), the probabilistic safety analysis - Examination of the recuperative heat ex- (PSA) submitted by KKG was studied with a changer view to issuing an appraisal. In order to allow - Ultrasonic examination of the primary circuit detailed investigation, both qualitative and The annual collective dose was about the same quantitative, HSK is currently developing a order of magnitude as in the previous year and probabilistic plant model for Gosgen. This pro- well below the HSK guideline of 4 man-Sv. cedure has already proved its worth in earlier The numerous dose rate measurements PSA appraisals for Muhleberg, Beznau and taken in the primary circuit showed that the Leibstadt. doses at points of importance for radiation pro- In 1996, the "fault tree analysis" method was tection had remained constant, compared with used to calculate the reliability of all the KKG the previous year, or had continued to show a systems which could prevent core damage slight increase. Temporary shielding was again during a severe accident. The fault tree analy- used. In 1996 a total of 11 tonnes of lead sis allows a breakdown of system reliability to sheeting was installed, in particular for protec- the level of individual components. tion in working areas concerned with the steam The influence of operator actions on the generator. The effective saving in collective course of a severe accident (human reliability dose is estimated by the operator as about analysis, HRA) was analysed in the Gosgen 50 man-mSv. The use of temporary lead shield- PSA using expert opinions. In future, greater ing is not regarded by KKG as a dose saving attention should be paid to the HRA factor in measure on the basis of the optimisation con- the PSA appraisal. siderations. The effect of severe core damage within the There was no significant individual contami- containment was analysed in detail. A special nation and no spread of contamination. There investigation was made of damage to the steel was no appreciable release of radioactive ma- shell caused by steam explosions which could terials into the atmosphere of the reactor build- arise if liquid melt from the core escaped and ing, although, due to the defects in two fuel as- came into contact with water. semblies, there was relatively high iodine 131 contamination of the primary water, 2-107 Bq-rrr3 3.2.6 Ageing surveillance programme (previous year, with four damaged fuel assem- 7 KKG has begun the ageing surveillance pro- blies: 7-10 Bq-m^). gramme as requested by the HSK. The initial In 1996, there were no radiological events information concerning components from the to be classified under Guideline R-15. In no areas of mechanical, electrical and civil engi- case did individual doses exceed the limits. In neering has been submitted to the HSK for 1996, the highest personal dose through ex- assessment. The HSK will continue to follow ternal irradiation was 15.2 mSv. The corre- up the implementation of the programme (see sponding value for 1995 was 14.0 mSv. Fur- section 11.3) ther information can be found in Tables A5 to A10 and Figures A5 to A10.

3.3 Radiation protection 3.3.2 Releases to the environment and direct radiation 3.3.1 Protection of personnel Table A4 presents the admissible limits for the In the calendar year 1996 (data for 1995 in release of radioactive materials, the 1996 an- brackets), the following collective doses were nual releases and the worst-case doses calcu- accumulated at KKG: lated for individuals in the vicinity of the plant. Radioactive releases in the form of aerosols, Plant status man•Sv iodine and inert gases lay well below the limits. Planned outage 0.72 (0.90) This was also true for radioactive releases in Power operation 0.20 (0.19) waste water, excluding tritium; releases of tri- Annual collective dose 0.92 (1.09) tium, typical for a pressurised water reactor, were about 20% of the limit, as in the previous In addition to the normal refuelling work (involv- year. ing opening and closing the pressure vessel The quarterly control measurements performed on random samples by the HSK and

HSK Annual report 1996 • GSsgen Nuclear Power Plant 31 SUeR on aerosol and iodine filters, and also keep their expertise up to the latest state of the on waste water samples, confirmed the very technology. low level of releases at KKG in the year under review. 3.4.2 Organisation and operational Accordingly, the worst-case annual doses management calculated for an individual member of the pub- There were no changes in the organisation lic, 0.001 mSv for an adult and 0.001 mSv for structure in the year under review. an infant, are very low and lie far below the As part of the periodic safety review (PSR) guide value of 0.2 mSv/year in accordance with (see also section 11.4), HSK has started to build Guideline R-11. Articles 5 and 6 of the Radia- up a more in-depth and up-to-date overview of tion Protection Ordinance state that activities the organisation at KKG. In particular, this has which lead to an effective dose of less than included checking areas concerned with the 0.01 mSv per year for the person involved are KKG quality assurance programme. This will deemed as justified and optimised. This means also be useful in connection with the Nuclear that no further efforts must be made to reduce Safety Convention (IAEA/UNO) which came radioactive releases and the resulting dose for into force in the year under review. the general public. The dose monitoring network (MADUK) in the vicinity of the plant and the measurements 3.5 Emergency preparedness at the perimeter of KKG showed no significant rise above the background radiation. A plant emergency exercise was carried out at KKG in autumn. The scenario assumed that, 3.3.3 Radiation protection instru- following a major loss in the integrity of a fuel mentation assembly, the plant was shut down for early In the year under review, the system for elec- refuelling. As the pressure was lowered, the tronic personnel dosimetry was completely re- specific activity in the primary circuit rose fur- placed and, after the required tests and cali- ther; additionally an instrumentation line was bration, went into routine operation. broken in the containment. Contaminated All the other radiation protection measuring steam escaped into the operating rooms be- instruments and personnel monitors also func- cause a concrete lock above the main coolant tioned satisfactorily. KKG successfully partici- pump was opened prematurely. The employ- pated in the annual comparison measurements ees at this location reported the escape of by personnel dosimetry services, organised by steam; plant shutdown was therefore acceler- EKS, and was able to demonstrate the required ated. The employees in question had become accuracy of measurement. contaminated and when they passed a personnel monitor, an alarm was triggered. One em- ployee probably spent about half an hour in the 3.4 Personnel and organisation containment, and 5 others were there for about one hour. 3.4.1 Personnel and training In the scenario selected, the criteria for de- In 1996, one reactor operator was newly ciding whether this was an emergency or not licensed. The total number of licensed person- were indeterminate, lying in a "grey area" (no nel is shown in Table A2. The total work force clear infringement of emergency criteria). Af- of the plant at the end of the year under review ter consultation with the picket engineer, the was 376 persons (1995: 373). plant management decided quite correctly that, In the year under review, shift personnel with the lack of clarity, the situation should be attended various courses on simulators in treated as an emergency. Essen (Gesellschaft fur Simulatorschulung - The HSK was convinced that the emergency simulator training school) and on a simulator organisation of KKG is properly able to cope of the FURNAS electricity company in Brazil. with an incident of this nature. In September 1996, KKG placed an order for a simulator for training shift personnel and began the construction of a training building on 3.6 Radioactive wastes the plant grounds. The plant's own simulator is expected to come into operation for training During the year under review, the quantity of shift teams in about three years from now. raw radioactive wastes (see Table A11) was as Members of the specialist departments at expected, judging from the experience of pre- KKG attended various internal and external vious years. Ion exchange resins were condi- courses as part of their professional training to tioned with bitumen, in accordance with the HSK execution permit. Mixed wastes were sent

32 HSK Annual report 1996 • Gosgen Nuclear Power Plant to PSI for sorting and treatment. There, the combustible wastes were incinerated and the ashes and non-combustible wastes were cemented. The packages of conditioned wastes produced and the separated compressible wastes were returned to KKG. For a concentrate with higher activity con- tent, KKG had defined a new type of package called "Dekontldsung". KKG has drawn up the specifications for this waste type fixed in bitumen and submitted the specification to NAGRA for verification of the suitability for final disposal. Furthermore KKG has now fully documented three waste package types from earlier production. The raw waste collected with a view to later treatment was kept in premises in the controlled zone. Conditioned wastes were routinely brought to and held in the interim storage facility. In order to prevent the build up of radiolysis gases in the storage shafts for the wastes in bitumen, the shaft covers were fitted with open- ings as required by the HSK.

3.7 Overall judgement by the HSK The plant condition and the operational management at KKG can be rated as good with regard to nuclear safety and radiation protection. The events which occurred had only a very slight significance for safety. The problem in connection with the full assembly spacers is recognised. Additional steps are being taken to avoid further fuel assembly damage. The amount of radioactive material released to the environment was very low and lay well below the limits set by the authorities. The individual doses accumulated were below 20 mSv. The annual collective dose for personnel lay well under the HSK guideline of 4 man-Sv.

HSK Annual report 1996 • Gosgen Nuclear Power Plant 33 11S/5t

Offener Reaktordruckbehalter im Kernkraftwerk Leibstadt Cuve du reacteur ouverte a la centrale nucleaire de Leibstadt Opened reactor pressure vessel in NPP Leibstadt 4. Leibstadt Nuclear Power Plant

4.1 Operational data and testing of 15 control rod penetrations and the visual inspection of the reactor pressure ves- results sel and the reactor vessel internals using tel- The Leibstadt Nuclear Power Plant (KKL) is evision techniques. The inner surfaces of the equipped with a boiling water reactor with a net main coolant pipes between the reactor outlet electrical output of 1030 MW. Additional data nozzles and the inlet pump nozzle of the main concerning the plant are summarised in Tables coolant pumps were also inspected using a tel- A1 and B3 of the Appendix, Figure B2 gives evision camera. the functional diagram of a boiling water reac- A visual inspection and a water pressure test tor plant. were carried out on a heat exchanger of the In its 12th year of operation, the Leibstadt ultimate emergency cooling system. power plant reached a load factor of 85.4% and On the secondary side of the plant, a series an availability factor of 88.7%. This time the of vessels was subjected to both visual inspec- revision outage lasted 41 days. Availability was tions and dye penetration tests. also influenced by a comprehensive test pro- Wall thickness measurements of piping on gramme carried out during the plant startup the secondary side were continued as part of following the outage at the beginning of Sep- the programme begun in 1990 to analyse weak tember, and also by a disconnection of the gen- spots due to erosion-corrosion. erator from the grid following a fault in the out- During the maintenance work, examinations door switch-yard in December. and inspections, no defects were found which During the period under review there was would indicate any impairment of the safety of no automatic reactor scram. the plant. The leakage tests on the closure devices of the containment apertures confirmed that the tightness of the containment is up to 4.2 Plant safety requirements. 4.2.1 Particular events 4.2.3 Plant modifications In accordance with the R-15 Guidelines con- In the year under review, a number of plant cerning reporting, the operator reported the modifications were carried out, most of them following notifiable event: during the annual outage. These were neces- Since October 1996, increased activity of the sary partly for nuclear safety and partly to meet reactor water and exhaust air has indicated the operating requirements. The main changes presence of a defect fuel rod. The cause of the were: damage can only be investigated during an out- - Exchange of the feedwater one-way flaps age. The event has been rated as class B accord- The existing 6 feedwater one-way flaps - ing to HSK Guideline R-15. On the international three in each of the two feedwater lines - evaluation scale INES (see section 11.7 and Ta- were replaced by damped one-way valves. ble B2 in Appendix B), this corresponds to level 0. This means that the feedwater lines to the reactor and their mounts are capable of with- 4.2.2 Work during the refuelling standing the pressure impuls due to a pos- outage tulated pipe rupture in the turbine building. During the annual outage from 27 July to 5 Sep- One of the valves did not quite meet the tember, the usual tasks were performed, such specified sealing requirements. This devia- as refuelling, maintenance work, periodic ex- tion has only a negligible influence on plant aminations of components, plant modifications, safety. The HSK has requested that this be inspections and functionality tests of systems corrected during the 1997 outage. and components. - Improvement of instrumentation in the emer- The periodic non-destructive examinations gency control rooms of mechanical equipment of the reactor in- As part of the measures against severe ac- cluded the ultrasonic checking of the longitudi- cidents, instruments were backfitted in the nal and circumferential weld seams of the pres- emergency control rooms to monitor the neu- sure vessel, the ultrasonic and eddy current tron flux in the reactor, the parameters of the

HSK Annual report 1996 • Leibstadt Nuclear Power Plant 37 containment and the emission of radioactive been fitted with an alternative foreign body filter materials in vented air. without moving parts. - Work begun during the 1995 outage contin- When the present 13th cycle started, the ued on the replacement of the T-pieces of core was defect-free; since October 1996 there the hydraulic control units of the control rod have again been indications of a fuel assem- drives. This was realised using pieces of bly defect. improved construction, with a view to avoid- ing vibration-induced cracks. It is planned to 4.2.5 Probabilistic safety analysis equip all 149 control units with new T-pieces. (PSA) - Work which had begun in 1995, to prevent As part of review and assessment of the appli- corrosion damage in that part of the plant cation for the plant power uprate, the HSK car- around the condenser, was completed upon ried out a thorough, largely independent, inves- the renovation of the air coolers. tigation of the study submitted by the plant - On the secondary side of the plant, in con- operator concerning plant risk. The results and nection with the application for the power the most important findings are documented in uprate, the following were replaced: the high the HSK safety evaluation report on the power pressure turbine, the turbine control valves uprate, published in May/June 1996. and the set of armatures for controlling the The overall frequency of core damage will turbine by-pass and discharge of the main not change noticeably because of the re- steam into the condenser. Modifications quested 15% power increase. A change would were also made to pumps and equipment clearly lie within the inherent dispersion range on the secondary side of the plant. of results for such analyses. For this reason, During startup of the 13th operating cycle, a the HSK opted not to make a quantitative state- comprehensive test programme was carried ment in their own analyses. A change is hardly out to show that the new components in the expected, since all technical measures have main control circuits and of the whole plant been implemented to ensure that the plant can were functioning properly under transients also be operated safely at the increased power following the plant modifications. The HSK level and since, in particular, the so-called sys- was present throughout this test programme. tem success criteria will remain valid without - For the protection of staff during accident any change. conditions, the ventilation of the control room On the other hand, the risk for the vicinity of was modified at the end of 1996. In such the plant, defined as frequency times released cases, a special operating mode of the ven- activity, would increase by a factor of about tilation system maintains overpressure in the 1.2-1.3 with increased power capacity. The rea- main control room and filters out any airborne son for this lies in a power-proportional increase radioactive materials in the incoming air. of the radioactive material inventory in the core and in the somewhat faster development of an 4.2.4 Fuel and control rods accident, both inherent phenomena. The HSK In the 12th fuel cycle (1995/96) the activity of considers that this risk increase, verified by the reactor water and exhaust air gave no indi- calculation, is acceptable because the risk of cation of any fuel assembly damage. During the Leibstadt plant is very small and has been the annual outage, all the fuel assemblies were consistently reduced over the years, thanks to tested using the sipping procedure and one fuel plant improvements. For this reason, the risk assembly was found to be slightly defect. The of the Leibstadt plant, even with increased fuel assembly in question was anyway going to power, will be at least 45% less than in 1990. be removed from the core. Investigations into the The operator submitted the improvements cause of the damage are still in progress. and additions to the PSA study as requested The spring-type foreign body filters, fitted to by the HSK by the end of 1996, on schedule. 8 fuel assemblies during the 12th fuel cycle, According to the revised study now available, proved unsuccessful in reactor operation, as the total core damage frequency through inter- was the case in other plants. During inspec- nally and externally caused events amounts to tions of these filters, vibration induced wear 2.7-10"6 per year. This result is even better than marks and broken springs were found. This shown in the HSK safety evaluation report and type of filter will no longer be used. proves once more that KKL, evaluated in this For the 13th fuel cycle (1996/97), 112 of the way, is one of the safest nuclear power plants total of 648 fuel assemblies were replaced by in the world. new ones during the outage. With the exception of 2 fuel assemblies, the reactor core now 4.2.6 Ageing surveillance programme contains only fuel assemblies with 10x10 fuel The KKL examined the most important com- rod configuration. Four fuel assemblies have ponents requested by the HSK in the field of

38 HSK Annual report 1996 • Leibstadt Nuclear Power Plant mechanical, electrical and civil engineering pha ratio for various components measured ex- under the programme for ageing monitoring ternally, it can be assumed that there was no and submitted the results to the HSK for ap- significant incorporation of alpha emitters. praisal. The HSK will continue to follow up the The mean value of the dose rate at the plant's implementation of this programme (see recirculation loops, 1.82 mSv/h, is the lowest section 11.3). since 1987. The dose rates on components of the reactor pressure vessel, that have been monitored over many years, either remain con- 4.3 Radiation protection stant or exhibit a very slight upward trend. To reduce the dose rate, 63 tons of tempo- 4.3.1 Protection of personnel rary shielding were installed, of which 55 tons In the calendar year 1996 (data for 1995 in were lead. During the shielding work, a total of brackets) the following collective doses were 43.5 man-mSv were accumulated. This is more found at KKL: than offset by the dose reduction of about 1 man-Sv. Plant status marvSv During 1996 there were no radiological Planned outage 1.53 (1.02) events which would have to be classified un- Power operation 0.45 (0.64) der the R-15 Guideline. Individual doses never Annual collective dose 1.98 (1.66) exceeded the limit. In 1996, the highest individual dose from external radiation was Both the collective dose for the outage and 11.0 mSv(1995: 14.6 mSv). For further details the annual collective dose corresponded to the refer to Tables A5-A10 and Figures A5-A10. values forecast. Because of the comprehensive work undertaken, the outage collective dose is 4.3.2 Releases to the environment higher than the previous year; however, it lies and direct radiation well below the HSK guideline of 4 man-Sv. Table A4 shows the limit values for the release The statutory optimisation requirements of radioactive materials, the total amount re- were satisfied using the very detailed written leased in 1996 and the resulting calculated radiation protection plans produced for the fol- worst-case dose for individuals in the vicinity. lowing non-routine, dose-relevant areas of None of the limit values was exceeded. KKL work: releases to the environment were slightly lower - replacement of two feedwater one-way flaps than those in the previous year. For adults, the in the drywell calculated annual dose, taking into account the - replacement of four feedwater one-way flaps depositions from the previous years, is in the steam tunnel 0.001 mSv and for infants 0.002 mSv. Articles - periodical examinations 5 and 6 of the Radiation Protection Ordinance - renovation of the air coolers associated with state that activities resulting in an effective dose the condenser of less than 0.01 mSv per year can be deemed Furthermore, by training the servicing team on justified and optimised. This means that it is 1:1 models, it was possible to optimize work- unnecessary to undertake further efforts to re- ing procedures and thus reduce the radiation duce radioactive release and the resulting dose dose significantly. This year, models were built for the general public. for the following tasks: The quarterly measurements carried out by - renovation of the air cooler associated with the HSK and the SUeR on KKL aerosol and the condenser iodine filters, and on waste water samples, - replacement of the feedwater one-way flaps again showed good agreement between the - examination of the control rod penetrations results for the three laboratories concerned. The radiological condition of the plant coincided The dose rate monitoring network (MADUK) largely with that of the previous year. It had to detected no significant increase in the ambient be expected that, with respect to the alpha con- dose rates above the background radiation in tamination caused by fuel assembly damage the vicinity of KKL. In the close proximity of the in previous years, similar conditions would nuclear power plant, the ambient dose rate of again arise in the wake of the outage revision direct and scattered radiation from the turbine work in 1994 and 1995. The alpha measure- building increases during operation. The HSK ment programme, which was satisfactorily carried out quarterly measurements also at the tested in the previous years, was repeated. KKL perimeter. The emission limit value under A total of 1788 persons were subjected to Art. 102, clause 3, of the Radiation Protection entry and exit measurement using the incor- Ordinance of 5 mSv per year and the guide poration monitor; no cases of beta/gamma in- value according to the HSK Guideline R-11 of corporation were found. From the gamma/al- 0.1 mSv/week for ambient doses through direct

