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COM (79)173
Vol.1979/0075

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COMMISSION OFTHE EUROPEAN COMMUNITIES
COM (79)173final
Brussels .9thApril 1979
TECHNOLOGICAL PROBLEMS OF NUCLEAR SAFETY
*
SÉCOND PROGRESS REPORT
\
(Communication from the Commission tothe Council )
/•' '""\/ ..■-> \i 'Â
b:.Ç-' . ^
V:
■v--'-. ■/
COM(79)173final

Technological problems ofnuclear safety
Second progress report
This report was drawn uppursuant toitem 8ofthe Council
Resolution of22July 1975 onthe technological problems
ofnuclear safety .

TABLE OFCONTENTS
Page N°
Introduction 2
Point 1.Safety ofreactors that have reached ahigh
level ofindustrial development (Water reactors ) 2
1.1 .Activities aimed atharmonizing safety
techniques andstandardizing ecpiipment 2
1.1.1 .Working Group N°1-Light-water reactor
safety ("Methodology ,criteria ,codes and
standards ")* 2
1.1.1.1 .Work programme -General outline 2
1.1.1.2 .Specific activities 5
1.1.2 .Safety analyses ofspecific projects 12
1.1.2.1 .GKN (Dodewaard Nuclear Power Station ) 12
1.1.2.2 .BR–2materials testing reaotor (CEN/SCK fMol)13
1.1.2.3 .Doel IIIandTihange IInuclear power stations 14
1.1.3 .Environmental andother implications 14
1.2 .Activities aimed atcoordinating research
programmes 17
1.2.1 .Working Group W°2activities 17
1.2.2 .Working group onsafety aspects ofsteel
components innuclear installations 21
Point 2.Safety ofsodium-cooled fast reactors (LMFBR ) 23
2.1.Working Group onFast Reactors Safety
(SWG) 23
2.2.Working Group onCodes andStandards (WGCS ) 25

Point 3.Activities inthefields ofplutonium recycling ,
radioactive –waste disposal andnuclear power-station
decommissioning 27
3.1.Plutonium recycling inlight –water reactors 27
3.2.Management and storage ofradioaotive waste 28
3.3.Decommissioning ofnuclear power stations 29
χ
X X
>«'•.'
ANNEX 1-Working Group N°1-Objectives and membership
Working Group N°2-Objectives and membership
ANNEX 2-Working Group onPast Reactor Safety -Objective
and membership
Working Group onCodes and Standards –
and membershipObjective

Introduction
This report covers the period from 1January 1977 to30June 1978 ?
itisasequel tothereport onthe same subject (reference COM(77 )168
final )which covered theperiod from July 1975 to31December 1976 .
1.SAFETY OF REACTORS THAT HA VE REACHED AHIGH LEVEL OF INDUSTRIAL
DEVELOPMENT (Water reactors )
1.1,Activities aimed atharmonizing safety techniques and standardizing
equipment
1.1*1 .Working Croup N°1–Light-Water reactor safety ("Methodology ,
criteria ,codes and standards ")•
Working Group N° 1,the objective ofwhich isdescribed inAnnex 1,
continued its work with the assistance ofad–hoc sub-groups and
bymeans ofstudy contracts .
1.1.1.1 .Work programme –General outline
Inview ofthe continuous developments inthis field ,the
previously defined subjeots were reviewed and supplemented and
thepriorities reassessed .Inconsultation with the Working
Group ,the Commission then modified the work Programme inthe
following manner t

-3-
Tasks tobeundertaken inthe future ,onthe basis ofcurrent
work :
.Exchange ofinformation onapplied safety rules ,criteria ,
codes and standards and continuation ofthe attempts to
reach acertain degree ofharmonization bymutual infor­
mation .
.Identification ofthe general safety criteria ,codes and
standards andoftheapproaches tospecific LWR**safety
problems applicable and/orunder development inthe various
member countries .
.Classification ofthe areas ofdivergence and those of
common requirements ;identification ofreasons fordiffe­
rences (industrial ,admini strftti ve,geographic ,etc.)and
evaluation ofpriorities .
.Suggestion offormulations toovercome thepoints indispute .
.Consultation ondrafts' ofnational rules ,codes ,etc.,in
member countries ofthe European Community .
.Examination ofthe need for uniform criteria ,codes ,stan­
dards ,etc.,and the respective ranges ofapplicability .
.Examination ofcodes ,guides and standards ,etc.,drawn up
byinternational organizations ,etc.,with respect to
applicability inCommunity member countries and any sub­
sequent amendments required .
11:eras to fce added tothelist oftopics initially
drawn up(1973),some ofwhich are tobedealt with asa
^ matter ofpriority :
-safety problems associated with siting (inaddition to
those already studied )
*)
LWR :Light-Water Reactor

-protection ofnuclear power plants against fire ;
-anticipated transients without scram (ATWS )-
-m-service inspection ;
-overpressuri zation oftheprimary circuit ;
technical safety aspects ofdecommissioning .
Items included intheinitial list onwhich work istobe
started inthe very near future :
–reliability andrisk analysis ,theuseofrisk concepts in
safety assessments
–comparison ofnational practices from thepoint ofview ofthe
fault andaccident conditions that determine thedesign ofa
nuclear power plant asreflected insafety reports
-study onimprovement ofexchanges oftechnical information
onincidents having asignificant effect onnuclear safety ,
butlimiting itself atpresent toastatus report onthe
requirements specified bytheregulatory authorities .
Theterms ofreference ofWorking Group N°1were adapted to
therevised work programme bytheinsertion oftheprovision
that thenext stage should start with theselective formula­
tions ,according tonecessity andinanagreed order ofprio­
rity ,ofrecommendations within themeaning ofarticle 124of
theEuratom Treaty ,Such .recommendations arenon–mandatory acts
andsubsequently itwasthought appropriate tofollow aprac­
tice similar tonon-mandatory national orinternational rules ,
guides ,standards ,etc.,andtoassociate utilities and ven­
dors (UNIPEDE ,UIJICE and CEEP)*inthedrafting ofthese
recommendations ,with thefinal input left totheauthorities
and/orsafety andcontrol organizations .
International Union ofProducers andDistributors ofElectrical
Energy
Union ofIndustries ofthe European Community
European Centre forPublic Enterprise

