ML24351A040
| ML24351A040 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 12/19/2024 |
| From: | Markley M Plant Licensing Branch II |
| To: | Coleman J Southern Nuclear Operating Co |
| Turner, Zachary | |
| References | |
| EPID l-2024-LLR-0068 | |
| Download: ML24351A040 (11) | |
Text
December 19, 2024 Jamie M. Coleman Regulatory Affairs Director Southern Nuclear Operating Company 3535 Colonnade Parkway Birmingham, AL 35243
SUBJECT:
JOSEPH M. FARLEY NUCLEAR PLANT, UNIT NO. 2 - RE: AUTHORIZATION OF PROPOSED ALTERNATIVE RR-PR-04 INSERVICE TESTING OF THE 2A, 2B, AND 2C CHARGING PUMPS AND MINI-FLOW ISOLATION VALVES (EPID L-2024-LLR-0068)
Dear Jamie Coleman:
By letter dated October 18, 2024, as supplemented by letter dated October 25, 2024, Southern Nuclear Operating Company (the licensee) submitted Alternative Request RR-PR-04 to the U.S. Nuclear Regulatory Commission (NRC), for Joseph M. Farley Nuclear Plant (Farley),
Unit 2. Pursuant to Title 10 of the Code of Federal Regulations (10 CFR), Section 50.55a, Codes and standards, paragraph (z)(2), the licensee requested an alternative to specific inservice testing (IST) requirements in the 2004 Edition through 2006 Addenda of the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code), as incorporated by reference in 10 CFR 50.55a, on the basis that compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Specifically, the licensee requested an extension of the IST testing interval for the 2A, 2B, and 2C charging pumps and mini-flow isolation valves, until after the spring of 2025 refueling outage, or a forced outage of sufficient duration, when the 2B reactor coolant pump seal is expected to be repaired.
On November 6, 2024, the NRC staff verbally authorized the use of alternative RR-PR-04 for Farley, Unit 2. This letter provides the NRCs written safety evaluation for the alternative request.
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.
J. Coleman If you have any questions, please contact the project manager, Zach Turner, at 301-415-2258 or via email at Zachary.Turner@nrc.gov.
Sincerely, Michael Markley, Chief Plant Licensing Branch 2-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-364
Enclosure:
Safety Evaluation cc: Listserv MICHAEL MARKLEY Digitally signed by MICHAEL MARKLEY Date: 2024.12.19 14:23:45 -05'00'
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ALTERNATIVE REQUEST RR-PR-04 FOR INSERVICE TESTING INTERVAL EXTENSION FOR 2A, 2B, AND 2C CHARGING PUMPS AND MINI-FLOW ISOLATION VALVES FIFTH INSERVICE TESTING PROGRAM INTERVAL SOUTHERN NUCLEAR OPERATING COMPANY JOSEPH M. FARLEY NUCLEAR PLANT, UNIT 2 DOCKET NUMBER 50-364 EPID: L-2024-LLR-0068
1.0 INTRODUCTION
By letter dated October 18, 2024 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML24292A210), as supplemented by letter dated October 25, 2024 (ML24299A270), Southern Nuclear Operating Company (SNC, the licensee) submitted Alternative Request RR-PR-04 to the U.S. Nuclear Regulatory Commission (NRC) proposing an alternative to specific inservice testing (IST) requirements in the 2004 Edition through 2006 Addenda of the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code) for 2A, 2B, and 2C charging pumps and mini-flow isolation valves at Joseph M. Farley Nuclear Plant (Farley), Unit 2.
Specifically, pursuant to subparagraph (2) in paragraph (z), Alternatives to codes and standards requirements, of Section 55a, Codes and standards, in Part 50, Domestic Licensing of Production and Utilization Facilities, to Title 10 of the Code of Federal Regulations (10 CFR), the licensee requested a one-time extension of the IST testing interval for the 2A, 2B, and 2C charging pumps and 2A, 2B, and 2C mini-flow isolation valves, on the basis that compliance with certain ASME OM Code requirements, at that time, would present an undue hardship without a compensating increase in the level of quality and safety.
