ML20174A545

Request for Alternative for Pressure Isolation Valve Testing

ML20174A545
Person / Time
Site:	Monticello
Issue date:	07/15/2020
From:	Nancy Salgado Plant Licensing Branch III
To:	Conboy T Northern States Power Company, Minnesota
Kuntz R
References
EPID L-2020-LLR-0006
Download: ML20174A545 (8)

Text

July 15, 2020 Mr. Thomas Conboy 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 - REQUEST FOR ALTERNATIVE FOR PRESSURE ISOLATION VALVE TESTING (EPID L-2020-LLR-0006)

Dear Mr. Conboy:

By letter dated January 16, 2020, Northern States Power Company, Minnesota (NSPM, the licensee) submitted an alternative request to inservice testing (IST) program requirements of the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code), 2004 Edition through the 2006 Addenda, at the Monticello Nuclear Generating Plant (MNGP) for the remainder of the fifth 10-year IST program interval.

Specifically, pursuant to subparagraph (1) 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, Energy, of Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(1), the proposed alternative, VR 05, Request for Approval of an Alternative for Pressure Isolation Valve Testing, was requested on the basis that the alternative provides an acceptable level of quality and safety.

As set forth in the enclosed safety evaluation, the U.S. Nuclear Regulatory Commission (NRC) staff has determined that alternative request VR 05 for MNGP describes a process to justify an extension of the leakage testing intervals for the valves listed that provides an acceptable level of quality and safety. Accordingly, the NRC staff concludes that alternative request VR 05 adequately addresses the regulatory requirements set forth in 10 CFR 50.55a(z)(1). As a result of the loss of test data, the VR 05 process requires two documented successful consecutive tests for MO-2029 and MO-2030 before extending their test intervals. Based on its review, the NRC staff authorizes the use of alternative request VR 05 at MNGP for the remainder of the fifth 10-year IST program interval, which is scheduled to end on May 31, 2022.

All other ASME OM Code requirements for which relief or an alternative was not specifically requested and approved as part of this subject request remain applicable.

If you have any questions, please contact Robert Kuntz at 301-415-3733 or via e-mail at Robert.Kuntz@nrc.gov.

Sincerely, Nancy L. Salgado, Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-263

Enclosure:

Safety Evaluation cc: Listserv Nancy L.

Salgado Digitally signed by Nancy L. Salgado Date: 2020.07.15 08:55:03

-04'00'

Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR RELIEF VR 05 NORTHERN STATES POWER COMPANY - MINNESOTA MONTICELLO NUCLEAR GENERATING PLANT DOCKET NO. 50-263

1.0 INTRODUCTION

By letter dated January 16, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20016A406), Northern States Power Company (licensee) submitted an alternative request for authorization by the U.S. Nuclear Regulatory Commission (NRC) to inservice testing (IST) program requirements of the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code), 2004 Edition through the 2006 Addenda, at the Monticello Nuclear Generating Plant (MNGP) for the remainder of the fifth 10-year IST program interval.

Specifically, pursuant to subparagraph (1) 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, Energy, of Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(1)), the proposed alternative, VR 05, Request for Approval of an Alternative for Pressure Isolation Valve Testing, was requested on the basis that the alternative provides an acceptable level of quality and safety.

2.0 REGULATORY EVALUATION

The NRC regulations in 10 CFR 50.55a(f), 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) state that alternatives to the requirements of paragraph (f) of 10 CFR 50.55a may be used, when authorized by the NRC if the licensee demonstrates: (1) the proposed alternatives would provide an acceptable level of quality and safety or (2) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

The applicable ASME OM Code of Record for the IST program at MNGP for the fifth 10-year IST program interval is the 2004 Edition through 2006 Addenda (OMb-2006) of the ASME OM Code as incorporated by reference in 10 CFR 50.55a. The fifth 10-year IST program interval at MNGP is scheduled to end on May 31, 2022.

3.0 TECHNICAL EVALUATION

3.1 Alternative Request RV 05 The IST requirements of 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-3522, Category C Check Valves, states that Category C check valves shall be exercised as follows:

(a) During operation at power, each check valve shall be exercised or examined in a manner that verifies obturator travel by using the methods in ISTC-5221.

(b) If exercising is not practicable during operation at power and cold shutdowns, it shall be performed during refueling outages.