-5-
Some topics were indicated which maylend themselves tore­
commendations :
1.Protection ofnuclear power plants against seismic effects
2.Emergency power supplies
3.Protection ofnuclear power plants against aircraft crash
4.Parameters used intheevaluation oftheradiological con­
sequences ofaloss-of-coolant accident andfuel-handling
accidents .
1.1.1.2 .Specific activities
a)Comparison ofthepractices andcriteria used forthepro­
tection ofnuclear power plants andanalysis ofaccident
conditions .
i
-Protection ofnuclear power plant against seismic effects .
Arevision of "thesynthesis report isbeing prepared .The
report lists existing national criteria ,codes andstan­
dards toprotect nuclear power plants against seismic
effects anddiscusses points ofconvergence anddivergence
inEuropean practices incomparison with USpractice .It
may serve asabasis toformulate recommendations ofthe
Commission oftheEuropean Communities (Art .124of
Euratom Treaty ).(Seesub-section 1.1.1.1 .above ).
-Protection ofnuclear power stations against aircraft
crashes .
Theposition ofsome ofthemember countries haschanged
asaresult ofincreased application ofprobabilistic
considerations .Further arrangements with airforces have
been concluded insome countries .Theexisting synthesi sre
port hasbeenadapted .Comparative studies ofmethods forcalcu
lating protection ofstructures against penetration and
formaking probabilistic calculations areunder consi­
deration .
"•Protection ofnuclear power plants against theeffects of
external explosions

I
ι-6-
The general view inthe Member States isthat anuclear
power plant must take into account "both detonation and
deflagration and inthecase ofdetonation –type explosions
theexclusion-area concept isapplied .
Insome countries nuclear power plants aregenerally de­
signed towithstand theeffects ofanexternal explosion ,
i.e. ,they aredesigned for apeak overpressure of0.3
barofthe incident pressure wave or0.45 barreflected
overpressure .Inother countries theexplosion hazard is
included inthedesign basis ofthenuclear power station
onacase -by-case basis .
Asynthesis report onthis item isinpreparation .
Itwill bepossible touse the results ofthe research
programme proposed bytheCommission (seesub-section
1.2.10 )for the continuation ofthe work .
Protection ofnuclear power plants against floods .
Therevised synthesis report onprotection ofnuclear
power plants against flooding hasbeen submitted tothe
working group forcomments .
Guides onthedesign andprotection ofnuclear power plants
against floods are actually under development orunder
discussion insome ofthe member countries .Current Com­
munity criteria call forprotection against flood levels .
Ageneral objective istoexclude from further considera­
tion individual events orcombined events ofasimilar
nature (such asdifferent flood-producing events )which
could lead tounacceptable consequences with aprobability
lower than 10^perannum .
Mechanical andthermohydraulic aspects oftheloss-of -
coolant accident (LOCA ).
Thepractices applied invarious member countries inorder
toassess themechanical andthermohydraulic consequences

-7-
ofaLOCA onthereactor internals ,theprimary components
andthe containment were compared ,with theassistance of
external consultants ,onthebasis ofinformation made
available within theworking group .Thefinal report is
still incourse ofpreparation .
Radiologi calconsequences ofaloss-of-coolant accident
(LOCA ).
Afirst draft synthesis report onthis matter waspresen­
tedtothemembers ofthat working group .This report
groups and compares inanorderly form foreasy reference
alltheinformation communicated sofar inreply toa
questionnaire andfrom afewother readily available
sources .
Far-reaching divergences areencountered with regard to
-atmospheric dispersal ;those result from the useof
different models andmeteorological inputs andrender
aquantitative comparison very difficult .Comments and
corrections from working group members will bediscussed
byexperts inanadhocsubgroup andarevised version of
thesynthesis report will beissued .
Fuel-handl ingaccidents .
Alist hasbeen compiled ofthepractices applied inthe
various Member States inassessment oftheconsetjuences of
afuel-handling accident .Thebasic information andafirst
condensed survey have been supplied bythesecretariat of
theworking group andtheintention istoprepare draft
recommendations with aview topossible future harmonizar -
tion ofexisting practices andcriteria .

-8-
-Turbine missiles and coolant pump flywheel integrity .
Theinvestigations inthefields ofturbine explosion and
primary pump flywheel rupture were putinabeyance ,since
there was nobasis for comparison either because oflack
oftechnical substance intheinformation (administrative
measures tosolve the problem )orbecause ofthe incompa­
rability ofvarious technical designs .
The available information has been collated anddistri­
buted .
-Spectrum ofsteamline breaks inside andoutside contain­
ment .
Thecollation ofinformation ;;onthevarious possible steam-
line break accidents ,i.e. :
BWR steamline break outside containment
PWR steamline break outside containment
PWR steamline break inside containment ,
can beconsidered asfinalized within the working group .
Synthesis reports are incourse ofpreparation .
-Protection ofnuclear power plants against loss ofelectric
power supply :
Guides inthis field are being developed insome ofthe
Member States ;inothers USNRC *Regulatory Guides are
being applied .Asynthesis report based mainly oncurrent
practice has been completed .Thedesirability andfeasibi­
lity offormulating recommendations isnow under considera­
tion .(see sub-section above ).
*).. .United States Nuclear Regulatory Commission

