ML22140A049
| ML22140A049 | |
| Person / Time | |
|---|---|
| Issue date: | 05/20/2022 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Jain, B, NRR/DORL/LPL4 | |
| References | |
| Download: ML22140A049 (29) | |
Text
Advisory Committee on Reactor Safeguards Digital Instrumentation & Controls Subcommittee Briefing May 20, 2022 ExpansionofCurrentPolicy RegardingPotentialCommonCauseFailuresin 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
- StatusofDraftSECYPaperandNextSteps
Introduction
- NuclearpowerplantscontinuetoinstalldigitalI&Ctechnology
- Increasedreliabilityandsafetybenefits
- Canintroducenewtypesoftypesofpotentialsystematic,nonrandom,concurrentfailuresof redundantelements(i.e.,CCFs)
- SRMSECY93087directsthat,iftheD3 assessmentshowsthatapostulatedCCF coulddisableasafetyfunction,thenadiversemeansbeprovidedtoperformthat safetyfunctionoradifferentfunction
- Diversemeansmayincludemanualactions
- Thecurrentpolicydoesnotallowfortheuseofariskinformedapproachtodeterminespecific circumstancesthatwouldnotrequireadiversemeansforaddressingDI&CCCFs
- ThestaffisdevelopingaSECYpaperthatwillproviderecommendedlanguagefor anexpandedpolicy,whichallowsgreateruseofriskinformed approachestoaddressDI&CCCFs 5
Key Messages
- Theexpandedpolicywillencompassthecurrentpointsof SRMSECY93087(withclarifications)andexpandtheuseof riskinformedapproaches
- Anyuseofriskinformedapproacheswillbeexpectedtobeconsistent withtheSafetyGoalPolicyStatement,PRAPolicyStatement,andSRM SECY980144
- ThecurrentDI&CCCFpolicywillcontinuetoremainavalidoptionfor licenseesandapplicants 6
Background - Early Concerns with CCFs
- EarlyconcernswithCCFs
- CCFshavebeenanNRCconcernsincethemid1960s
- Intheearly1990s,theintroductionofDI&Cbecameaconcernasanewsource forintroducingCCFs,asexplainedinSECY91292
- CurrentDI&CCCFpolicy
- TheNRCscurrentDI&CCCFpolicyisexpressedinvariousdocuments,including SRMSECY93087;SECY180090;andBTP719,Revision8
- CurrentstateofDI&Cinthenuclearpowerindustry
- Designdevelopmentpracticesandqualityassurancetoolshaveevolved
- DI&CCCFsremainsaseriousareaofconcern 7
Background - Use of Risk-Information
- Increaseduseofriskinformeddecisionmaking
- ThestaffisfollowingthePRAPolicyStatementandSRMSECY98144toexpand riskinformeddecisionmaking
- ModernizingtheDI&Cregulatoryinfrastructure
- SRMSECY160070approvedimplementationofthestaffsintegratedaction plantomodernizetheNRCsDI&Cregulatoryinfrastructure
- Thestaffissuedguidanceonriskinformed,gradedapproachestoaddress DI&C CCFsforlowsafetysignificantsystems(e.g.,BTP719andRIS200222, Supplement1)
- Thestaffbelievesthisisanappropriatetimetoexpandthecurrentpolicyon DI&CCCFstoincludetheuseofriskinformedapproaches 8
SECY Paper Subject and Purpose
- SUBJECT
- ExpansionofCurrentPolicyRegardingPotentialCCFsinDI&CSystems
- PURPOSE
- ProvidetheCommissionarecommendationonexpandingthe currentpolicytoincludetheuseofriskinformedapproachesfor addressingDI&CCCFs
- Therecommended expandedpolicywillencompassthecurrent positionsinSRMSECY93087andtheuseofriskinformed approachestodeterminetheappropriatelevelofdefenseindepth anddiversitytoaddressDI&CCCFs 9
Proposed Expanded Policy to Address DI&C CCFs
- Asingleexpandedpolicythatencompassesthecurrentpositionin SRMSECY93087andprovidesforriskinformedapproachestoaddress DI&CCCFs
- Theexpandedpolicyincludes:
1)
Positioninpoints1,2,and3ofSRMSECY93087withappropriateclarifications andcorrectionsfromSECY180090 2)
Positioninpoint4ofSRMSECY93087withappropriateclarifications 3)
Theadditionofriskinformedapproachestopoints2and3ofSRMSECY93087
- Theexpandedpolicyprovidesfor:
- 1) Thedeterministicdemonstrationofadequatediversity
- 2) Riskinformedapproaches 10
Proposed Expanded Policy to Address DI&C CCFs 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 CCFs 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 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&CCCFs
- ThecurrentfourpointsinSRMSECY93087willremainasaviablepath tolicenseesandapplicants:
- Point1-assessthedefenseindepthanddiversityoftheproposedI&Csystemto demonstratethatvulnerabilitiestocommonmodefailureshaveadequatelybeenaddressed.
- Point2-analyzeeachpostulatedcommonmodefailureforeacheventthatisevaluatedin theaccidentanalysissectionofthesafetyanalysisreport(SAR)usingbestestimatemethods demonstrateadequatediversitywithinthedesignforeachoftheseevents.
- Point3-Ifapostulatedcommonmodefailurecoulddisableasafetyfunction,thenadiverse meansshallberequiredtoperformeitherthesamefunctionoradifferentfunction.
