Extrait de la publication…Auteurs : Rene Coulon, Jacques Delmas, Gerard Griperay, Philippe Guetat,...

Extrait de la publication

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ELEMENTSOF NUCLEAR SAFETY

Jacques LIBMANN

English translation by Jean Mary Dalens

Avenue du HoggarZone Industrielle de Courtab&oelig;uf

BP 11291944 Les Ulis cedex A, France


Book series coordinated by Henri Mètivier

Books already published:

Agriculture, Environnement et Nuclèaire : comment reagir en cas d'accidentAuteurs : Rene Coulon, Jacques Delmas, Gerard Griperay, Philippe Guetat, ReneLoyau, Claude Madelmont, Rèmy Maximilien, Jean-Claude Rottereau

Traitement de la contamination interne accidentelle des travailleursAuteurs : M.H. Bhattacharyya, B.D. Breistenstein, H. Mètivier, B.A. Muggenburg,G.N. Stradling, V. Volf

Approche de la surete des sites nuclèairesAuteur : Jean Faure

Circonstances et consequences de la pollution radioactive dans I'ancienneUnion soviètique

D. Robeau, Coordinateur.Auteurs : Jean-Claude Nènot, Christian Chenal, Sabine Charmasson, DanielRobeau, M. Bertin, Philippe Renaud, Henri Maubert, Andre Jouve, AlexandreGrebenkov

Elements de sûretè nuclèaire

Elements of Nuclear Safety (Russian version in preparation)Auteur: Jacques Libmann

Le tritium - de I'environnement a I'HommeYves Belot, Monique Roy et Henri Mètivier, Coordinateurs.Auteurs : Y. Belot, M. Roy, H. Mètivier, P. Pihet, Ph. Duport, A. Flüry-Hèrard,E. Rabin, Ph. Boucquey, F. Briot, P. Giroux, J.Y. Hervè, J.P. Le Goff et G. Pescayre

Radionuclides in the OceansP. Guèguèniat, P. Germain and H. Mètivier, Coordinators

ISBN : 2-86883-286-5

This work is subject to copyright. All rights are reserved, whether the whole or part of the material isconcerned, specifically the rights of translation, reprinting, re-use of illustrations, recitation, broad-casting,reproduction on microfilms or in other ways, and storage in data banks. Duplication of this publication orparts thereof is only permitted under the provisions of the French Copyright law of March 11, 1957.Violations fall under the prosecution act of the French Copyright Law.

© Les Editions de Physique 1996


This basically educational document draws much of its substance from allthe various activities of the Institute for Nuclear Safety and Protection(IPSN), the technical support body of the Nuclear Installation SafetyDirectorate (DSIN). The latter organizations however may under no circum-stances be considered liable for its contents.

Its purpose was to heighten awareness among analysts and more gener-ally among all those concerned by nuclear safety. The safety picture present-ed is consequently not intended to be well-balanced. It is moreover imbuedwith the activities and viewpoints of the IPSN, which is only one of the safe-ty organisms concerned.

The present document is an extensively supplemented revision of workpublished in 1988 by the National Institute for Nuclear Science andTechnology (INSTN) under the title "Approche et analyse de la sûretè desrèacteurs eau sous pression". As in the previous case, this work would nothave been possible without the technical and financial assistance of theDSIN. The personal acknowledgments featured in the 1988 publicationremain intact for the present version, as follows: Monique Libmann; Marie-Claire Dupuis, Bernard Barrachin, Andr Cayol, Bernard Fourest; DanielQuèniart, Yves Chelet, Fran ois Cognè.

