RC-14-0129, Response to Request for Additional Information on License Amendment Request LAR-06-00055 and to Adopt NFPA 805

Response to Request for Additional Information on License Amendment Request LAR-06-00055 and to Adopt NFPA 805

ML14227A737
Person / Time
Site:	Summer
Issue date:	08/14/2014
From:	Gatlin T South Carolina Electric & Gas Co
To:	Shawn Williams Document Control Desk, Office of Nuclear Reactor Regulation
References
RC-14-0129
Download: ML14227A737 (27)

Text

Thomas D. Gatlin Vice President,Nuclear Operations 803.345.4342 August 14, 2014 A SCANA COMPANY RC-14-0129 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555-0001 Attn: S. A. Williams

Subject:

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

References:

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

2. Shawn A. Williams, NRC, to Thomas D. Gatlin, SCE&G, "Virgil C. Summer Nuclear Station Unit - 1 (VCSNS) - Request for Additional Information Regarding License Amendment Request to Adopt National Fire Protection Association Standard 805 (TAC NO. ME7586)" dated July 11, 2014

[ML14182A473]

South Carolina Electric & Gas Company (SCE&G), acting for itself and as agent for South Carolina Public Service Authority pursuant to 10 CFR 50.90, submitted License Amendment Request (LAR) per Reference 1 and several responses to LAR Requests for Additional Information (RAI) to adopt NFPA 805. NRC review and audit of these requests determined that additional information was required and a RAI was issued per Reference 2. The Attachment of this letter contains SCE&G's response to these RAIs. VCSNS spoke with Shawn Williams on August 7, 2014 and was granted an extension which sets August 14, 2014 as the new due date. SCE&G's response to RAI 100 will be submitted by September 30, 2014.

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

Document Control Desk LAR-06-00055 RC-14-0129 Page 2 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.

Executed on Thomas D. Gatlin/

RLP/TDG/ts

Attachment:

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

Response

c: Without Attachments unless noted K. B. Marsh S. A. Byrne J. B. Archie N. S. Carns J. H. Hamilton J. W. Williams W. M. Cherry V. M. McCree (w/Attachments)

S. A. Williams (w/Attachments)

NRC Resident Inspector S. E. Jenkins Paulette Ledbetter K. M. Sutton NSRC RTS (CR-06-00055)

File (813.20)

PRSF (RC-14-0129) (w/Attachments)

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 1 of 25 VIRGIL C. SUMMER NUCLEAR STATION UNIT 1 DOCKET NO. 50-395 OPERATING LICENSE NO. NPF-12 ATTACHMENT Probabilistic Risk Assessment (PRA) Request for Additional Information (RAI)

Response

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 2 of 25 PRA RAI 64.01 In a letter dated October 10, 2012 (Agencywide Documents Access and Management System (ADAMS) Accession Number ML12297A218), the licensee responded to PRA RAI 64 and provided the results of a sensitivity analysis from applying a variance method that incorporates component failure rate error factors in developing the mean interfacing system loss of coolant accident (ISLOCA) frequency. The results showed an increase by a factor of 3.7 in internal events core damage frequency (CDF) to 5.OE-05 per year and an increase by a factor of 145 in internal events large early release frequency (LERF) to 3.7E-05 per year. The licensee stated that these increases are dominated 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 the internal 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 in the total CDF (including internal events, fire events, and seismic events) and LERF exceeding the Regulatory Guide (RG) 1.174, "An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis," Revision 2, May 2011 (ADAMS Accession No. ML100910006) risk guidelines for Region II so that only very small risk increases are allowed. Assess the relevance of more recent data on rupture failure rate of MOVs to the analysis, including updating the contribution to total CDF and LERF from this issue.

• Alternately, additional analysis or modifications may be necessary to meet RG 1.174 guidelines. 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 in response 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 peer review of the VC Summer PRA in 2002 (F&O IE-06). The answer to this issue involved a spreadsheet using a factored approach that gave a mean value for ISLOCA frequency with a large variance as described in the question above.

The ISLOCA model for VC Summer underwent an update after F&O IE-06 was addressed. This update changed the ISLOCA model from a single number calculated outside of the fault tree (effectively a module) to explicit modeling of ISLOCA failure modes within the fault tree. These failure modes are represented by basic events with assigned error factors. The basic events are correlated by "type codes" for uncertainty studies.

