ML24197A161

NRC Staff Presentations for the Public Workshop on Development of Risk Metrics to Support Implementation of Risk-Informed Programs for Advanced Reactors

ML24197A161
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Issue date:	07/15/2024
From:	Jeffery Wood NRC/RES/DRA/PRB
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Public Workshop on Development of Risk Metrics to Support I mplementation of Risk-Informed Programs for Advanced Reactors

July 18, 2024 Workshop Over view

• NRC Opening Remarks

• Review Workshop Purpose

• Review Meeting Agenda

• External stakeholder presentations

• NRC staff presentations

• Open Discussion

• Public Comments

2 Public Workshop on Development of Risk Metrics to Support Implementation of Risk- Informed Programs for Advanced Reactors Opening Remarks

Division of Advanced Reactors and Non-Power Production and Utilization Facilities (DANU) of NRC s Office of Nuclear Reactor Regulation (NRR)

Workshop Purpose

Gather input on strategy for establishing risk metrics for Non- LWRs (NLWRs).

Focus on technical aspects of risk metric development and use.

Identify the many risk metric connections to regulatory programs.

Focus staff ideas for further work on risk metrics for NLWRs.

Discuss NLWR operating experience data, methods, and tools to support risk estimation.

4 Project Drivers Understanding that LWR risk Prepare to assess metrics may not be suitable for applicant-proposed comprehensive plant risk NLWR designs. metric (or set of metrics) SRM-SEC Y 0021 and associated methodology. provides motivation and Commission direction to staff Development of metrics direction to staff related on Part 53 rule for different plant designs NLWR risk metrics, but this (e.g., LWRs, gas-cooled wor ksh op i s not part of the SRM-SECY 0021 (ADAMS reactors, molten salt Part 53 rulemaking.

ML24064A039) re a c to rs ) .

The risk metric(s) and methodology should inform NRC s risk-informed decision making (including applications after initial licensing).

5 NRC Tasks on Evaluating Risk of Advanced Reactors

• Development of technology-inclusive risk metrics that can be applied to NLWRs.

Task 1

• Output: White paper outlining vision and strategies for risk metrics and tools to support risk-informed licensing and oversight for NLWRs.

• Includes topics to be discussed at this w orkshop

• Developing methods, tools, and processes to collect, analyze, and use data Task 2 to support RIDM for advanced reactors.

• Includes topics to be discussed at this w orkshop

6 NRC Tasks on Evaluating Risk of Advanced Reactors (continued)

• Scoping study to evaluate the risk and modeling approaches for a selected Task 3 advanced reactor design.

• Effort expected to be focused in fiscal years 2026 - 2028.

• Enhancing RIDM guidance and framework for advanced reactors.

Task 4

• Effort expected to be focused in fiscal years 2026 - 2029.

7 Focus of NRC Working Group

Risk metric(s) should be comprehensive in covering all radiological sources, all operating states, and all internal and external hazards.

The Working Groups initial focus:

• Risk metrics that express plant risk so they can provide indications of meeting desired ultimate risk objectives, such as the Quantitative Health Objectives (QHOs).

• Initial focus on NLWRs

• For example, molten salt reactors, high-temperature gas-cooled reactors.

• Initial focus on radiological sources from reactor s primary system.

8 Public Workshop Agenda (part 1 of 4)

Time To p i c Speaker 8:30 am - 8:40 am NRC Opening Remarks NRC 8:40 am - 8:50 am Purpose of Public Workshop Jeffery Wood, NRC Review of Applicant-Proposed Risk Metrics for 8:50 am - 9:20 am Commercial Nuclear Power Plants Licensed Marty Stutzke, NRC Under Proposed 10 CFR Part 53 -

Development of Interim Staff Guidance 9:20 am - 10:05 am NIA Perspectives on Comprehensive Risk Patrick White, Nuclear Innovation Metrics Alliance (NIA) 10:05 am - 10:35 am EPRIs Risk Metric Work Eric Thornsbury, Electric Power Research Institute (EPRI) 10:35 am - 10:45 am Break

9 Public Workshop Agenda (part 2 of 4)

Time To p i c Speaker 10:45 am - 11:15 am Breakthrough Institute Perspectives on Risk Adam Stein, The Breakthrough Metrics Institute Challenges and Lessons Learned in Applying Kyle Hope, Westinghouse Electric 11:15 am - 11:45 am NEI 18-04 During Active Design: The eVinci Company Microreactor 11:45 am - 12:15 pm Hazard Level Selection for LMP Jessica Maddocks, X- E n e rg y 12:15 pm - 1:15 pm Lunch Break

10 Public Workshop Agenda (part 3 of 4)

Time To p i c Speaker

1:15 pm - 1:45 pm UCS Views on Advanced Reactor Risk Metrics Ed Lyman, Union of Concerned Scientists (UCS)

1:45 pm - 2:15 pm USNIC Perspectives on Risk Metrics Cyril Draffin, U.S. Nuclear Industry Council (USNIC)

NRC Plans for Work on Operating Experience, 2:15 pm - 2:30 pm Methods, and Tools to Support Advanced John Lane, NRC Reactor Risk

2:30 pm - 3:00 pm NLWR Data Insights and Experience Dave Grabaskas, Argonne National Laboratory (ANL)

Advanced Reactor Operating Experience Data Sai Zhang and Diego Mandelli, 3:00 pm - 3:30 pm Analysis to Support Risk Estimation and the Idaho National Lab. (INL)

Intertwining of Data, Decisions, and Reliability 3:30 pm - 3:40 pm Break

11 Public Workshop Agenda (part 4 of 4)

Time To p i c Speaker 3:40 pm - 4:10 pm NRC Preliminary Thoughts on Risk Metrics for Matthew Humberstone and NLWRs Gerardo Martinez-Guridi, NRC 4:10 pm - 4:50 pm Open Discussion All 4:50 pm - 5:00 pm Public Comments NRC 5:00 pm Adjourn

12 NRC Working Group on Advanced Reactor Risk Metrics

Matt Humberstone 1

• 1 NRC Office of Nuclear Regulatory Research (RES) / Division of Risk Analysis (DRA)

Gerardo Martinez-Guridi 1

• 2 NRC Office of Nuclear Reactor Regulation (NRR) / Division of Hanh Phan 2 Advanced Reactors and Non- p owe r Production Utilization Facilities

( DA N U )

Marty Stutzke 2 Jeffery Wood 1

13 Questions?

Comments or questions on workshop purpose?

