ML15345A006

Safety Evaluation by the Office of Nuclear Reactor Regulation for Request MSS-VR-01 R1

ML15345A006
Person / Time
Site:	Nine Mile Point
Issue date:	01/29/2016
From:	Travis Tate Plant Licensing Branch 1
To:	Bryan Hanson Exelon Generation Co
Mozafari B
References
CAC MF5773
Download: ML15345A006 (8)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 January 29, 2016 Mr. Bryan Hanson President and Chief Nuclear Officer Exelon Generation Company, LLC 4.300 Winfield Road Warrenville, IL 60555

SUBJECT:

NINE MILE POINT NUCLEAR STATION, UNIT 2 - SAFETY EVALUATION BY THE OFFICE OF NUC,LEAR REACTOR REGULATION FOR RELIEF REQUEST MSS-VR-01, REVISION 1 (CAC NO. MF5773)

Dear Mr. Hanson By letter to the U.S. Nuclear Regulatory Commission (NRC) dated February 16, 2015 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML15047A003), Exelon Generation Company, LLC (the licensee) submitted Revision 1 to Relief Request (RR) MSS-VR-01 for the third interval of the 10-year inservice testing (IST) program at Nine Mile Point Nuclear Station, Unit 2 (NMP2). RR MSS-VR-01, Revision 0, was authorized by the NRC staff for the NMP2 third interval of the 10-year IST program by letter dated December 29, 2008 (ADAMS Accession No. ML083500039). The request proposes an alternative to the test intervals specified in the American Society of Mech,anical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code).

Specifically, pursuant to Title 10 of the Code of Federal Regulations (:10 CFR) 50.55a(z)(1 ), the licensee requested to use the proposed alternative in RR MSS-VR-01, Revision 1, on the basis

. that the alternative provides an acceptable level of quality and safety.

The NRC staff has completed its review of the subject request as documented in the enclosed Safety Evaluation (SE). The SE concludes that the prqposed alternatives described in RR MSS-VR-01, Revision 1, provide an acceptable level of quality and safety for testing of the NMP2 main steam safety relief valves. Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(z)(1) for RR MSS-VR-01, Revision 1, and is in compliance with the ASME OM Code requirements.

All other ASME OM Code requirements for which relief was not specifically requested and approved remain applicable.

B. Hanson If you have any questions concerning this matter, please contact the NMP2 Senior Project Manager, Mrs. Brenda Mozafari, at (301) 415-2020 or Brenda.Mozafari@nrc.gov .

. Sincerely, o~d~

Travis L Tate, Chief Plant Licensing Branch 1-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-410

Enclosure:

Safety Evaluation cc w/enclosure: Distribution via Listserv

UNITED STATES NUCLEAR R~GULATORY. COMMISSION WASHINGTON, D.C. 20555..0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION INSERVICE TESTING PROGRAM RELIEF REQUEST MSS-VR-01, REVISION 1 THIRD 10-YEAR INTERVAL EXELON GENERATION COMPANY, LLC NINE MILE POINT NUCLEAR STATION. UNIT 2 DOCKET NO. 50-410

1.0 INTRODUCTION

By letter to the U.S. Nuclear Regulatory Commission (NRG) dated February 1~. 2015 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML15047A003), Exelon Generation Company, LLC (Exelon or the licensee), submitted Revision 1 to Relief Request (RR) MSS-VR-01 for the third interval of the 10-year inservice testing (IST) program at Nine Mile Point Nuclear Station, Unit 2 (NMP2). RR MSS-VR-01, Revision 0, was authorized by the NRG staff for the NMP2 third interval of the 10-year IST program by letter dated December 29, 2008 (ADAMS Accession No. ML083500039). The request proposes an alternative to test intervals specified in the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants* (OM Code).

Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(1), the licensee requested to use the proposed alternative in RR MSS-VR-01, Revision 1, on the basis that the alternative provides an acceptable level of quality and safety.

2.0 REGULATORY EVALUATION

Section 50.55a(f) of 10 CFR, "lnservice testing requirements," requires, in part, that IST of certair:i ASME Code Class 1, 2, and 3 pumps and valves be performed in accordance with the specified ASME OM Code and applicable addenda incorporated by reference in the regulations.

Exceptions are allowed where alternatives have been authorized by the NRG pursuant to paragraphs (z)(1) or (z)(2) of 10 CFR 50.55a. In proposing alternatives, the licensee must demonstrate that: (1) the proposed alternatives provide an acceptable level of quality and safety (10 CFR 50.55a(z)(1)), or (2) compliance would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety (10 CFR 50.55a(i)(2)).

Section 50.55a allows the NRC to authorize alternatives from ASME OM Code requirements upon making the necessary findings.

