ML25128A019
| ML25128A019 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 05/08/2025 |
| From: | Southern Nuclear Operating Co |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| EPID L-2025-LRM-0042 | |
| Download: ML25128A019 (1) | |
Text
Vogtle Electric Generating Plant Units 3 and 4 Exemption Request Request Exemption from 10 CFR 50.71(h)(2) and 50.71(h)(3) requiring upgrade of the probabilistic risk assessment (PRA) to include low power shutdown (LPSD) modes of operation Pre-submittal Meeting: May 14, 2025
Agenda
- Background
- Request
- Justification
- Schedule
BACKGROUND 10 CFR 50.71(h)(2) and 50.71(h)(3)
(h)(1) No later than the scheduled date for initial loading of fuel, each holder of a combined license under subpart C of 10 CFR part 52 shall develop a level 1 and a level 2 probabilistic risk assessment (PRA). The PRA must cover those initiating events and modes for which NRC-endorsed consensus standards on PRA exist one year prior to the scheduled date for initial loading of fuel.
(2) Each holder of a combined license shall maintain and upgrade the PRA required by paragraph (h)(1) of this section. The upgraded PRA must cover initiating events and modes of operation contained in NRC-endorsed consensus standards on PRA in effect one year prior to each required upgrade. The PRA must be upgraded every four years until the permanent cessation of operations under § 52.110(a) of this chapter.
(3) Each holder of a combined license shall, no later than the date on which the licensee submits an application for a renewed license, upgrade the PRA required by paragraph (h)(1) of this section to cover all modes and all initiating events.
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BACKGROUND 10 CFR 50.71(h)(2) and 50.71(h)(3)
Added in 2007 via 72 FR 49352 (2007-08-28)
Provisions apply only to Combined Licenses under Part 52 (h)(2) requires updates (to reflect plant design changes)
(h)(2) requires upgrades after endorsement of new consensus standards Final rule discussion did not really address the need for the upgrades.
Similar to requiring plant design upgrades? 52.63 addressed?
(h)(3) requires (when applying for license renewal) upgrade to cover all modes and all initiating events.
Final rule discussion did not really address the need for the upgrade.
must be developed even if standards do not yet exist.
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BACKGROUND 10 CFR 50.71(h)(2) and 50.71(h)(3)
- In implementing these new requirements, it is the NRCs expectation that industry stakeholders will work with the NRC and appropriate codes and standard setting bodies to continually upgrade the relevant codes and standards, identify potential issues, resolve problems, and create relevant guidance to assist in periodically improving the quality and comprehensiveness of the PRA.
- However, it remains unclear why a new scope of the PRA is necessary for Combined Licenses when currently operating plants are sufficiently safe using the currently existing low power shutdown risk tools.
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BACKGROUND UFSAR Chapter 19 - Probability Risk Assessment This section presents an overview of the Probabilistic Risk Assessment (PRA) performed for VEGP Units 3&4. The PRA models developed for VEGP Units 3&4 are based upon the generic AP1000 plant PRA model (Ref. 18) and have been upgraded to the NRC-endorsed standard (Reference 1) including site-specific information and expanded to evaluate the site seismic hazard.
Section 19.7 discusses the Shutdown Defense-In-Depth (DID) model that qualitatively assess risk in accordance with 10 CFR 50.65(a)(4).
- 1. ASME/ANS-RA-Sa 2009, Standard for Level 1/Large Early Release Frequency Probabilistic Risk Assessment for Nuclear Power Plant Applications, American Society of Mechanical Engineers, February 2009.
- 18. APP-GW-GL-022, Revision 8, AP1000 Probabilistic Risk Assessment, Westinghouse Electric, LLC, August 2007.
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REQUEST Exemption Exemption is requested to allow SNC to NOT upgrade of the probabilistic risk assessment (PRA) to include low power shutdown (LPSD) modes of operation Includes current requirement for upgrade to include LPSD if an approved standard for LPSD exists at one year prior to the required upgrade (every four years) and Includes current requirement to upgrade before submittal of an application for a renewed license.
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JUSTIFICATION 50.12 Exemption Criteria
- 1. Authorized by law No law exists that would preclude the changes covered by this exemption request.
- 2. Will not present an undue risk to the health and safety of the public The qualitative analysis and risk considerations already in use for implementation of the Maintenance Rule provide adequate determination of the risk-significance of activities related to shutdown activities without a LPSD PRA. No new insights would be expected to be identified from such a LPSD PRA.
- 3. Consistent with the common defense and security There is no change to the design, function, or operation of any structures or plant equipment that is necessary to maintain a safe and secure status of the plant. The requested exemption has no impact on plant security or safeguards procedures.
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JUSTIFICATION 50.12 Exemption Criteria (continued)
- 4. Special circumstances are present Meets the special circumstances of 10 CFR 50.12(a)(2)(ii) which specifies that a special circumstance exists whenever [a]pplication of the regulation in the particular circumstances would not serve the underlying purpose of the rule or is not necessary to achieve the underlying purpose of the rule.
The Federal Register Notice (72 FR 49352) for the final rule adding 10 CFR 50.71(h) describes the underlying purpose of 10 CFR 50.71(h)(2) and (h)(3) as an effort to improve PRA quality through support and endorsement of consensus standards on PRA methods.
However, as noted above (item 2) the qualitative analysis and risk considerations already in use for implementation of the Maintenance Rule provide adequate implementation for determination of the risk-significance of activities related to shutdown activities without imposing specific upgrade requirements to develop a LPSD PRA. No new insights would be expected to be identified from such a LPSD PRA Therefore, application of the 50.71(h)(2) and (3) requirements are not necessary to achieve the underlying purpose of the rule.
In addition, 10 CFR 50.12 (a)(2) specifies that special circumstances exist when compliance would result in undue hardship or other costs that are significantly in excess of those contemplated when the regulation was adopted, or that are significantly in excess of those incurred by others similarly situated.
Given the effectiveness in the application of DID methods to manage outage risk, application of 10 CFR 50.71(h)(2) & (3) would impose an undue cost and resource burden on VEGP 3 & 4 that is not borne by similarly situated facilities, including the other facilities in the SNC fleet.
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SCHEDULE SUBMITTAL planned by May 21, 2025 REQUEST approval by December 21, 2025 (acceptance plus 6 months) 10