ML110030901

Exhibit Pwa 00014, Kamiar Jamali, Use of Risk Measures in Design and Licensing of Future Reactors

ML110030901
Person / Time
Site:	Pilgrim
Issue date:	01/03/2011
From:	Jamali K Elsevier, US Dept of Energy, Office of Nuclear Energy
To:	Atomic Safety and Licensing Board Panel
SECY RAS
Shared Package
ML110030897	List: ML110030898 ML110030901 ML110030903 ML110030907 ML110030908 ML110030909 ML110030910 ML110030911 ML110600894 ML110600896 ML110600897 ML110600899 ML110600900
References
RAS 19369, 50-293-LR, ASLBP 06-848-02-LR, PWA 00014
Download: ML110030901 (7)

Text

PWA00014 Pilgrim LR Proceeding SO-293-LR, 06-848-02-LR Kamiar Jamaili - PRA's Subject to Uncertainties Co n ten t!l- I i'St -g, .ava i I BIble .at Sde.n ceDI ~

ReHabi l ity Enginee,.-ng and System Safety j.o u r n a l h o m .e p.a g .e : 'W'Ww.e l:S<e vl e r .oo m / l oca t e/ res. s.

Use of r isk measures in design and li censing of fu ure r eactors K amiar Jamali Unit.a:::l Srars nq,aRm rnt of ~. Off or ofllucmr .f.nagy, Jooo J'~ .~ I!; W ammg;DD. DC 2lJ.s.as. ,jJ _~

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1 ~ Intn xl:uct:ion rl.s k- ba.sec::'I regula 'lD ry con.struct. Som e 0 f 't b e d is ti n g ui.sh _in.g featu res bet:wee:n 'the: 'tv.'O are a l.so d i..scus.s ed in 't bi.s pape;L Proba.b ilis t ic ri.sk .a.sse.s.s me:n t ( PM ) results .and in.sig h ts have T he: n uc:le.ar in dustry aJ.s o has u .seCI PRA techni q u e.s extE:n s ive:l y h e l ped ID imp ro ve nu d e.a.r po.......er pla n t s a fe ty a n d o pe:ra ti o naJ "Wi t b b en e:fi,d a l res ul ts.. i ncl ud ing ion 'the desig n o f advanced o r n e:xib iJ ity f o r m o r e t ha.n .3 0 yea.~ . T hi.s s u a:e:s.s has k!d ,to i_n c m.a.sed evol u tio n a ry nud ea r re.actD~ . These ben e fi ts a r e:.. in part.. l1!.I.ated u se o f P RAs by t h e n 'uc:l e.a:r i nd u st:Jy a n d reg ulato ry a u t ho rit ie.s ID t h.e f .ar:t 't h at 'these s .arn.e u .se:rs can a l.so con trol a n d lim.it 'the:

1NO rldv.ri d e.. W hj Ie t.h is t:r1!n d is large ly pcsi tive.. t h e re can be: infl u e nce o 'f th e in(D m p l ete sa fet y info rmat io n t h a:t i.s p rovi ded pot e n t ia l n e g.a:t ive con seq uen ces t h a 't ha ve n o t b een \<'Vi d e ly thorou g h th e r esu I ts o f the: P RA a lo n e.. Factors 't h a 't are u s u a lly no't d i.scus.sed in. re lated Ii terat:u re:. "Wi th :so m ,e e::x£I!P 't i o ns (e.. g... ( 1 1)" full y accoun ted for in a PRA m ,o de:1 but are g e rma.ne to 'the:

I t "Was becau s e o f t hi.s pos iti ve (D J]t ributio n 1D s afe ty that the (D nsid e r a ti o n o f adequacy 0 f s afety fe.a.tu res fo r a s pe cific i.ss\E o r U S N:u c Je.ar Regu la 'ln ty Com m is s io n ( NRC ) g radu a ll y re:fi ned the::i r aa::i.d en t scenario may i n d :u de:: m .agn itu de:s of re evan t .sa..fety o r ig inaJ dete rmin_istic- ba.ser::) J]u d eB,r .sa..fety ~Jat:io[15 b y ma.rgi n.s. i n CDr poa rati o n 0 f d e f e n.se i.n doq::r t h. poten t ia l f o r c o rrec-i n c o r po rat:i n g 't he u se o f ri.sk in fo rma.'t i o n a n d in.sig h t s "Wi't hi n a tive 0 r com pe;nsa 'l Dry attio n.s. degree o f c o n.se:rvati.s m in a na lysi.s.

ri.sk-info rrned fr.a.m ev."CJ rk . Ris k- info rmed regulatio n .s for the a nd m .an y o'the r s.. Th e very sam ,e P RA in formatio n.. h owever. w h,e n c urren t f.l.eet of op e-ra ting l ight - "Wa'l Er reacto r s ( LW Rs ) are d e fi ned us ed t o (D mpl y "Wi t h -we.11-in't e:n t i on ed l'1!g ulato ry JX>l i cie:s a n d t hro u g h a com b inatio n 0 f rule- m a king a nd pub Licat i o n o f a pproac hes can le.ad to som e un desirab le (D ns eq u e nces.. Som e o 'f 10VW!r-t i e r docu men ts, s u c h as regu la 'l D ry g ui d es o r NRC's the u n desi_rab Ie (D ns equ e n CE.5 in a pp Ucatio n.s i_n volv i.ng fu ture e n d o r se::m ,e n t o f certa in n uclear in d u s try docu m ents. Thus. in a re.actD r'S a re a lso d i.scussed 'b el ow ~

ri.sk-i n Jo rrned fra m ewor k., ri.sk info rm.a d o n a n d insig b ts s u p ~ e PRAs prov iCI e bot h q u a li tati ve a n d q u a n 'titative: info rma tio n _

m ,e n t t h e trad i tio na l dete rm in is t ic a p proach e.s a n d f o rm a part o f Recent: 't re n d s in t he: de:v e kJ pm e n t: o f n,eN ris k - rela ted a p pro ach es..

t h e 0 ve:r.a.11 .sa..fe:ty ca.se ("Wb.ic h i.s s o m eti m es refe rred ID as the "W he:th .er 't h ey are per fo rm ed b y 'the: regu laID ry staff. nuclear safety ba.s is ) f o r a n 'u d e.ar pla nt. The Com mi.ssio n has aJ.so cal ~ ind ustty~ 0 r o 'the r dom estic o r i_n te:rna tio n a l 'bod i es.. are tl:JWards f o r i.nc::re.a.seCI u se o f PRA tech no logy in a ll regu laID ry m..atte:~ in a heavi e r e mph.a.si.s in u se o f q u a n t ita:t ive P RA res'ul ts ( in't e n:.h.ange-m a n _n e r t ha.t compl e men ts NRC's p redo mina n t ly dete rministic: a bl y re.f erred 'to as '" r is k m easu res'" i.n t.hi.s paper ).. I t i.s ""'e.U- know n a p p roach,e.s "Wi th.i n the (D nfin.e.s o f a ri.sk- i n_fo rm ed as 0 pposed ID a tha t q ua n 't i tat:ive results o f PRAs, in pa.rt:icul.ar~ a re: s u 'bj ect 't o var io us types o f un ce-:rt ain ties.. Examp le.s of 't hese 'u nce:rta..i nd e.s incl ud e pro b a b ilisti c q u a n 't ifi.c .a:ti o n o f s ing l e a lX1 (D mmon--

