ML25010A381
| ML25010A381 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  (NPF-081) |
| Issue date: | 01/16/2025 |
| From: | Markley M NRC/NRR/DORL/LPL2-1 |
| To: | Coleman J Southern Nuclear Operating Co |
| Lamb J, NRR/DORL/LPL2-1 | |
| References | |
| EPID L-2025-LLR-0000 | |
| Download: ML25010A381 (1) | |
Text
January 16, 2025 Jamie M. Coleman Regulatory Affairs Director Southern Nuclear Operating Company 3535 Colonnade Parkway Birmingham, AL 35243
SUBJECT:
VOGTLE ELECTRIC GENERATING PLANT, UNIT 2 - RE: AUTHORIZATION OF PROPOSED ALTERNATIVE FOR INSERVICE TESTING OF THE 2A AND 2B CHARGING PUMPS (EPID L-2025-LLR-0000)
Dear Jamie Coleman:
By letter dated January 7, 2025 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML25007A244), Southern Nuclear Operating Company (SNC, the licensee) submitted Alternative Request RR-PR-04 to the U.S. Nuclear Regulatory Commission (NRC) for Vogtle Electric Generating Plant (Vogtle), 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 with Addenda through OMb-2006 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, SNC requested to extend the test interval requirements to perform Group A quarterly pump tests as specified in ASME OM Code, Subsection ISTB, Inservice Testing of Pumps in Light-Water Reactor Nuclear Power Plants, paragraph ISTB-3400, Frequency of Inservice Tests, for the 2A and 2B charging pumps at Vogtle, Unit 2, until the end of the spring 2025 refueling outage when the reactor coolant pump #1 seals are expected to be repaired or a forced outage of sufficient duration and scope prior to the spring 2025 refueling outage to perform the repairs.
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 senior project manager, John G. Lamb, at 301-415-3100 or via email at John.Lamb@nrc.gov.
Sincerely, Michael Markley, Chief Plant Licensing Branch 2-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-425
Enclosure:
Safety Evaluation cc: Listserv MICHAEL MARKLEY Digitally signed by MICHAEL MARKLEY Date: 2025.01.16 10:14:21 -05'00'
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ALTERNATIVE REQUEST RR-PR-04 FOR 2A AND 2B CHARGING PUMPS FOURTH INSERVICE TESTING PROGRAM INTERVAL SOUTHERN NUCLEAR OPERATING COMPANY VOGTLE ELECTRIC GENERATING PLANT, UNIT 2 DOCKET NUMBER 50-425 EPID L-2025-LLR-0000
1.0 INTRODUCTION
By letter dated January 7, 2025 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML25007A244), 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 with Addenda through OMb-2006 of the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code) for 2A and 2B charging pumps at Vogtle Electric Generating Plant (Vogtle), 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 to extend the test interval requirements to perform Group A quarterly pump tests as specified in ASME OM Code, Subsection ISTB, paragraph ISTB-3400, for the 2A and 2B charging pumps until the end of the spring 2025 refueling outage for Vogtle, Unit 2. SNC stated that the performance of 2A and 2B charging pumps tests as scheduled would constitute a hardship without a compensating increase in the level of quality and safety.
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 SNCs Alternative Request RR-PR-04 Applicable ASME OM Code Edition The applicable Code of Record for the Fourth IST Program interval at Vogtle, Unit 2, is the 2004 Edition with Addenda through OMb-2006 of ASME OM Code as incorporated by reference in 10 CFR 50.55a. The Fourth IST Program interval at Vogtle, Unit 2, began on May 31, 2017, and is currently scheduled to end on May 30, 2027.
Applicable ASME OM Code Components Table 1 lists the pumps at Vogtle, Unit 2, for which this alternative is being requested.
Table 1 Component Description Code Class OM Group or Category 21208P6002 2A Charging Pump*
2 Group A Pump 21208P6003 2B Charging Pump**
2 Group A Pump
- Also referred to as chemical and volume control system (CVCS) centrifugal charging pump (CCP) A Pump
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.
