ULNRC-06469, Submittal of Request for Extension of Seismic Probabilistic Risk Assessment

Submittal of Request for Extension of Seismic Probabilistic Risk Assessment

ML18318A059
Person / Time
Site:	Callaway
Issue date:	11/14/2018
From:	Banker S Ameren Missouri, Union Electric Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
ULNRC-06469
Download: ML18318A059 (5)

Text

.... ,, Callaway Plant MISSOURI Niib 14; 20 18 ULNRC-06469 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-000 1 10 CFR 50.54(f)

Ladies and Gentlemen:

DOCKET NUMBER 50-483 CALLAWAY PLANT UNIT 1 UNION ELECTRIC CO.

RENEWED FACILITY OPERATING LICENSE NPF-30 REQUEST FOR EXTENSION OF SEISMIC PROBABILISTIC RISK ASSESSMENT SUBMITTAL

References:

1 . NRC Letter, Request for Information Pursuant to Title 1 0 ofthe Code of Federal Regulations

50. 54(f) Regarding Recommendations 2.1, 2.3, and 9.3 ofthe Near-Term Task Force Review oflnsights from the Fukushima Daiichi Accident, dated March 12, 2012 (ML12053A340)

2. ULNRC-06102, Ameren Missouri Seismic Hazard and Screening (CEUS Sites) Response to NRC Request for Information Pursuant to 10 CFR 50.54(1) Regarding Recommendation 2. 1 of the Near-Term Task Force Review of Insights from the Fukushima Daiichi Accident, dated March 28, 2014 (ML14090A448) 3 . NRC Letter, Final Determination of Licensee Seismic Probabilistic Risk Assessments Under the Request for Information Pursuant to Title 1 0 of the Code of Federal Regulations 50.54(f)

Regarding Recommendation 2. 1 Seismic ofthe Near-Term Task Force Review of Insights from the Fukushima Daiichi Accident, dated October 27, 201 5 (ML15194A015)

4. ULNRC-06377, Request For Extension of Seismic Probabilistic Risk Assessment Submittal, dated June 15, 2017 (ML17166A474)

5. NRC Letter, Callaway Plant, Unit 1 NRC Response to Request for Extension of Seismic Probabilistic Risk Assessment Submittal, dated August 22, 2017 (ML17200D113)

6. NRC Letter, Callaway Plant, Unit 1 Staffreview of Spent Fuel Pool Evaluation Associated with Reevaluated Seismic Hazard Implementing Near-Term Task Force Recommendation 2. 1:

Seismic, dated January 23, 2018 (ML18003B419)

STARS Alliance

ULNRC-06469 November 14, 2018 Page 2 of 5 Union Electric Company (Ameren Missouri) hereby requests an extension ofthe December 3 1, 2018, due date for submittal ofthe Seismic Probabilistic Risk Assessment (SPRA) for Callaway Plant Unit 1.

Ameren Missouri is requesting that the due date be extended to September 30, 2019.

On March 12, 2012, the Nuclear Regulatory Commission (NRC) issued Reference 1 to all power reactor licensees and holders of construction permits in active or deferred status. Enclosure 1 of Reference 1 requested each addressee located in the Central and Eastern United States (CEUS) to submit a Seismic Hazard Evaluation and Screening Report. Reference 2 provided the Seismic Hazard and Screening Report for Callaway Plant. Based on the results of the screening evaluation provided in Reference 2, it was determined that Callaway Plant screens in for a required risk evaluation in the form of a Seismic PRA (SPRA), a spent fuel pool evaluation, and a high frequency confirmation (relay chatter) evaluation. Reference 3 was issued by the NRC and provided the required submittal dates for the SPRAs and remaining high frequency and spent fuel pool seismic evaluations in order for licensees to complete their responses to the March 12, 2012 request for information (Reference 1). In Reference 4, Callaway requested an extension of the submittal date for the SPRA until December 3 1 201 8 In Reference 5, the NRC approved the extension request for the SPRA and the corresponding seismic Mitigating Strategies Assessment (MSA).

Ameren Missouri has completed the spent fuel pooi evaluation for Callaway Unit 1 as reviewed by the NRC per Reference 6. The effects ofhigh frequency exceedance on plant equipment will be assessed as part ofthe SPRA.

