ML18278A295

Response to Request for Additional Information for Risk-Informed Completion Times Supplemental Responses for Items 17.f and 21

ML18278A295
Person / Time
Site:	Palo Verde
Issue date:	10/05/2018
From:	Lacal M Arizona Public Service Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
102-07801-MLL/MDD
Download: ML18278A295 (10)

Text

10 CFR 50.90 Qaps MARIA L. LACAL Senior Vice President Nuciear Reguiatory and Oversight Palo Verde 102-07801-MLL/MDD Nuclear Generating Station P.O. Box 52034 October 5, 2018 Phoenix, AZ 85072 Mail station 7605 Tel 623.393.6491 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

References:

1. Arizona Public Service Company (APS) Letter 102-07060, License Amendment Request to Revise Technical Specifications to Adopt TSTF-505-A, Revision 1, Risk-Informed Completion Times, dated July 31, 2015 [Agencywide Documents Access and Management System (ADAMS) Accession number ML15218A300]

2. APS Letter 102-07587, License Amendment Request Supplement for Risk-Informed Completion Times, dated November 3, 2017 (ADAMS Accession number ML17307A188)

3. APS Letter 102-07691, APS Response to Request for Additional Information for Risk-Informed Completion Times, dated May 18, 2018 (ADAMS Accession number ML18138A480)

4. APS Letter 102-07796, Response to Request for Additional Information for Risk-Informed Completion Times, dated September 21, 2018 (ADAMS Accession number ML18264A318)

Subject:

Palo Verde Nuclear Generating Station Units 1, 2, and 3 Docket Nos. STN 50-528, 50-529, and 50-530 Response to Request for Additional Information for Risk-Informed Completion Times Supplemental Responses for Items 17.f and 21 On Juiy 31, 2015, as supplemented by letter dated November 3, 2017, APS submitted a iicense amendment request (LAR) to modify the Palo Verde Nuclear Generating Station (PVNGS) Technical Specification requirements to permit the use of risk-informed compietion times in accordance with Risk-Informed Technical Specification Task Force Initiative 4b, References 1 and 2, respectiveiy.

During the week of February 20, 2018, the NRC staff conducted an audit at PVNGS to gain an understanding of the pianned risk-informed compietion time program at PVNGS and to review the probabiiistic risk assessment modei that will be used by APS for this risk-informed LAR. The NRC staff communicated that additional Information was required to complete their review and APS responded to the request for additional information (RAI) in Reference 3. Following conference calls with the NRC staff on August 7, and September 14, 2018, APS agreed to provide supplemental information regarding four of the RAIs that were originally responded to in Reference 3. Two of the four (RAI 11 and RAI 16) were responded to in Reference 4, which also included A member of the STARS Alliance, LLC Callaway

• Diablo Canyon

• Palo Verde

• Wolf Creek

102-07801-MLL/MDD ATTN: Document Control Desk U.S. Nuclear Regulatory Commission APS Response to RAIs for Risk-Informed Completion Times Items 17.f and 21 Page 2 responses to NRC questions provided by NRC letter dated August 23, 2018. The enclosure to this letter provides the additional information for the remaining two RAIs (RAI 17.f and RAI 21) as described in Reference 4.

APS has reviewed the information supporting a finding of no significant hazards consideration previously provided to the NRC in Reference 1. APS has concluded that the information provided in this response does not affect the basis for concluding that the proposed license amendment does not involve a significant hazards consideration under the standards set forth in 10 CFR 50.92.

No new commitments are being made to the NRC by this letter.

Should you need further information regarding this letter, please contact Michael D.

DiLorenzo, Nuclear Regulatory Affairs, at (623) 393-3495.

By copy of this letter, this RAI response is being forwarded to the Arizona Department of Health Services in accordance with 10 CFR 50.91(b)(1).

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

Executed on: October 5. 2018 (Date)

Sincerely, MLL/MDD/PJH/sma

Enclosure:

APS Response to Request for Additional Information for Risk-Informed Completion Times Supplemental Responses for Items 17.f and 21 cc: K. M. Kennedy NRC Region IV Regional Administrator M. D. Orenak NRC NRR Project Manager for PVNGS C. A. Peabody NRC Senior Resident Inspector for PVNGS T. Morales Arizona Department of Health Services - Bureau of Radiation Control (ADHS)

ENCLOSURE APS Response to Request for Additional Information for Risk-Informed Completion Times Supplemental Responses for Items 17.f and 21 Attachment 1 - Updated PVNGS RICT PRA Implementation Items

Enclosure APS Response to RAIs for Risk-Informed Completion Times Supplemental Responses for Items 17.f and 21 Introduction On July 31, 2015, as supplemented by letter dated November 3, 2017, Arizona Public Service Company (APS) submitted a license amendment request (LAR) to modify the Palo Verde Nuclear Generating Station (PVNGS) Technical Specification (TS) requirements to permit the use of risk-informed completion times (RICT) in accordance with Risk-Informed Technical Specification Task Force (RITSTF) Initiative 4b [Agencywide Documents Access and Management System (ADAMS) Accession numbers ML15218A300 and ML17307A188].

