august 14, 2014 company rc-14-0129 - nrc: home page · a scana company rc-14-0129 u.s. nuclear...

Thomas D. Gatlin

Vice President, Nuclear Operations

803.345.4342

August 14, 2014A SCANA COMPANY RC-14-0129

U.S. Nuclear Regulatory CommissionDocument Control DeskWashington, D.C. 20555-0001Attn: S. A. Williams

Dear Sir or Madam:

Subject: VIRGIL C. SUMMER NUCLEAR STATION (VCSNS) UNIT 1DOCKET NO. 50-395OPERATING LICENSE NO. NPF-12LICENSE AMENDMENT REQUEST-LAR-06-00055LICENSE AMENDMENT REQUEST TO ADOPT NFPA 805RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION

References:

1. Thomas D. Gatlin, SCE&G, Letter to NRC Document Control Desk, LicenseAmendment Request - LAR-06-00055, "License Amendment Request toAdopt NFPA 805 Response to Request for Additional Information" datedNovember 15, 2011 (RC-11-0149)

2. Shawn A. Williams, NRC, to Thomas D. Gatlin, SCE&G, "Virgil C. SummerNuclear Station Unit - 1 (VCSNS) - Request for Additional InformationRegarding License Amendment Request to Adopt National Fire ProtectionAssociation Standard 805 (TAC NO. ME7586)" dated July 11, 2014[ML14182A473]

South Carolina Electric & Gas Company (SCE&G), acting for itself and as agent forSouth Carolina Public Service Authority pursuant to 10 CFR 50.90, submitted LicenseAmendment Request (LAR) per Reference 1 and several responses to LAR Requestsfor Additional Information (RAI) to adopt NFPA 805. NRC review and audit of theserequests determined that additional information was required and a RAI was issuedper Reference 2. The Attachment of this letter contains SCE&G's response to theseRAIs. VCSNS spoke with Shawn Williams on August 7, 2014 and was granted anextension which sets August 14, 2014 as the new due date. SCE&G's response to RAI100 will be submitted by September 30, 2014.

Virgil C. Summer Station . Post Office Box 88. Jenkinsville, SC .29065 . F (803) 941-9776

Document Control DeskLAR-06-00055RC-14-0129 of 2

If you have any questions about this submittal, please contact Bruce L. Thompson at(803) 931-5042.

There are no commitments contained in this document.

I certify under penalty of perjury that the foregoing is correct and true.

Thomas D. Gatlin/Executed on

RLP/TDG/ts

Attachment:Probabilistic Risk Assessment (PRA) Request for Additional Information (RAI)Response

c: Without Attachments unless notedK. B. MarshS. A. ByrneJ. B. ArchieN. S. CarnsJ. H. HamiltonJ. W. WilliamsW. M. CherryV. M. McCree (w/Attachments)S. A. Williams (w/Attachments)NRC Resident InspectorS. E. JenkinsPaulette LedbetterK. M. SuttonNSRCRTS (CR-06-00055)File (813.20)PRSF (RC-14-0129) (w/Attachments)

Document Control DeskAttachmentLAR-06-00055RC-14-0129Page 1 of 25

VIRGIL C. SUMMER NUCLEAR STATION UNIT 1DOCKET NO. 50-395

OPERATING LICENSE NO. NPF-12ATTACHMENT

Probabilistic Risk Assessment (PRA) Request for Additional Information (RAI)Response


PRA RAI 64.01

In a letter dated October 10, 2012 (Agencywide Documents Access and ManagementSystem (ADAMS) Accession Number ML12297A218), the licensee responded to PRARAI 64 and provided the results of a sensitivity analysis from applying a variancemethod that incorporates component failure rate error factors in developing the meaninterfacing system loss of coolant accident (ISLOCA) frequency. The results showed anincrease by a factor of 3.7 in internal events core damage frequency (CDF) to 5.OE-05per year and an increase by a factor of 145 in internal events large early releasefrequency (LERF) to 3.7E-05 per year. The licensee stated that these increases aredominated by the variance in the rupture failure rate for motor-operated valves (MOVs).The NRC staff notes that while the ISLOCA frequency calculation method utilized in theinternal events probabilistic risk assessment (IEPRA) has no impact on the Fire PRA(FPRA), the large increase in CDF and LERF shown in this sensitivity analysis results inthe total CDF (including internal events, fire events, and seismic events) and LERFexceeding the Regulatory Guide (RG) 1.174, "An Approach for Using Probabilistic RiskAssessment in Risk-Informed Decisions on Plant-Specific Changes to the LicensingBasis," Revision 2, May 2011 (ADAMS Accession No. ML100910006) risk guidelines forRegion II so that only very small risk increases are allowed. Assess the relevance ofmore recent data on rupture failure rate of MOVs to the analysis, including updating thecontribution to total CDF and LERF from this issue. •

Alternately, additional analysis or modifications may be necessary to meet RG 1.174guidelines. Provide a discussion of the potential changes to the overall analysis,including any plant changes needed to meet RG 1.17 4 guidelines as developed inresponse to PRA RAI 98, as well as the updated risk measures, CDF and LERF.

SCE&G Response:

The question about variance in the ISLOCA frequency was originally raised in the peerreview of the VC Summer PRA in 2002 (F&O IE-06). The answer to this issue involveda spreadsheet using a factored approach that gave a mean value for ISLOCA frequencywith a large variance as described in the question above.

The ISLOCA model for VC Summer underwent an update after F&O IE-06 wasaddressed. This update changed the ISLOCA model from a single number calculatedoutside of the fault tree (effectively a module) to explicit modeling of ISLOCA failuremodes within the fault tree. These failure modes are represented by basic events withassigned error factors. The basic events are correlated by "type codes" for uncertaintystudies.


With the new model, it is possible to run a monte-carlo simulation on the ISLOCA cutsetfile that produces uncertainty bounds and gives a new mean value for the ISLOCAinitiating event frequency based on the uncertainty bounds. The result of this calculationis that the monte-carlo ISLOCA initiating event mean (5.59E-05/yr) is very close to thevalue calculated by the fault tree (5.56E-05/yr).

I1l 1j 1 EA l

F1Mwoo. 5.w0U-1 :4 nE055n 55E095%4 : 7,23E05,o.sdo l00

&E- 695E5 71-5 7959 5-5 65E-5 &E-5 9.5E-5 1104 15 E4

F.Q-.y / PI.Wbiky

* Impo.tarc, I,~-1f.54~CDF=1.l5%POF -5175.51 [rc ~ -- FIdsa5s~

The individual ISLOCA component failure uncertainties are correlated in the overalluncertainty analysis for CDF and LERF for the new model. The CDF and LERF resultsfor a monte-carlo analysis using 10,000 simulations are shown in the table below anddemonstrate compliance with RG 1.174 risk guidelines.

