ML24086A468
| ML24086A468 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 03/21/2024 |
| From: | Hilbert L Virginia Electric & Power Co (VEPCO) |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| 24-113 | |
| Download: ML24086A468 (1) | |
Text
VIRGINIA ELECTRIC AND POVVER COMPANY RICHMOND, VIRGINIA 23261 March 21, 2024 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Serial No.24-113 NAPS/RAP Docket Nos. 50-338, 339 License Nos. NPF-4, NPF-7 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION ENERGY VIRGINIA)
NORTH ANNA POWER STATION UNITS 1 AND 2
SUMMARY
OF FACILITY CHANGES, TESTS AND EXPERIMENTS Pursuant to 10 CFR 50.59(d)(2), a report containing a brief description of any changes, tests, and experiments, including a summary of the evaluation of each, must be submitted to the NRC, at intervals not to exceed 24 months. Attachment 1 provides a summary description of Facility Changes, Tests and Experiments identified in 10 CFR 50.59 Evaluations performed at the North Anna Power Station during 2023. Attachment 2 provides a summary description of Commitment Change Evaluations during 2023.
If you have any questions, please contact Marcus A. Hofmann at (540) 894-2100.
v:aw-Lisa Hilbert Site Vice President Attachments
- 1. 10 CFR 50.59 Summary Description of Facility Changes, Tests and Experiments
- 2. Commitment Change Evaluation Summary cc:
Regional Administrator United States Nuclear Regulatory Commission Region II Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, Georgia 30303-1257 NRC Senior Resident Inspector North Anna Power Station
ATTACHMENT 1 10 CFR 50.59
SUMMARY
DESCRIPTION OF FACILITY CHANGES, TESTS AND EXPERIMENTS NORTH ANNA POWER STATION UNITS 1 AND 2 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION ENERGY VIRGINIA)
NORTH ANNA UNITS 1 AND 2 10 CFR 50.59
SUMMARY
DESCRIPTION OF FACILITY CHANGES, TESTS AND EXPERIMENTS 10 CFR 50.59 EVALUATION PARENT DOCUMENT: ETE-NAF-2023-0017, Rev. 0 Brief
Description:
The activity being reviewed is the implementation of the PADS code based method (WCAP-17642-P-A) into the licensing basis for affected analyses at North Anna Units 1 and 2. PADS is an approved fuel thermal performance code that models fuel geometry, material properties, and heat transfer mechanisms to set initial conditions used in the transient analyses. PADS output is used as input to the RETRAN transient analysis computer code which is then used to predict system responses to postulated non-LOCA events.
Reason for Change: The use of PADS addresses the thermal conductivity degradation (TCD) issue described and addressed by Westinghouse in L TR-NRC-12-18. The activity is therefore an update of methods for analyzing non-LOCA events for which fuel thermal performance is an element of the analysis.
The ETE associated with this review (ETE-NAF-2023-0017, Rev. 0) supports a change to the North Anna UFSAR for Units 1 and 2. The change consists of text, table, and figure modifications in Chapters 4, and 15. Details of specific changes can be found in Attachment A of the ETE. The changes to the UFSAR address the technical impacts of the transition from the current version of PAD to PADS on affected analyses and descriptions of the thermal/hydraulic design, including fuel rod design parameters. The 10 CFR 50.59 applicability review identified the following changes were subject to a 10 CFR 50.59 screen:
- 1. Non-LOCA Method Changes:
- a. FSAR Chapter 4 fuel performance evaluation method (PAD 4.0 to PAD5), including the update to the fuel melt limit assumed within the safety analyses.
- 2. Safety Analysis Changes:
- a. Reanalysis of the Control Rod Ejection accident and Steam Generator Tube Rupture dose consequence analyses: The new analyses were performed to assess the impact of different fuel property inputs from PAD5 on the transients, as well as assess against the updated fuel melt limit applicable to PAD5 (for Rod Ejection only).
The activities listed above also require updates to the NAPS UFSAR.
Of the changes determined to require a screen, all changes screened in for evaluation.
Summary: The primary purpose of the changes being implemented as part of this 10 CFR 50.59 Evaluation is to capture the impact of using PAD5 to generate fuel-related inputs on affected analyses for North Anna Power Station (NAPS) Units 1 and 2. This
activity directly addresses the phenomena of thermal conductivity degradation (TCD).
