ML19217A324

Relief Request MC-SRV-NC-03, Alternate Testing for Pressurizer Power Operated Relief Valve Block Valve 2NC-35B

ML19217A324
Person / Time
Site:	Mcguire, McGuire
Issue date:	08/14/2019
From:	Markley M Plant Licensing Branch II
To:	Teresa Ray Duke Energy Carolinas
Mahoney M, NRR/DORL/LPL2-1, 415-3867
References
EPID L-2019-LLR-0067
Download: ML19217A324 (7)

Text

August 14, 2019 Mr. Thomas D. Ray Site Vice President Duke Energy Carolinas, LLC McGuire Nuclear Station 12700 Hagers Ferry Road Huntersville, NC 28078-8985

SUBJECT:

MCGUIRE NUCLEAR STATION, UNIT 2 - RELIEF REQUEST MC-SRV-NC-03, ALTERNATE TESTING FOR PRESSURIZER POWER OPERATED RELIEF VALVE BLOCK VALVE 2NC-35B (EPID NO. L-2019-LLR-0067)

Dear Mr. Ray:

By letter dated July 17, 2019, Duke Energy Carolinas, LLC (Duke Energy, the licensee) submitted relief request MC-SRV-NC-03 to the U.S. Nuclear Regulatory Commission (NRC) for certain American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code) requirements at McGuire Nuclear Station (McGuire), Unit 2.

The licensee requested an alternative test plan in lieu of certain inservice testing (IST) requirements of the 2004 Edition through 2006 Addenda of the ASME OM Code for the IST program at McGuire, Unit 2, during the fourth 10-year IST program interval for pressurizer power operated relief valve block valve, 2NC-35B. Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(2), the licensee requested to use an alternative on the basis that complying with the specified requirement would result in hardship or unusual difficulty.

The NRC staff determined that the proposed alternative provides reasonable assurance that valve 2NC-35B is operationally ready, and that compliance with the ASME OM Code requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Accordingly, the NRC staff concludes that the licensee has adequately addressed all the regulatory requirements set forth in 10 CFR 50.55a(a)(z)(2).

Therefore, the NRC staff authorizes the McGuire, Unit 2 proposed alternative request until valve 2NC-35B is repaired during the next refueling outage which is currently scheduled to begin on March 21, 2020.

All other ASME OM Code requirements for which relief was not specifically requested and authorized by the NRC remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.

T. Ray If you have any questions, please contact the Project Manager, Michael Mahoney at 301-415-3867 or via e-mail at Michael.Mahoney@nrc.gov.

Sincerely,

/RA/

Michael T. Markley, Chief Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-370

Enclosure:

Safety Evaluation cc w/encl: Distribution via ListServ

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ALTERNATIVE REQUEST MC-SRV-NC-03 RELATED TO THE INSERVICE TESTING PROGRAM FOURTH 10-YEAR INTERVAL DUKE ENERGY CAROLINAS, LLC MCGUIRE NUCLEAR STATION, UNIT 2 DOCKET NUMBER 50-370

1.0 INTRODUCTION

By letter dated July 17, 2019 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML19204A116), Duke Energy Carolinas, LLC (Duke Energy, the licensee) submitted relief request MC-SRV-NC-03 to the U.S. Nuclear Regulatory Commission (NRC) for certain American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code) requirements at the McGuire Nuclear Station (McGuire), Unit 2.

The licensee requested an alternative test plan in lieu of certain inservice testing (IST) requirements of the 2004 Edition through 2006 Addenda of the ASME OM Code for the IST program at McGuire, Unit 2, during the fourth 10-year IST program interval for pressurizer power operated relief valve (PORV) block valve, 2NC-35B.

Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(2), the licensee requested to use an alternative on the basis that complying with the specified requirement would result in hardship or unusual difficulty.