14 Acronyms and Abbreviations

• ANL -Argonne National Laboratory

• NRC -CommissionU.S. Nuclear Regulatory

• CFR - Code of Federal Regulations* NLWR -Non -Light-Water Reactor

• EPRI -InstituteElectric Power Research

• QHO -Quantitative Health

• INL - Idaho National LaboratoryObjective

• LMP - Licensing Modernization

• RIDM -MakingRisk- Informed Decision Project

• UCS -Union of Concerned

• NEI -Nuclear Energy Institute Scientists

• NIA -Nuclear Innovation Alliance

• USNIC -U.S. Nuclear Industry Council

15 Re vie w o f Ap p l ic a n t- Propos ed Ris k Metrics for Commercial Nuclear Plants Licens ed Unde r Propos e d 1 0 CFR Pa rt 5 3

- Development of Interim Staff Guidance -

Ma rty Stu tzke S e n io r Te c h n ic a l Ad vis o r fo r P r o b a b il is t ic Ris k As s e s s m e n t Divis ion of Ad va nc e d Re a c tors a nd Non- P o w e r P r o d u c t io n a n d Ut il iz a t io n Fa c il it ie s (DAN U)

Office of Nuclear Reactor Regulation (NRR)

Ju ly 18, 2024 1 Ag e n d a

• Re v i e w o f S RM- S EC Y 0021, Ite m 2

• Development of interim s taff guidance (ISG):

• IS G a p p l ic a b il it y

• Terminology related to ris k metrics

• Review flowchart

• Cha nge p rovis ions

• Intellectual property

• N e xt s t e p s

2 S RM- S EC Y- 23- 0021, Ite m 2

• Dis a pprove d c odific a tion of the QHOs

• Re vis e d ra ft § 53.220 to s pe c im e tric s ) a nd a de s c ription of the a s s oc ify tha t a ppla te d m e thodolic a nts m us t progopos e a c om pry:e he ns ive pla nt ris k m e tric (or s e t of

• Expla in initia l a nd bounda ry c onditions

• Expla in a s s um ptions

• fr o m t h e fa c il it y:Cumulative and comprehens ive mean that the ris k metric(s ) s hould approximate the total overall ris k

• Screening tools and bounding or s implified methods may be us ed for any mode or hazard with an acceptable technical bas is

• Addres s uncertainties

• NRCs a pprova l of the m e tric or s e t of m e tric s is not, by its e lf, a n indic a tor of a de qua te prote c tion

• Ens ure tha t a pprove d m e tric (s ) a nd m e thodology c a nnot be c ha nge d without prior NRC a pprova l

• The m e tric (s ) a nd a s s oc ia te d m e thodology will not c ons titute a re a l -time requirement

• Conduct tabletop exercis es and wides pread public engagement with interested external stakeholders

• Se e km e m o r ia l iz e d c om m e nt on whe the r a nd how c om pre he ns ive pla nt ris k m e tric s s hould be c odifie d or othe rwis e

3 Tentative ISG Scope

• Addres s es the NRC staff review of applicant -propos ed ris k metrics for commercial nuc le a r p la nts und e r p rop os e d 10 CFR Pa rt 53:

• Li g h t -water reactor (LWR) and non -LWR te c hnologie s

• Rinjadiuroly to the publogical ris ks (ic due to the heals eparate guidance ith effs beiects ofng dev the chemieloped fcalor haz the as s es s ment ofards of licens ed mater the ris kial of) permanent

• In it ia l a p p l ic a t io n s fo r :How the propos ed ris k metric is

• Sta nda rd de s ign a pprova ls (SDAs ) pres ented to the staff determines

• Standard des ign certifications (DCs ) what NRC internal proces s applies.

• Manufacturing licens es (MLs )

• Cons truc tion p e rm its (CPs )

• NRC Management Directives

• Operating licens es (OLs )

• NRR Offic e Ins truc tions

• Combined licens es (COLs )

• Changes to ris k metrics or ris k performance objectives after initial licens ing

• Topic a l re ports s ubmitte d by:

• Individual applicants, permit holders, or licens e holders

• Third p a rtie s , e .g., d e s igne rs , ind u s try grou p s

• Ind us try c ons e ns us s ta nd a rd s

• White pa pe rs 4

Tentative Terminology

Pos s ible terms to be defined in the ISG:

1. Ri s k m e t r i c ( RM)

2. Comprehens ive ris k metric

3. Ris k performance objective (RPO)

4. Ris k s u r ro ga t e Exa m p l e fo r Dis c u s s io n Fo r a l l p l a n t s , IEF R 5 x10 -7 / p la n t - ye a r

Sta te m e nt of R i s k Me t r i c ( R M)Ris k Performance Objective (RPO)

Ap p l ic a b il it y Calculated by the PRA A ris k performance objective is a

• Te c hnology -inclus ive preestablis hed, indicative value of or reactor s pecific? the ris k metric that is us ed during

• What s ource(s )? r is k-inform e d d e c is ion m a king to

• Wh a t P O S s  ? gauge plant safety.