-9-
b)Study and comparison oftherules andstandards used for
site selection andforthedesign andconstruction ofLWR
nuclear power stations .
Several topics are atpresent being dealt with under study
contracts andarebriefly outlined below .
-Comparison ofsafety practices andcriteria applied inthe
site selection and evaluation .
Discussions onandcompilation ofsiting criteria andsite
evaluation practices fornuclear power plants inmember
countries andrelated emergency planning andprocedures
were started .The discussion ofthis item will continue and
includes siting considerations near borderlines and indense­
lypopulated areas .Asynthesis report will bedrawn upand
should constitute anup-to-date outline ofthe siting ,
policy fornuclear power plants inCommunity .countries
from ahealth andsafety standpoint .
-Reactor-coolant pressure boundary .
Acorrelation study oncriteria ,codes andstandards
applied inthedesign ,construction andsafety assessment
ofprimary boundary components isbeing prepared .Itis
planned tofinalize thework inthelatter half of1978 .
Adetailed comparison ofEuropean codes applied inthedesign
*
andconstruction ofpressure components with theASME Code
wasprepared with theassistance oftheUSNRC inafirst
draft ,which isatpresent incourse ofrevision .
\
*
American Society ofMechanical Engineers

-10-
-Containment structures and engineered safeguards .
The methods and procedures applied incontainment -leak
testing are being investigated byvarious European plant
operators who already have experience inthe application
ofperiodic leak-testing procedures .Afirst report will
bereleased atthe end of 1978 .
The treatment ofsome other topics ,such ascontrol room,
reactor ventilation system ,radioactive waste treatment
systems ,service water systems and ultimate heat sink,reac­
tor core and vessel internals ,will beinitiated during the
period 1978-80 .
c)Use ofrisk concept insafety analysis
Astart has been made with the consideration offundamen­
tal concepts inthe development ofcriteria ,standards ,
guides etc.Ithas been decided toinclude the methodolo­
gies ofrisk analysis inthis context .
Aquestionnaire has recently been sent out toworking group
members inorder toobtain ageneral view ofcurrent prac­
tice inthe risk analysis field orofthe alternative prac­
tices applied atpresent inreactor safety .(See also sub­
section 1.1.3 c).
d)Notification ofthe Commission bythe Member States of
draft laws orregulatipns concerning the safety ofnuclear
installations pursuant toitem 6ofthe Council Resolution
of22July 1975 .
Nodrafts were forwarded tothe Commission during the period
covered bythis report .

-11-
e)Development ofnational and international technical rules
(criteria ,codes ,standards )
-Asystematically organized "Catalogue andclassification
oftechnical safety standards ,rules and regulations for
nuclear power reactors and nuclear fuel cycle facilities "
inexistence orbeing developed inboth member and non-
member countries was duly prepared and wasfirst published
inSeptember 1975 .The intention was toupdate the cata­
logue periodically .Afirst revision appeared insummer
1977 (doc .EUR 5849 ).
-National draft technical rules ,codes and standards of
general interest tothe working group are being forwarded
totheCommission forconsultation ofthe working groupj
approximately 20 caSes have been dealt with sofar.
f)The Commission maintains close contacts with international
andnational bodies such asIAEA-NuSS ,IS0/TC85,OECD /NEA,
US-NRC ,KTA,and DIN*tokeep track ofon-going activities .
Inparticular ,the Commission follows closely the IAEA's
efforts inthefield ofnuclear safety codes andguides
under the NuSS programme .These codes andguides are
circulated tothe members ofWorking Group N° 1inorder to
IAEA-NuSS :International Atomic Energy Agency -Nuclear Safety Standards
IS0/TC85 :International Standards Organization /Technical Committee 85
OECD/NEA :Organization for Economic Cooperation and Development /Nuclear
Energy Agency
KTA :Kerntechnischer Ausschuss
DIN sDeutsches Institut fur Normung

-12-
avoid duplication andsignificant discrepancies inthis
field .Commission staff participate regularly inthose
meetings ofTechnical Review Committees CTRC )andthe
Senior Advisory Group (SAG )which deal with subjects re­
lating toWGN° 1'sworking scheme .
1.1.2 .Safety analyses ofspecific projects
These safety analyses enable theexperts brought together bythe
Commission tocompare their views ongeneral andonspecific
problems concerning safety ,which makes for apragmatic approach
totheproblems arising intheharmonization ofsafety criteria
andrules andsupplements theactions implemented byWorking
Group N° 1.
1.1.2.1 .GKN (Dodewaard Nuclear Power Station )
In1973 ,theDutch authorities asked theCommission ofthe
European Communities forexpert advice ontheconsequences
ofanincrease oftheoutput oftheDodewaard Nuclear Power
Station ;inparticular ,theperformance oftheemergency core-
cooling system (ECCS )hadtobeevaluated .
Themain subjects ofthis study were :
-theadequacy oftheemergency core-cooling system ,ex­
pressed interms ofthereactor core 'sthermal response to
aloss-of-coolant accident ;
-stress analysis ofthereactor internals during aloss-of -
coolant accident ;
-theproposed modified design ofthe ECCS .
Asregards the first twosubjects ,theCommunity experts
should notperform their owncalculations buttheoperator 's
calculations should bechecked against thecriteria inuse .
Thereliability oftheproposed modified design ofthe ECCS
should bestudied by"engineering judgment "and/orbymeans
ofasimple reliability analysis .

-13-
Theinformation needed tocomplete thestudy wasrecently pro­
vided bytheoperator andthefinal report setting outthecon­
clusions andanumber ofrecommendations will becompleted in
thesummer of1978 .
1.1.2.2 .BR-2 materials testing reactor (CEN/SCK,Mol ).
In1976 ,theBelgian authorities requested theCommission to
carry out asafety study ontheBR-2 experimental reactor .This
wasprompted bythe fact that deterioration hadbeen observed
intheberyllium matrix ofthereactor core .TheBelgian
authorities wished toobtain anopinion onthe specific prob­
lempresented bythe state oftheberyllium matrix andonthe
more general problem ofcontinuing theoperation ofthis reac­
torfrom theviewpoints ofsafety andofprotecting thehealth
oftheworkers andthegeneral public inthe surrounding area .
In1977 ,theCommission departments concerned set upanadviso­
rygroup ofexperts from various European Community bodies
specializing inproblems ofnuclear safety ,towhich ,atthe
request oftheBelgian authorities ,twoAmerican experts on
beryllium metallurgy were added .During the second half of
1977 ,these experts studied alarge number ofdocuments drawn
upbytheoperators oftheBR-2 reactor ,mainly concerning the
progression development ofthedamage observed intheberyl­
lium structures ,themodifications andimprovements made tothe
installation andthevarious operational incidents and acci­
dents undergone bythereactor since itsentry into service .
InApril 1978 ,thegroup ofexperts mettogether with there­
presentatives oftheCommi ssiort andanobserver sent bythe
Belgian safety authorities . ' *•
After this meeting ,asafety assessment report wasdrawn up
andwasforwarded totheBelgian authorities inJune 1978 .