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 3 of 25 With the new model, it is possible to run a monte-carlo simulation on the ISLOCA cutset file that produces uncertainty bounds and gives a new mean value for the ISLOCA initiating event frequency based on the uncertainty bounds. The result of this calculation is that the monte-carlo ISLOCA initiating event mean (5.59E-05/yr) is very close to the value calculated by the fault tree (5.56E-05/yr).

I1l EA1j 1 l Mwoo. 5.w0 U-1 :4 nE05 F1 5n 55E0 95%4 :7,23E05

,o.sdo l00

&E- 695E5 71-5 7959 5-5 65E-5 &E-5 9.5E-51104 15E4 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 overall uncertainty analysis for CDF and LERF for the new model. The CDF and LERF results for a monte-carlo analysis using 10,000 simulations are shown in the table below and demonstrate compliance with RG 1.174 risk guidelines.

Mean 5% 95%

CDF 4.15E-06 1.73E-06 8.66E-06 LERF 1.09E-07 3.19E-08 2.66E-07

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 4 of 25 PRA RAI 66.03 In a letter dated May 2, 2014, (ADAMS Accession No. ML14125A274) the licensee responded to PRA RAI 66.02 and stated that "additional cable protection modifications were added to protect the CREP panels in CB04, CB06, CB15, and CB17" and "additional cable protection modifications were added to the latest fire PRA model to protect several additional functions including prevention of spurious ESFAS, prevention of RWST draindown, isolation of spray suction, and EDG loading." It does not appear, however, that these modifications are included in the updated LAR Attachment C provided in the letter dated February 25, 2014 (ADAMS Accession No. ML14063A455), nor are they described in the updated LAR Attachment S, Table S-1, provided in the letter dated October 14, 2013 (ADAMS Accession No. ML13289A194). Identify which of the ECR modification(s) in LAR Attachment S, Table S-1 includes these "additional cable protection modifications."

In addition, describe all of the individual modifications included under this ECR modification(s), and describe where each of these individual modifications is specifically identified in the LAR to either make a VFDR (DROID) deterministically compliant or to only reduce risk.

SCE&G Response:

The "additional cable protection items" discussed in SCE&G's response to PRA RAI 66.02 (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 two existing 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 provided below including identification of why they were required, either for a DROID (VFDR), or for risk reduction.

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

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

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 5 of 25 Quantification notebook in the table "FireImpact Data - Mods". The scope of this modification has been added to ECR50810.

It should be noted that although circuits associated with this modification are described as being "protected" in the PRA RAI 66.02 response, this is only FPRA modeling terminology. 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 Feedwater control from the CREP panels is available. The goal is preservation of equipment function 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 design phase and is scheduled to be completed by the end of 2015.

Table 1 - FPRA RAI 66.03 Response Fire Area DROID ID Cable Plant ECR CB04, CB06, CB15 N/A (Risk Reduction) EFW 21B 50810 CB04, CR06, CB15 N/A (Risk Reduction) EF W 22B 50810 CB15 N/A (Risk Reduction) EF W 23B 50810 CB15 N/A (Risk Reduction) EF W 24B 50810 CB04, CB06, CB15 N/A (Risk Reduction) EFW 56B 50810 CB04, CB06, CB15 N/A (Risk Reduction) EFW 57B 50810 CB04, CB06, CB15 N/A (Risk Reduction) EFW 61A 50810 CB04, CB06, CB15 N/A (Risk Reduction) EFW 62A 50810 CB15 N/A (Risk Reduction) EFW 63A 50810 CB15 N/A (Risk Reduction) EFW 64A 50810 CB04, CB06, CB15 N/A (Risk Reduction) EFW 86A 50810 CB15 N/A (Risk Reduction) EFW 89A 50810 CB15 N/A (Risk Reduction) EFW 91B 50810 CB15 N/A (Risk Reduction) EFW 92B 50810 CB15 N/A (Risk Reduction) EFW 93B 50810 CB04, CB06, CB15 N/A (Risk Reduction) EFW 94B 50810 CB04, CR06, CB15 N/A (Risk Reduction) EFW 95B 50810 CB04, CR06, CB15 N/A (Risk Reduction) EFW 97B 50810 CB04, CB06, CB15 N/A (Risk Reduction) EFW 98B 50810 CB15 N/A (Risk Reduction) EF W 103B 50810 CB15 N/A (Risk Reduction) EF W 104B 50810