Enclosure

Based on the above, and subject to the following technical evaluation, the NRC staff finds that regulatory authority exists for the licensee to request and the Commission to authorize the alternative relief requested by the licensee.

3.0 TECHNICAL EVALUATION

3.1 Applicable ASME OM Code Edition and Addenda The third interval of the NMP2 IST program complies with the ASME OM Code of Nuclear Power Plants, 2004 Edition with no Addenda. The NMP2 third interval of the 10-year IST program interval began on January 1, 2009, and is scheduled to end on December 31, 2018.

3.2 ASME OM Code Requirements The licensee requested relief from Mandatory Appendix I, 1-1320, which requires that Class 1 pressure relief valves be tested at least once every 5 years with a minimum of 20 percent of the valves from each valve group tested within any 24-month interval. This 20 percent shall consist of valves that have not been tested during the current 5-year interval, if they exist. The test interval for any individual valve shall not exceed 5 years.

3.3 Component Identification Relief was requested for the following Unit 2 Class 1 main steam safety relief valves (SRVs):

2MSS*PSV120 2MSS*PSV121 2MSS*PSV122 2MSS*PSV123 2MSS*PSV124 2MSS*PSV125 2MSS*PSV126 2MSS*PSV127 2MSS*PSV128 2MSS*PSV129 2MSS*PSV130 2MSS*PSV131 2MSS*PSV132 2MSS*PSV133 2MSS*PSV134 2MSS*PSV135 2MSS*PSV136 2MSS*PSV137 3.4 Licensee's Basis for Requesting Relief The licensee stated in its application:

Section ISTC-3200, "lnservice Testing," states that inservice testing shall commence when the valves are required to be operable to fulfill their required function(s). Section ISTC-5240, Safety and Relief Valves, directs that safety and relief valves shall meet the inservice testing requirements set forth in Appendix I of the ASME OM Code. Appendix I, Section l-1320(a) of the ASME OM Code states that Class 1 pressure relief valves shall be tested at least once every 5 years, starting with initial electric power generation. This section also states a minimum of 20% of the pressure relief valves are tested within any 24-month interval and that the test interval for any individual valve shall not exceed 5 years.

The required tests ensure that the SRVs, which are located on each of the main steam lines between the reactor vessel and the first isolation valve within the drywell, will open at the pressures assumed in the safety analysis.

However, given the current 24-month operating cycle at NMP2, Exelon Generation Company, LLC (Exelon) is required to remove and test approximately half of the SRVs every refueling outage in order to ensure that all valves are removed and tested in accordance with the ASME OM Code requirements. This ensures compliance with the ASME OM Code requirements for testing Class 1 pressure relief valves within a 5 year interval. With the current 5 year interval, NMP2 is required to remove all 18 SRVs over 2 refuel cycles (i.e., 4 years).

Approval of extending the test interval to 6.5 years would reduce the number of SRVs removed during an individual outage, such that the full scope of 18 SRVs are replaced over 3 refuel cycles (i.e., 6 years, plus 6 months grace). Without Code relief, the incremental outage work due to the inclusion of the additional 2 - 3 SRVs per outage would be contrary to the principle of maintaining radiation dose As Low As Reasonably Achievable (ALARA). The removal and replacement of the additional 2 - 3 SRVs per outage without Code relief results in an additional exposure of approximately 2 - 4 Rem [roentgen equivalent man]

each outage. Additionally, the grace period allows for flexibility in the scheduling of as-left and as-found set-pressure testing, which is based on a test to test frequency.

The NRC staff previously authorized RR MSS-VR-01 for NMP2 to increase the SRV test interval from 5 years to 3 refueling cycles (approximately 6 years), but did not include the 6-month grace. Revision 1 of RR MSS-VR-01 would replace the currently approved test interval of 3 refueling cycles (approximately 6 years} with a test interval of 6 years, and would further allow a 6-month grace period for performing the tests. These revisions are consistent with the test interval and grace period described in ASME Code Case OMN-17. Due to outage scheduling, the additional 6 months is necessary to avoid unnecessary testing.

3.5 Licensee's Proposed Alternative Testing The licensee stated its application:

As an alternative to the Code required 5-year test interval per Appendix I, paragraph 1-1320(a), Exelon proposes that the subject Class 1 pressure relief valves be tested at least once every three refueling cycles (approximately 6 years/72 months) with a minimum of 20% of the valves tested within any 24-month interval. This 20% would consist of valves that have not been tested during the current 72-month interval, if they exist. The test interval for any individual valve would not exceed 72 months except that a 6-month grace period is allowed to coincide with refueling outages to accommodate extended shutdown periods and certification of the valve prior to installation.