14-
1.1.2.3 .Ooel III and Tihange IInuclear power stations
Both ofthese power stations areequipped with 941-MWe PWRs *
ofpractically identical technical design andtheir schedules
for construction and entry into service coincide towithin a
few months .Asafety assessment ofboth power stations was re­
quested from the Commission ofthe European Communities bythe
Belgian Governmant in1976 .During 1977,the competent de­
partments ofthe Commission enlisted the help ofanumber of
external experts tocarry outthis assessment .
Most ofthe safety reports onthe Ooel III and Tihange IIpower
stations were provided over aperiod from June 1977toMarch
1978,sothat the actual expert assessment ,which was totake
about one year ,only began inMarch 1978 .Byagreement with
the Belgian authorities ,theactivity ofthe committee ofex­
perts called together bythe Commission would berestricted to
studying only apart ofthe safety reports .
Only those points ofthe study which are ofdefinite Community
interest were taken with bythe committee ofexperts -in
particular ,certain site-related aspects such asseismology ,
safety and safeguard systems ,the control system ,the emergency
electric power supply ,the study ofaccidents ,and systems for
protection against accidents ofexternal origin .These are,in
fact ,theprincipal subjects which are currently being studied
for regulatory and standardization purposes byWorking Group
N° 1.
1.1.3 .Environmental and other implications
a)Limits and conditions for normal effluent release
InApril 1977,ameeting organized bythe Commission with re­
presentatives ofthe competent authorities andthe group of
experts appointed under Article 37ofthe Euratom Treaty was
held todiscuss thegenerally appli cable limits fof *effluent control
*Pressunzed-Water Reactor

-15-
andoperational discharge applied inMember States tonuclear
installations .The aim ofthe meeting wastocreate abetter
mutual understanding inthis field with aview ultimately to
harmonizing thedifferent approaches used inthe various coun-
. *tries toimplement the ICRP principle of"aslowasreasonably
achievable ."
Inaddition tothe information concerning the European Com­
munity countries engaged innuclear energy activity ,informa­
tion concerning practice inSwitzerland and inUSA was con­
sidered .
The following conclusions can bedrawn from the meeting .
Inaccordance with the recommendations ofICRP,all countries
considered above apply the "aslow asreasonably achievable "
principle .Tothis end some countries incorporate environmen­
tal radiological limits i.nlegislation ,directives ,recommen­
dations orguidelines (limits far below the ICRP
dose limitsjto beassociated specifically with radioactive dis­
charges ;other countries have incorporated limits onthe maxi­
mum permissible activity indischarges .Other countries again
have notexplicitly stated such generally applicable limits
for effluent control .
Inthe fixing ofdischarge limits forindividual nuclear in­
stallations ,however ,acase-by-case analysis isalways carried
out.The above-ment ioned general lyapplicable limits then serve
asmaxima within which theoperational limits have tobefixed ,
taking into account the best current technology forthe type of
plant inquestion .
Although noradiological limits applied specifically toeffluent
control inthe various countries exceed 10% ofthe ICRP dose
limits ,they vary over anorder ofmagnitude .Any attempt to
compare therelative stringency ofthese different values can,
International Commission onRadiological Protection

-16-
however ,Lead tomisunderstandings ifnoaccount istaken of
corresponding differences inthe range ofconditions towhich
the values are intended toapply .
Abetter approach for the purpose ofgrasping what constitutes
the best current practice indischarge control would appear
tobecomparison ofoperational limits applied tothe same
type ofnuclear installations .This isparticularly true as
regards nuclear power stations equipped with light-water reac­
tors ,ofwhich asignificant number ofstations are already in
operation orplanned .Moreover ,operational limits can be
adapted toimprovements intechnology more easily than limits
laid down informal legislation .
Itcan beconcluded that ,although considerable differences
are found inthe generally applicable limits applied today
inthe Member States and some other countries for effluent
control from nuclear installations ,increasing uniformity can
beobserved inrespect of:
-the quantities specified inthe operational limits ;
-the ways inwhich these limits are derived ,expressed and
implemented .
b)The existing list oflicensing procedures forthe construction
and operation ofnuclear power plant within the Member States
(Report EUR 5284 )has been updated ,including now supervision
and control ,and published (1978 Edition ). Aseparate report
onthe authorization procedure for containers and conditions
governing transport ofradioactive substances within the Mem­
ber States has been issued (EUR 5663 ).
c)The progrssive use ofquantitative methods insafety assessments
involves access toreliability data onnuclear plant components
aswell asthe development and improvement oftheanalytical
5

-17-
methods used .Inthe light ofthese considerations ,theCommis­
sion continued itsefforts tosecure cooperation between natio­
nalreliability data systems (exchange ofdata ,analysis of
codes ,terminology ).Inaddition ,thevalidation study of
probabilistic transient analysis bycomparison with histori­
caldata from anoperating nuclear power plant went further
ahead .From this study aconcluding report mayemerge inthe
summer of1978 .
Inorder "tocompare risks from nuclear installations andthose
from conventional activities ,astudy hasbeen undertaken in
which thefactors that determine existing risk levels inthe
non-nuclear sector have been examined ,aswell astheextent
oftheefforts made tofind ways ofreducing these risks .
The conclusions ofthis study will befinalized before the
endof1978 .-J• -
1.2 .Activities aimed atcoordinating research programmes
1.2.1 .Working Group N°2(onlight-water reactor safety research pro­
jects *)concentrated mainly onthefollowing areas 1
a)Theupdating ofthe"index "ofresearch projects concerning the
safety ofwater reactors ;thefourth edition wasdistributed
inAugust 1977 andcontains information onapproximately 500
projects classified under 19main headings .
TheCommission forwards copies oftheCommunity index asinput
fortheOECD(NEA)-IEA version andacts asaliaison point for
theMember States oftheCommunity .Close liaison onthetwo
systems ismaintained ,thus ensuring themaximum dissemination
atanytime ofthecurrent projects ineach particular area
ofnuclear safety research .
See Annex 1 fortheterms ofreference ofthis Group
e