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magn itudes 0 f SOU r<l! terms. r.ul ionud ide release and transpert. The Com m i£sion' 5 1005 PRA I'IlIicy Statement 0 n use 0 f PRII atmospheric dispersio n, biological elfucts o f rad ia tion, dose metbads in nudear regu laIDry activ ities [31. w hich was issued in calcu lations. and many others. U nlike d<!l:erministic una.rtain t ies t he aFtP.rmath of the ID mpletio n o f PRIIs for all o""rating nudear related to physical phenomena (e.g.. neu tron ics:, t hermal - hydrau- plan ts in aa:ordan<J! w i t h the Ind ividua l Pla nt Exami nat ions li cs~ PRII una.rtaint ies aR! not R!.ad ily reducib le in most Generic letter l41 states. in (>art:

instances. Uncertai nties associatm w ith physical phenomena The use o fPRII techno logy.ba uld be increased in aU R!gu latory can 0 FtP.n be redu md by tests:, experi ments:, 0 ""rati ng experience matter. ID the exb!n t sup perl:l!d by t he state-af-the-art in PRII on actual o r p rototype designs. o r imp rovements: in analytical methods and data and in a manner th.a t complements: the models or ID mputat iona l ca pab il ities. Despi te th.is well- known limitatio n. if quant itative PRA resu lts: are u sed in the ID ntext o f N:RC's determi n istic ap proach and su !>p<lrts t he N:RC.

tr.ld i tio nal defense-i n-<lepth p hiJosop by.

risk .aa:eptan<l! criteria ( ce., w hen t h.e y are com pared agai nst a set of threshold val ues estab I ished by either the i ndustry or the The Cam mission's safety goals for nuclear power pla nts and regu laID r). it wou Id be di Ffic ul t to IDunt er the una mbiguous but subsidiary numerical obj ectives are to be used w ith potential ly m.islead i ng or i nID rrocl: message that is de~ vered appropriate consideration o f u ncertain*ties in maki ng by such a number-based pro<l!55 ; i..e.., implying that a design is regu latory judgmen ts: an the nem for proposing and bac k-unaa:eptable o r unsafe because it d id not meet a particu la r risk- fit ti.ng new generic requj remen ~s 0 n n udear pav.",r pla nt based numeri cal t h reshold (labeled as a risk .aa:eptan<l! cri teri on). lia.nsees.

An i m pertan t issue that is outs ide of the SID pe of th is paper.

b ut is wo rthy o f detailed d iscussions of its own, is t ha t the Th.e Commission a(>p rm"ed th.e staff's W hi te Paper on Risk-introduction and i m(>act 0 f PRIIs: i nthe design and ~ cens:i ng stilges rnfo rmed and Performance-Based Regu Iation in March 1900 [51, fo r a fu ture reactor is by and large different from the way t hat w hjc h provided defi ni t ions of risk- in.formed and risk-based risk- informed regulations have been a(>plim to existing reactor*. regu Latio ns. It R!it erates t hat the Commissio n does not endorse Cu rrently oper.lting R!iLClD rs h.ad a demrministically estab ~shed an a(>p roach t hat is r isk-basm, w herein decisio n-ma king is solely lia msing basis (w hic h ind uded t he plant's safety basis) before based an the numerical resul ts o f a r isk assessment.

pla nt-speci fi co r generi c risk information and insights: were made Regulatory Gu ide 1.174 16 1 est;Ib lished the framewor k for avai lable th rough PRIIs. T he PRIIs: generally con firmed t hat the risk-in fo rmed regu lations in applications r<gam ing making pla nt-origi na l determ.i nistic ap proach to design and Iia.nsi ng was speci fic cha nges to t he I i<J!osi ng basis. Its ap proach ensures t hat conservative (e.g.. plants couJd respend ID some accident numerical PRA resul ts would not fo rm the sole basis for maki ng scenari os in ma nners t hat were not cred ited in the determ.ini£tic nudear .afety do::i£ions by Iisti ng five key p ri nc ip les (Le., meeti ng ana lyses) and further identified changes that couJd improve pla nt cu r R!l1t regu lations lw hich are prima ril y deterministiq .

design or oper.ltiona l safely. Meeti ng the deterministic req uire- m.eeting defense-i n"4lepth p ri nci pies, ma in tai ni ng . uffident ments meant t hat implementatio n of their atb!ndant provis ions safely ma rgi n, keepi ng i ncreases in risk. malJ, and per forman<l!

embodied w it hin the IDnceptso f defense in dept h. safety ma rgi ns. m.o nitored) that have ID be met for a risk- i nform ed ap proach_

conservati ve assum ptio ns and ana lyses. qua l i Iy assurance, and Clearl y, c urren t regu lations are by and large based 0 n detenn i-nu merous other factors ( many of w hich are not R!.ad ily measur- njstic req u irements. A key pertion of the section an SID pe (Section able w i t hin a PRII model) created a safety cushion or marg in t hat 1.4 ) states:

proto::ted t hese plants from u ncertainties. i nclud ing those from The N:RC has chosen a mare restri c tive pol icy that wou Id

" un know n unk noWIlS" (fo r w hich a eu phemism can be "emergi ng permj t o nly s mall i ncreases in risk, and then only when it is safety issu es~ as d iscuss:ed in Section 1 ~ On the other hand, PRA reasanab Iy assu red. among other thj ngs, t hatsuffid entdere:nse models h.ave to R!ly on realistic inputs: to ellS ure t hat risk in depth and suffic ient ma rgi ns are mai ntai ned. Thjs pel.iq is significant insights are not obscu red by arti fic ia Uy biased resul ts:

adopted because 0 f uncertai nties and to acIDun t for the fact derill'ed from the ap p ~ ca ti o n 0 f uneven ID llServatism5. Themfore, t hat safety issues continue ID emerge regardi.ng design, great caR! must be exercised in bringi ng PRAs into t he design construction, and 0 perational matter. notwithstandi ng the p racess to ensu re t hat t he fu ndamental pi Uars of determ.i ni£tic ma turi ly of t he nudear power ind ustry. Th. .... fac1D rs suggest safety as:su rance process ment ioned above are not u nd u Iy t hat nuclear pcwer R!.aclD rs shou Id operate rou ti nely on Iy at a com pro mised. Thus, fo r futu re reactors. 'Use 0 f risk in fo rroation prudent marg i n above adequate protection. The safety goal ca n hav e a far more sign i ficant im (>iLct on the safety basis of the subsidiary objectives are used as an examp le of such a prudent pla nt, ind udi ng the petentia l ID dri ve some key design decisio ns.

ma rgi n.