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 6 of 25 Fire Area DROID ID Cable Plant ECR CB15 N/A (Risk Reduction) EF W 109B 50810 CB04, CB06, CB15 N/A (Risk Reduction) EFW 110B 50810 CB15 N/A (Risk Reduction) EF W 111A 50810 CB15 N/A (Risk Reduction) EF W 112A 50810 CB1 5 N/A (Risk Reduction) EF W 113A 50810 CB04, CB06, CB15 N/A (Risk Reduction) EF W 114A 50810 CB15 N/A (Risk Reduction) EF W 115A 50810 CB04, CB06, CB15 N/A (Risk Reduction) EF W 116A 50810 CB15 N/A (Risk Reduction) EF W 117B 50810 CB15 N/A (Risk Reduction) EF W 122A 50810 CB15 N/A (Risk Reduction) EF W 123A 50810 CB04, CB06, CB15 N/A (Risk Reduction) EF W 128A 50810 CB15 N/A (Risk Reduction) EF W 133B 50810 CB15, CB17.01 N/A (Risk Reduction) EF W7003A 50810 CR15, CB17.01 N/A (Risk Reduction) EF W7005A 50810 CB15, CB17.01 N/A (Risk Reduction) EF W7012A 50810 CB15, CB17.01 N/A (Risk Reduction) EF W7014A 50810 CB15, CR17.01 N/A (Risk Reduction) EF W7017A 50810 CB15, CB17.01 N/A (Risk Reduction) EF W7018A 50810 CR15, CB17.01 N/A (Risk Reduction) EF W7019A 50810 CB15, CB17.01 N/A (Risk Reduction) EF W7020A 50810 CR15, CB17.01 N/A (Risk Reduction) EF W7021A 50810 CB15, CB17.01 N/A (Risk Reduction) EF W7022A 50810 CB15, CR17.01 N/A (Risk Reduction) EF W7023A 50810 CB15, CB17.01 N/A (Risk Reduction) EF W7024B 50810 CR15, CB17.01 N/A (Risk Reduction) EF W7025B 50810 CR15, CB17.01 N/A (Risk Reduction) EF W7026B 50810 CB15, CB17.01 N/A (Risk Reduction) EF W7027B 50810 CR15, CB17.01 N/A (Risk Reduction) EF W7028B 50810 CR15, CB17.01 N/A (Risk Reduction) EF W7029B 50810 CB15, CR17.01 N/A (Risk Reduction) EF W7030B 50810 CB15, CB17.01 N/A (Risk Reduction) EF W7031B 50810 CR15, CB17.01 N/A (Risk Reduction) EF W7032B 50810 CR15, CB17.01 N/A (Risk Reduction) EF W7034B 50810 CB15, CB17.01 N/A (Risk Reduction) EF W7035B 50810 CB15, CB17.01 N/A (Risk Reduction) EF W7036B 50810 CB15, CR17.01 N/A (Risk Reduction) EF W7037B 50810

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 7 of 25 Fire Area DROID ID Cable Plant ECR CB15, CB17.01 N/A (Risk Reduction) EF W7039B 50810 CB15, CB17.01 N/A (Risk Reduction) EF W7041B 50810 CB15, CB17.01 N/A (Risk Reduction) EF W7042B 50810 CB15, CB17.01 N/A (Risk Reduction) EF W7043B 50810 CB15, CB17.01 N/A (Risk Reduction) EF W7044B 50810 CB15, CB17.01 N/A (Risk Reduction) EF W7045B 50810 CB15, CB17.01 N/A (Risk Reduction) EF W7046B 50810 CB15, CB17.01 N/A (Risk Reduction) EF W7047B 50810 CB15, CB17.01 N/A (Risk Reduction) MC E7004A 50810 CB15, CB17.01 N/A (Risk Reduction) MS W7019A 50810 CB04, CB06 N/A (Risk Reduction) SG J 31A 50810 CB04, CB06 N/A (Risk Reduction) SG J 32B 50810 Additional Cable Protection Items discussed in FPRA RAI 66.02 Response that are included in the scope of ECR50784:

