ML23248A209
| ML23248A209 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 09/18/2023 |
| From: | Jeffrey Whited Plant Licensing Branch III |
| To: | Hafen S Northern States Power Company, Minnesota |
| Ballard, B | |
| References | |
| EPID L-2023-LLR-0040 | |
| Download: ML23248A209 (1) | |
Text
September 18, 2023 Mr. Shawn Hafen Site Vice President Northern States Power Company - Minnesota Monticello Nuclear Generating Plant 2807 West County Road 75 Monticello, MN 55362
SUBJECT:
MONTICELLO NUCLEAR GENERATING PLANT - PROPOSED ALTERNATIVE VR-11 TO THE REQUIREMENTS OF THE ASME OM CODE ASSOCIATED WITH INSERVICE TESTING OF MO-2397, REACTOR WATER CLEANUP INBOARD ISOLATION VALVE (EPID L-2023-LLR-0040)
Dear Mr. Hafen:
By letter dated July 31, 2023, Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (NSPM, the licensee) submitted a request to the U.S. Nuclear Regulatory Commission (NRC) for the use of an alternative to certain American Society of Mechanical Engineers (ASME) for Operation and Maintenance of Nuclear Power Plants (OM Code) requirements at Monticello Nuclear Generating Plant (Monticello).
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(2), the licensee requested to use an alternative to the 10-year test frequency for inservice diagnostic testing of reactor water cleanup inboard isolation valve MO-2397 on the basis that complying with the specified requirement would result in hardship or unusual difficulty. The licensee proposed to perform the test at a frequency of 12 years until the completion of the spring 2025 refueling outage (RFO) at Monticello.
The NRC staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that the licensee has demonstrated that a hardship or unusual difficulty, without a compensating increase in the level of quality and safety, would exist to perform inservice diagnostic testing of MO-2397 at the required interval specified in the ASME OM Code prior to the spring 2025 RFO at Monticello. Additionally, the NRC staff has determined that the proposed alternative will provide reasonable assurance that MO-2397 will be operationally ready to perform its safety functions until the spring 2025 RFO. As a result, the NRC staff concludes that the licensees proposed alternative for a one-time extension of the inservice diagnostic testing interval for MO-2397 to the spring 2025 RFO meets the regulatory requirements as set forth in 10 CFR 50.55a(z)(2).
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) remain applicable.
S. Hafen If you have any questions, please contact the Project Manager, Brent Ballard, at 301-415-0680 or via e-mail at Brent.Ballard@nrc.gov.
Sincerely, Digitally signed by Jeffrey A. Jeffrey A. Whited Date: 2023.09.18 Whited 14:58:33 -04'00' Jeffrey A. Whited, Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No(s). 50-263
Enclosure:
Safety Evaluation cc: ListServ
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PROPOSED ALTERNATIVE VR-11 REGARDING REACTOR WATER CLEANUP INBOARD ISOLATION VALVE MO-2397 NORTHERN STATES POWER COMPANY MONTICELLO NUCLEAR GENERATING PLANT DOCKET NO. 50-263
1.0 INTRODUCTION
By letter dated July 31, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23212A963), Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (the licensee) requested that the U.S. Nuclear Regulatory Commission (NRC) authorize the use of a proposed alternative to certain inservice testing (IST) program requirements of the American Society of Mechanical Engineers (ASME)
Operation and Maintenance of Nuclear Power Plants, Division 1, OM Code: Section Inservice Testing (OM Code), associated with inservice testing of a motor-operated valve (MOV) at the Monticello Nuclear Generating Plant (Monticello).
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(2)
Alternatives to codes and standards requirements, the licensee requested to implement proposed alternative request (AR) VR-11, which would allow a one-time extension of the frequency for the inservice diagnostic test from 10 years to 12 years for reactor water clean-up (RWCU) inboard isolation valve MO-2397 as an alternative to the specified 10-year frequency requirement in the ASME OM Code. The basis for the request is that compliance with the MOV diagnostic testing requirement would result in 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.
Enclosure
The NRC regulations in 10 CFR 50.55a(z), Alternatives to codes and standards requirements, state that alternatives to the requirements of paragraphs (b) through (h) of 10 CFR 50.55a 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 Proposed Alternative VR-11 Applicable ASME OM Code Edition The licensees OM Code of Record is the 2017 Edition of the ASME OM Code for the IST program at Monticello for the sixth 10-year interval, which commenced on October 1, 2022, and is currently scheduled to end on May 31, 2032.