The int ent of risk- in form ed R!gu lations is to ensu re t hei r influence is pas itive in safety t radeof f do::isions. The clause abou t ID nti nual emergen<l! of safely issues for pLants w ith many years of operating experien<J! is an altern.ative way to state the ID ncern regardi ng u na.rta int ies about the

" unk nown unkn owns~ that are a mare significant con<J!rn for f uture R!.aclD r designs.

N:RC publ ished t he Safely Goals Pol icy Staternen to n Aug ust B, One R!iL5on th.a t RI!gu latory Gu ide 1.174 h.as worked weU in 1986 [l ~ W hile t he tex t o f t his I'll I icy statl!!Tlent does use the app~ catio n is that it was in tended for operati ng plan ts w i t h a p h laSe "aca.pt.m Ie risk," the tit le and the rest of the d iscuss io ns primarily determjnistic ~cens i ng basis already in place, w hjch were ca reful to avo id the use of th.e Q,Janti tati, ,,, Health means t hat the pla nts ",,,,re al ready deten:nined to be safe: before Objectives ( Q:HOs) o f pro mpt fatalities ( pr s) and latent cancer app ly ing the resul ts of pla nt- speci fic PRAs.

fata lities { [Lr s) as R!gu la tory risk--.aa::eptan<l! criteria. In o th.e r ri.nally, N'otel o f Chapt er 19 o f the Standam Review Pla n (SRP )

wo ms. the selection of the tl'rm.i no logy of " safely goals- was very 17 1 states that t he Q:H:Qwsu rregates 0 f OJ re Damage FR!Q uency delibe ra1E. An impertant attribu te of t he calcu latio n of pla nt- ( CDf) and large Release Frequency (lRF) are goals and not specific PFs and las for IDm paroon w ith the dua l QHOs: is t hat regu laID ry requ i rements.

both are by ne<l!55 ity " integrar" qua nti t ies t hat are deri,"ed from Th.e key cond usio n from the: above is t hat the N:RC the ID nt ribu tio ns of all aa:ident scenari os t hat are considered in Commissioners have not endorsed a " risk-based- app rnach to the pla nt-specific PRA model. regu la tio n because of the u ncertainties in qua ntitative R!S ul ts: o f

PRAs.. Th.ese u na>rtainties are la rge for cu rrently 0 perati ng nudear [n add ition, t he Commission rejected the use o f lE - 5Jy r of pla nts, pa:rticu larly in the SCI~lI ed l.e!J'eI 2 and level 3 PRlls. The macID r operatio n as a CDP goal for advancul d esigru in. SECY-fact that t he large una>rtaint ies in the estimal25 of p mbab ilities 9O~ 16 1. 12 ~ and its SlUvt T his rej ection sho u Id b e exam i ned for h ardwa~ failu~ and human erro[S. and understanding and m geth.e r w it h a seri es of Co mmiss ion Pc I icy Statemen*ts 0 n p robabi I istic qua nti fic<rtio n o f occu r mnce of some physical ~ ulabon 0 f advan.ced reacID [s. The last in the sedes pub I ished p he:no mena in PRAs o f cu rrently 0 perating reactors seem less so in OcID'ber of 2008 lUI stal25:

because of repeated reuse shou Id no t be O!Ierlooke(L T realment of una>rtaint ies in severe acddent prog~ si on and d elineatio n has T he Commission expttt:s. as a minimum, at least the same always 'been 1i m ited in r is k assessments performed m d<lte, even degree 0 f protection of the I!Ilvi ron ment aoo pub I ic healt h and in t he stoo ies th<1l: went the fu rthest in suc h. a nalyses, such as safety a nd the m mmon defense and secu rity that is requi red N'UREG- 1150 1 8~ . for cu r rent gene ratio n l ig ht-water reactors. l'u rtherm ore, the Another irn portant consideratio n, also related to t he general Commissio n expects that advan.ced reactors w ill pmv idl!

c<rll>gory of u ncertai nties, is t he issue of stab>-O f~th e-art: in PRII en hanced margi ns 0 f safety a nd/ o r use si m p I iEied. inhe rent:,

methods and data. Th is is a n issue for risk model i ng o f all reactor passive. or o therinnO!lative means m acmmplish their safety d esigns as a ll uCled t o above, a nd it is esped aUy so for d esigns and secu ri*ty functions. The in.m rpo ratio n o f en.hanced safety t hat pri mari Iy rely o n pa:ss ive safety fu nctions perform ed by ma rgi IlS may he ll' offset the e ffects 0 f added uncertai nties in safel¥-related Systems. Structur es, and Com po nents (SSCs) and t he PRII mo del a nd/Or in acddent ana lyses aris ing from the d igital systems (e.g.. in i nstru mentatio n and control I&<C). The nOllei ty of advanced reac1Dr designs. l Elsewhere other attri-cu r~nt stab>-Of-the;Lrt does not permit a high qua lity model ing b utes o f advanced designs are d escribed as: rei iable and less for ~I iabil it y evaluatio ns fo r these systems. rn parti c ula r. there is complBt: shutDow n heat remO!lal systems; longer t ime m n-consid erab Ie u nrertai nty w ith respect to t he m ntributio n of stants a nd sufooent instrumentatio n; s impliEied safety sys-software m mmon ~us e f ailures ( CtJ') 1D digital system reU.a- tems; minim ize poten tia l fo r severe acddents 'by inm r porating b i I ity. Fo r the potential ly safer and mo ~ passive advanced reactor redu ndanqr. diversity. safety syst.e m. i nd epende:nce; i nm !'pO-d esigns.. it is poss ib Ie that digital systems and huma n errors of rate defen~in-depth ; e1L ~