On November 6, 2024, the NRC staff communicated a verbal authorization (ML24312A190) of Alternative Request RR-PR-04 for the proposed extension of the IST Program 3-month schedule for testing the 2A, 2B, and 2C charging pumps and 2A, 2B, and 2C charging pump mini-flow isolation valves at Farley, Unit 2, in accordance with 10 CFR 50.55a(z)(2). The NRC staff authorized a delay in the testing until after the spring of 2025 refueling outage, or a forced outage of sufficient duration, when the 2B reactor coolant pump (RCP) seal is expected to be repaired. The verbal authorization documentation provided a summary of the staff evaluation of the proposed alternative. This safety evaluation documents the staffs review of the licensees Alternative Request RR-PR-04.
2.0 REGULATORY EVALUATION
The NRC regulations in 10 CFR 50.55a(f)(4), Inservice testing standards requirement for operating plants, state, in part, that throughout the service life of a boiling or pressurized water-cooled nuclear power facility, pumps and valves that are within the scope of the ASME OM Code must meet the IST requirements (except design and access provisions) set forth in the ASME OM Code and addenda that become effective subsequent to editions and addenda specified in 10 CFR 50.55a(f)(2) and (3) and that are incorporated by reference in 10 CFR 50.55a(a)(1)(iv), to the extent practical within the limitations of design, geometry, and materials of construction of the components.
The NRC regulations in 10 CFR 50.55a(z), Alternatives to codes and standards requirements, state that alternatives to the requirements of 10 CFR 50.55a(b) through (h) or portions thereof may be used when authorized by the Director, Office of Nuclear Reactor Regulation. A proposed alternative must be submitted and authorized prior to implementation.
The applicant or licensee must demonstrate that:
(1) Acceptable level of quality and safety. The proposed alternative would provide an acceptable level of quality and safety; or (2) Hardship without a compensating increase in quality and safety. Compliance with the specified requirements of this section would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
3.0 TECHNICAL EVALUATION
3.1 Licensees Alternative Request Applicable ASME OM Code Edition The applicable Code of Record for the Fifth IST Program interval at Farley, Unit 2, is the 2004 Edition through 2006 Addenda of ASME OM Code as incorporated by reference in 10 CFR 50.55a. The Fifth IST Program interval at Farley, Unit 2, began on December 1, 2017, and is currently scheduled to end on November 30, 2027.
Applicable ASME OM Code Components Table 1 lists the pumps and motor-operated valves (MOVs) at Farley, Unit 2, for which this alternative is being requested.
Table 1 Component Description Code Class OM Group or Category Q2E21P002A 2A Charging Pump 2
Group A Pump Q2E21P002B 2B Charging Pump 2
Group A Pump Q2E21P002C 2C Charging Pump 2
Group A Pump Q2E21MOV8109A 2A Charging Pump Mini-Flow Isolation Valve 2
Category B Valve Q2E21MOV8109B 2B Charging Pump Mini-Flow Isolation Valve 2
Category B Valve Q2E21MOV8109C 2C Charging Pump Mini-Flow Isolation Valve 2
Category B Valve Applicable ASME OM Code Requirements The IST requirements in the ASME OM Code, as incorporated by reference in 10 CFR 50.55a, related to this alternative request are as follows:
ASME OM Code, Subsection ISTC, Inservice Testing of Valves in Light-Water Reactor Nuclear Power Plants, paragraph ISTC-3510, Exercising Test Frequency, states, in part, that Active Category A, Category B, and Category C check valves shall be exercised nominally every 3 months, except as provided by paragraphs ISTC-3520, ISTC-3540, ISTC-3550, ISTC-3570, ISTC-5221, and ISTC-5222.
ASME OM Code, Subsection ISTB, Inservice Testing of Pumps in Light-Water Reactor Nuclear Power Plants, paragraph ISTB-3400, Frequency of Inservice Tests, states that an inservice test shall be run on each pump as specified in Table ISTB-3400-1. Table ISTB-3400-1, Inservice Test Frequency, specifies that for Group A pumps, a Comprehensive [Pump] Test (CPT) be performed biennially, and a Group A Test be performed quarterly.