-18-
!
b)Continous on-going activ.ity istaking place ,inconjuntion with
Working Group N° 1,topromote -inselected fields and accor­
ding toapre-established order ofpriority -continuous con­
sultation ,coordination and cooperation between the specialized
agencies andinstitutes ofthe Member States and,where appro­
priate ,those ofthe non-member countries .
c)Having established aprocedure for rapid and accurate circula­
tion ofinformation oncurrent research projects ,Working Group
N°2hasgiven considerable attention tothetask ofassessing
key areas where further knowledge isstill required .Its ob­
ject isthus topromote cooperation between Community specia­
lized institutes inthese key areas and toformulate programmes
ofwork onspecific topics where useful work can beperformed
asagreed tobenecessary byits members .
After long and extensive discussions ,three such key areas have
been identified inwhich itisconsidered necessary toimprove
and consolidate existing technical knowledge .
These are :
-Emergency core-cooling (ECC)phenomena following aloss-of -
coolant accident (LOCA ).
-The protection ofnuclear installations against external ex­
plosive gas clouds .
-The escape ofradioactive fission products following apostu­
lated reactor accident andtheir dispersion inthe atmosphere .
These three topics have been studied indetail ateight meetings
ofexpert sub-groups .
Asaresult ,afive-year indirect action programme ofresearch
work covering these areas was formulated and waspresented to
the Council and the other Community institutions onApril
19th 1978*.
C0M(78 )166 final

-19-
This programme istobepartly funded bythe Commission and is
intended tobecomplementary toexisting and proposed program­
mes ofreactor safety research in:
Community Member States ;
the Joint Research Centre ofthe Commission ;
countries with advanced nuclear technology outside the Community .
-Inthefirst area ,the assessment ofthe necessary effective­
ness ofthe emergency core-cooling system isbased largely on
computer codes whose validities are dependent onexperimental
studies covering arange from basic research onphysical
phenomena through single-effect tests tolarge-scale integral
experiments modelling the reactor geometry insome detail .
The proposed Community programme isconcerned mainly with the
study ofseparate effects inthe field oftwo-phase rewetting
phenomena .The proposed work will fill gaps inexisting know­
ledge ,assist inthe development ofpredictive models and
codes and aid the interpretation oflarge-scale integral ex­
periments .
-Inthe second area ,thepossibility ofrelease tothe atmos­
phere from industrial areas of .hydrocarbon vapour and gas
clouds may constitute anexplosion hazard toalocal nuclear
power plant .This could necessitate changes tothe design of
the nuclear plant inorder towithstand theeffects ofsuch
events .Inorder todetermine the required protection ,abet­
ter understanding ofthe phenomena ofgas cloud explosions
isrequired .The proposed Community programme will there­
fore cover three fields ,namely :
theinitial production anddispersion ofclouds ;
the important parameters involved inthepossible explosion
ofthe cloud ;
therelationship between agenerated pressure wave and the
response ofbuilding structures .

-20-
-Knowledge ofthethird area isanecessary input tothe overall
risk analysis ofanuclear plant ,asthis dispersion will have
animportant influence onthepotential consequential damage
tothegeneral public andthe environment following postula­
ted accidents ofvery lowprobability ofoccurence .Anim­
portant objective for Europe isanagreed method ofassessing
the overall risk tonuclear plant ,particularly relevant in
the case ofthose sited close tonational frontiers .Community
work here will include assessment and comparison ofexisting
dispersion models ,some important experimental validation of
such models and monitoring ofspecific meteorological condi­
tions .
The intention isthat work onthese topics should becarried
out inparallel ,and oncollaborative lines ,atanumber of
organizations within tihe Community .Inthe case ofexperimen­
tal work ,thetotal cost tothe Community can beconsiderably
reduced bymaking use ofhigh-capital -cost experimental faci­
lities already existing inCommunity Member States .
The overall aim ofthis programme istosupply industry and
governmental organizations with thebasic information neces­
sary toconsolidate the safe operation and assessment ofther­
mal water reactors inuse and under construction today -that
is,those types ofnuclear plant providing the bulk ofnuclear
electricity generation atthe present time .
The proposed programme will beimplemented under contracts .
Inthe execution ofthis programme the Commission will be
advised bythe already existing Advisory Committee onPro­
gramme Management forreactor safety research inprogress at
the Ispra Joint Research Centre .This Committee will be
further assisted byWorking Group N°2anditsrelevant
technical sub-group .

-21-
1.2.2 .Working group onsafety aspects ofsteel components innuclear
instal lations
This working group isorganized jointly bytheCommission ofthe
European Communities andtheOECD /NEA (CSNI ).Itsactivities during
thereference period were confined t&theselected areas offrac­
ture mechanics ,welding and heat treatment ,andnon-destructive
testing .Itisnotthe intention toexclude problems relating to
anyparticular reactor type ,although thegreater part ofthe
working group 'sactivities concern water reactors ,simply because
these accounted formost ofthesafety research being carried out
atpresent inthe Commission andOECD member countries .
During thepast year ,considerable progress wasachieved inthe
field offracture mechanics -asevidenced inparticular byin­
creased confidence intheuseofsmall test-pieces toestimate K^c
and encouraging developments intheuse forthis purpose ofsmall
test-pieces ofthe Charpy Vnotch type .Thelatter technique is
especially suitable forinspecting reactor vessels .However ,major
uncertainties persist with regard tothesignificance ofthe
growth ofstable cracks ,both intest-pieces andinactual struc­
tures .Forabetter understanding ofthese phenomena tests onlar­
ge-scale models andstruotures would berequired .
TheWorking Group considered that more attention should bepaid
to :
-special aspects offractures asafunction oftheyield point {
-theapplication ofelasto-plastic fracture mechanics tostruc­
tures such aswelds ,comprising materials with very different
hardnesses ;
-theapplication ofprobabilistic methods tofracture mechanics .
K■critical value oftheBtress concentration ,lo