2.0 REGULATORY EVALUATION

The regulations in 10 CFR 50.55a(f), "Inservice Testing Requirements," require, in part, that IST of certain ASME Code Class 1, 2, and 3 components must meet the requirements of the ASME OM Code and applicable addenda, except where alternatives have been authorized pursuant to paragraphs 10 CFR 50.55a(z)(1) or 10 CFR 50.55a(z)(2).

In proposing alternatives, a licensee must demonstrate that the proposed alternatives provide an acceptable level of quality and safety (10 CFR 50.55a(z)(1)) or compliance would result in Enclosure

hardship or unusual difficulty without a compensating increase in the level of quality and safety (10 CFR 50.55a(z)(2)).

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 requested by the licensee.

3.0 TECHNICAL EVALUATION

3.1.1 Licensees Alternative Request MC-SRV-NC-03 ASME OM Code Requirements:

The 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, except as provided by ISTC-3520, ISTC-3540, ISTC-3550, ISTC-3570, ISTC-5221, and ISTC-5222.

Alternative testing is requested for the following valve:

Valve ID Description Category Class 2NC-35B pressurizer PORV block valve B 1 In its letter dated July 17, 2019, the licensee states, in part, that:

Reason for Request

Nuclear Condition Report (NCR) 02275540 was initiated by Engineering on June 4, 2019 due to an increasing trend in identified reactor coolant system (RCS) leakage between May 27, 2019 and June 9, 2019. The May 27, 2019 corrected identified RCS leakage value was 0.055 GPM [gallons per minute] and gradually increased to 0.23 GPM by June 9, 2019. Technical Specification (TS) 3.4.13 limits RCS identified leakage to a maximum of 10 GPM. A containment entry was made on June 8, 2019 to investigate the source of identified RCS leakage. The investigation determined the leakage source to be from the common PORV block valve stem leak off line. A troubleshooting plan was developed and 2NC-35B was stroked closed on June 10, 2019 resulting in a significant decrease in RCS identified leakage. From June 10, 2019 to June 18, 2019, RCS identified leakage remained low with 2NC-35B in the closed position.

Stroking 2NC-35B can create a hardship as further packing degradation may result, reducing operational RCS leakage margin. Current RCS leakage values are stable with 2NC-35B closed and the remaining two PORV block valves 2NC-31B and 2NC-33A open. 2NC-35B remains operable with emergency power available.

Based on current plant conditions and as described in the proposed alternative basis, Duke Energy is requesting relief from ASME Code quarterly valve surveillances to prevent quarterly valve cycles until valve repair can be made during the next Unit 2 refueling outage, which is currently scheduled to begin on March 21, 2020.

Repair of 2NC-35B would require entry into containment and RCS depressurization for isolation purposes. Personnel safety and ALARA [as low as reasonably

achievable] practices are maximized during a scheduled refueling outage.

Additionally, maneuvering the reactor to a mode outside of TS applicability and depressurizing the RCS involves inherent risk and increases nuclear safety risk due to cycling plant equipment.

Proposed Alternative and Basis for Use As an alternative to performing quarterly surveillance testing on 2NC-35B, Duke Energy is requesting to defer exercise and valve stroke timing testing for the remainder of the current Unit 2 fuel cycle. In the event of PORV block valve packing leakage, stroking the respective valve creates a hardship because of the increased potential for packing leakage. Increased leakage reduces the margin for acceptable reactor coolant system identified leakage (Reference TS 3.4.13, Operational Leakage). If RCS identified leakage exceeds its allowable limit, the required action is plant shutdown. All other PORV block valves will continue to be stroked quarterly per applicable ASME code requirements.

As stated in Section 5, to control stem packing leakage on 2NC-35B, the valve was manually closed, with emergency power available. Operational valve stroke timing testing was conducted on June 10, 2019 in both the closed and open directions with satisfactory results. This testing demonstrates the valve is fully operationally ready to open in the current configuration.

When the valve is closed due to valve packing leakage, the valve is administratively maintained closed with emergency power available. If required to be opened to perform its intended safety function, the valve is opened by the control room operator. Opening the valve with a packing leak during normal plant operation may cause further stem packing damage, resulting in increased RCS leakage.

