ML20212L390

Proposed Alternative I4r-03 to the Requirements of the Asme Code (Epid L-2019-Llr-0114)

ML20212L390
Person / Time
Site:	Clinton
Issue date:	08/31/2020
From:	Nancy Salgado, Joel Wiebe Plant Licensing Branch III
To:	Bryan Hanson Exelon Generation Co, Exelon Nuclear
Wiebe J S-NRR/DORL 301-415-6606
References
EPID L-2019-LLR-0114
Download: ML20212L390 (7)

Text

August 31, 2020 Mr. Bryan C. Hanson Senior Vice President Exelon Generation Company, LLC President and Chief Nuclear Officer (CNO)

Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555

SUBJECT:

CLINTON POWER STATION, UNIT 1 - PROPOSED ALTERNATIVE I4R-03 TO THE REQUIREMENTS OF THE ASME CODE (EPID L-2019-LLR-0114)

Dear Mr. Hanson:

By letter dated December 16, 2019 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML19350C642), Exelon Generation Company, LLC (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 Boiler and Pressure Vessel Code (ASME Code),Section XI, requirements at Clinton Power Station (CPS), Unit 1 Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(2), the licensee requested to use alternative I4R-031 on the basis that complying with the specified requirement would result in hardship or unusual difficulty. Performing system leakage tests as required by the ASME Code would require applying a leak detection solution to a large amount of piping and components, many of which are in elevated dose rate areas with limited access.

The NRC staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that that the proposed alternative provides reasonable assurance of structural integrity and leak tightness of the subject components at CPS. The NRC staff finds that complying with the requirements of ASME Code,Section XI, 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 of the regulatory requirements set forth in 10 CFR 50.55a(z)(2). Therefore, the NRC authorizes the use of alternative I4R-03 at CPS for the fourth 10-year inservice inspection interval, which is currently scheduled to begin on July 1, 2020, and end June 30, 2030.

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

1 The other requests contained in the licensees December 16, 2019, letter have been or will be addressed by separate correspondence.

B. Hanson If you have any questions, please contact the Senior Project Manager, Joel S. Wiebe, at (301) 415-6606 or Joel.Wiebe@nrc.gov.

Sincerely, Digitally signed by Nancy L. Nancy L. Salgado Date: 2020.08.31 Salgado 12:38:59 -04'00' Nancy L. Salgado, Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-461

Enclosure:

Safety Evaluation cc: ListServ

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PROPOSED ALTERNATIVE I4R-03 REGARDING SYSTEM LEAKAGE TEST REQUIREMENTS FOR CERTAIN CLASS 2 AND CLASS 3 PIPING AND VALVES EXELON GENERATION COMPANY, LLC CLINTON POWER STATION, UNIT 1 DOCKET NO. 50-461

1.0 INTRODUCTION

By letter dated December 16, 2019 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML19350C642), Exelon Generation Company, LLC (EGC, the licensee), submitted relief request (RR) I4R-03 to the U.S. Nuclear Regulatory Commission (NRC) for use of an alternative to the requirements of the American Society of Mechanical Engineers Boiler & Pressure Vessel Code (ASME Code),Section XI, IWC-5220 and IWD-5220, for the fourth 10-year inservice inspection (ISI) interval at Clinton Power Station (CPS), Unit 1.

Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(2), the licensee submitted RR I4R-03 to allow alternative system leakage testing of various ASME Code Class 2 and Class 3 piping and valves on the basis that complying with the specified ASME Code requirements would result in hardship or unusual difficulty, without a compensating increase in the level of quality and safety.

2.0 REGULATORY EVALUATION

Pursuant to 10 CFR 50.55a(g)(4), the ASME Code Class 1, 2, and 3 components (including supports) must meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, to the extent practical within the limitations of design, geometry, and materials of construction of the components.

Pursuant to 10 CFR 50.55a(z), alternatives to the requirements of paragraph (g) of 10 CFR 50.55a 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 licensee must demonstrate: (1) the proposed alternative would provide an acceptable level of quality and safety; or (2) 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.

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 NRC to authorize, the alternative requested by the licensee.

3.0 TECHNICAL EVALUATION

3.1 Component Affected The licensee identified the affected piping segments as all Class 2 instrument air piping and components between containment isolation valves; Class 3 instrument air piping and components supplying to all safety relief valves (SRVs) and both feedwater containment outboard isolation check valves.

The components affected are classified by the ASME Code as follows, ASME Code Class 2 piping. In accordance with IWC-2500 (Table IWC-2500-1), they are classified as Examination Category C-H, Item No. C7.10.

ASME Code Class 3 piping. In accordance with IWD-2500 (Table IWD-2500-1), they are classified as Examination Category D-B, Item No. D2.10.

3.2 Applicable Code Edition and Addenda The Code of record for the fourth 10-year ISI interval is the 2013 Edition of the ASME Code,Section XI.

3.3 Duration of Relief Request The licensee submitted RR I4R-03 for the fourth 10-year ISI interval which began on July 1, 2020, and will end on June 30, 2030.

