ML18275A275
| ML18275A275 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 10/10/2018 |
| From: | Michael Orenak Plant Licensing Branch IV |
| To: | Bement R Arizona Public Service Co |
| Orenak M | |
| References | |
| CAC MF6576, CAC MF6577, CAC MF6578, EPID L-2015-LLA-0001 | |
| Download: ML18275A275 (6) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 October 10, 2018 LICENSEE:
Arizona Public Service Company FACILITY:
Palo Verde Nuclear Generating Station, Units 1, 2, and 3
SUBJECT:
SUMMARY
OF SEPTEMBER 14, 2018, CLARIFICATION CALL WITH ARIZONA PUBLIC SERVICE TO DISCUSS THE INCOMPLETE RESPONSES IN THE LETTER DATED MAY 18, 2018, REGARDING THE ADOPTION OF RISK INFORMED COMPLETION TIMES (CAC NOS. MF6576, MF6577, and MF6578; EPID L-2015-LLA-0001)
On September 14, 2018, a clarification call was held regarding incomplete responses contained in a letter dated May 18, 2018 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18138A480) from Arizona Public Service Company (APS, the licensee) regarding four U.S. Nuclear Regulatory Commission (NRC) staff questions provided on April 4, 2018 (ADAMS Accession No. ML18094B112). During this call, the NRC staff and APS discussed a path forward and schedule to receiving these answers in a timely fashion.
Background
By letter dated July 31, 2015 (ADAMS Accession No. ML15218A300), APS submitted a license amendment request (LAR) to modify the Palo Verde Nuclear Generating Station (Palo Verde),
Units 1, 2, and 3 Technical Specifications (TSs) to implement a risk-informed completion time (RICT) program. By letter dated May 18, 2018, APS provided a response to an NRC staff request for additional information (RAI). In this response, APS indicated that the following responses assumed the completion of the following activities that would be performed in the future:
In RAI 11, the NRC staff requested a summary of the June 2017 fact and observation findings (F&Os) process regarding (1) whether each F&O resolution constitutes a probabilistic risk assessment (PRA) upgrade or maintenance upgrade (2) rationale for determining the adequacy for closure of each finding in relation to the affected portions of the associated supporting requirement (SR) for every SR and weakness identified in the F&O, (3) description of remote reviewer's participation, and (4) the confirmation that every weakness in each F&O has been addressed, that a closed finding has been achieved (for applicable F&Os ), and that the documentation has been formally incorporated in the PRA Model of Record before closure in the final F&O closure report.
APS stated that they will perform an F&O closure review to document how these four items were met.
In RAI 16, the NRC staff requested that the licensee confirm that the screening criteria in the American Society of Mechanical Engineers/American Nuclear Society (ASME/ANS) RA-Sa-2009 PRA Standard SRs IE-C6, SY-A15, and SY-813 are met for screening out the reactor coolant pump (RCP) seal loss-of-coolant accident. If not met, the licensee should discuss its plans to resolve this issue prior to implementing the RICT program.
APS stated that prior to implementation of the RICT program, they will revisit the evaluation of the RCP seal leakage as an initiating event and impact on mitigation functions as described in SRs IE-C6, SY-A15, and SY-813.
In RAI 21, the NRC staff requested that APS identify changes made to the PRA in response to all other RAls for this proposed amendment, and provide the estimated core damage frequency (CDF) and large early release frequency (LERF) values that incorporate all changes and modifications. Additionally, APS should propose a plan to incorporate those changes that affect total baseline CDF and LERF values prior to implementation of the RICT program.
The licensee stated that it will provide the updated PRA model CDF and LERF values after changes described in other RAI responses are incorporated.
As such, the letter dated May 18, 2018, also included a proposed license condition that would restrict usage of the RICT program until these activities had been completed.
The NRC staff had previously stated that the above information will be needed to complete the review prior to issuing the amendment. During an audit conducted on February 20-22, 2018, the NRC staff discussed with Mr. Hooks of the APS staff that the above information will be needed to complete the review. On April 4, 2018, the NRC staff submitted official RAls to APS, formally requesting responses to the above information. On May 3, 2018, APS requested a clarification call regarding the RAls with NRC staff and Mr. Hooks acknowledged during this call that the above information will be provided at a later date, but prior to issuance of the amendment. However, the May 18, 2018, letter from APS was not responsive to the above RAls because the requested information would not be provided prior to issuance of the amendment.
