ML23068A024

RAI Issuance Fuel Handling Trolley LAR

ML23068A024
Person / Time
Site:	Surry
Issue date:	03/08/2023
From:	John Klos NRC/NRR/DORL/LPL2-1
To:	Geoffrey Miller Dominion Energy Co
References
Download: ML23068A024 (1)

Text

John Klos From: John Klos Sent: Wednesday, March 08, 2023 8:04 AM To: gary.d.miller@dominionenergy.com Cc: John Klos

Subject:

Formal release of RAIs for Surry Fuel Handling Trolley LAR

Gary, The following requests for information are being released formally based on a 30 day calendar response time of Friday April 7th, 2023.

BACKGROUND By letter dated May 11, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22131A351), Dominion Energy Virginia submitted a license amendment request (LAR) for Surry Power Station (SPS), Units 1 and 2. The proposed amendment would use a risk-informed approach to demonstrate that the fuel handling trolley support structure (FHTSS), as designed, meets the intent of a tornado-resistant structure under the current SPS licensing basis for a 360 miles per hour (mph) maximum tornado wind speed.

The licensee provided supplemental information by letter dated July 11, 2022 (ML22192A075).

REGULATORY BASIS The U.S. Nuclear Regulatory Commission (NRC) issued construction permits for Surry Power Station (SPS)

Units 1 and 2 before May 21, 1971. Consequently, SPS Units 1 and 2 were not subject to the requirements in Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Domestic Licensing of Production and Utilization Facilities, Appendix A, General Design Criteria (GDC) for Nuclear Power Plants," see SECY 223, Resolution of Deviations Identified during the Systematic Evaluation Program, dated September 18, 1992 (ADAMS Accession No. ML003763736). In its letter dated May 11, 2022, the licensee stated that SPS UFSAR [3], Section 1.4.2, "Performance Standards," Section 1.4.40, "Missile Protection," Section 2.2.2.1, "Tornadoes," and Section 15.2.3, 'Tornado Criteria," meet the intent of GDC 2 and GDC 4.

SPS UFSAR, Rev. 54, (ML22283A015) Section 1.4.2, states, in part, that Those systems and components of reactor facilities that are essential to the prevention of accidents that could affect the public health and safety or to the mitigation of their consequences are designed, fabricated, and erected in accordance with performance standards that enable the facility to withstand, without loss of the capability to protect the public, the additional forces that might be imposed by natural phenomena such as earthquakes, tornadoes, flooding conditions, winds, ice, and other local site effects. The design bases so established reflect (a) appropriate consideration of the most severe of these natural phenomena that have been recorded for the site and the surrounding area, and (b) an appropriate margin for withstanding forces greater than those recorded, in view of uncertainties about the historical data and their suitability as a basis for design.

SPS UFSAR Appendix 14B, states, in part, that The analysis ensures that the Commissions General Design Criterion 4 is met, i.e., that all structures, systems, and components important to safety are designed to accommodate the effects of and are compatible with the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents, including loss-of-coolant accidents (LOCAs). These structures, systems, and components are protected against dynamic effects, including the effects of missiles, pipe whipping, and discharging fluids that may result in equipment failures and from events and conditions outside the nuclear power unit.

Regulatory Guide 1.174, Revision 3, An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis, (ML17317A256) describes an approach that is 1

acceptable to the NRC staff for developing risk-informed applications for a licensing basis change that considers engineering issues and applies risk insights.

RAI APLC-1: Demonstration of RG 1.174 Acceptance Guidelines In its submittal dated May 11, 2022, the licensee stated that the proposed approach for risk-informed analysis utilizes the acceptance criteria in RG 1.174, Revision 3, An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis, (ML17317A256) similarly to how they were applied in NUREG-1738, Technical Study of Spent Fuel Pool Accident Risk at Decommissioning Nuclear Power Plants, February 2001 (ML010430066).