• Wh a t h a z a r d s (s )?

5 Te nt a t ive Te rm ino lo gy (Co nt inue d )

Ri s k S u r r o g a t e - general form If [r is k s u r r o g a t e is m e t ], t h e n [r is k m e t r ic is m e t ]

Ex a m p l e Fo r LWRs , if C DF 1 0-4 /r-y, t h e n ILC F R 2 x 10 -6 /r-y

Q u e s t io n F o r LWRs , if HCLPF 1.67 SSE, then s eis mic ris k is acceptable (SRM -S EC Y 087)

• Is the HCLPF (high c onfid e nc e of low p rob a b ility of fa ilu re ) d e ve lop e d by a P RA-b a s e d s e is m ic m a r g in s a n a l ys is (S MA) a r is k m e t r ic o r a r is k s u r ro ga t e  ?

• Note: The 1.67 multiplier has not yet been accepted for non -LW R s 6 Exa m p l e  : De r ivin g Ris k The safety goals broadly define S u r r o ga t e s fr o m t h e QHOs an acceptable level of ra d io l o g ic a l r is k

Individua l me mbe rs of the public s hould be provide d a le ve l Societal risks to life and health from nuclear power plant of p rote c tion from the c ons e q ue nc e s of nuc le a r p owe r op e ra tion s hould b e c om p a ra b le to or le s s tha n the ris ks of p la nt op e ra tion s uc h tha t ind ivid ua ls b e a r no s ignific a nt ge ne ra ting e le c tric ity by via b le c om p e ting te c hnologie s a nd a d d itiona l ris k to life a nd he a lth. s hould not b e a s ignific a nt a d d ition to othe r s oc ie ta l ris ks . S GP S

The risk to an average individual in the vicinity of a nuclear The risk to the population in the area near a nuclear power p owe r p la nt of p rom p t fa ta litie s tha t m ight re s ult from p la nt of c a nc e r fa ta litie s tha t m ight re s ults from nuc le a r re a c tor a c c id e nts s hould not e xc e e d one -te nth of one p owe r p la nt op e ra tion s hould not e xc e e d one -te nth of one p e rc e nt (0.1 p e rc e nt) of the s um of p rom p t fa ta lity ris ks p e rc e nt (0.1 p e rc e nt) of the s um of c a nc e r fa ta lity ris ks re s ulting from othe r a c c id e nts to whic h m e m b e rs of the resulting from all other causes.

QHOs U.S. population are generally exposed.

IEFR 5x10 -7 /re a c tor-year* I LC F R 2x10 -6 /re a c tor-year*

• RM d e fin it io n  : RG 1 . 2 4 7

• RM d e fin it io n  : RG 1 . 2 4 7

• RP O b a s i s  : N U REG-0880, Re v. 1

• RP O b a s i s  : N U REG-0880, Re v. 1practical values r is k LE R F 1 0-5 /re a c tor-year LR F 1 0-6 /re a c tor-year C DF 1 0-4 /re a c tor-year f o r R ID M s urroga te s

• RM d e fin it io n  : RG 1 . 2 0 0* Applica nt -defined* RM d e fin it io n  : RG 1 . 2 0 0

• RP O b a s i s  : N U REG-1860, Ap p. D* H i s t o r y : S EC Y 0029* RP O b a s i s  : N U REG-1860, Ap p. D

• LMP ( N E I 1 8-04, Rev. 1, as endorsed in RG 1.233), uses the QHOs on a per plant basis te c hnology-in c lu s ive LW R-s p e c ific 7

Tentative ISG Overarching Principles

• The ISG provides guidance to NRC s taff reviewers

• Review s hould ens ure that the propos ed ris k metrics and as s ociated ris k performance objectives are fit -fo r-purpos e  :

• Form follows fu nc tion - Lo u is S u l l iva n

• Sta rt with the e nd in m ind - Stephen Covey

• Re vie w s h o u l d e n s u r e c o n s is t e n c y w it h C o m m is s io n p o l ic ie s a nd pre vious ly a c c e pte d ris k m e tric s a nd ris k pe rform a nc e objectives to help achieve an equivalent level of s afety

• Applic a nts m a y us e pre vious ly a c c e pte d ris k m e tric s a nd ris k pe rform a nc e obje c tive s , whe n a pplic a ble, whic h im prove s review efficiency

8 Te n t a t ive IS G H ig h- Level Concept

Ris k Me t r ic Us e s of the PRA A give n m e thod ology m a y b e us e d

• Meet regulations Ris k Performance to determine multiple risk metrics

• De m ons tra te tha t Com m is s ion O b je c t ive Me thodology expectations in policy statements have been achieved

• Sup p ort volunta ry ris k -inform e d Ris k Me t r ic

• Q u a l it a t ive a n d q u a n t it a t ive a p p l ic a t io n s s creening analys es

• P RA lo gic m o d e ls Propose a risk metric (or set of metrics) Ris k Performance

• Q u a n t it a t ive r is k-inform e d and associated risk performance target(s) O b je c t ive s upplemental evaluations tha t c olle c tive ly: o Bounding m e thods

• Approximates the total overall risk o S im p l ifie d m e t h o d s

o All ra d io lo gic a l s o u rc e s o All p la n t o p e ra t in g s t a t e sRis k Me t r ic Me thodology o All internal and external hazards