Licensees Proposed Alternative and Basis for Use:
In Section 5 of the Enclosure to its submittal dated October 18, 2024, the licensee stated:
The proposed alternative requests to defer the requirements to perform Group A quarterly pump tests as required by ISTB-3400 for the 2A, 2B, and 2C charging pumps and quarterly exercise testing for the 2A, 2B, and 2C charging pump mini flow isolation valves as required by ISTC-3510 until April 14, 2025. This will allow performance of a comprehensive pump test (CPT) for the 2A, 2B, and 2C charging pumps and the performance of a Category B valve test for the 2A, 2B, and 2C charging pump mini flow isolation valves during the upcoming spring of 2025 refueling outage. The Group A quarterly pump tests and quarterly Category B valve tests will resume as scheduled following the spring of 2025 refueling outage and repair of the 2B RCP seal.
Previous trends for the 2A, 2B, and 2C charging pumps and the charging pump mini flow isolation valves are in Attachment 1 (Tables 1-15) and show the operational readiness of the pumps and valves to perform their intended safety function. The last two years of data from the quarterly Group A testing and the last 10 years of data from the CPT for the 2A, 2B, and 2C Charging Pumps indicate there is no current pump degradation. All recorded values for pump vibration, flow, and differential pressure during the review period were within the ASME OM Code and design limits. The last two years of recorded stroke times for the charging pump mini flow isolation valves have been within ASME OM Code and design limits. Therefore, it is unlikely that the upcoming quarterly pump and valve tests would produce a failing value for any test parameter. Additionally, no significant maintenance has been performed or is planned for the 2A, 2B, or 2C charging pumps or charging pump mini flow valves that would alter the pump and valve test parameters.
Repairs to the 2B RCP seal are planned for the upcoming spring of 2025 refueling outage because repair of the seal requires the pump and motor to be decoupled which would require shutdown of the Unit 2 reactor. In the current conditions, performing the Group A quarterly test for the 2A, 2B, and 2C charging pumps and the Category B valve test for the 2A, 2B, and 2C charging pump mini flow isolation valves would constitute a hardship without a compensating increase in the level of quality and safety. The proposed alternative to ISTB-3400, Frequency of Inservice Tests, and ISTC-3510, Exercising Test Frequency, provides reasonable assurance of pump and valve operational readiness and provides an acceptable level of quality and safety.
Relief is requested pursuant to 10 CFR 50.55a(z)(2) based on the determination that compliance with the ASME OM Code required quarterly charging pump and valve test requirements cannot be achieved without considerable plant safety and reliability risks prior to significant repairs to address the 2B RCP seal degradation. Performance of the Group A quarterly charging pump test and Category B valve test has shown to cause perturbations to the #1 and #2 RCP seals that could challenge the ability of the RCP seal package to prevent loss of coolant which challenges plant safety and reliability.
Licensees Reason for Request In Section 4 of the Enclosure to its submittal dated October 18, 2024, the licensee stated:
Pursuant to 10 CFR 50.55a, Codes and standards, paragraph (z)(2), an alternative is proposed to the quarterly pump and valve test requirements of the ASME OM-2004 Code with Addenda through OMb-2006. The basis of the request is that compliance with the specified requirements results in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Increase inleakage into the Unit 2 Reactor Coolant Drain Tank (RCDT) was identified on September 4, 2024. The increased inleakage is due to degradation of the 2B Reactor Coolant Pump (RCP) #2 seal causing increased seal leakoff which drains into the RCDT.
On September 19, 2024, during performance of the quarterly Group A test for the 2A charging pump and Category B valve test for the 2A charging pump mini flow isolation valve, perturbations were experienced that caused a decrease in the 2B RCP #1 seal leakoff flow rate and an increase in the #2 seal leakoff flow rate. Performance of the Group A pump test causes perturbations to the #1 and #2 seals based on the required changes to seal injection flow, charging flow, Volume Control Tank (VCT) pressure, and pressure perturbations on the #1 seal return flow path during the test. The Category B valve tests are performed in conjunction with the pump test and require charging pump alignments to be swapped. The Category B valve tests cause pressure perturbations to the #1 RCP seal leak-off line and the potential to degrade the #1 RCP seal. The #1 seal does not have a fully functional backup in the event of failure due to the degradation of the #2 seal. Continued performance of the Group A pump tests and Category B valve tests causes undue stress to the #1 and #2 RCP seals and could cause further degradation.
