ML22130A727
| ML22130A727 | |
| Person / Time | |
|---|---|
| Issue date: | 05/20/2022 |
| From: | Bhagwat Jain NRC/NRR/DORL/LPL4 |
| To: | |
| Jain B, NRR/DORL/LPL4 | |
| References | |
| Download: ML22130A727 (28) | |
Text
Advisory Committee on Reactor Safeguards Digital Instrumentation & Controls Subcommittee Briefing May 20, 2022 ExpansionofCurrentPolicyto AddressPotentialCommonCauseFailuresin DigitalInstrumentationandControlSystems
TechnicalStaffPresenters
- SamirDarbali-ElectronicsEngineer,NRR/DEX
- NorbertCarte-SeniorElectronicsEngineer,NRR/DEX
- StevenAlferink-ReliabilityandRiskAnalyst,NRR/DRA DigitalI&CProjectManagers
- BhagwatJain-SeniorProjectManager,NRR/DORL
- MichaelMarshall-SeniorProjectManager,NRR/DORL 2
Working Group Members
- NRR/DEX
- NorbertCarte
- SamirDarbali
- NRR/DRA
- StevenAlferink
- ShilpVasavada
- SunilWeerakkody
- NRR/DSS
- CharleyPeabody 3
- AdditionalNRR/DEX andDORLSupport
- WendellMorton
- MingLi
- MichaelMarshall
- KhoiNguyen
- DavidRahn
- RichardStattel
- MichaelWaters
- SteveWyman
- NRR/DORL
- BhagwatJain
- SheldonClark
- RES/DE
- SergiuBasturescu
Presentation Outline 4
- IntroductionandKeyMessages
- Background
- SubjectandPurpose
- ProposedExpandedPolicy
- CurrentPath
- RiskInformedPath
- IndustryProposal
- StatusofDraftSECYPaperandNextSteps
Introduction
- SRMSECY93087directsthat,iftheD3 assessmentshowsthata postulatedCCFcoulddisableasafetyfunction,thenadiversemeansbe providedtoperformthatsafetyfunctionoradifferentfunction
- Diversemeansmayincludemanualactions
- Thecurrentpolicydoesnotallowfortheuseofariskinformed approachtodeterminespecificcircumstancesthatwouldnotrequire adiversemeansforaddressingDI&CCCF
- TheSECYpaperwillproviderecommendedlanguageforanexpanded policy,whichallowsriskinformedapproachestoaddressDI&CCCF 5
Key Messages
- TheexpandedpolicywillencompassthecurrentpointsofSRMSECY93 087(withclarifications)andexpandtheuseofriskinformed approaches
- Anyuseofriskinformedapproacheswillneedtobeconsistentwiththe SafetyGoalPolicyStatement,PRAPolicyStatement,andSRMSECY98 0144
- ThecurrentDI&CCCFpolicywillcontinuetoremainavalidoptionfor licenseesandapplicants 6
Background - Early Concerns with CCF
- EarlyconcernswithCCF
- CCFhasbeenanNRCconcernsincethemid1960s
- Intheearly1990s,theintroductionofDI&Cbecameaconcernasanewsource forintroducingCCF,asexplainedinSECY91292
- CurrentDI&CCCFpolicy
- TheNRCscurrentDI&CCCFpolicyisexpressedinvariousdocuments,including SRMSECY93087;SECY180090;andBTP719,Revision8
- CurrentstateofDI&Cinthenuclearpowerindustry
- Designdevelopmentpracticesandqualityassurancetoolshaveevolved
- DI&CCCFsremainsaseriousareaofconcern 7
Background - Risk-Informing DI&C CCF
- Increaseduseofriskinformeddecisionmaking
- ThestaffisfollowingthePRAPolicyStatementandSRMSECY98144toexpand riskinformeddecisionmaking
- ModernizingtheDI&Cregulatoryinfrastructure
- SRMSECY160070approvedimplementationofthestaffsintegratedaction plantomodernizetheNRCsDI&Cregulatoryinfrastructure
- Thestaffissuedguidanceonriskinformed,gradedapproachestoaddress DI&C CCFforlowsafetysignificantsafetysystems(e.g.,BTP719andRIS200222, Supplement1)
- Thestaffbelievesthisisanappropriatetimetoexpandthecurrentpolicyon DI&CCCFtoincludetheuseofriskinformedapproaches 8
SECY Paper Subject and Purpose
- SUBJECT
- ExpansionofCurrentPolicytoAddressPotentialCommonCause FailuresinDigitalInstrumentationandControlSystems
- PURPOSE
- ProvidetheCommissionarecommendationonexpandingthe currentpolicytoincludetheuseofriskinformedapproachesfor addressingDI&CCCFs
- Therecommended expandedpolicywillencompassthecurrent positionsinSRMSECY93087andtheuseofriskinformed approachestodeterminetheappropriatelevelofdefenseindepth anddiversitytoaddressDI&CCCF 9
Proposed Expanded Policy to Address DI&C CCF
- AsingleexpandedpolicythatencompassesthecurrentpositionsinSRM SECY93087andprovidesforriskinformedapproachestoaddressDI&C CCF
- Theexpandedpolicyincludes:
1)
Positionsinpoints1,2,and3ofSRMSECY93087withappropriateclarifications andcorrectionsfromSECY180090 2)
Languageinpoint4ofSRMSECY93087withappropriateclarifications 3)
Theadditionofriskinformedapproachestopoints2and3ofSRMSECY93087
- Theexpandedpolicyprovidesfor:
- 1) Thedeterministicdemonstrationofadequatediversity
- 2) Riskinformedapproaches 10
Proposed Expanded Policy to Address DI&C CCF 11 Point 2 Risk-Informed Approach Point 3 Risk-Informed Approach Point 2 SRM-SECY-93-087, Point 2 (Clarified)
Point 3 SRM-SECY-93-087, Point 3 (Clarified)
Current Path Risk-Informed Path Proposed Expanded Policy to Address Digital I&C CCF The Current Path allows for the use of best estimate analysis and diverse means to address a potential DI&C CCF.