• Sup p orts the inte nd e d us e s of the PRA Ris k Performance

O b je c t ive 9 Regulations Related to Ris k Metrics

• Prbas iopos e d § 53.220 - s accidentsSafety criteria for licens ing -b a s is e ve nts othe r tha n d e s ign-

• Numerous references to propos ed § 53.220 t h ro u gh o u t p ro p o s e d Pa rt 53

• Remember that under Part 53, a commercial nuclear plant means a facility cons isting of one or more commercial nuclear reactors and as s ociated co -l o c a t e d s u p p o r t fa c il it ie s , in c l u d in g the c olle c tion of b uild ings , ra d ionuc lid e s ourc e s , a nd SSCs . Ac c ord ingly, c om p re he ns ive ris k metrics must include the ris ks from:

• Mu l t i-reactor event s equences

• No n -reactor event s equences

• Propos e d § 53.440(k) - Chemical hazards

• Refe lfects ofa tion of the chemi m e thod s fcalor a na l hazaryds ofzing the ri licens ed maters k of p e rm a ne nt iial to methods us ed to calnjury to the p ub lic d ue to the he a lculate th r a d io l o g ic a l r is k m e t r ic s  ?

• 10 CFR Pa rt 51 - Severe accident mitigation des ign alternatives (SAMDAs )

• Re q u ire d fo r DCs , MLs , CPs , OLs , a n d COLs

• No t re q u ire d fo r S DAs

• Rus e d ielation to rn the s a fis ke ty metr a na lics, methods to calys is ?culate ris k metrics, and ris k performance objectives

10 R i s k M e t r i c s a n d S AM D A An a l y s i s

N P V = (AP E + AO C + AO E + AO S C ) - COE

Proportiona l to popula tion dos e ris k

• For LWRs , proportiona l to CDF (p e r s o n -r e m / y)

• Wha t a bout non- LW R s  ?

Proportiona l to offs ite e c onom ic c os t ris k ($/y)

NP V = Net pres ent value of current ris k ($)

AP E = Pres ent value of averted public expos ure ($)

AO C = Pres ent value of averted offs ite property damage costs ($)

AO E = Pres ent value of averted occupational expos ure ($)

AO S C = Pres ent value of averted ons ite costs ($)

C OE = Cost of any enhancement implemented to reduce ris k ($)

11 Tentative ISG Review Proces s

Re vie w p roc e s s e s , c oord ina tion, a nd s c he d uling S t a ge 1 Ha s the a p p lic a nt id e ntifie d its no S t a ge 2

• In it ia l l ic e n s in g (C P, O L, DC , C O L, ML, S DA)inte nd e d us e s of the ris k m e tric s

• Re vis e d o r n e w ris k m e t ric o r ris k p e rfo rm a n c e and risk performance objectives?F St a rt o b je c t ive a ft e r in it ia l l ic e n s in g ye s

• Topica l re port - a p p lic a nt, ve nd or, ind us try Is the s e t of ris k m e tric s a nd ris k no

• Ind us try c ons e ns us s ta nd a rd performance objectives

• White paper A c om pre he ns ive?

ye s G Leverage previous Same reactor technology, ye s Is each risk metric concisely and no reviews (e.g., COL based u s e s , r is k m e t r ic s , a n d r is k Acce pta bleuna m biguous ly de fine d?

o n D C , S D A, o r ML)performance objectives as ye s H previously reviewed? B Does each risk performance no no objective have an acceptable Ris k m e t r ic s a n d r is k ye s technical basis?

performance objectives same ye s I a s t h e QHOs ?no C Has the applicant described the Cons is te nc y with Ris k m e t r ic s a n d r is k m e thodology to be us e d to no C o m m is s io n p o l ic y performance objectives ye s compute each risk metric?

e xpe c ta tions derived from the QHOs?

• ICs , BCs , a nd a s s um p tions  ?

no D

• Tre a tm e nt of unc e rta intie s  ?

Inform management ye s J E Acce pta ble Unacceptable

12 Other Topics

• Cha nge Provis ions

• Type of licens ing proces s :

• C Ps - attach as a permit condition

• MLs , O Ls , a n d C O Ls - attach as a licens e condition

• DC s  :

• No t c e rtific a tion inform a tion (a na logy: not Tie r 1 inform a tion unde r Pa rt 52)

• Inc lude in the DCD

• S D As - Inc lud e in the SDA

• Sub je c t to re le va nt c ha nge p rovis ions in p rop os e d Pa rt 53

• Intellectual Property

• The NRC s ta ff re c ognize s tha t a p p lic a nts , lic e ns e e s , a nd ind us try orga niza tion m a y invest cons iderable res ources in propos ing ris k metrics.

• Nfr o m P u b l ic Dis c l o s u r e .RR Offic e Ins truc tion LIC -204, Ha nd ling Re q ue s ts to Withhold Prop rie ta ry Inform a tion

• Te vh e Co m m ia lua tions is s in s up p ort ofo ns PRA P ro le gic yul Sta te m e n t (a tory d e c is ions s houl60 FR 42622; Ad b e a s ru gu s t 16, 1995)e a lis tic a s p r: PRa c tiAc a b le a nd a ppropria te s upporting da ta s hould be public ly a va ila ble for re vie w.

13 N e xt S t e p s

• Ts eparh e IS G o n s t a ff r e vie w o f a p p l ic a n t p r o p o s e d r is k m e t r ic s is a ate effort (i.e., the ISG will not be not included in the Part 53 rulemaking package).

• Goa l is to is s u e the ISG whe n Pa rt 53 is fina lize d .

