ML11192A002
| ML11192A002 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 07/08/2011 |
| From: | Feintuch K Division of Operating Reactor Licensing |
| To: | Browning T Florida Power & Light Co |
| References | |
| Download: ML11192A002 (11) | |
Text
1 NRR-PMDAPEm Resource From:
Feintuch, Karl Sent:
Friday, July 08, 2011 2:46 PM To:
Browning, Tony Cc:
Harrison, Donnie; ONeal, Daniel; Howe, Andrew; Chawla, Mahesh
Subject:
FW: Additional RAI items for the DAEC TSTF-425 adoption amendment application Attachments:
ME5744 RAI resp (20Apr11), ML1111105070.pdf Repeat copy of this message is sent for the benefit of Ccd personnel.
From: Feintuch, Karl Sent: Friday, July 08, 2011 2:44 PM To: 'Browning, Tony'
Subject:
Additional RAI items for the DAEC TSTF-425 adoption amendment application
These items were sent to me by the APLA Branch Chief as a result of the July 7, 2011, call discussing the PRA Model status relative to ME5744, TSTF-425 adoption. The items are separately identified to facilitate any further specific discussion.
I am sending them as draft RAI items. For traceability, I linked them to the July 7, 2011, discussion (that is RAI 2011-07-07 prefix). If you have another more suitable identifier scheme, then just apply it and precede each answer with the associated item text.
Please confirm that your responses can be absorbed within the existing August 15, 2011, response schedule.
Karl Feintuch USNRC 301-415-3079
========= begin RAI 2011-07-07 items========
Please confirm, or clarify, the following summary of the July 7, 2011 conference call. Based on this conference call, the staff understands that:
- 1. The probabilistic risk assessment (PRA) model, Revision 6, proposed for the TSTF-425 application, is complete.
- 2. The status of the open gap items for Revision 6 is as provided in the supplemental information, dated April 20, 2011.
- 3. The focused peer review, noted in the supplemental information, utilized appropriate independent peer reviewers consistent with Regulatory Guide 1.200.
- 4. The focused peer review reviewed the 83 potential gap items from the 2007 full scope peer review, including the 30 provided in the February 23, 2011 submittal.
- 5. The focused peer review also reviewed new methods and PRA model changes associated with the upgrade to Revision 6.
- 6. This focused peer review identified 12 items, 5 of which have been incorporated into Revision 6, and 7 open items as provided in the supplemental information.
- 7. The 7 open gap items supersedes the 30 open gap items provided in TSTF-425 application submittal, dated February 23, 2011, for Revision 6.
2
- 8. The 12 items include gap items not previously identified in the February 23, 2011 submittal.
- 9. In addition to confirming, or clarifying this summary, please describe the 5 gap items noted in the supplemental information and, for each with its own unique identifier, how they were dispositioned via the Revision 6 PRA model.
Duane Arnolds RAI response of April 20, 2011 (ADAMS Accession No. ML111110507), attached for convenience, is also the basis of our current understanding.
======== end RAI 2011-07-07 items===
Hearing Identifier:
NRR_PMDA Email Number:
99 Mail Envelope Properties (Karl.Feintuch@nrc.gov20110708144600)
Subject:
FW: Additional RAI items for the DAEC TSTF-425 adoption amendment application Sent Date:
7/8/2011 2:46:21 PM Received Date:
7/8/2011 2:46:00 PM From:
Feintuch, Karl Created By:
Karl.Feintuch@nrc.gov Recipients:
"Harrison, Donnie" <Donnie.Harrison@nrc.gov>
Tracking Status: None "ONeal, Daniel" <Daniel.ONeal@nrc.gov>
Tracking Status: None "Howe, Andrew" <Andrew.Howe@nrc.gov>
Tracking Status: None "Chawla, Mahesh" <Mahesh.Chawla@nrc.gov>
Tracking Status: None "Browning, Tony" <Tony.Browning@fpl.com>
Tracking Status: None Post Office:
Files Size Date & Time MESSAGE 2786 7/8/2011 2:46:00 PM ME5744 RAI resp (20Apr11), ML1111105070.pdf 661615 Options Priority:
Standard Return Notification:
No Reply Requested:
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Normal Expiration Date:
Recipients Received:
Attachment to NG-11-0135 Page 1 of 6 Request for Clarifying Information - NextEra Energy Duane Arnold Probabilistic Risk Assessment Model for Use in Implementing TSTF-425, Rev.1 During a teleconference held on March 29, 2011 between the NRC Staff and NextEra Energy Duane Arnold personnel, the Staff requested that information contained in of the referenced application (Documentation of PRA Technical Adequacy) be clarified to assist the Staff in evaluating the Duane Arnold Energy Center (DAEC)
Probabilistic Risk Assessment (PRA) model. Specifically, the following information was requested:
- 1) The application states that Revision 6 of the DAEC PRA, currently under development, will be the model used to implement this Technical Specification (TS) change upon approval. When is it expected to be finalized and issued for use?