HSK Annual report 1996 • Leibstadt Nuclear Power Plant 39 radiation were not exceeded during the year were submitted to the HSK for appraisal. In under review. various areas of the KKL, departmental and interdepartmental quality audits were carried 4.3.3 Radiation protection instru- out to check the efficiency of the quality man- mentation agement system. The radiation protection measurement instru- The international group of IAEA experts, who ments for monitoring releases to the environ- examined the KKL in 1994, within the frame of ment and the activity and radiation levels in the an OSART mission, submitted a report with plant, and also the personnel monitors and sys- suggestions for improvements in different ar- tems for individual dosimetry, all functioned as eas. In December 1996, a smaller team from required. The KKL successfully participated in the IAEA followed up and assessed the imple- the annual comparison measurement for indi- mentation of these suggestions. OSART con- vidual dosimetry which is organised by the EKS, firmed that the level of implementation at KKL and was able to demonstrate the required ac- was high; two solutions were found to be ex- curacy of measurement. cellent and were recommended for wider use. At the same time, however, it was stressed that the process of critical self-appraisal should be 4.4 Personnel and organisation ongoing and can never be considered finished. The HSK came across visible signs of the 4.4.1 Personnel and training positive effects of the OSART recommenda- In the year under review, five reactor operators tions during their plant inspections throughout and a shift chief were licensed. One person the year. qualified as a chief radiation protection controller. The total number of licensed personnel is given in Table A2. The total work force of the 4.5 Emergency preparedness plant at the end of the year was 407 persons (1995:408). During the year under review the "FORTUNA" During the year under review, KKL's new nu- combined emergency exercise was carried out clear power plant simulator was used exten- within the framework of INEX 2 (International sively for training shift personnel. The simula- Nuclear Emergency Exercise 2). In addition to tor is very realistic and readily available as it is the emergency organisations of the HSK and located on site. These factors have a very posi- KKL, an exercise of this type also includes the tive influence on the simulator training pro- emergency teams from the canton of Aargau, grammes. the Confederation and foreign authorities. During the annual revision, several hundred The basic scenario, chosen to be at the INES employees from outside firms are engaged in level 2 (see Appendix, Table B2), postulated a work at the plant, under the supervision of the phase I in which, following the fracture of the plant staff. To optimise this supervision, KKL rotor disc blades in the low pressure turbine, introduced a special management training the turbine housing was perforated and, in the scheme for supervisors responsible for outside intermediate superheater (west), a steam pipe staff. and cooling water piping in the main condenser During the year under review quite a number were ruptured. As a result, the turbine building of KKL employees again attended different windows burst, allowing slightly radioactive training courses in order to keep their techni- steam containing inert gases, iodine and aero- cal expertise up to date. In addition, seminars sols to escape; the levels of activity were nev- were held on quality management and quality ertheless below the short-term release limits. audits, and instructors on the simulator train- Due to a high vibration level, the turbine ing programme attended a didactics course to switched off automatically, but a bearing and a develop training skills. The emergency team generator seal had been damaged. Oil and participated at a seminar for co-operation with hydrogen were released causing an explosion outside agencies, together with the emergency which was followed by a fire. The smoke pour- team from KKB and the cantonal police of ing out of the broken turbine building windows Aargau. was easily visible in the vicinity. During phase II of the exercise, hydrogen 4.4.2 Organisation and operational and oil vapour entered the activated carbon fil- management ter of the exhaust gas system via a defective There were no organisational changes. stop valve in the vent gas unit, and within about KKL has revised the rules for quality manage- 6 hours a fire had developed. This then led to a ment, formulating the regulations in a more build-up of pressure and deflagration in the vent compact form to improve clarity. The new rules gas system. Considerable quantities of inert

40 HSK Annual report 1996 • Leibstadt Nuclear Power Plant gases and aerosols were released into the open 4.7 HSK safety evaluation turbine building via a broken measuring line, subsequently escaping into the environment. report on the power During phase III of the exercise, the situa- increase tion was brought under control from a radio- In summer 1992, the KKL submitted an appli- logical point of view, and the turbine building cation for an increase in the nominal thermal was temporarily sealed. Contamination in fields power to 3600 MW, i.e. by 14.7%. This increase near the KKL was found at levels which did not in power requires a change in the operating necessitate the instigation of any measures licence. As the supervisory authority with regard according to the protection action guide con- to nuclear safety and radiation protection of cept; it did, however, raise questions of infor- nuclear plants, the HSK has checked this mation for the public and whether any particu- application in detail. The safety aspects of the lar course of action should be recommended. requested power increase, in particular the risk The HSK rated the emergency organisation for the surrounding areas, were also assessed. and the handling of the emergency by the per- On the basis of this safety evaluation, the HSK sonnel as good. There is still room for improve- raises no objections to the operation of the ment in the communication and information Leibstadt plant at 3600 MW. The findings and tasks of all those involved. Working groups are consequences of this assessment are given in presently discussing what improvements are the HSK safety evaluation report issued in possible and how they could be implemented. March 1996. In this report the HSK recommends that the licence be conditional upon certain requirements designed to ensure the 4.6 Radioactive wastes present and future safe operation of the plant. During the year under review, the quantity of raw radioactive wastes (see Table A11) was as 4.8 Overall judgement by expected, judging from the experience of previous years. Ion exchange resins were ce- the HSK mented with concentrates according to the HSK The plant condition and operation at KKL can corresponding execution permit. Mixed wastes be rated as good with regard to nuclear safety were taken to the PSI, where the combustible and radiation protection. The frequency of inci- wastes were incinerated and the ash residue dents having an influence on safety decreased cemented. The conditioned waste packages still further. The fuel assembly defect found at were returned to KKL. the end of 1996 shows that efforts should con- The principal type of waste package from tinue in order to ensure lasting fuel assembly KKL consisted of powdered resins, milled bead integrity. resins and concentrates, which were cemented In the area of radiation protection, the val- together. NAGRA has checked and approved ues for individual and collective doses were the suitability of this type of waste package for kept very low, particularly considering the ex- final disposal. Based on this, the HSK issued tent of the work that was carried out. Similarly, the corresponding updated execution permit. the release of radioactive materials in the vi- Previously, laundry slurries had been prepared cinity of the plant was negligible. for volume reduction using a press. In future these raw wastes, which contain organic material, are to be dried and incinerated. Different raw wastes, awaiting later treatment, are stored in an unconditioned form in premises in the controlled zone. These are usually compressible wastes collected for the next campaign, as well as some corundum and glass bead wastes, which are to be treated later in the incineration and melting plant of the interim storage facility (ZWILAG). Conditioned waste packages, especially the cemented resins and concentrates, were routinely brought and held in the interim storage facility.

HSK Annual report 1996 • Leibstadt Nuclear Power Plant 41 Die Baustelle fur das Zentrale Zwischenlager fur radioaktive Abfalle in Wurenlingen (ZWILAG) Le chantier de construction de I'entrepot central de dechets radioactifs a Wurenlingen (ZWILAG) The construction site for the central interim storage for radioactive wastes in Wurenlingen (ZWILAG) 5. Central Interim Storage, Wurenlingen

5.1 Review and assessment 5.3 Supervision of

The HSK safety evaluation report on the cen- construction tral interim storage (ZZL) at Wurenlingen, of In accordance with the licence dated 21 August December 1995, was made available for pub- 1996, the detail plans and the construction work lic inspection from 6 February to 22 April 1996, itself will be subjected to HSK supervision. For together with the statement of the KSA. In the the construction of each separate section of course of the licensing procedure, in view of the plant, ZWILAG is to obtain execution the construction of a high-pressure natural gas permits from the HSK. These will be issued pipeline in the vicinity of the ZZL and PSI, once the documentary evidence and plans ZWILAG submitted a supplementary report on submitted have been examined for complete- the possible effects that a gas explosion would ness and correctness. In 1996, execution per- have on the ZZL facilities and the transfer sta- mits were granted for the construction of the tion. The HSK studied the information pre- ground-floors of various buildings. sented in this report and the conclusions pre- Execution permits from the HSK are also sented by ZWILAG. The documentation required for the installation of any systems and submitted by ZWILAG was judged to provide components relevant to safety. Such installa- sufficient evidence that no scenario can be tion permits will be required at the earliest in envisaged that would be likely to have any un- 1997 and subsequent years. acceptable radioactive outcome. As a result, Moreover, since the start of the ZZL construc- the requirements in the proposed licensing con- tion work, periodic inspections of the construc- dition 13 of the HSK safety evaluation report tion site have been carried out by or on behalf were fulfilled, making the inclusion of any spe- of the HSK. cial condition on that aspect in the licence unnecessary. 5.4 Waste from reprocessing 5.2 Licence and licensing The wastes arising from the reprocessing of spent Swiss fuel assemblies at COGEMA in conditions France or BNFL in the UK must be brought back Based on the review and assessment of the to Switzerland. At that time this waste will be project by the Safety Authorities, on 30 May transferred to the ZZL for interim storage. The 1996, ZWILAG submitted a request for a specifications for waste to be brought back change in the initial application. A construction were examined by the HSK and, subject to vari- licence only (including start-up of non-nuclear ous conditions, accepted. operations) should be granted for the condi- Swiss fuel is routinely processed at tioning facility and also for the incineration and COGEMA in the UP3 plant Production reports melting facilities. ZWILAG is thus no longer from COGEMA show that the amount of waste seeking the simultaneous issue of construction produced is smaller than anticipated from the and operating licences for these sections of the specifications. Vitrified high level waste is ready plant. for return to Switzerland. Although the corre- On 21 August 1996, the Federal Council sponding THORP plant at BNFL has been in granted the licence in accordance with the pro- operation since 1995, no Swiss fuel has yet posals of the modified application and overruled been reprocessed there. the objections raised. The licence was granted To date no reprocessed waste has been re- subject to a series of conditions of which 22 turned to Switzerland. Before the waste can be concern nuclear safety, radiation protection and re-imported, the necessary ZZL storage facili- surveillance by the HSK during construction and ties must be constructed and be in operation. operation of the plant. In parallel with the construction of the ZZL, the nuclear power plant operators are fulfilling the further conditions set out in earlier government rulings concerning the applications for prelimi-

HSK Annual report 1996 • Central Interim Storage. Wurenlingen 45 nary assessment. The emphasis will be on meeting the preliminary conditions for the return of vitrified high level wastes from COGEMA. At the end of 1996 the HSK summarised status and results on all these aspects. The nuclear power plant operators have jointly undertaken the procurement of containers for transport and storage of these vitrified high level wastes.

46 HSK Annual report 1996 • Central Interim Storage. Wurenlingen lllilllilf ,L . w .„,,,*• V Das Bundeszwischenlager fur radioaktive Abfalle beim Paul Scherrer Institut, Wurenlingen L'entrepot federal d'entreposage de dechets radioactifs a I'lnstitut Paul Scherrer, Wurenlingen The federal interim storage for radioactive wastes, at the Paul Scherrer Institute, Wurenlingen 6. Paul Scherrer Institute (PSI)

6.1 The PSI in Villigen and Wurenlingen The collective dose for 1996 was 12.5 man-mSv. The plant operated without any This report deals with both sectors of the Paul problems and without any notifiable events. Scherrer Institute, the East sector (located in the community of Wurenlingen) and the West 6.2.2 SAPHIR sector (located in that of Villigen). Surveillance The SAPHIR research reactor is now shut down by HSK covers six nuclear installations (as des- and in a consolidated state. Nuclear fuels are ignated by the nuclear law of 1959) in the East being stored in the installation. PSI's plan to sector, and all other installations in both sec- decommission SAPHIR and to use the build- tors, insofar as they are concerned with aspects ing for other purposes continued during the of radiation protection as described in the ra- course of 1996. Some of the spent nuclear fuel diation protection law of 1991. was returned to the land of origin, the USA, The HSK supervision activities in the year and preparations are being made to return the under review were primarily focused on the ac- remainder. A new control centre, set up to re- celerator installations with the spallation neu- place the dismantled control room, now ensures tron source SINQ which completed first func- that surveillance of the shutdown plant is both tionality tests in December 1996. Supervision safe and economical. In 1996, a range of valu- also covered the PROTEUS reactor, the hot able components (external primary cooling cir- laboratory, the decommissioned DIORIT re- cuit, neutron flux instrumentation, control rod search reactor, the SAPHIR research reactor drives, reactor control and protection systems) (no longer in operation), radioactive waste was transferred to the reactor research centre management and the federal interim storage in Otwock-Swierk, Poland. facility (BZL). In the facility for medical radia- It is now clear that this nuclear installation tion applications, surveillance is carried out SAPHIR will remain in use for several years as jointly with the BAG. According to the radiation a storage facility for unirradiated nuclear fuels. protection law, the HSK is the supervisory board Despite a reduction in the workforce, sufficient for radiopharmacy devices. staff must be available to ensure the proper surveillance of the consolidated plant and of the nuclear fuel stored there. 6.2. Research reactors The 1996 collective dose for this installation was 3.6 man-mSv. During the period under re- 6.2.1 PROTEUS view no notifiable events occurred in SAPHIR. In 1996 the research work on HTR pebble fuel (high temperature reactor fuel) was completed 6.2.3 DIORIT in the PROTEUS research reactor. Further- During the year under review the active sur- more, several experimenters from other disci- face treatment laboratory in the DIORIT build- plines used the reactor as a neutron source for ing was completed, an aluminium melting fur- neutron radiography, calibration of neutron nace was installed, and the active dismantling dosimeters, and detector tests. After the shut- area, which forms part of a disposal route for down of SAPHIR in 1993, PROTEUS was in the dismantling phase of the internal reactor 1996 the only reactor neutron source then avail- components, was constructed. The dismantling able at the PSI. In 710 hours of operation, work on the disused reactor was not continued 50 hours were said "with neutron flux", i.e. dur- during 1996. ing which the neutron flux had a value of at The DIORIT building is presently used by 48 9 2 1 least 1-10 cm- -s- . employees from several research groups for In 1996, the PROTEUS plant took part in the offices and experimental areas. The collective IAEA "Remote Monitoring System" project, dose accumulated by the dismantling squad which aims to provide satellite picture trans- (three people) was only 0.6 man-mSv in 1996. mission from nuclear fuel storage facilities for No notifiable incidents occurred during the the purpose of fission material control (non-pro- period under review. liferation) by international organizations.

HSK Annual report 1996 • Paul Scherrer Institute (PSI) 49 6.3 Accelerator, proton The research activities of the Positron Emis- sion Tomography Programme (PET) at PSI beam channels and ex- focused on neurological sciences and neuro- perimental areas oncology. As in previous years, the radioisotopes F-18, C-11, 0-15, Fe-52, 1-124 and The PSI accelerator was in safe and stable Br-76 were used as tracers in both human and operation, running at 86% availability. Both the animal subjects. spallation neutron source and the medical ap- During the year under review, 236 persons plications require a continuous, uninterrupted suffering from eye melanoma underwent radio- proton beam. The operating staff succeeded therapy in the OPTIS installation. The new in their attempt to minimize beam interruptions. 200 MeV proton therapy installation for proton Injector I (variable energy) operated without treatment of deep tumors was successfully put faults for about 5270 hours for experiments into pilot operation. In addition to treating sev- (nuclear spectroscopy, radiochemistry, mate- eral animal patients, the first human irradiation rial research) and was also satisfactorily inte- was undertaken. As planned, 1996 saw a fur- grated into accelerator operations. Injector II ther reduction in the quantities of radioisotopes (72 MeV) was in operation for 5630 hours. The produced at the Laboratory for Radiopharmacy 600-MeV ring cyclotron operated for 5470 hours (LRP). During the period under review produc- during the year under review and midyear tion involved chiefly radioisotopes for PSI's in- reached weekly proton beam current averages ternal research and on-line applications (PET). of 1.4 mA. In view of the high beam current, The exception was the production of fluoro beam losses responsible for scattered radia- desoxyglycose. tion and activation were kept within reasonable The collective dose for employees in limits. radiopharmacological production and the medi- Operation of the accelerator installations with cal application, 95 persons, was 34.3 man-mSv the associated experiments, as always involv- in 1996. During the year one notifiable incident ing very many internal and external research occurred in the LRP (see section 6.7.1). groups, ran without incidents. At the PSI accelerator installation (excluding radiopharmacy and medical applications), 6.4 Hot Laboratory the collective dose for 185 PSI employees was 74.0 man-mSv in 1996, however, some of these The hot laboratory is now the largest nuclear people were also occupied in other fields of installation at the PSI Since the start-up in the radiology work in the Institute in addition to their early sixties, it has been used equally for basic work on the accelerator. The collective dose research and for applied research in the field for the approximately 300 national and foreign of material technology. This PSI installation is experimenters during the same period was equipped to handle all common types and quan- 66.1 man-mSv. tities of radioactive materials (nuclear fuels and activated materials). A range of modern, largely 6.3.1 Spallation Neutron Source remote-controlled, analytical instruments is (SINQ) available, and further equipment was added Additional construction work on the installation during the year under review. in the halls built some years ago was completed During 1995 and 1996 the safety report, dat- during the year under review. For test purposes ing from the time the laboratory originally went the SINQ was put into operation for the first into service, was completely revised and time for two days in December 1996. The col- passed to the HSK for assessment. As a re- lective dose for the 14 employees at the instal- sult, steps were immediately implemented to lation, in 1996, was 2.1 man-mSv. improve fire protection, and modern contamination monitoring instruments were introduced. 6.3.2 Installations for medical appli- While the reprocessing of waste containing liq- cations (PET, OPTIS, proton uid plutonium, required by the supervisory au- therapy) and radiopharmacy thorities, could not be concluded as planned, (LRP) significant progress has been made (see also The Federal Office for Public Health (BAG) and section 6.5.1). Considerable quantities of al- HSK co-ordinate their surveillance activities for pha-contaminated laboratory waste were also the medical radiation applications at PSI. The treated and fully documented; this led to a BAG deals solely with activities involving irra- marked improvement in the situation at the diation of persons, while HSK is responsible internal radioactive waste interim storage for the other aspects of radiation protection, facility. During operation of the hot laboratory, especially for operational radiation protection. the supervisory authority was notified of one