During the week of February 20, 2018, the NRC staff conducted an audit at PVNGS to gain an understanding of the risk-informed completion time program at PVNGS and to review the probabilistic risk assessment (PRA) model that will be used by APS for this risk-informed LAR. The NRC staff communicated that additional information was required to complete their review and APS responded by letter numbers 102-07691, 102-07716, and 102-07796 dated May 18, June 1, and September 21, 2018 respectively (ADAMS Accession numbers ML18138A480, ML18152B874, and ML18264A318).

Following conference calls with the NRC staff on August 7, and September 14, 2018, APS agreed to provide supplemental information regarding four of the RAIs that were originally responded to in the APS letter dated May 18, 2018. Two of the four RAIs (RAI 11 and RAI 16) were responded to in the APS letter dated September 21, 2018, which also included responses to NRC questions from an August 23, 2018 letter to APS. This enclosure provides the additional information for the remaining two RAIs (RAI 17.f and RAI 21) as described in APS letter number 102-07796, dated September 21, 2018.

The APS response is provided after each RAI.

RAI 17 APLA - Fire PRA Methods

f. Please confirm that the manual suppression probabilities are consistent with NUREG/CR-6850, EPRI [Electric Power Research Institute]/NRC-RES [Office of Nuclear Regulatory Research] Fire PRA Methodology for Nuclear Power Facilities," Volume 2, Appendix P (ADAMS Accession No. ML050940189), in that these are not less than the 0.001 floor.

APS Response to RAI 17.f The manual suppression rates are updated with the mean values provided in NUREG-2169, Nuclear Power Plant Fire Ignition Frequency and Non-Suppression Probability Estimation Using the Updated Fire Events Database, January 2015, Table 5-1, Probability Distribution for Rate of Fires Suppressed per Unit Time. A floor value of 0.001 is hard-coded into the calculations of manual non-suppression probability.

Therefore, the manual suppression probabilities are not less than the 0.001 floor, and in that respect the fire PRA model is consistent with NUREG/CR-6850. The estimated core damage frequency (CDF) and large early release frequency (LERF) values in the RAI 21 response reflect this change.

This item is complete; therefore, it is not reflected in Attachment 1, Table 1-1 as a future implementation action.

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Enclosure APS Response to RAIs for Risk-Informed Completion Times Supplemental Responses for Items 17.f and 21 RAI 21 APLA - Total CDF and LERF LAR Attachment 9, Table A9-1 provides the total baseline CDF and LERF. Completing the actions in the NRC staff's RAIs may impact the CDF and LERF values. After completing the actions in the other RAIs, please identify changes made to the PRA in response to RAIs, and provide the estimated CDF and LERF values that incorporate all changes and modifications. Also, please propose a plan to incorporate those changes that affect total baseline CDF and LERF values prior to implementation of the RICT program.

APS Response to RAI 21 The following changes were made to the PRA model in response to RAIs:

Internal Events

• The reactor coolant pump (RCP) seal leakage model from the internal fire PRA (FPRA) was incorporated in the internal events PRA model [Response to RAI 16 in ML18138A480]

• Added detailed engineered safety features actuation system (ESFAS) and reactor protection system (RPS) modeling [Response to EICB-RAI-2 In ML16102A463 and RAI 4 in ML18138A480]

Internal Fire

• Incorporated the updated fire ignition frequencies, manual suppression rates and non-suppression probabilities (NSP) provided in NUREG-2169, Nuclear Power Plant Fire Ignition Frequency and Non-Suppression Probability Estimation Using the Updated Fire Events Database [Response to RAI 17.c, 17.d and 17.f in ML18138A480]

• Incorporated the updated electrical cabinet heat release rates provided in NUREG-2178, Refining and Characterizing Heat Release Rates from Electrical Enclosures During Fire (RACHELLE-FIRE) [Response to RAI 17.c and 17.d in ML18138A480]

• Incorporated updated oil fire split fractions (counting) per NRC position, item 3, Recent Fire PRA Methods Review Panel Decisions and EPRI1022993, Evaluation of Peak Heat Release Rates in Electrical Cabinet Fires (ADAMS Accession Number ML12171A583) [Response to RAI 17.c in ML18138A480]

• Updated the KERITE cable type per FAQ 08-0053, Revision 1, Kerite-FR Cable Failure Thresholds (ADAMS Accession Number ML121440155) [Response to RAI 17.C in ML18138A480]

• Incorporated the methodology and results with respect to breaker coordination in Report 0001-0013-001-003, Revision 1, PVNGS Fire PRA Common Power Supply Associated Circuits Calculation [Response to RAI 17.b in ML18138A480]