The basic raw material for a general review of the activity of a largegroup is the actual work of the members of the group considered. This was,of course, the case for the present document and I should like to mention ina far from exhaustive list some of those on whom I relied for assistance:Roland Avet-Flancart, Bernard Barbe, Alain Bardot, Bernard Barrachin,Bernard Bartholmè, Geneviève Beaumont, Claude Birac, Christine Bonnet,Jean Bourgeois, Louis Brègeon, Jacques Brisbois, Jean-Paul Bussac, GerardCadolle, Marc Champ, Yves Chelet, Alain Chesnel, Jean-Pierre Clausner,Francois Cogne, Yvon Cornille, Patrick Cousinou, Bernard Crabol, MichelDelage, Gerard Delettre, Gerard Depond, Yves Droulers, Fran ois Ducamp,Jacques Duco, Marie-Claire Dupuis, Veronique Fauchille, Jean Faure,Christine Feltin, Bernard Fourest, Denis Goetsch, Christian Giroux, Alain

Foreword


IV Elements of nuclear safety

Gouffon, Gilbert Gros, Fran ois Heili, Jean-Yves Henry, Karine Herviou,Jean Jalouneix, Laurent Janot, Martial Jorel, Anne Jouzier, Patrick Jude,Mil ne Julien-Dolias, Jeanne-Marie Lanore, Michel Laverie, Corentin LeDoare, Catherine Lecomte, Joseph Lewi, Alain L'Homme, Marcel Le Meur,Agnes Levret, Daniel Manesse, Jean-Marie Matt i, Jean-Pierre Merle, HenriMetivier, Jean-Luc Milhem, Bagher Mohammadioun, Jean-Claude N not,Jacques Ney, Nicole Parmentier, Dorothee Pattee, Fr d rique Pichereau,Jean-Louis Pierrey, Jean-Claude Puit, Daniel Queniart, Bruno Rague, HenriRoche, Francois Rollinger, Lucien Rousseau, Monique Roy, JacquesSavornin, Jean-Jacques Seveon, Henri Bureau, Pierre Tanguy, NicholasTricot, Serge Vidal-Servat...

Consistency of principles and their expression was once again assuredby Daniel Queniart, who thus made a decisive contribution to the contentsof this text.

The readability of the book, both for French and foreign readers,was vastly improved thanks to the advice and comments of NathalieRutschkowsky.

Philippe Vesseron and Henri Metivier fostered its publication in thisform, whilst Etienne Benoist encouraged its translation into English andRussian.

To Monique Libmann and Monique Roy was entrusted the thanklesstask of rereading.

I am most honored that Mr. Andre-Claude Lacoste, Director of the DSINand Chairman of the Board of Management of the IPSN, has accepted topreface the book.

I thank them all. Needless to say, any errors and imperfections whichmay nevertheless have been overlooked remain my entire responsibility.

Jacques Libmann

PrefaceLike many other industrial safety fields, nuclear safety has developed con-siderably over the last few decades. An essential component of the verynotion of safety is doubtless the ceaseless quest for improvement.

The impact of these developments on organizations is in part related tothe more widespread use of nuclear energy. The prime responsibility ofnuclear operators for the safety of their plants is now clearly acknowledgedby the International Convention on Nuclear Safety, as is the necessity foreach country concerned to constitute a competent safety authority, indepen-dent of organisms promoting nuclear energy. It was only in 1973 that such anuclear safety authority (SCSIN) was set up in France, as a department ofthe ministry of industry. Twenty years later, it became the DSIN (nuclearinstallation safety directorate), responsible to the ministers for industry andfor the environment respectively. For several years now, the running of thisdepartment has been supervised by the Parliamentary Office for Assess-ment of Scientific and Technological Options and the implementation ofnuclear safety statutory provisions is currently being considered.

Technical repercussions have also been extensive, since ideas have con-siderably progressed in France since the initial adoption of the AmericanPWR design, accompanied by its already voluminous package of regulatoryor pararegulatory texts. The EDF and Framatome engineers, together withthose of the safety authority and its technical support structure, the IPSN,had first to become thoroughly acquainted with the basic reactor type beforegradually moving on to a more practical approach, involving the control ofaccidents considered as beyond design basis events in American practiceand even those culminating in core meltdown. Deep thinking along theselines even led to certain previously adopted but inadequately validated cri-teria being called into question, such as the use of fuels with high burnupfractions.

These gradual developments, prompted by know-how advances,whether based on operating feedback or research and development results,are the subject matter of Jacques Libmann's book.