50 HSK Annual report 1996 • Paul Scherrer Institute (PSI) event according to HSK Guideline R-25 (see for final storage. Although the manufacture of section 6.7.3). The collective dose for the 68 these small packages went according to sched- hot laboratory employees subjected to ule and speedily, the treatment of the backlog dosimetric control was 93.5 man-mSv; the of previously accumulated wastes could not be highest individual dose was 8.3 mSv. completed as planned during 1996. However, it was possible to condition all older wastes fully. Processing of the remaining, properly packaged 6.5 Treatment of radio- and accurately declared, plutonium-containing wastes from the hot laboratory should be com- active wastes pleted by September 1997. The PSI has a wide variety of waste types to treat. These include wastes from federal and 6.5.2 Incineration plant and waste cantonal research installations, from medicine laboratory and industry, and also some from Swiss nu- In the incineration plant attached to the waste clear power plants. Great efforts were made to laboratory, a total of 54 tonnes of radioactive characterize these very diverse wastes accord- wastes from Swiss nuclear plants and the PSI ing to type and to determine the total nuclide were incinerated in the 136 days of operation composition. Extensive activation calculations of the two incineration campaigns, no 34 and were carried out and probes of raw wastes were no. 35. However, at this time the medical, in- analysed using very thorough techniques. dustrial and research wastes from the BAG In 1996, PSI drew up the necessary specifi- collection campaign were excluded from incin- cations, in line with current guidelines, for eight eration. The waste residues (ash) and the ce- types of waste, mainly from the hot laboratory. ramic filter cartridges produced during flue gas For five of these waste types, NAGRA has cleaning were conditioned with cement mor- issued a certificate of suitability for final reposi- tar into 28 waste packages of a specified type. tory in accordance with its regulations for the It was possible to reduce the collective dose acceptance of radioactive wastes; by the end for employees working in the incineration plants of 1996 HSK granted production execution by 50% following the installation of additional permits for four waste types. shields and extensive repairs to the ceramic On 8 July 1996, the new Ordinance for cladding of the incinerator. In addition, by ap- mandatory collectable radioactive wastes pointing new, qualified staff members, the level (SR 814.557), based on the radiation protec- of training of operating personnel could be tion law of 22 June 1994, came into force. As a raised, so that the number of interventions aris- result of this, a training course was held for rep- ing from faulty operations and the time spent resentatives from all installations in the BAG/ in servicing were reduced. The number of calls SUVA area, with particular emphasis on the PSI on standby staff was also reduced proportion- regulations for declaration of wastes. It is hoped ately. that with these measures future incidents can The PSI waste laboratory treats radioactive be largely avoided, due, for example, to incor- wastes falling into the responsibility of the Con- rect or inaccurate declaration. The mandatory federation and produced in the whole of Swit- collection of medical, industrial and research zerland. A key focus in 1996 was on compact- wastes took place at the end of 1996 in the ing solid wastes containing plutonium from the usual annual nationwide campaign. hot laboratory. The compacted wastes were In 1996, the collective dose during opera- conditioned into 31 waste containers specified tion of the PSI disposal installations was for this type of waste. 41.1 man-mSv. The highest individual dose was 9.3 mSv. During the period under review one 6.5.3 PSI West Sector incident according to HSK Guideline R-25 The investigations needed for the characteri- occurred in the plants and installations of the sation of activated raw wastes from the opera- radioactive disposal installations (see section tion of the accelerator advanced sufficiently to 6.7.4). allow calculation of the nuclide inventory. This inventory was accepted, in principle, by NAGRA 6.5.1 Solidification of liquid radio- for the beam dump1 which was removed from active wastes its original installation site in 1990. During the Priority was given to the disposal of wastes conditioning of the 60-tonne waste package containing plutonium. By the end of 1996,1750 planned for early 1997, core samples are to be one-litre packages had been produced and taken and a nuclide examination carried out. quality tested in the hot laboratory (see also section 6.4) using the FIXBOX method. In this about 100 g of plutonium was conditioned ready ' Beam collector for the proton beam

HSK Annual report 1996 • Paul Schemer Institute (PSIj 51 6.5.4 Materials clearance 6.7 Particular events Again considerable quantities of no longer required inactive and/or uncontaminated materi- During the year under review there were four als accrued in zones controlled by PSI. During class B notifiable events according to HSK the year under review, HSK released about Guideline R-25 at PSI, these are listed in Table 57 tonnes of used materials, found to be inac- A3 in Appendix A. tive, from the supervised area for unconditional further use. Among these was an old experi- 6.7.1 Contamination at the LRP (PSI mental magnet with a mass of 36 tonnes, made West) primarily from iron and steel. In March 1996, in a workroom of the LRP, PSI- West, there was a contamination incident with iodine isotope 123. This occurred because the 6.6 Storage of radioactive person concerned disregarded several points wastes in the operating regulations. 6.6.1 Federal Interim Storage 6.7.2 Contaminated measuring de- The Federal interim storage (BZL) has been in vice outside of controlled regular use for temporary storage since the end zones (PSI East) of 1992, and is now about one third full. At the Several years ago, an internally contaminated end of 1996 the BZL stored 3366 treated stand- portable analytical device was brought from a ard containers (200 litres) and 24 containers controlled zone in PSI-East into an inactive (4.5 cubic metres each) holding untreated solid laboratory without sufficient attention being paid wastes from PSI West. During the course of to the relevant safety measures. Its slight in- the year under review, transport containers ternal contamination remained undiscovered holding spent fuel elements from the SAPHIR for a lengthy period and also caused no prob- research reactor were held in temporary stor- lem. When, in late autumn 1995, a repair be- age. came necessary, the device left the Institute's premises bearing no special markings, via CH 6.6.2 Further storage facilities at 5304 Cham to D-72218 Wildberg-Sulz, where PSI (East) a component (monitoring cell) was removed. It Storage halls A, B and C, the stockyard and was not until the device reached the manufac- the transfer point are used for short and me- turer (ANATEL) in Colorado, USA, that the re- dium term storage of low and medium level moved measuring cell was discovered to be wastes either treated or untreated. The inven- contaminated with approx. 200 kBq Co-60 and tory in these storage areas fluctuates greatly. PSI was informed. The work places where the The raw wastes from Swiss nuclear plants, device had been opened were immediately intended for incineration, are delivered as part- decontaminated. shipments and remain at the transfer point for only a short time. The untreated radioactive 6.7.3 Personnel contamination (PSI medical, industrial and research wastes col- East) lected during the 1996 campaign and the re- Careless opening of an insufficiently labelled maining stocks from earlier BAG collection can during tidying-up work in the hot labora- campaigns are kept in storage halls A and B tory involved four employees in a contamina- until they are treated. At the end of 1996 there tion incident in which one person absorbed were 155 waste containers of various sizes in americium 241 with a committed effective dose storage there. At the end of the year, 216 waste of 2.8 mSv. containers (200 litre each) conditioned with cement mortar, some shielded, were stored in 6.7.4 Uncontrolled release of tritium storage hall C and in the stockyard. Spent fuel (PSI East) assemblies from the DIORIT research reactor In autumn 1996, during an insufficiently pre- are temporarily stored in storage hall B in a pared repackaging campaign in the waste labo- CASTOR type storage container. ratory at PSI-East, involving previously treated tritium and americium wastes from non-nuclear 6.6.3 PSI stockyard (West) industrial production, an uncontrolled release The temporary stockyard in the West sector, in of tritium into the environment occurred. The which accelerator wastes in concrete contain- total release of radioactivity, however, lay well ers are being stored for a limited period of five below the short term release limit for the PSI. years, went into operation. In the year under The work was immediately suspended. Aslight review, 14 concrete containers with untreated absorption of tritium was measured in four wastes were stored here.

52 HSK Annual report 1996 • Paul Scherrer Institute (PSI) employees who were carrying out the The outline of a new organization unit repackaging work. charged with radioactive waste disposal and its practical implementation took shape during 1996. This development fulfils a repeatedly ex- 6.8 Additional themes pressed requirement of HSK and it is expected that this unit will become fully functional during 6.8.1 Radiation protection 1997. In the whole of the PSI in the year under review, a radiation dose of 430 man-mSv (1995: 6.8.3 Emergency exercises 540 man-mSv) was accumulated: The PSI emergency exercise, "GERHARD", 250 man-mSv at PSI-West and 180 man-mSv postulated a fire involving solvents in the area at PSI-East. The highest individual dose was of the hot laboratory annexe and the hot labo- 9.3 mSv (1995: 11.1 mSv). As in the previous ratory sector. It assumed that several persons year, no new work with any significant effect had been injured and contaminated, one em- on dose rate was undertaken and the produc- ployee sustaining such serious injuries that tion of isotopes was further reduced. hospitalisation would be necessary. This was The radiation hygiene department person- done by helicopter in order to practice the nel had a collective dose of 22 man-mSv in logistic aspects. 1996(1995: 21 man-mSv). Further information This very demanding exercise proved the about dose values can be found in sections 6.2 preparedness of the PSI emergency organisa- to 6.5 and 6.7 and inTablesA4toA10and Fig- tion to respond to alarms and to adopt proper ure A6. procedures. Steps towards further improving In connection with the protection of the pub- emergency preparedness were taken by PSI, lic and the environment, the release limits for primarily through more targeted training of the all nuclides and nuclide groups were not ex- emergency personnel. ceeded at any release point of the PSI. Assum- ing a worst-case, a dose relative to the most exposed persons in the vicinity of approx. 6.9 Overall judgement by 0.002 mSv per year for aerosols from the incineration plant and 0.004 mSv per year for inert the HSK gases from the central exhaust air of PSI-West The condition of the PSI installations during the is expected. year under review can be considered good. In The quality management system introduced the evaluation of the operation of installations in the radiation hygiene department of the PSI supervised by the HSK there were four notifi- during the period under review formed the able Class B events according to HSK Guide- organizational basis, according to the stand- line R-25. In the opinion of HSK the above ard ISO 9000, for the successful accreditation, events were caused almost exclusively by pronounced by the Swiss Federal Office of Me- human errors or shortcomings. The nuclear trology, of the services for dosimetry, radio- installations still operated at the PSI, and the analysis, calibration and operational radiation other devices subject to radiation protection leg- protection in conformity with the standards islation, demand a high standard of safety EN 45001 and EN 45004 of the European Un- awareness from supervisors and operating staff ion (Euronorms also valid in Switzerland as in order to avoid accidents and incidents. Pre- Swiss standards). cisely at a time when, due to the start of major, new projects and increasing staff and material 6.8.2 Personnel and organisation shortages, expenditure for safety is being criti- The planned shutdown of SAPHIR again led to cally examined, senior management is called a reduction in the number of licenced person- upon to give more thought to safety concepts. nel in this installation during the period under In discussions with PSI and during inspections, review. At the end of 1996 there were two re- HSK was satisfied that proper attention was actor chiefs and two shift chiefs. According to being given to the safety of employees and of HSK, this continues to represent the lower per- the environment. missible limit for proper surveillance of the installation and fuel stores. The number of licenced personnel on PROTEUS has also been reduced and consisted at the end of 1996 of two reactor physicists and two reactor technicians. Two persons attended the training course and passed the examinations for radiation protection chief controllers. !®f t BLA3IK

HSK Annual report 1996 • Paul Scherrer Institute (PSI) 53 7. Other Nuclear Installations

7.1 Ecole Polytechnique 7.3 Experimental reactor at Federate de Lausanne Lucens (VAKL) (EPFL) Since the formal decision by the Federal Coun- The research reactor, CROCUS, was in opera- cil on 12 April 1995, most of the underground tion for 558 hours during 1996 for practical train- and above ground installations of the Lucens ing (reactor physics) for students of the EPFL experimental reactor are no longer subject to and of the engineering schools of Geneva (EIG) nuclear law. The site is now owned by the Can- and Fribourg (EIF). The PSI reactor school used ton of Vaud. A small area of the site, on which the installation for the subject of reactor kinetics. steel containers with radioactive wastes from During the period under review, 116.44 Wh of the damaged, subsequently shutdown and dis- thermal energy were produced. mantled reactor are stored, is still classified as Concerning the other nuclear installations at a nuclear installation. These containers there- the "Institutde Genie Atomique", CARROUSEL, fore remain under the surveillance of the HSK. essentially an arrangement with a neutron The waste containers are to remain on the source surrounded by a moderator, is used for Lucens site until they are transferred to the the preparation of practical work on reactor phys- central interim storage facility (ZZL of the ics by students. The LOTUS plant, a subcritical ZWILAG), now being built in Wurenlingen. 14 MeV neutron source powered by an accel- The Federal Council in its ruling of 1995, re- erator, was not operated in 1996, since repairs solved that radiological surveillance by the ra- had to be made to the cooling system. dioactivity surveillance section (SUeR) of the Operation of all installations and of the type Federal Office of Health (BAG) must continue B laboratory ran without problems. The collec- for thirty years. The SUeR is responsible for tive dose for the 11 persons working on the radiological surveillance of the whole of Swit- nuclear installations at the Institute was zerland, with the exception of the nuclear in- 0.5 man-mSv in 1996. Releases, including tri- stallations. tium, via the atmosphere and via water drain- The one remaining member of the surveil- age, were again insignificant in 1996. lance group, still registered as being occupationally exposed to radiation, accumulated a dose of 1.01 mSv during inspection tours. 7.2 University of Basle

In 1996, the small swimming pool reactor of type AGN-211-P in the basement of the physics fac- ulty at the University of Basle was used, as intended, for teaching purposes, i.e. radiochemistry and radiophysics practicals. In Switzerland there are currently only two small training plants (this one and CROCUS). For this reason both the reactor school at PSI (see also 12.2) and the HTL technical college in Brugg-Windisch use the Basle facility for most of their reactor practical work. The reactor was in operation for this purpose for 63.5 hours (1kW standard hours). This meant that only about 18% of the author- ized weekly limit of 30 kWh was used. The collective dose for the reactor staff of five people was 0.7 man-mSv in 1996. Operation of the Basle nuclear installation was trouble-free and there were no notifiable incidents according to HSK Guideline R-25.

HSK Annual report 1996 • Further Nuclear Installations 55 Seismische Messungen der Nagra im Mettauertal im Hinblick auf die Endlagerung hochradioaktiver Abfalle Mesures sismiques dans le Vallon de Mettau pour ie compte de la Cedra en relation avec le stockage final des dechets hautement radioactifs Seismic measurements by Nagra in the Mettau Valley with a view to final disposal of high-level wastes 8. Disposal of Radioactive Wastes

8.1 Wellenberg repository in the region of Mettau in North Aargau. Initially a seismic campaign is to be carried out, fol- In February 1996, the Wellenberg co-operative lowed by the drilling of vertical and inclined for nuclear disposal (GNW) submitted an ad- boreholes at one or more sites. ditional report in which the statements made in At the end of 1996, in accordance with the the application for a general license for the re- agreement reached, NAGRA carried out pository for low and intermediate level wastes reflexion-seismic measurements in the area (LLW & ILW) in Wellenberg were checked in around Mettau. One or more sites for deep the light of the results of the latest site investi- boreholes should be selected from the results gations. The HSK has taken these results into of these measurements. The government of the consideration in its assessment of the project. canton of Aargau has appointed a commission Based on current knowledge, the HSK is of the in charge to follow these explorations, in which opinion that a LLW & ILW repository, which pro- HSK is participating. vides protection of human health and the envi- Long-term observation continues in ronment, can be constructed at Wellenberg. NAGRA's existing deep boreholes in the crys- The HSK has no objections to the granting of talline basement of North Switzerland. In August the requested general license. It recommends the annual joint meeting of the relevant super- subjecting the license to three conditions which visory commissions was held. The main item would oblige the applicant to proceed to addi- on the agenda was the forthcoming backfilling tional site and safety investigations in view of of deep boreholes. The HSK has set the future licensing steps. The HSK safety evalua- requirements for such backfillings in Decem- tion report was made public on 11 July 1996 ber 1996. Based on these, NAGRA will plan together with the corresponding statement of the backfilling of three deep boreholes which the KSA. are no longer needed (in Riniken, Schafisheim The final evaluation of the site investigations and Siblingen). to date (phase 1) is underway at NAGRA. At A co-ordinating commission on the lines of the beginning of 1997, it should be possible to the earlier supervisory commission was formed produce a geological synthesis report. Parallel for the deep drilling in Benken which was to this, the exploration strategy for the under- licensed by the Federal government in May ground investigations is being refined. During 1996. The first meeting of this commission took the period under review, one meeting of the place in December. The commission studied supervisory commission on the investigations information about the seismic measurements at Wellenberg, consisting of representatives of planned for spring 1997 and about measures the Confederation, the canton and the local for the surveillance of the groundwater. HSK had community, was held. reviewed the programmme of work for the deep drilling and granted the execution permit in August. 8.2 Disposal of high-level Accompanying investigations and experiments observed by HSK are carried out in rock wastes: preparatory laboratories. In the Grimsel rock laboratory the measures main feature was the start of the FEBEX ex- The working group called "Kristallin periment. In connection with the excavation Nordschweiz" formed in 1995, with members experiment, HSK granted a radiation protec- including experts from NAGRA, KNE and HSK, tion permit for the use of radioactive tracers. In submitted its final report in June. The task of June the new Mont Terri rock laboratory near this working group was to work out an agree- St. Ursanne was opened. The ceremony was ment on a concept for further exploration of attended by many representatives of partners crystalline rock with a view to final disposal of from abroad. Since the beginning of 1996, an high-level wastes. It was considered sensible extensive test programme in the host rock to continue parallel programs in the crystalline opalinus clay has been prepared and is now rock and in the opalinus clay. The group fa- underway. voured exploration of the crystalline basement

HSK Annual report 1996 • Disposal of Radioactive Wastes 9. Transport of Radioactive Materials

9.1 Approvals according to 9.3 Audits and inspections transport legislation To ensure the safety of transport workers and The Swiss regulations governing the transport of the general public, any shipment of radioac- of radioactive materials are based on interna- tive materials must comply with the relevant tional legislation on the transport of hazardous regulations. Quality assurance programs are materials. The IAEA recommendations (SS6)1 intended to ensure compliance with regulations. for the safe transport of radioactive materials Quality assurance covers the design plans and apply for all modes of transport. the procedures, aimed at achieving compli- The main responsibility for complying with ance, adopted by packaging constructors and the transport regulations and for radiological manufacturers, consignors, carriers and the safety lies with the consignor. In the case of competent authorities. the transport of nuclear fuel or other highly The statutory requested transport quality as- radioactive materials, regulations demand that surance programs of the Swiss nuclear instal- the consignor obtain in advance the approval lations came into force in 1994. Since then, from the competent authority. Depending on the quality assurance programs for the transport individual circumstances, the approvals cover of radioactive materials have been approved the consignments and/or the shipments. HSK by the HSK for all larger Swiss nuclear installa- is the Swiss competent authority in charge of tions (KKB, KKL, KKM, KKG, PSI). In order to issuing such approvals, irrespective of whether maintain this approval, periodic audits are they concern the transport of radioactive planned. In 1996, the first such audit was car- materials from nuclear installations or from ried out at KKG with satisfactory results. other installations. Where consignment approv- In 1996 an inspection lasting several days als are concerned, the HSK usually relies on was carried out on the dispatch of fuel assem- the documents issued by the competent blies from KKG. This showed that the transport authorities of the country of origin. In all cases regulations were being complied with. the HSK first verifies that packaging and contents comply with regulations. In 1996 the HSK assessed 48 applications 9.4 Training and information concerning shipments or consignments. In October 1996, the sixth course was held for plant employees responsible for the dispatch 9.2 Authorisations accord- of radioactive materials. The five-day course is usually offered annually both in French (In- ing to radiation protec- stitute of Applied Radiophysics, Lausanne) and tion legislation in German (PSI School of Radiation Protection). The HSK collaborates by delegating some of According to Article 2 of the radiation protec- its staff members as instructors for these tion law of 22 March 1991, the transportation courses. of radioactive materials is an activity subject to authorisation. The conditions for granting such an authorisation are laid down in the radiation protection ordinance of 22 June 1994. In 1996, on the basis of an application and fulfilment of the conditions, the Beznau nuclear power plant was granted an authorisation for the transportation of radioactive materials.

