ML23346A039

Supplemental Information Needed for Acceptance of Requested Licensing Action Request for Relief from Requirements of ASME Code, Section Xl, Examination and Testing Unbonded Post-Tensioning System

ML23346A039
Person / Time
Site:	Callaway
Issue date:	12/14/2023
From:	Mahesh Chawla NRC/NRR/DORL/LPL4
To:	Diya F Callaway Energy Center
References
EPID L-2023-LLR-0061
Download: ML23346A039 (1)

Text

December 14, 2023

Mr. Fadi Diya Senior Vice President and Chief Nuclear Officer Ameren Missouri Callaway Energy Center 8315 County Road 459 Steedman, MO 65077

SUBJECT:

CALLAWAY PLANT, UNIT NO. 1 - SUPPLEMENTAL INFORMATION NEEDED FOR ACCEPTANCE OF REQUESTED LICENSING ACTION RE:REQUEST FOR RELIEF FROM REQUIREMENTS OF ASME CODE, SECTION XI, SUBSECTION IWL EXAMINATION AND TESTING OF THE UNBONDED POST-TENSIONING SYSTEM (EPID L-2023-LLR-0061)

Dear Mr. Diya:

By letter dated October 26, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23299A195), Union Electric Company, doing business as Ameren Missouri (the licensee), submitted a request for relief from the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, subsection IWL regarding examination and testing of the unbonded post-tensioning system (Relief Request C3R-01) for Callaway Plant, Unit No. 1. ASME Code,Section XI, subsection IWL requires periodic visual examination of containment concrete as well as visual examination and physical testing of the post-tensioning system. The licensee proposes extending the interval for post-tensioning system examinations and testing and detailed visual examination of concrete adjacent to tendon bearing plates from 5 years to 10 years.

The purpose of this letter is to provide the results of the U.S. Nuclear Regulatory Commission (NRC) staffs acceptance review of this proposed alternative. The acceptance review was performed to determine if there is sufficient technical information in scope and depth to allow the NRC staff to complete its detailed technical review. The acceptance review is also intended to identify whether the application has any readily apparent information insufficiencies in its characterization of the regulatory requir ements or the licensing basis of the plant.

Pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(1) and 10 CFR 50.55a(z)(2), the applicant shall demonstrate that the proposed alternatives would provide an acceptable level of quality and safety, or that compliance with the specified requirements of 10 CFR 50.55a would result in hardship or unusual difficulty without a compensating increase in the level of quality or safety.

F. Diya

The NRC staff has reviewed your application and concluded that the information delineated in the enclosure to this letter is necessary to enable the NRC staff to make an independent assessment regarding the acceptability of the proposed alternative in terms of regulatory requirements for the protection of public health and safety and the environment.

In order to make the application complete, the NRC staff requests that the licensee supplement the application to address the information requested in the enclosure by December 29, 2023.

This will enable the NRC staff to begin its detailed technical review. If the information responsive to the NRC staffs request is not received by th e mutually agreed upon date, the application will not be accepted for review pursuant to 10 CFR 2.101, Filing of application, and the NRC will cease its activities associated with the application. If the application is subsequently accepted for review, you will be advised of any further information needed to support the staffs detailed technical review by separate correspondence.

A clarification call was conducted with your representatives on December 11, 2023. Following the clarification call, the timeframe in this letter was discussed and agreed upon by Thomas Elwood of your staff.

If you have any questions, please contact me at 301-415-8371 or via email at Mahesh.Chawla@nrc.gov.

Sincerely,

Mahesh L. Chawla, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Docket No. 50-483

Enclosure:

Supplemental Information Needed

cc: Listserv

SUPPLEMENTAL INFORMATION NEEDED

PROPOSED ALTERNATIVE TO ASME CODE, SECTION XI REQUIREMENTS REGARDING

EXAMINATION AND TESTING OF THE UNBONDED POST-TENSIONING SYSTEM

UNION ELECTRIC COMPANY

CALLAWAY PLANT, UNIT 1

DOCKET NOS. 50-483

By letter dated October 26, 2023 (Agencywi de Documents Access and Management System (ADAMS) Accession No. ML23299A195), Union Electric Company, doing business as Ameren Missouri, (the licensee) submitted a request for relief from the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, Subsection IWL regarding examination and testing of the unbonded post-tensioning system (Relief Request C3R-01) for Callaway Plant, Unit No. 1. ASME Code,Section XI, subsection IWL requires periodic visual examination of containment concrete as well as visual examination and physical testing of the post-tensioning system. The licensee proposes extending the interval for post-tensioning system examinations and testing and detailed visual examination of concrete adjacent to tendon bearing plates from 5 years to 10 years.

The U.S. Nuclear Regulatory Commission (NRC) staff noticed in section 2.1, Proposed Program Changes, of enclosure 2, Callaway Power Station Containment Post-Tensioning System In-Service Inspection Technical Report, Basis for Proposed Extension of Examination Interval, Revision 0, to the application, that the licensee requested duration of the proposed alternative for multiple containment inservice ins pection (CISI) intervals (i.e., extend the interval of post-tensioning system examinations and test s and detailed visual examination of concrete adjacent to tendon bearing plates from 5 years to 10 years with future examinations to be performed in accordance with the following schedule: 2028 (45th), 2038 (55th), 2048 (65th),

2058 (75th).

It is the NRC staffs understanding that this relief request only seeks NRCs approval through the 40th year. However, the staff does not find the proposed alternative beyond the 45 th year reasonable, and thus does not provide an acceptable level of quality and safety, because:

(1) the staff only allows for a one-time interval extension based on its review of the plant specific testing results and operating experience provided in the relief request; (2) the proposed alternative may allow undetected degradations every 5 years to advance for up to 10 years before taking the necessary corrective actions to preserve the intended function of the unbonded post-tensioning system; (3) the staff does not find it reasonable to extend the CISI intervals for the fourth 10-year interval and beyond, without reviewing the results of the IWL CISI inspections conducted prior to the initiation of the subsequent CISI interval; and (4) the staff has not authorized such requests beyond a one 10-year interval for any plant, even though requests for authorization through end of license were made for at least three recent similar proposed alternative requests for unbonded post-tensioning system inspection intervals (i.e., Palo Verde Nuclear Generating Station, Units 1, 2, and 3 (ML22124A241); Calvert Cliffs Nuclear Power Plant, Units 1 and 2 (ML21190A004); Braidwood Station, Units 1 and 2 and Byron Station, Unit Nos. 1 and 2 (ML21134A006)), and staff stated its rationale in the safety evaluations.

Enclosure

Please provide clarification of this request to confirm that the request only seeks NRCs approval through the 40 th year only. In addition, please provide a revised schedule for this approval as discussed during the clarification call with the NRC staff.

Enclosure

ML23346A039 *via email NRR-004 OFFICE NRR/DORL/LPL4/PM NRR/DORL/LPL4/LA* NRR/DEX/ESEB/BC*

NAME MChawla PBlechman ITseng DATE 12/12/2023 12/12/2023 12/13/2023 OFFICE NRR/DORL/LPL4/BC* NRR/DORL/LPL4/PM*

NAME JRankin MChawla DATE 12/14/2023 12/14/2023