Mean 5% 95%CDF 4.15E-06 1.73E-06 8.66E-06LERF 1.09E-07 3.19E-08 2.66E-07


PRA RAI 66.03

In a letter dated May 2, 2014, (ADAMS Accession No. ML14125A274) the licenseeresponded to PRA RAI 66.02 and stated that "additional cable protectionmodifications were added to protect the CREP panels in CB04, CB06, CB15, andCB17" and "additional cable protection modifications were added to the latest firePRA model to protect several additional functions including prevention of spuriousESFAS, prevention of RWST draindown, isolation of spray suction, and EDGloading." It does not appear, however, that these modifications are included in theupdated LAR Attachment C provided in the letter dated February 25, 2014 (ADAMSAccession No. ML14063A455), nor are they described in the updated LARAttachment S, Table S-1, provided in the letter dated October 14, 2013 (ADAMSAccession No. ML13289A194). Identify which of the ECR modification(s) in LARAttachment S, Table S-1 includes these "additional cable protection modifications."In addition, describe all of the individual modifications included under this ECRmodification(s), and describe where each of these individual modifications isspecifically identified in the LAR to either make a VFDR (DROID) deterministicallycompliant or to only reduce risk.

SCE&G Response:

The "additional cable protection items" discussed in SCE&G's response to PRA RAI66.02 (RC-14-0067) did not result in new Engineering Change Request (ECR)modifications being added to LAR Attachment S, Table S-1. Instead, the scope of twoexisting ECR modifications have been modified as necessary to include these items.The two ECRs that contain the scope of these modifications are:

* ECR50810, NFPA 805 Hazard Protection" ECR50784, NFPA 805 Circuit/Tubing Protection

Additional information regarding the scope of each of these modifications is providedbelow including identification of why they were required, either for a DROID (VFDR), orfor risk reduction.

Additional Cable Protection Items discussed in PRA RAI 66.02 Response that areincluded in the scope of ECR50810:

The response to RAI 66.02 states that cable protection was applied to equipmentcontrols from the Control Room Evacuation Panel (CREP). This was to addresspotential loss of CREP controls for fires in CB04, CB06, CB15, and CB17. The CREPpanel protection cables are in the FRANx database and documented in the


Quantification notebook in the table "FireImpact Data - Mods". The scope of thismodification has been added to ECR50810.

It should be noted that although circuits associated with this modification are describedas being "protected" in the PRA RAI 66.02 response, this is only FPRA modelingterminology. ECR50810 will independently power the EFW isolation valves (IFV-3531,3541, 3551, 3536, 3546 and 3556) from their respective CREP panels (XPN-7006A/B)and isolate power from the Control Room. This is to ensure Emergency Feedwatercontrol from the CREP panels is available. The goal is preservation of equipmentfunction from the CREP. The function of the circuits listed in Table 1 will be protected,not the cables themselves.

This modification was identified to reduce risk in the FPRA. ECR50810 is in the designphase and is scheduled to be completed by the end of 2015.

Table 1 - FPRA RAI 66.03 Response

Fire Area DROID ID Cable PlantECR

CB04, CB06, CB15 N/A (Risk Reduction) EFW 21B 50810CB04, CR06, CB15 N/A (Risk Reduction) EF W 22B 50810CB15 N/A (Risk Reduction) EF W 23B 50810CB15 N/A (Risk Reduction) EF W 24B 50810CB04, CB06, CB15 N/A (Risk Reduction) EFW 56B 50810CB04, CB06, CB15 N/A (Risk Reduction) EFW 57B 50810CB04, CB06, CB15 N/A (Risk Reduction) EFW 61A 50810CB04, CB06, CB15 N/A (Risk Reduction) EFW 62A 50810CB15 N/A (Risk Reduction) EFW 63A 50810CB15 N/A (Risk Reduction) EFW 64A 50810CB04, CB06, CB15 N/A (Risk Reduction) EFW 86A 50810CB15 N/A (Risk Reduction) EFW 89A 50810CB15 N/A (Risk Reduction) EFW 91B 50810CB15 N/A (Risk Reduction) EFW 92B 50810CB15 N/A (Risk Reduction) EFW 93B 50810CB04, CB06, CB15 N/A (Risk Reduction) EFW 94B 50810CB04, CR06, CB15 N/A (Risk Reduction) EFW 95B 50810CB04, CR06, CB15 N/A (Risk Reduction) EFW 97B 50810CB04, CB06, CB15 N/A (Risk Reduction) EFW 98B 50810CB15 N/A (Risk Reduction) EF W 103B 50810CB15 N/A (Risk Reduction) EF W 104B 50810



CB15 N/A (Risk Reduction) EF W 109B 50810CB04, CB06, CB15 N/A (Risk Reduction) EFW 110B 50810CB15 N/A (Risk Reduction) EF W 111A 50810CB15 N/A (Risk Reduction) EF W 112A 50810CB1 5 N/A (Risk Reduction) EF W 113A 50810CB04, CB06, CB15 N/A (Risk Reduction) EF W 114A 50810CB15 N/A (Risk Reduction) EF W 115A 50810CB04, CB06, CB15 N/A (Risk Reduction) EF W 116A 50810CB15 N/A (Risk Reduction) EF W 117B 50810CB15 N/A (Risk Reduction) EF W 122A 50810CB15 N/A (Risk Reduction) EF W 123A 50810CB04, CB06, CB15 N/A (Risk Reduction) EF W 128A 50810CB15 N/A (Risk Reduction) EF W 133B 50810CB15, CB17.01 N/A (Risk Reduction) EF W7003A 50810CR15, CB17.01 N/A (Risk Reduction) EF W7005A 50810CB15, CB17.01 N/A (Risk Reduction) EF W7012A 50810CB15, CB17.01 N/A (Risk Reduction) EF W7014A 50810CB15, CR17.01 N/A (Risk Reduction) EF W7017A 50810CB15, CB17.01 N/A (Risk Reduction) EF W7018A 50810CR15, CB17.01 N/A (Risk Reduction) EF W7019A 50810CB15, CB17.01 N/A (Risk Reduction) EF W7020A 50810CR15, CB17.01 N/A (Risk Reduction) EF W7021A 50810CB15, CB17.01 N/A (Risk Reduction) EF W7022A 50810CB15, CR17.01 N/A (Risk Reduction) EF W7023A 50810CB15, CB17.01 N/A (Risk Reduction) EF W7024B 50810CR15, CB17.01 N/A (Risk Reduction) EF W7025B 50810CR15, CB17.01 N/A (Risk Reduction) EF W7026B 50810CB15, CB17.01 N/A (Risk Reduction) EF W7027B 50810CR15, CB17.01 N/A (Risk Reduction) EF W7028B 50810CR15, CB17.01 N/A (Risk Reduction) EF W7029B 50810CB15, CR17.01 N/A (Risk Reduction) EF W7030B 50810CB15, CB17.01 N/A (Risk Reduction) EF W7031B 50810CR15, CB17.01 N/A (Risk Reduction) EF W7032B 50810CR15, CB17.01 N/A (Risk Reduction) EF W7034B 50810CB15, CB17.01 N/A (Risk Reduction) EF W7035B 50810CB15, CB17.01 N/A (Risk Reduction) EF W7036B 50810CB15, CR17.01 N/A (Risk Reduction) EF W7037B 50810