ASME OM Code, Subsection ISTB, 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.
SNCs Proposed Alternative and Basis for Use:
In Section 5 of Alternative Request RR-PR-04, SNC stated:
The proposed alternative requests to defer the requirements to perform Group A quarterly pump tests as required by ISTB-3400, for the 2A and 2B [centrifugal] charging pumps until the end of the spring 2025 refueling outage. This will allow performance of a comprehensive pump test (CPT) for the 2A and 2B centrifugal charging pumps during the upcoming spring of 2025 refueling outage. The Group A quarterly pump tests will resume as scheduled following the spring of 2025 refueling outage and repair of the #1 [reactor coolant pump]
RCP seals.
Previous trends for the 2A and 2B charging pumps are in Attachment 1 (Tables 1 - 8) and show the operational readiness of the pumps 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 and 2B Centrifugal 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 ASME OM code and design limits. Therefore, it is unlikely that the upcoming quarterly pump tests would produce a failing value for any test parameter.
Additionally, no significant maintenance has been performed or is planned for the 2A and 2B centrifugal charging pumps that would alter the pump test parameters.
Repairs to the #1 seals are planned for the upcoming spring of 2025 refueling outage because repair of the seals 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 and 2B centrifugal charging pumps would constitute a hardship without a compensating increase in the level of quality and safety. The proposed alternative to ISTB-3400, Frequency of lnservice Tests, provides reasonable assurance of pump 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 test requirements cannot be achieved without considerable plant safety and reliability risks prior to significant repairs to address the #1 RCP seal degradation. Performance of the Group A quarterly charging pump test could cause perturbations to the #1 seals that could challenge the ability of the RCP seal package to prevent loss of coolant which challenges plant safety and reliability.
SNCs Reason for Request In Section 4 of Alternative Request RR-PR-04, SNC stated:
Pursuant to 10 CFR 50.55a, Codes and standards, paragraph (z)(2), an alternative is proposed to the quarterly pump 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. A rising trend in Unit 2 RCP #1 Seal Leak-off on all RCPs was identified on December 26, 2024. The increased leakage is due to degradation of the #1 seals causing increased seal leak-off. While the source of the #1 seal degradation cannot be formally concluded before inspection during reactor shutdown, the most probable cause is believed to be increased iron oxide deposition on the faceplates.
Based on this condition, any centrifugal charging pump test could cause perturbations to the
- 1 seals based on the required changes to seal injection flow, charging flow, Volume Control Tank [VCT] pressure, and pressure changes to the #1 seal return flow path during the test. Damage or degradation of the #1 seals could cause loss of coolant through the seal package which challenges plant safety and reliability.
Damage or degradation of the #1 seals (due to perturbations caused by the Group A pump test) could cause seal leak-off flow rates to exceed procedural operating limits and require a shutdown of Unit 2 in order to prevent the potential small break loss of coolant accident. The system operating procedure provides direction for monitoring operational parameters and taking appropriate action. Procedures direct the operators to manually trip the reactor then secure the affected RCP if the total seal leak off exceeds the operational limit defined in procedures (currently 6 gpm [gallons per minute]).
Repairs to address the RCP #1 seal leakages 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 RCP seals 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 2A centrifugal charging pump is due January 30, 2025, which is 92 days plus grace from the last test performed on October 7, 2024, and the next performance of the Group A test for the 2B centrifugal charging pump is due February 20, 2025, which is 92 days plus grace from the last test performed on October 28, 2024. Southern Nuclear Operating Company is requesting NRC approval of this relief request by January 29, 2025, prior to the expiration of the testing frequency window.
3.2
NRC Staff Evaluation
In its Alternative Request RR-PR-04 dated January 7, 2025, SNC proposed an extension of the IST Program testing schedule for the 2A and 2B charging pumps at Vogtle, Unit 2. In this request, the licensee described how testing these pumps at this time could cause stress to the RCP #1 seals. As a result, SNC 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 Vogtle, Unit 2, requires the subject pumps be tested every 3 months. The licensee reported that the next test was due on January 30, 2025, for the 2A charging pump, and February 20, 2025, for the 2B charging pump.