IAEA Safety Series 6: Regulations for the safe transport S31XT g»A6E(S) of radioactive material, 1985 Edition (as amended 1990) left BLANK

HSK Annual report 1996 • Transport of Radioactive Materials 61 Messsonde MADUK vor dem Kernkraftwerk Leibstadt Sonde de mesure du reseau MADUK devant la centrale nucleaire de Leibstadt MADUK measurement probe at the NPP Leibstadt 10. Emergency Preparedness

In accordance with the ordinance on the or- 10.2 Training activities in ganisation for intervention in the event of in- the area of emergency creased radioactivity (VEOR of 26 June 1991), the HSK has responsibilities in the area of protection emergency protection. The HSK has to inform the National Emergency Operation Centre In 1996, in the area of emergency protection, (NAZ) promptly of any events in Swiss nuclear the HSK held a total of 23 external training installations which could present a radiation risk courses on its own and/or contributed to to the environment. The HSK has to issue fore- courses organised by other authorities. The casts on how the event at the installation is likely courses were divided as follows: 11 courses at to develop, how any radioactivity released could federal level and 6 each at cantonal and com- spread in the surrounding areas, and what the munity level. The topics covered by the courses consequences would be; it has to assess the included the principles of radiation protection, suitability of any measures adopted by the nu- how nuclear power plants function, accident clear installation operators for the protection of scenarios, and emergency planning for the re- personnel and the environment; it has to ad- gions around nuclear power plants. vise the NAZ on proposals for protection measures for the public. In order to be able to perform these tasks, the HSK operates a picket 10.3 WINDBANK, ADPIC service and runs its own emergency organisation. 10.3.1 Determination of the lower Aare Valley wind fields using WINDBANK 10.1 HSK emergency organi- The WINDBANK project (Lower Aare Valley Wind Field Databank) aims to record the re- sation gional wind field situation in Zones 1 and 2 of The work of the emergency organisation, par- KKB (Beznau Nuclear Power Plant), KKL ticularly the emergency staff, and the suitabil- (Leibstadt Nuclear Power Plant), and PSI (Paul ity of the means and equipment available in Scherrer Institute). the emergency room were checked by exter- The values measured in the terrain during nal experts. In this connection, further train- the previous year were subjected, in the year ing in the staff work was undertaken. Improve- under review, to a wind field classification. A ments in the infrastructure in the emergency comparison of the data built up pictures of simi- room were made. lar situations and, by normalising the wind In accordance with the Guideline HSK-R-15, speeds, 13 clearly defined, different and char- the plant operators notified the HSK picket serv- acteristic flow situations could be shown. All the ice of events 17 times in 1996. data, with only unimportant or insignificant to In the combined emergency exercise slight wind direction deviations, were classifi- 'FORTUNA" held on 7 November 1996 (see able. This has produced a wind field database section 4.5), the HSK emergency organisation for the lower Aare valley, which can be used to was in operation for the entire period of the calculate the spread of radioactivity in the exercise (with 2-shift relief). The effectiveness vicinity of nuclear plants. In autumn 1997, it is of the training that had been carried out was planned to measure and record the wind fields evident in the staff work and in the handling of in the vicinity of KKM. communications and information. For all calls on the HSK emergency organi- 10.3.2 Computer program ADPIC sation through its picket service, by the plants The complex dispersion model, ADPIC (Atmos- for each notified event and also in the pheric Diffusion Particle-ln-Cell Model) devel- "FORTUNA" emergency exercise, the required oped in America, described in the HSK 1995 groups were always fully mobilised as pre- Annual Report, has been further adapted to scribed within less than one hour after being meet Swiss conditions. A major task lies in the summoned. on-line recording, automatic transfer and use

HSK Annual report 1996 • Emergency Preparedness 65 of current meteorological data and the use of the wind field measurements from the WINDBANK project. ADPIC should be in operation for the KKB and KKL locations by the end of 1997.

10.4 MADUK, ANPA 10.4.1 Measuring network for automatic dose rate surveillance in NPP vicinity (MADUK) Since the beginning of 1996, the daily average dose rates measured by four of the several MADUK probes operating on each nuclear power plant site have been broadcast on Tele- text on the national television for German, French and Italian speaking areas of Switzer- land. The information is also published in monthly bulletins of results, issued directly to cantonal and local authorities and also to pro- prietors of the probe sites. In summary, it can be seen that the MADUK system is a valuable tool for the monitoring and assessment of radioactivity in the vicinity of nuclear power plants.

10.4.2 System for plant parameter transmission (ANPA) At the request of the HSK, a system (ANPA) for the transmission of parameters to HSK headquarter from each of the five Swiss nuclear power plants can be connected up. Using ANPA, the HSK can receive and then display up to 25 key plant parameters, updated every 2 minutes, especially in the case of an accident at a plant. In the event of mobilisation, the emergency staff has the means available to be kept rapidly informed about the nature and progress of the accident. The ADAM system now being developed (Accident Diagnostics, Analysis and Manage- ment) will provide the HSK emergency organisation with support in the interpretation of the ANPA data and give indications on how the accident is developing and its consequences. ADAM uses simplified plant-specific models and can determine the current plant status using the ANPA data. The system calculates the course of an accident 100 times faster than a real-life accident would be expected to progress. At present, one model is available for the Leibstadt plant.

1 PAGt(S) left SLANtC 66 HSK Annual report 1996 • Emergency Preparedness Ultraschallaufnahme einer durch den asymmetrischen Schweissvorgang bedingten, normalen Verformung eines Steuerstab-Durchfuhrungsrohrs Image ultrason d'une deformation normale, causee par la soudure asymetrique, d'un manchon de traversee d'une barre de commande Ultrasound test pattern of normal deformation, caused by asymmetric welding, in a control rod guide tube 11. Selected Aspects of Nuclear Safety and Radiation Protection

11.1 Guidelines authorities will apply in evaluating an application and in performing their surveillance tasks. The Swiss guidelines and recommendations, Design guidelines, such as HSK-R-101, ap- valid at the end of the year under review, are ply in principle to the construction of new nu- given in Table B1 of this report. These were clear power plants with light water reactors. drawn up by the HSK, in some cases in col- Such guidelines are also applied in the evalua- laboration with the KSA and other Federal Of- tion of existing plants in order to identify devia- fices. In 1996 the following guidelines were re- tions. Compliance with the guidelines makes it vised and came into force: easier to verify the safety status, while any de- •HSK-R-15d: Berichterstattung Gber den partures from the guidelines have to be evalu- Betrieb von Kernkraftwerken ated on a case by case basis. (Reporting on the operation of nuclear power plants) • HSK-R-35d: Aufsichtsverfahren bei Bau und 11.2 Instructive events in Anderungen von Kemkraftwer- foreign nuclear ken, Systemtechnik (Surveillance procedures for installations construction and modification work on nuclear power plants, Of the events reported in 1996 in foreign plants, systems engineering) there were no incidences of such significance In 1996 the following two guidelines were still as to require the immediate implementation of in preparation; they should come into force in measures to improve the safety provisions in 1997: Swiss plants. Nevertheless, some events are • HSK-R-41d: Berechnung der Strahlenexpo- described below because they are instructive sition in der Umgebung von and the lessons learned from them may con- Kemanlagen aufgrund von tribute to improving the safety of Swiss plants. Emissionen radioaktiver Stoffe aus solchen Anlagen 11.2.1 Severe impairment of the (Calculation of radiation expo- decay heat removal system in sure in the vicinity of nuclear a pressurised water reactor plants, based on the emission during shutdown of the plant of radioactive materials from The event regarding the impairment of the de- such plants). cay heat removal system has already been • HSK-R-45d: Planung und Durchfuhrung von described in the report for last year (descrip- Notfallubungen in schweizeri- tion, see Annual Report 1995, page 77). A post- schen Kernkraftwerken (Ersetzt script can be added here: the analyses carried die Empfehlung E-03) out since then have shown that an error during (Planning and carrying out plant shutdown could impair not only the decay emergency exercises in Swiss heat removal system but also the function of nuclear power plants (replaces the containment. As this applies to all types of recommendation E-03). plants, the HSK has informed all the Swiss The HSK guidelines demonstrate how the plants of these circumstances and has asked safety authorities wishe to implement their for their comments. statutory responsibilities in the areas specified. They are intended to create legal security in that they indicate which criteria the competent

HSK Annual report 1996 • Selected Aspects of Nuclear Safety and Radiation Protection 69 11.2.2 Severe impairment of the investigated. The cause lies in connection with cooling capacity through ice deformation of the guide tubes. The problem formation in the cooling wa- occurred in the reactors of two different manu- ter inlet facturers. No event of this type has ever oc- In a foreign plant which takes its cooling water curred in Swiss plants. Nevertheless, special from a lake, very unfavourable weather condi- tests have been carried out in the plants. Swit- tions (strong wind and low temperatures, lake zerland is actively participating in the close in- surface not frozen) resulted in the very rare ternational co-operation working to solve the formation of granular ice, called frazil. This ice problem. does not remain on the surface of the lake but hangs in suspension so that the inlet filter (sev- 11.2.4 Missing plug in a neutron eral metres below the surface) of the cooling measuring channel water extraction pipe became partially blocked. After maintenance work on the neutron flux When the blockage was noticed, the plant was detectors, the shielding of a measuring chan- immediately shutdown. This type of ice forma- nel was not replaced in accordance with the tion was known to the operator and a heat re- regulations. As a result, during reactor opera- taining installation had been provided. However, tion, radiation of high intensity but small dimen- it lacked the necessary efficiency. Furthermore, sion (about 5 cm diameter) escaped into an some minor faults were discovered. The oper- accessible area. Two employees received a ating staff proceeded, in accordance with the partial body dose which exceeded the admis- regulations, to call out the support staff and in- sible limit. Despite the monitoring of radiation form the authorities. The situation was quickly and dose, done as prescribed in the regula- remedied with divers initially called in to assist. tions, the fault remained undetected for a con- Even if the cooling water supply had failed com- siderable length of time. Following the incident, pletely, no accident would have occurred, as extensive measures were introduced to im- an independent emergency cooling water prove quality assurance during maintenance source is available which uses fire hydrant work. This is an instructive case, even though water. The lessons to be learned from the event the personnel in Swiss nuclear installations are (uncommon set of weather conditions, insuffi- well aware of the problem of badly positioned cient heating) can be drawn at several levels. or missing shielding. An event of this kind has Swiss plants do not take cooling water from never occurred in Switzerland. What is more, lakes, but from rivers, so they are less likely to a check showed that in most plants, the area be affected by this type of event. However, the in question is not accessible during reactor question of this special type of frazil ice forma- operation. tion in the cooling water inlet is very instructive as a "common cause" (failure of components 11.2.5 Inadmissible fast cool down due to a single common cause). Unlike the plant of the primary side in question, the KKB, KKL and KKG plants have Although a spray valve of the pressurizer was separate ground water supplies which are in- indicated as having reached the closed posi- dependent of the river water inlet. Moreover, tion, it did not significantly reduce the spray flow. the plants are so designed that hydrant water This resulted in a large reduction in pressure could very easily be adapted for use as an in- in the primary circuit of the pressurised water dependent cooling water source. In KKM, there reactor. To prevent steam void formation in the is a fixed installation fed from a high reservoir. core, the operating staff thought it advisable to cool the plant as rapidly as possible. This led 11.2.3 Blockage of some control to an unacceptably high rate of cooling. As rods preventing full insertion Swiss pressurised water reactors have the after a scram in some pressu- same arrangement of spray valves, the HSK rised water reactors of west- requested the operators concerned to make a ern design statement on the event. Investigation has It has been observed in some pressurised wa- shown that present operating instructions are ter reactors that, after scrams, some control sufficient to avoid such an occurrence. rods failed to reach the final insertion position because they had become blocked a little way short of full insertion. The plants are so de- 11.3 Ageing surveillance signed that even without the full effect of the control rods there is sufficient reserve to en- The mechanical and electrical equipment of a sure shutdown. Also, as most of the rods fell nuclear power plant and its buildings have, in into position, enough reserve has always been many cases, a great significance to nuclear maintained. The problem is being extensively safety. A loss of integrity or a functional failure

70 HSK Annual report 1996 • Selected Aspects of Nuclear Safety and Radiation Protection could cause an accident condition, render the The ASP is to produce proof of suitability with control of the plant under such conditions more regard to ageing and safety for all mechanical difficult, or at least submit certain parts of the and electrical equipment and for buildings, for plant to detrimental transient stresses. at least the next operating cycle. However, it The primary aim of the ageing surveillance also demands a long-term forward-looking sur- programme is to maintain the required degree veillance strategy. Complementary to the short- of safety in the NPP at component level. A fur- term objectives, during the remaining lifespan ther aim is to minimize operating problems. of a plant, all ageing effects, or at least those What is more, it is essential to place planning which are ascertainable and predictable, should of the lifetime of the plant on a solid founda- be identified in good time with the help of the tion, particularly in view of the long operating ASP, in order to be able to timely implement times of the plants. any necessary corrective measures. As a rule, the operational and safety proper- For nuclear power plants now in operation, ties of mechanical and electrical equipment the ASP for mechanical and electrical deteriorate progressively throughout service equipments as well as for buildings has two life. This is caused by the operational loads and main steps: initially establishing and organis- stresses and the associated material deterio- ing of the programme (initial tasks), then, as a ration (ageing). The same is true, to some ex- long-lasting obligation, implementing it (perma- tent, for buildings. The deterioration in quality nent tasks). caused by ageing in components or construc- For the initial tasks, the NPP operator has to tional parts is a function of time, but only in the examine and evaluate all information on exist- simplest cases is this linear and therefore pre- ing systems and components, examine and dictable. In other cases the processes are com- evaluate the historical records from the complex and insufficiently understood. ponent manufacture and installation phase, With time and material usage, ageing effects identify and evaluate all possible ageing mecha- can become of significance to nuclear safety. nisms and effects, evaluate all previous sur- For this reason it is essential to have a surveil- veillance and maintenance measures, and then lance programme which is systematic, compre- finally draw conclusions from these on any po- hensive and forward-looking in the long term. tential consequences and appropriate meas- The programme must cover all mechanical and ures required. electrical equipment and buildings which are Under the ASP permanent tasks, the NPP subject to the ageing processes and ageing operator undertakes the long-term surveillance effects. Such a programme plays a key role in and any necessary extension of maintenance ensuring the safety of a nuclear power plant and routine tests. This has to be based on the during its remaining operating lifespan. current state of the technology, the testing Nuclear power plant operators are required methods employed and operating experience. by the HSK to run an ageing surveillance pro- The permanent tasks continue until the NPP is gramme (ASP). It must include all measures decommissioned. necessary to ensure the timely and reliable recognition, rectification, amelioration or correc- tion of ageing in all plant parts where integrity 11.4 Periodic safety review and functionality are essential for the safety of the plant. These measures include the system- A periodic safety review (PSR) is a compre- atic evaluation, by component or system, of hensive safety examination of a nuclear power possible ageing mechanisms, the early identi- plant which takes account of the current state fication of such ageing processes, an evalua- of science and technology. It is made by the tion from a safety viewpoint of all existing age- HSK and is based on the updated safety analy- ing effects, and ultimately an assessment of sis report, the probabilistic safety analysis and the remaining plant life. To do this, it may be other technical reports. An examination of this necessary to check back at the design basis of type was performed for the Muhleberg and components and systems to review them in the Beznau plants in 1991/92 and 1993/94 respec- light of the current state of the technology. It is tively, as part of the review and assessment of also necessary to check the completeness and the applications for an unlimited operating li- effectiveness of the in-service inspection pro- cence, and for the Leibstadt NPP in 1995/96 gramme, periodic inspections and functional- as part of the review and assessment of the ity tests as part of the maintenance activities. If application for a power uprate. any gaps are found during these investigations, The PSR for Gosgen began in mid 1996 and suitable measures are to be adopted to ensure should be completed in 1998. The EVED their closure. granted the startup and operating licence for GOsgen in 1978 based on the various techni-

HSK Annual report 1996 • Selected Aspects of Nuclear Safety and Radiation Protection 71 cal safety evaluation reports by the KSA. Since nificance of such accidents. It also serves to then the safety status of the plant has been identify weak spots in the safety design, and to verified through regular inspections, tests and reveal and evaluate measures for controlling servicing, and also by safety analyses of spe- accidents and mitigating their consequences. cific problems. In-service inspection, fuel When applied throughout, PSA studies can assembly inspections and comprehensive sys- make a valuable contribution to a balanced tem and component tests during shut down for safety evaluation of the plant and its operation. maintenance and refuelling form a central ele- At the request of the HSK, all Swiss nuclear ment for ensuring the safe operation of a plant. power plants are preparing PSA studies for both HSK grants the execution permit for startup full power operation and outage, respectively. after refuelling largely based on the results of The studies for full power operation are already these tests. Moreover, every modification to the available for all plants. The outage studies are plant which affects safety is checked in detail still in preparation in some plants. The HSK has by the HSK. With the scientific and technical already subjected the existing full power advances made in the area of nuclear power operation studies to an independent assess- plant safety, several back-fitting projects (e.g. ment. in connection with measures to prevent or miti- On the basis of the results currently avail- gate severe accidents) have been completed able, the residual risk for all Swiss nuclear over the past years and their effect on safety power plants is very low and the results, by com- has been assessed. parison at the international level, are very good. Probabilistic safety analyses (PSA) have also The good results reflect the constant effort of been carried out in recent years for Gosgen as the operators to run their plants at a high level it has been done for the other Swiss nuclear of safety and to take appropriate measures to power plants. These analyses provide a com- keep the risks as low as possible. The HSK, prehensive evaluation of the course of even for its part, keeps track of and evaluates these hypothetical abnormal events not covered by measures and, on the basis of its own inde- the design basis with regard to risk, and to re- pendent investigations and clarifications, reveal possible weak spots in the plant as well quires, if necessary, additional improvements. as to take appropriate measures for control- In an effort to reduce the uncertainty inher- ling or alleviating such events. In the ageing ent in any safety analysis, the HSK supports surveillance program (ASP, see section 11.3), international research projects which contrib- on the other hand, the emphasis is placed on ute to explaining the technical and scientific component condition. Both the PSA and ASP phenomena. HSK participation in such projects are important cornerstones of a PSR, and are is not limited to financial contributions but in- usually complemented by a systematic and cludes active work on various projects. Two ex- comprehensive analysis of events, operating amples are briefly described below. experience, and maintenance. In modern plants, the high level of redun- The aims and purposes of the PSRs are to dancy of the safety systems has led to an ap- evaluate the individual results collected by plac- parent increasing effect on the core damage ing them in their overall context and so to pro- frequency due to faults in components of the duce a full evaluation of the safety status of same type (common cause failure CCF). This the plant. This also includes checking to see can be explained by the removal of virtually all that the protective aims, rooted in the guide- other sources of potential core damaging fac- lines and other regulations, are being kept both tors. Common cause failures are rare, so the under normal operation and also under acci- numeric failure rate exhibits a wide scatter dent conditions. band. To quantify this more accurately, as much The time required to conduct the PSR is es- information as possible is needed on the reli- timated at about two years. The PSR final re- ability of the same type of components. To cover port will contain the main results and meas- this need, the Swedish nuclear safety authority ures for authorities, operators and the public. (SKi) instigated a multinational exchange of data and founded the International Common Cause Data Exchange Group (ICDE Group) 11.5 Probabilistic safety which is working primarily on the methods and documentation for quantifying CCF. Over the analysis coming years, a database will be built up from Probabilistic safety analyses (PSA studies) are data collected for the project from some 200 concerned with accidents in which several nuclear power plants and will be evaluated for safety systems fail or, for some other reason, CCF incidence. exceed the design limits. This analysis proce- In the EU project "European Benchmark Ex- dure allows a quantitative evaluation of the sig- ercise on Expert Judgement Techniques in