ASME OM Code, Subsection ISTC, paragraph ISTC-3630, Leakage Rate for Other Than Containment Isolation Valves, states, in part:

Category A valves with a leakage requirement not based on an Owner's 10 CFR 50, Appendix J, program, shall be tested to verify their seat leakages within acceptable limits. Valve closure before seat leakage testing shall be by using the valve operator with no additional closing force applied.

ASME OM Code, Subsection ISTC, paragraph ISTC-3630(a), Frequency, states Tests shall be conducted at least once every 2 years.

VR 05 requests alternative testing for the following pressure isolation valves (PIVs) associated with the residual heat removal (RHR) and the core spray (CS) systems.

Table 1 Valve Identifier Description System ASME Code Class OM Cat.

MO-2014 RHR Low Pressure Coolant Injection (LPCI)

Inboard Isolation Valve RHR 1

A MO-2015 RHR LPCI Inboard Isolation Valve RHR 1

A MO-1753 11 Core Spray (CS) System Motor Operated Inboard Injection Valve CS 1

A MO-1754 12 Core Spray System Motor Operated Inboard Injection Valve CS 1

A Valve Identifier Description System ASME Code Class OM Cat.

MO-2029 Reactor Coolant to RHR Shutdown Cooling Supply Isolation Valve RHR 1

A MO-2030 Reactor Coolant to RHR Shutdown Cooling Supply Isolation Valve RHR 1

A RHR-81 Thermal Overpressurization Relief Check Valve for Penetration X-12 RHR 1

AC AO-10-46A RHR Injection Check Valve RHR 1

AC AO-10-46B RHR Injection Check Valve RHR 1

AC AO-14-13A 11 Core Spray Injection Air-Operated Check Valve CSP 1

AC AO-14-13B 12 Core Spray Injection Air-Operated Check Valve CSP 1

AC

=

Reason for Request===

VR 05 states that the proposed alternative is to allow historically good performing PIVs listed in Table 1 of this safety evaluation to be exercised and leak tested on a performance-based schedule. A performance-based schedule will allow divisional outages to reduce required resources and reduce radiation dose accumulated during testing. VR 05 states that the proposed extended intervals would provide a dose savings of 1.7 rem (Roentgen equivalent man) over three refueling outages (RFOs). Dose reduction is consistent with NRC and industry as low as reasonably achievable radiation dose principles.

Proposed Alternative and Basis for Use The specific test interval for each PIV is proposed to be a function of its performance and be established in a manner consistent with the containment isolation valve testing process under 10 CFR 50, Appendix J, Option B. Performance-based scheduling of PIV testing will be controlled in a manner similar to the methods described in Nuclear Energy Institute (NEI) 94-01, Revision 3-A. PIV test performances would occur at a nominal frequency ranging from every RFO to every third RFO, subject to acceptable valve performance. Valves that have demonstrated good performance for two consecutive cycles may have their test interval extended up to 75-months, with a permissible extension (for non-routine emergent conditions) of 9 months (84 months total).

A conservative control will be established such that if any valve fails the PIV test, the test interval will be reduced consistent with Appendix J, Option B, requirements. Any PIV leakage test failure would require the component to return to the initial interval of every 30 months until good performance can again be established.

3.2

NRC Staff Evaluation

As incorporated by reference in 10 CFR 50.55a, ASME OM Code (2004 Edition through 2006 Addenda), paragraph ISTC-3630(a), requires that valves within the scope of the ASME OM Code that have specific leakage criteria (other than containment isolation valves that are tested in accordance with 10 CFR Part 50, Appendix J), are required to be leak rate tested at least once every 2 years. RV 05 proposed an alternative test in lieu of this requirement for the 11 specific PIVs listed. Specifically, RV 05 proposes to functionally test and verify the leakage rate of these 11 PIVs using a 10 CFR Part 50, Appendix J, Option B, performance-based schedule.

Valves would initially be tested at the required interval schedule, which is every RFO or 2 years (plus as much as 6 months grace as permitted by Appendix J, Option B) as specified by ASME OM Code, Subsection ISTC, paragraph ISTC-3630(a). Valves that have demonstrated good performance for two consecutive cycles may have their test interval extended to 75 months with a permissible extension for non-routine emergent conditions of nine months (84 months total).

Any valve leakage test failure would require the component to return to the initial interval of every 30 months until good performance can again be established.