The potential damage or degradation of the #1 seal, combined with the known degradation of the #2 seal, challenges plant safety and reliability due to the potential for a small break loss of coolant accident through the seal package. Damage or degradation of the #1 seal (due to the perturbations caused by the Group A pump test and Category B valve tests) could cause seal leakoff flow rates to exceed abnormal operating procedure limits and require a shutdown of Unit 2 in order to prevent the potential small break loss of coolant accident. The abnormal operating procedure directs preparing for an orderly shutdown within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> if the #1 seal leakoff is greater than 6 gpm [gallons per minute] and combined seal leakoff is less than 8 gpm. The procedures direct manually tripping the reactor then securing the affected RCP if combined #1 and #2 seal leakoff are greater than 8 gpm.
Repairs to address the 2B RCP seal leakage are scheduled for the upcoming refueling outage in the spring of 2025. As a contingency, the repair scope is included on the forced outage worklist and would be performed if a forced outage of sufficient duration and scope were necessary prior to the planned refueling outage. Repair of the 2B RCP seal requires the pump and motor to be decoupled which would require shutdown of the Unit 2 reactor and reduce plant reliability.
The next performance of the Group A test for the 2B charging pump and the Category B test for the charging pump mini flow isolation valves is due November 7, 2024, which is 92 days plus grace from the last test performance on July 15, 2024.
SNC requested approval of this alternative request by November 7, 2024, prior to the expiration of the test frequency window.
3.2
NRC Staff Evaluation
In Alternative Request RR-PR-04, submitted on October 18, 2024, and supplemented by letter dated October 25, 2024, the licensee proposed an extension of the IST Program testing schedule for the 2A, 2B, and 2C charging pumps and 2A, 2B, and 2C charging pump mini-flow isolation valves at Farley, Unit 2. In this request, the licensee described how testing these pumps and valves at this time could cause stress to the 2B RCP seals. As a result, the licensee submitted the proposed alternative under the hardship provisions of 10 CFR 50.55a(z)(2).
The licensees current OM Code of Record for the IST Program at Farley, Unit 2, requires the subject pumps and valves to be tested every three months. The licensee reported that the next test was due on November 7, 2024. In its request, the licensee proposed to extend the IST testing schedule for these pumps and valves, until after the spring of 2025 refueling outage, or a forced outage of sufficient duration, when the 2B RCP seal is expected to be repaired.
In its submittal dated October 18, 2024, the licensee reported that on September 19, 2024, during performance of the quarterly Group A pump test for the 2A charging pump and Category B valve test for the 2A charging pump mini-flow isolation valve, perturbations were experienced that caused a decrease in the 2B RCP #1 seal leakoff flow rate and an increase in the #2 seal leakoff flow rate. The licensee stated that performance of the Group A pump test causes perturbations to the 2B RCP #1 and #2 seals based on the required changes to seal injection flow, charging flow, VCT pressure, and pressure perturbations on the #1 seal return flow path during the test. The licensee also indicated that the Category B valve tests cause pressure perturbations to the 2B RCP #1 seal leakoff line and the potential to degrade the 2B RCP #1 seal. The licensee reported that damage or degradation of the 2B RCP #1 seal from the Group A pump test and Category B valve tests could cause seal leakoff flow rates to exceed abnormal operating procedure limits and require a shutdown of Farley, Unit 2, to prevent a potential small break loss of coolant accident. Based on this information, the NRC staff agrees that testing these components before repair of the 2B RCP seal would cause stress to the 2B RCP seals and result in further seal degradation and challenge plant safety.
In its submittal dated October 18, 2024, the licensee summarized the history of the test results for the subject pumps and valves. In particular, the quarterly Group A pump tests over the last two years and the biennial CPTs over the last 10 years for the 2A, 2B, and 2C charging pumps have been satisfactory. Further, the last two years of recorded stroke times for the charging pump mini-flow isolation valves have been within the ASME OM Code and design limits. The licensee had not identified any deficiencies or adverse trends that might have reflected degraded performance of the subject pumps and valves.
In its submittal dated October 25, 2024, in response to an NRC staff request for additional information (RAI), the licensee discussed its evaluation of increased vibration test data for the 2B charging pump indicated in its October 18, 2024, submittal. The licensee noted that an increase in the recorded values for the 2B charging pump outboard vibration values was observed during the most recent CPT on October 20, 2023, compared to previous test data.
The licensee reported that adequate margin is available between the recorded values and the alert range for the vibration values for the 2B charging pump. The licensee provided graphs that show the recorded values compared to the reference value and alert range during the CPT for this pump. The licensee demonstrated that there were no significant changes or trends for the quarterly Group A pump test of the 2B charging pump before or after the October 2023 CPT.