72 HSK Annual report 1996 • Selected Aspects of Nuclear Safety and Radiation Protection Level 2 PSA" (BE-EJT), a comparison is being properly differentiated manner rather than as made of the various expert judgement (EJ) generalities. methods used for evaluating steam explosions At the moment, international efforts are in within and outside the reactor pressure vessel. progress to afford the human factors in nuclear Its suitability for use in probabilistic safety analy- plants a higher significance. An originally tem- sis is being checked. Expert groups from vari- porary study group of the OECD/NEA, which ous countries used some of the newly devel- was looking at the human factor, has now been oped EJ methods in order to predict the results given a permanent mandate. In the year under of a fuel-coolant interaction (FCI) experiment review, this study group was concerned prima- at the FARO test plant (Ispra, Italy). The over- rily with working out an overview on simulator all agreement of the prediction with the empiri- training in the member states and, in addition, cal values can be used to make a comparative with ways of improving the analysis of events assessment of the EJ methods. caused or influenced by the human factor. The results of this work will provide the international Incident Reporting System (IRS) for events in 11.6 Human factor and nuclear power plants with a new enlarged system of classification taking account of the safety culture human factor in such events. In autumn 1996, the SVA organised a seminar The great importance of the human factor on "The Human Factor in Nuclear Power Plant for nuclear safety has also been reflected in Operation". The great interest shown in this the grading of events according to the INES event indicated that the human factor is now (International Nuclear Event Scale). It has been recognized as an important element in nuclear recognized that the prevention of events does safety. While in the aftermath of the Three Mile not depend solely on technical barriers but also Island accident (1979, USA) studies of the hu- on the behaviour of operating personnel. It is man factor were restricted largely to ergonom- assumed, for example, that the failure of per- ics and training, the Chernobyl accident (USSR, sonnel to act in accordance with the procedures 1986) showed that both the individual and also should be regarded as a breach of one of the the supporting organisation can have a signifi- safety barriers and this can justify that an event cant influence on safety. As a result, this has be classified at a higher level. This philosophy been expressed by the creation of the term is presented in the INES user's manual. It is "safety culture" which has been employed in the task of INES to provide rapid information all subsequent studies of this topic. for the media and the general public on any The expression has now become estab- effect that an event may have on safety. This lished, although for some time there was a cer- requires that uniform practices be adopted in tain doubt as to the proper definition and inter- all countries, it is therefore essential that the pretation and this still exists to some extent philosophy be adopted internationally and the today. This was one of the reasons why the INES criteria be applied uniformly. KSA took up the topic. The year under review saw the final phase of the preparation of a KSA paper on the subject of safety culture. The 11.7 Evaluation of events in document called "Reflections on Safety Culture" is designed to clarify the expression and inter- nuclear installations pret it in a Swiss context. The HSK made a 11.7.1 HSK Guidelines contribution to this paper. In accordance with HSK Guidelines R-15 and The application of the term "safety culture" R-25, the operators of Swiss nuclear installa- is not entirely without problems. "Safety" and tions are obliged to notify the HSK of any events "culture" are words with implications of high val- which occur. The purpose of this notification is ues. Too casual a use of the expression, as in threefold: the general, all-embracing remark, "they have - Notification of events to allow early recogni- no safety culture", during the analysis or evalu- tion of weak spots and their rectification. ation of an event can give rise to misunder- - Notification of accident conditions to alert the standing or discouragement in those affected. HSK emergency organisation and other au- This type of generalisation puts a stop to any thorities. dialogue before it has even started. For this - Notification of events of public interest to al- reason, in some circles the expression "safety low the supervisory authority (HSK) to make culture" is re-worded in more neutral terms as an independent assessment and to rapidly "organisational factors" or "risk awareness". give official information to the public. This enables the comments, made during the For practical reasons, to achieve these objec- evaluation of an event, to be expressed in a tives, a classification system was introduced

HSK Annual report 1996 • Selected Aspects of Nuclear Safety and Radiation Protection 73 which takes into account the significance of plant, they could generate public interest. An events with regard to safety. The Guideline R-15 event of this type could be an industrial acci- provides for the following classification of dent where an ambulance has been called. events, with examples, in order of ascending safety significance: 11.7.2 International Nuclear Event Scale, INES Event U (unclassified) Several countries were quick to recognize the These are events which exhibit safety aspects need for a new instrument specially designed of interest to the supervisory authority, but do for communication with the public. As a result, not fulfill the criteria for a class B, A or S. They a scale was developed (similar to the Richter serve chiefly for internal information within the scale for earthquakes) so that the public could HSK and are not mentioned in Table 3 of tech- be properly informed about occurrences (called nical events. Examples of this category: events in the Guideline R-15). Building on this - Large variations in power, water level or flow, experience, the International Atomic Energy without a reactor scram Agency (IAEA), working jointly with member - Failure of a safety system during testing, but states, produced the International Nuclear in such a way that this type of failure would Event Scale (INES). This was introduced in not occur in an actual demand situation 1990 as a pilot scheme and was adopted defi- - Events which indicate the possible presence nitely in 1992. of a common mode fault (the possibility of The scale aims to inform the media and the failure of several components of the same public of events at nuclear plants by putting type). them in the right perspective with regard to safety. The INES User Manual was produced Events of Class B as the yardstick with evaluation principles valid These events only marginally affect safety. They for all countries. The IAEA plays a central co- are registered and evaluated so that any pos- ordinating role in the exchange of event notifi- sible weak spots can be identified in good time. cations. Each member state has undertaken Examples of events falling into this class in- to report all events from level 2 upwards to the clude an automatic reactor shutdown or the IAEA for distribution to the other member states. failure of a safety component during a periodic The IAEA also organizes exchanges of experi- functionality test. ence between member states in order to promote uniformity in the use of the scale. Par- Events of Class A ticularly at the lower end of the scale (0 and 1, These events are significant to safety, but have and sometimes 2), the criteria cannot be speci- no or only very slight radiological consequences fied precisely enough to preclude engineering for the environment. For example, the failure differences in the evaluations. With the large of the internal electricity supply would fall into number of different plant types in the partici- this class, or any case where the lowest radio- pating countries, and the differing safety provi- active release limit would be exceeded (short sions, it is almost impossible, even from a tech- time limit). nical viewpoint, to achieve complete standardisation of disturbances in the normal Events of Class S running mode of the various plants. These events pose a threat to the plant, the Switzerland, as a member of the INES or- plant personnel or the environment. For exam- ganisation, has co-operated on the develop- ple, this class would include a leak in the ment of the INES system from the start and primary system which automatically triggered uses the INES scale. This does not exempt the emergency cooling system, or a major pipe operators from notifying events in accordance leak in the steam system which causes a reac- with the Guideline R-15, but is intended as ad- tor scram, or any release exceeding the annual ditional information for the public. release limit for radioactive materials. The INES scale indicates the significance of events as a number from 0 to 7, where level Many events are of interest to the general 0 is taken to be a "normal deviation", for exam- public and these are designated "0". A and S ple, automatic reactor shutdown without much class events are basically of public interest; in complication (about class B in R-15). the case of B and U events, public interest is In principle, each INES level differs from the aroused by those events with consequences next by a factor of 10 to 100 in safety signifi- which can be observed from outside the plant. cance, i.e. a level 1 event corresponds to V10 There are also events which have no safety to V100 of a level 2 event. Three aspects are classification as they lie below level U, but be- taken into consideration: "Degradation of safety cause they can be observed from outside the measures" (applies from level 1 to level 3),

74 HSK Annual report 1996 • Selected Aspects of Nuclear Safety and Radiation Protection "Consequences within the plant" (level 2 to 5), and "Radiological consequences outside the plant" (level 3 to 7). The individual criteria are given in a simplified form in Table B2. Accidents start at level 4. As the purpose of the INES scale (greater understanding for the media and experts for informing the public) differs from that of the HSK Guideline R-15 (information for the authorities), the INES levels cannot be classified directly as B, A or S. Already only slight departures from the procedures or technical specifications are classed by INES as level 1, even when this involved no increase in risk. Compared with national classification systems, the INES scale has the advantage that it applies internationally recognized criteria and standards. This serves to enhance abroad the understanding of the consequences of events, because the same evaluation criteria are employed. It helps to avoid misunderstandings in reporting events in plants in foreign countries, and places them in their proper safety perspective Nearly all countries comply with the INES reporting system when their authorities notify the IAEA or at least check the report before it is sent. The INES system is able to ensure, worldwide and independently of any operator of an nuclear installation, a policy of public information on events in nuclear installations that is open and clear.

HSK Annual report 1996 • Selected Aspects of Nuclear Safety and Radiation Protection 75 12. Research, Training and International Co-operation

12.1 Safety research active cobalt-58 are interchangeable in the aqueous phase. The Swiss Federal Nuclear Safety Inspector- The findings regarding the deposit of active ate, HSK, must appraise the safety of Swiss cobalt on system surfaces in boiling water re- nuclear plants according to the latest state of actors are of great significance for personnel science and technology and, if necessary, has doses accumulated during operation and dur- to require that measures be adopted to increase ing maintenance. Further experiments are nec- safety. To this end, the HSK supports various essary to model the actual reactions in boiling projects in key areas of regulatory safety re- water reactors. search in the following three fields: - Research projects at the Paul Scherrer In- 12.1.2 Stress corrosion cracking off stitute (PSI) and at universities steels for reactor compo- - Specific projects given to domestic and for- nents in hot water; PSI, eign engineering companies Wurenlingen/Villigen - Participation in international projects The research project aims to examine the long- Some brief comments on the more important term behaviour of reactor components exposed of these projects follow. to pressure loading with regard to stress corrosion cracking under reactor conditions. Dur- 12.1.1 Light water reactor- ing the year under review the focus was on the contamination control; PSI, following activities: Wurenlingen/Villigen - Re-equipping and improving the experimen- The aim of the research is a better understand- tal hot water loops and sample preparation; ing of the mechanisms of the incorporation of introduction of better measuring techniques. cobalt-60 into the oxide layers of light water re- - Implementation of an international compari- actor components. son study planned in 1995 (Round Robin Ex- In line with the research objectives set for periments), and continuation of the basic 1996, various sub-projects were undertaken: measuring programme. - Investigation of the speed of corrosion, the - Establishment of a quality assurance pro- kinetics of the layer build-up, and the struc- gramme for experimental methods and the ture of the oxide layer on the austenitic evaluation of results. chrome nickel steel under simulated reactor - Modelling of stress corrosion crack growth, conditions in a hot water loop. The tests using finite element methods. showed that the oxide layer is thicker at wa- The tests carried out so far permit a conserva- ter speeds typical of laminar flow compared tive evaluation of stress corrosion crack growth to turbulent flow. Moreover, the layer is sig- speeds under simulated boiling water reactor nificantly thicker on mechanically polished conditions. Further tests and theoretical inves- surfaces than on electro-polished surfaces. tigations in the fringe range of normal operat- - Reduction of the active deposits on steel using conditions are necessary for an overall as- ing pre-oxidation. Preliminary tests showed sessment from which the remaining life span that the oxide layers formed via pre-oxida- of cracked reactor components can be esti- tion with hydrogen peroxide effectively hinder mated. The modelling of mechanical param- formation of active deposits under reactor eters in the crack initiation process may be a conditions. The treatment with hydrogen basic condition for understanding and interpret- peroxide has been submitted for patenting. ing the crack growth speed found in experi- - Examination of the deposition mechanisms ments. of active materials under controlled flow con- Parallel to this project, literature studies were ditions in Couette-autoclaves. New tests carried out in the specialised area of irradia- under special experimental conditions have tion assisted stress corrosion cracking. In Swit- shown that the incorporation of cobalt into zerland this subject is of special interest owing the surface layers during the experiment is to the cracks that have appeared in the core irreversible, but that inactive cobalt-59 and shroud of the Muhleberg Nuclear Power Plant (KKM). Investigations are being made concern-

HSK Annual report 1996 • Research, Training and International Co-operation 77 ing the possibility of launching a research effect of a temperature change (inherent prop- project at the PSI on irradiation assisted stress erty) is smaller for higher burn-up. corrosion cracking. The research on core stability for boiling water reactors also produced some interesting 12.1.3 Simulation models for tran- results. The work of the STARS team in this sient analysis in Switzerland field has received international interest. (STARS II); PSI, Wurenlingen/ During 1996 the STARS team continued its Villigen work aiming at concentrating the computing Within the framework of the STARS II project, tools into a few main computer codes which simulation models are to be developed for all are largely used internationally and which are Swiss nuclear power plants in order to be able competently monitored by the developer, thus to analytically determine their behaviour under guaranteeing an active support for the users. accident conditions. This concentration into a few important codes One of the main tasks of the STARS project and the development into an integrated com- in 1996 concerned analyses for the GOsgen nu- puter program package will also be a valuable clear power plant which are of special interest aid with regard to quality assurance and effi- to the HSK in view of the current periodic safety cient working methods, and is supported by the review (PSR) and the detailed control of the HSK. Gosgen probabilistic safety analysis (GPSA). The first priority was the critical evaluation of 12.1.4 Radioecology, PSI, the computer programs used by the operator Wurenlingen/Villigen; behav- and the manufacturer of KKG in the event or iour of radionuclides in the accident analysis. Experts from the STARS Rivers Aare and Rhine, team participated at a special methodology EAWAG, Diibendorf seminar which the HSK had requested and It is essential to know how radionuclides re- which was organised by the Gosgen nuclear leased into the biosphere will behave in order power plant and SIEMENS/KWU. The STARS to evaluate the doses to the population ex- team's appraisal of the individual computer posed. The radioecological research project of codes for accident conditions was reported in the PSI aims to investigate the behaviour of an internal HSK report. radionuclides in the soil and in plants, while the Within the frame of the GPSA check by the EAWAG is researching the radionuclide behav- HSK, some doubts were raised concerning cri- iour in surface waters. teria for the success of the system in small and The PSI's chief priority is to set parameters medium losses of coolant accidents (LOCA). - adjusted to Swiss conditions - for the For this reason the STARS team therefore car- radioecological computational model ried out a series of LOCA analyses which con- CHECOSYS. This model can be used to cal- firmed the suspicions of the HSK that the crite- culate the doses for the population, based on ria for the success of the system used in the radionuclide concentrations in the air and in the PSA study were indeed incorrect. The models soil, and also to assess how doses could be will be adapted accordingly. reduced in the domain of agriculture by means On behalf of the HSK, analyses of anticipated of suitable measures. transients without scram (ATWS) were contin- Important tasks during 1996 included the PSI ued at the nuclear power plant in Leibstadt. participation in the EU project SEMINAT (long- These analyses had already been introduced term dynamics of radionuclides in semi-natu- in 1995 as part of the assessment procedure ral environment). The PSI, together with the connected with the application for a power Federal Research Institute for Forests, Snow uprate. The results of the analyses support the and Landscape, have started the first field tests requirement made by the HSK for an automatic on a testing ground in Ticino. Measurements reduction of the feedwater flow in the case of of soil samples taken from the surroundings of an ATWS. A corresponding plant modification Chernobyl (but on Russian territory) were con- is to be realised at the KKL during the 1997 tinued at PSI and compared with the data of outage. the Russian project partners. Another task of the STARS team, which is After completion of the three-year EAWAG important for the HSK, is the investigation of project for the investigation of the transport and the high bum-up behaviour of nuclear fuel. One sedimentation behaviour of radionuclides (i.e. significant finding was the dependency of the particularly cobalt) in the aquatic systems down- burn-up on the thermal neutron contribution to stream of Swiss nuclear installations, it became the fuel temperature coefficients. From the point clear that further tests were necessary for a of view of safety, this is significant because the deeper understanding of the processes which occurred. For this reason a new participation

78 HSK Annual report 1996 • Research, Training and International Co-operation agreement between EAWAG and the HSK was the measurement of alpha-emitting nuclides in made, with the following project targets: samples from the Leibstadt nuclear power plant a) Chemical characterization of the radio- (KKL). It is essential to have rapid access to nuclides in waste water. information concerning the type and level of In the previous project, the chemical-physi- contamination in order to instigate adequate cal form of the chief radionuclides in waste safety measures for the personnel working on water from nuclear power plants had proved radioactively contaminated components. The to be a significant factor in the description of PSI developed the alpha-measuring techniques nuclide behaviour. The investigations should still further, in order to achieve good results be extended. within a short time. Comparative tests carried b) Change of the chemistry in contact with river out by PSI have verified the methods of deter- water. mining radionuclides in urine. These tests are to determine the chemical Within the framework of the research form of the radionuclides in river water as a projects on dosimetry, questions of the meas- function of distance from the release point urement of individual contamination after a and season. radiological event were examined. A new sys- c) Significance of colloids and biological parti- tem for individual neutron dosimetry was fur- cles. ther developed and tested in various neutron Attempts will be made to use radioactive par- fields. The suitability of various personnel elec- ticles to extend the methods of particle sepa- tronic dosimeters, for use both by emergency ration and characterisation, and also to study organisations and as a fully recognized and and understand the phenomena of nuclide officially accepted personnel dosimeter, was ex- deposits on these particles. Radionuclide ad- amined. The work of installing and starting up sorption is to be assessed in greater detail, the whole body counter was continued. in parallel with radiochemical studies as a function of time, location and season. 12.1.6 Dose-effects relationship, In 1996 the majority of the tests on water and molecular biological examina- sedimentation dynamics were carried out in the tions and studies of cancer Lake of Biel. The main objectives were to moni- mortality in the neighbour- tor the water from the River Aare and the sub- hood of Swiss nuclear instal- stances it was carrying as it entered the lake, lations; Institute for medici- as well as to characterize the physical proc- nal radiobiology, Zurich; PSI, esses taking place in the lake. Wurenlingen/Villigen; Insti- Another important aspect was the compre- tute for Social and Preventive hensive and specific sampling carried out Medicine, Zurich downstream from each of the nuclear power As the supervisory authority for nuclear instal- plants. lations, the HSK has a duty to ensure that per- Based on the results of previous investiga- sonnel and the public are protected from ioniz- tions, the past year saw the implementation of ing radiation. For this reason the HSK the revised sampling plan for the routine sur- encourages research into the effects of low veillance of activity in the Rivers Aare and doses. Rhine. One area of research concerns the mecha- In summary, it can be said that the results nisms at cell level which repair damage or, if supplied by EAWAG provide a deeper insight unsuccessful, destroy the damaged cells. This into transport phenomena via waste water into research project should help to improve under- surface water - a field which has been far less standing of the behaviour of biological systems researched than that of discharges via outgo- affected by ionising radiation. The findings also ing air into the atmosphere. The results of the have a great potential for application outside investigations will be used practically during the field of radiation protection. routine sampling downstream from the Swiss A further field of research is devoted to nuclear power plants, in collaboration with the literature study and the evaluation of results Section for the Surveillance of Radioactivity from international research into the effects of (SUeR) and the Institute of Applied small doses. It is important to know whether Radiophysics in Lausanne (IRA). the linear dose-effect relationship currently used in radiation protection also applies at low 12.1.5 Radioanalysis and dosimetry; doses. If radiation effects at low doses were PSI, Wurenlingen/Villigen lower than currently assumed, this would have The PSI researched special aspects of far-reaching effects on protection measures radioanalysis and dosimetry on behalf of the after a reactor accident, e.g. in the area sur- HSK. An important part of this work concerned rounding Chernobyl. A reliable, scientifically-