SCE&G's PRA RAI 66.02 response discussed cable protection of additional items to preserve several nuclear safety functions. It should be noted that although these items were described as "additional cable protection items," some of them were only newly credited in the FPRA, and have been included in the scope of ECR50784 to support the Nuclear Safety Capability Assessment (NSCA) since the original LAR submittal. Table 2 includes the requested details for these modifications. ECR50784 is in the implementation phase and all work is scheduled to be completed by the end of 2015.

Table 2 - FPRA RAI 66.03 Response Fire Area DROID ID Cable Notes Plant ECR ABO1.04 DROID-ABO1.01, CS C 82B 50784 02, 03, 04, 06, 09-10 AB01.06 DROID-ABO1.01, CS C 72B 50784 02, 03, 04, 06, 09-10 ABO1.09 DROID-ABO1.01, CS C 82B 50784 02, 03, 04, 06, 09-10 CB02 DROID-CB02-10 ED E 34B Protection of ED E 34B 50784 preserves desired function. EM C 287B does not need protection as

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 8 of 25 Fire Area DROID ID Cable Notes Plant ECR identified in the RAI 66.02 response.

CB05 DROID-CB05-04 ED E 23A Protection of ED E 23A 50784 ED E 24A and ED E 24A preserves the desired equipment function. EM C 281A and EM C 282A do not need protection as identified in the RAI 66.02 response 1B25.04 DROID-1B25.04-08 SI C 212B 50784 SP C 92B 1B25.04 DROID-1B25.04-04 CS C 302B 50784 CS C 305B 1B25.04 DROID-IB25.04-10 CS C 72B 50784 IB25.06.02 DROID-1B25.06, ES M 73X 50784 07-09 IB25.06.02 DROID-1B25.06, ES M 63X 50784 07-10 1B25.06.02 N/A (For Risk RC M 15X 50784 Reduction) RC M 25X RC M 35X Full scope of ECR50784 ECR50784 consists of circuit protection modifications including replacement of cable with fire rated cable, and installation of fire wrap. To address the request for all modifications included in ECR50784, Table 3 contains the remaining circuit protection modifications that were not identified in Table 2. The scope of ECR50784 agrees with the B-3 Table submitted under RC-14-0027 except for DROID-1B25.04.02. It was determined during ECR50784 implementation that circuit protection is not required because redundant indication is available.

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 9 of 25 Table 3 - FPRA RAI 66.03 Response Fire Area DROID ID Cable Plant ECR ABO1.10 DROID-AB.10, 13,14,15,16,17-05 RC E 5XB 50784 ABO1.08.02 DROID-ABO1.08-03 CS C 103A 50784 MSUI101D S U 3D 50784 ABO1.10 DROID-ABO1.10, 13, 14,15,16,17-01 SI U 3D ABO1.18.01 DROID-ABO1.18, 19-03 SI U 3D 50784 CB01.01 DROID-CB01-01 NI A 198D 50784 C301.01 DROID-CBOI-18 CS C 52B 50784 CS C 62B CB01.01 DROID-CB01-32 SG D 14B 50784 CB02 DROID-CB02-07 CS C 52B 50784 CS C 62B CB02 DROID-CB02-42 EF U 55A 50784 CS C 42B 50784 CB12 DROID-CB12-19 CS C 52B CS C 62B CB20 DROID-CB20-04 CS C 42B 50784 EF EF UU 4A 5A 50784 1B25.01.03 DROID-IB25.01.03, .04, .05-01 EF U 55A MS W251A 50784 DROID-IB25.01.03, .04, .05-02 MSW251A 1B25.01.03 MS W 256A 1B25.06.02 DROID-IB25.06, 07-05 VL C 12C 50784 ABO1.21.02 N/A (Risk Reduction Only) CS W 304XD 50784 CB10 N/A (Risk Reduction Only) ES M 94X 50784 CB15 N/A (Risk Reduction Only) ES E 108X 50784 Full scope of ECR50810 The purpose of plant modification ECR50810 is to provide plant enhancements and address items identified during the NFPA 805 transition process. In addition to the CREP panel protection, the current scope includes replacing sections of existing sprinkler systems, installation of additional portable fire extinguishers, raising Post Indicator Valves, installation of lock boxes and storage boxes, anchoring flammable liquid storage cabinets and modifications to address LERs 2011-001, 2011-002 and 2013-005.

