ML23198A321

Authorization and Safety Evaluation for Proposed Alternative RV-1

ML23198A321
Person / Time
Site:	Comanche Peak
Issue date:	07/27/2023
From:	Jennifer Dixon-Herrity NRC/NRR/DORL/LPL4
To:	Peters K Vistra Operating Co. (VistraOpCo)
References
EPID L-2023-LLR-0019
Download: ML23198A321 (1)

Text

July 27, 2023

COMANCHE PEAK NUCLEAR POWER PLANT, UNIT NOS. 1 AND 2 - AUTHORIZATION AND SAFETY EVALUATION FOR PROPOSED ALTERNATIVE RV-1 (EPID-L-2023-LLR-0019)

LICENSEE INFORMATION

Recipients Name and Address: Mr. Ken J. Peters Senior 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 Power Plant, Unit Nos. 1 and 2 (Comanche Peak, Units 1 and 2)

Docket Nos. 50-445 and 50-446

APPLICATION INFORMATION

Submittal Date: April 13, 2023

Submittal Agencywide Documents Access and Management System (ADAMS) Accession No. ML23108A246

Applicable Inservice Testing (IST) Program Interval and Interval Start/End Dates:

Comanche Peak, Units 1 and 2, third 10-year IST program interval, began on August 3, 2013, and ends August 2, 2023. On November 4, 2020 (ML20281A472), the NRC approved a request by the licensee in accordance with 10 CFR 50.55a(f)(4)(iv), Applicable IST Code: Use of later Code editions and addenda, to use a portion of the 2017 Edition of the ASME OM Code related to the documentation of IST results for the remainder of the third 10-year IST program interval at Comanche Peak. Comanche Peak, Units 1 and 2, fourth 10-year IST program interval will begin on August 3, 2023, and is scheduled to end on August 2, 2033.

Alternative Provision: The applicant submitted Alternative Request RV-1 for Comanche Peak, Units 1 and 2, under Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(2), on the basis that compliance with the American Society of Mechanical Engineers Code for Operation and Maintenance of Nuclear Power Plants (ASME OM Code) as incorporated by reference in 10 CFR 50.55a 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 for the remainder of the third 10-year IST program interval, and until the spring 2025 refueling outage (RFO) for Unit 1 and the fall 2024 RFO for Unit 2 during the fourth 10-year IST program interval at Comanche Peak.

Applicable Code Edition and Addenda: The current Code of record for the third 10-year IST program interval at Comanche Peak until August 2, 2023, is the 2004 Edition through the 2006 Addenda of the ASME OM Code as incorporated by reference in 10 CFR 50.55a, Codes and standards. Beginning on August 3, 2023, the licensee will be required by 10 CFR 50.55a to implement the fourth 10-year IST program interval at Comanche Peak with the Code of record as the 2017 Edition of the ASME OM Code, Division 1, section IST, as incorporated by reference in 10 CFR 50.55a

Applicable Components and or System

Description:

The 19 thermal relief valves in the station service water (SSW) system at Comanche Peak that provide overpressure protection for the SSW side of the component cooling water heat exchangers and the SSW side of various emergency core cooling system (ECCS) pump lube oil coolers listed below are within the scope of this alternative request:

1SW-0442 1SW-0446 1SW-0452 2SW-0434 2SW-0439 1SW-0443 1SW-0447 1SW-0453 2SW-0435 2SW-0440 1SW-0444 1SW-0450 2SW-0422 2SW-0436 2SW-0441 1SW-0445 1SW-0451 2SW-0423 2SW-0438

The licensee provides specific details regarding these thermal relief valves in table 1, RV-1 Relief Valve Descriptions, of Alternative Request RV-1.

Applicable IST Requirements: ASME OM Code, Mandatory Appendix I, Inservice Testing of Pressure Relief Devices in Light-Water 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.

In the 2017 Edition of the ASME OM Code, the title of Mandatory Appendix I is Inservice Testing of Pressure Relief Devices in Water-Cooled Reactor Nuclear Power Plants.

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 2RF20 [Unit 2 RFO 20][in the spring of 2023] or 1RF23

[Unit 1 RFO 23][in the fall of 2023], Vistra OpCo proposes to replace the Unit 2 and Unit 1 relief valves no later than 2RF21 (in the Fall of 2024) and 1RF24 (in the Spring of 2025), respectively. In the interim, Vistra OpCo proposes to control the service water system in a manner that eliminates the chances of overpressure due to thermal transients by requiring the applicable vent valve to

be opened upon isolation of the heat exchanger or cooler and remain open until the heat exchanger or cooler is no longer isolated from the safe shutdown impoundment.

For additional details on the licensees request, please refer to the documents located at the ADAMS Accession number identified above.

STAFF EVALUATION

On April 20, 2023, the U.S. Nuclear Regulatory Commission (NRC) staff verbally 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 tests for 19 thermal relief valves during the spring 2023 RFO at Comanche Peak, Unit 2, and during the fall 2023 RFO at Comanche Peak, Unit 1, would result in a hardship or unusual difficulty without a compensating increase in the level of quality and safety. The NRC verbal authorization is a publicly available document, which can be found in ADAMS at Accession No. ML23110A712.