HSK Annual report 1996 • Research, Training and International Co-operation 79 based dose-effect relationship would also have a serious core meltdown accident is also vital an influence on the extent of corrective actions for establishing accident management meas- in residential buildings in the face of increased ures for the limitation and alleviation of the con- concentrations of radon. sequences of such accidents. The findings of In the immediate vicinity of some nuclear the project, which have been presented at plants abroad there has been an increased in- international conferences, have always met with cidence of leukemia in young people. However, great interest. this is neither a general finding, nor the effects At present, a follow-up project is being of ionising radiation, but concerns so-called planned, primarily for the investigation of the "clusters" whose cause is not yet known. convection of the containment atmosphere and The cancer register of the canton of Zurich the thermodynamic behaviour of the sump examines - on behalf of the HSK - the cancer (bubble dynamics on the surface) during flash mortality rate in young people living near the vaporisation. What is more, for the first time, Swiss nuclear installations. These records do the drying out of the sump is to be researched not show any increased incidence in the sur- under realistic conditions. rounding districts. A detailed study in the Lower Aare Valley with its three nuclear installations 12.1.8 Earthquake resistance of showed indeed fewer deaths of young people shear walls in nuclear power from cancer and leukemia than would have plants; Basler & Hofmann, been expected from Swiss statistics. Similar Zurich studies are to be carried out around the other Switzerland is participating in the OECD re- Swiss NPP sites. search project for the validation of calculations Moreover, the HSK participates in investiga- of earthquake resistance of shear walls in tions which supply information about the sig- nuclear power plants. The basic data are taken nificance of the selected statistical analyses. from the rocking table tests on model walls Here, it is important to develop an efficient carried out in Japan. method that can recognize an increase in mor- The comparisons made during the year tality even if the total number of deaths is small. under review using various methods showed The methods of analysis that are available that by using the design standards and refer- today are to be supplemented by a further sys- ring to current practice, the results lead to a temisation of the "variable search screening" conservative resistance level. for deaths, and so should be a tool for nation- With refined assumptions and a method of wide screening for "clusters". calculation reflecting the dynamics of the phenomena a more realistic and practice-oriented 12.1.7 REVENT; Institute for Process calculation is possible. In the follow-up of the Technology, ETH Zurich project, computerised models and results at Under the REVENT project the processes tak- international level will be compared. ing place in the containment, especially the transport of radioactive materials during 12.1.9 Swiss contribution to the depressurisation of the containment, will be NESC1 Project on Pressurised examined under realistic conditions. The ques- Thermal Shock; Basler & tion arises about how radioactive materials from Hofmann, Zurich the sump are released into the containment Thermoshock transients under pressure rep- atmosphere and what proportion gets further resent an exceptional challenge to a reactor into the filter system during an accident. pressure vessel's integrity. This applies chiefly Current theoretical models are based on to those vessels that have been subjected to oversimplified assumptions and usually employ fast neutron irradiation over a long period of constant values for the so-called decontami- time. nation factor, irrespective of the thermodynamic The newly-founded "Network for Evaluation conditions in the containment and independ- of Steel Components" (NESC) has launched ent of the aerosol composition. an international project for experimental study Under the REVENT project, a pilot plant test and analytical calculation of thermal shocks due installation has been built at the ETH in Zurich to injection of cold emergency cooling water in for carrying out representative experiments. reactor pressure vessels as they stay under Both the HSK and the international expert pressure. Switzerland is making a contribution community want to know what the emission to the project in the domain of fracture mechani- levels are under controlled, filtered depressu- cal calculation and analysis. This has the ob- risation in the containment after serious core jective of deriving from the results recommen- meltdown accidents. Detailed knowledge of the dations for practical applications. phenomena occurring in the containment after

80 HSK Annual report 1996 • Research. Training and International Co-operation During the research year under review, the Research into the interaction of molten co- methods for fracture mechanical calculation rium and water, particularly in the initial were worked out and presented in a report. phase of a steam explosion Difficulties with the experimental aspects de- This research is very important because it re- layed the experiments, which could only be re- lates to the ongoing controversy concerning the sumed at the end of 1996. possibility and effect of a steam explosion in the case of reactor pressure vessel failure. An 12.1.10 Melt-structure-water interac- important aspect of this research is the frag- tions during severe accidents mentation of the molten corium after the reac- in LWR's; Royal Institute of tor pressure vessel failure and the cooling of Technology, Stockholm the fragmented molten corium. Experimental The project "Melt-Structure-Water Interactions investigations should help to clarify these de- during Severe Accidents in LWRs" (MWSI) is tails, and thus to better limit the domain in which financed by six organisations and is headed by a steam explosion is possible after a reactor the Royal Institute of Technology (RIT) in Stock- pressure vessel failure. In the absence of any holm (Sweden). Apart from the HSK, the Ameri- detailed understanding of the phenomenon, it can (US-NRC) and the Swedish (SKi) nuclear still has to be assumed in PSA analyses that a safety authorities, as well as various Nordic steam explosion always occurs in the event of nuclear power plant operators, supported the ablation. The consequences vary according to project. Moreover, parts of the project are be- the boundary conditions, and this is taken into ing supported by the EU within the framework account by using probabilistic methods How- of a "Melt-Vessel-Interaction" research pro- ever, in any case, such an evaluation is con- gramme. servative. The project was started in the spring 1994 and is being supported by the HSK for a provisional period of three years as from 1.1.96. By 12.2 PSI Schools participating in this very interesting research project the HSK receives direct access to all The East sector of the Paul Scherrer Institute the results and knowledge acquired so far, and houses two schools: the reactor school and the also has an opportunity to influence the re- radiation protection school. search targets with constructive proposals. In 1996 the focus will be on two subject areas: 12.2.1 Reactor School The reactor school gives basic theoretical ba- Local failure of reactor pressure vessel sic training and advanced training to the staff (vessel hole ablation) of Swiss nuclear installations. In particular the A reactor pressure vessel may become dam- reactor school runs a federally recognized aged in the vicinity of penetrations in the bot- Technical College (TS) specializing in nuclear tom of the vessel, because such parts of the power plant technology. The school is super- vessel are prone to certain weaknesses. The vised by the VSE, the BIGA and the HSK and question arises about how a local failure in the has eight employees and ten lecturers. lower head will open and spread (ablation) In April 1996 seven candidates - two from when molten fuel flows through it.This ques- each of the nuclear power plants at Beznau and tion is important because ablation can affect Gosgen and three from the Muhleberg nuclear the volume of molten core material (corium) power plant - successfully completed the sixth flowing out and therefore implicitly the possi- basic course and received their diplomas as bility and the extent of a steam explosion and TS nuclear power plant technicians. They will of direct containment heating. receive further training at the plants before they The results of previous examinations show that take their examinations to become licensed ablation is an important phenomenon that can reactor operators. occur at a rate of a few mm/s, i.e. a relatively In January 1996, the seventh course for nu- small failure in the vessel can grow very quickly. clear power plant technicians started at the re- All these investigations into ablation also actor school. This course will last until April 1997 serve to develop a theoretical model to predict and is being taken by five participants from the numerically the process of ablation in the case Beznau nuclear power plant. of a serious accident. A model is being devel- For the participants of earlier courses at the oped under the name of HAMIS. reactor school, the year under review presented the last opportunity to qualify as a TS nuclear power plant technician via the backdated quali- fication procedure. Fourteen former students

HSK Annual report 1996 • Research, Training and International Co-operation 81 of the reactor school took advantage of this The Nuclear Safety Convention came into opportunity. force on 24 October 1996 and became binding for Switzerland on 11 December 1996, after rati- 12.2.2 Radiation Protection School fication by the Swiss Parliament. Most of the For several years the PSI radiation protection requirements specified in the Convention have school has offered multilevel courses recog- been applied in Switzerland for many years. nized by the authorities. In the year under re- Two areas require, however, closer examina- view, some 3100 participants were instructed tion: firstly, the Safety Convention requires a (basic education and/or retraining) in the area quality assurance programme for all those of radiation protection. During 1996 the radia- activities that are relevant to nuclear safety. The tion protection school employed six full-time HSK will have to check whether the quality teachers. All the teachers attended specialized assurance programmes in the Swiss nuclear conferences and seminars, while three of them installations and at the HSK itself adequately attended a three-day training course in didac- meet these requirements. Secondly, to main- tic methods. tain independence in the surveillance of nuclear During the year the infrastructure of the installations, the Convention requires that the school underwent further improvements. The surveillance authorities be strictly separate from three classrooms were newly equipped and all organisations concerned with energy pro- many of the measuring instruments were duction. This requirement calls into question replaced with new ones. A modern X-ray the position of the HSK within the Federal Of- machine was installed, similar to those found fice for Energy. in many modern doctors' surgeries. The Convention obliges the countries par- The retraining courses covering the latest ticipating to implement the stipulated measures changes in the radiation protection legislation and to issue regular reports on the status of were no longer necessary in the year under the programmes implemented. The procedure review, because all those concerned from the for monitoring the implementation of the field of nuclear power plants had already required measures will be defined as foreseen received such instruction the previous year. in the Convention at the preparatory meeting This also accounts for the smaller number of of the delegates from the participating coun- course participants compared to the previous tries early in 1997. year. It should be mentioned that 75% of the participants come from the medical profession and 12.4 Co-operation with other emergency organisations. These include students from the Medical Assistants' and Medico- countries Technical X-ray Assistants' School (MTRA) and 12.4.1 Germany members of the fire services, civil defence and The German-Swiss Nuclear Safety Commis- the army. No special on-job training for engi- sion of nuclear installations (DSK) held its 14th neering colleges and universities took place meeting in October 1996 in Solothurn. The during the year under review. Students from report DSK 96/2 for the KKL power uprate to these schools generally attended the courses 3600 MWth was approved. The report for radiation protection experts. DSK 96/1 concerning the ZZL had already been approved earlier, by correspondence. Further- more the DSK reviewed its own organization 12.3 Nuclear Safety Conven- and revised the mandates of its working groups: 1. Installation safety, 2. Emergency protection, tion of the IAEA 3. Radiation protection and 4. Radioactive Every country using nuclear energy for civil waste management. purposes has its own methods for the surveillance of nuclear installations. These methods 12.4.2 France differ when it comes to requirements, proce- The French-Swiss Nuclear Installations Safety dures, depth of assessment, etc. By issuing Commission (CFS) held its 7th meeting in June guidelines, the IAEA has attempted to achieve 1996 in Lyon. The two delegations exchanged a certain standardisation of these methods. information, especially concerning inspections, From this and with time, minimum requirements events, surveillance of ageing and disposal. A have developed, which may be considered as visit was made to the new MELOX fuel assem- a basis for the safe operation of nuclear power bly plant. French observers watched the emer- plants. These requirements were formulated by gency exercise in Leibstadt and delegates from the IAEA and are laid down in the Nuclear Switzerland were able to watch the emergency Safety Convention.

82 HSK Annual report 1996 • Research, Training and International Co-operation exercise at the French nuclear power plant in 12.4.5 Canada Fessenheim. An exchange-of-information agreement was signed with the Canadian safety authorities 12.4.3 Russia (AECB). The first phase of the Swiss-Russian SWISRUS project, which was launched in November 1994 and which is funded by the Swiss Department for Foreign Affairs (EDA) and the Direction for Development and Co-operation (DEZA) and placed under the administration of the HSK, will last until April 1997. The object of this project was to provide the experts of the Russian safety authorities with modern analytical tools for checking safety in their nuclear power plants and to school them in the use of such tools. This was achieved by means of a specific analysis (PSA study) of the Rus- sian plant Novovoronezh-5, a pressurized water reactor rated at 1000 MWe. In this way, apart from the transfer of know-how, it was possible to demonstrate the plant's specific strengths and weaknesses and to indicate some essential, practical improvements that should be made in the plant. Based on the results available for internally caused events, it is clear that these plants still do not have the level of safety of plants in the west and that improvements are called for. It has been found, however, that the safety awareness of the operator increases after being con- fronted with a comprehensive safety analysis covering all aspects of safety. It is planned to continue this project, making probabilistic analyses for occurrences such as earthquakes, fire, flooding etc., and carrying out a safety appraisal of the containment functions.

12.4.4 Slovakia The Swiss Department for Foreign Affairs (EDA) and the Direction for Development and Cooperation (DEZA) are funding the new SWISSLOVAK project. The HSK is leading this project, which serves to support the Slovak safety authorities in the field of safety analysis and will be carried out within the framework of co-operation with Eastern Europe. A safety analysis group will be established under the direct guidance of the Slovak authorities and will carry out both deterministic and probabilistic safety analyses. As part of the exchange of experience organized by the IAEA, three employees of the Slovak safety authorities familiarized them- selves with HSK work in the field of emergency preparedness. A further topic for discussion was the international contacts, which help to keep the HSK up to date with the latest scientific and technological developments. SfEXT PAGH(S) tefft BLAftJK

HSK Annual report 1996 • Research, Training and International Co-operation 83 130 190 250 310nSv/h

100 200 km —I

Ortsdosisleistungskarte der Schweiz mit den Standorten der schweizerischen Kernanlagen Carte des debits de dose ambiante pour I'ensemble de la Suisse, avec indications des sites des installations nucleates Local dose rate in Switzerland with positions of the Swiss nuclear installations Appendix A

Tables TableAl Performance of the Swiss nuclear power plants (1996) 89 Table A2 Numbers of the licensed personnel in the Swiss nuclear power plants as of end 1996 90 Table A3 Reports of plant operators on particular events in 1996 according to HSK Guidelines R-15 and R-25 91 Table A4 Radioactive material released to the environment in 1996 with resulting individual doses 92 Table A5a Whole-body doses from external irradiation in 1996. Nuclear power plants. Totals and distributions of the number of persons and average annual dose 95 Table A5b Whole-body doses from external irradiation in 1996. Research installations. Totals (including NPPs) and distributions of the number of persons and average annual dose 96 Table A6a Whole-body doses from external irradiation in 1996. Annual collective doses in man-millisievert [man-mSv]. Nuclear power plants 97 Table A6b Whole-body doses from external irradiation in 1996. Distribution of annual collective doses in man-millisievert [man-mSv] for research installations, with totals including nuclear power plants 98 Table A7 Whole-body doses from external irradiation in 1996. Number of individuals grouped according to age and sex. All NPP and research personnel, own and external, considered 99 Table A8 Hand and foot doses accumulated in 1996 by individuals occupational^ exposed to ionising radiation resulting from their activities in nuclear power plants and research installations (mainly PSI). Number of individuals according to dose intervals and installations 100 Table A9 Committed effective dose EM resulting from incorporation in 1996 by individuals occupationaliy exposed to ionising radiation resulting from their activities in nuclear power plants and research installations (mainly PSI). Number of individuals according to dose intervalls and installations 101 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 1996, exceeded 200 mSv. Totals and distribution according to dose interval and installations 102 Table A10b Number of persons (plant own personnel) whose accumulated total dose (life-dose) due to occupational exposure up to the end of 1996, exceeded 200 mSv (NPP and PSI). Totals and distribution according to age and dose interval 103 Table A11 Radioactive wastes at the NPP's and PSI. (For PSI are included here wastes from medicine, industry and research) Volume in m3 104

Figures Figure A1 Availability and load factor 1987-1996 (in %) 105 Figure A2 Classified events, subject to notification, 1987-1996 106 Figure A3 Reactor scrams (unplanned) 1987-1996 107 Figure A4 Fuel rod defects (number of rods) 1986-1996 108 Figure A5 Annual collective doses [man-Sv/a] in the NPPs 1980-1996 109 Figure A6 Annual collective doses [man-Sv/a] in Swiss NPPs from 1969-1996 110

HSK Annual report 1996 87 Figure A7 Number of persons with an individual annual whole-body dose over 20 mSv in the nuclear power plants from 1984-1996 111 Figure A8 Average annual individual dose [mSv] of the own and external personnel of the nuclear power plants from 1980-1996 112 Figure A9 Number of individuals (own personnel) of the nuclear power plants who at the end of each of the years between 1980 and 1996 have accumulated integrated doses (life-dose) of more than 200 mSv 113 Figure A10 Calculated dose for the most affected person (adult) in the vicinity of the nuclear power plants 114

88 HSK Annual report 1996 Table A1 Performance of the Swiss nuclear power plants (1996)

KKBI KKBII KKM KKG KKL Thermal energy produced [GWh] 8624 8774 8125 24517 23708 Net electrical energy supplied [GWh] 2753 2754 2649 7874 7705 Thermal energy supplied [GWh] 133.6 7.4 3.09 142.2 - Availability factor1 [%] 88.23 90.1 89.3 93.43 88.7 Non-availability due to annual 11.8 9.9 10.1 6.6 10.4 revision [%] Load factor2 [%] 88.93 89.4 84.5 93.63 85.4 Number of unplanned scrams 3 3 1 0 0 Other unplanned shutdowns 0 0 0 0 0 Load reductions due to faults or 3 5 4 0 1 failures (>10%PN)

' 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. 3 Remark: From the definition of the availability and load factor it arises that the load factor is normally less than the availability. Due to the increase in the actual electrical power by unchanged nominal rating due to an exchange of components (e.g. steam generator, high and low pressure turbines) a load factor higher than 100% results. An adjust- ment of the nominal power would be done by the owner when it is certain that the yearly deviations in the actual electrical power would always remain over the nominal power. Small deviations are, however, tolerated since the electrical nominal power is a typical characteristic of a NPP and should not, if possible, be changed.

HSK Annual report 1996 • Appendix A 89 Table A2 Numbers of the licensed personnel in the Swiss nuclear power plants as of end 1996. In parentheses: 1995 values.

Job title KKB l+ll KKM KKG KKL

B operator 20 (20)' 12 (14) 6 (9) 21 (16) A operator 18 (17) 8 (7) 23 (20) 7 (8) Shift chief and deputy 22 (21) 10 (10) 17 (17) 17 (17) Picket & operations engineers 10 0) 7 (8) 12 (12) 10 (10) Radiation protection controller 4 (5)! 6 (8) 5 (5) 9 (10) Radiation protection chief 6 5 4 6 controller (6) (3) (4) (5)

90 HSK Annual report 1996 • Appendix A Table A3

Reports of plant operators on particular events in 1996 according to HSK Guidelines R-15 and R-25. In parentheses: 1995 values.