• Incorporated additional guidance on modeling treatment for sensitive electronics per FAQ 13-0004, Revision 1, Clarification on Treatment of Sensitive Electronics (ADAMS Accession Number ML13322A085) [Response to RAI 17.C in ML18138A480]

• Incorporated the guidance in FAQ 16-0011, Revision 1, Cable Tray Ignition, for determining fire propagation through a cable tray arrangement for specific scenarios (ADAMS Accession Number ML18074A020) [Response to f^I 17.c in ML18138A480]

• Incorporated modeling for fire-induced Anticipated Transients Without Scram (ATWS) [Response to EICB-RAI-2 in ML16102A463]

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Enclosure APS Response to RAIs for Risk-Informed Completion Times Supplemental Responses for Items 17.f and 21 Seismic Incorporated the updated 2016 Seismic Hazard Analysis for PVNGS [Response to RAI 9 in ML18138A480]

Table 1 provides an estimate of the total Unit 1/2/3 baseline CDF and LERF values with these changes reflected.

A review was conducted of incorporated changes into the estimate model to determine which of these changes were upgrades and if any of the upgrades were significant to meeting the Regulatory Guide (RG) 1.174 risk limits. Table 2 of this enclosure provides a summary of the identified PRA upgrades. None of the upgrades identified in Table 2 were determined significant to meeting the risk limits in RG 1.174.

The upgrades identified in Table 2 will undergo a focused scope peer review in accordance with NEI 05-04 and any findings will be resolved prior to implementation of the RICT program. Attachment 1, Table 1-1, Item 5 identifies the PRA upgrades that are required to be completed prior to implementation of the RICT program.

Attachment 1 also contains a partial revision to Table 1-1 for the PVNGS, Units 1, 2 and 3 RICT PRA implementation items, documented in APS letter number 102-07691, dated May 18, 2018, APS Response to Request for Additionai Information for Risk-Informed Compietion Times (ADAMS Accession Number ML18138A480). This partial revision incorporates item 6 associated with a revision to procedure 40EP-9E001, Standard Post Trip Actions, as described in Table 1 below.

Table 1 Estimated Total Unit 1/2/3 Baseline CDF/LERF Hazard CDF (per reactor-yr)

Internal Events 5.1E-6 1.7E-7 Internal Flooding 4.6E-7 2.1E-8 Seismic 1.7E-5 2.2E-6 Internal Fire* 4.9E-5 5.2E-6 Total 7.2E-5 7.6E-6

• Table 1 credits a change to procedure 40EP-9EO0]L, Standard Post Trip Actions, which is in process and not yet implementeid. The change adds a contingency operator action to locally trip motor gerlerator sets power supply breakers NGN-L03C4 and NGN-L10C4. PVNGS will irnplement this change as described in Attachment 1, Table 1-1, item 6.

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Enclosure APS Response to RAIs for Risk-Informed Completion Times Supplemental Responses for Items 17.f and 21 Table 2 - Identified PVNGS PRA Model Upgrades Significant to I meeting RG 1 Impact Upgrade Upgrade Description Description 1.174 Risk 1 ID Type 1 imil-s? '

Capability PRA model change may No 2017-2021 Closure of F&O AS-03, loss of coolant accident (LOCA) Change impact significant accident modeling success criteria sequences and significant justification accident progression sequences Methodology Human-induced flooding may No 2017-2026 Closure of Internal Flooding F&O 1-2, Human-Induced Change involve a new methodology Flooding (Linked with that has not previously been Impact 2018-2526) applied in the PVNGS PRA 2017-2028 Methodology Implemented a different No Closure of F&O SHA-E2-01, Updated Seismic Hazard Change methodology for seismic Analysis hazard evaluation than previously applied 2017-2029 Capability Additional relays were No Closure of F&O SFR-F3-01, Resolve Seismic Fragility of Change included in the SPRA model Unaddressed Relays which impacted significant accident sequences and risk insights 2018-2526 Closure of Internal Flooding Methodology Human-induced flooding may No F&O IFEV-A7-01, Human- Change involve a new methodology Induced Flooding (Linked that has not previously been with Impact 2017-2026) applied in the PVNGS PRA 2018-2531 Capability More robust HRA approach No Closure of F&O SPR-B8-01, Post-Seismic Event Ex- Change may impact significant Control Room Operator accident sequences and risk Actions Alternate Paths insights Various Modeling of Fire-Induced Capability Model change to fire-induced No ATWS Change ATWS which impacted significant accident sequences and risk insights Page 4

Enclosure APS Response to RAIs for Risk-Informed Completion Times Supplemental Responses for Items 17.f and 21 Attachment 1 Updated PVNGS RICT PRA Implementation Items Page 5

Enclosure APS Response to RAIs for Risk-Informed Completion Times Supplemental Responses for Items 17.f and 21 Attachment 1 Updated PVNGS RICT PRA Implementation Items The following tables are partial revisions (e.g. adds information) to Table 1-1 and Table 1-2 from the Palo Verde Nuclear Generating Station (PVNGS), Units 1, 2 and 3 RICT PRA implementation items, identified in APS letter number 102-07691, dated May 18, 2018, APS Response to Request for Additional Information for Risk-Informed Completion Times (ADAMS Number ML18138A480). The items identified below will be addressed prior to implementation of the RICT program. Table 1-2 reflects the addition of this letter to the proposed license condition.

