ML23107A285
| ML23107A285 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 04/25/2023 |
| From: | V Sreenivas Plant Licensing Branch III |
| To: | Domingos C Northern States Power Company, Minnesota |
| Ballard, B | |
| References | |
| EPID L-2022-LLR-0088 | |
| Download: ML23107A285 (1) | |
Text
April 25, 2023 MONTICELLO NUCLEAR GENERATING PLANT - AUTHORIZATION AND SAFETY EVALUATION FOR ALTERNATIVE REQUEST PR-08 (EPID L-2022-LLR-0088)
LICENSEE INFORMATION Recipients Name and Address:
Mr. Christopher P. Domingos Site Vice President Northern States Power Company
- Minnesota Monticello Nuclear Generating Plant 2807 West County Road 75 Monticello, MN 55362 Licensee:
Northern States Power Company Plant Name and Unit:
Monticello Nuclear Generating Plant (MNGP)
Docket No.
50-263 APPLICATION INFORMATION Submittal Date:
December 15, 2022 Submittal Agencywide Documents Access and Management System (ADAMS) Accession No. ML22350A726 Supplement Date:
January 6, 2023 Supplement ADAMS Accession No. ML23006A277 Applicable Inservice Testing (IST) Program Interval and Interval Start/End Dates: MNGP sixth 10-year Interval IST program began October 1, 2022, and is scheduled to end May 31, 2032.
10 CFR 50.55a Alternative Requirement: The licensee submitted Alternative Request PR-08 for MNGP under Title 10 of the Code of Federal Regulations (10 CFR), paragraph 50.55a(z)(2),
on the basis that compliance with specific IST program requirements in the American Society of Mechanical Engineers (ASME) Operation and Maintenance of Nuclear Power Plants, Division 1, OM Code: Section IST (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 and safety.
Proposed Duration of Alternative: The licensee requested that this alternative be authorized until MNGP's spring 2023 refueling outage (RFO), which is scheduled to start April 15, 2023.
Applicable Code Edition and Addenda: ASME OM Code, 2017 Edition, as incorporated by reference in 10 CFR 50.55a, for the sixth 10-year Interval IST program at MNGP.
Applicable IST Requirements:
2017 Edition of the ASME OM Code, Subsection ISTC, Inservice Testing of Valves in Water-Cooled Reactor Nuclear Power Plants.
Subsection ISTA, General Requirements, paragraph ISTA-3170, Inservice Examination and Test Frequency Grace, specifies, in part, that components whose test frequencies are based on elapsed time periods shall be tested per table ISTA-3170-1, Test Frequency and Time Between Tests, which requires, for quarterly (every 3 months) testing, that the specified time between tests is 92 days.
Subsection ISTB, Inservice Testing of Pumps in Water-Cooled Reactor Nuclear Power Plants -
Pre-2000 Plants, paragraph ISTB-3400, Frequency of Inservice Tests, states that an IST shall be run on each pump as specified in table ISTB-3400-1, Inservice Test Frequency, which specifies a quarterly Group A Test for Pump Group A.
Subsection ISTC, Inservice Testing of Valves in Water-Cooled Reactor Nuclear Power Plants, paragraph ISTC-3510, Exercising Test Frequency, states, in part:
Active Category A, Category B, and Category C check valves shall be exercised nominally every 3 months,...
Mandatory appendix III, Preservice and Inservice Testing of Active Electric Motor-Operated Valve Assemblies in Water-Cooled Reactor Nuclear Power Plants, paragraph III-3721, HSSC
[High Safety Significance Component] MOVs [Motor-Operated Valves], states, in part:
HSSC MOVs that can be operated during plant operation shall be exercised quarterly,....
Brief Description of Proposed Alternative: The proposed alternative is to defer the quarterly testing of components in the high-pressure coolant injection (HPCI) system until the 2023 spring RFO when repairs to the 'G' SRV (safety relief valve) will be completed.