• Pa r t 5 3 r u le m a kin g s c h e d u le  :

• Se p te m b e r 4, 2024: Se n d re vis e d p ro p o s e d Pa rt 53 to t h e Co m m is s io n

• Eofa r p u b lly Oc tob e ric c om m e nt p e r: Pu b lis h p riodop os e d Pa rt 53 in the Federal Register  ; s t a rt

• The ISG will be informed by:

• Com m e nts a nd d is c u s s ion d u ring this works hop

• Pu b lic c om m e nts on the p rop os e d Pa rt 53 (la te 2024 - e a rly 2025)

• Future works hops (to be de te rm ine d)

14 Ac r o n ym s a n d In it ia l is m s

BC b ound a ry c ond ition No n -LW R non- l ig h t -water reactor C DF core damage frequency N RC Nuclear Regulatory Commis s ion C FR Cod e of Fe d e ra l Re gula tions N RR Office of Nuclear Reactor Regulation COL combined licens e P OS p la nt op e ra ting s ta te CP c ons truc tion pe rm it P RA probabilistic risk assessment D AN U Divis ion of Ad va nc e d Re a c tors a nd Non- p o we r OL operating licens e P r o d u c t io n a n d Ut il iz a t io n Fa c il it ie s QHOs quantitative health objectives DC s t a n d a r d d e s ig n c e r t ific a t io n RM r is k m e t r ic FR Federal Register RG re gu la t o r y gu id e H C LP F high c onfid e nc e of low p rob a b ility of fa ilure RID M r is k-inform e d d e c is ion m a ke IC in it ia l c o n d it io n RP O ris k performance objective IEF R in d ivid u a l e a r l y fa t a l it y r is k S AM D A s evere accident mitigation des ign alternatives I LC F R in d ivid u a l l a t e n t c a n c e r fa t a l it y r is k S DA s ta nda rd de s ign a pprova l IS G in t e r im s t a ff g u id a n c e S MA s e is m ic m a r g in s a n a l ys is LE R F large early releas e frequency S RM staff requirements memorandum LR F large releas e frequency SSC s s truc ture s , s ys te m s , a nd c om p one nts LW R l ig h t -water reactor SSE s a fe s hutd own e a rthq ua ke ML m a nufa c turing lic e ns e

15 References

• S RM-S EC Y-23-0021, Sta ff Re q u ire m e n ts - S EC Y-23-0021 - P r o p o s e d Ru l e  : Ri s k-Inform e d , Te c hnology -Inclus ive Regulatory Framework For Advanced Reactors (RIN 3150 -AK31), Ma rc h 4, 2024, p u b lic we b s ite .

• S RMADAM-S EC YS Ac c e s s i-93-087, SEo n No. MCY-89-L051660712.102 - Im p le m e nta tion of the Sa fe ty Goa ls , June 15, 1990,

• RG 1.200, Rev. 1, Acceptability of Probabilis tic Ris k As s es s ment Res ults for Ris k -

Informed Activities, December 2020, public webs ite.

• RWGater 1.247, T ReactorRI RALis k -I - Acceptabinformed Alitycti ofv Pitires,obabi Marlis tich 2022, publc Ris k As s es s ment Ric webs ite.es ults for Non -Li g h t

• N U REG -0880, Re v. 1, Sa fe ty Go a ls fo r Nu c le a r Powe r Pla n t Op e ra tio n , Ma y 1983, ADAMS Ac c e s s io n No. ML071770230.

• N U REG -1 8 6 0 , Fe a s ib il it y S t u d y fo r a Ris k -Inform e d a nd Pe rform a nc e -Ba s e d Re g u l a t o r y Structure for Future Plant Licens ing, December 2007, public webs ite.

• S EC Y-13-0029, His tory of the Us e a nd Cons id e ra tion of the La rge Re le a s e Fre q ue nc y Metric by the U.S. Nuclear Regulatory Commis s ion, March 22, 2013, public webs ite.

16 Reliability & Operational Data Needs For Advanced Reactors

John C Lane PE Division of Risk Analysis Office of Nuclear Regulatory Research Workshop on Advanced Reactors Risk Metrics & Data July 18 2024 Advanced Reactor Operational Exp Relevance of Research & Operational Data a Needs

• Data will inform:

• Reactor design

• Reliability assessment

• Risk modeling

• NRC licensing

• Licensing basis event selection

• Classification of structures, systems and components

• Conformance with ASME/ANS NLWR PRA Standard data requirements

2 Component reliability raw data databases

• NaSCoRD-SNL-Sodium System & Component Reliability Database (developed from CREDO data)

• MOSARD-ORNL-Molten Salt Reactor Component Reliability Database (w/ EPRI)

• NDMAS-INL-Nuclear Data Management & Analysis System

• FFTF-PPNL-Passive Safety Testing & Metal Fuel Irradiation Database

• TREXR-ANL-Treat Experimental Relational Database & EBR-II Transient

& Fuels DBs

3 Gateway for Accelerated Innovation in Nuclear

4 Data Sources & Challenges in Modeling Risk

Early initiatives will likely Data challenges for passive combine system reliability

• Commercial power plant data (INPO-* Physical failure of components (e.g.,

IRIS database) pipe breaks, spurious actuation)

• Advanced reactor component

• Functional failure (e.g., unexpected, engineering & operational failure event unanalyzed situations) data

• Uncertainties in new system design,

• Expert/engineering judgement time-dependent boundary conditions

• Simulations

• Limited testing of operating condition

5 Planned Data Activities

Examine available existing Workshop (July 18 2024) advanced reactor OpE databases

Establish database templates, reporting criteria, and data Populate the new database with methods/procedures to operational data from prominent support risk modeling and advanced reactor designs regulatory oversight

6 NRC Preliminary Thoughts on Risk Metrics for Non-LW R s

NRC Working Group on Technology-Inclusive Risk Metrics

• Matt Humberstone (RES/DRA)