The Risk-Informed Path allows for the use of risk-informed approaches and other design techniques or defensive measures other than diversity to address a potential DI&C CCF.
Point 4 SRM-SECY-93-087, Point 4 (Clarified)
Point 1 SRM-SECY-93-087, Point 1 (Clarified)
CurrentPath 12
Current Path
- ThecurrentpolicycontinuestobeaviableoptiontoaddressDI&CCCF
- ThecurrentfourpointsinSRMSECY93087willremainasaviablepath tolicenseesandapplicants:
- Point1-assessthedefenseindepthanddiversityoftheproposedI&Csystemto demonstratethatvulnerabilitiestocommonmodefailureshaveadequatelybeenaddressed.
- Point2-analyzeeachpostulatedcommonmodefailureforeacheventthatisevaluatedin theaccidentanalysissectionofthesafetyanalysisreport(SAR)usingbestestimatemethods demonstrateadequatediversitywithinthedesignforeachoftheseevents.
- Point3-Ifapostulatedcommonmodefailurecoulddisableasafetyfunction,thenadiverse meansshallberequiredtoperformeitherthesamefunctionoradifferentfunction.
- Point4-Asetofdisplaysandcontrolslocatedinthemaincontrolroomshallbeprovidedfor manual,systemlevelactuationofcriticalsafetyfunctionsandmonitoringofparametersthat supportthesafetyfunctions
- SECY180090clarifiestheapplicationofthefourSRMSECY93087 pointsandprovidesguidingprinciplesthatwereusedinthe developmentofBTP719,Rev.8 13
Proposed Expanded Policy - Current Path 14 Point 1 SRM-SECY-93-087, Point 1 (Clarified)
Point 2 Risk-Informed Approach Point 3 Risk-Informed Approach Point 2 SRM-SECY-93-087, Point 2 (Clarified)
Point 3 SRM-SECY-93-087, Point 3 (Clarified)
Current Path Risk-Informed Path Proposed Expanded Policy to Address Digital I&C CCF Point 4 SRM-SECY-93-087, Point 4 (Clarified)
The Path allows for the use of best estimate analysis and diverse means to address a potential DI&C CCF.
Clarifying the Current Policy Language
- Replacingcommonmodefailurewithcommoncausefailure
- ThecurrentlanguageinSRMSECY93087points1,2and3usestheterm commonmodefailurewhentheintentandimplementationiscommoncause failure
- Addingfacilitywhereappropriate
- ThecurrentlanguageinSRMSECY93087points1and2focusesonthe proposedI&Csystem,whentheNRCsconcernisonthedefenseindepthand diversityofthefacilityincorporatingtheDI&Csystem
- Addingdefenseindepthwhereappropriate
- ThecurrentlanguageinSRMSECY93087point2focusesondemonstrating adequatediversity,whentheintentandimplementationincludesdefensein depth 15
RiskInformedPath 16
Guiding Principles for Implementation
- Theexpandedpolicywillnotconflictwithexistingregulatory requirements
- Arulechangeorexemptionwillnotberequiredtoimplementit
- ExpandingtheDI&CCCFpolicywillbeconsistentwiththeagencys1995 PRAPolicyStatement,SRMSECY980144,andcurrentfocusforthe agencytoexpandriskinformeddecisionmaking
- ImplementationoftheexpandedDI&CCCFpolicywillcontinueto providereasonableassurance ofadequateprotection andsafety 17
Guiding Principles for Implementation (contd.)