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 10 of 25 PRA RAI 68.01 In a letter dated April 1, 2013 (ADAMS Accession Number ML13092A333), the licensee responded to PRA RAI 68 and explained that for grouped transient zones, (defined as zones in which all the fixed and transient ignition sources are failed completely at time zero), 120 new scenarios were identified for which walk downs showed that cable trays extend across transient zone boundaries. The NRC staff noted that these new scenarios do not appear to have been specifically included in the FPRA model, however, the results of an evaluation showed the scenarios increase the fire CDF by 1.4E-06 per year. While not significant to transition, the NRC staff notes that the self-approval acceptance guidelines are much smaller than the transition acceptance guidelines and therefore addition of these 120 new scenarios could affect post-transition plant change evaluations. Discuss how these scenarios will be included in post-transition plant change evaluations if they are not specifically modeled in the FPRA.

SCE&G Response:

The list of grouped transient zones (i.e., those transient zones where targets are failed with no credit for severity factors or nonsuppression probabilities), with potential for propagation to adjacent transient zones that are not included in the Fire PRA, was revised in order to reduce the total CDF and is provided below in Table 1. The last row of Table 1 shows that the total CDF increase for all the scenarios has been reduced to 3.47E-08 (from the 1.4E-06 reported in the earlier RAI response). The value of 3.47E-08 is low and does not affect the post-transition plant change evaluations. The CDF reduction is primarily achieved by: 1) crediting automatic sprinklers in selected scenarios, 2) crediting the hot gas layer scenario in TB02, and 3) performing detailed analysis by crediting severity factors and non suppression probabilities in selected scenarios (i.e., ungrouping the scenarios).

Technical details of the changes included in Table 1 intended to reduce total CDF are as 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 the sprinkler systems credited in these scenarios were already part of the NFPA 805 fire protection required systems.

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 11 of 25

2. A hot gas layer scenario for TB02 is included in the Fire PRA; therefore, the following 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 the targets at times shorter than propagation to adjacent transient zones within the Fire Zone, the inclusion of the scenarios is not warranted.

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

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

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 12 of 25 Table 1: CDF for Grouped Transient Zones with Potential for Propagation to Adjacent Transient Zones (Replaces Table 3 in PRA RAI 68 response, April 1, 2013, ADAMS Accession Number ML13092A333)

Base Case PNS, CDF no Exposing 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-T1 1.90E-04 N/A 0.001 1.28E-03 1.28E-03 2.43E-07 2.43E-07 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-T3 1.20E-05 N/A 0.001 1.28E-03 1.28E-03 1.54E-08 1.54E-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 ABO1.09-T3-TO-ABO1.09-T4 5.42E-06 N/A 0.001 1.42E-03 1.56E-03 7.70E-09 7.70E-09 ABO1.09-T4-TO-ABO1.09-T3 3.70E-05 N/A 0.006 1.28E-03 1.56E-03 4.74E-08 4.74E-08 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

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 13 of 25 Base Case PNS, CDF no Exposing 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 ABO1.18.02-T4-TO-ABO1.18.02-T5 2.76E-04 N/A 0.001 4.12E-07 1.50E-06 1.14E-10 1.14E-10 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-T5-TO-ABO1.18.02-T7 2.32E-04 N/A 1 2.09E-08 8.67E-07 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 ABO1.18.02-T9-TO-ABO1.18.02-T8 1.29E-05 N/A 1 2.02E-08 2.02E-08 Note 1 Note 1 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-T11-TO-ABO1.21.02-T7 6.37E-04 N/A 1 4.14E-07 4.14E-07 Note 1 Note 1 ABO1.21.02-T12-TO-ABO1.21.02-T11 4.01E-04 N/A 0.001 4.12E-07 2.26E-04 2.56E-10 1.65E-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-T11 6.13E-05 N/A 1 4.14E-07 4.14E-07 Note 1 Note 1 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 ABO1.29-T3-TO-ABO1.29-T2 5.27E-04 N/A 1 NA NA Note 2 NA