CB15, CB17.01 N/A (Risk Reduction) EF W7039B 50810CB15, CB17.01 N/A (Risk Reduction) EF W7041B 50810CB15, CB17.01 N/A (Risk Reduction) EF W7042B 50810CB15, CB17.01 N/A (Risk Reduction) EF W7043B 50810CB15, CB17.01 N/A (Risk Reduction) EF W7044B 50810CB15, CB17.01 N/A (Risk Reduction) EF W7045B 50810CB15, CB17.01 N/A (Risk Reduction) EF W7046B 50810CB15, CB17.01 N/A (Risk Reduction) EF W7047B 50810CB15, CB17.01 N/A (Risk Reduction) MC E7004A 50810CB15, CB17.01 N/A (Risk Reduction) MS W7019A 50810CB04, CB06 N/A (Risk Reduction) SG J 31A 50810CB04, CB06 N/A (Risk Reduction) SG J 32B 50810

Additional Cable Protection Items discussed inare included in the scope of ECR50784:

FPRA RAI 66.02 Response that

SCE&G's PRA RAI 66.02 response discussed cable protection of additional items topreserve several nuclear safety functions. It should be noted that although these itemswere described as "additional cable protection items," some of them were only newlycredited in the FPRA, and have been included in the scope of ECR50784 to support theNuclear Safety Capability Assessment (NSCA) since the original LAR submittal. Table2 includes the requested details for these modifications. ECR50784 is in theimplementation phase and all work is scheduled to be completed by the end of 2015.


Fire Area DROID ID Cable Notes Plant ECRABO1.04 DROID-ABO1.01, CS C 82B 50784

02, 03, 04, 06, 09-10

AB01.06 DROID-ABO1.01, CS C 72B 5078402, 03, 04, 06, 09-10

ABO1.09 DROID-ABO1.01, CS C 82B 5078402, 03, 04, 06, 09-10

CB02 DROID-CB02-10 ED E 34B Protection of ED E 34B 50784preserves desiredfunction. EM C 287B doesnot need protection as


Fire Area DROID ID Cable Notes Plant ECRidentified in the RAI 66.02response.

CB05 DROID-CB05-04 ED E 23A Protection of ED E 23A 50784ED E 24A and ED E 24A preserves

the desired equipmentfunction. EM C 281A andEM C 282A do not needprotection as identified inthe RAI 66.02 response

1B25.04 DROID-1B25.04-08 SI C 212B 50784SP C 92B

1B25.04 DROID-1B25.04-04 CS C 302B 50784CS C 305B

1B25.04 DROID-IB25.04-10 CS C 72B 50784

IB25.06.02 DROID-1B25.06, ES M 73X 5078407-09

IB25.06.02 DROID-1B25.06, ES M 63X 5078407-10

1B25.06.02 N/A (For Risk RC M 15X 50784Reduction) RC M 25X

RC M 35X

Full scope of ECR50784

ECR50784 consists of circuit protection modifications including replacement of cablewith fire rated cable, and installation of fire wrap. To address the request for allmodifications included in ECR50784, Table 3 contains the remaining circuit protectionmodifications that were not identified in Table 2. The scope of ECR50784 agrees withthe B-3 Table submitted under RC-14-0027 except for DROID-1B25.04.02. It wasdetermined during ECR50784 implementation that circuit protection is not requiredbecause redundant indication is available.



Fire Area DROID ID Cable Plant ECRABO1.10 DROID-AB.10, 13,14,15,16,17-05 RC E 5XB 50784ABO1.08.02 DROID-ABO1.08-03 CS C 103A 50784

MSUI101D 50784ABO1.10 DROID-ABO1.10, 13, 14,15,16,17-01 S U 3D

SI U 3D

ABO1.18.01 DROID-ABO1.18, 19-03 SI U 3D 50784CB01.01 DROID-CB01-01 NI A 198D 50784

C301.01 DROID-CBOI-18 CS C 52B 50784CS C 62B

CB01.01 DROID-CB01-32 SG D 14B 50784

CB02 DROID-CB02-07 CS C 52B 50784CS C 62B

CB02 DROID-CB02-42 EF U 55A 50784

CS C 42B 50784CB12 DROID-CB12-19 CS C 52B

CS C 62B

CB20 DROID-CB20-04 CS C 42B 50784EF U 4A 50784

1B25.01.03 DROID-IB25.01.03, .04, .05-01 EF U 5AEF U 55A

MS W251A 507841B25.01.03 DROID-IB25.01.03, .04, .05-02 MSW251A

MS W 256A

1B25.06.02 DROID-IB25.06, 07-05 VL C 12C 50784ABO1.21.02 N/A (Risk Reduction Only) CS W 304XD 50784CB10 N/A (Risk Reduction Only) ES M 94X 50784CB15 N/A (Risk Reduction Only) ES E 108X 50784

Full scope of ECR50810

The purpose of plant modification ECR50810 is to provide plant enhancements andaddress items identified during the NFPA 805 transition process. In addition to theCREP panel protection, the current scope includes replacing sections of existingsprinkler systems, installation of additional portable fire extinguishers, raising PostIndicator Valves, installation of lock boxes and storage boxes, anchoring flammableliquid storage cabinets and modifications to address LERs 2011-001, 2011-002 and2013-005.


PRA RAI 68.01

In a letter dated April 1, 2013 (ADAMS Accession Number ML13092A333), the licenseeresponded to PRA RAI 68 and explained that for grouped transient zones, (defined aszones in which all the fixed and transient ignition sources are failed completely at timezero), 120 new scenarios were identified for which walk downs showed that cable traysextend across transient zone boundaries. The NRC staff noted that these newscenarios do not appear to have been specifically included in the FPRAmodel, however, the results of an evaluation showed the scenarios increase the fireCDF by 1.4E-06 per year. While not significant to transition, the NRC staff notes thatthe self-approval acceptance guidelines are much smaller than the transitionacceptance guidelines and therefore addition of these 120 new scenarios could affectpost-transition plant change evaluations. Discuss how these scenarios will be includedin post-transition plant change evaluations if they are not specifically modeled in theFPRA.