- Applicantswillneedtoaddressallfiveprinciplesofriskinformed decisionmaking,aslistedinRG1.174
- AsystematicapproachisusedtoevaluateDI&Cfailurecausesduring operationandmaintenance,includinginappropriatesoftwarebehavior
- APRAusedforriskinformedapproachesneedstobetechnically acceptable(e.g.,meetstheguidanceinRG1.200)andincludean effectivePRAconfigurationcontrolandfeedbackmechanism 18
19 Point 1 SRM-SECY-93-087, Point 1 (Clarified)
Point 2 Risk-Informed Approach Point 3 Risk-Informed Approach Point 2 SRM-SECY-93-087, Point 2 (Clarified)
Point 3 SRM-SECY-93-087, Point 3 (Clarified)
Current Path Risk-Informed Path Proposed Expanded Policy to Address Digital I&C CCF Point 4 SRM-SECY-93-087, Point 4 (Clarified)
Proposed Expanded Policy - Risk-Informed Path The Risk-Informed Path allows for the use of risk-informed approaches and other design techniques or defensive measures other than diversity to address a potential DI&C CCF.
SRM-SECY-93-087, Points 1 and 4 in the Risk-Informed Path
- SRMSECY93087,Point1:
- ItdoesnotprecludetheuseofriskinformedapproachfortheD3evaluation
- Existingpolicyandguidancesupportagradedapproachandapplyingalevelof rigorfortheD3assessmentcommensuratewiththesafetysignificanceofthe proposedDI&Csystemorcomponent
- SRMSECY93087,Point4:
- Regulationseffectivelyrequirediverseandindependentdisplaysandcontrols
- Riskinformedapproachtopoint4wouldnotprovidenoticeablebenefits 20
Risk-Informing the positions in SRM-SECY-93-087 Point2
- Currentapproachfocusesonconsequences
- Thestaffconsidersthisanappropriateareaforriskinformingthe evaluationofpostulatedDI&CCCFs
- Ariskinformedapproachcanidentifyinitiatorsorscenarioswherelack ofDI&Cdiversitydoesnotcompromisesafety 21
Risk-Informing the Positions in SRM-SECY-93-087 Point3
- Currentapproachonlyprovidesonewayofaddressingundesirable outcomes(i.e.,diversemeans)
- Thestaffconsidersthisanappropriateareaforevaluatingdesign measuresotherthandiversitytoreducetheriskfromaDI&CCCF 22
Benefits of Risk-Informed Approaches
- Riskinformedapproachescanprovideflexibilitytoaddress DI&CCCF andareconsistentwiththePRAPolicyStatement
- Riskinformedapproachescouldsupportagradedapproachin determiningthedegreeofdiversitythatisneeded
- PRAmodelscouldbeusedtosystematicallyassesstheneedtoreduce theriskintroducedbytheDI&Csystem
- RiskinformedapproachescanhavedifferentlevelsofPRAuse 23
Proposed Expanded Policy to Address DI&C CCF 24 Point 2 Risk-Informed Approach Point 3 Risk-Informed Approach Point 2 SRM-SECY-93-087, Point 2 (Clarified)
Point 3 SRM-SECY-93-087, Point 3 (Clarified)
Current Path Risk-Informed Path Proposed Expanded Policy to Address Digital I&C CCF The Current Path allows for the use of best estimate analysis and diverse means to address a potential DI&C CCF.
The Risk-Informed Path allows for the use of risk-informed approaches and other design techniques or defensive measures other than diversity to address a potential DI&C CCF.
Point 4 SRM-SECY-93-087, Point 4 (Clarified)
Point 1 SRM-SECY-93-087, Point 1 (Clarified)
Key Messages
- TheexpandedpolicywillencompassthecurrentpointsofSRMSECY93 087(withclarifications)andexpandtheuseofriskinformed approaches
- Anyuseofriskinformedapproacheswillneedtobeconsistentwiththe SafetyGoalPolicyStatement,PRAPolicyStatement,andSRMSECY98 0144
- ThecurrentDI&CCCFpolicywillcontinuetoremainavalidoptionfor licenseesandapplicants 25
Status of Draft SECY Paper and Next Steps
- ThedraftSECYiscurrentlybeingdeveloped
- ApublicoutreachmeetingisplannedforJune2022
- ThestaffexpectstosendtheSECYpapertotheCommissioninJuly2022
- Uponapprovalofanexpandedpolicy,thestaffwillproceedtoupdate theimplementationguidanceinBTP719 26
Questions?
BTP BranchTechnicalPosition CCF CommonCauseFailure D3 DefenseinDepthandDiversity DI&C DigitalInstrumentationandControl ESFAS EngineeredSafetyFeaturesActuationSystem GDC GeneralDesignCriteria IAP IntegratedActionPlan I&C Instrumentationandcontrol MP ModernizationPlan NEI NuclearEnergyInstitute Acronyms NRC NuclearRegulatoryCommission OEDO OfficeoftheExecutiveDirectorforOperations PRA ProbabilisticRiskAssessment RG RegulatoryGuide RIS RegulatoryIssueSummary RPS ReactorProtectionSystem SAR SafetyAnalysisReport SECY CommissionPaper SRM StaffRequirementsMemorandum