ML25111A082
| ML25111A082 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 04/25/2025 |
| From: | Tony Nakanishi Plant Licensing Branch IV |
| To: | Peters K Vistra Operations Company |
| References | |
| EPID-L-2024-LLR-0079 | |
| Download: ML25111A082 (1) | |
Text
April 25, 2025 COMANCHE PEAK NUCLEAR POWER PLANT, UNIT NO. 1 - AUTHORIZATION AND SAFETY EVALUATION FOR PROPOSED ALTERNATIVE REQUEST RV-1A (EPID L-2024-LLR-0079)
LICENSEE INFORMATION Recipients Name and Address:
Mr. Ken J. Peters Executive Vice President and Chief Nuclear Officer Attention: Regulatory Affairs Vistra Operations Company LLC Comanche Peak Nuclear Power Plant 6322 N FM 56 P.O. Box 1002 Glen Rose, TX 76043 Licensee:
Vistra Operations Company, LLC (Vistra OpCo)
Plant Name and Unit:
Comanche Peak Nuclear Plant, Unit No. 1 (Comanche Peak, Unit 1)
Docket No.:
50-445 APPLICATION INFORMATION Submittal Date: December 11, 2024 Submittal Agencywide Documents Access and Management System (ADAMS)
Accession No.: ML24346A143 Additional Document: Summary of February 25, 2025, Public Observation Meeting, dated April 3, 2025 (ML25083A059)
Applicable Inservice Testing (IST) Program Interval and Interval Start/End Dates:
Comanche Peak, Units 1 and 2, fourth IST interval program began on May 22, 2024, and ends on August 2, 2033. On July 27, 2023 (ML23198A321), the NRC authorized Alternative Request RV-1 submitted by the licensee in accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(2), Hardship without a compensating increase in quality and safety, for the performance of required tests or replacements for 19 thermal relief valves (including relief valves 1SW-0442 and 1SW-0443) to be extended from the fall 2023 refueling outage (RFO) to the spring 2025 RFO at Comanche Peak, Unit 1, and to be extended from the spring 2023 RFO to the fall 2024 RFO at Comanche Peak, Unit 2. In Alternative Request RV-1A, the licensee proposed a second extension of the IST requirements for thermal relief valves 1SW-0442 and 1SW-0443 until the fall 2026 RFO (1RF25) at Comanche Peak, Unit 1.
Alternative Provision: The licensee submitted Alternative Request RV-1A for Comanche Peak, Unit 1, under 10 CFR 50.55a(z)(2), on the basis that compliance with the 2017 Edition of American Society of Mechanical Engineers (ASME) Operation and Maintenance of Nuclear Power Plants, Division 1 (OM Code): Section IST, as incorporated by reference in 10 CFR 50.55a, Codes and standards, for tests or replacements of specific thermal relief valves at its upcoming 10-year interval would result in hardship or unusual difficulty without a compensating increase in the level of quality or safety.
Proposed Duration of Alternative: The licensee requested that this alternative be authorized until the fall 2026 RFO at Comanche Peak, Unit 1.
Applicable Code Edition and Addenda: The current Code of record for the fourth IST interval program at Comanche Peak is the 2017 Edition of the ASME OM Code, as incorporated by reference in 10 CFR 50.55a, Codes and standards.
Applicable Components and System
Description:
The two thermal relief valves (RLF VAV) within the scope of this alternative request are located in the station service water (SSW) system at Comanche Peak, Unit 1. These thermal relief valves provide overpressure protection for the SSW side of the component cooling water (CCW) heat exchangers (HX).
The thermal relief valves within the scope of this alternative request are as follows:
1SW-0442, CCW HX 1-01 SSW RLF VAV 1SW-0443, CCW HX 1-02 SSW RLF VAV Applicable IST Requirements: ASME OM Code, Mandatory Appendix I, Inservice Testing of Pressure Relief Devices in Water-Cooled Reactor Nuclear Power Plants, paragraph I-1390, Test Frequency, Classes 2 and 3 Pressure Relief Devices That Are Used for Thermal Relief Application, states:
Tests shall be performed on all Classes 2 and 3 relief devices used in thermal relief application every 10 [years], unless performance data indicate more frequent testing is necessary. In lieu of tests the Owner may replace the relief devices at a frequency of every 10 [years], unless performance data indicate more frequent replacements are necessary.