Regulation 10 CFR Part 50, Appendix J, Option B, is a performance-based containment leakage test program. Guidance for implementation of acceptable leakage rate test methods, procedures, and analyses is provided in NRC Regulatory Guide (RG) 1.163, Performance Based Containment Leak Test Program (ADAMS Accession No. ML003740058). RG 1.163 endorses NEI Topical Report (TR) 94-01, Revision 0, Industry Guideline for Implementing Performance Based Option of 10 CFR 50, Appendix J, dated July 26, 1995, with the limitation that Type C components test interval cannot extend greater than 60 months. The current version of NEI 94-01 is Revision 3-A, which allows Type C containment isolation valve test intervals to be extended to 75 months with a permissible extension for non-routine emergent conditions of 9 months (84 months total). In a [[letter::L-MT-12-077, License Amendment Request: Adoption of Technical Specifications Task Force (TSTF) Traveler TSTF-484, Revision 0, Use of TS 3.10.1 for Scram Time Testing Activities|letter dated December 6, 2012]], the NRC staff found the guidance in NEI 94-01, Revision 3-A, to be acceptable (see ADAMS Accession Nos.

ML121030286 and ML12226A546) with the following conditions:

1) Extended interval for Type C local leak-rate tests (LLRTs) may be increased to 75 months with the requirement that a licensees post-outage report include the margin between Type B and Type C leakage rate summation and its regulatory limit. In addition, a corrective action plan shall be developed to restore the margin to an acceptable level. Extensions of up to nine months (total maximum interval of 84 months for Type C tests) are permissible only for non-routine emergent conditions. This provision (nine-month extension) does not apply to valves that are restricted and/or limited to 30-month intervals in Section 10.2 (such as boiling water reactor main steam isolation valves) or to valves held to the base interval (30 months) due to unsatisfactory LLRT performance.

2) When routinely scheduling any LLRT valve interval beyond 60 months and up to 75 months, the primary containment leakage rate testing program trending or monitoring must include an estimate of the amount of understatement in the Type B & C total and must be included in a licensees post-outage report. The report must include the reasoning and determination of the acceptability of the extension, demonstrating that the LLRT totals calculated represent the actual leakage potential of the penetrations.

VR 05 states that leakage test results for the specific PIVs at MNGP showed historically good performance for four consecutive RFOs. However, the 2019 results for the reactor coolant to RHR shutdown cooling supply isolation valves (MO-2029 and MO-2030) were lost, although they tested within acceptance criteria. In addition to the good performance, VR 05 noted that the leakage test of the 11 PIVs places a burden on test personnel being exposed to radiation.

An overall dose savings of 1.7 rem over the course of three RFOs can be attained by extending the test intervals to a 10 CFR Part 50, Appendix J, Option B, performance-based schedule.

The NRC staff reviewed the historical performance data of the PIVs listed in the submittal. The staff found that the specific PIVs at MNGP have had good performance history with the exception of the missing testing results for MO-2029 and MO-2030 from the 2019 RFO.

Therefore, MO-2029 and MO-2030 will require the documentation of two successful consecutive tests before their test intervals may be extended.

Based on its review of the specified PIVs at MNGP identified in the submittal, the NRC staff finds that proposed alternative VR 05 for a process to justify an extension of the leakage testing intervals for these PIVs at MNGP provides an acceptable level of quality and safety in accordance with 10 CFR 50.55a(z)(1). As a result of the loss of test data, successful consecutive tests for MO-2029 and MO-2030 are required to justify extending the test interval for these valves.

4.0 CONCLUSION

As set forth above, the NRC staff has determined that alternative request RV 05 for MNGP describes a process to justify an extension of the leakage testing intervals for the valves listed that provides an acceptable level of quality and safety. Accordingly, the NRC staff concludes that alternative request VR 05 adequately addresses the regulatory requirements set forth in 10 CFR 50.55a(z)(1). As a result of the loss of test data, the VR 05 process requires two documented successful consecutive tests for MO-2029 and MO-2030 before extending their test intervals. Based on its review, the NRC staff authorizes the use of alternative request RV 05 at MNGP for the remainder of the fifth 10-year IST program interval, which is scheduled to end on May 31, 2022.

All other ASME OM Code requirements for which relief or an alternative was not specifically requested and approved as part of this subject request remain applicable.

Principal Contributor: J. Huang, NRR Date: July 15, 2020

ML20174A545 OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA NRR/DEX/EMIB/BC NRR/DORL/LPL3/BC NAME RKuntz SRohrer ABuford NSalgado DATE 6/23/2020 6/23/2020 6/15/2020 7/15/2020