• Gerardo Martinez- Guridi (RES/DRA)

• Hanh Phan (NRR/DANU)

• Marty Stutzke (NRR/DANU Sr. Level Advisor)

• Jeffery Wood (RES/DRA)

Outline

• Structure for Discussing Risk Metrics for NLWRs

• Applicability of Existing Risk Metrics

• Desirable Characteristics for Risk Metrics

• Desirable Characteristics for Using Risk Metrics

• Some Considerations on Other Potential Approaches to Risk Metrics

• Basic Considerations on Risk Metrics Proposed by Industry

• Summary of Initial Thoughts: Proposed Approach to Risk Metrics

2 Structure for Discussing Risk Metrics for NLWRs

• The current regulatory structure and the three levels of PRA commonly applied to LWRs are used herein as the bases for discussing risk metrics for NLWRs

• Other approaches to developing these metrics are possible and are also briefly addressed

3 LWR PRA Structure

Initiating Prevention C o re Containment systems, event capabilities damage Severe accident progression, event Radiological release Offsite radiological consequences

Level 1 PRA Level 2 PRA Level 3 PRA

Reliability and core damage metrics: Radioactive release metrics: Consequence metrics:

• CDF

• LERF, LRF* Early fatalities

• Importance measures

• Characteristics of

• Latent cancer fatalities

• Performance indicators release, such as timing

• Dose

• Reliability targets and magnitude

• Economic impacts

Modeling approach: Modeling approach: Modeling approach:

• Probabilistic analysis (e. g.,

• Mechanistic analysis

• Mechanistic analysis of SAPHIRE, CAFTA) with (MELCOR, MAAP) for radionuclide transport and probability and frequency- accident progression and health effects based outputs source terms

• Incorporates probabilistic

• Frequency- based output evaluation (e.g., weather)

• MACCS commonly used4 Applications of Risk Metrics

Applications Where Regulatory Decision Making is Informed by Applications Where Regulatory Decision Making is Applicant/Licensee-Defined Risk Metrics and Models Informed by Staff-Defined Risk Metrics and Models

• Initial licensing (CP, OL, DC, SDA, ML, COL) applications

• Incidence Investigation Program (MD 8.3)

• 10 CFR 50.69 - Risk-Informed Categorization of SSCs

• Notice of Enforcement Discretion (NOED) (IMC-0410)

• 10 CFR 50.65 - Maintenance Rule

• Integrated Risk Informed Decision Making of

• RG 1.178 - Risk-Informed Inservice Inspection Emergent Issues (LIC-504)

• RG 1.175 - Risk-Informed Inservice Testing

• 10 CFR 50 App J, NEI 94-01, and EPRI TR -1009325 - Risk-Informed

• Integrated Risk Informed Decision Making for Integrated Leak Review Testing Licensing Reviews (LIC-206)

• RG 1.205 - Risk-Informed Fire Protection

• Reactor Oversight Process - Significance

• RG 1.177 - Risk-Informed Technical -Specification PRA Determination Process (SDP) (IMC-0609)

• JLD-ISG-2012 -01 and NEI 12-06 - Flex Strategies Risk Metrics* Generic Issues Program - GI screening is heavily

• Risk-Informing Emergency Planning informed by the RG 1.174 approach

• Risk-informing Security

• Accident Sequence Precursor (ASP) Program

• Mitigating System Performance Indicators (MSPIs)

• Etc.

• RG 1.174 - An Approach for Using PRA in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis

• LR-ISG-2006 -03 and NEI 05-01 - SAMDA analysis

• Reliability and Integrity Management Programs

• Etc. 5 Applicability of LWR Risk Metrics to NLWRs CDF LERF/LRF Consequence Metrics LW R Applicable Applicable to Technology Technology N LW R NLWRs w/CD inclusive inclusive Not Applicable to Other NLWRs F o r LW R s  :

• CDF measures accident prevention and is a surrogate for the latent fatality QHO

• LERF measures accident mitigation and is a surrogate for the early fatality QHO

6 Challenges with Consequence (Radiological Health-Effects) Metrics

• Technical

• Health effects metrics are obtained by combining the characteristics of a plant with the conditions of the plant s location, such as the number of people surrounding the plant, the peoples spatial distribution, and the weather

• It is difficult to relate health effects metrics to the elements (e.g., hardware components and human errors) of a Level-1 PRA and a Level-2 PRA to evaluate the importance measures of each element

• Large uncertainties

7 Challenges with Consequence (Radiological Health-Effects) Metrics (cont d)

• Perception

• Possible perception of additional burden on NLWR applicants compared to LW R s

• Possible negative perceptions (e.g., results reported in terms of number of fatalities)

• Increased review times

8 Desirable Characteristics for Risk Metrics

• A risk metric is a measure that is used to express the risk i nte re st quantity of

• A risk metric can be used to illustrate compliance with safety goals

• A risk metric can be used in performing risk characterization

• Risk characterization combines the major components of risk (hazards, consequences, frequency, and probability), along with quantitative estimates of risk, to give a combined and integrated risk perspective (i.e., a risk profile)

• A risk metric can be used to derive risk indicators

• An example of a risk indicator is conditional core damage probability (CCDP)

• Importance measures is an important example because:

• They provide relative and absolute measures of the importance of PRA elements to plant risk s

• They are used in many regulatory programs involving RIDM

• Characterization of the uncertainty of risk metric is possible

9 Desirable Characteristics for Using Risk Metrics

• The process for calculating a risk metric is transparent

• Risk metrics for accident prevention and accident mitigation would be useful (as described on SECY-89-102)