-22-
Inthe field ofwelding andheat treatment ,tneforking
Group concentrated onproblems arising intherepair ofwelds .
Byusing theresults provided byvarious countries ,theWorking
Group found that controlling thetemperature during thewelding
operation wasofdecisive importance asregards thestructural
composition oftheheat-affected zone andthefiller metal .On
theother hand ,itisnotsomuch thelevel ofinput heat which
exercises aninfluence ,butrather thewelding method itself ,the
rate ofsuccessive passes andtheshape oftheweld .
Itwasfound that ,byoptimizing thepreheating temperature ,the
welding parameters andstress relief ,annealing could beimproved .
Inthefield ofnon-destructive testing ,theWorking Group concen­
trated itsactivities ontheprogramme coordinated bythePlate
Inspection Steering Committee (PISC),
Attheend of1975 ,the USPressure Vessel Research Council
shipped three material test blocks with artificially introduced
flaws ,available inthe USHeavy Section Steel Technology Pro­
gramme (HSST ),toEurope' inorder togive European non-destruc­
tive testing institutions theopportunity totest their equip­
*
ment (primarily ultrasonic methods ).
Theparticipating European institutions agreed toperform the
tests inaccordance with the ASME XICode soastomake the
results comparable tothe UStest results .These institutions
were ,however ,free toapply national requirements inaddition .
About 27European institutions participated inthenon-destruc­
tive testing (NDT )programme ,which wasconcluded attheend
ofMay 1978 .After the completion oftheNDTprogramme ,destruc­
tive tests will beperformed todefine more precisely the sizes ,
position ,andnature ofthecontained defects .Themost impor­
tant part ofthedestructive programme ,aswell astheevalua­
tion ofresults will beperformed attheJoint Research Centre ,
Ispra ,with contributions from various European institutes .
See also COM (77)168

-23-
2.SAFETY OFSODIUM-COOLED FAST REACTORS (LMFBR )
2.1 .Working Group onFast Reactors Safety (SWG)
During theperiod inquestion ,theSafety Working Group ,thestudy
group onWhole –Core Accident Codes andthestudy group onContainment
Loading andResponse actively continued their work .
2.1.1 .The fourth updating ofthe inventory ofR+Dactivities inthe
field ofsafety was completed .
2.1.2 .The R+Dprogrammes were continued andtheexperience acquired with
thedemonstration reactors inoperation wasdiscussed .
2.1.3 .Topics ofspecial interest asregards fast-reactor safety formed
the subject oftalks presented byspecialists onanumber ofocca­
sions .Among the topics dealt with were :
newdevelopments inthe field ofearthquake knowledge ;
methods applied inthe assessment ofreliability ;
in-pile experiments onthe fuel-failure mode .
2.1 .A.Atthe request ofthe Fast Reactor Coordinating Committee ,the
group drew upadocument onthe keysubjects inthefield of
safety that could beuseful forthepurpose ofdefining its
future programme .Theproblems associated with theremoval of
post-accident heat received special attention from thegroup .In
this specific field ,thegroup drew upadetailed inventory ofthe
activities inprogress intheMember States .This document will
shortly beforwarded toagroup ofexperts which will have the
task ofdetermining whether alltheproblems arecovered bythe
current programmes orwhether further projects should berecom­
mended .
2.1.5 .Safety criteria andprovisional technical recommendations inres­
pect ofprimary reactivity accidents were drawn upandsubmitted
tothe Fast Reactor Coordinating Committee .These results repre­
sent animportant step ,which wasmade possible byprodigious
efforts onthepart ofalltheparticipants .
SeaAnnex 2forthe terras ofreference oftheSafety Working Group and
these study groups .

-24-
The establishment ofsafety criteria ;andoftechnical recommenda­
tions forthe other categories ofaccident isatask towhich the
group accorded high priority .
2.1.6 .Study Group onWhole Core Accident Codes (WAC)
The WAC Study Group continued the comparative calculations .A
report onaloss-of-coolant accident waspublished ;ithas been
 presented atone conference andwill bepresented atanother .
The calculations performed for atransient overpower accident
(TOP)have reached their final stage and areport isbeing drawn
up;publication isscheduled for 1979 .Since 1977,American ex­
perts have been attending the meetings devoted todiscussing the
results ofcomparative calculations .
Considerable progress has been made inthe development ofthe
European Accident Code,which isanother main task ofthe WAC
group .
The JRC,Ispra ,haselaborated apilot version ofamodular code
which enables modules developed bydifferent organizations tobe
easily exchanged .
2.1.7 .Study Group onContainment Loading and Response (CONT )
The CONT Study Group has continued todiscuss the work inprogress
atIspra onthe development andverification ofcalculation codes
forapplication totheevaluation ofsevere accident effects on
fast-reactor vessels .
Inaddition ,the CONT Group hasparticipated indrawing upapro­
gramme ontheeffect ofmolten fuel-sodium interactions inindi­
vidual assemblies .This programme ,which isbeing implemented at
the Ispra JRC,was planned with considerable care asacomplement
tothe work inprogress inthenational establishments .
Another part ofthe group 'swork isitsparticipation inthe
APRICOT programme .This isaproject initiated bytheUnited
*
Reaktortagung (Hannover ,April 1978 )
ENS-ANS International Meeting onNuclear Power Reactor Safety
(Brussels ,October 1978).