In order to complete the SPRA evaluation for the Callaway Plant, an extension of 9 months beyond the current December 3 1 201 8 due date is needed. This would move the submittal date to September 30, 2019. Ameren Missouri discussed the need for this extension with NRC staffvia telephone in October 20 1 8 As noted in that discussion, the in-progress results received for Callaways SPRA are not believed to be a realistic representation of the seismic risk at the plant. Since the first extension request, the focus has been on identifying possible drivers for those results and performing refinements to the SPRA model. Until recently, these refinement efforts were largely unsuccessful in developing significant changes in the model results. Refinement efforts made within the past 3 months, however, appear to be more impactful, and the SPRA model is beginning to identify drivers and more realistic insights into the seismic risk for the Callaway Plant. To support the NRC performing an effective review of the results, additional time is required to fully complete the seismic PRA refinement and analysis that realistically quantifies the seismic risk at Callaway Plant.

A peer review was performed of the Callaway SPRA in accordance with NET 12-1 3 External ,

Hazards PRA Peer Review Process Guidelines, in June of2Ol8. The peer review team concluded that the Callaway SPRA meets most of the PRA Standard requirements. However, the peer review team noted that a number of the modeling approaches in the fragility analysis and plant response analysis for the Callaway SPRA are overly conservative and have resulted in a seismic CDF result that appears unrealistic for this plant design and operation.

ULNRC-06469 November 14, 2018 Page 3 of 5 Following the peer review, the seismic PRA model has been used to guide and prioritize a number of refinements to the fragility analysis for specific components. Consequentially, the current risk estimates and insights are converging to results that are more in line with expectations and industry experience. None of the fragility refinements required advanced fragility analysis techniques or any assumptions for modification to the plant. The refinements are based instead on more realistic estimates and treatment of either the existing seismic demand or the actual seismic capacity of individual components. The Callaway risk profile is extremely flat (i.e., no individual components are driving the risk estimates) which is an indication of a balanced design, but it also means that a relatively large number of fragility refinements are needed for a more realistic risk estimate.

In addition to the unanticipated flat risk profile and resultant extensive refinements required, the Callaway SPRA initial proj ect schedule did not provide an adequate amount of time to complete the SPRA Peer Review and then resolve the resulting Facts and Observations. The effort to resolve the Facts and Observations resulting from the Peer Review effort typically requires a six-month duration.

With the extension of the $PRA submittal date, Ameren Missouri will have adequate time to address the Facts and Observations and utilize the NRC endorsed method to conduct an Independent Assessment Team process to closeout the Facts and Observations.

Ameren Missouri has developed a detailed schedule for the required activities, and it indicates that the final Callaway Unit 1 SPRA can be submitted to the NRC on or before September 30, 2019. Ameren Missouri is therefore requesting that the SPRA submittal due date be extended to that date.

Depending on the results of the SPRA, a seismic M$A could be required. If a seismic MSA is required for the Callaway Plant, an extension until December 3 1 201 9 is requested. This provides an additional three months to complete the MSA evaluation beyond the SPRA submittal date.

Continued plant operation during the extension period is justified based on considerations that include consistency with the NRC overall schedule for submittal of all Near-Term Task Force related plant SPRAs, the defense-in-depth provided by compliance with all NRC Orders regarding beyond design basis events, completion ofthe NRC endorsed Expedited Seismic Evaluation Process and all actions identified by that process, the inherent nuclear power plant design margins, and completion of the evaluation demonstrating the beyond design basis seismic robustness of the Callaway Plant Unit 1 spent fuel pool. No plant vulnerabilities have been identified and no safety concerns have been raised by the continuous review of the insights from the in-process SPRA for the Callaway Plant. Therefore, there is no undue risk associated with delaying submittal of the SPRA results for NRC review.

This letter does not contain new commitments. If you have any questions, please contact Justin Hiller at 314-225-1 141 or Bruce Huhmann at 573-694-6741.

Sincerely, Stephanie Banker Vice President, Engineering

ULNRC-06469 November xx, 2018 Page 4 of 5 cc: Mr. Kriss M. Kennedy Regional Administrator U. S. Nuclear Regulatory Commission Region IV 1600 East Lamar Boulevard Arlington, TX 76011-4511 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman, MO 65077 Mr. L. John Klos Project Manager, Callaway Plant Office ofNuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 09E3 Washington, DC 20555-0001

ULNRC- 06469 November xx, 2018 Page 5 of 5 Index and send hardcopy to QA File A160.0761 Hardcopy:

Certrec Corporation 6100 Western Place, Suite 1050 FortWorth,TX 76107 (Certrec receives ALL attachments as long as they are non-safeguards and may be publicly disclosed.)

Electronic distribution for the following can be made via Responses and Reports ULNRC Distribution:

F. M. Diya T. E. Herrmann B. L. Cox S. P. Banker F. J. Bianco R. C. Wink T. B. Elwood J. W. Hiller B. E. Huhmann Corporate Communications NSRB Secretary STARS Regulatory Affairs Mr. Jay Silberg (Pillsbury Winthrop Shaw Pittman LLP)