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 14 of 25 Base Case PNS, CDF no Exposing Automatic PNS, Manual CCDP no CCDP with propagation Scenario ID IGF Suppression Suppression propagation propagation Total CDF considered ABO1.29-T3-TO-ABO1.29-T4 5.27E-04 N/A 1 NA NA Note 2 NA ABO1.29-T4-TO-ABO1.29-T3 5.15E-04 N/A 1 NA NA Note 2 NA 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-T7-TO-CB04-T8 9.84E-06 N/A 1 NA NA Note 2 NA CB04-T9-TO-CB04-T1O 3.92E-06 N/A 1 NA NA Note 2 NA CB20-T1-TO-CB20-T2 1.53E-05 N/A 1 NA NA Note 2 NA CB20-T2-TO-CB20-T1 2.90E-06 N/A 1 NA NA Note 2 NA CB20-T2-TO-CB20-T3 2.90E-06 N/A 1 NA NA Note 2 NA CB20-T3-TO-CB20-T2 1.62E-05 N/A 1 NA NA Note 2 NA CB20-T3-TO-CB20-T4 1.62E-05 N/A 1 NA NA Note 2 NA CB20-T4-TO-CB20-T3 3.06E-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-T2-TO-IB20-T3 7.55E-04 N/A 0.479 1.96E-05 1.96E-05 1.48E-08 1.48E-08 IB20-T3-TO-IB20-T2 5.34E-04 N/A 0.479 1.96E-05 1.96E-05 1.05E-08 1.05E-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-T8 1.17E-04 N/A 0.479 1.96E-05 9.87E-05 6.73E-09 2.29E-09

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 15 of 25 Base Case PNS, CDF no Exposing Automatic PNS, Manual CCDP no CCDP with propagation Scenario ID IGF Suppression Suppression propagation propagation Total CDF considered IB20-T4-TO-IB20-T9 1.1 7E-04 N/A 1 1.96E-05 7.11 E-06 Note I Note 1 IB20-T5-TO-IB20-T4 3.78E-04 N/A 0.479 1.96E-05 1.96E-05 7.41E-09 7.41E-09 IB20-T8-TO-IB20-T1 2.62E-04 N/A 0.479 9.87E-05 9.87E-05 2.59E-08 2.59E-08 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 IB25.01.03-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

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 16 of 25 Base Case PNS, CDF no Exposing Automatic PNS, Manual CCDP no CCDP with propagation Scenario ID IGF Suppression Suppression propagation propagation Total CDF considered 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 1 TI301.02-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 transient zone. In order to apportion the ignition frequency correctly, only one combination per exposing transient zone is included in the calculation.

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

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 17 of 25 Table 2: Additional Scenarios Added to the Fire PRA Model for Ungrouped Transient Zone TB101.01 -T2 Equipment Equipment Type Fire Zone Equipment ID Equipment Description Type Description Scenario TBO1.01 DPN1X DC DISTRIBUTION PANEL 1X EC Electrical 2 cabinets TBO1.01 DPN2X DC POWER PANEL EC Electrical 2 cabinets TBO1.01 H2-TBO1.01-12-03 H2 piping in the building H2 Misc. Hydrogen 2 Fires TBO1.01 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/cutting TBO1.01 XPNO100 IAM MOUNTING PANEL FOR IB EC Electrical 2 PRE-ACTION SYS cabinets TBO1.01 XPN5142 LOC CONTR STAT FOR EC Electrical 2 XPP0042A cabinets TBO1.01 XPP0042A CONDENSATE PUMP A PMP Pumps 2 TB01.01 XPP0042A CONDENSATE PUMP A ZOl Fire with 100% 2 of Oil TBO1.01 XPP0042A CONDENSATE PUMP A Z02 Fire with 10% of 2 Oil TBO1.01 XPP0042B CONDENSATE PUMP B PMP Pumps 2 TBO1.01 XPP0042B CONDENSATE PUMP B ZOl Fire with 100% 2 of Oil TB01.01 XPP0042B CONDENSATE PUMP B Z02 Fire with 10% of 2 Oil TBO1.01 XPP0042C CONDENSATE PUMP C PMP Pumps 2 TB01.01 XPP0042C CONDENSATE PUMP C ZOl Fire with 100% 2 of Oil TB01.01 XPP0042C CONDENSATE PUMP C Z02 Fire with 10% of 2 Oil TBO1.01 XPP0075A EXHAUST HOOD SPRAY PUMP A PMP Pumps 2 TB01.01 XPP0075A EXHAUST HOOD SPRAY PUMP A ZO1 Fire with 100% 2 of Oil TB01.01 XPP0075A EXHAUST HOOD SPRAY PUMP A Z02 Fire with 10% of 2 Oil TBO1.01 XPP0075B EXHAUST HOOD SPRAY PUMP B PMP Pumps 2 TBO1.01 XPP0075B EXHAUST HOOD SPRAY PUMP B ZO1 Fire with 100% 2 of Oil TB01.01 XPP0075B EXHAUST HOOD SPRAY PUMP B Z02 Fire with 10% of 2 Oil