-25-
States forthecomparison ofexisting calculation codes forthe
evaluation ofaccident effects onafast-reactor vessel .
Finally ,thegroup hashaddiscussions onspecial problems which
areofconsiderable importance asregards assessing theresponse
ofareactor vessel ;this involves dealing with unsteady flow
across perforated plates andthetransient dynamics ofatwo-
phase vapor bubble .
2.2.Working Group onCodes andStandards (WGCS )*
At "theplenary meetings andnumerous experts meetings ,theWorking
Group reviewed thepresent state ofknowledge inthefield with
wnich itisconcerned }inDecember 1977 »theresults were presented
totheFast Reactor Coordinating Committee (PRCC ),which examined and
approved the report .
Asregards future work ,the FRCC expressed anopinion requesting
theGroup tomake aneffort toarrive ataconsensus ofopinion
ontheevaluation ofpoints ofdivergence inmethodology andtoen­
courage projects that would facilitate such aconsensus .
Basing itswork onthetechnical data provided bytheWGCS ,thesecre­
tariat drew upaproposal foraresearch programme (indirect action )
onLKFBR codes andstandards which will bepresented totheCommission
inJuly 1978 .
Theresults obtained bytheWGCS relate tothefour following fields :
(a)Manufacturing standards andquality control
"Code qualite ",adocument prepared byTechnicatome forthecon–
truction ofSuper-Phenix ,served asabasis forthestudies *In
thelight ofthis document ,over thirty distinct manufacturing
operations were chosen *Theinter-relationship between activities
such astests onthematerial purohased ,preparation ofthe
See Annex 2 fortheterms ofreference ofthis Group .

work ,execution ofthe work andtests after completion ofthe '
work waspinpointed .for each operation .Thepractice adopted by
each Member Stattf for each activity was determined .
Subsequently ,cases inwhich practices were identical indetail ,
were ascertained,as well cases inwhich they were similar and had
the same objective and cases inwhich they differed significantly .
Inthe majority ofcases ,itwas found that thenational practices
examined were identical orsimilar inform .Onanumber of im­
portant points ,however ,significant differences exist .
(b)Structural analysis ofequipment and design calculations
Itwas established that the Member States did not possess speci­
fic national codes that had been specially developed for LMFBR
components .Similarly ,there was agreement among theexperts
that itwas the components subjected tohigh temperatures that
presented thegreatest difficulty .
Priority was thus accorded tothis field .The only design rules
published inthe field ofstructural analysis were those inthe
ASME Code Case 1592*.
However ,since many ofthese rules should beused with caution
inrespect ofhigh temperatures and since certain procedures are
difficult toapply ,this code has not been adopted inits en­
tirety and additional clauses orrevisions have been incorporated
which define other methods and design criteria .
<c)Materials
The selection ofspecifications for materials for the construc­
tion ofspecial LMFBR components comes within afield which is
particularly influenced bynon-LMFBR experience inthe countries
concerned .
I
! '
i
I ■. .
1 Τ"
i American Society forMechanical Engineers <ASME ).

Tnetask undertaken inthis field consists instudying the manner
inwhich thematerials are chosen and approved inthe Community
Member States forspecific applications and what range of
materials iscurrently used oriscoming into use for LMFBRs
inthe Community .
Nine materials were identified .One ofthem,type 316steel ,was
then selected for more detailed studies .Itturned out that there
were nine different versions oftype 316steel currently inuse
andthat these versions could have very different mechanical
properties .
Cd)Classification ofcomponents
The classification isthe method used toensure that the measures
taken tomake failures improbable are aligned tothe consequences
ofsuch failures . |
The most advanced document inthis field was adopted asabasis
fordiscussion ;ithad been specially drawn upforthe construc­
tion ofthe Super-Phenix reactor and was modified bythe Group
both tosimplify itand tomake itapplicable toamore extensive
range ofLMFBR designs .
ACTIVITIES INTHE FIELDS OF PLUTONIUM RECYCLING ,RADIOACTIVE-WASTE
DISPOSAL AND NUCLEAR POWER-STATION DECOMMISSIONING .
.1.Plutonium recycling inlight-water reactors
The nuclear safety projects described indocument C0M(77)168 with
reference tothe indirect-action programme onplutonium recycling
inLWR power stations were practically all put inhand in1977 under
contracts .They cover mainly the following fields :
.study ofthestatic and dynamic behaviour ofplutonium -fuel led
LWR power stations ;
.study ofthe impact onthe environment ofplutonium transport
under normal conditions and accident conditions ;
.global study ofthe impact onthe environment ofplutonium re­
cycling inlight-water reactors (development prospect forthe
end ofcentury ).

-28-
.study oft+te impact onthe environment ofplutom um-fuel fabrica­
tion plants ,covering normal operation andpossible accidents .
Some results ofthe studies onthe environment are already available
and have been communicated tothe Member States (Article 13ofthe
Euratom Treaty );further results will becommunicated during 1978
and 1979 ,while safety studies relating tothe behaviour ofpower
stations will becompleted bymid-1979 atthe latest .
The technical details ofthese contracts :technical specifications
and -incertain cases ,the main conclusions were presented intwo
1 : ____2annual reports covering the periods 1975-1976 and 1976-1977 .
Two technical meetings confined tocontractors and the members of
the Advisory Committee onProgramme Management were held todis­
cuss the presentation and the status ofthe work carried out bythe
contractors inthe three fields listed above .
3.2.Management and storage ofradioactive waste
The work carried out aspart ofthefirst five-year indirect-action
programme onthe management and storage ofradioactive waste and
mentioned inthe preceding progress report has been continued .Itis
mainly concerned with thepractical development ofeffective solutions
toenable the radioactive waste tobeisolated from the environment
for long periods after suitable treatment .
Apart from the development ofmethods for conditioning the various
types ofwaste and preparatory work onthe construction ofthefirst
experimental storage installations ,the evaluation oftheproperties
offormations suitable for the siting ofsuch installations was con-
tinued^as welIasthegeneral safety studies bymeans ofriskanalysis and
Programme ofresearch and development onplutonium recycling inlight-
water reactors ,EUR 5780 d/e/f/i/n,1977.
\
Programme ofresearch and development onplutonium recycling inlight-
water reactors ,EUR 6002 e,1978 .
Indirect-action programme onthe management and storage ofradioactive
waste ,Annual progress report ,1976,EUR 5749