PORV block valves have established preventative maintenance activities. The valves have maintained consistent performance with no adverse trends or abnormalities noted during Motor Operated Valve diagnostic testing. The valve actuator general and lubrication condition is of sufficient quality to support continued reliability with the relief of quarterly exercise and stroke timing activities until scheduled repairs.

lnservice Testing (IST) performance history of McGuire Unit 1 and Unit 2 PORV block valves has been excellent with no valve stroke timing or position indication testing failures from reviewed data January 1, 2009 to present. 2NC-35B valve stroke timing performance (open and closed directions) has been consistently between 5.5 and 6.0 seconds, demonstrating acceptable margin to the maximum limit of 10 seconds.

Duration of Proposed Alternative This condition is only intended to permit McGuire Unit 2 operation for a limited period of time not to exceed restart from the next refueling outage. 2NC-35B repair is planned for the next McGuire Unit 2 refueling outage M2R26 scheduled to begin on March 21, 2020. Following the refueling outage, Duke Energy will resume quarterly testing of 2NC-35B per applicable ASME Code requirements.

3.1.2 NRC Staff Evaluation The ASME OM Code requirement ISTC-3510 requires that active Category A and B valves be exercised nominally every 3 months. In addition, the Code specifies that if the exercise tests are not practicable to perform during power operation the test may be deferred to either cold shutdowns or refueling outages.

The licensee had been exercising valve 2NC-35B nominally every 3 months. IST performance history has been excellent with no issues. Recently, there has been a noted increase in RCS leakage due to faulty packing of the pressurizer block valve 2NC-35B. Continued operation in the normally open position would challenge TS RCS leakage acceptance criteria. To avoid an unnecessary RCS depressurization, 2NC-35B was placed in the closed position to stop the leakage, with emergency power available. RCS leakage was confirmed to return to acceptable levels. Prior to keeping 2NC-35B in the closed position, it was operationally tested in both the open and closed directions with satisfactory results demonstrating that the valve is operationally ready. Continuation with the quarterly exercise stroke testing could result in an increase in packing degradation and lead to an unnecessary plant shutdown. This represents a hardship or unusual difficulty without a compensating increase in the level of quality or safety.

The licensee proposes to maintain the valve current configuration with valve 2NC-35B in the closed position with emergency power available. If required to be opened to perform its intended safety function, the valve will be opened by the control room operator. This configuration will be maintained until maintenance can be performed at the next refueling outage currently scheduled to begin on March 21, 2020. The NRC staff finds that the proposed alternative provides reasonable assurance that the components are operationally ready.

The NRC approved a similar relief request for the Unit 2, PORV block valve 2NC-35B on October 20, 2016 (ADAMS Accession No. ML16291A303).

4.0 CONCLUSION

The NRC staff has concluded that the proposed alternative provides reasonable assurance that PORV Block Valve 2NC-35B is operationally ready, and that compliance with the ASME OM Code requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Accordingly, the NRC staff concludes that the licensee has adequately addressed all the regulatory requirements set forth in 10 CFR 50.55a(z)(2).

Therefore, the NRC staff authorizes the licensees relief request MC-SRV-NC-03 for McGuire, Unit 2, proposed alternative request until PORV Block Valve 2NC-35B is repaired during the next McGuire, Unit 2 refueling outage which is currently scheduled to begin on March 21, 2020.

All other ASME OM Code requirements for which relief was not specifically requested and approved remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.

Principal Contributor: Michael F. Farnan, NRR Date: August 14, 2019

ML19217A324 *By Memorandum +By Email OFFICE NRR/DORL/LPL2-1/PM NRR/DORL/LA NRR/DORL/LPL2-1/LA NAME MMahoney KEntz KGoldstein+

DATE 08/09/19 08/07/19 08/09/2019 OFFICE NRR/DE/EMIB/BC NRR/DORL/LPL2-1/BC NAME SBailey* MMarkley DATE 07/24/19 08/14/19