SCE&G Response:

The list of grouped transient zones (i.e., those transient zones where targets are failedwith no credit for severity factors or nonsuppression probabilities), with potential forpropagation to adjacent transient zones that are not included in the Fire PRA, wasrevised in order to reduce the total CDF and is provided below in Table 1. The last rowof Table 1 shows that the total CDF increase for all the scenarios has been reduced to3.47E-08 (from the 1.4E-06 reported in the earlier RAI response). The value of3.47E-08 is low and does not affect the post-transition plant change evaluations. TheCDF reduction is primarily achieved by: 1) crediting automatic sprinklers in selectedscenarios, 2) crediting the hot gas layer scenario in TB02, and 3) performing detailedanalysis by crediting severity factors and non suppression probabilities in selectedscenarios (i.e., ungrouping the scenarios).

Technical details of the changes included in Table 1 intended to reduce total CDF areas follows:

1. Automatic sprinklers in TB01.02 are credited in scenarios TBO1.02-T2-TO-TBO1.02-T1 and TBO1.02-T9-TO-TBO1.02-T7. It should be noted that thesprinkler systems credited in these scenarios were already part of the NFPA 805fire protection required systems.


2. A hot gas layer scenario for TB02 is included in the Fire PRA; therefore, thefollowing scenarios are no longer listed in Table 1.

TB02-T1-TO-TB02-T2

TB02-T1-TO-TB02-T3

TB02-T2-TO-TB02-T1

TB02-T2-TO-TB02-T3

TB02-T3-TO-TB02-T1

TB02-T3-TO-TB02-T2

Since the hot gas layer scenario which fails all targets in the fire zone, fails thetargets at times shorter than propagation to adjacent transient zones within theFire Zone, the inclusion of the scenarios is not warranted.

3. Twenty-two new ungrouped scenarios (i.e., scenarios that are now receivingcredit for severity factors and non-suppression probabilities) in transient zoneTB01.01-T2 are added to the Fire Modeling Database; and therefore scenariosTB01.01-T2-TO-TB01.01-Ti and TBO1.01-T2-TO-TBO1.01-T10 are no longerlisted in Table 1. To make this change in the Fire Modeling Database, transientzone TBO1.01-T2 was changed to an "ungrouped" transient zone.

The additional scenarios from TBO1.01-T2 that will now be included in the quantificationof the Fire PRA are listed in Table 2.


Table 1: CDF for Grouped Transient Zones with Potential for Propagation to Adjacent Transient Zones (ReplacesTable 3 in PRA RAI 68 response, April 1, 2013, ADAMS Accession Number ML13092A333)

Base Case

PNS, CDF noExposing Automatic PNS, Manual CCDP no CCDP with propagation

Scenario ID IGF Suppression Suppression propagation propagation Total CDF considered

ABO1.04-T1-TO-ABO1.04-T2 2.12E-05 N/A 0.001 2.02E-08 1.28E-03 2.76E-11 4.28E-13


ABO1.04-T2-TO-ABO1.04-T7 1.90E-04 N/A 0.001 1.28E-03 1.28E-03 Note 1 Note 1

ABO1.04-T2-TO-ABO1.04-T8 1.90E-04 N/A 0.001 1.28E-03 1.28E-03 Note 1 Note 1

ABO1.04-T7-TO-ABO1.04-T2 5.21 E-05 N/A 0.001 2.02E-08 1.28E-03 6.77E-1 1 1.05E-12

ABO1.04-T7-TO-ABO1.04-T9 5.21 E-05 N/A 0.001 2.02E-08 2.21 E-05 Note 1 Note 1

AB01.04-T8-TO-AB01.04-T2 2.45E-04 N/A 0.001 7.64E-05 1.28E-03 1.90E-08 1.87E-08

ABO1.04-T9-TO-ABO1.04-T7 1.14E-04 N/A 1 2.21E-05 2.21E-05 2.52E-09 2.52E-09

ABO1.08.02-Ti -TO-ABO1.08.02-T2 6.61 E-06 N/A 0.001 2.95E-07 1.28E-03 1.04E-1 1 1.95E-12

ABO1.08.02-T2-TO-ABO1.08.02-T1 1.11E-05 N/A 0.001 1.28E-03 1.28E-03 1.42E-08 1.42E-08

ABO1.08.02-T3-TO-ABO1.08.02-T4 8.69E-06 N/A 0.001 1.28E-03 1.28E-03 1.11 E-08 1.11E-08


ABO1.08.02-T4-TO-ABO1.08.02-T5 1.20E-05 N/A 1 1.28E-03 1.28E-03 Note 1 Note 1

ABO1.08.02-T5-TO-ABO1.08.02-T4 1.02E-05 N/A 0.001 5.46E-07 1.28E-03 1.86E-1 1 5.57E-12



AB01.10-T13-TO-ABO1.10-T14 3.24E-04 N/A 1 2.72E-06 2.72E-06 8.81E-10 8.81E-10

ABO1 .10-T14-TO-AB101.10-T1 3 4.12E-04 N/A 1 2.72E-06 2.72E-06 1.12E-09 1.1 2E-09

ABO1.10-T14-TO-AB01.10-T15 4.12E-04 N/A 1 NA NA Note 2 NA

ABO1.10-T15-TO-AB01.10-T14 6.69E-05 N/A 1 NA NA Note 2 NA

AB01.18.01-T3-TO-ABO1.18.01-T4 1.04E-04 N/A 1 NA NA Note 2 NA

AB01.18.01-T4-TO-ABO1.18.01-T3 1.32E-04 N/A 1 NA NA Note 2 NA

ABO1.18.01-T4-TO-ABO1.18.01-T5 1.32E-04 N/A 1 NA NA Note 2 NA


Base Case

PNS, CDF noExposing Automatic PNS, Manual CCDP no CCDP with propagation

Scenario ID IGF Suppression Suppression propagation propagation Total CDF considered