Number of reports on International technical events radiological events Nuclear Event Scale (INES) INES4 Plant class S1 class A2 class B3 class S1 class A2 class B3 level KKBI 0 (0) 0 (0) 4 (1) 0 (0) 0 (0) 0 (0) 0 and 1 KKB II 0 (0) 0 (0) 5 (2) 0 (0) 0 (0) 0 (0) 0 KKM 0 (0) 0 (0) 2 (1) 0 (0) 0 (0) 0 (0) 0 KKG 0 (0) 0 (0) 5 (2) 0 (0) 0 (0) 0 (0) 0 KKL 0 (0) 0 (0) 1 (4) 0 (0) 0 (0) 0 (0) 0 PSI 0 (0) 0 (0) 0 (2) 0 (0) 0 (1) 4 (0) 0 EPFL 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) - UNIBS 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) -

1 Events representing a threat to the plant, its personnel or environment. 2 Safety-relevant events with no or only minor off-site radiological impact. 3 Events of slight safety relevance. They are being registered and analyzed to allow for an early detection of possible weaknesses. ' Event classification according to INES scale (levels 0 to 7).

Note: Table A3 serves solely to present the events described in the text in such a way as to provide a clear overview. It cannot be used to compare the safety of different installations. Any attempt of this nature would result in misleading conclusions.

HSK Annual report 1996 • Appendix A 91 Table A4 Radioactive material released to the environment in 1996 with resulting individual doses (see footnotes at the end of the tables)

Release limits (AL) Actual releases2; Calculated effective equiva- Plant Medium Type of releases (according to (±50%) lent doses3 1 regulation ) Adult Child Bq/year Bq/year mSv/year mSv/year KKB 1 + Waste water Nuclide mixture (without tritium)4 4-10'" 3.O-1O*09 <0.001 <0.001 (36000 m3) KKB2 Tritium 7-10*'3 1.2-10''3 <0.001 <0.001

Exhaust air Inert gases 4 MO*'5 2.6-10'12 <0.001 <0.001

Aerosols5 6-10*09 <0.1% AL <0.001 <0.001 (without 1-131; half lite >8 days) lodine-131" 4-1O*09 (1-131 only) 2.51O*07 <0.001 <0.001

6 Carbon-14 - 4.0-10'10 0.0011 0.0018

KKM Waste water Nuclide mixture (without tritium)4 4-10*" 2.0-10'08 <0.001 <0.001 (5978 m3) Tritiurn 2-10*13 2.9-10*1" <0.001 <0,001

Exhaust air Inert gases 4 210*'5 <0.1% AL <0.001 <0.001

Aerosols5 2-10*'° <0.1% AL 0.0089 0.0066 (without 1-131; half life >8 days) lodine-131 210*'° <0.1%AL <0.001 <0.001

Carbon-146 2.0-10-M <0.001 0.0011

KKG Waste water Nuclide mixture (without tritium)4 210*" <0.1%AL <0.001 <0.001 (7358 m3) 3 Tritium 710*' 1.3-10'13 <0.001 <0.001

5 Exhaust air Inert gases4 M0*' (<)1.3-10"'3 <0.001 <0.001 - p total mesurement (<1.1-10*13) Aerosols5 110'" <0.1% AL cO.001 <0.001 (without 1-131; half life >8 days) 09 lodine-131 710* 1.0-10*07 <0.001 <0.001

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

KKL Waste water Nuclide mixture (without tritium)4 4-10*" <0.1% AL <0.001 <0.001 (16822 m3) 13 Tritium 210* 7.1-10*1' <0.001 <0.001

5 Exhaust air Inert gases 4 2-10*' 8.7 10*'2 <0.001 <0.001

Aerosols5 210*'° <0.1% AL <0.001 <0.001 (without 1-131; half lite >8 days) lodine-131 210*'° 7.M0*08 <0.001 <0.001

Carbon-146 2.2-10*" 0.0011 0.0018

92 HSK Annual report 1996 • Appendix A Table A4 (cont.)

Installa- Medium Type of release Release limits (AL)' Actual releases 2. (±50%) Calculated effective equivalent doses : tion Adult Child Bq/year Bq/year mSv/year mSv/year PSI- Waste water Nuclide mixture (without tritium)4' 2.0E+11 (for the entire PSI) <0.1%AL <0.001 <0.001 EAST (18448 m3) Tritium 2.0E+13 (for the entire PSI) <0.1%AL <0.001 <0.001

Other Other Other Other Main stack Incine- Main stack Incine- Main stack Main stack releases releases Incine- releases Incine- releases 7 rator East' rator East rator East' rator East' Exhaust air Inert gases/gases (Ar-41-equ.)4 4-10*12 5-10*' 1.5-10*10 <0.001 <0.001

10 p/y-Aerosols5 MO* MO*09 MO*01 <0.1%AL 4.9-10*07 (without Iodine; half live >8 days) p/y-Aerosols5 2.4-1 o*°r <0.001 r 0.0015 •

Iodine (1-131-equ.)4 3-10*'° 210*09 2-1O*01 2.4-1O*06 2.O-1O*07 <0.001 <0.001 <0.001 <0.001

Tritium (tntiated water) 4-10*12 2-10*1: 2.3-10*10 <0.1% AL 8.0-10*1 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 PSI- Waste water Nuclide mixture (without tritium)4 cp. PSI-East <0.1%AL <0.001 <0.001 WEST (78 m3) Tritium cp. PSI-East <0.1%AL <0.001 <0.001

Other Other Other Other Main sUck Double releases Main stack Double releases Main stack Double releases Main suck Double releases stack West' stack West' suck West' sUck West' 1: Exhaust air Inert gases/gases (Ar-41-equ.)4 5-10* 2-10*'' 8.9-10*13 2.0-10*10 1.2-10*" 0.004 <0.001 cO.001 0.004 <0.001 <0.001

p/y-Aerosols6 2-10* 4.4-10*07 <0.1%AL <0.1%AL

(without lodine&Be-7; T1/2 >8 days) p/^Aerosols5 2.5-10*00 <0.001 <0.001 f <0.001 <0.001 f <0.001 f <0.001 ( 8 hrs.

Iodine (l-131-equ.)4 5-10*™ 1-10*08 4.6-10*08 <0.001 <0.001

1 Tritium (tritiated water) 6-10'1' 2-10't? 4.9-10'11 4.0-10* ' <0.001 <0.001 <0.001 <0.001 Table A4 (Footnotes)

Release limits according to the operating licence effective for the respective nuclear installation. The release limits have been laid down to keep off-site exposure of the critical polulation group in the vicinity below 0.2 mSv/year. For some classes of substances and release locations at PSI, no rigidly laid-down yearly release limit is given, since even if the short-time release limits are constantly fully utilized the dose remains insignificantly small.

2 The measurement of the releases is carried out according to the requirements of the "Regulation on the release of radioactive materials from the nuclear power plant., and on the surveillance of the environment", the "Regulation for the release of radioactive substances and the surveillance in the vicinity of the Paul-Scherrer Institute (PSI)". The accuracy of the measurements is about ±50%. Releases below 0.1% of the yearly release limits are regarded by HSK as not relevant and are reported as "<0.1% AL" (release limit). When no nuclide-specific measurements are available, a standard nuclide mixture is assumed for the calculation of the dose and for equivalence conversions. For KKB, a mixture of 50% Co-60 and 50% Cs-137 is assumed for the aerosols. For KKG, a total fS-measurement is performed for the inert gases (see values in the brackets). Therefore, for the calculations (release-equivalent as well as dose) a mixture of80%Xe-133,10%Xe-135 and 10% Kr-88 is assumed and applied.

3 Calculated annual effective equivalent doses for persons living at the critical location under the additional assump- tion that these persons only eat food which is grown at this point and drink water from the river directly downstream from the plant or PSI (mean water-carriage of the river Aare at Muhleberg is 3.8-109 m3/year; at G&sgen 9.0-109 mVyear; at Wurenlingen (PSI) and at Beznau 1.8-1010 m3/year and of the river Rhein at Leibstadt 3.3-10'° m3/year). Doses smaller than 0.001 mSv - equivalent to the dose accumulated from natural radioactivity in about ten hours - are not reported. The calculations are performed according to the draft HSK-Guideline R-41. This contains a model and the defined parameters.

4 Declarations in release equivalents: Waste water: releases in Bq/year 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 200 Bq/kg corresponds to a reference nuclide with an ingestion dosis-factor of 5-10 8 Sv/Bq. Inert gases: releases in Bq/year normalised to a reference CA value of 2-10*5 Bq/m3(for NPPs) and 5-10*" Bq/m3 (for PSI, Argon-41 equivalent). The CA values for the inert gas nuclides are taken from appendix 3 of the radiological protection ordnance (StSV). A CA value of 2-10*5 Bq/m3 corresponds to a reference nuclide with an immersion dosis- factor of 4.4-10"7 (Sv/year)/(Bq/m3). Iodine: (for PSI); lodine-131 equivalent calculated by a weighted summation of the releases of all iodine nuclides reaching the weighting factor by the ratio between the ingestion dose factor of the appropriate nuclide and the ingestion dose factor of iodine-131. The ingestion dosis factors are taken from StSV

5 The contribution to the dose from aerosols with a half-life less than 8 days is negligible for the nuclear power plants. In the case of PSI-West extremely short-lived aerosols possibly may play a role for inhalation and immersion as well as in a smaller extend for the irradiation from the soil. Thereby, under very conservative assumptions, a contribution of about 50% of the aerosol dose due to long-lived aerosols may be estimated. In the case of KKM, the main contribution to the dose stems from soil-deposited aerosols which were unintentionally released in 1986. The dose contribution through aerosol releases in the year under review is small compared to this and lies within the order of magnitude of other Swiss nuclear power plants.

6 The reported releases of C-14 are, with the exception of KKL, where the C-14 releases are measured, based on estimates of HSK founded on temporary measurements in the power plants in earlier years.

7 Dispersion equivalents: In order to restrict the number of release limits for PSI, various release locations are combined and treated as one under "other releases East" and "other releases West". This is only possible if the actual releases measured are converted to dispersion equivalent values by scaling them, using the dispersion factor, to the properties (i.e. level of release above ground and velocity of released gases) of a reference release point. The table gives both the release limits and the releases for "other releases" East and West as the dispersion equivalent values.

94 HSK Annual report 1996 • Appendix A Table A5a Whola-body doses from external irradiation in 1996. Nuclear power plants. Totals and distributions of the number off persons and average annual dose.

Dose KKB l+ll KKG KKL KKM Total NPP1 distribution [mSv] E F E+F E F E+F E F E+F E F E+F E F E+F > 0.0 -1.0 199 432 631 201 361 562 216 1103 1319 131 703 834 747 2247 2994 > 1.0 - 2.0 60 69 129 28 41 69 65 163 228 37 87 124 190 323 513 > 2.0 - 5.0 71 91 162 35 59 94 52 186 238 70 84 154 228 405 633 > 5.0-10.0 25 22 47 25 25 50 19 65 84 26 39 65 95 162 257 > 10.0 -15.0 5 5 7 7 1 4 5 5 5 10 18 9 27 > 15.0-20.0 1 1 1 2 3 > 20.0 - 25.0 > 25.0 - 30.0 > 30.0 - 35.0 > 35.0 - 40.0 > 40.0 - 45.0 > 45.0 - 50.0 over 50.0 Total persons 360 614 974 297 486 783 353 1521 1874 269 918 1187 1279 3148 4427 Average per 1.6 1.0 1.2 1.6 0.9 1.2 1.3 1.0 1.0 2.0 0.9 1.2 1.6 1.1 1.2 person [mSv]

1 Individuals from external external personnel having worked successively in several installations are counted here only once. to E = plant own personnel, F = external personnel; TL-dosimeters used in all plants to en Table A5b

Whole-body doses from external irradiation in 1996. Research installations. Totals (including NPPs) and distributions of the number of persons and average annual dose.

Dose University of Total Total NPP Total NPP and distribution PS! EPFL Basle Research' E+F Research2 [mSv] 0.0- 1.0 1077 8 4 1089 2994 4022 > 1.0-2.0 51 52 513 565 > 2.0-5.0 44 44 633 677 >5.0- 10.0 7 7 257 264 > 10.0- 15.0 27 27 > 15.0-20.0 3 3 > 20.0 - 25.0 > 25.0 - 30.0 > 30.0 - 35.0 > 35.0 - 40.0 > 40.0 - 45.0 > 45.0 - 50.0 over 50.0 Total persons 1179 8 4 1192 4427 5558 Average per 0.4 0.0 0.2 0.4 person [mSv] 1.2 1.1

1 This column contains the value for one person (1.01 mSv annual dose), working at the decommissioned Lucens nuclear power plant. 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

Whole-body doses from external irradiation in 1996. Annual collective doses in man-millisievert [man-mSv]. Nuclear power plants

1 Dose distribution KKB l+ll 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 45.2 85.0 130.2 45.8 46.8 92.6 41.4 253.9 295.3 30.4 141.7 172.0 162.8 493.3 656.1 > 1.0 -2.0 85.7 104.0 189.7 42.5 60.3 102.8 96.7 242.6 339.3 56.1 120.9 177.0 281.0 476.4 757.4 > 2.0 - 5.0 215.4 293.1 508.5 106.8 184.8 291.6 173.6 557.1 730.6 230.1 280.7 510.8 725.8 1275.2 2001.0 >5.0- 10.0 175.0 142.0 317.0 167.3 165.2 332.5 125.3 420.5 545.7 179.0 252.4 431.4 646.6 1072.5 1719.1 > 10.0-15.0 55.8 55.8 86.3 86.3 11.0 42.7 53.7 54.8 54.7 109.5 207.9 99.5 307.4 I > 15.0-20.0 15.2 15.2 15.2 31.3 46.5 c 3 > 20.0 - 25.0 •§ > 25.0 - 30.0 > 30.0 - 35.0 > 35.0 - 40.0 > 40.0 - 45.0 > 45.0 - 50.0 over 50.0 Total [man-mSv] 577.1 624.1 1201.2 463.9 457.0 920.9 447.9 1516.7 1964.6 550.3 850.4 1400.7 2039.2 3448.3 5487.5 Highest individual 13.6 9.6 13.6 15.2 9.7 15.2 11.0 11.0 11.0 11.6 11.8 11.8 15.2 15.1 15.2 dose [mSv]

1 It happens that by the addition of the individual doses received in different installations some differences appears in the collective doses in some dose intervals E = plant own personnel, F = external personnel

j co 00 Table A6b Whole-body doses from external irradiation in 1996. Distribution of annual collective doses in man-millisievert [man-mSv] for research installations, with totals including nuclear power plants

Dose distribution Total NPP Total NPP and PSI EPFL University of Basle Total research1 [mSv] E+F Research2

> 0.0 -1.0 171.5 0.6 0.7 172.8 656.1 828.9 > 1.0 -2.0 71.7 72.7 757.4 830.0 > 2.0 - 5.0 141.7 141.7 2001.0 2142.7 >5.0- 10.0 46.3 46.3 1719.1 1765.4 > 10.0-15.0 307.4 307.4 > 15.0-20.0 46.5 46.5 > 20.0 - 25.0 > 25.0 - 30.0 > 30.0 - 35.0 > 35.0 - 40.0 > 40.0 - 45.0 > 45.0 - 50.0 over 50.0 Total [man-mSv] 431.2 0.6 0.7 433.5 5487.5 5920.9 Highest individual 9.3 0.4 0.7 9.3 15.2 15.2 dose [mSv]

1 This column contains the value for one person (1.01 mSv annual dose), working at the decommissioned Lucens nuclear power plant. 3 It happens that by the addition of the individual doses received in different installations (research and NPP) some differences appears in the collective doses in some dose intervals. E = plant own personnel, F = external personnel Table A7 Whole-body doses from external irradiation in 1996. Number of individuals grouped according to age and sex. All NPP and research personnel, own and external, considered.

16-18 19-20 21 -30 31 -40 41 -50 51 -60 >60 Dose distribution Total years years years years years years years {mSv] M F M F M F M F M F M F M F 0.0-1.0 10 1 52 2 816 42 1037 50 1024 29 769 40 148 2 4022 > 1.0-2.0 5 127 4 184 2 140 4 81 1 17 565 > 2.0 - 5.0 1 2 155 1 227 194 90 7 677 > 5.0-10.0 60 88 74 37 5 264 > 10,0 -15.0 2 11 7 6 1 27 > 15.0-20.0 2 1 3 > 20.0 - 25.0 > 25.0 - 30.0 > 30.0 - 35.0 > 35.0 - 40.0 > 40.0 - 45.0 > 45.0 - 50.0 over 50.0 Total persons 11 1 59 2 1162 47 1547 52 1440 33 983 41 178 2 5558 Average per 0.40 1.00 0.37 1.14 0.28 1.26 0.16 1.12 0.32 0.88 0.08 0.64 1.07 person [mSv] Collective dose 4.4 1.0 22.0 1320.7 13.0 1943.1 8.5 1616.4 10.6 863.4 3.4 114.5 5920.9 [man-mSv]

M = male, F = female

CO CD o o Table A8 Hand and foot doses accumulated in 1996 by individuals occupationally exposed to ionising radiation resulting from their activities in nuclear power plants and research installations (mainly PSI). Number of individuals according to dose intervals and installations.

Total NPP Dose distribution KKB HI KKG KKL KKM Total NPP PSI , and PSI [mSv] E F E+F E F E+F E F E+F E F E+F E F E+F E + F 0.0 - 25.0 8 28 36 5 8 13 4 2 6 15 24 39 32 62 94 81 175 > 25.0 - 50.0 3 3 1 2 3 1 5 6 4 10 > 50.0 - 75.0 I I > 75.0-100.0 > 100.0 -150.0 2 2 2 2 2 > 150.0-200.0 > 2000 - 250.0 > 250.0 - 300.0 > 300.0 - 350.0 > 350.0 - 400.0 > 400.0 - 450.0 > 450.0 - 500.0 1 1 over 500.0 Total persons 8 28 36 7 11 18 5 4 9 15 24 39 35 67 102 86 188

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

Committed effective dose E50 resulting from incorporation in 1996 by individuals occupationaiiy exposed to ionising radiation resulting from their activities in nuclear power plants and research installations (mainly PSI). Number of individuals according to dose intervalls and Installations.

Committed Total effective dose KKB l+ll KKG KKL KKM Total NPP PSI NPP E50 and PSI Dose distribution [mSv] E F E + F E F E + F E F E + F E F E + F E F E + F E + F 0.0-1.0 170 299 469 285 483 768 355 1433 1788 269 918 1187 1079 3133 4212 427 4639

I > 1.0-2.0

eKAn n n > 2.0 - 5.0 1 1 ua l r e > 5.0-10.0 D o > 10.0 -15.0 99 6 > 15.0-20.0

| > 20.0 - 25.0

X > 25.0 - 30.0 > 30.0 - 35.0 > 35.0 - 40.0 > 40.0 - 45.0 > 45.0 - 50.0 over 50.0 Total persons 170 299 469 285 483 768 355 1433 1788 269 918 1187 1079 3133 4212 427 4639 Medical 461 396 857 287 287 343 343 269 77 346 1360 473 1833 829 2662 examinations

Persons by which in the screening mesurement did not exceeded the predetermined threshold are noted in this Table in the E50 dose distribution between 0-1.0 mSv. o 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 1996, exceeded 200 mSv. Totals and distribution according to dose interval and installations.