Brief Description of Proposed Alternative: The licensee provided the following brief description of the proposed alternative:
Since suitable replacement parts or valves to support rework or replacement cannot be procured by 1RF24 [Unit 1 RFO 24], Vistra OpCo proposes to rework/replace the two relief valves [1SW-0442 and 1SW-0443] no later than 1RF25 (in the Fall of 2026). Until valve rework/replacement, Vistra OpCo proposes to place Shift Manager Caution Tags on the heat exchanger isolation valves and vent valves requiring the heat exchangers to be vented upon isolation and to remain vented until the heat exchanger is no longer isolated from the safe shutdown impoundment.
For additional information on the licensees request, please refer to the documents located at the ADAMS Accession numbers identified above.
NRC STAFF EVALUATION On July 27, 2023, the U.S. Nuclear Regulatory Commission (NRC) staff authorized Alternative Request RV-1 submitted by the licensee in accordance with 10 CFR 50.55a(z)(2) on the basis that the requirements of the ASME OM Code to perform specific IST requirements for 19 thermal relief valves [including 1SW-0442 and 1SW-0443] during the spring 2023 RFO at Comanche Peak, Unit 2, and during the fall 2023 RFO at Comanche Peak, Unit 1, would have resulted in a hardship or unusual difficulty without a compensating increase in the level of quality and safety. In response to Alternative Request RV-1, the NRC staff authorized the test or replacement of the 19 thermal relief valves to be deferred until the spring 2025 RFO for Unit 1 and the fall 2024 RFO for Unit 2 at Comanche Peak on the basis that the extension would not adversely impact the reasonable assurance that those valves will be operationally ready to perform their safety functions.
The NRC regulations in 10 CFR 50.55a(f), Preservice and inservice testing requirements, require licensees to implement IST programs for pumps, valves, and dynamic restraints that meet the requirements of the ASME OM Code as incorporated by reference in 10 CFR 50.55a.
Based on the applicable code edition, beginning on August 3, 2023, the licensee was required by 10 CFR 50.55a to implement the fourth IST interval program at Comanche Peak, Unit 1.
In Alternative Request RV-1A, the licensee requested in accordance with 10 CFR 50.55a(z)(2) a further extension of the interval for testing or replacement required by the ASME OM Code in Mandatory Appendix I, paragraph I-1390, for two Unit 1 thermal relief valves (1SW-0442 and 1SW-0443) in the SSW system at Comanche Peak, Unit 1. These thermal relief valves provide overpressure protection for the SSW side of the CCW heat exchangers.
In the alternative request, the licensee proposed that the alternative be authorized until the fall 2026 RFO for Unit 1 at Comanche Peak. At that time, the licensee will rework or replace the 1SW-0442 and 1SW-0443 thermal relief valves with suitable replacement valves or parts. The licensee requested that the duration of Alternative Request RV-1A be until the fall 2026 RFO at Comanche Peak, Unit 1.
In performing their closed safety function, the thermal relief valves within the scope of Alternative Request RV-1A remain closed to maintain the SSW system pressure boundary when the SSW system is in service at Comanche Peak, Unit 1. The open safety function of these thermal relief valves is only required for overpressure protection when the heat exchangers or coolers are isolated for maintenance, or in response to a condition requiring the heat exchanger or cooler to be taken out of service. Further, the licensee indicated that the full open relief rate for one of these 1-inch thermal relief valves would be insignificant compared to the available margin in the safe shutdown impoundment inventory of the SSW system, and less than half the capacity of the applicable sump pumps at Comanche Peak.