Appendices 4C, Pool Performance Guideline [PPG], and 4D, Change in Risk Associated with EP

[Emergency Preparedness] Relaxations, of NUREG-1738 examine the spent fuel pool risk in decommissioning plants and states that conformance with the recommended PPG will assure that demonstrate decommissioning risk will continue to meet the Commissions quantitative health objectives (QHOs).

Appendix 4C states that the concepts of RG 1.174 can be applied in the regulation of spent fuel pools.

However, Appendix 4C states:

For decommissioning plants, the risk is primarily due to the possibility of a zirconium fire with the spent fuel cladding. The consequences of such an event do not equate directly to either a core damage accident or a large early release as modeled for an operating reactor.

RG 1.174 provides acceptance guidelines in terms of core damage frequency (CDF), large early release frequency (LERF), change in CDF (CDF), and change in LERF (LERF). Appendix 4D of NUREG-1738 translates the RG 1.174 acceptance guidelines into metrics that are applicable for evaluating spent fuel pool risk. Table 4 in Appendix 4D compares risk with RG 1.174 acceptance guidelines including early fatalities, population dose, individual early fatality risk, and individual latent cancer fatality risk.

In its letter dated July 11, 2022, the licensee provided a justification for applying the RG 1.174 acceptance guidelines for CDF and LERF. The licensee stated that the proposed risk measure of spent fuel damage frequency (SFDF) was compared to the CDF acceptance guideline since there is no impact to CDF related to this application. The licensee also stated that the increase in LERF associated with this request was determined to be zero. Finally, the licensee stated that the frequency of dose to the public was not used in this application because SFDF and LERF were effective in characterizing the risk impact of the proposed change.

Please address the following:

a. Demonstrate how the RG 1.174 acceptance guidelines are satisfied using the approach in NUREG-1738, which translates the RG 1.174 acceptance guidelines for applicability to changes in spent fuel pool risk measured by early fatalities, population dose, individual early fatality risk, and individual latent cancer fatality risk.

b. Discuss conservatisms included in the demonstration performed in response to part a such as assumptions related to the Fujita scale, failure modes and thresholds of the FHTSS, fuel damage to the spent fuel, potential radioactive release after fuel damage, and environmental conditions affecting dose to the public.

RAI APLC-2: Demonstration of RG 1.174 Principles of Risk-Informed Decision-Making In its letter dated July 11, 2022, , the licensee provided a summary of how the proposed change meets the five principles of risk-informed decision-making in RG 1.174. However, this summary did not provide sufficient detail for the staff to understand how all principles of risk-informed decision-making are met for the proposed change.

Please provide further justification for how the proposed change meets all five principles of risk-informed regulation in RG 1.174, including:

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a. Principle 1: The proposed licensing basis change meets the current regulations unless it is explicitly related to a requested exemption (i.e., a specific exemption under 10 CFR 50.12).

b. Principle 2: The proposed licensing basis change is consistent with the defense-in-depth philosophy.

This justification should address the seven considerations in RG 1.174 and include the dominant risk contributors and the plant systems and operator actions that mitigate these dominant risk contributors.

c. Principle 3: The proposed licensing basis change maintains sufficient safety margins. This justification should identify conservatisms included in the analyses supporting the proposed change. This justification may refer to the response to the previous RAI to demonstrate how this principle is met.

d. Principle 4: When proposed licensing basis changes result in an increase in risk, the increases should be small and consistent with the intent of the Commissions policy statement on safety goals for the operations of nuclear power plants. This justification may refer to the response to the previous RAI to demonstrate how this principle is met.

e. Principle 5: The impact of the proposed licensing basis change should be monitored using performance measurement strategies. This justification should describe how the proposed change will be monitored (e.g., the aging management programs that ensure the structural performance of the fuel handling trolley support structure remains consistent with the as-built design).

Thanks in advance, John Klos DORL Mcguire, Surry Licensing Project Manager U.S. NRC, Office of Nuclear Reactor Regulation (NRR),

Division of Operating Reactor Licensing (DORL),

NRC/NRR/DORL/LPL2-1, MS O9E3 Washington, DC 20555-0001 301.415.5136, John.Klos@NRC.gov 3