commission ( due in partto longer ti m econstan see. e.g.. I.1J1) might have a higher relative risk m nt ribu tio n, a m ntribubon t hat T he important aspects o f th is Po liqr Stall!ment a~ : ( a ) it may be d i fficu It to assess w ith any s ig ni Iicant level 0 f con Eid ence. m ntai ns o nly q ualitati v'e but well~p m ven pri nd ples fo r en hanced T hese issues 0 ffer addi tio nal reaso ns t o ap p Iy q uantit<rtive PRII safety of nuclear rea.ctor d esigns.. a nd (h ) itspecilically lacks any resul ts j u did ously fo r futu re nuclear pla nts.. ds k~based numerical criteria. Because of large uncertaint ies of TheComm issio n also offered another goal of l E-6Jyr w ithin the ds k-based nu merical resu Its. ris k a nalysts typ ically d o not Safl!!y Goals PcUqr S1>II:ement fo r frlX! uenqr o f large m1mses to the m ns iller vari<1l:ions of less than factors 0 f 10. o r 50 in suc h eOYi 10 oment for fu rther staff exam in.a tion.. A CIeEin ition fo r la 'lle nu m'bers as meani ngfu I inc re ments. Ris k Bt: perts may convert the reIe.ase was not offered in that document 12~ fn 19l the staff abO!le pol.iqr statement int o a m r~pond ing nu meri c.al crita:io n consi ~ severa l optio ns aoo Iinally r ommended that a la 'lle 'by prO!lid ing an order o f magnitooe as the sma liend iscdminalD r relea.E 'be deli ned as a ~Iease th<1l: h.as the potential fo r causi ng an fo r decid ing how much safer advanced reactors sho uld 'be fro m offsite early fataUty. ~ral o ther SKY papers (denotes pape-s current reactors. Th is.. however. is a non- sequitur a nd a prob lem sub m ittul t o the Commissioners 'by the NRC staff}. Staff inherent to risk.:tJased calc ulations. An order of magnitud e is a Requi~mts Memoranda (SRMs~ and Advisory Committee on very la 'lle i ncmmen t in th.e real w orill. and cur rmt nucJear Rea<:tor Sai>guarCIs (ACRS) letters to the Commission (e.g . l lOl) we~ ~lD rs are a l ready muc h safer than a ny o t her m mpa:rable deKItul m this subj ect The Com mission directed the stalf m ensu~ i ndustrial fad I it ies a nd hazaroous human acti v ities. Ultra-m n-that the r eva luation o f la'lle mlease m agn itOOe 'be m nsistent v.ith. servatism in d esign has a price, bo th @cono mically and ACRS proposed guidel ines I in kirlg the hieraJt:hical lweI!; of the safety ope rationa lly. As discussed in Sectio n 3. th.e p roposed new goal dbjertives, where the Ia'lle ~I ease gu iIlel.ine was m nsiClerul the surrogate nume ri cal risk- based c ri teria can be fa r mo re restdcti ve t hi rd level objertive (the quaUtative and q uantitati ve health obj ectives than the QHIOs. They are a lso quantitatively unp rm ictable in

~ the level one aoo two dbj ectives ~ Amnrdi ng t o these guideUnes. ~real risk s pace" a nd not com parab Ie w ith QlROs as they are each. subordinate I_ I o f the safl!!y !Jlal dbjocti\eS should: no n-i nmg ral measu res o f risk. They are more restri ctive in the sense t hat a rea.ctor that in a hy po thetical case may fail lD meet some 0 f the new criteda (d escribed in Sectio n 3) can stil l meet the

• b e m nsistent w ith the level above, QflOs 'by o rders of magn i tude.

• not 'be SCI conservativ e as t o Cmilte a d e facID new pol.icy.

fn s pite of the abO!le discussio ns and the b road pol iqr gu iClanCl!

• rep ~ent a simpUEicatio n o f the previous level

'by t h.e NRC Commissio ners, this paper' s observation is t hat

• prO!lid e a basis fo r assuri ng th<rt the Safety Goal Pc Ucy th roug hout ma ny ptibliation.s of the natio nal and international Obj ectives a~ 'be:ing met,

~ ulatory agend es and commerc ia l e ntities, there is an

• b e delined m hav e broad generic appUcabil.ity.

i ncreasi ng tre nd mward more prevalent use o f risk.based

• be st<1I:ed in terms t hat are understandable t o t he publ ic. and

~ ulatory concepts in gene ral, and the 'use of some fo rm of

• gene ral ly m mply w i t h. cu rrent PRII usage and practia..

nu meri cal risk t h rI!5 ho Ids as il.CD!ptanCl! c ri teria vis-a- v is safety fn 'the end. the staff reached the overall cond usio n t hat goals.. in pa rtic ular. Fo r example. a nurriber of NRC staff d evelop ment of a la rge release d eEi n:itio n and magn itude, 'beyo nd oocu me nts ( e.g.. 1. 14.151). as well as industry aoo internatio n.al a si m pie q ual i tative statan ent related t o the frequency 0 f 1E- 6 Jyr pubUcatio ns {e.g.. I.16-23n have emp loyed variou.s types of risk-is neither p ractical no r required fo r des ign or regu lam ry pu rpos es. acceptance criteria (consistent w ith the termi no logy em played fn aCJ(J ition, basul upon th.e wo rk d one elaluabng la 'lle releases w ith in the oocu ments) w h ich. i oyolve some fo rm o f a frequenqr in N'U REG*- l1 50 181 a nd o ther related activ ities. the s taff notul versus consequenCl! ( FC) c urve, or FC ancho r poi n'ts or regions. It that the ge neral *per fo rma nCl! gu idel i ne of 1 E-6JyT a nd the f iF can 'be shown that these ap proaches generally establ ish muc h stibsid iary dbjective 0 f 1 E-4Jyr are not m ns is tent w it h. the me re restrictive nu mer ical th resholds t ha n th.e QiROs, and a~

o rigin al QROs 1.11 1 ( i.e.. they a~ more conservativ e. a nd the applied as non-integral qua nti ties. W hi le t he intentio ns 'behind degree o f m nservatism de*pends on the specilic pl.ant ). th is trend are ndb Ie and mo tivated in part: flO m a d esi re t o

. E+O 1 E- 1 1E-2

~

~.

• 1 E -3 I

ill:'

£ I"

u..

1E-4 5() rom P'lte y em ~ _", '1llr8!lfb' Bill 1E-5  !!tfocl!l (lftillla r",nllJll_eBrtjllolol1ll

.." ~ ....'po** I>,., -------'JO.I E-6 1E*7 1.......- - - - - - - - - - - - - - - - ! I . . -

11001 O.(n 0.1 1.0 10.0 100.0 1000 .0 Dose, rom

. ~ 1_ I'requenq> =. C<I11=fU= Gln-e .

• 62 ) af lJRl!C. 1SO[L analytical models and ma ny other faclDr:s (e.g.. impact of safe:y subj ect: to such depenoondes on the calcu lation mo&l or ma~ ns~ Even then, t he use of representative parametl!rs (such plant design.

as the mean) iI.55iOwb!rl w ith. t he frequencies and m n.sequenms o I'twiU be a chaUenge to estab l ish c ritl!ria to ensu ~ t hat of indiv idual or integra12d aa::ident SlEnarios has I i rnita:ions of i nd iv idua l aa:ident scenari os a~ defin ed o r character-its own, as th.e types and w idths of the underlyi ng distributions i:md at the same level 0 f ~ reso.lu tion ~ across d i ffurent of the input random variables are generally ass igned by pla nt dlesigns and iI.55iOda12d PRA models for use w it h.

subj ect:ive j udgmmt rt is clear t hat these issues bem rTll! more this type of FC cu rve constTucL The syst'em would be dominant in analyses offutu rqal'lvanCl!!d reactor designs w ith inherent ly unstable and dependent 0 n subj ective i nter-less knowledge about several key aspects of the safety of t he pretatio.ns by all sides in a d ispute.

des ig n. such as the fidel ity of analyses i.n thermal ~f1 uids, 2 Relative UIlcertain*ties decrease w h.en t he assodated ra~

neutro nics, 'fis sion product t ransport m atl!rial properti es at dom. variables are summed, and t hey increase w hen the high 'II';m peratu res, component reliabil ities. and the " unknown random variab les are mult iplied_ Therefore, the effects of u nk nown.s.~ u ncertain*ties are minim ized when integrall';d risk measu res