For additional details on the licensees request, please refer to the documents located at the ADAMS Accession numbers identified above.
NRC STAFF EVALUATION On December 15, 2022, the licensee submitted Alternative Request PR-08 with a supplemental letter dated January 6, 2023, proposing to defer the quarterly testing of certain components in the HPCI system at Monticello until the 2023 spring RFO when repairs to SRV RV-2-71G (referred to as the G SRV) would be conducted. The licensee submitted Alternative Request PR-08 in accordance with 10 CFR 50.55a(z)(2) on the basis that performance of HPCI required by the ASME OM Code for specific components in the HPCI system prior to the spring 2023 RFO at Monticello would cause a hardship or unusual difficulty without a compensating increase in the level of quality and safety. With the required dates for testing the HPCI components
approaching in January 2023, the NRC staff determined that it would be most efficient and effective to review Alternative Request PR-08 using the NRC verbal authorization process.
The HPCI system components within the scope of Alternative Request PR-08 are the follows:
HPCI-18, HPCI Gland Seal Condenser/Lube Oil Cooler Cooling Water Return Check Valve HPCI-20, HPCI Gland Seal Condenser/Condensate Pump Discharge Check Valve HPCI-32, HPCI Pump Suction from Condensate Storage Tank Check Valve HPCI-9, HPCI Turbine Exhaust Check Valve HPCI-10, HPCI Turbine Exhaust Check Valve MO-2036, HPCI Turbine Steam Supply Isolation Valve P-209, HPCI Pump In Alternative Request PR-08, the licensee specified that SRV RV-2-71G has an elevated tailpipe temperature which might be indicative of pilot or second stage leakage. When HPCI pump P-209 is activated for IST, the licensee indicated that there is a potential for a spurious lift of the G SRV that might result in a plant transient and require a rapid power reduction or reactor scram. Therefore, the licensee requested deferral of the quarterly ISTB-3400 Group A pump test for HPCI pump P-209, and the quarterly ISTC-3510 exercising of the HPCI-9, HPCI-10, HPCI-18, HPCI-20, and HPCI-32 check valves. In addition, the licensee requested deferral of the quarterly exercising of MOV MO-2036 required by Mandatory appendix III, paragraph III-3721. The licensee stated that normal IST of the HPCI system will resume following the replacement of the G SRV during the spring 2023 RFO that is scheduled to start on April 15, 2023.
In Alternative Request PR-08, the licensee stated that it had reviewed the maintenance history and inservice testing results for the specified HPCI components. The licensee determined that the HPCI components would retain their operational readiness with the deferral of the specified ISTs. In its initial submittal, the licensee provided a brief summary of the testing history of the components within the scope of Alternative Request PR-08.
Based on the review of the initial submittal for the alternative request, the U.S. Nuclear Regulatory Commission (NRC) staff requested on January 4, 2023 (ML23004A198), that the licensee provide specific information regarding the performance and testing history of the HPCI components within the scope of the request, and other clarifying information.
In its supplemental submittal dated January 6, 2023, the licensee provided the results of several recent quarterly and biennial tests of the HPCI-9, HPCI-10, HPCI-18, HPCI-20, and HPCI-32 check valves, and their recent preventive maintenance and leak tightness history. The supplemental information for the HPCI check valves showed satisfactory test results, and no history of failure of these check valves to open or close. The licensee reported that leak tightness testing for the HPCI check valves occurs during RFOs and will be performed per the normal periodicity without deferral.
In the supplemental submittal, the licensee provided the results of the last three quarterly tests of HPCI pump P-209 with the acceptance criteria for flow, differential pressure, and vibration, demonstrating its stable performance. The licensee also described the satisfactory results of recent oil sample evaluations for the HPCI pump P-209. The licensee clarified that the fourth quarter 2022 test of the HPCI pump P-209 with its grace period until January 15, 2023, allowed by ASME OM Code, subsection ISTA, paragraph ISTA-3170, was also requested to be deferred
together with the pump ISTs in the first quarter of 2023 prior to the spring 2023 RFO at Monticello.