ABO1.18.01-T5-TO-ABO1.18.01-T4 1.87E-05 N/A 1 NA NA Note 2 NA

ABO1.18.02-Ti0-TO-ABOl .18.02-T9 1.45E-05 N/A 1 4.12E-07 4.12E-07 5.97E-12 5.97E-12

ABO1.18.02-Ti 1-TO-ABO1.1 8.02-T3 5.78E-05 N/A 0.006 1.78E-05 5.03E-05 1.04E-09 1.03E-09

ABO1.18.02-T1i-TO-ABO1,18.02-T5 5.78E-05 N/A 1 1.78E-05 5.03E-05 Note 1 Note 1

ABO1.18.02-T3-TO-ABO1.18.02-Tll 1.85E-04 N/A 0.001 3.05E-07 5.03E-05 6.57E-1 1 5.64E-1 1


AB01.1 8.02-T5-TO-ABO1 .18.02-T1 1 2.32E-04 N/A 0.001 2.09E-08 5.03E-05 1.65E-1 1 4.85E-12

ABO1.I8.02-T5-TO-ABOI.18.02-T4 2.32E-04 N/A 1 2.09E-08 1.50E-06 Note 1 Note 1


ABO1.18.02-T7-TO-ABO1.18.02-T5 1.12E-05 N/A 1 2.02E-08 8.67E-07 9.71E-12 2.26E-13

ABO1.18.02-T8-TO-ABOI.18.02-T9 1.73E-05 N/A I 2.02E-08 2.02E-08 3.49E-13 3.49E-13

ABO1.1 8.02-T9-TO-ABO1 .18.02-T1 0 1.29E-05 N/A 1 2.02E-08 4.12E-07 5.31E-12 2.61E-13


ABO1.21.01-Ti-TO-ABO1.21.01-T2 1.76E-04 N/A 1 1.62E-04 1.05E-05 1.85E-09 2.85E-08

ABO1.21.01-T2-TO-ABO1.21.01-T1 1.25E-04 N/A 1 1.05E-05 1.05E-05 1.31 E-09 1.31 E-09

ABO1.21.02-Ti 1-TO-ABO1.21.02-T12 6.37E-04 N/A 0.001 4.14E-07 2.26E-04 4.07E-10 2.64E-10



ABO1.21.02-T13-TO-ABO1.21.02-T5 6.98E-05 N/A 1 2.90E-05 2.90E-05 2.02E-09 2.02E-09


ABO1.21.02-T7-TO-ABO1.21.02-T5 6.13E-05 N/A 0.001 4.14E-07 2.90E-05 2.71 E-1 1 2.54E-1 1

ABO1.29-Ti-TO-ABO1.29-T2 6.08E-04 N/A 1 NA NA Note 2 NA

ABO1.29-T2-TO-ABO1.29-Ti 9.01E-04 N/A 1 NA NA Note 2 NA

ABO1.29-T2-TO-ABO1.29-T3 9.01E-04 N/A 1 NA NA Note 2 NA



Base CasePNS, CDF no

Exposing Automatic PNS, Manual CCDP no CCDP with propagationScenario ID IGF Suppression Suppression propagation propagation Total CDF considered