• . Th.e QHOs hae a logical relationshi p w it h the risk that the are used as opposed t o w h.e n i.n:II';Tmedia:te and product members of the pub I ic are otherwise ex posed to as articu lab!rl Quantities, such as frequencies and con.sequenms of in the Qual itative hmJt h obj ectives. They establ ish the risks of individual acddent scenarios are used.

nudear power pla nt 0 peratio ns at a sma ll fraction of t he ris ks 3. Com pariso n of any parti al level o.f pla nt risk. such as t h.ose that t he members of th.e pub lic. not t he general publ ic at large, t hat are based on individua l aa:ioont SlEna rios, agai nst but t hose l iv ing in the v id nity of tbe plant are al ready exposed SOrTll! Qua ntitati ve criteri a can misinfo rm. or even. m islead.

to. A reduction in these ris ks for 'fu t u re reactors proposed b y The poten*tia l fo r m is i nfo rmatio.n is large because it wou Id any stakeholder ( w hich would be mnsi.sll';nt w ith th.e stall!!d not be known as to w hat fraction ( is it 0.001% or Hal of the Qualitati ve goal of t he Commissio n), should be within. reason overall integ ral risk ( wen. w ith i n. the same catl!gory, such.as and not so d rastic as to deprive the same po pulation from the i nll';rnal eIIoentsl is being com pared agai nst the c ri'lI';ria benefits that t hey may o therwise real ize f rom operation. of o Thus. the riskof an i nd ividua l scena rio would/should not these reactors, necessaril y be UIlac:ceptable if it fa Us in. th.e "unacxejr

• . Plant~pI!lCi Fic PEs and l eEs are calc ulated for m mpari.son tab l e~ region of an. FC cu rve. because the QHCE ( as safety against t he QHOs, Both of t hese, as well as the more widely goals) might still be met w it h large margin used surroga'lI'; metrics tD QHOs.. such as OJF and lRF f or lWR o A mnverse corollary is that th.e risk of individual ap pI.ications, are inll';gral Quant ities that are derived fro m the scena rios sh.ou.1Il not necessari Iy be viewed as " ac:r:ejr contrib ut ions of all acdoont scena ri os that are m nsioored in tilb l e~ in. the other region either. as a pruoont approach the plant~specifi c risk moooL rnteglal risk measures inm rpo- 'ID safety as.su rance always seeks tD incorpo rall! reaso ~

rall! at least th ree i m po rtant properti es: able additio nal contro ls w h e~ ever a proper Qua li tative L Defi.n:ition or c haracterization of individual aa:ioontsamar- engi neeri ng j u dgrTll!nt 0 r a Qua ntitati ve analysis so ios is dependent on bo th the specific PRA modI:!! (e.g.. dictates, FaUi ng w ith i n the aa:eptable reg io n cou Id den.y large fa'll It trel!!' small event tree versus sma U fault t rt!l!,l'large t he designers and ot hers from t horough engineering event tree) and the sped Fic plant design (e,g.. complex w ith th.i n ki ng i n.th.e safety design process.

more active safe;ty sy.sll';ms __sus less c.o mplex w ith. more

• rf it is assu med t hat a fu t ure design. of an. HTG R o r an. SMR passive safety sy.sll';ms~ IntEgra12d risk m easu ~ are not meets the FC curve. then t he NRC w ill be on rem rtlfor

m rti.fyi ng that t he level of risk -bil!il!ld safe!ty of t hi.s design is acm ptanCl! cri ter ia w ill be variable !br eac h d esign, s pec:i fi.c "aa:eptilble,- and in (JJ ntrast; any design th.a t does not meet PRA model, and mac1D r silil!. The v ariab i~ty can be substantia l th is level of safety. even Fe r a si ngle aa:ident sa mari o w i th all in some GlSe.S..

the attmdant unm rtainty. is unsafe. The same p rob lem is en(JJu nb!red even if t he governing document is from the It is i m lXIrta.nt that t he N:RC staff be mg niz.a.nt of t he above i ndustry. w hether or not it is I!X plic itly mdorsed b y t he N:RC, issues in complyi ng w it h t he Com m issio n d i roct:io n in b!sti ng the such as an ASME or ANiS st mdard as in 118 ~ HOw (JJ uld the concepts embod ied in N:URE& 1860 in an actual lim n.si ng regulator aa:epta des ign with one o r rno re accident scenarios app roval process for a future pla nt The .<ta.ff should ensu re th.at in t h.e *'u.nacm ptab le- region when t he governing ind ustry t heir review w i II not deviab! from t h.e 10 ng- standi ng Com mission standard itself has labeled i t as suc h? premaents in estab ~s hin g t he many elements of a ris k- informul

• Some cu rrent L....1Rs w ill li kely not meet this FC CUIVe. ap p roach. W hLle th is paper has IDuchul ulXIn on Iy a r..w ID pies.

A misunderstanding o f the intmt of this culVe and t he role fum A! I>aper:s can d iscu.ss the use of PRA. includ ing the introdu c-that N:UREC reporn play at N:RC (JJuld lead some t o incorrect t ion o f a proiJ(lSl>d tech nology-ooutral generic risk measu re t h.at (JJ ocl usions conm rn i ng the adequacy of safe!ty of cu rrent w i II allow !br cross-com IJ'ilriso n 0 f the level of safe!ty !br d i lferen t pla nts, because t he N:RC m d Jo r t he nuclear industry them- pla nt designs ind ependent of sit e-speci fic characb!risties; al>"

selves (as. e.g. in [15,18 1) hav e labeled plants that d o not meet p roach t o defe!n.se-in-de:p th ; selectio n of t he So-GlUed l.im nsing-th is cu.rve as " unacmptab Ie.- basis even ts; and selertion of safe!ty SSC:s in a risk- i n.formed and

• The FC curve is. in fact. i ntrodu ci ng new and more restrictive per!brm.an<p-based f rame:wo 11<.

aa:epta nm c rib!ria than the QHO safety goals as evident by It should be added t hat alternative and complementary risk i ns pectio n and as me nt ioned in 115 ~ in cont rad iction ID the met r ies ID QHOs can be usefu l ID a IXItentia l ap pi icant for a design ACRS guidanm mentio ned above. certi.lica tion o r (JJ mbined license, fo r exam plelD assist in

• The combi ned effect 0 fusi ng risk met r ics as aa:eptanm c ri b!ria dem min.ation o f h.a ving reached a suffic ient mix o f preven*ti ve and ap p lyi ng them on the level of ind ividua l accident scena rios and mitigati ve featu res in a new design ( i.e.. safety design t rade-can lead to otherun desi rab Ie out(JJ mes. Future mac1D r designs o ff decisionsl arID (JJ mlJ'ilre relative safe!ty of d i fferent designs.