• Risk metrics that minimize changes to the current regulatory structure

• It allows to maximize consistency with current risk metrics (CDF and LERF/LRF)

• Risk metrics that minimize challenges to relate them to safety objectives, such as the QHOs

10 Desirable Characteristics for Using Risk Metrics

( c o n t d )

• Risk metrics that can be applied to the lifetime of an NLWR

• Risk metrics that avoid challenges associated with health-effect metrics

• Risk metrics that can be applied to all sizes (i.e., power generation) of reactors

11 Risk Metrics for Accident Prevention for NLWRs

• When core damage is applicable (e. g., for fast reactors cooled by liquid metals):

• CDF is applicable to these NLWRs

• Definition of core damage may be specific to each reactor technology

• When core damage is not applicable:

• Core damage for LWRs implies the failure of the LWR fuel cladding, which is the initial confinement of radioactive material

• Accordingly, our initial tendency is to define a frequency of failure of initial confinement of radioactive material

• Defining failure of initial confinement is specific to each reactor technology

• It may be somewhat challenging to define this failure for each reactor technology

12 Some Considerations on Other Potential Approaches to Risk Metrics for NLWRs

• Technology- inclusive risk metrics

• LERF could be a possibility

• Risk metrics for accident prevention could be missing since they are technology-specific

• It would require major modifications to current regulatory structure or developing a new regulatory structure for NLWRs

• Simplified approach that is not related to the LWR PRA levels

• It may be difficult to calculate quantitative risk metrics that can be used to compare with the safety objectives, such as the QHOs

• It may be difficult to generate derived risk indicators, such as importance measures, which are used in many regulatory programs involving RIDM

13 Basic Considerations on Risk Metrics Proposed by Industr y

• NRC is open to consider the proposed risk metrics

• It also seems desirable to establish:

• Set of unified metrics between industry and NRC (as much as possible)

• Set of unified metrics that would be appropriate for use throughout plant lifetime

14 Summary of Initial Thoughts:

Proposed Approach to Risk Metrics for NLWRs

• For accident prevention:

• Use CDF whenever core damage is applicable

• Use new metrics when core damage is not applicable (e.g., frequency of failure of initial confinement of radioactive material)

• For accident mitigation, LERF is technology inclusive

• Consequence metrics are technology inclusive, but there are challenges associated with them

• Desirable attributes for risk metrics and for using the metrics are proposed

15 Acronyms and Abbreviations

A d v.Advanced ASP Accident Sequence Precursor CCDP Conditional Core Damage Probability CDF Core Damage Frequency CFR Code of Federal Regulations COL Combined License CP Construction Permit DANU (NRC) Division of Advanced Reactors and Non-Power Production and Utilization Facilities DC Design Certification EPRI Electric Power Research Institute IMC Inspector Manual Chapter ISG Interim Staff Guidance LERF Large Early Release Frequency LRF Large Release Frequency LW R Light-Water Reactor MACCS MELCOR Accident Consequence Code System

16 Acronyms and Abbreviations (cont d)

MAAP Modular Accident Analysis Program MD Management Directive ML Manufacturing License NEI Nuclear Energy Institute N LW RNon-Light -Water Reactor NOED Notice of Enforcement Discretion NRC Nuclear Regulatory Commission RIDM Risk-Informed Decision Making NRR (NRC) Office of Nuclear Reactor Regulation OL Operating License OpE Operating Experience PRA Probabilistic Risk Assessment QHO Qualitative Health Objective RES (NRC) Office of Nuclear Regulatory Research RG Regulatory Guide

17 Acronyms and Abbreviations (cont d)

Rx Reactor SAMDA Severe Accident Mitigation and Design Alternatives SDA Standard Design Approval SSC Structures, Systems, and Components

18 Backup Slides

19 Early Studies, Events, and Policies related to Risk

Individual Plant Examinations (IPE) for Severe Accident Vulnerabilities TMI Accident (GL 88-20, NUREG-1560) PRA Policy Severe Accident Shutdown / Statement Policy Statement Low Power

(NUREG-1449) 1980 1990

1975 1985 1995

AT W S Indian Point Safety Goal IPE of (NUREG-0460) & Zion Policy Statement External Events Probabilistic (GL 88-20 supp. 4, Safety Studies NUREG-1742)

Station Blackout Severe Accident Risks Reactor Safety Study (NUREG-1032) (NUREG-1150)

( WA S H-1400)

20 1986 Policy Statement: Safety Goals for the Operations of Nuclear Power Plants

Qualitative Safety Goals: Quantitative Health Objectives (QHOs):

• Individual members of the public

• The risk to an average individual in the vicinity1 of a should be provided a level of nuclear power plant of prompt fatalities that might protection from the consequences of result from reactor accidents should not exceed one-nuclear power plant operation such tenth of one percent (0.1 percent) of the sum of that individuals bear no significant prompt fatality risks resulting from other accidents additional risk to life and health. to which members of the U.S. population are

• Societal risks to life and health from generally exposed.

nuclear power plant operation should

• The risk to the population in the area2 near a nuclear be comparable to or less than the power plant of cancer fatalities that might result from risks of generating electricity by viable nuclear power plant operation should not exceed competing technologies and should one-tenth of one percent (0.1 percent) of the sum of not be a significant addition to other cancer fatality risks resulting from all other causes.

societal risks.