CB02-T2-TO-CB02-T1 1.53E-05 N/A 1 NA NA Note 2 NA

CB04-T3-TO-CB04-T12 1.87E-05 N/A 0.001 1.65E-03 2.56E-03 Note 1 Note I

CB04-T3-TO-CB04-T13 1.87E-05 N/A 0.001 1.65E-03 1.37E-01 3.34E-08 3.09E-08

CB04-T5-TO-CB04-T6 1.51 E-05 N/A 0.001 6.77E-04 6.45E-04 1.02E-08 1.02E-08

CB04-T6-TO-CB04-T5 1.59E-05 N/A 0.001 6.95E-04 6.45E-04 1.1OE-08 1.11E-08


CB04-T9-TO-CB04-T1O 3.92E-06 N/A 1 NA NA Note 2 NA







IB20-T10-TO-IB20-T11 4.01E-04 N/A 0.001 7.11E-06 7.11E-06 2.85E-09 2.85E-09

IB20-T1O-TO-IB20-T9 4.01E-04 N/A 1 7.11E-06 7.11E-06 Note 1 Note 1

IB20-T11-TO-IB20-T1O 4.OOE-04 N/A 0.001 7.11E-06 7.11E-06 2.84E-09 2.84E-09

IB20-T1-TO-IB20-T8 7.50E-04 N/A 0.479 1.96E-05 9.87E-05 4.31 E-08 1.47E-08



IB20-T3-TO-IB20-T4 5.34E-04 N/A 1 1.96E-05 1.96E-05 Note 1 Note 1

IB20-T4-TO-IB20-T3 1.17E-04 N/A 1 1.96E-05 1.96E-05 Note 1 Note 1

IB20-T4-TO-IB20-T5 1.17E-04 N/A I 1.96E-05 1.96E-05 Note 1 Note 1





IB20-T4-TO-IB20-T9 1.1 7E-04 N/A 1 1.96E-05 7.11 E-06 Note I Note 1



IB20-T8-TO-IB20-T4 2.62E-04 N/A 0.479 9.87E-05 9.87E-05 Note 1 Note 1

1B20-T8-TO-1B20-T9 2.62E-04 N/A 0.479 9.87E-05 9.87E-05 Note 1 Note 1

IB20-T9-TO-IB20-T10 4.OOE-04 N/A 1 7.11E-06 7.11E-06 Note 1 Note 1

IB20-T9-TO-IB20-T4 4.OOE-04 N/A 1 7.11E-06 7.11E-06 Note 1 Note 1

IB20-T9-TO-IB20-T8 4.OOE-04 N/A 0.001 7.11E-06 9.87E-05 2.88E-09 2.84E-09

1B21.01-T2-TO- 1B21.01-T7 9.04E-06 N/A 1 2.74E-06 2.74E-06 2.48E-11 2.48E-11

IB21.01-T3-TO-IB21.01 -T7 6.02E-06 N/A 1 2.74E-06 2.74E-06 1.65E-11 1.65E-11

IB21.01 -T5-TO-IB21.01-T6 1.03E-04 N/A 0.479 2.85E-05 2.85E-05 2.94E-09 2.94E-09

1B21.01-T6-TO-IB21.01-T1 2.78E-06 N/A 1 2.85E-05 4.97E-05 1.38E-10 7.92E-11

1B21.01-T6-TO-IB21.01-T5 2.78E-06 N/A 1 2.85E-05 2.85E-05 Note 1 Note 1

IB21.01-T7-TO-IB21.01-T2 1.26E-05 N/A 1 2.74E-06 2.74E-06 3.45E-11 3.45E-11

IB21.01-T7-TO-IB21.01-T3 1.26E-05 N/A 1 2.74E-06 2.74E-06 Note 1 Note 1

I B25.01.03-Ti-TO-IB25.01.03-T2 1 .1 9E-05 N/A 0.001 4.83E-06 5.94E-04 6.45E-1 1 5.75E-1 1

IB25.01.03-T2-TO-IB25.01.03-Ti 9.87E-05 N/A 0.006 5.94E-04 5.94E-04 5.86E-08 5.86E-08

IB25.01.03-T2-TO-IB25.01.03-T4 9.87E-05 N/A 1 5.94E-04 5.94E-04 Note 1 Note 1

IB25.01.03-T4-TO-IB25.01.03-T2 5.67E-06 N/A 0.006 2.44E-08 5.94E-04 2.03E-1 1 1.38E-13

IB25.01.03-T4-TO-IB25.01.03-T6 5.67E-06 N/A 1 2.44E-08 2.55E-05 Note 1 Note 1

IB25.01.05-T3-TO-IB25.01.05-T5 1.07E-05 N/A 1 3.15E-07 3.15E-07 3.37E-12 3.37E-12

IB25.01.05-T5-TO-IB25.01.05-T3 1.29E-05 N/A 1 3.15E-07 3.15E-07 4.06E-12 4.06E-12

TBO1.01-T1O-TO-TBO1.01-T12 1.05E-03 N/A 1 2.02E-08 2.02E-08 Note 1 Note 1

TBO1.01-T1O-TO-TBO1.01-T13 1.05E-03 N/A 1 2.02E-08 2.02E-08 Note 1 Note 1

TBO1.01-T1O-TO-TBO1.01-T2 1.05E-03 N/A 0.187 2.02E-08 1.11E-05 2.20E-09 2.12E-11




TB01.01-Ti1-TO-TB01.01-T13 4.01E-04 N/A 1 2.02E-08 2.02E-08 8.10E-12 8.10E-12

TB01.01-T12-TO-TB01.01-T10 1.14E-03 N/A 1 2.02E-08 2.02E-08 2.30E-11 2.30E-11

TB01.01-T13-TO-TBO1.01-T10 7.99E-04 N/A 1 2.02E-08 2.02E-08 1.61E-11 1.61 E-11

TB01.01-T13-TO-TB01.01-T11 7.99E-04 N/A 1 2.02E-08 2.02E-08 Note 1 Note 1

T[301.01 -T14-TO-TBO1.01 -T9 1.07E-03 N/A 0.187 1.11 E-05 1.11 E-05 1.19E-08 1 .19E-08

T[301.01 -T9-TO-TB01.01-T1 4 2.94E-04 N/A 0.187 1.11 E-05 1.11 E-05 3.26E-09 3.26E-09

TB01.02-T10-TO-T801.02-T11 6.28E-04 N/A 1 2.02E-08 2.02E-08 Note 1 Note 1

TI01.02-T10-TO-TB01.02-T9 6.28E-04 N/A 0.187 2.02E-08 1.11E-05 1.31 E-09 1.27E-11

TBi01.02-Ti 1-TO-TBO1.02-Ti 0 6.38E-03 N/A 1 2.02E-08 2.02E-08 1.29E-10 1.29E-10

TI301.02-T11-TO-TBO1.02-T12 6.38E-03 N/A 1 2.02E-08 2.02E-08 Note 1 Note 1

TB01.02-T12-TO-TBO1.02-T11 5.76E-04 N/A 1 2.02E-08 2.02E-08 1.16E-11 1.16E-11

TB01.02-T2-TO-TBI01.02-T1 5.59E-04 0.02 0.187 1.17E-04 6.41 E-03 1.45E-08 1.31 E-09

TB01.02-T9-TO-TB01.02-T10 3.56E-04 N/A 1 1.11E-05 1.11E-05 Note 1 Note 1TI301.02-T9-TO-TB01.02-T7 3.56E-04 0.02 0.187 1.11E-05 6.41E-03 8.60E-09 7.90E-11

SUM 6.45E-07 6.10E-07

Total CDF Increase Due to Propagation Across Transient Zone Boundaries 3.47E-08

I

Notel: I hi1s scenario nas a LDUI-' that IS equal to or less man anomner scenario involving me same exposing transientzone. In order to apportion the ignition frequency correctly, only one combination per exposing transient zone isincluded in the calculation.

Note 2: One or both of the CCDP values is less than 2E-08, and therefore not a significant risk contributor.


Table 2: Additional Scenarios Added to the Fire PRA Model for UngroupedTransient Zone TB101.01 -T2

EquipmentEquipment Type

Fire Zone Equipment ID Equipment Description Type Description ScenarioTBO1.01 DPN1X DC DISTRIBUTION PANEL 1X EC Electrical 2

cabinetsTBO1.01 DPN2X DC POWER PANEL EC Electrical 2

cabinetsTBO1.01 H2-TBO1.01-12-03 H2 piping in the building H2 Misc. Hydrogen 2

FiresTBO1.01 TBO1.01-T2 Transient fire # 2 postulated at floor TRTB Transients 2

level.TBO1.01 TBO1.01-T2 Transient fire # 2 postulated at floor TRWTB Trans. fires - 2