VI Elements of nuclear safety

Throughout his career at the IPSN, Jacques Libmann has personally fol-lowed all the varied details of this progression, as now witnessed by hisbook. Many of you will remember him from their training courses, both inFrance and abroad, when he succeeded in convincing his listeners of thesoundness of the basic safety principles which have gradually been defined.The publication of this book will doubtless widen his audience even furtherand will be beneficial to all those seeking either an introduction to nuclearsafety or further insight into specific aspects of the subject.

The time history approach has the advantage of showing how realimprovements are achieved, sometimes after false starts, by pragmaticresearch where accepted ideas may have to be called into question. Currentdevelopments are aimed beyond national contexts at European, or evenworldwide harmonization of safety practices, together with significantimprovements on the safety level presently attained. This is notably the goalof the future PWR developed by the French and German utilities and plantbuilders (EPR project).

May Jacques Libmann's book assist all those, whether they be designers,operators or safety authority specialists, who, in France or abroad, areresponsible for nuclear plant safety issues!

Andre-Claude LACOSTEDirecteur de la S ret

des installations Nucleaires


Contents

Introduction 1

1. Radioactivity and the biological effects of ionizing radiation.. 5

1.1. Units used 51.2. Natural radioactivity 61.3. Biological effects of ionizing radiation 71.4. Radiation protection principles 16

2. Nuclear safety organization 19

2.1. Nuclear security and safety 202.2. Nuclear safety organization and responsibility sharing 212.3. Safety analysis reports and regulations 232.4. Developments in safety goals 272.5. Safety Culture 28

3. Deterministic safety approach 31

3.1. Determination of specific risks 313.2. Potential risks, residual risks, acceptable risks 333.3. The barriers 353.4. The defense in depth concept 383.5. Quality Control 45

4 . Analysis of operating conditions 47

4.1. Classification of operating conditions 474.2. Definition of design basis operating condition categories 494.3. Choice of operating conditions 504.4. Operating conditions: list and subdivisions 524.5. Operating condition analysis process 554.6. Consideration of internal or external hazards 64

5. Assessment of the radiological consequences of accidents 65

5.1. Quantities of radioactive products involved 66


VIII Elements of nuclear safety

5.2. Release rates 675.3. Transfer and deposit in reactor systems 685.4. Transfer and deposit in buildings 685.5. Leak rate to the outside atmosphere and filtering provisions 695.6. Environmental transport and deposit conditions 695.7 Pathways to man 725.8. Dose conversion factors 725.9. Changes in radiological consequence calculation methods 74

6. An example of accident analysis: LOCA 75

6.1. Physical effects of a large break 726.2. Assumptions adopted in safety analysis 826.3. Acceptability criteria and results 846.4. Evaluation of radiological consequences 856.5. Safety demonstration evolution 90

7. Assessment of safety justifications 91

7.1. Data drawn from operating condition studies 927.2. Checking the number of lines of defense 1057.3. New safety demonstration requirements for the N4 series 108

8. A particular barrier point: the steam generator tubes 113

8.1. Steam generator tube rupture without human intervention 1158.2. Complementary French studies 1178.3. Dealing with the problem for the N4 series 118

9. Internal hazards 121

9.1. Missiles from inside the containment 1229.2. The results of piping breaks 1239.3. Turbogenerator bursting 1249.4. Protection against load dropping 1269.5. Fire protection 1299.6. Internal flooding 132

10. External hazards 135

10.1. Determination of earthquake hazards 13610.2. Protection against aircraft crashes 14110.3. Industrial hazards 14510.4. Floods 14710.5. Protection against other external hazards 149

11. Complementary operating conditions 151

11.1. Origins 15111.2. The position of the safety authorities 152

Contents IX

11.3. Complementary operating conditions 153

12. Probabilistic assessment of an accident sequence 163

12.1. Effects of failures and initial assumptions 16312.2. Chronological list of the elements forming the scenario 16412.3. Required data 16512.4. Assessment results 16612.5. Revision of scenarios and their probabilities 168