As-found testing using steam and subsequent valve maintenance are currently performed at an off-site test facility. Subsequent to completion of as-found testing, each SRV in the removed complement is disassembled to perform inspections and a complete valve overhaul. Any SRV that failed the as-found set-pressure test is inspected to determine the cause of the test failure. Valve overhaul is performed to ensure that parts are free of defects resulting from time related degradation or service induced wear. All identified adverse conditions

are corrected, the disc and seats are lapped, and the valve is reassembled.

Each SRV is then recertified for service through inspection and testing consistent with ASME OM Code requirements, including set-pressure, seat tightness, stroke time and disc lift verifications, solenoid coil pick up/drop out, and air actuator integrity tests.

After recertification testing, the SRVs are stored at the test facility for future use.

The storage area is inspected and maintained to ANSl/ASME N45.2.2 requirements, which will minimize the potential for any valve degradation.

3.6 Staff Evaluation The NMP2 main steam SRVs are ASME Code Class 1 pressure relief valves that provide overpressure protection for the reactor coolant pressure boundary to prevent unacceptable radioactive release and exposure to plant personnel. ASME OM Code, Mandatory Appendix I requires that Class 1 pressure relief valves be tested at least once every 5 years. However, Mandatory Appendix I does not require that pressure relief valves be disassembled and inspected as part of the 5-year test requirement. In lieu of the 5-year test interval, the licensee proposed to implement requirements similar to ASME OM Code Case OMN-17, which allows a test interval of 6 years, plus a 6-month grace period. The ASME Committee on OM developed Code Case OMN-17 and published it in the 2009 Edition of the ASME OM Code. However, ASME OM Code Case OMN-17 imposes an additional special maintenance requirement to disassemble and inspect each pressure relief/safety valve to verify that parts are free from defects resulting from time-related degradation or service-induced wear coincident with each required test during the interval. The purpose of this maintenance requirement is to reduce the potential for pressure relief valve set-point drift.

ASME OM Code Case OMN-17 has not yet been added to Regulatory Guide 1.192, "Operation and Maintenance Code Case Acceptability, ASME OM Code," nor included in 10 CFR 50.55a by reference. However, the NRG has allowed licensees to use ASME OM Code Case OMN-17, provided all requirements in the Code Case are met. Consistent with the special maintenance requirement in ASME OM Code Case OMN-17, each main steam SRV at NMP2 will be disassembled and inspected to verify that internal surfaces and parts are free from defects or service induced wear prior to the start of the next test interval. This maintenance will also help to reduce the potential for set-point drift and increase the reliability of these SRVs to perform their design requirement functions. Consistent with the special maintenance requirement in ASME OM Code Case OMN-17, critical components will be inspected for wear and defects.

Additionally, the NRG staff review of recent set-point testing results shows that the SRV maintenance practices employed at NMP2 have been effective, as evidenced by no test failures over the last two refueling outage test cycles.

Based on the historical performance of the set-point testing of the main steam SRVs at NMP2 and disassembly and inspection of the main steam SRVs prior to use, the NRG staff finds that the proposed alternative test frequency for the testing of the main steam SRVs at NMP2, in lieu of the requirements of the 2004 Edition, no Addenda, Mandatory Appendix I, Section 1320, of the ASME OM Code, provides an acceptable level of quality and safety.

4.0 CONCLUSION

As set forth above, the NRC staff has determined that the proposed alternatives described in RR MSS-VR-01, Revision 1, provide an acceptable level of quality and safety for the NMP2 main steam SRVs. Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(z)(1) for RR MSS-VR-01, Revision 1, and is in compliance with the ASME OM Code requirements.

All other ASME OM Code requirements for which relief was not specifically requested and approved remain applicable.

Principal Contributor: John Billerbeck Date: January 29, 2016

B. Hanson If you have any questions concerning this matter, please contact the NMP2 Senior Project Manager, Mrs. Brenda Mozafari, at (301) 415-2020 or Brenda.Mozafari@nrc.gov.

Sincerely,

/RA/

Travis L. Tate, Chief Plant Licensing Branch 1-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-410

Enclosure:

Safety .Evaluation cc w/enclosure: Distribution via Listserv DISTRIBUTION:

PUBLIC CSantos, OEDO LPL 1-1 R/F RidsACRS_MailCTR Resource RidsNrrDorlLpl1-1 Resource RidsRgn1 MailCenter Resource RidsNrrLAKGoldstein Resource RidsNrrDeEpnb Resource RidsNrrPMNineMile Point Resource JBillerbeck, NRR ADAMS Access1on No.: ML15345A006 *b1y memo OFFICE DORL/LPLl-1/PM DORL/LPLl-1/LA DE/EPNB/BC* DORL/LPL 1-1/BC DORL/LPL 1-1/PM NAME BMozafari KGoldstein DAiiey TT ate BMozafari (LRonewicz for)

DATE 01/12/16 01/28/16 12/08/15 01/29/16 01/29/16 OFFICIAL RECORD COPY