Partial Revision to Table 1-1 PVNGS RICT PRA Implementation Items Description Resolution

5. Seven PRA model upgrades were identified Conduct a focused scope peer review for the from a review of all PRA model changes not following PRA model upgrades:

reviewed by peer reviews:

PRA model impact 2017-2021: Closure a. PRA model impact 2017-2021: Closure of a.

of F&O AS-03, LOCA modeling success F&O AS-03, LOCA modeling success criteria criteria justification justification

b. PRA model impact 2017-2026: Closure PRA model impact 2017-2026: Closure of of Internal Flooding F&O 1-2, Human- Internal Flooding F&O 1-2, Human-Induced Induced Flooding (Linked with Impact Flooding (Linked with Impact 2018-2526) 2018-2526) c. PRA model impact 2017-2028: Closure of PRA model impact 2017-2028: Closure F&O SHA-E2-01, Updated Seismic Hazard of F&O SHA-E2-01, Updated Seismic Analysis Hazard Analysis d. PRA model impact 2017-2029: Closure of

d. PRA model impact 2017-2029: Closure F&O SFR-F3-01, Resolve Seismic Fragility of of F&O SFR-F3-01, Resolve Seismic Unaddressed Relays Fragility of Unaddressed Relays e. PRA model impact 2018-2526: Closure of

e. PRA model Impact 2018-2526: Closure Internal Flooding F&O IFEV-A7-01, Human-of Internal Flooding F&O IFEV-A7-01, Induced Flooding (Linked with Impact Human-Induced Flooding (Linked with 2017-2026)

Impact 2017-2026) PRA model impact 2018-2531: Closure of PRA model impact 2018-2531: Closure F&O SPR-B8-01, Post-Seismic Event Ex-of F&O SPR-B8-01, Post-Seismic Event Control Room Operator Actions Alternate Ex-Control Room Operator Actions Paths Alternate Paths g- Modeling of Fire-Induced ATWS g- Modeling of Fire-Induced ATWS This condition is described, in response to NRC These actions are indicated in response to NRC RAI RAI 21, in APS letter 102-07801, dated 21, in APS letter 102-07801, dated October 5, October 5, 2018. 2018.

6. Revise procedure 40EP-9E001, Standard Post Implement change to procedure 40EP-9E001, Trip Actions, to credit operator action to locally Standard Post Trip Actions, to credit operator action trip NGN-L03C4 and NGN-L10C4. to locally trip NGN-L03C4 and NGN-L10C4.

This condition is described in the response to RAI This action is indicated in response to RAI 21, in APS 21, in APS letter 102-07801, dated October 5, letter 102-07801, dated October 5, 2018.

2018.

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Enclosure APS Response to RAIs for Risk-Informed Completion Times Supplemental Responses for Items 17.f and 21 Attachment 1 Updated PVNGS RICT PRA Implementation Items Table 1-2 Additional Conditions Amendment Additional Conditions Implementation Number Date Arizona Public Service Company (APS) is approved to implement the risk-informed completion time (RICT) program specified in license amendment [NUMBER] dated

[DATE].

The risk assessment approach and methods, shall be acceptable to the NRC, be based on the as-built, as-operated, and maintained plant, and reflect the operating experience of the plant as specified in RG 1.200. Methods to assess the risk from extending the completion times must be PRA methods accepted as part of this license amendment, or other methods approved by the NRC. If the licensee wishes to use a newly developed method, and the change is outside the bounds of this license condition, the licensee will seek prior NRC approval, via a license amendment.

[NUMBER] APS will complete the implementation items listed in the Prior to implementation of Enclosure of APS letter 102-07587, dated November 3, RICT program.

2017, to the NRC and in Attachment 1, Table 1-1 of APS letter 102-07691, dated May 18, 2018, as updated by APS letter 102-07801, dated October 5, 2018, prior to implementation of RICTs. All issues identified will be addressed and any associated changes will be made, focused scope peer reviews will be performed on changes that are PRA upgrades as defined in the PRA standard (ASME/ANS RA-Sa-2009, as endorsed by RG 1.200, Revision 2), and any findings will be resolved and reflected in the PRA of record prior to implementation of the RICT program.

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