level. welding/cuttingTBO1.01 XPNO100 IAM MOUNTING PANEL FOR IB EC Electrical 2

PRE-ACTION SYS cabinetsTBO1.01 XPN5142 LOC CONTR STAT FOR EC Electrical 2

XPP0042A cabinetsTBO1.01 XPP0042A CONDENSATE PUMP A PMP Pumps 2

TB01.01 XPP0042A CONDENSATE PUMP A ZOl Fire with 100% 2of Oil

TBO1.01 XPP0042A CONDENSATE PUMP A Z02 Fire with 10% of 2Oil

TBO1.01 XPP0042B CONDENSATE PUMP B PMP Pumps 2

TBO1.01 XPP0042B CONDENSATE PUMP B ZOl Fire with 100% 2of Oil

TB01.01 XPP0042B CONDENSATE PUMP B Z02 Fire with 10% of 2Oil

TBO1.01 XPP0042C CONDENSATE PUMP C PMP Pumps 2

TB01.01 XPP0042C CONDENSATE PUMP C ZOl Fire with 100% 2of Oil

TB01.01 XPP0042C CONDENSATE PUMP C Z02 Fire with 10% of 2Oil

TBO1.01 XPP0075A EXHAUST HOOD SPRAY PUMP A PMP Pumps 2

TB01.01 XPP0075A EXHAUST HOOD SPRAY PUMP A ZO1 Fire with 100% 2of Oil

TB01.01 XPP0075A EXHAUST HOOD SPRAY PUMP A Z02 Fire with 10% of 2Oil

TBO1.01 XPP0075B EXHAUST HOOD SPRAY PUMP B PMP Pumps 2

TBO1.01 XPP0075B EXHAUST HOOD SPRAY PUMP B ZO1 Fire with 100% 2of Oil

TB01.01 XPP0075B EXHAUST HOOD SPRAY PUMP B Z02 Fire with 10% of 2Oil


PRA RAI 85.02

In a letter dated November 26, 2013 (ADAMS Accession No. ML13333A280), thelicensee responded to PRA RAI 85.01 and stated that the FPRA is currently beingupdated based on changes due to RAI responses and that the model has beenconverted to use the most recent version of the FRANX software that will allowuncertainties for CDF and LERF to be provided. Furthermore, in a letter dated May 2,2014, (ADAMS Accession No. ML14125A274) the licensee responded to PRA RAI 98and stated that the updated uncertainty analysis utilizing this capability supports theconclusion that the estimated CDF and LERF are not significantly affected by state-of-knowledge correlations (SOKC). Clarify if delta (A) CDF and ALERF are significantlyaffected by SOKC (i.e., RG 1.174 risk guidelines are exceeded). If significantly affected,discuss the results and any changes made to the PRA model to meet the RG 1.174 riskguidelines.

SCE&G Response:

VCS confirmed in a letter dated May 2, 2014 in response to PRA RAI 98 that theupdated model and associated uncertainty analysis supports the conclusion that theestimated CDF and LERF are not significantly affected by state-of-knowledgecorrelations (SOKC).

This conclusion is also true for the ACDF and ALERF calculations. The ACDF andALERF calculations are not significantly affected by SOKC (i.e., RG 1.174 riskguidelines are not exceeded). Uncertainty calculations were completed for the meansof both the variant and compliant plant CDF and LERF. The delta risk was thencalculated using the means and the resulting delta risks were still within RG 1.174 riskguidelines. The results of the overall ACDF and ALERF uncertainty calculations areshown below.

CDF and LERF, Monte Carlo 5000 Simulations

CDF 5% 95% LERF 5% 95%(/reactor-yr) (/reactor-yr)

Variant 5.4E-05 2.90E-05 9.20E-05 2.5E-07 5.5E-08 6.7E-07

Compliant 4.7E-05 2.48E-05 8.33E-05 1.7E-07 5.OE-08 6.4E-07

Delta 6.4E-06 1.7E-08


PRA RAI 97.01

In a letter dated January 9, 2014 (ADAMS Accession No. ML14013A074), the licenseeresponded to PRA RAI 97 and stated that the seal package modeled in the PRAsupporting the LAR is based on the FlowServe N9000 seals and that the FlowserveN9000 seal package will be installed. The response also states that LAR Attachment S,Table S-2, item 22 also requires update of the PRA to reflect the as-built modifications.

a) Provide technical design and testing evaluations that support the RCP seal PRAmodel.

b) Summarize the differences and similarities between the FlowServe RCP PRAmodel in the PRA and the PRA models in "Model for Failure of RCP Seals GivenLoss of Seal Cooling in CE NSSS Plants," WCAP-16175-P-A, Rev. 0, March2007 (ADAMS Accession No. ML071130391). In addition, discuss the seal logicmodel and the basic events values assumed in the FPRA.

c) Summarize whether any testing will be required to confirm the projected reliabilityof the seals and how such testing will be reflected in the FlowServe RCP PRA.

d) Implementation Item 22 does not discuss the actions that will be taken should thechange in risk for the updated Fire PRA model following installation of the as-builtmodifications not meet the RG 1.174 risk guidelines. Identify when a confirmatoryevaluation of the achieved NFPA-805 transition change in risk that includes theinstalled and tested seals will be completed, and what action(s) will be takenshould the RG 1.174 risk guidelines not be met.

SCE&G Response:

a) VC Summer used information in WCAP-16175-P-A. The same design and testingevaluations that support the WCAP were relied upon.

b) WCAP-16175-P-A includes a three stage model and a four stage model, neitherof which has the additional abeyance seal. VC Summer will be installing a threestage seal with the additional abeyance seal. Since WCAP-16175-P-A does nothave an abeyance seal model, this feature was conservatively not credited. Theoutput of the WCAP-16175-P-A model is a list of failure probabilities for theN9000 seals that depend on exposure interval, isolation of controlled bleed offflow, and time.

The incorporation of the results of the three stage N9000 model into the VCSNSPRA required fault tree changes in the loss of component cooling water (LCCW),


loss of service water (LSW), and station blackout fault tree logic. Also, theprobability of events for consequential reactor coolant pump seal LOCA and coreuncovery during LCCW, LSW, and blackout sequences were modified torepresent the N9000 seals.

The table below shows basic event values used for the N9000 model in the PRA.

Event Name Description New BE Adj. BE

CNU_1 CORE IS UNCOVERED AT 14 HOURS 1.57E-03(WITH RCS COOLDOWN)

CNU_10 CORE IS UNCOVERED AT 5 HOURS 2.47E-04 1.57E-01(LOSS OF CCW AND LOSS OF SWINITIATING EVENTS)



CNU_41 CORE IS UNCOVERED AT 4 HOURS 1.43E-04(WITH RCS COOLDOWN, NOACCUMULATORS)

CNU_5 CORE IS UNCOVERED AT 10 HOURS 1.57E-03(NO RCS COOLDOWN)

CNU_5SUCCES SUCCESS OF CNU_5 N/ASCNU_6 CORE IS UNCOVERED AT 6 HOURS 8.12E-04

(NO RCS COOLDOWN)

CNU_61 CORE IS UNCOVERED AT 6 HOURS 8.12E-04(NO RCS COOLDOWN NOACCUMULATORS, EFW FAILS AT 4HO

CNU_61SUCCE SUCCESS OF CNU_61 N/ASSCNU_62 CORE IS UNCOVERED AT 6 HOURS 8.12E-04

(NO RCS COOLDOWN EFW FAILS AT4 HOURS)

CNU_62SUCCE SUCCESS OF CNU_62 N/ASSCNU_6SUCCES SUCCESS OF CNU_6 N/ASCNU_7SW CORE IS UNCOVERED AT 4 HOURS 1.430E-04 9.11E-02

(NO RCS COOLDOWN)


Event Name Description New BE Adj. BE

CNU_7SBO CORE IS UNCOVERED AT 4 HOURS(NO RCS COOLDOWN) 6.00E-04

CNU_7SWSUC SUCCESS OF CNU_7_SW N/ACNU_7SBOSUC SUCCESS OF CNU_7_SBO N/ACNU_81 CORE IS UNCOVERED AT 1 HOUR

(NO RCS COOLDOWN) 0.00E+00

CNU_82 CORE IS UNCOVERED AT 1 HOUR(NO RCS COOLDOWN) 0.00E+00

CNU_83 CORE IS UNCOVERED AT 1 HOUR(NO RCS COOLDOWN, PZR PORV 1.OOE+00STUCK OPEN)