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 18 of 25 PRA RAI 85.02 In a letter dated November 26, 2013 (ADAMS Accession No. ML13333A280), the licensee responded to PRA RAI 85.01 and stated that the FPRA is currently being updated based on changes due to RAI responses and that the model has been converted to use the most recent version of the FRANX software that will allow uncertainties 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 98 and stated that the updated uncertainty analysis utilizing this capability supports the conclusion that the estimated CDF and LERF are not significantly affected by state-of-knowledge correlations (SOKC). Clarify if delta (A) CDF and ALERF are significantly affected 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 risk guidelines.

SCE&G Response:

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

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

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 19 of 25 PRA RAI 97.01 In a letter dated January 9, 2014 (ADAMS Accession No. ML14013A074), the licensee responded to PRA RAI 97 and stated that the seal package modeled in the PRA supporting the LAR is based on the FlowServe N9000 seals and that the Flowserve N9000 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 PRA model.

b) Summarize the differences and similarities between the FlowServe RCP PRA model in the PRA and the PRA models in "Model for Failure of RCP Seals Given Loss of Seal Cooling in CE NSSS Plants," WCAP-16175-P-A, Rev. 0, March 2007 (ADAMS Accession No. ML071130391). In addition, discuss the seal logic model and the basic events values assumed in the FPRA.

c) Summarize whether any testing will be required to confirm the projected reliability of 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 the change in risk for the updated Fire PRA model following installation of the as-built modifications not meet the RG 1.174 risk guidelines. Identify when a confirmatory evaluation of the achieved NFPA-805 transition change in risk that includes the installed and tested seals will be completed, and what action(s) will be taken should 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 testing evaluations that support the WCAP were relied upon.

b) WCAP-16175-P-A includes a three stage model and a four stage model, neither of which has the additional abeyance seal. VC Summer will be installing a three stage seal with the additional abeyance seal. Since WCAP-16175-P-A does not have an abeyance seal model, this feature was conservatively not credited. The output of the WCAP-16175-P-A model is a list of failure probabilities for the N9000 seals that depend on exposure interval, isolation of controlled bleed off flow, and time.

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

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 20 of 25 loss of service water (LSW), and station blackout fault tree logic. Also, the probability of events for consequential reactor coolant pump seal LOCA and core uncovery during LCCW, LSW, and blackout sequences were modified to represent 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 SW INITIATING EVENTS)

CNU_2 CORE IS UNCOVERED AT 12 HOURS 6.690E-04 (WITH RCS COOLDOWN)

CNU_4 CORE IS UNCOVERED AT 4 HOURS 1.43E-04 (WITH RCS COOLDOWN)

CNU_41 CORE IS UNCOVERED AT 4 HOURS 1.43E-04 (WITH RCS COOLDOWN, NO ACCUMULATORS)

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

CNU_5SUCCES SUCCESS OF CNU_5 N/A S

CNU_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 NO ACCUMULATORS, EFW FAILS AT 4 HO CNU_61SUCCE SUCCESS OF CNU_61 N/A SS CNU_62 CORE IS UNCOVERED AT 6 HOURS 8.12E-04 (NO RCS COOLDOWN EFW FAILS AT 4 HOURS)