1Within 1 mile of the nuclear power plant site boundary; 2Within 10 miles of the plant site 21 Background on Risk Metrics Policy and Histor y

• NRC has a long history of integrating risk into our decision-making

• Sug gested reading:

22 Risk Objective References

• SRM on SECY- 89- 102, Implementation of Safety Goals (ML003707881)

• Establishes objectives for CDF, LRF, and CCFP

• SECY(ML003761015)- 93- 138, Recommendation on Large Release Definition

• Recommend terminating further work to develop large release definition

• SECYReactors- 10- 0121, Modifying the Risk -Informed Regulatory Guidance for New (ML102230076)

• SRM on SECY-reaffirms existing subsidiary risk goals10-0121 ( ML110610166) disapproved staff s recommendation,

• N U R EG -1860, Feasibility Study for a RIPB Regulatory Structure for Future Plant Licensing

• See Appendix D - Derivation of Risk Surrogates for LWRs

23 Risk vs Risk Metrics

• Risk Triplet:

1. What can go wrong?

2. How likely is it?

3. What are the consequences?

• Risk Metric - a measure that is used to express the risk quantity of interest (from NUREG- 2122 - Glossary of Risk-Related Terms)

• For example, for LWRs:

• Core damage frequency (CDF)

• Large early release frequency (LERF)

• Risk metrics could be used to address all parts of the risk triplet.

24 Risk Metric Terms

• Subsidiary Risk Metric or Surrogate Risk Metric -metric that can provide indication of meeting a desired ultimate risk an alternative risk objective, e. g., QHOs

• For example, CDF is a surrogate risk metric for individual latent cancer fatality risk

• A surrogate is typically developed at a lower modeling level and provides a measure of margin to the desired risk goal

• Risk Performance Objective is used during RIDM to gauge plant safety- a preestablished, indicative value that

• For example, CDF < 1E-4 / y e a r.

• Provides a reference point for risk metric results.

• Typically, not a strict acceptance limit.

• Sometimes also referred to as risk goal or risk criterion.

25 LWR PRA Levels

• Level 1: Core damage frequency analysis

• It calculates the core damage frequency given the design and operation of the plant.

• Level 2: Radionuclide release frequency analysis

• It takes the results of the Level(accident sequences resulting in core -1 PRA damage) as input and produces frequencies of radioactivity releases as output.

• Level 3: Consequence analysis

• It takes the results of the Level 2 PRA as input and produces offsite consequences (health effects, economic consequences) as output.

S o u rce o f tex t : N U REG-2122

26 Structure of Level 1, Level 2, Level 3 PRA (for LWRs)

Figure from System Modeling Techniques for PRA (P -200) by INL.

Subsidiar y Risk Objectives

In NRCs risk-informed decision-making for operating reactors (LWRs):

• A core damage frequency (CDF) of < 10 -4 /Rx-year is used as a surrogate for the latent cancer fatality QHO.

• A large early release frequency (LERF) of < 10 -5 /Rx-year is used as a surrogate for the individual prompt fatality QHO.

28 Subsidiar y Risk Objectives (cont d)

In 1990, the Commission established three risk metrics for new reactors (Advanced LWRs (ALWRs)) and associated quantitative goals:

• Core Damage Frequency (CDF) < 1x 10-4/year - A measure of overall safety performance in prevention of severe accidents

• Large Release Frequency (LRF) < 1x 10-6/year - A measure of prevention of significant offsite consequences

• Conditional Containment Failure Probability (CCFP) < 0.1 - A measure of the capability of design to mitigate a severe accident

29 Examples of Previously Used Risk Metrics and Associated Performance Objectives.

Risk Metric and Performance Objective Applicability Definition Notes IEFR: individual early Technology RG 1.247

• First quantitative health objective (QHO) in the fatality risk Inclusive Commissions safety goal policy statement; NUREG-0880 provides the technical rationale.

mean* IEFR 5x10-7 /plant-year ILCFR: individual latent cancer fatality risk Technology RG 1.247

• Second QHO in the Commissions safety goal policy Inclusive statement; NUREG- 0880 provides the technical rationale.

mean* ILCFR 2x10-6 /plant-year LRF: large release frequency Technology Staff has not defined

• SRM on SECY 016 established this performance inclusive LRF; practice has been to objective.

mean* LRF allow Part 52 applicants

• LRF applies to all current and future designs (SRM -SECY-10-6 /reactor-year to define LRF. 98- 102).

• LW Rs transition from LRF to LERF at initial fuel load (SRM -

SECY 0081)

• SECY 0029 provides a history of LRF.

CDF: core-damage frequency LW Rs and NLW Rs RG 1.200

• Surrogate for the ILCFR QHO; NUREG -1860, Vol. 2, App. D susceptible to core provides the technical rationale for LW Rs.

mean* CDF damage

• Measure of plants accident prevention capability.

10-4 /reactor-year

• Does not address non- core sources or multi -reactor accidents.

LERF: large early release frequency Technology RG 1.200

• Surrogate for the IEFR QHO and LRF; NUREG -1860, Vol.

inclusive 2, App. D provides the technical rationale for LW Rs.

mean* LERF

• Measure of plants accident mitigation capability.

10-5 /reactor-year

• Does not address non- core sources or multi -reactor accidents.

• LERF sequences have been identified qualitatively for LW Rs (e.g., Table 2- 2.8-9 in ASME/ANS RA- Sa-2009, as endorsed in RG 1.200).

• The term mean refers to the mean of the parametric uncertainty distribution of the risk metric. Modeling uncertainties and c ompleteness uncertainties also should be considered in risk -informed decision making (NUREG -1855). 30 Impressions of LMP Approach Strengths:

• Technology-inclusive

• Useful for initial licensing

• It is being used by applicants and potential applicants Challenges:

• How will the approach be leveraged for other RI programs?

• RG 1.174

• Maintenance rule

• Significance Determination Process

• Interface of LMP with industry consensus standards

• Seismic design process, reliability integrity management, RI fire protection

31