- Point4-Asetofdisplaysandcontrolslocatedinthemaincontrolroomshallbeprovidedfor manual,systemlevelactuationofcriticalsafetyfunctionsandmonitoringofparametersthat supportthesafetyfunctions
- SECY180090providesguidingprinciplesfortheapplicationofpolicy, whichwereusedinthedevelopmentofBTP719,Revision8 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 CCFs Point 4 SRM-SECY-93-087, Point 4 (Clarified)
The Current 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
- ThecurrentlanguageinSRMSECY93087points1,2,and3usestheterm commonmodefailurewhentheintentandimplementationiscommoncause failure
- Addingfacilitywhereappropriate
- ThecurrentlanguageinSRMSECY93087points1and2focusesonthe proposedI&Csystem,whentheNRCsconcernisonthedefenseindepthand diversityofthefacilityincorporatingtheDI&Csystem
- Addingdefenseindepthwhereappropriate
- ThecurrentlanguageinSRMSECY93087point2focusesondemonstrating adequatediversity,whentheintentandimplementationincludes defenseindepth 15
RiskInformedPath 16
17 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 CCFs 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 measures other than diversity to address a potential DI&C CCF
SRM-SECY-93-087, Point 1 in the Risk-Informed Path
- Point1doesnotprecludetheuseofriskinformedapproachesforthe D3assessment
- Existingpolicyandguidancesupportagradedapproachandapplyinga levelofrigorfortheD3assessmentcommensuratewiththesafety significanceoftheproposedDI&Csystemorcomponent 18
SRM-SECY-93-087, Point 4 in the Risk-Informed Path
- Point4isconsistentwithcurrentregulationsthateffectivelyrequire diverseandindependentdisplaysandcontrols
- 10CFR50.55a(h)incorporatesbyreferenceIEEEStd279andIEEEStd6031991,which aremandatoryfornuclearpowerplantslicensedsince1971
- IEEEStd279,clauses4.1,4.17,and4.20,andIEEEStd6031991,clauses4.10,5.6.1, 6.2.1,6.2.2,and6.2.3containrequirementsrelatedtoautomaticallyinitiatedprotective actions,manualcontrols,andinformationdisplays
- 10CFRPart50,AppendixA,GeneralDesignCriterion22states, [d]esign techniques, suchasfunctionaldiversityordiversityincomponentdesignandprinciplesofoperation, shallbeusedtotheextentpracticaltopreventlossoftheprotectionfunction.
- Riskinformedapproachtopoint4wouldnotprovideappreciable benefits 19
SRM-SECY-93-087, Point 2 in the Risk-Informed Path
- Currentapproachfocusesonconsequences
- Thestaffconsidersthisanappropriateareaforriskinformingthe evaluationofpostulatedDI&CCCFs
- Thestaffsgoalisthatriskinformedapproacheswillbeconsistentwith allfiveprinciplesofriskinformeddecisionmaking,aslistedinRG1.174 20
SRM-SECY-93-087, Point 3 in the Risk-Informed Path
- Currentapproachonlyprovidesonewayofaddressingundesirable outcomes(i.e.,diversemeans)
- Thestaffconsidersthisanappropriateareaforevaluatingdesign measuresotherthandiversitytoreducetheriskfromaDI&CCCF
- Thestaffsgoalistoapplyagradedapproachforthelevelofjustification neededfordesigntechniquesormeasuresotherthandiversity
- Diversemeanswillcontinuetobeacceptable 21
Benefits of Risk-Informed Approaches
- Riskinformedapproachescanprovideflexibilitytoaddress DI&CCCFs andareconsistentwiththePRAPolicyStatement
- RiskinformedapproachescanhavedifferentlevelsofPRAuse
- Riskinformedapproachescouldsupportagradedapproachfor addressingDI&CCCFsinhighsafetysignificantsystems
- PRAmodelscouldbeusedtosystematicallyassesstheneedtoreduce theriskintroducedbytheDI&Csystem
- Riskinformedapproachescanidentifyinitiatorsorscenarioswherelack ofDI&Cdiversitydoesnotcompromisesafety 22
Guiding Principles for Implementation
- Theexpandedpolicywillnotconflictwithexistingregulatory requirements
- Arulechangeorexemptionwillnotberequiredtoimplementit
- TheexpandedDI&CCCFpolicywillbeimplementedconsistentwiththe Commissions1995PRAPolicyStatement,SRMSECY980144,andthe currentagencyfocusonexpandingriskinformeddecisionmaking
- ImplementationoftheexpandedDI&CCCFpolicywillcontinueto providereasonableassurance ofadequateprotection ofpublic healthandsafety 23
Guiding Principles for Implementation (contd.)
- Theuseofriskinformedapproacheswillbeconsistentwithallfive principlesofriskinformeddecisionmaking,aslistedinRG1.174
- PRAsusedforriskinformedapproacheswillbetechnicallyacceptable (e.g.,meettheguidanceinRG1.200)andincludeaneffectivePRA configurationcontrolandfeedbackmechanism 24
Proposed Expanded Policy to Address DI&C CCFs 25 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 CCFs 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 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
- Theexpandedpolicywillencompassthecurrentpointsof SRMSECY93087(withclarifications)andexpandtheuseof riskinformedapproaches
- Anyuseofriskinformedapproacheswillbeexpectedtobeconsistent withtheSafetyGoalPolicyStatement,PRAPolicyStatement,andSRM SECY980144
- ThecurrentDI&CCCFpolicywillcontinuetoremainavalidoptionfor licenseesandapplicants 26
Status of Draft SECY Paper and Next Steps
- ThedraftSECYiscurrentlybeingdeveloped
- ApublicoutreachmeetingisplannedforJune2022
- ThestaffplanstosendtheSECYpapertotheCommissionin2022
- Uponapprovalofanexpandedpolicy,thestaffwillproceedtoupdate theimplementationguidanceinBTP719 27
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