-29-
themodelling ofradionuclide migration towards the biosphere ".A
number ofmeetings took place onthis subject ,particularly the semi­
narjointly organized bythe Nuclear Energy Agency andthe Commission
inJune 1977 ontheanalysis ofrisks associated with thedischarge
ofwaste andthat onthein-situ heat transfer experiments atHar­
well inSeptember 1977 .The compilation ofproblems presented bythe
management ofradioactive waste for which solutions would not be
found within the framework ofcurrent legal ,administrative and
financial provisions has been continued ;astudy under contract has
been carried out onthevarious national nuclear legislations inthe
Community countries andtheinternational conventions ofsignificance
towaste management .
3.3.Decommissioning ofnuclear power stations
The decommissioning ofnuclear power stations means their disposition
under conditions that ensure the necessary safety after they have
been taken out ofservice .
On17May 1977,the Council approved ,aspart ofthe Community pro-
2gramme ofaction onenvironment ,theprinciple ofaproject inthe
field ofnuclear power station decommissioning ,tobecarried out
along thefollowing lines with theassistance ofnational experts :
(a)assessment ofthe foreseeable quantities ofradioactive waste of
different categories arising from the decommissioning ofnuclear
instal lations ;
(b)comparison ofthe specialized techniques that exist orare being
developed inthefield ofdecommissioning with aview toapprai­
sing them both from the aspect oftheprotection ofman andhis
environment and from that ofthe economy .Onthebasis ofthis
assessment ,determination ofthe measures tobetaken ;
Indirect-action programme onthe management andstorage ofradioactive
waste ,Annual progress report ,1977,EUR,tobepublished .
2OJNoC139of13June 1977

-30-
(c)comparison ofthe studies and available experience concerning
decommissioning operations ,aswell asthe various conceivable
methods forfinal storage ofthe radioactive waste arising from
these operations ;
(d)determination ofcertain guiding principles inrespect ofthe
design and operation ofnuclear installations with the aim
offacilitating their subsequent decommissioning ;
Ce)determination ,inrespect ofthe decommissioning ofnuclear in­
stallations ,ofguiding principles around which aCommunity
policy inthis field could beformulated .
The work carried out onthe basis ofthis plan ofaction involved
three meetings ofthe group ofnational experts and enabled the
 Commission topresent acommunication tothe Council .This com­
munication comprises onthe one hand asummary ofthe results ob­
tained sofar,covering items (b)and (c)andthefirst stage ofitem
(a)ofthe abovement ioned plan ofaction ;and,ontheother hand ^,
aproposal for afive-year research and development programme (indi­
rect action )tobeapproved bythe Council .The programme isaimed
atthe joint development ofasystem ofmanagement ofdisused nuclear
power stations and ofradioactive waste arising from their dismant­
ling soastoprovide ,atthedifferent stages ,optimum protection
ofthe population and the environment .Inaddition tothe develop­
ment ofspecialized techniques ,the programme includes the con­
tinuation ofthose projects inthe abovement ioned plan which are
inthe long-term category (Projects (a),(d),and (e)).
C0M(78 )167 final

ANNEX 1
Working Group N°1-Objectives andmembership
Theobjective ofWorking Group N°1istocompare thepractices ,methodo­
logies ,criteria ,codes andstandards applied intheMember States ,for
thepurpose ofenabling the Commission subsequently toformulate recom­
mendations andtoplace before theCouncil proposals judiciously geared
toCommunity requirements .This Working Group wassetupatthe endof
1972 ;itiscomposed ofdelegates from the Member States who are
appointed by :
–theauthorities and/ortheassociated bodies responsible fornuclear
safety ,authorizations ,supervision andinspection ;
-theelectricity-producing bodies ,through theintermediary ofUNIPEDE 1;
-thedistributing bodies ,through theintermediary ofUNICE 2and CEEP^.
Under certain conditions ,Swedish experts have been participating inthe
meetings since the end of1976 .
Working Group If02–Objectives and membership
Theobjectives ofWorking Group N°2concern theroutine exchange of
information andconsultations onthenational and Community (JRC)
research programmes onnuclear safety .This Working Party was set upat
the end of1972 .
Itiscomposed ofrepresentatives from the Member States who are
appointed by :
–theauthorities and/orassociated bodies responsible fornuclear
safety ;
International Union ofProducers andDistributors ofElectrical Qiergy .
2Union ofIndustries ofthe European .Community .
European Centre forPublic Enterprise .

2
theadministrations responsible forthemanagement ofresearch program­
mes financed bypublic funds ;
theelectricity-producing bodies ,through theintermediary ofUNIPEDEj
thedistributing bodies ,through theintermediary ofUNICE andCEEP .

ν
ANTTEX 2
Working :Group onFast Reactor Safety -Objective andmembership
Theobjective ofthis Working Group ,which was setupin1971 within the
Fast Reactor Coordinating Committee ,isthe exchange ofinformation on
current research anddevelopment programmes ,thediscussion of pro­
blems ofparticular interest asregards fast reactor safety and thepro­
posal ofmeasures tobetaken tosolve them ,andthepreparation ofcom­
mon safety criteria .
Twostudy groups areassigned thetask ofstudying ,evaluating and compar -
ring the calculation codes :
TheStudy Group onWhole –Core Accident Codes (WAC)
TheStudy Group onContainment Loading andResponse (CONT )
TheWorking Group iscomposed ofrepresentatives from theMember States
appointed bythevarious bodies involved inthedevelopment andconstruo -
tion offast reactors :
-thegovernment departments responsible forresearch anddevelopment
programmes ;
-therepresentatives ofresearch centres ;
-theapproval authorities orassociated bodies ;
-the constructors ;
-theelectricity producers .
Working Group onCodes and Standards –Objective and membership
This Group was setupin1974 and itsmembership issimilar tothat of
theWorking Group onFast Reactor Safety .Itsmain objeotive istodraw
upaninventory oftheexisting codes andstandards that canbeapplied
tofast reactors with theaimofidentifying thefields inwhich addi­
tional knowledge isdesirable .