In its request, SNC proposed to extend the IST testing schedule for these pumps, until the spring of 2025 refueling outage when the RCP #1 seals are expected to be repaired, or a forced outage of sufficient duration and scope prior to the spring 2025 refueling outage to make the repairs.
In its submittal dated January 7, 2025, SNC reported that a rising trend in Vogtle, Unit 2, RCP #1 seal leak-off on all RCPs was identified on December 26, 2024. The increased leakage is due to degradation of the RCP #1 seals causing increased seal leak-off. Based on this condition, the licensee is concerned that any centrifugal charging pump test could cause perturbations to the RCP #1 seals based on the required changes to seal injection flow, charging flow, VCT pressure, and pressure changes to the #1 seal return flow path during the test. Damage or degradation of the RCP #1 seals due to perturbations caused by the Group A pump test could cause seal leak-off flow rates to exceed procedural operating limits and require a shutdown of Vogtle, Unit 2, in order to prevent a potential small break loss of coolant accident.
Repairs to address the RCP #1 seal leakage are scheduled for the upcoming Vogtle, Unit 2, refueling outage in the spring of 2025. As a contingency, SNC has included the repair scope on the forced outage worklist if a forced outage of sufficient duration and scope occurs prior to the planned refueling outage. Repair of the RCP seals requires the pump and motor to be decoupled that would require shutdown of Vogtle, Unit 2. Based on this information, the NRC staff agrees that testing of the 2A and 2B charging pumps before repair of the RCP #1 seals would cause stress to the seals and result in further seal degradation and challenge plant safety.
In its submittal dated January 7, 2025, SNC summarized the history of the test results for the 2A and 2B charging pumps at Vogtle, Unit 2. In particular, the quarterly Group A pump tests over the last 2 years and biennial CPT testing over the last 10 years indicate successful pump performance. In particular, the recorded values for pump vibration, flow, and differential pressure remain within the ASME OM Code and design limits. SNC reports that no significant maintenance has been performed or is planned for the 2A and 2B centrifugal charging pumps at this time. The NRC staff identified variations among the measured pump performance parameters provided in the pump data tables in the licensee submittal. However, the data tables note that all trends are within the acceptance criteria and specified that any adverse trend or notable deviation would require SNC engineering evaluation. The NRC staff did not identify any significant deficiencies or adverse trends in the licensee data tables that might reflect degraded performance of the subject pumps during the duration of the alternative request.
Based on its independent review of the test and performance history of the pumps 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 and 2B charging pumps at Vogtle, Unit 2, to be capable of performing their design functions during the proposed IST test interval extension.
The NRC staff found that compliance with the specified IST requirements for the subject pumps 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 NRC 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 and 2B charging pumps at Vogtle, Unit 2, until the spring of 2025 refueling outage when the RCP #1 seals will be repaired. SNC will be responsible for evaluating the 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 January 7, 2025, provides adequate justification that compliance with the applicable ASME OM Code test requirements for the subject 2A and 2B charging pumps at Vogtle, Unit 2, at this time would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety until the RCP #1 seals are repaired. The NRC staff also found that the testing and performance experience of the subject pumps 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 for the proposed extension of the IST testing interval for the 2A and 2B charging pumps at Vogtle, Unit 2, until the spring of 2025 refueling outage, when the RCP #1 seals will be repaired, or an outage of sufficient duration prior to the spring 2025 refueling outage to make the repairs.
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, NRR/DEX/EMIB Date: January 16, 2025
ML25010A381 NRR-028 OFFICE NRR/DORL/LPL2-1/PM NRR/DORL/LPL2-1/LA NRR/DEX/EMIB/BC NRR/DORL/LPL2-1/BC NAME JLamb KZeleznock SBailey (KHsu for)
MMarkley DATE 01/08/2025 01/13/2025 01/14/2025 01/16/2025