ASME OM Code Components Affected In its submittal, the licensee proposed alternative testing for the following MOV:
Component Code System OM Category Number Class MO-2397 RWCU 1 A Applicable ASME OM Code Requirements The IST requirements in the ASME OM Code, as incorporated by reference in 10 CFR 50.55a, related to AR VR-11 are as follows:
ASME OM Code, Division 1, Section IST, Subsection ISTC, Inservice Testing of Valves in Water-Cooled Reactor Nuclear Power Plants, paragraph ISTC-5120, Motor-Operated Valves states:
Active MOVs shall meet the requirements of Mandatory Appendix III of this Division.
ASME OM Code, Division 1, Section IST, Mandatory Appendix III, Preservice and Inservice Testing of Active Electric Motor-Operated Valve Assemblies in Water-Cooled Reactor Nuclear Power Plants, paragraph III-3300, Inservice Test, states, in part:
(b) Inservice tests shall be conducted in the as-found condition. Activities shall not be conducted if they invalidate the inservice test results. If maintenance is needed between
the inservice tests, see para. III-3400. As-found testing is not required prior to maintenance activities as long as the MOV is not due for an inservice test. If maintenance activities are scheduled concurrently with an MOVs inservice test, then the inservice test shall be conducted in the as-found condition, prior to the maintenance activity.
ASME OM Code, Division 1, Section IST, Mandatory Appendix III, paragraph III-3310, Inservice Test Interval, subparagraph (c), states:
The maximum inservice test interval shall not exceed 10 yr [years]. MOV inservice tests conducted per para. [paragraph] III-3400 may be used to satisfy this requirement.
ASME OM Code, Division 1, Section IST, Mandatory Appendix III, paragraph III-3722, LSSC MOVs, subparagraph (d), states:
LSSC [Low Safety-Significant Component] MOVs shall be inservice tested at least every 10 yr in accordance with para. III-3310.
ASME OM Code, Division 1, Section IST, Subsection ISTA, General Requirements, paragraph ISTA-3170, Inservice Examination and Test Frequency, states, in part:
For periods specified as greater than or equal to 2 yr, the period may be extended by up to 6 months for any given test.
Proposed Alternative and Basis for Use In AR VR-11, the licensee proposed a one-time extension of the frequency for the inservice diagnostic test (also referred to as periodic verification test (PVT) by the licensee in its IST program plan and proposed alternative) from 10 years to 12 years for RWCU inboard isolation valve MO-2397, which will allow performance of this test during the spring 2025 refueling outage (RFO) at Monticello. AR VR-11 specified that the frequency would return to the required Mandatory Appendix III frequency after completion of the spring 2025 RFO. In VR-11, the licensee requested use of the proposed alternative for MO-2397 on the basis that compliance with the MOV diagnostic testing requirement would result in a hardship without a compensating increase in the level of quality and safety in accordance with 10 CFR 50.55a(z)(2).
Reason for Request
In its submittal, the licensee stated that the as-found PVT with subsequent mechanical preventive maintenance (PM) was scheduled for MO-2397 during the spring 2023 RFO at Monticello. Due to a human performance issue, the mechanical PM was performed prior to the as-found PVT, which precluded the completion of the PVT in accordance with ASME OM Code, Mandatory Appendix III, paragraph III-3300. The previous PVT for MO-2397 was completed on April 8, 2013, thus a PVT was required during the 2023 RFO per ASME OM Code, Mandatory Appendix III, paragraphs III-3310 and III-3722, to satisfy the 10-year frequency requirement.
The licensee provided additional information in its submittal which is discussed in section 3.2, NRC Staff Evaluation below.
3.2 NRC Staff Evaluation The 2017 Edition of the ASME OM Code, Mandatory Appendix III, as incorporated by reference in 10 CFR 50.55a, requires active safety-related MOVs to be periodically diagnostic tested at an interval not to exceed 10 years to demonstrate their capability to perform the specific safety functions. When determining the proper diagnostic test interval, the MOV program engineer at a nuclear power plant considers all potential performance-related degradations that could impact the capability of each MOV to perform its safety functions. The diagnostic test interval needs to be established such that the MOV functional margin does not decrease below the acceptance criteria for demonstrating its design-basis capability.