In Alternative Request RV-1A, the licensee described the controls that will be established to provide assurance that the applicable thermal relief valves will remain closed throughout the duration of the alternative request. The licensee stated that shift manager clearances in the form of caution tags will be attached to the applicable heat exchanger and cooler isolation valves and vent valves. The caution tags will require the heat exchangers to be vented upon isolation and to remain vented until the heat exchanger is no longer isolated from the safe shutdown impoundment. The caution tags will provide directions to open the respective vent valve upon isolation of its heat exchanger. Opening the vent valve will eliminate the potential for an overpressure condition due to thermal expansion that might lead to opening of the applicable thermal relief valve.
In its justification for the alternative request, the licensee stated that the thermal relief valves within the scope of the request have not been tested for several years because they were inadvertently omitted from the IST program at Comanche Peak. The licensee has determined that replacement valves or parts are not currently available. As a result, implementing the ASME OM Code requirement to test the thermal relief valves during the upcoming RFO has the potential to cause an extended unavailability of the SSW system at Comanche Peak. The licensee has initiated several actions to obtain either replacement valves or parts to support testing of the thermal relief valves during the spring 2025 RFO for Unit 1. For example, the licensee contacted the valve vendor to obtain estimates of the procurement time for replacement valves and parts.
In its review of Alternative Request RV-1A for Comanche Peak, Unit 1, the NRC staff evaluated (1) the licensees description of the specific inservice tests proposed to be deferred for the applicable 1SW-0442 and 1SW-0443 thermal relief valves; (2) the open and closed functions of these small thermal relief valves; (3) the overall successful leaktight history of the thermal relief valves; (4) the capability of plant systems to respond to a stuck-open thermal relief valve; (5) the current unavailability of replacement valves or parts for the thermal relief valves; (6) the extensive efforts by the licensee to obtain replacement valves or parts as soon as possible; and (7) the duration of Alternative Request RV-1A with the re-initiation of the required testing during the fall 2026 RFO for Comanche Peak, Unit 1.
Based on the information provided by the licensee in Alternative Request RV-1A, the NRC staff finds that a hardship exists without a compensating increase in the level of quality and safety, in accordance with 10 CFR 50.55a(z)(2), for the performance of the specified IST requirements for the 1SW-0442 and 1SW-0443 thermal relief valves within the scope of the request at Comanche Peak, Unit 1. The NRC staff also finds that the licensees proposed alternative to postpone the IST requirements of the applicable two thermal relief valves until the 1RF25 RFO in the fall of 2026 for Comanche Peak, Unit 1, will not adversely impact the reasonable assurance that these thermal relief valves will be operationally ready to perform their safety functions.
CONCLUSION Based on its review of Alternative Request RV-1A, the NRC staff has determined that complying with the specified IST requirements for 1SW-0442 and 1SW-0443 thermal relief valves at the upcoming 10-year interval at Comanche Peak, Unit 1, would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
The NRC staff finds that Alternative Request RV-1A provides reasonable assurance that the applicable two thermal relief valves are operationally ready to perform their safety functions during the duration of the alternative request.
The NRC staff concludes that the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(2). Therefore, the NRC staff authorizes the use of Alternative Request RV-1A to extend the interval for the specified IST requirements of the applicable 1SW-0442 and 1SW-0443 thermal relief valves until the fall 2026 RFO at Comanche Peak, Unit 1. The NRC staff does not authorize Alternative Request RV-1A beyond the fall 2026 RFO (1RF25) at Comanche Peak, Unit 1.
All other ASME OM Code requirements as incorporated by reference in 10 CFR 50.55a for which relief or an alternative was not specifically requested, and granted or authorized (as appropriate), in the subject request remain applicable.
Principal Contributors: Gurjendra Bedi, NRR/DEX Thomas Scarbrough, NRR/DEX Date: April 25, 2025 Tony Nakanishi, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation cc: Listserv TONY NAKANISHI Digitally signed by TONY NAKANISHI Date: 2025.04.25 11:24:43 -04'00'
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