off~ing lower total ( integrab!d ) risk th.a n c urrent operating T he tech nology -neutral generic ris k meas ure mentioned above reactors may be erroneously labeled as ' 'u nsafe- and not be w ill satis fy t he latter need !br futu re reactor d esigns !br w hic h the pu rsued. 0 r be bu rdened w it h costly and un nemssary d esign CDP and lRF metries may not be ful ly applicable. An example o f mod ificatio ns. an alb!m ati ve FC c urve that can be effe!ctively used for safety o An exam p Ie of the above ( i nvo Ivi 'Ill a pob!n tially safer design t rade-off decisions is discussed in Sectio n 6.

fut u re reactor des ign) is a reactor aJO la nt ~n e break !br a high-12m pe ratu re gas-coo led reactor (HTGR). [n a by pothe-tical c.ase, it can be assu med that an ap pi iean t calc:u lab!s the frequency and the conseq uences of the scenario in a way that allow s them t o show t hat it is "acceptahle.- Anyone The im lJ'ilct of the aforementioned issues may not be as great in ind ined to quest:ionth.e va~d i ty 0 f t he ca lcu.latio ns ca n: p ractiCl! w hen t he FC cu rve of N:U RE& 1860 or a si m i lar (JJ nstruct (a) lXIint t o the degree of u nc.ertain ty in the pipe b reak is used o nly by t he designer as op iJ(lSl>d ID the regulator. The frequency because of v ery ~ m ited nu mbe r of years 0 f designer ca n use such constructs 0 r con.CI!pts as (JJ m plementary ope-ati ng experi enm w ith these reactors; ) poi ntln in !brmation in an iterati ve ma nner th rougho ut the d esign promss.

(JJnd itions suc h as high ope rating t em peratures as add i - A prOb lem t hat may be en(JJ un teA!d in that pro mss is t hat a tiona l r&so ns fo r much higher fai lure freq uency lXl'ten tia l p roper interpretation 0 f some risk- bil!il!ld (JJ ncepts may not be as th.a n in t he l W Rex perienm ; and (c ) c hallenge t he assumed int uit ive for the designer. especially for t hose w ho are not PRA rad ionud ide airborn e fractions produced by unm rtaint ies ex perts. as it may appear at lirst. rn addit ion, manuals of p ractice, in so urce t er ms {e.g. long- b!rm di ffusio n o f rad ionud i des stICh as standards 0 r guides t hat aA! d eveloped by the industry through aJilteC fuel IJ'ilrti d es. ~us pension causul by may be mdorsed or refel1>nced by the regu laID rs and be usul in vibratio n effects, higher t em peratu res. lower plab!out, way s that produCl! t he uni.n b!nd ed resu.l ts (e.g. leading to e1L~ These c hallenges can lead ID a m nclusio n t hat the rej ection o f safer d es igns ). For t his reaso n, it is sugges b!d th.at

.smnari o falls in the "u nacceptable" regio ninstead t he use 0 f quant itative PRA results in t he (JJ ntext of des ign or

• Si mp Ie andJor pas.siv'e reac lm designs wou III have fe!wer regu lalDry risk-accep'tance c ri b!ria be avoided by all. Insb!ild.

numb er:s of acciden t scena rios t han com pi ex and active Sectio n 6 provides an alb!rna tive (JJ nstruct that ffi<IY be used by des igns at the same Iev'el of accident smnario delinit ion t he industry t hat w ill aa:ompl is hthe in tended purpose (design (e.g. sys b!m level ) and w ithin the same PRA model. safe!ty trade-off decisio ns) without the negative (JJ nnotatio ns th.at The diff~ence in the number o f ac:cident scenari os (JJ uld are associated w ith N:U REC- 1860s version 0 f an FC cu eve.

be in multiples of 10 rather than in algeb raic fractions. As a hypoth.e tic.al examp le. two reactors may have the same ris k pro Ii Ie. bu t the Ii r:st has 10 sequences w ith JO rem at 1 E- 61y r. S. Inmlpmtati<>n of tho! as :Rem criteri'l>n u....t in and the second has one sequence w ith a consequence o f lU (FR l00,l5U.34 JO rem at l E- 5/Yr. Und er t he FC curve (JJ nstruct, one is deemed acrept.able and the 0 ther is not; w h ic h does not make The 15 rem c ri b!rion used in 10 CFR 100 and 10 cm 5034 is sense in " real risk space.'* o fb!n used as a de facto dose ac:ceptance cri b!rion !br DBAs by the o Thus. the use of risk- based a<E:eptance crit~ia 0 nthe level 0 f N:RC staff. T his *usage is. boweve:r. contrad ictory to actual ind iv id ual aa:ident .smnarios (as opposed to integral quan- Commissio n IXII icy and gu idance as described exp l.icitly in N:RC tities) m<l1( be viewed as penal iz:i ng s imple and passive regu latio ns. as d iscussed in t his sectio n. SinCl! a nud ear pla nt is designs in favo r of active and (JJm pi ex designs. in vio lation 0 f designed t o adequa b!ly respo nd t o the O<E:U r",nee 0 f Des ig n &a.sis the Co mm ission Pol icy Statement o n Mvanmd Rmctors l UI. Events { DBE incl udes Antici pated Operationa l O<E:u nences and

• Again. bo::ause integral mllB.S ures o f risk are not Obtained in OIesign Basis A<E:i den ts~ t he ex pecta.tionis t h.at the associamd this model applications of these smnario*- I..... el and risk- based o ffsitecon.seq uences w ill be sma U {e.g. fractions of 15 rem T EDEl.

heav ier em pbasis in use of qua nti tat iv-e PM "",til ts. T hese risk measures are somet i mes compared to r isk t hreshold values t hat hav-e attai ned an actual. o r ev-en a de fac to. regu lalDry stature o f

" risk accep tance c ri teria" i.n CErtain insta nC1!5. Such ap pi ications of Add iti onalcor'ltrols. risk measu "", for a nuclear reactor d esign 0 r a specific pla nt are not always in keepi ng w it h the t e""ts 0 f risk- i n formed r<'gula-may be con*sldered t ions. w h.ic.h ca Li for com pari ng (i.ntegral ) measu res of the calcu lalEd risk (e.g.. PEs and LCFs or t heir suitable surrogates such as t he COP or the LRP) against QHOs ( or their s'urrogab>

targets. e.g.. 1E - 4Jyr fo r CDr ) on 1'1 as ' 'safety go als."

In add itio n, using nu merical PRA resu lts. parti clllarl y those that are not integral quan*ti ties, in a ris k-aa:eptanee m ntext, ev-en by the nuclmr industry (as opposed to the reglIlators) can have Ad dltlonall controls need numerous u ndesirable con.sequm ces. Examples of these among not be con sidered many d i.scussed in the text i nd ude: the t endency to pena~:z.e s imple. passive safety system des igns in favor of comp lex. ac tive l og Consequeooe designs; and futu re rea::tor des igns 0 fferi ng lower i ntegralEd risk t han t hose 0 f the c u mmt and high 1'1 safe 0 perati '1!l reacID rs may is- 2 ~ A Ol ~..a:l .JiCci cEt t ~i1.eI1r.J ~ f;requ_e rq' "eJ'5U!5 amsequ_eTl.a!: Ql:rw! be er roneously labeled as unsafe and not be pursued. or be

.h t GIll used by .o;pplic.o.l1I: durin~ dosign procrs ..

bu rdened w it h m stly bu t unnecessary des ig n mod i licatio ns.