Previously, the NRC released Information Notice 2009-23, which requested licensees to review the information notice and determine if TCD had been adequately addressed at each operating facility. To address this concern, Westinghouse developed an improved fuel thermal model and fuel performance evaluation code and methodology documented in WCAP-17642-PA, Revision 1, which has been approved by the NRC. The methodology and associated code, known as PADS, incorporates several improved fuel thermal performance models, including consideration of TCD with increasing burnup, compared to the current PAD 4.0 code and method described in the North Anna Power Station Updated Final Safety Analysis Report (U FSAR).
This 10 CFR 50.59 activity implements the PADS code and method into Chapter 4 of the NAPS U FSAR and implements updated Chapter 15 safety analyses to account for the use of PADS inputs at North Anna. An Evaluation is required because methods of analysis are changed from those currently described in the NAPS UFSAR and Chapter 15 safety analyses were re-run to address the use of PAD5 inputs and to ensure that the respective acceptance criteria continue to be met such that their individual design functions remain unaffected. Because of this methodology change and potentially affected SAR-described design functions, which are considered adverse changes under 10 CFR 50.59, an Evaluation is required to assess each of the eight Evaluation criteria.
The method change is solely evaluated under Criterion 8 consistent with NEI 96-07, Revision 1, Section 4.3.8, while the reanalyzed safety analyses are evaluated under Criteria 1 through 7.
The reanalyzed safety analyses continue to meet the applicable acceptance criteria ensuring the design functions remain unaffected. Because the 50.59 treatment of the reanalysis under Criteria 1 - 7 only involved input changes and all acceptance criteria continue to be met, there was no impact on frequency of occurrence of accidents or SSC malfunctions, no more than a minimal increase in radiological consequences of the accidents or via SSC malfunctions, and no potential for different accidents directly or via SSC malfunctions. The fuel melt limit, which is considered a DBLFPB, is altered as an acceptance criterion for safety analyses for which fuel melt is evaluated; however, the fuel melt limit is included in the approved WCAP-17642-P-A, Revision 1 topical, which is implemented en toto under Question 8 of the Evaluation. Finally, as the method of analysis for these events is unchanged, Criterion 8 of the Evaluation is not applicable.
As previously indicated, WCAP-17642-P-A, Revision 1 (Westinghouse's PADS model and code) is being implemented as the new fuel performance evaluation methodology at North Anna which includes incorporation into the safety analyses. PADS is NRC approved and offers improvements over the current PAD 4.0 fuel performance code/method, namely the consideration of the effects of TCD with increasing burn up.
The change in methodology is not considered a departure from a method of evaluation because PAD5 is NRG-approved, is being used for its intended application, is used within the limitations outlined in the WCAP-17642-P-A, Revision 1 SER, and it offers technical improvements over PAD 4.0. Only Criterion 8 applies to this change because it only involves a change in the method of evaluation.
Implementation of PAD5, including the reanalyzed safety analyses and use of the new fuel melt limit, may be implemented without NRC approval under the provisions of 10 CFR 50.59.
ATTACHMENT 2 Commitment Change Evaluation Summary
NORTH ANNA POWER STATION UNITS 1 AND 2 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION ENERGY VIRGINIA)
Commitment Change Evaluation Summaries Original Commitment
Description:
North Anna will perform fuel dispersal in accordance with the B.5.b. Phase 1 strategy for B.2.m.1.
Revised Commitment
Description:
In lieu of dispersal, the strategy for Spent Fuel Pool (SFP) thermal mitigation measures for North Anna Units 1 and 2 will credit time sensitive actions for SFP external makeup and SFP external spray implementation from the time plant personnel diagnose that external SFP makeup is required, as supported by NEI 06-12.
Justification for the Commitment Change:
The original NRC Order EA-02-026 requiring a SFP thermal management program was fully rescinded because the requirements were incorporated into 10 CFR 50.54 (hh)(2).
10 CFR 50.54 (hh)(2) was subsequently moved to 10 CFR 50.155 (b)(2). The revised mitigation strategy continues to maintain compliance with 10 CFR 50.155. The revised thermal mitigation strategy results in an improvement in nuclear safety by significantly reducing the number of irradiated fuel assembly movements in the SFP while ensuring that the SFP external makeup and external spray can be implemented in a timely manner.