Response
As stated in the application, Revision 6 is intended to also support the conversion of the DAEC Fire Plan to the NFPA-805 standard. As the license amendment request for the Fire Plan conversion is currently scheduled for submission by June 29, 2011, Revision 6 of the DAEC PRA will be implemented no later than that date.
- 2) The application discusses the results of the Peer Review conducted on the DAEC PRA model, Revision 5C. That review resulted in the identification of 83 potential gaps to meeting Capability Category II in the Supporting Requirements of the ASME Standard. However, the Tables provided in Attachment 2 of the submittal only discuss 30 of those items. Please provide a discussion of the disposition of all 83 identified items and the expected status of any open items when Revision 6 of the model is issued.
Response
The intent of the Attachment 2 Tables was to discuss only those items that remained in an open status at the time of the application and to bin them into separate Tables by significance. Therefore, any item which had already been dispositioned and closed in the Revision 6 model was not reported in the Tables because they no longer represented gaps to Capability Category II. Because Peer Reviews often result in findings that may represent potential gaps in more than one Supporting Requirement in the ASME Standard, there was overlap between the line items found in the 3 Tables in the application which makes a simple tallying of them back to the original 83 items difficult.
Subsequent to the original application, NextEra Energy performed a follow-up Focused Peer Review to validate the closure of those previously identified 83 items from the 2007 Peer Review. In addition, that review utilized the current version of the ASME Standard (RA-Sb-2009).
Attachment to NG-11-0135 Page 2 of 6 The Focused Peer Review team found that NextEra Energy had appropriately incorporated most of the 83 previously identified items into Revision 6. However, not all of the closures were found to fully meet Capability Category II requirements, which resulted in new open items, in addition to those items that remained open at the time of the Focused Peer Review. The final result was a total of 12 items that were assessed as not meeting Capability Category II per the current ASME Standard. Of these 12 items, five will be addressed and incorporated into Revision 6 of the DAEC model upon issuance prior to June 29, 2011. The remaining seven items are judged to have either no, or only minor, impact on the models ability to support this application. The following Table describes those seven open items.
In order to not repeat the confusion created by binning them into gaps, findings, and suggestions, as was done in the original Attachment 2 Tables, we have simplified the presentation of the current open items on the pending Revision 6 of the DAEC PRA model into a single Table.
Attachment to NG-11-0135 Page 3 of 6 ASMECategoryIISRsNotMetinDAECModel,Rev.6
ASMESRs
CategoryIISRDetails
DescriptionofGAP
ImpactonQuantification
ImportancetoApplication
IEB301A
GROUPinitiatingeventsonlywhenthe
followingcanbeassured:
(a) eventscanbeconsideredsimilarin
termsofplantresponse,success
criteria,timing,andtheeffectonthe
operabilityandperformanceof
operatorsandrelevantmitigating
systems;or
(b) eventscanbesubsumedintoagroup
andboundedbytheworstcaseimpacts
withinthe"new"group.
AVOIDsubsumingeventsintoagroup
unless:
(i) theimpactsarecomparabletoorless
thanthoseoftheremainingeventsin
thatgroup,
AND
(ii) itisdemonstratedthatsuchgrouping
doesnotimpactsignificantaccident
sequences.
SeveralfindingsandsuggestionsunderHLRAandHLRBhavebeen
dispositioned/resolved,butthesubsuming(IEB3)andscreening
(IEC4(C6))ofinitiatingeventsdoesnotmeetthestandard.The
followingprovidesexamplesummarizes(IENotebook,including
AppendixH):
RBCCW(failsCRD,whichiscreditedforearlyinjection)is
subsumedbyTT,butRBCCWisnotfailedgivenTT.
GSW(failsRBCCW,CRD,Feedwater,etc.)issubsumedbyTC,but
thesesystemsarenotfailedgivenTC.
TheimpactsofReferenceandVariableLegBreaksarenot
adequatelydescribedandaresubsumedbyLossofFW.Most
likelywouldbeamanualshutdownwithcomplicationsversesa
LossofFW.Giventhatimmediateshutdownwouldoccurgivena
break,theseshouldbemodeled.Section2.4.8describedthelow
riskfromthese,butthisdoesnotmeetstandardforscreening.
1A1/1A2busfailuresandpartiallossoffeedwater(onepump)are
binnedtoTT,butthisimpactisnotmodeledgivenTT.
1A3/1A4busfailuresaresubsumedwithTT.Impactonlossof
chargers[TS3.8.4.]etc.andpossibilitythatfailureisaproblem
couldleadtoanimmediateshutdown.Notes11and12suggest
thatonlynormalpowersourceislost,butemergencypoweris
alsounavailableifbusfails.