These issues can lead ID serious un i nb>nded m n.sequenees in whether add itional m ntrols sho u Id be m ns idered for the licens ing of fut ure rmc:t:ors o r creating new challenges regardi ng s(ll!Ci Fic s<l!.nario.

t he safety adequacy of ex isting pla nts.

(v ) The two regions are sepalated bya band 0 f pe rhaps an 0 l1ler The paper also 0 ffered an al ternat iv-e use fo r a frequency v-ersus of magnitud e variation w ith d iffused bou ndari es ( such as in con.sequencecu rv-e as adesign or operational safety optimization Regu latory Gu ide 1.174 ) on frequency and con.sequence.

too l for use by the reaclD r des ig ner o r plant operator.

lather t h.a n Firm bound aries. T his is because any single parametl>r o f samario frequency or m nsl'fluence ( the mean is typ ically u..oo fo r all ) is itself subj ect to un<l!.rtainty and Diisdaimo<Y eJ1suing ch.a llenges, as the ranges of variabili ty and the underly ing d istributions are generall y assignol subjectively.

(v i ) The m n.sequ enee scale may be related ID app ropriate pub ~ c The wo rk relalEd t o t he development of this (>aper was heal t h measu res and /or cos t-beJ1eFit for t he i nel usion of the condUCb>d at t he IElq uest 0 f th.e Oi rector of the Advancol Reactor add itional control und er m nsideration.. Programs at t he Office of ~w Reaclllrs (now retired ) in the last

( vii ) Si nce t his cu."'" is u..oo as a desig n aid for t he applicant, qu arter 0 flOOS at the US N:RC. w hi Ie t he au tho r was on loan from

~ Iatory staff would hav-e no position about t he acc:ept-t he US Dl!partment of E ~.

ab i Iity or the lack thereof associated w it h any (>a rt of its Neither the author. no r t he United States Government; any m nstruct. ind udLng the anc bo r poin~s. The regu laID r must agency thereof. 0 r any 0 f thei r em ployees makes any warlanty.

use the total ity of the safety in formatio n del iv-ered by the ex pressed or impliol. or assumes any legal liability o r responsi -

design and t he proposed operatio nal plan t hat ind udes b ility for the accuracy. m mpleteness. o r any thi rd party's use of the trad itiona l deter ministic requi rements alo ng with the t he results of such use o f any in formatio n. p lUduct, or p rocess su pplemental PM in formation in m ncJuding that the pro- d isclosed. 0 r represents t hat its use would not infri nge privately posed pla nt is safe. ow ned rights. Reference herei 0. to any sped lic com mereal product, precess. 0 r service by trade name. tlademark. manu fac-turer. or otherwise. doos not neCl!5sari ly m nsti t ute or imply its Note that the bo unda'Y region 0 f essent ia l ly constant risk is endorsement; remm mendation. 0 r favo ring by the Uoi ted States on 1'1 m ncept ua L The d esigne r may decide that in certai 0. Govem ment, 0 r any agency thereoE sub-Jt>gio ns and bocause o f specific considerations. such as ev-ents The v iews and 0 pi 0. ions of the auth.o r exp res sed herein d o not w i t h particulady high o r low f lElquencies and/ or con.sequenCl!5. necessarily state or reflect t hose of t he UnilEd States g.ov-ernm ent and in t hose areas g .ov-erned b y exis ti ng regu lations. devi.a tions o r any agency t hereo E fro m the boundary region are warranted A.d latow IedgrDl!n1!5

7. Summary and. co nc:I'usimlS The aut hor w ishes to thank Or. Do n Dube ( US N:RC) w ho was Risk- informed regu la tio n is buil t around t he m acept o f t he Ii rst expert to l1!View the eady versio ns of t his paper and usi ng tradi tional d etl>rmi.n.is tic techniques of safety assu ranee offered his b road and in-depth kn owledge in su pport of its su p plemen lEd b y PM infor ma tion and insights. Trad itional dev-elopment. Mr. Ala n Kuritz.ky and Drs. Mo hseJ1 Khat ilr-Rahbar d eb>rminis tic tech niques include concepts such as inm rpolation and Doug True p rovidol many usefu I insig hts.

of red undancy and d iv-ersi ty. incor po ration o f safety ma rgins.

ap pi ication 0 f defense in depth. ap pi ication of q ua~ ty assu lance.

et c PRA resul ts should play a ~mited and supportive role in maki ng decisions about adequaq of safety i.n a risk- in.fo tmed regu lalD 'Y framewor k. (1 1 ChojllllOn J, H= RisJc';"_ . l:edm:i~41e1Jtr.i ~ ..oo 1ia=i'18 Hcwever. re<l!.nt trends i nthe dev-elop ment of new risk- relalEd f.,.",.,.".n ilr n .... """""" pi "'tl. In : ANSI'SA~~ ~~

tJll'SA during /he ....duT ~Km ..,ll ~ ffi. ~ '~ ll . ~ .

ap!>rlladles, w hether they are perfo oned by the ind ustry. N:RC 121 US c. ~1 Regis .... ~1 j;Jt l W2fL s..fety goo.tls for /he oporotio", of staff 0 r other domestic or i nb>m ational bod ies, are towards mdur pawer plonts" August 2 1. 19!11l

II I lIS NJC. le:teQl ll.<8ister. ;q. _ an u.. 01 prdJ.mlis;;c ris k I2Il I l-fun~ ~ (Coou!hor). "',..,. D",;;ll1Jte of Nuclo.oT s..fel)'. Ilegu:lor"')'

_=ment metI1oo. in mdo.oT regulrnll)' ""~ .1lin ~1 Micy !ltot~ l'iewpaint <JJl inmvative VH1lt ~qpmen t in """"'-  : 4th August 16. vot 60; US). l!l!1!!i . P. 42622- !L in"'n.>tian~l "'Pial meeting .., ~.igh temperalll"" _ _ ""Iogy.

1<11 lIS N:RC CeJl~ Ister CUIIlO2<i. D n:I:Mdu~1 p1~tt .....min-. i" ~ Septembor 2!I"()""'er 1. 200!i.

..ment vulner;lbili ties,.}lavembor n. 19sa 12 11 ]. 02-02. N..a...T "'&I' In_*'. A risk . :b!:mod. p".i",,,,,,nce.m.ed I~I lIS :RC SOC'MI!l- 144. White popor .., ris!c-in:b!:mod ~d pedm:m~ce""' <d regu'b.tOl)' nmework ilr paw... r&ctors" u.y 2001-regu1oticm. J;>.TI~T)' 22. 1 :Il SQrf ""1uiT<:mO:Ill5 mo:mor.oTldum ~Pl"""ed UoTcl1 1. 199!L 1221 -""'TI Jo"'- (~""',). N.tioml Nu<lJe..r RegW~or. SouJtb Arne.... SouJtb AfriaTl ...rety ~ ..... ment lnmo. work ii, lihe p01tIle bed madulor ~. In:

161 lIS JC. ~'b.1:al)' gu.ide 1.1, 4. An ~Jlllroo<il1 fo, ... in g prdJ.mlistic risk 4th intermtioml "'Pial meet:iJ1g OIl high ~er.o1ltae _ _ mlogy.