CNU_62SUCCE SUCCESS OF CNU_62 N/A SS CNU_6SUCCES SUCCESS OF CNU_6 N/A S

CNU_7SW CORE IS UNCOVERED AT 4 HOURS 1.430E-04 9.11E-02 (NO RCS COOLDOWN)

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 21 of 25 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/A CNU_7SBOSUC SUCCESS OF CNU_7_SBO N/A CNU_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+00 STUCK OPEN)

CNU 83SUCCE SUCCESS OF CNU_83 O.OOE+00 SS CNU_9 CORE IS UNCOVERED AT 1 HOUR (LOSS OF CCW AND LOSS OF SW 2.89E-04 1.84E-01 INITIATING 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 in WCAP-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 divided by the number for an RCP Consequential seal LOCA (1.57E-03). The adjustment is made because RCPCONSLO was used as a factor in the loss of CCW and loss of service water fault trees for all sequences except LSW-22 and LCCW-22 (which contain failure of the RCPs to trip).

Values for CNU_81 and CNU_82 (core uncovered at 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, no RCS cooldown) are set to zero in the baseline PRA model. It was deemed inappropriate to model these as being worse for an N9000 seal so the value was retained.

The CNU "Success" values were removed from the model. For the N9000 model, the values for these success events is approximately 1.0 so not modeling them has no effect on the results.

CNU_7 appeared in the loss of service water model, the loss of CCW model and the station blackout model. Since the station blackout events are treated as having less than 50 degrees subcooling and the loss of CCW and loss of service water events are treated as having greater than 50 degrees subcooling, CNU_7 was split into different events as shown in the table above.

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

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 22 of 25 revised model will be available by the time the other NFPA 805 modifications are implemented 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 with the VC Summer engineering guideline PSA-08 "PRA MODEL UPDATES" after implementation of the modifications. Should the validation/update of the model to reflect as-built modifications provide results that do not meet RG 1.174 risk guidelines, actions will be taken to restore compliance with the guidelines. These actions may include re-analysis, additional modeling, procedure changes, or hardware changes to the plant. The course of action taken will be specific to the issue that is causing RG 1.174 not to be met. Additional details of the update process are included in the response to PRA RAI 101.

PRA RAI 101 In a letter dated October 10, 2013 (ADAMS Accession No. ML12297A218) the licensee responded 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 and provided a new Implementation Item (Item 22) to validate/update the FPRA model to reflect the as-built modifications and to verify that the reported change-in-risk is either less than that estimated in the LAR Attachment W, or is within the guidance of RG 1.174. However, the implementation item does not discuss the actions to be taken if RG 1.174 guidelines are not met.

Describe the process that will ensure appropriate actions are taken if RG 1.174 guidelines are not met that will ensure that additional analysis and/or additional plant modifications will be made to meet RG 1.174 guidelines. Also, discuss the process for updating 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 PRA model changes/updates. PRA model updates are performed in accordance with engineering guideline PSA-08 "PRA MODEL UPDATES." Items to be addressed in an update are found in the following PSA-08 guidance:

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

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

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 23 of 25

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 and methods

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)

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 24 of 25

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 prior to startup from each refueling outage. This evaluation can be performed more frequently if it is determined that the model does not accurately represent the plant in terms of supporting PRA applications.

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

A. The established threshold requiring a PRA model update is a greater than an estimated 25% change in CDF or LERF for Units 1, 2, and 3.

Items which exceed the established threshold warrant an immediate PRA model update. This will be done as soon as practicable consistent with the required change importance and the applications being used.

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

C. If the estimated cumulative effect of multiple items exceeds the established threshold, an immediate PRA model update is warranted.

This will be done as soon as practicable consistent with the required change importance and the applications being used.

6.1.3 Complete model updates should be made at least every other cycle. The total time between the distributions of complete model updates should not exceed four years.

Document Control Desk Attachment LAR-06-00055 RC-14-0129 Page 25 of 25 As part of the plant change process, modifications are reviewed for inclusion in the PRA model and their impact conservatively estimated prior to implementing the modification in order to ensure continued compliance with RG 1.174 risk guidelines.

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