RECOMMENDATION:FollowIEB3andC6withregardtosubsuming
andscreeningormoreimportantlymodeltheaboveinitiatingevents.
Modelingtheseadditionalinitiatorswill
betterdefinecertainaccidentsequences
andamoreaccuratelydetermine
associatedSSCimportance.
Overallcalculatedriskslightlyincrease;
significantlyforspecificfunctions
associatedwiththeinitiatingevent.Some
applicationsmayseeaslightdecreasein
riskmargin.
Althoughtheimportanceofaffected
componentsisnotfullyconsidered;
theirimpactcanbeaddressedfor
specific5bapplicationsusing
sensitivityanalysis,qualitative
analysis,boundinganalysisor
explicitmodelinginaccordancewith
theNEI0410guidance.
SYA501A
INCLUDEtheeffectsofbothnormaland
alternatesystemalignments,totheextent
neededforCDFandLERFdetermination.
TheSBOeventtreedoesnottakecreditforcontainmentventing
usinganalternatealignmentwhenthepneumaticsupplyislost.DAEC
procedureSAMP706providesdetaileddirectionforventingPCgiven
anunavailablepneumaticsupply.TheContainmentVentnotebook
doesnotcredit/discussthisprocedure.
RECOMMENDATION:Addcontainmentventingtotheeventtree
alongwithoperatoractionsandcomponentalignmentsneededto
ventcontainmentwithoutthepneumaticsupplysystem.
CreditingtheB5bprocedurethat
implementscontainmentventingwithouta
pneumaticsupplywillreduceoverall
calculatedrisk.Willhaveamoresignificant
impactonSBOsequences.
Willimproveresultsfor5b
applicationsespeciallythose
functionsassociatedwithSBO.
Withoutthischangethemodelis
conservative.
Attachment to NG-11-0135 Page 4 of 6 ASMECategoryIISRsNotMetinDAECModel,Rev.6
ASMESRs
CategoryIISRDetails
DescriptionofGAP
ImpactonQuantification
ImportancetoApplication
SYC201A
DOCUMENTthesystemfunctionsand
boundary,theassociatedsuccesscriteria,
themodeledcomponentsandfailure
modesincludinghumanactions,anda
descriptionofmodeleddependencies
includingsupportsystemandcommon
causefailures,includingtheinputs,
methods,andresults.
ThereisnoFireWaterSystem(AlternateInjection)notebookor
equivalentinformationinanothernotebook.Theoperatoractionto
alignfirewaterforinjectionismodeledbutthecomponentsare
basedontheargumentthattheprobabilityoftheactionsubsumes
thecomponentfailurerates.
RECOMMENDATION:Developnewsystemnotebookforuseoffire
waterasanalternateinjectionsource.
Documentingtheuseofthefirewater
systemasanalternateinjectionsourcewill
facilitateamorethoroughevaluationof
thisfunction.Creditingfirewaterinjection
(lateintheevent)willdecreaseoverallrisk,
especiallyforSBOsequences.
Willimproveresultsfor5b
applicationsespeciallythose
functionsassociatedwithSBO.
Withoutthischangethemodelis
conservative.
HRA101A
ForequipmentmodeledinthePRA,
IDENTIFY,throughareviewofprocedures
andpractices,thosetestandmaintenance
activitiesthatrequirerealignmentof
equipmentoutsideitsnormaloperational
orstandbystatus.
HRANotebook(AppendixJ,TableJ1)includesasystematicapproach
toidentifyingtestandmaintenanceactivitiesthroughasystemby
systemreviewofpotentialmisalignments.Thismeetsthehighlevel
requirementtouseasystematicapproachandisjudgedtobe
adequatebythePeerReviewteam.However,theSRwording
requiresareviewofproceduresandpracticeswhichwasnot
followed.Asaresult,thePRteammustassessthisSRasnotmet.
RECOMMENDATION:ReassessthisSRwhentheAddendumBofthe
PRAStandardisreleased.Thecurrentproposedrevisiondeletesthe
requirementforareviewofproceduresandpractices.
Noimpact.Asnotedbythereviewteama
systematicapproachwasusedtoidentify
potentiallysignificantmisalignments.
Basedonthisreview,onlytheprocedures
thatwereassociatedwiththesealignments
werereviewedfurther.DAECnotedthat
theydidreviewalltheproceduresbutdid
notdocumentthisreview.
ThedraftrevisionofaddendumBtoHRA1
thatiscurrentlyinreviewdeletesthe
requirementforareviewofprocedures
andpractices.
NoimpactsinceDAECstaffdid
reviewallprocedures;howeverthey
didnotdocumentthisreview.