CNU 83SUCCE SUCCESS OF CNU_83 O.OOE+00SSCNU_9 CORE IS UNCOVERED AT 1 HOUR

(LOSS OF CCW AND LOSS OF SW 2.89E-04 1.84E-01INITIATING EVENTS)

RCPCONSLO PROBABILITY OF CONSEQUENTIAL(NON-SBO) RCP SEAL LOCA 1.57E-03

The "New BE" numbers in the table above were determined from values and models inWCAP-16175-P using failure probabilities for an N9000 seal in a 3 stage seal model.The "Adj. BE" numbers for some CNU basic events are the "New BE" numbers dividedby the number for an RCP Consequential seal LOCA (1.57E-03). The adjustment ismade because RCPCONSLO was used as a factor in the loss of CCW and loss ofservice water fault trees for all sequences except LSW-22 and LCCW-22 (which containfailure of the RCPs to trip).Values for CNU_81 and CNU_82 (core uncovered at 1 hour, no RCS cooldown) are setto zero in the baseline PRA model. It was deemed inappropriate to model these as beingworse for an N9000 seal so the value was retained.The CNU "Success" values were removed from the model. For the N9000 model, thevalues for these success events is approximately 1.0 so not modeling them has no effecton the results.CNU_7 appeared in the loss of service water model, the loss of CCW model and thestation blackout model. Since the station blackout events are treated as having less than50 degrees subcooling and the loss of CCW and loss of service water events are treatedas having greater than 50 degrees subcooling, CNU_7 was split into different events asshown in the table above.

c) FlowServe is conducting additional seal testing to support longer coping times forloss of seal cooling events and will publish an updated N9000 PRA model. Thatmodel will also include the abeyance seal. VC Summer anticipates that the


revised model will be available by the time the other NFPA 805 modifications areimplemented and the FPRA is updated to reflect the as-built modifications.

d) The FPRA will be updated to reflect the as-built modifications in accordance withthe VC Summer engineering guideline PSA-08 "PRA MODEL UPDATES" afterimplementation of the modifications. Should the validation/update of the modelto reflect as-built modifications provide results that do not meet RG 1.174 riskguidelines, actions will be taken to restore compliance with the guidelines. Theseactions may include re-analysis, additional modeling, procedure changes, orhardware changes to the plant. The course of action taken will be specific to theissue that is causing RG 1.174 not to be met. Additional details of the updateprocess are included in the response to PRA RAI 101.

PRA RAI 101

In a letter dated October 10, 2013 (ADAMS Accession No. ML12297A218) the licenseeresponded to PRA RAI 13. In a letter dated November 26, 2013 (ADAMS Accession No.ML13333A280) the licensee provided an updated LAR Attachment S, Table S-2 andprovided a new Implementation Item (Item 22) to validate/update the FPRA model toreflect the as-built modifications and to verify that the reported change-in-risk is eitherless than that estimated in the LAR Attachment W, or is within the guidance of RG1.174. However, the implementation item does not discuss the actions to be taken if RG1.174 guidelines are not met.

Describe the process that will ensure appropriate actions are taken if RG 1.174guidelines are not met that will ensure that additional analysis and/or additional plantmodifications will be made to meet RG 1.174 guidelines. Also, discuss the process forupdating the FPRA to reflect completion of other implementation items in addition to as-built modifications.

SCE&G Response:

VC Summer maintains an open items database to track issues that may warrant PRAmodel changes/updates. PRA model updates are performed in accordance withengineering guideline PSA-08 "PRA MODEL UPDATES." Items to be addressed in anupdate are found in the following PSA-08 guidance:

- Review plant and industry changes that have occurred since the last modelupdate. Changes to items such as the following should be considered for inclusionin the review:

1. Plant Operating Experience - Licensee Event Reports, Maintenance Ruleunavailability and functional failure data, and IST Data


2. Plant Design changes (ECRs and NCs with "Repair" and "Accept-as-is"

dispositions

3 Design documents referenced in the most recent PRA model Calculation

4. Changes in PRA technology, including items like new or updated codes andmethods

5. Operator Training Program

6. Technical Specifications

7. Surveillance Test Procedures (primarily for test interval)

8. Engineering Calculations

9. Emergency and Abnormal Operating Procedures

10. System Operating Procedures

11. Emergency Plan

12. Industry Studies

13. Maintenance Policies

14. Severe Accident Management Guides

15. Station Monthly Operating Report

16. PRA Open Items Database

17. Equipment History Data

18. Risk ranking data

19. Fire Pre-Plans

20. Emergency Plan Procedures

21. Condition Reports (for Fires and other events)


22. Discussions with Fire Protection Sr. Engineer

23. Offsite Power Recovery Data/Reports

24. PCCKS (Electrical Cable Routing Program)

25. Fire Modeling Database

26. HRA Studies, assumptions, and methodologies

27. Circuit Analysis (e.g. methodology, changes in circuit design,routing,coordination, etc..)

The frequency of updates defined in PSA-08 is as follows:

6.1 Frequency of Updates

6.1.1 The need for a PRA model update is to be evaluated and documented priorto startup from each refueling outage. This evaluation can be performedmore frequently if it is determined that the model does not accuratelyrepresent the plant in terms of supporting PRA applications.

6.1.2 Established thresholds will determine the frequency of PRA model updatesregarding plant modifications or changes.

A. The established threshold requiring a PRA model update is a greaterthan an estimated 25% change in CDF or LERF for Units 1, 2, and 3.Items which exceed the established threshold warrant an immediatePRA model update. This will be done as soon as practicableconsistent with the required change importance and the applicationsbeing used.

B. If an item does not meet the threshold, it will be tracked andincorporated into the next model update.

C. If the estimated cumulative effect of multiple items exceeds theestablished threshold, an immediate PRA model update is warranted.This will be done as soon as practicable consistent with the requiredchange importance and the applications being used.

6.1.3 Complete model updates should be made at least every other cycle. Thetotal time between the distributions of complete model updates should notexceed four years.


As part of the plant change process, modifications are reviewed for inclusion in the PRAmodel and their impact conservatively estimated prior to implementing the modificationin order to ensure continued compliance with RG 1.174 risk guidelines.

Should the validation/update of the model to reflect as-built modifications provide resultsthat do not meet RG 1.174 risk guidelines, actions are taken to restore compliance withthe guidelines. These actions may include re-analysis, additional modeling, procedurechanges or even hardware changes to the plant. The course of action taken will bespecific to the issue that is causing RG 1.174 not to be met.