13. The accident at Three Mile Island 171

13.1. The accident 17113.2. Causes of the accident 17713.3. Lessons learned from the accident 180

14. The state-oriented approach 183

14.1. Limits of the event-related approach 18314.2. Development of the state-oriented approach 18414.3. First application of the state-oriented approach 18514.4 Generalization of the state-oriented approach 18814.5. Safety panels 189

15. Preparation for the management of severe accidents 191

15.1. Core and vessel degradation 19115.2. The Rasmussen report 19415.3. "Source terms" 19615.4. Severe accident management studies in France 19815.5. Radiological consequences of source term S3

and intervention provisions 20915.6. List of ultimate emergency procedures 21315.7. Summary of procedures 21315.8. Internal Emergency Plan 21415.9. The fourth level of defense in depth 215

16. Special risks associated with criticality accidents 217

16.1. Theoretical scenario 21716.2. A plausible scenario and corrective measures 22016.3. Identification of other dilution scenarios 22116.4. Other criticality accident hazards 22216.5. International information 224

17. Emergency preparedness and IPSN resources 227

17.1. Emergency preparedness 22717.2. Role of the IPSN crisis team 23017.3. Method and tools of the assessment cell 231


X Elements of nuclear safety

17.4. Methods and tools of the radiological consequences cell 23817.5. Conclusion on the method and tools 24017.6. External Emergency Plan 24117.7. Environmental transfer and deposit conditions 242

18. Severe accident research and development work 247

18.1. Thermal hydraulic codes 24818.2. Fission product codes 25018.3. Fission product experiments 25218.4. Corium and containment building behavior studies 25318.5. Other on-going surveys 254

19. Probabilistic safety assessment 257

19.1. Initiation of the studies 25819.2. Aims and organization of the studies 25919.3. Core meltdown probability assessment method 26019.4. Specificities of French studies 26319.5. Results of the 900 PSA survey 26619.6. Results of the 1300 PSA 27219.7. Comparison with studies undertaken abroad 274

20. Applications and development of probabilistic studies. 277

20.1. Use of probabilistic safety studies 27720.2. Development of these studies and tools 28520.3. Probabilistic assessment of radioactive release 28820.4. Conclusions on the probabilistic safety studies 289

21. The Chernobyl accident 291

21.1. The Chernobyl plant and the RBMK reactors 29221.2. The accident 29721.3. The release and its consequences 30021.4. Causes of the accident and lessons learned 31221.5. Future of the other Chernobyl units 31521.6. Lessons drawn in France 31521.7. Information of the general public and communication 31721.8. After Chernobyl 318

22. General operating rules 319

22.1. General operating rules 32022.2. Technical Operating Specifications 32322.3. Initial and periodic tests 33122.4. Emergency operating procedures 335


Contents XI

23. Incident analysis 339

23.1. Incident selection 34123.2. Significant incident analysis methods 34523.3. Case of a repetitive incident 352

24. Detailed analysis of incidents involving human factors 359

24.1. Pressurizer heater damage at Flamanville 2 36024.2. Isolation of pressurizer level sensors at Cruas 2 36624.3. Isolation of pressurizer level sensors at Gravelines 4 36824.4. Analysis and lessons 36924.5. Check on sensor operability 37424.6. General considerations on maintenance activity quality 37424.7. Defense in depth applied to operation 377

25. Preventive maintenance and in-service surveillance 379

25.1. In-service surveillance for large components 37925.2. Preventive maintenance of equipment 38125.3. Steam generators 38225.4. Steam line defects 39025.5. Closure head adapter cracking 392

26. Some French precursors 399

26.1. Incidents 40026.2. Latent nonconformances revealed by inspections 411

27. Periodic safety review 419

27.1. Safety review methodology 42027.2. Fessenheim and Bugey plant safety reviews 42327.3. Safety review of the CP1 and CP2 standardized 900 MWe plant series 430

28. The international dimension 439

28.1. The IAEA standards and guides program 44128.2. The Incident Reporting System 44228.3. French-German comparisons 44428.4. Services proposed by the IAEA 44628.5. Plants of soviet design 450

29. The next generation of reactors 461

29.1. Setting up of French-German safety options 46229.2. Changes in safety objectives 46329.3. Application of the defense in depth concept 46529.4. Preliminary characteristics of the EPR project 46629.5. Illustration of defense in depth provisions 471