Dose distribution Total NPP KKB l+ll KKG KKL KKM Total NPP PSI [mSv] and PSI > 200.0 - 250.0 26 5 16 47 4 51 > 250.0 - 300.0 19 1 1 8 29 1 30 > 300.0 - 350.0 15 1 3 19 1 20 > 350.0 - 400.0 5 4 9 9 > 400.0 - 450.0 6 3 9 9 > 450.0 - 500.0 4 7 11 11 > 500.0 - 550.0 3 3 3 > 550.0 - 600.0 1 1 1 over 600.0 1 1 1 L Total persons 80 1 41 129 6 135

including individuals who left during the course of 1996 Table A1 Ob Number of persons (plant own personnel) whose accumulated total dose (life-dose) due to occupational exposure up to the end of 1996, exceeded 200 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 200.0 - 250.0 2 14 34 1 51 > 250.0 - 300.0 13 13 4 30 > 300.0 - 350.0 7 12 1 20 > 350.0 - 400.0 7 2 9 > 400.0 - 450.0 1 7 1 9 > 450.0 - 500.0 3 8 11 > 500.0 - 550.0 2 1 3 > 550.0 - 600.0 1 1 over 600.0 1 1 Total persons 2 40 84 9 135

This table includes individuals who left during 1996.

HSK Annual report 1996 • Appendix A 103 Table A11 Radioactive wastes at the NPP's and PSI. (For PSI are included here wastes from medicine, industry and research) Volume in m3

unconditioned conditioned1 Amount arising2 Total3 Production2 Total3 PSI 162 320 15 715 KKB 149 75 10 877 KKM 111 507 50 274 KKG 47 52 15 209 KKL 190 290 60 1065 Total 659 1244 150 3140

1 A reduction in volume occurs during conditioning burnable and compressible wastes 2 Volumes in reporting period, 1996 3 Volumes in storage facilities of the NPP's and PSI at the end of 1996

104 HSK Annual report 1996 • Appendix A Figure A1 Availability and load factor 1987-1996 (in %)

100 I availability 95 • load factor

KKB I, II r 7- * I ! i .' "Jill I 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

100 • availability 95 ED load factor 90

KKM 85

70 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

KKG

1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

*K-:::-:3xr KKL

S ! _ I . 1_ 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

HSK Annual report 1996 • Appendix A 105 Figure A2 Classified events, subject to notification, 1987-1996

14 ! KKB I: only events 12 ; KKB II: only events 10

8 KKB I, II 6 4 2 0 _MI 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

14 12 10 8 KKM 6 4 2 0 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

14 ! only events B 12 10 8 - KKG 6 4 2 0 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

14 \ events B 12 I events A 10 KKL

4 -- 2 0 - 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

106 HSK Annual report 1996 • Appendix A Figure A3 Reactor scrams (unplanned) 1987-1996

II KKB I 4 KKB II 3 - KKB I, II 2 -

o - 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

KKM

1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

KKG

1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

5 -

3 y KKL 2 -•

1 -

1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

HSK Annual report 1996 • Appendix A 107 Figure A4

Fuel rod defects (number of rods) 1986-1996

• KKB I: slight damage (e.g. hair cracks) 3 — • KKB I: larger damage KKBI KKB II: no damage

1 -

86/87 87/88 88/89 89/90 90/91 91/92 92/93 93/94 94/95 95/96

L; only slight damage

3 -•

KKM

86/87 87/88 88/89 89/90 90/91 91/92 92/93 93/94 94/95 95/96

C slight damage

I larger damage KKG 2 -

86/87 87/88 88/89 89/90 90/91 91/92 92/93 93/94 94/95 95/96

L. slight damage 3 r

KKL

86/87 87/88 88/89 89/90 90/91 91/92 92/93 93/94 94/95 95/96

108 HSK Annual report 1996 • Appendix A Figure A5 Annual collective doses [man-Sv/a] in the NPPs 1980-1996

• power operation

m shutdown for refuelling ™ and maintenance

KKB I, II

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

12 li power operation 10 . shutdown for refuelling and maintenance 8

KKM 6 —

W? ",''

...... % \ """SS SIS*! >* "t " J Sir

0 s-~ 1980 81 8283848586 87 888990 91 929394 95 96

12 - • power operation 10 - . shutdown for refuelling and maintenance 8 —

KKG 6 ~ 4

7. ,.. ;A^V . .jy. 1980 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96

12 — D power operation 10 — shutdown for refuelling and maintenance 8 —

KKL 6

4 --

0 1980 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96

HSK Annual report 1996 • Appendix A 109 Figure A6 Annual collective doses [manSv/aJ in Swiss NPPs from 1969-1996

-KKB KKB l+ll -KKG KKG KKL -KKM KKM -PS PSI 12

I en >

CO 6 C

1969 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96

plant own and external personnel calendar year Figure A7 Number of persons with an individual annual whole-body dose over 20mSv in the nuclear power plants from 1984-1996 200

160 —

120 i— KKB I, II 89 80 56 60 40 38 23 , i —,-, 0 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

200 187

160

120 KKM 80 JL 46 40 22 0 -' 0 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

200

160 -

120 KKG 80

0 0 0 0 0 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

200

160

120 KKL 80

40 27

1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

HSK Annual report 1996 • Appendix A 111 Figure A8 Average annual individual dose [mSv] of the own and external personnel of the nuclear power plants from 1980-1996

J plant own personnel

• external personnel

•M I _ KKB I, II

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

12 f [J plant own personnel 10 •— H external personnel 8

KKM 6 4 - f i; -1 2

0 1980 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96

12 — D plant own personnel 10 \ external personnel 8 —

KKG 6

2 -

0 1980 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 9

12 u plant own personnel 10 \ external personnel 8 — KKL 6 I -

4 —

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

112 HSK Annual report 1996 • 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 1996 have accumulated integrated doses (life-dose) of more than 200 mSv.

120 — 106 107 105 102 99 -96- 100 • 91 93 93 91 84 80 80 — 70 KKB I, II 60 40

0 1980 1981 1982 198319841985 19861987 1988 198919901991 19921993 199419951996

120

100 — •

80 — KKM 60 41 40 41 40 _3I 3Z- 30 30 29 32 23 20 ---

0 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 190) 1991 1992 1993 1994 1995 1996

120

100

80 KKG 60 40

20 o 1 1 19801981 19821983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

120

100

KKL 60

0 19801981 1982198319841985198619871988198919901991 19921993199419951996

HSK Annual report 1996 • Appendix A 113 Figure A10 Calculated dose for the most affffected person1 (adult) in the vicinity off the nuclear power plants

KKBI/II KKG KKL 1000.0

100.0 to 8. c C

8 10.0 l o o "E

0.1 1976 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 year

1 Fictitious person, permanently located at the critical place, obtaining all food from the area and all drinking water from the river downstream of the nuclear power plant in question. 2 Dose guideline as a function of source (StSV Art. 7, HSK Guideline R-11) 3 Values below 1 microsievert are not shown as such on the Figure, they are placed on the 1 microsievert line for convenience. Appendix B

Tables Table B1 List of the Swiss Guidelines (R) and Recommendations (E) presently in force 116 Table B2 International Nuclear Event Scale (INES) 119 Table B3 Basic characteristics of the Swiss nuclear power plants 121

Figures Figure B1 Functional diagram of a nuclear power plant with a pressurised water reactor 122 Figure B2 Functional diagram of a nuclear power plant with a boiling water reactor 122

List of Abbreviations 123

Pictures 126

HSK Annual report 1996 • Appendix B 115 Table B1 List of the Swiss Guidelines (R) and Recommendations (E) presently in force

Status: as of end 1996 Languages: All guidelines originally written in German; guidelines noted IE, IF or /R translated into and available in English, French or Russian. For guidelines denoted with "*", only the title has been translated into English.

Date of current Guideline Title of Guideline issue

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

Supervisory procedures governing ihe construction of nuclear power R-05* plants: Mechanical equipment (Aufsichtsverfahren beim Bau von October 1990 Kemkraftwerken: mechanische Ausrustungen)

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

Guideline for radiation protection zones in nuclear installations and in Paul R-07* Schemer Institute (Richtlinie fur den uberwachten Bereich der Kemanlagen Juni 1995 und des Paul Scherrer Institutes)

R-07/F Directives concemant les zones de radioprotection dans les installations July 1977 R-07/R nucleates

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

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

Objectifs de la protection des personnes contre les radiations ionisantes R-11/F July 1978 dans la zone confluence des centrales nucleaires

Dosimetry for occupationally radiation exposed personnel of nuclear R-12* installations (Erfassung der Dosen des beruflich strahlenexponierten December 1979 Personals von Kemanlagen)

R-U/E Conditioning and Interim Storage of Radioactive Wastes (Konditionierung December 1968 R-14/R und Zwischenlagerung radioaktiver Abfalle)

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

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

R-17* Organization and personnel of nuclear power plants (Organisation und August 1986 R-17/R Personal von Kemkraftwerken)

Protection Objectives for the Disposal of Radioactive Waste (Schutzziele November 1993 R-21E fur die Endlagerung radioaktiver Abfalle)

R-21/F Objectifs de protection pour le stockage final des dechets radioactifs November 1993

Revisions, testing, replacement, repair and modification of electrical equipment in nuclear installations (Revisionen, Prufungen, Ersatz, R-23* December 1993 Reparaturen und Anderungen an elektrischen Ausrustungen in Kemanlagen)

116 HSK Annual report 1996 • Appendix B Table B1 (cont.) List of the Swiss Guidelines (R) and Recommendations (E) presently in force

Date of current Guideline Title of Guideline issue

Reporting Guideline concerning the nuclear installations of the Swiss Confederation, of the Cantons, of PSI and the decommissioned Lucens R-25* experimental nuclear power plant (Berichterstattung der Kemanlagen des May 1990 Bundes, der Kantone, des PSI sowie des stillgelegten Versuchsatomkraftwerks Lucens)

Notification relative aux installations nucteairesde la Confederation et des R-25/F Cantons, a I'lnstitut Paul Scherrerjainsi qu!a la centrale nucleaire April 1989 experimental d^saffectee de Lucens

Selection, training and examination of NPP staff requiring a license R-27* (Auswahl, Ausbildung und Prufung des iizenzpflichtigen Betriebspersonals May 1992 von Kernkraftwerken)

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

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

Guideline for meteorological measurement on sites of nudear installations R-32* (Richtlinie fur die meteorologischen Messungen an Standorten von September 1993 Kemanlagen)

Supervisory procedures governing the construction of nuclear power R-35* plants: System engineering (Aufsichtsverfahren beim Bau und Mai 1996 Anderungen von Kemkraftwerken, Systemtechnik)

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

Interpretation of the term "derived guideline value for surface R-38* contamination" (Interpretation des Begriffs "abgeleiteter Richtwert fur July 1987 Oberflachenkontami nation")

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

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

Responsibility for decisions to implement particular measures to mitigate the consequences of a severe accident at a nuclear installation R-42/E March 1993 (Zustandigkeiten fur die Entscheide uber besondere Massnahmen bei einem schweren Unfall in einer Kemanlage; Februar 1993)

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

Design Criteria for Safety Systems of Nuclear Power Plants with Light R-101/E Water Reactors (Auslegungskriterien fur Sicherheitssysteme von May 1987 Kernkraftwerken mit Leichtwasser-Reaktoren)

Design Criteria for the Protection of Safety Equipment in NPP against the Consequences of Airplane Crash (Auslegungskriterien fur den Schutz von R-102/E December 1986 sicherheitsrelevanten Ausrustungen in Kemkraftwerken gegen die Folgen von Flugzeugabsturz; October 1986)

Plant internal measures against severe accidents (Antageinteme R-103* November 1989 Massnahmen gegen schwere Unfalle)

HSK Annual report 1996 • Appendix B 117 Table B1 (cont.) List of the Swiss Guidelines (R) and Recommendations (E) presently in force

Recom- Date of current Title of Recommendation mendation issue

Recommendations for the Planning and Execution of Emergency Exercises in Swiss Nuclear Power Plants (Empfehlungen fur die Planung E-03/E und Durchfuhrung von Notfallubungen in den schweizerischen October 1991 Kemkraftwerken; Mai 1990)

Control centers and emergency rooms of NPP: Requirements on design and equipment for accident management (Steuerstelien und Notfaliraume E-04* von KKW: Anforderungen betr. Ausfuhrungen und Ausrustungen fur December 1989 Accident Management)

118 HSK Annual report 1996 • Appendix B Table B2 International Nuclear Event Scale (INES) The international scale used to indicate accident severity in nuclear installations (International Nuclear 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

• 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.

• External release of fission products (in quantities radiologically 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.

• 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. • Severe damage to a large fraction of the Three Mile Island core and major plant contamination. USA, 1979 • 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 4 significant off-site risk food control. • Some damage to reactor core as a result of Saint Laurent, mechanical effects and/or melting. France, 1980 • Worker doses likely to have acute fatal consequences.

HSK Annual report 1996 * Appendix B 119 Table B2 (cont.) International Nuclear Event Scale (INES)

Level Descriptor Criteria Examples j • 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. • Exposure of personnel sufficient to cause acute health effects. Severe spread of Serious incident contamination inside the plant. • 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.

• Incidents with major failure of safety • Sosnowy Bor, provisions, but still leaving sufficient safety Russia, 1992 margins to cope with additional faults. Incident • 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.

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

• 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.

120 HSK Annual report 1996 • Appendix B Table B3 Basic characteristics of the Swiss nuclear power plants

KKBI KKBII KKM KKG KKL Thermal power [MW] 1130 1130 1097 3002 3138 364 364

Electrical power [MW] from from 372 from 1085 1.10.1996 1.10.1996 1.1.1996 380 374 1020 350 350

Net electrical power [MW] from from 355 from 1030 1.10.1996 1.10.1996 1.1.1996 365 357 970 Reactor type PWR PWR BWR PWR BWR Westing- Westing- Reactor supplier 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 1969 1971 1972 1979 1984 operation

HSK Annual report 1996 • Appendix B 121 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

Reheater V Water separator

High-pressure Low-pressure turbine turbine Generator

Recirculating pump Reactor High-pressure feedheater

Condenser

Feedwater Low-pressure pump feedheater

122 HSK Annual report 1996 • Appendix B List of Abbreviations

A AN PA System for automatic transmission of plant parameters from the NPPs to the HSK ASP Ageing Surveillance Programme ATWS Anticipated Transient Without Scram B BAG Swiss Federal Office of Public Health BEW Swiss Federal Office of Energy BIGA Swiss Federal Office for Industry, Commerce and Work BIOMOVS Biospheric Model Validation Study BKW BKW FMB Energie AG BNFL British Nuclear Fuels Ltd Bq Becquerel = radioactivity (1 Bq = 2.7-10"11 Ci) BWR (SWR) Boiling Water Reactor BZL Swiss Federal interim storage facility BZS Swiss Federal Office for civil defence C COGEMA Compagnie Générale des Matières Nucléaires, La Hague CVRS Cement Volume Reduction and Solidification D DSK German-Swiss Nuclear Safety Commission DWR Pressurised Water Reactor E EAWAG Swiss Federal Bureau for Water Supply, Waste Water Purification and Water protection EKS Federal Commission for Radiation Protection EPFL Swiss Federal Institute of Technology, Lausanne EU European Union EVED Federal Department of Transport, Communications and Energy (Ministry)

G GE General Electric Company GNW Co-operative for Nuclear Disposal Wellenberg GWh Gigawatthours = 109 Watthours H HAA High-level waste HRA Human Reliability Analysis HSK Swiss Federal Nuclear Safety Inspectorate

IAEA International Atomic Energy Agency INES International Nuclear Event Scale IRA Institut de Radiophysique Appliquée, Lausanne

K KKB Nuclear Power Plant Beznau KKG Nuclear Power Plant Gôsgen KKL Nuclear Power Plant Leibstadt KKM Nuclear Power Plant Muhleberg KNE Commission for Nuclear Waste Disposal Kr Krypton KSA Swiss Federal Nuclear Safety Commission KUeR Swiss Federal Commission for Radioactivity Surveillance

HSK Annual report 1996 • List of Abbreviations 123 List of Abbreviations (cont.)

L 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 Man Sv = collective radiation dose (1 man-Sv = 100 man-rem) MGy Mega-Gray = 106 Gray (1 Gray = 100 rad) MMI Man-machine interaction MOX Mixed oxide (uranium-plutonium) mSv Milli-Sievert = 10"3 Sievert MW Megawatt = 106 Watt (power unit) MWe Megawatt electrical power MWth Megawatt thermal power u.Sv Micro-Sievert = 10"6 Sievert 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 NAZ National emergency operation center NOK Nordostschweizerische Kraftwerke AG NPP (KKW) Nuclear power plant NRC Nuclear Regulatory Commission (USA) O OECD Organisation of Economic Cooperation and Development OSART Operational Safety Review Team (IAEA) P PSE(PSO) Periodic safety examination PSI Paul Scherrer Institute, Wurenlingen and Villigen (East and West) PWR (DWR) Pressurised water reactor Q QA(QS) Quality assurance R RPV Reactor pressure vessel REFUNA Regional heat supply system of the lower Aare valley S SAA Low-level wastes SMA Low- and Medium-level Active Wastes SRM Source Range Monitor StSG Radiation protection law StSV Radiation protection Ordinance 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) SWR Boiling Water Reactor T TBq Terabequerel (1TBq = 1012 Bq) THORP Thermal Oxide Reprocessing Plant TLD Thermal-Luminescent Dosemeter U V VAKL Experimental nuclear power plant, Lucens VSE Union of Swiss Electricity Producers

124 HSK Annual report 1996 • List of Abbreviations List of Abbreviations

x Xe Xenon

Z ZWIBEZ Interim radwaste storage facility, KKB ZWILAG Interim Storage Facility, Wurenlingen ZZL Central interim storage facility, Wurenlingen

HSK Annual report 1996 • List of Abbreviations 125 Pictures by courtesy of:

Cover Page 10 Page 20 Institute for Geo-Physics; ETH, Zurich Beznau Nuclear Power Plant BKW FMB Energie AG, Berne

Page 29 Page 36 Page 44 GOsgen Nuclear Power Plant Leibstadt Nuclear Power Plant ZWILAG, Baden

Page 48 Page 58 Page 64 Paul Scherrer Institute, Villigen NAGRA, Wettingen HSK, Wurenlingen

Page 68 Page 86 Leibstadt Nuclear Power Plant Institute for Geo-Physics; ETH, Zurich

126 HSK Annual report 1996 • Pictures HSK, Wurenlingen (Switzerland) Postal address: HSK, CH-5232 Villigen-HSK Phone: 056 31038 11 Telefax: 056 310 39 95 and 056 310 39 07 Telex: 827 472 ask ch Internet: http://www.hsk.psi.ch