3.4 ASME Code Requirement The ASME Code,Section XI, IWC-2500, Table IWC-2500-1, Examination Category C-H, Item No. C7.10, requires all Class 2 pressure-retaining components be subject to a system leakage test with a VT-2 visual examination in accordance with paragraph IWC-5220. This pressure test is to be conducted once each inspection period.

The ASME Code,Section XI, IWD-2500, Table IWD-2500-1, Examination Category D-B, Item No. D2.10, requires all Class 3 pressure-retaining components be subject to a system leakage test with a VT-2 visual examination in accordance with paragraph IWD-5220. This pressure test is to be conducted once each inspection period.

3.5 Proposed Alternative, Basis for Use, and Reason for Relief Relief is requested from performance of system leakage tests and VT-2 visual examinations specified in Tables IWC-2500-1 and IWD-2500-1 for all Class 2 and Class 3 instrument air pressure retaining components in accordance with paragraphs IWC-5220 and IWD-5220, respectively.

In lieu of the system leakage tests, pressure decay testing is performed in accordance with CPS procedures. In its December 19, 2019, letter, the licensee states that the pressure decay test is performed by isolating and pressurizing these accumulators and associated piping and components to the nominal operating pressure. The decay in pressure is then monitored through calibrated pressure measuring instrumentation. If any pressure decay acceptance criterion is exceeded, the surveillance procedure identifies appropriate troubleshooting steps, including soap-bubble application, to locate leakage.

In its letter dated December 19, 2019, the licensee states that this pressure decay testing is performed at a greater frequency than that required in Tables IWC-2500-1 or IWD-2500-1, and the test pressure is consistent with the pressure requirements in both tables. Thus, the testing performed during this surveillance will provide the same level of quality and safety as the pressure test and VT-2 visual examination requirements of Tables IWC-2500-1 and IWD-2500-1. The licensee states that performing system leakage tests, as required by Tables IWC-2500-1 and IWD-2500-1, would require applying a leak detection solution to a large amount of piping and components, many of which are in elevated dose rate areas with limited access.

In summary, the licensee stated that performing system leakage tests, as required by Tables IWC-2500-1 and IWD-2500-1, would result in a hardship without a compensating increase in quality and safety. The proposed alternative provides reasonable assurance of operational readiness of the subject components.

3.6 NRC Staff Evaluation The ASME Code,Section XI, IWC-2500, Table IWC-2500-1, Examination Category C-H, Item No. C7.10, requires a system leakage test be performed with a VT-2 visual examination in accordance with paragraph IWC-5220. This pressure test is to be conducted once each inspection period.

The ASME Code,Section XI, IWD-2500, Table IWD-2500-1, Examination Category D-B, Item No. D2.10, requires a system leakage test be performed with a VT-2 visual examination in accordance with paragraph IWC-5220. This pressure test is to be conducted once each inspection period.

The NRC staff notes that the ASME Code,Section XI, requires a system leakage test of all pressure retaining components in the automatic depressurization system (ADS) and the SRV accumulators including the associated piping once every 40 months and a VT-2 visual examination during the system leakage test to detect evidence of leakage. The ASME Code further states that the contained fluid in the system which is air shall serve as the pressurizing medium. Therefore, soap solution is applied to the surface of the component to detect any evidence of leakage. As an alternative, the licensee proposed to take credit for the technical specifications (TSs) surveillance performed which states that each ADS SRV shall be determined operable automatically and manually at a 24-month frequency. In addition, the TSs require that these valves are to be surveillance tested in accordance with the inservice testing program during each refueling outage.

The NRC staff considers this leakage criterion based on pressure decay to be an acceptable alternative to the ASME Code-required VT-2 visual examination of the pressure boundary. The ASME Code,Section XI, allows rate of pressure loss as an alternative to the VT-2 visual examination during system leakage test of buried components that are isolable by means of

valves. The NRC staff notes that pressure decay provides an adequate assurance of leak-tight integrity of the components during the surveillance. In addition, the proposed alternative offers further conservatism because the surveillance frequency is once every 24 months as opposed to the ASME Code requirement frequency of once every 40 months.

The NRC staff finds that performing the system leakage tests with visual examinations in accordance with paragraphs IWC-5220 and IWD-5220 would result in a hardship due to the excessive radiation exposure. In addition, performing the tests at elevated temperatures would present safety concerns to personnel performing the visual examination.

Based on the above, the NRC staff finds that the licensees proposed alternative provides reasonable assurance of structural integrity and that compliance to ASME Code requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

4.0 CONCLUSION

As set forth above, the NRC staff determines that the proposed alternative provides reasonable assurance of structural integrity and leak tightness of the subject components, and that complying with the specified ASME 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 use of the licensees proposed alternative I4R-03 at CPS, Unit 1, for the fourth 10-year ISI interval which will end on June 30, 2030.

All other ASME Code,Section XI, requirements for which relief was not specifically requested and authorized herein by the NRC staff remain applicable, including the third-party review by the Authorized Nuclear In-service Inspector.

Principal contributor: B. Fu Date: August 31, 2020

ML20212L390 *via email OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA* NRR/DNRL/NPHP/BC* NRR/DORL/LPL3/BC*

NAME JWiebe SRohrer MMitchell NSalgado DATE 7/30/2020 7/30/2020 7/2/2020 8/31/2020