The NRC regulations in 10 CFR 50.55a(f), Preservice and inservice testing requirements, require licensees to implement IST programs fo r 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 and addenda, beginning on August 3, 2023, the licensee will be required by 10 CFR 50.55a to implement the fourth 10-year IST program interval at Comanche Peak.

In accordance with 10 CFR 50.55a(z)(2), the licensee requested a postponement of testing required by the ASME OM Code in Mandator y Appendix I, paragraph I-1390, for 19 small thermal relief valves in the SSW system during the spring 2023 RFO at Comanche Peak Unit 2 and the fall 2023 RFO at Comanche Peak Unit 1. The 19 thermal relief valves include 10 thermal relief valves in Comanche Peak Unit 1, and 9 thermal relief valves in Comanche Peak Unit 2. These thermal relief valves provide overpressure protection for the SSW side of the component cooling water heat exchangers and the SSW side of various ECCS pump lube oil coolers. In its submittal, the licensee included the information that will be provided in the IST Program Plan for the 19 thermal relief valves within the scope of the request.

In Alternative Request RV-1, the licensee proposed that the alternative be authorized until the spring 2025 RFO for Unit 1 and the fall 2024 RFO for Unit 2 at Comanche Peak. At that time for each Comanche Peak unit, the 19 thermal relief valves will be reworked or replaced with suitable replacement valves or parts. The licensee noted that the duration of Alternative Request RV-1 spans the remainder of the third 10-year IST program interval and up to the first RFO of the fourth 10-year IST program interval at each Comanche Peak unit. With respect to paragraph I-1390 in Mandatory Appendix I of the ASME OM Code, there are no technical differences between the ASME OM Code editions used for the third and fourth 10-year IST program intervals at Comanche Peak.

In performing their closed safety function, the thermal relief valves within the scope of Alternative Request RV-1 remain closed to maintain the SSW system pressure boundary when the SSW system is in service at Comanche Peak. 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. The licensee stated that there has been only one instance of leakage from the relief valves within the scope of Alternative Request RV-1 at Comanche Peak.

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-1, 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 RFOs has the potential to cause an extended unavailability of the SSW system or ECCS 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 and the fall 2024 RFO for Unit 2. For example, the licensee has contacted the applicable valve vendor to obtain estimates of the procurement time for replacement valves and parts. The licensee has also been searching industry databases for currently available valves or parts from other sources.

In its review of Alternative Request RV-1 for Comanche Peak, the NRC staff evaluated (1) the licensees description of the specific inservice tests proposed to be deferred for the applicable 19 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 re-initiation of the required testing during the spring 2025 RFO for Unit 1 and the fall 2024 RFO for Unit 2 at Comanche Peak. The NRC staff evaluated the duration of Alternative Request RV-1, which spans the remainder of the third 10-year IST program interval and extends until the first RFO of the fourth 10-year IST program interval for each Comanche Peak unit.

Based on the information provided by the licensee in Alternative Request RV-1, 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 inservice tests for the 19 thermal relief valves within the scope of the request during the spring 2023 RFO at Comanche Peak Unit 2, and during the fall 2023 RFO at Comanche Peak Unit 1. The NRC staff also finds that the licensees proposed alternative to postpone the inservice tests of the applicable 19 thermal relief valves until the spring 2025 RFO for Unit 1 and the fall 2024 RFO for Unit 2 at Comanche Peak will not adversely impact the reasonable assurance that those valves will be operationally ready to perform their safety functions.

CONCLUSION

The NRC staff has determined that complying with the specified requirements described in the licensees request referenced above would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

The proposed alternative provides reasonable assurance that the applicable 19 thermal relief valves are operationally ready to perform their safety functions.

The NRC staff concludes that the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(2).

The NRC staff authorizes the use of Alternative R equest RV-1 to defer the specified inservice tests of the applicable 19 thermal relief valves for the remainder of the third 10-year IST program interval, and until the spring 2025 RFO for Unit 1 and the fall 2024 RFO for Unit 2 during the fourth 10-year IST program interval at Comanche Peak. The NRC staff does not authorize Alternative Request RV-1 beyond the spring 2025 RFO for Unit 1 or the fall 2024 RFO for Unit 2 at Comanche Peak.

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 Contributor: Thomas Scarbrough

Date: July 27, 2023

Jennifer Dixon-Herrity, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

cc: Listserv

ML23198A321 *via email NRR-028 OFFICE NRR/DORL/LPL4/PM NRR/DORL/LPL4/LA* NRR/DEX/EMIB/BC*

NAME DGalvin PBlechman SBailey DATE 7/18/2023 7/18/2023 5/25/2023 OFFICE NRR/DORL/LPL4/BC*

NAME JDixon-Herrity DATE 7/27/2023