XII Elements of nuclear safety

30. Safety considerations on other nuclear installations 473

30.1. Safety organization changes at the CEA 47730.2. General safety approach 47730.3. Safety objectives, notion of acceptability 47930.4. Risk potentials 48230.5. Design bases 48630.6. Safety analysis of an installation 49530.7. Operating safety 50030.8. Plant end of life 50430.9. Conclusion of this chapter 506

Conclusion 507

Appendix A - Basic safety rules 509

A.1 Rules concerning pressurized water reactors (June 1995) 509A.2 Rules concerning basic nuclear installations

other than reactors (June 1995) 511

Appendix B - Regulatory texts related to quality 513

B.1. Order of August, 10,1984 513B.2. Circular of August, 10, 1984 520

Appendix C - French nuclear power plants 533

C.1. Graphite-moderated, gas-cooled reactors (GCR) 533C.2. Heavy water reactor (HWR) 534C.3. fast breeder reactors (FBR) 535C.4. Pressurized water reactor (PWR) 535

Appendix D - Basic Nuclear Installations 539

D.1. Experimental reactors in service 539D.2. Fuel cycle basic nuclear installations 540D.3. Other CEA basic nuclear installations 541D.4. Other nuclear installations 542D.5. Particle accelerators considered as basic nuclear installations 542

Introduction

Nuclear installations present a specific risk in that they all contain, by defin-ition, more or less substantial quantities of radioactive products. These canresult in the exposure of individuals, populations or the environment to ion-izing radiation and the consequences thereof. Nuclear installations for elec-tricity generation fall, of course, in this category.

Other sources of energy also involve risks, but our present purpose isnot to draw comparisons. Moreover, we are well aware of public sensitivityin this respect, where radioactivity effects are associated far more with themilitary explosions of Hiroshima and Nagasaki, and now with Chernobyl,than with natural radioactivity or the benefits of radiotherapy. Our inten-tion here is simply to present the methods and concepts used in the nuclearindustry to ensure a satisfactory safety level for this activity.

Safety results from a set of technical and organizational measures takenat all stages in the life of an installation to ensure that its operation and,more generally speaking, its very existence, present a sufficiently low-levelrisk as to be deemed acceptable for the staff, the general public and the envi-ronment.

So what is actually involved is:• ensuring normal operating conditions which are conducive neither to

excessive exposure of workers nor to release to the environment ofradioactive waste with a high activity level

• incident and accident prevention• limiting the consequences to workers, populations and the environment of

any incidents and accidents which could nevertheless occur.

This gives rise to provisions covering plant operation, but also itsdesign, construction and decommissioning.

It is to be noted that the idea of an acceptable risk is not grounded onclearly defined, absolute criteria, but is rather the result of choices of asociopolitical nature which may evolve over a period of time and may differfrom one country to another, depending on local economic conditions. In

2 Elements of nuclear safety

this context, it is the role of the technicians to propose, but the final decisionis based on political assessments integrating other contingencies.

For any given installation, the process begins with identification of thenature and extent of the risks entailed. Only after this has been done canmethods for ensuring safety be defined and analyzed.

Several decades have now elapsed since nuclear plant construction andoperation began in France. The reactors of the first type used in France,which were natural uranium-fuelled, graphite-moderated and CO2-cooled,have now all been shut down. Several of the installations currently in ser-vice were built to earlier standards, at least as regards technological devel-opments and safety issues.

Most of the pressurized water reactors presently operating in Francewere designed on the basis of the American plants under construction at theend of the sixties and the beginning of the seventies, at a time when worldexperience in this type of undertaking was limited.

It is consequently not surprising that, although the basic principlesdefined at the outset of a project are not easily called into question, safetycriteria approaches and analysis methods have considerably altered over theperiod of time involved.

Now that substantial experience has been acquired, we are, or course,able to check whether the principles underlying the initial approach are stillsatisfactory and to compare actual plant behavior with the estimates madebeforehand. The world's two most dramatic nuclear accidents, Three MileIsland in 1979 and Chernobyl in 1986, figure largely in this analyticalprocess, without however overshadowing the many minor difficulties to becontended with in the daily running of an installation.