In the supplemental submittal, the licensee provided an estimate of the capability margin for the motor actuator to open MOV MO-2036 based on the potential required thrust to open the valve and the closing thrust measured during diagnostic testing. The NRC staff considered the licensees report of successful diagnostic testing of MOV MO-2036 to be sufficient for the verbal authorization process. The NRC staff determined that clarifying information regarding the licensees estimation of the capability margin for MOV MO-2036 would be obtained for the written safety evaluation.
In its review of Alternative Request PR-08 (as supplemented), the NRC staff evaluated (1) the licensees description of the specific ISTs proposed to be deferred for the HPCI components within the scope of the alternative request, (2) the performance and testing history of the applicable HPCI components, (3) the licensees plans to conduct repairs to the G SRV during the spring 2023 RFO, and (4) the re-initiation of the ISTs required by the ASME OM Code following the spring 2023 RFO at Monticello.
Based on its review, the NRC staff provided verbal authorization of Alternative Request PR-08 (as supplemented) on January 12, 2023 (ML23017A222), to defer the specified ISTs for HPCI pump P-209 and the applicable valves until the spring 2023 RFO at Monticello. Following issuance of the verbal authorization, the NRC staff held a public meeting with the licensee on March 8, 2023 (ML23074A121), for clarification of the licensees estimate of the capability margin for MOV MO-2036. Based on the public meeting discussion, the NRC staff notes that the estimation method used by the licensee in support of Alternative Request PR-08 differs from the method of calculating MOV capability margin accepted by the NRC staff. As a result, the NRC staff does not rely on the specific amount of capability margin estimated by the licensee for MOV MO-2036 in this review of Alternative Request PR-08.
Based on the information provided by the licensee (including the March 8, 2023, public meeting), 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 in the ASME OM Code for HPCI pump P-209 and the applicable valves until the spring 2023 RFO at Monticello. Based on the satisfactory performance and testing history for the applicable HPCI components described by the licensee, the NRC staff finds that the licensees proposed alternative to defer the first quarter 2023 ISTs for the applicable HPCI components would not adversely impact the reasonable assurance that those components will be operationally ready to perform their safety functions until the spring 2023 RFO when the G SRV will be repaired at Monticello.
CONCLUSION On January 12, 2023, the NRC staff provided a verbal authorization of Alternative Request PR-08 (as supplemented) to defer the specified ISTs for HPCI pump P-209 and the applicable valves until the spring 2023 RFO at Monticello. As described above, the NRC staff finds that the licensee justified in Alternative Request PR-08 that performance of IST required by the ASME OM Code for specific components in the HPCI system prior to the spring 2023 RFO at Monticello would have caused a hardship or unusual difficulty without a compensating increase in the level of quality and safety. The NRC staff finds that Alternative Request PR-08 provides reasonable assurance that components within the scope of the request will be operationally ready to perform their safety functions until the spring 2023 RFO at Monticello. Accordingly, the
NRC staff concludes that the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(2). Consistent with the verbal authorization provided on January 12, 2023, the NRC staff authorizes the use of Alternative Request PR-08 (as supplemented) until the spring 2023 RFO at Monticello. The NRC staff authorization of Alternative Request PR-08 (as supplemented) expires upon completion of the spring 2023 RFO at Monticello.
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:
Chakrapani Basavaraju, NRR/DEX/EMIB Thomas Scarbrough, NRR/DEX/EMIB Date: April 25, 2023 V. Sreenivas, Acting Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation cc: Listserv Digitally signed by Venkataiah Sreenivas Date: 2023.04.25 16:39:40 -04'00'
ML23107A285 OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA NRR/DEX/EMIB/BC NRR/DORL/LPL3/BC(A)
NAME BBallard SRohrer SBailey VSreenivas DATE 4/17/2023 4/18/2023 4/14/2023 4/25/2023