_.....,.,nt in risk in:brm<d docisi<Jn. an plo_pocific d h _ lie tile Septe_ 29-0dJollor 1. 200!i.

li EJ1sm:!: msis,. R~:ian 1. moem1Jer 2 - 1231 m m(J<ty) ltd . ~Ia'bilistic risk """""""", t (~ , "1'J-<lrll for the !He 1'71 lIS NIl<: NUR1lC-()fIiliJ. lIS ..a...T liquJ..t<JI)' Cammission . uoom """;ew modu:lor ,..um. ~sion 1. J une 12" llOOl1

_T p1 ..n. limsion l. M ~d1 1 lCh.>pter 191*

lSI lIS c. NUJtrC. l UiJ. Severe ..nctent rim: ~TI "",,,,,,,,,,,nt for five lIS

_erP:Io_; 0rt.dJer 19

• 191 lIS JlC. SEc 4!9. 102.Im1'lemen ta:i.., 0I~ gml p<J!i cy;M.>:r.nlll. 199!L 1241 lIS NJC.

w June lOO7.

~ CI'.tJ1.tJ lll1.

per:brm~ce.m. <d

14. 2

_ r=mmen:l ..~ OIl' ~rding ~

""";sion I!o 10 a;R p ..rt 9ll

• St.off requirements mo:mor.oTldum ..JlP7""ed rill mk-in:I:Jrmed 3 U6.AH81);

Sept em'bor 10 .

11111 lIS C Ml!S I.<;Jbor I!o iNRCCI""j,:n",n. Ml!S<:<II1llDeI1ts.., ~n ; mpl~ 1251 lIS c. SIlCV- iI!Ul(J!;G. SUfi ~roo<il1 ~Tding .. ri sk.,informod md

<JJl p'b.n i

l1lihe uiot

r gml policy. IiIb)' 11. 199'. perfor:n:an...b&ed ,.".,..., to p.ort ~Il 01 ;;t1o 10 01 the (h de 01 I'<d_l 111 1 lIS JC. SECI' . .tJ19fL Stm!s "'JI<>rt o n ri sk'; nfmmed d h _ lie tile !i.guloti .......TId Il ~ing ~ Policy _ <JJl Def""'e4n 111 for

~~l ""1 ui~ofl ll a;R port 9ll (optian l) w ~ ..ti<Jn.on _:reRad<lrs"Ap ril 7.2Il1l!L ris!c . :b!:mod .n~nges 10 10 a;R port 9a.4<1 (o:nnbustihle g& m_~ I2GI lIS N:RC ACIlS1W2Il'. ",.oopment of ~ tMlno1ogy-"1eutral regu'Llt"')'

tembor 14. 2Il nmeworl<" Septembor 201. 2 (12 1 lIS - C SEC/' . 111 ~ utianol)' light wo1:<r . - (U'IIi) ~n 12'1 Memor.ondum. Eo.... Iml]7o I!o]..l!. .... Foreign Invel trip rep<Dt ilr the iss"", w /h eir r&1iomh:ips I!o ~ reguIot Ol)' requi.-.men Juno 2Il. 19 In t ermtion;,l Atom;c m;~ Agency Cans.,]~.qo meeting lie ~I'm !A!lJ\

1131 lISNJC.Feder .. Rqister. ""t 7:l (99).N 2IlOS-tlZl,. oIicy ....t<men t on ...fety gui de on _sifi~<JJl 01 """'''''''' Sf5"""'- ~Tld corop<l11ellts fnmJ regul ..~ .., 01 ~ v"Tla<I ~ 0rt.dJer 14. 2IlOS. P. 0061 2~. ApriU4 lihrnugh ilpril 2 2006;),by :5" 20011 11 41 lIS NU c. l nfLD ~ pre~p1ic.o.~ <m...rel)' ... ~luo.ti .., "'JI<>rtfor /he 12~ 1 lIS NJC. <='I Regi5'"". 9ll l2 13fL J\ol;q. .werr.ienl on ..vere m>du.IoT hign..~er.o1ltae gos-cooled ~r. Uorcll 19s9. ~, ..nctete ~, ding row"" d"';gns ..n:I exis ~ ng plonts. August 8.

11:51 lIS NJC. NUJtrC.1S61l. ""","" .i1i l)' -d)' for .. risk inbmed w 19f1l1.

I""f<Jrl1l.>TI.....b&ed regul ..~,,)' , lr uctluTe for hi;tu", plott Dicensin '<. * ....,""""'" 12 I (h de 01 ~ llegW- ..m 1 0; J.. ,.,,,,I)' 1. 200!i Io...pter 1iii.

200'. Pili (h de 01 ~ Regul ..~ OIl" _ S 1- 199; J"""'l' 1. 200!i 100001' t... 11l1.

(161 ~ .. Al<lmia. ToJl"l ~regulot"'}'<riteri.m /he ....Tldm -IHTCR"OO I! 11 St.ollin - c. ... from m<d:ic.ol miotion .,,,,,as. H~1tIb ""Ym SoOety.

I<<CR-8!5

• Sept"mlJer 199!L ( 1ttpt Ilwww~j11p'publ_""' I~ ;; desldm...r~ic.o._ ..~ on.

(1'1 1lur0000000TI (hmn:rissiom.. ~7OJI""'TI ...rei)' 'Jlllroo<il1 for mOOuJ ..T Hi' 11tml } ; 1Ipd.>ted u.y 2Il. 2Il1l!L DoaJment na. ~ . .-Sf4.l. ~ lri dlod dism:mution. April 1:5" P 21 ~ Pi!.. Tbe high b rl:grOlJlld mi.>ti<Jn ..,..,. in b=. iraTI: Ceology.

2OO ~ nann" b >o1ogy. 11<<. ..TId possible regulotOl)' fmL In : VIM "W C<JJl~=

11 ~ I AN S-S.1.2tJrot Nud ...., uiot:r <ria .. ~nd ...f <ty do:sign p:roc= for T~",.., . If2.I'ebru;,1)' 24.-l!i. 2 . 2.

madu:lor bolium-<llalod ......am ~ts. ~; Jun.e n. 200fL P31 J.>w<llVWSlci z. Ioni zing .-..di"~ 0Il W .-..diaod:Mt)' in !h.e 20th <= tuI}' . In :

1191 ~eI)' 1Ii!:p

Tlts wi/h Iln t~tio :nal mn~cean ~:n,alld it!iirol e;ind~.m:is.Ji:ll.d~ m>du.IoT high t<:mp<:r.rIlU"" g& C<101ed ~o ... April. .lIOO:Il Teb:r.on. Iran. Ckitl 18 0. 2000.