Rather than describe current approaches to safety from a static statusangle, we have opted for a partly historical presentation which reveals moreclearly their dynamic and evolutive character. We shall base most of thispresentation on the pressurized water reactors operated in France, althoughmany other examples will also be used.

In this document, we shall consider successively:• the deterministic approach, which is the main safety approach method• safety analysis methods based on accident analysis• the enhancement of these methods by development of the probabilistic

safety approach and preparation for the management of particularlysevere accident situations

• operating feedback• subsequent evolution paths and the international dimension.

Each subject will be illustrated with a number of examples.


Introduction 3

General topics such as the human factor or the importance of quality,could have been dealt with in separate chapters, but we have preferred, onthe contrary, to avoid isolating them so that they can be referred to in themany contexts directly concerned by them.

Finally, we shall insofar as possible base our discussion of the elementsof this approach on general aspects, applicable to all nuclear installations,for it will be seen that if responses in each case must be adapted to specificpotential risks, the same types of questions re-occur and have to be system-atically examined.

In order to situate the purpose of nuclear safety, we shall summarize inan introductory chapter the biological effects of radiation together with themain basic principles of radiation protection. This should enable the readerto better comprehend the extent of the consequences of the phenomena dis-cussed.

Similarly, safety awareness and practice involve a sharing of responsi-bilities defined by regulatory texts. In order to conserve the technical andphilosophical rather than administrative disposition we have adopted, thesecond chapter will describe the organizational principles governing rela-tions between the safety partners. This will give rise to reflections on thedetermination of "acceptable" risks and on what is now referred to as SafetyCulture, to which we trust the present document will contribute.

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1 Radioactivity andthe biological effectsof ionizing radiation

At the International Conference on the Safety of Nuclear Energy: Strategyfor the Future, held in Vienna (Austria) on September 2-6, 1991, it wasdeemed advisable to present the basic biological effects of radioactivity toenable at least overall understanding, with a view to prevention, of possibleradiological consequences of abnormal situations and of the basic principlesof radiation protection. It is on the same grounds that the present workbegins with a chapter on this subject. The text is adapted from the confer-ence document prepared by an international working party entrusted withpresenting the basic principles of safe use of nuclear energy. It draws exten-sively on the conclusions formulated by the organizations competent on thisquestion, the International Commission on Radiological Protection (ICRP)and notably its publication No. 60, but also on certain more recent observa-tions on the populations exposed following the Chernobyl disaster.

1.1. Units usedThe radioactivity unit is the becquerel (Bq), equal to 1 disintegration per sec-ond. As this unit is extremely small, multiplying prefixes are oftenemployed: mega (M) = 106, giga (G) = 109 or tera (T) = 1012.

The former unit is the curie (Ci), equal to 3.7 1010 disintegrations per sec-ond or becquerels and historically defined as the activity of one gram ofradium 226. Since this unit is relatively large, minimizing prefixes wereused: micro ( ) = 10-6, nano (n) = 10-9, pico (p) = 10-12.

Two units are used to express radiation effects on the human body. Thegray (Gy) expresses the energy deposited in matter by a particle or radia-tion. 1 gray = 1 joule per kilo of material. It is the SI absorbed dose unit,replacing the former rad (1 Gy = 100 rad).



The shorter the path of each energy depositing particle, the greater willbe the potential noxiousness of the absorbed dose.

For comparison purposes, quality factors are used to express absorbeddoses of any type in terms of dose equivalents for reference X and radia-tion effects. This quality factor is, by definition, 1 for electrons and X andradiation, 20 for alpha particles and heavy nuclei and from 5 to 20 for neu-trons and protons. The dose equivalent is expressed in sievert (Sv). The for-mer unit is the rem (1 Sv = 100 rem).

Each tissue and organ has a specific sensitivity to cancer risks. For 100cancers observed following homogeneous external exposure, there are 12lung cancers, 5 breast cancers and 1 skin cancer, for instance. So a weighting(or sensitivity) factor is introduced to transpose the dose equivalent into aneffective dose.