Beyond the MOV stroke-time test information, the NRC staff requested in an RAI that the licensee describe the successful performance of the charging pump mini-flow isolation valves at Farley, Unit 2, during recent diagnostic testing, such as obtained by the MOV testing program under Generic Letter (GL) 96-05, Periodic Verification of Design-Basis Capability of Safety-Related Motor-Operated Valves, to comply with 10 CFR 50.55a(b)(3)(ii). In its October 25, 2024, submittal, the licensee stated that these MOVs are within the scope of the Farley GL 96-05 testing program. The most recent diagnostic tests for these MOVs were performed during the Unit 2 refueling outage in the fall of 2017. The licensee has categorized these MOVs as high margin/low risk valves with a 10-year diagnostic testing interval per its GL 96-05 program. The licensee reported that the 2017 testing demonstrated 59.8 percent design margin for both Q2E21MOV8109A and Q2E21MOV8109B, and 66 percent design margin for Q2E21MOV8109C. The licensee stated that Q2E21MOV8109B and Q2E21MOV8109C are scheduled to be diagnostically tested under the GL 96-05 program during the spring of 2025 refueling outage at Farley, Unit 2, while Q2E21MOV8109A will be tested during the fall 2026 refueling outage at Farley, Unit 2. The NRC staff finds that this diagnostic test information supports the licensees proposal in Alternative Request RR-PR-04 to extend the ASME OM Code exercise test interval for the charging pump mini-flow isolation valves at Farley, Unit 2.
Based on its independent review of the test and performance history of the pumps and valves within the scope of Alternative Request RR-PR-04, the NRC staff determined that there is reasonable assurance of the operational readiness of the 2A, 2B, and 2C charging pumps and the 2A, 2B, and 2C mini-flow isolation valves at Farley, Unit 2, to be capable of performing their design functions during the proposed IST test interval extension. The staff found that compliance with the specified IST requirements for the subject pumps and valves during the short duration of the requested alternative would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Therefore, the staff determined that the proposed alternative meets the requirements of 10 CFR 50.55a(z)(2). As a result, the NRC staff finds that Alternative Request RR-PR-04 may be authorized for an extension of the specified testing intervals for the 2A, 2B, and 2C charging pumps and 2A, 2B, and 2C charging pump mini-flow isolation valves at Farley, Unit 2, until after the spring of 2025 refueling outage, or a forced outage of sufficient duration, when the 2B RCP seal will be repaired. The licensee will be responsible for evaluating the 2B RCP seals and conducting an extent of condition review under 10 CFR Part 50, Appendix B, Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants, based on that evaluation.
4.0 CONCLUSION
As set forth above, the NRC staff determined that Alternative Request RR-PR-04 as described in the licensees submittal dated October 18, 2024, as supplemented by letter dated October 25, 2024, provides adequate justification that compliance with the applicable ASME OM Code test requirements for the subject 2A, 2B, and 2C charging pumps and 2A, 2B, and 2C mini-flow isolation valves at Farley, Unit 2, would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety until such time as the 2B RCP seal is repaired. The NRC staff also found that the testing and performance experience of the subject pumps and valves provides reasonable assurance that they will be operationally ready to perform their safety functions for the duration of the request. Accordingly, the NRC staff concludes that the licensee has adequately addressed all regulatory requirements set forth in 10 CFR 50.55a(z)(2). Therefore, the NRC staff authorizes Alternative Request RR-PR-04 (as supplemented) for the proposed extension of the IST testing interval for the 2A, 2B, and 2C charging pumps and 2A, 2B, and 2C mini-flow isolation valves at Farley, Unit 2, until after the spring of 2025 refueling outage, or a forced outage of sufficient duration, when the 2B RCP seal is expected to be repaired.
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: T. Scarbrough, NRR S. Roche Rivera, NRR Date: December 19, 2024
ML24351A040 OFFICE NRR/DORL/LPL2-1/PMNRR/DORL/LPL2-1/LA NRR/DEX/EMIB/BC NRR/DORL/LPL2-1/BC NAME ZTurner KZeleznock SBailey MMarkley DATE 12/16/2024 12/17/2024 12/17/2024 12/19/2024