ML22329A111
| ML22329A111 | |
| Person / Time | |
|---|---|
| Issue date: | 11/30/2022 |
| From: | Vincent Gaddy NRC/RGN-IV/DORS/EB1 |
| To: | Horin W Winston & Strawn, LLP |
| Gaddy V | |
| References | |
| Download: ML22329A111 (3) | |
Text
November 30, 2022 William A. Horin, Partner Winston & Strawn LLP 1901 L Street, N.W.
Washington, D.C. 20036-3506
SUBJECT:
RESPONSE TO NUCLEAR UTILITY GROUP ON EQUIPMENT QUALIFICATIONS CONCERN WITH GENERIC IMPLICATIONS AND REQUEST FOR CLAIRIFICATION STEMMING FROM 10 CFR 50 49 NON CITED VIOLATION AT THE DIABLO CANYON POWER PLANT
Dear Mr. Horin:
Thank you for your letter dated September 27, 2022, where you raised a concern with the generic implications and requested clarifications stemming from the NRCs classification of a performance deficiency documented in NRC Inspection Report 05000275/2022011 and 05000323/2022011 (ADAMS Accession No. ML22215A284). Specifically, the inspection report documented a performance deficiency associated with a non-cited violation of 10 CFR 50.49(e)(1). As requested, a copy of your letter has been placed into the public Agencywide Documents Access and Management System (ADAMS Accession No. ML22271A885).
I would like to acknowledge your concerns and state that the NRC does not necessarily disagree with the concerns you raised. Additionally, I would like to assure you that the NRC has not changed how it applies or interprets Title 10 of the Code of Federal Regulations (10 CFR) 50.49 and that the violation is specific to Diablo Canyon Power Plant (Diablo Canyon) and should not be applied generically to other licensees. (Inspectors always need to verify whether a previously issued violation at one licensee facility applies to the plant specific design and licensing basis and relevant circumstances at another.)
The NRCs regulations in 10 CFR Part 50 require that structures, systems, and components important to safety in a nuclear power plant be designed to accommodate the effects of environmental conditions and that design control measures be used to verify the adequacy of the design. These general requirements are contained in General Design Criteria 1, 2, 4, and 23 of Appendix A to Part 50; Criteria III, XI, and XVII of Appendix B to Part 50; and 10 CFR 50.55a.
Specific requirements pertaining to qualification of certain electric equipment important to safety are contained in 10 CFR 50.49.
10 CFR 50.49 broadly covers safety-related electric equipment that is relied upon to remain functional during and following design basis events, nonsafety-related electric equipment whose failure under postulated environmental conditions could prevent satisfactory accomplishment of safety functions, and certain post-accident monitoring equipment. 10 CFR 50.49 further describes design basis events as conditions of normal operation, including anticipated operational occurrences, design basis accidents, external events, and natural phenomena (including tornadoes) for which the plant must be designed. However, 10 CFR 50.49 does later state that requirements for seismic and dynamic qualification, protection of electric equipment
W. Horin 2 against other natural phenomena and external events, and equipment located in a mild environment are not included within the scope.
The inspectors noted during the Diablo Canyon inspection that the updated final safety analysis report stated the following: a tornado is a design basis event, the tornado causes a loss of offsite power and the loss of the 480 VAC switchgear room and 125 VDC inverter room ventilation system, and manual actions are required to maintain temperature in electric equipment rooms to ensure that equipments functionality while the plant is brought to safe shutdown, and if required, cold shutdown. Furthermore, the room heat up calculation for the tornado event demonstrated that the temperature rise in certain electric equipment rooms was significantly more severe than what would occur during normal plant operation. This analysis was performed for the tornado event alone and was not in combination with a design basis accident, such as a loss-of-coolant accident. Additionally, the analyzed room temperatures exceeded the equipment control guideline area (i.e., room) temperature monitoring limits from an operability perspective. The inspectors also noted that the affected electric equipment was not included in Diablo Canyons list of equipment covered by 10 CFR 50.49.
Based upon the information above and what the inspectors understood to be the design and licensing basis at the time, the inspectors proposed the Green non-cited violation of 10 CFR 50.49 related to their concerns of the capability of safety-related electric equipment to accommodate the effects of environmental conditions following a design basis tornado event.
Diablo Canyon did not challenge the inspectors position during the inspection, nor did they contest the violation after the inspection report was issued. (Instructions for contesting a violation are provided in the cover letter to the inspection report.) Since Diablo Canyon did not provide a site-specific argument demonstrating that they cover accommodating the effects of environmental conditions from a design basis tornado event outside of 10 CFR 50.49 and through other requirements, the inspectors did not change their initial characterization of the issue. However, the NRC acknowledges that the performance deficiency could have been characterized in terms of the general requirements described previously in this letter.
I thank you again for raising your concerns and hope that I have clarified the NRCs position by providing some perspective on our decision-making and inspection process.
Sincerely, Signed by Gaddy, Vincent on 11/30/22 Vincent G. Gaddy, Chief Engineering Branch 1 Division of Operating Reactor Safety
ML22329A111 X Non-Sensitive X Publicly Available X SUNSI Review Sensitive Non-Publicly Available OFFICE SRI:RIV/DORS/EB1 SRI:RIV/DORS/EB1 RC:RIV/ORA NRR/DEX/ELTB NAME JBraisted RKopriva DCylkowski MMcConnell DATE 11/28/2022 11/29/2022 11/28/2022 11/30/2022 OFFICE BC:RIV/DORS/EB1 NAME VGaddy DATE 11/30/2022