In the event of internal contamination, irradiation continues until theradioelement responsible has been removed. In this case, we calculate thedose commitment due to the contamination, extrapolated over the next 50years. In accordance with current regulations, this calculation is performedat the time of contamination. Effective and committed doses are alsoexpressed in sievert.

In accordance with regulatory practice, the term "dose" shall generallyrefer in what follows to an effective dose.

The relationship between a becquerel and the corresponding gray orsievert number depends on the particle or radiation energy and its mode ofinteraction with the substance considered and, in the case of internal conta-mination, on the length of time the radioelement stays inside the organism.

1.2. Natural radioactivitySince the origin of man, humanity has been exposed to a wide spectrum ofnatural ionizing radiation. This exposure is due to cosmic radiation, gammaradiation from the earth and radioactive products naturally present in thehuman body, originating from food and water (mainly lead 210 and potassi-um 40) and from inhalation (mainly radon 222).

The annual dose due to these natural sources averaged over all popula-tions of the globe is between 2 and 3 millisievert (mSv), but varies between 1and 5 mSv according to the place considered. Under average conditions, thecontributions of the cosmic rays, the gamma rays from the ground andingested products are approximately the same and equal to 0.3 to 0.4 mSv.So the fraction due to radon inhalation is much larger, representing up to40% of this natural irradiation. It varies considerably according to place,dwellings, living conditions.



• Other experience (operating experience of basic nuclear facilities, "standard prac-tice") has enabled the processes or codes used to be validated; in such event, itshall be systematically determined that the assumptions are correct and fall withinthe scope of such processes or codes.

• Insofar as it is possible to make properly any necessary changes, the facility com-missioning tests may be sufficient to confirm the achieved results; the number ofcases in this category shall remain sufficiently limited so that possible changes nec-essary at an advanced stage of construction remain limited.

• The studies for which there are no technical control means independent of thoseused and a list of which is included as such with all necessary support in the safetyreport.

In these three cases, the procedures for the follow up of the studies provide evi-dence, with all necessary support, of the extent of the areas in which the special con-trol measures are not implemented.

Finally, studies aiming only at improving assessment of the available toleranceswith respect to situations not allowed for in the design are subject to adapted proce-dures; in such event, the use of simplified confirmation calculations is no longerrequired but they shall be used insofar as possible.

Article 15

For certain activities initiated before filing of the basic nuclear facility constructionpermit application, and in particular for preliminary plan activities, the Order's pro-visions may be adapted or not applied entirely insofar as no action difficult toreverse under the decisions made for the safety of the future facility can result there-from.

Article 16

(mentioned as a reminder).

Article 17

This article takes into account the diversity of basic nuclear facilities (power reactors,research reactors, fuel enrichment, manufacturing and reprocessing plants, wastestorage centers, accelerators, irradiators, laboratories, etc.), the diversity of the phas-es in which they now stand and the time necessary for the establishment, if need be,of new measures.

The Order is obviously not applicable to activities completed on the date of pub-lication of the Order in the Official Journal. It applies however as provided in thisarticle to future and continuing activities.

Article 18

Requests for waiver of the Order will be handled by the Head of the SCSIN who willconsult, insofar as need be, the competent experts or groups of experts, in particularthe standing groups responsible for studying the technical aspects of the safety ofnuclear facilities.

Appendix B - Regulatory texts related to quality 531

Article 19

Like the other provisions of the regulation covering basic nuclear facilities, the orderapplies in the strict sense only to the basic nuclear facilities operated or to be operat-ed in France.

However, a supplier may happen to perform, or make others perform, in France,a significant part of the activities devoted to design or construction of a nuclear facil-ity located or to be located abroad. If the involved supplier so requests, measureswill be taken to enable provisions of the order enforceable in France to be appliedunder the same conditions as if the nuclear facility were to be installed in France,considering the supplier as an owner, as defined in the Order, during the design andconstruction period. The Head of the SCSIN shall then be instructed to enforce theOrder.


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