In addition, in response to RAI 17(f), APS stated that they plan to update the manual suppression rates with the updated mean values provided in NUREG-2169, "Nuclear Power Plant Fire Ignition Frequency and Non-Suppression Probability Estimation Using the Updated Fire Events Database," Table 5-1, "Probability distribution for rate of fires suppressed per unit time," dated January 2015 (ADAMS Accession No. ML15016A069). However, APS did not include an implementation item to update the manual suppression rates and incorporate the updates into its Fire PRA.
On August 7, 2018, the NRC staff held a clarification call with APS staff to discuss the forthcoming responses and the response timeline. Mr. Dilorenzo and Mr. Cox of the APS staff indicated that APS planned to respond in October, however, this timeline was well over the maximum of 90 days normally allowed for RAI responses by the NRC staff. On August 9, 2018, the NRC staff informed Mr. Cox of the APS staff that the information responsive to the RAls was expected to be received by September 10, 2018. On August 29, 2018, an e-mail was received from Mr. Cox requesting additional clarification regarding these four questions and a new response timeline. Consequently, a call was held on September 14, 2018, and is summarized below.
Clarification Call Summary Immediately after introductions, the NRC staff stated that they will be expecting a letter in the near term where APS outlines the schedule for the responses to the four outstanding questions.
The APS Regulatory Affairs Director, Mr. Thomas Weber, discussed the reason for the delayed RAI responses. He specifically cited the current heavy workload of his PRA staff due to an emergent potential greater-than-green finding at one of the Palo Verde units.
The NRC and APS discussed the following aspects of each of the four outstanding RAI responses, as listed below:
- 1) For RAI 11, the NRC staff stated they were expecting that all F&O weaknesses would be addressed, including a mapping between the 1998 Combustion Engineering Owners Group checklist and the current ASME/ANS PRA Standard RA-Sa-2009. If the full F&O report is provided, the licensee should identify if there are more PRA updates that need peer review.
- 2) For RAI 16, the licensee stated that the RCP seal loss of coolant accident will not be screened out of the internal events PRA.
- 3) For RAI 17(f), the licensee stated that they will submit an implementation item to update the manual suppression rates and incorporate the updates into their Fire PRA.
- 4) For RAI 21, the licensee stated that completing this RAI is the most time consuming and challenging, but understands the request.
After the discussion of the RAls, the licensee and NRC staff discussed the response timelines.
The NRC and APS agreed that the responses to RAls 11 and 16 would be submitted by September 21, 2018, and that RAls 17(f) and 21 would be submitted by October 5, 2018.
The responses to RAls 11 and 16 were received by the NRC staff on September 21, 2018 (ADAMS Accession No. ML18264A318) and the responses to RAls 17(f) and 21 were received on October 5, 2018 (ADAMS Accession No. ML18278A295).
Please direct any inquiries to me at 301-415-3229 or Michael.Orenak@nrc.gov.
Docket Nos. STN 50-528, STN 50-529, and STN 50-530
Enclosure:
List of Attendees
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Michael D Orenak, Project Manager Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
LIST OF ATTENDEES SEPTEMBER 14, 2018, CLARIFICATION CALL WITH ARIZONA PUBLIC SERVICE COMPANY REGARDING INCOMPLETE RESPONSES TO QUESTIONS FOR THE RISK-INFORMED COMPLETION TIMES LICENSE AMENDMENT REQUEST PALO VERDE NUCLEAR GENERATING STATION, UNITS 1, 2, AND 3 DOCKET NOS. STN 50-528, STN 50-529, AND STN 50-530 NAME Michael Orenak Michael Franovich Stacy Rosenberg Jonathan Evans Ed Miller Mihaela Biro Robert Pascarelli Thomas Weber Michael Dilorenzo Matthew Cox Carl Stephenson Paul Hom Tom Hook Sarah Kane ORGANIZATION U.S. Nuclear Regulatory Commission (NRC)
NRC NRC NRC NRC NRC NRC Arizona Public Service Company (APS)
APS APS APS APS APS APS Enclosure
ML18275A275 OFFICE NRR/DORL/LPL4/PM NRR/DORL/LPL4/LA NRR/DORL/LPL4/BC NRR/DORL/LPL4/PM NAME MOrenak PBlechman RPascarelli MOrenak DATE 10/09/18 10/03/18 10/10/18 10/10/18