ML21237A136

Amendment Request Regarding Risk-Informed Approach to Closure of Generic Safety Issue 191

ML21237A136
Person / Time
Site:	Callaway
Issue date:	08/23/2021
From:	Meyer S Ameren Missouri, Union Electric Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
Shared Package
ML21237A135	List: ML21237A136 ML21237A137 ML21237A138 ULNRC-06683, Enclosure 3: Callaway, Unit 1, Amendment Request Regarding Risk-Informed Approach to Closure of Generic Safety Issue 191 - CAL Roverd Results Baseline (Non-Isolable Breaks)
References
EPID L-2021-LLA-0059, ULNRC-06683
Download: ML21237A136 (4)

Text

Callaway Plant

.t August 23, 2021 ULNRC-06683 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 10 CFR 50.90 Ladies and Gentlemen:

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

RENEWED FACILITY OPERATING LICENSE NPF-30 TRANSMITTAL OF DOCUMENTS IDENTIFIED FROM NRC AUDIT OF LICENSE AMENDMENT REQUEST REGARDING RISK-INFORMED APPROACH TO CLOSURE OF GENERIC SAFETY ISSUE 191 (EPID L-2021-LLA-0059)

References:

1. Ameren Missouri letter ULNRC-06526, "Request for License Amendment and Regulatory Exemptions for a Risk-Informed Approach to Address GSI-191 and Respond to GL 2004-02 (LDCN 19-0014)," dated March 31, 2021 (ADAMS Accession No. ML21090A185)

2. Ameren Missouri letter ULNRC-06651, "Supplement to Request for License Amendment and Regulatory Exemptions for a Risk-Informed Approach to Address GSI-191 and Respond to GL 2004-02 (LDCN 19-0014)," dated July 22, 2021 (ADAMS Accession No. ML21203A193)

3. NRC letter from Mr. M. L. Chawla to Mr. F. M. Diya, "Callaway Plant, Unit No. 1 - Audit Plan and Setup of Online Reference Portal for License Amendment Request Regarding Risk-Informed Approach for Closure of Generic Safety Issue-191 (EPID L-2021-LLA-0059)," dated July 23, 2021 (ADAMS Accession No. ML21197A063)

In the letter identified as Reference 3, the Nuclear Regulatory Commission staff transmitted its plan for audit of the Union Electric Company (Ameren Missouri) combined request for regulatory exemptions and license amendment that was proposed for addressing GSI-191 and responding to Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors," for the Callaway plant. The combined

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ULNRC-06683 August 23, 2021 Page 2 of 4 request was submitted in the letter identified as Reference 1, and has been supplemented by the letter identified as Reference 2.

During the conduct of the audit, the audit team identified certain information as being necessary for analysis of the combined request. This information consists of inputs to, and calculational output results of, the CASA Grande software that is used to implement the risk-informed "RoverD" method for addressing concerns about accident-generated debris in the Callaway Plant containment and its potential effects on sump performance and core cooling as described in References 1 and 2.

The requested information is hereby provided in the enclosures to this letter. Enclosure 1 contains break frequencies from NUREG-1829, loss-of-coolant accident (LOCA) data, and the Callaway Plant non-isolable weld break locations that are input to CASA Grande. Enclosure 2 contains the CASA Grande debris generation and transport output data for the critical weld break locations. Enclosure 3 contains the debris generation and transport output data for breaks at each of the non-isolable weld locations that was obtained using CASA Grande at a reduced resolution for break orientation and break size increments. The Enclosure 3 data is provided in order to allow the NRC staff to validate the process that was used to identify the critical weld break locations.

This letter does not contain new commitments.

If there are any questions, please contact Mr. Tom Elwood at 314-225-1905.

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

Sincerely, Steve J. Meyer Manager, Regulatory Affairs 08/23/2021 Executed on: ___________________

Enclosures:

Enclosure 1 - Callaway Baseline Weld Input Enclosure 2 - CAL RoverD Results Baseline (Critical Breaks)

Enclosure 3 - CAL RoverD Results Baseline (Non-Isolable Breaks)

ULNRC-06683 August 23, 2021 Page 3 of 4 cc: Mr. Scott A. Morris 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. M. Chawla Project Manager, Callaway Plant Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 08B1A Washington, DC 20555-0001

ULNRC-06683 August 23, 2021 Page 4 of 4 Index and send hardcopy to QA File A160.0761 Hardcopy:

Certrec Corporation 6500 West Freeway, Suite 400 Fort Worth, TX 76116 (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 B. L. Cox F. J. Bianco S. P. Banker B. L. Jungmann E. C. Olson S. M. Lange S. J. Meyer R. C. Wink T. B. Elwood R. J. Andreasen NSRB Secretary STARS Regulatory Affairs Mr. Jay Silberg (Pillsbury Winthrop Shaw Pittman LLP)

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