In section 3.1 of this safety evaluation, the NRC staff described the licensees proposed alternative and the basis for use.
Valve MO-2397 at Monticello is currently being tested at the specified 10-year interval and was due to be tested during the spring 2023 RFO. Valve MO-2397 is located in a locked high radiation area, which requires a plant outage to access the valve and perform the specified diagnostic testing. Installation and removal of scaffolding and shielding is also required to conduct this testing. The licensee reports that approximately 4.2 rem was received during the 2023 RFO through activities supporting the PM and associated testing. The licensee states that a forced outage would present an opportunity to perform an as-found PVT of MO-2397 but would result in additional radiation exposure and personnel safety risk. Additionally, the licensee notes that the data obtained from a mid-cycle as-found test would not be representative of a typical as-found test because there has been less than 2 years of inservice time since the mechanical PM was performed on MO-2397.
In AR VR-11, the licensee provided the calculated MOV functional margin for MO-2397 in both 2017, when the MO-2397 actuator was replaced, and 2023, after performing maintenance. The diagnostic testing showed a 15.2 percent positive functional margin in 2017 with the measured packing load and an 11.0 percent as-left functional margin with measured packing load in 2023.
The licensee noted that the leakage testing required by 10 CFR Part 50, Appendix J, of MO-2397 was accomplished in 2023. The licensee stated that valve functional margin of MO-2397 is expected to remain positive for the duration of the alternative. To support its request, the licensee relied on the valves history of preventative maintenance (including the 2017 replacement of the actuator) as well as the calculated functional margin of MO-2397.
In response to the licensees request, the NRC staff reviewed the maintenance history and results of testing of MO-2397 provided by the licensee. The staff determined that the licensee has justified that MO-2397 has sufficient margin to support extension of the MOV diagnostic test interval to the spring 2025 RFO at Monticello. The staff has determined that requiring MO-2397 to be diagnostically tested within the specified 10-year interval with the 6-month extension allowed by ASME OM Code, Subsection ISTA, paragraph ISTA-3170, represents a hardship or unusual difficulty, without a compensating increase in the level of quality or safety, as the test would require a forced plant outage and additional radiation exposure and personnel safety risk to obtain as-found test data for MO-2397 that is not representative of a full interval as-found test due to the limited inservice time since the mechanical PM performed during the spring 2023 RFO.
Based on the information provided by the licensee for MO-2397 in AR VR-11, the NRC staff found that (1) previous testing of MO-2397 indicates acceptable historical performance, (2) ongoing IST activities have not identified MOV performance concerns, (3) periodic maintenance
activities have been completed and will continue, and (4) a hardship exists for the performance of diagnostic testing of this MOV during a forced plant outage that would be contrary to the health and safety of plant personnel. Further, the proposed alternative will provide reasonable assurance that MO-2397 will be operationally ready to perform its safety functions until the spring 2025 RFO at Monticello. Therefore, the NRC staff determines that the licensees proposed alternative for a one-time extension of the diagnostic testing interval for MO-2397 to the spring 2025 RFO at Monticello is acceptable, in accordance with 10 CFR 50.55a(z)(2).
4.0 CONCLUSION
As set forth above, the NRC staff has determined that the licensee has demonstrated that a hardship or unusual difficulty, without a compensating increase in the level of quality and safety, would exist to perform the inservice diagnostic test of RWCU inboard isolation valve MO-2397 at the required interval specified in the ASME OM Code prior to the spring 2025 RFO at Monticello. Additionally, the NRC staff has determined that proposed alternative VR-11 will provide reasonable assurance that MO-2397 will be operationally ready to perform its safety functions until the spring 2025 RFO at Monticello. As a result, the NRC staff concludes that the licensees proposed alternative for a one-time extension of the diagnostic testing interval for MO-2397 to the spring 2025 RFO at Monticello meets the regulatory requirements set forth in 10 CFR 50.55a(z)(2). Therefore, the NRC staff authorizes alternative VR-11 until the completion of the spring 2025 RFO at Monticello, which is scheduled to start in April 2025.
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: Nicholas Hansing Nachiketh Chandran Date: September 18, 2023
ML23248A209 OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA NRR/DEX/EMIB/BC NRR/DSS/SCPB/BC NRR/DORL/LPL3/BC NAME BBallard SRohrer SBailey BWittick JWhited DATE 9/5/2023 9/5/2023 8/18/2023 9/9/2023 9/18/2023