HRA201A
IDENTIFY,throughareviewofprocedures
andpractices,thosecalibrationactivities
thatifperformedincorrectlycanhavean
adverseimpactontheautomaticinitiation
ofstandbysafetyequipment.
HRANotebook(AppendixJ,TableJ1)includesasystematicapproach
toidentifyingcalibrationactivitiesthroughasystembysystemreview
ofpotentialmiscalibrations.Thismeetsthehighlevelrequirementto
useasystematicapproachandisjudgedtobeadequatebythePeer
Reviewteam.However,theSRwordingrequiresthroughareviewof
proceduresandpracticeswhichwasnotfollowed.Asaresult,thePR
teammustassessthisSRasnotmet.
RECOMMENDATION:ReassessthisSRwhentheAddendumBofthe
PRAStandardisreleased.Thecurrentproposedrevisiondeletesthe
requirementforareviewofproceduresandpractices.
Noimpact.Asnotedbythereviewteama
systematicapproachwasusedtoidentify
potentiallysignificantmiscalibrations.
Basedonthisreview,onlytheprocedures
associatedwiththeseacionswerereviewed
further.DAECnotedthattheydidreview
alltheproceduresbutdidnotdocument
thisreview.
ThedraftrevisionofaddendumBtoHRA1
thatiscurrentlyinreviewdeletesthe
requirementforareviewofprocedures
andpractices.
NoimpactsinceDAECstaffdid
reviewallprocedures;howeverthey
didnotdocumentthisreview.
Attachment to NG-11-0135 Page 5 of 6 ASMECategoryIISRsNotMetinDAECModel,Rev.6
ASMESRs
CategoryIISRDetails
DescriptionofGAP
ImpactonQuantification
ImportancetoApplication
HRC101A
Foreachunscreenedactivity,DEFINEa
humanfailureevent(HFE)thatrepresents
theimpactofthehumanfailureatthe
appropriatelevel,i.e.,function,system,
train,orcomponentaffected.
AnumberofpreIEHFEsareidentifiedformodelinginthePRA.
GenerallytheseHFEsareatthetrainorsystemlevel,asappropriate.
However,asmallsetwereidentifiedatthesystemlevelwithout
relatedtrainlevelHFEs.ItispossiblethatthetrainlevelHFEmaybe
importanttosystemunavailability.Forexample,miscalibrationofDG
fueloilleveltransmittersisdoneatthesystemlevel,butnotatthe
trainlevel.Atthetrainlevel,theHFEwouldbe8e3,comparedwith
independentfailureoftheleveltransmitterof5e4.Inothercases,
theHFEisatthetrainlevel,butnocorrespondingsystemlevel
dependentHFEisincluded.Forexample,failuretorestoreRHRSW
postTMisdevelopedatthetrainlevel,butnocommonmisalignment
ofbothtrainsisconsidered.
RECOMMENDATION:Reviewthedifferencesbetweenthemodeling
ofsystemimpactvstrain.
Roughly10preinitiatorsareaffected.The
probabilityforthesepreinitiatorsislow.
Thereforeaddressingthisfindingis
expectedtohaveaminorimpactonoverall
risk.
Mayhaveaminorimpactonsome
5bapplications.
QUD5a01A
IDENTIFYsignificantcontributorstoCDF,
suchasinitiatingevents,accident
sequences,equipmentfailures,common
causefailures,andoperatorerrors[CatI].
INCLUDESSCsandoperatoractionsthat
contributetoinitiatingeventfrequencies
andeventmitigation[CatII].
RECOMMENDATION:Faulttreesarerequiredforsupportsystem
initiatingeventsinordertosatisfythisSR[CatII].
CategoryIwasmet.Addinginitiatingevent
faulttreeswillnotalteroverallresultsifthe
faulttreeresultsareinagreementwiththe
originalpointestimates.Howeverthere
willbeanincreaseinriskimportance
associatedwithoperatoractionsandSSCs
thatareincludedintheinitiatingevent
faulttrees.
Althoughtheimportanceofaffected
SSCsonaninitiatingeventmaynot
befullyconsidered;theirimpactcan
beaddressedforspecific5b
applicationsusingsensitivity
analysis,qualitativeanalysis,
boundinganalysisorexplicit
modelinginaccordancewiththeNEI
0410guidance.
Attachment to NG-11-0135 Page 6 of 6 These open items are contained in a controlled database that, by NextEra Energy procedure, must be reviewed prior to beginning any PRA application. Therefore, each open item will be reviewed as part of the Surveillance Test Interval change assessment.
If an open item has a potential impact on the results, then additional assessments (sensitivities) will be performed in accordance with the guidance contained in NEI 04-10.
In summary, with the exception of the seven items listed in the above Table, all previously identified items that represent gaps to Capability Category II will be fully incorporated into Revision 6 of the DAEC PRA model upon formal issuance.