ML20076J372

Summary of NRC Verbal Authorization (E-mail Dated 3/16/2020) Alternative Request IR-4-03 for Use of Alternative Non-Code Methodology:

ML20076J372
Person / Time
Site:	Millstone
Issue date:	03/16/2020
From:	Richard Guzman NRC/NRR/DORL/LPL1
To:	Sinha S Dominion Energy Nuclear Connecticut
Guzman R
References
EPID L-2020-LLR-0038
Download: ML20076J372 (3)

Text

From: Guzman, Richard To: Shayan.Sinha@dominionenergy.com

Subject:

Millstone Power Station, Unit 3 - Alternative Request IR-4-03 For Use of an Alternative Non-Code Methodology to Demonstrate Structural Integrity:

SUMMARY

OF NRC STAFF VERBAL AUTHORIZATION [EPID: L-2020-LLR-0038]

Date: Monday, March 16, 2020 6:59:57 PM

Shayan, Effective today, March 16, 2020, and as discussed in todays 6:30 pm call, the NRC staff communicated its verbal authorization of Dominion Energy Nuclear Connecticut, Inc.s (DENC, the licensee) Alternative Request No. IR-4-03, submitted by DENC letter dated March 14, 2020, as supplemented by two e-mail transmittals both dated March 16, 2020, for Millstone Power Station, Unit 3 (Millstone 3). The alternative request proposed to use a non-code methodology in lieu of repair allowed by the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, IWA-4000, in order to address a through-wall leak in a reinforced branch connection of the Millstone 3 A train service water piping header.

Please see below transcript of the NRC staffs verbal authorization. This e-mail will be added to ADAMS as a publicly available official agency record, documenting the staffs aforementioned approval. The NRC staffs formal safety evaluation will be transmitted via separate correspondence. Please contact me if you have any questions regarding this licensing action.

Rich Guzman Sr. PM, Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Office: O-9C7 l Phone: (301) 415-1030 Richard.Guzman@nrc.gov VERBAL AUTHORIZATION BY THE OFFICE NUCLEAR REGULATION 10 CFR 50.55a REQUEST TO USE A NON-CODE ALTERNATIVE NON-CODE METHODOLOGY TO DEMONSTRATE STRUCTURAL INTEGRITY OF CLASS 3 MODERATE ENERGY PIPING MILLSTONE POWER STATION, UNIT 3 DOMINION ENERGY NUCLEAR CONNETICUT, INC.

DOCKET NO. 50-423 MARCH 16, 2020 Technical Evaluation read by Matthew Mitchell, Chief of the Piping and Head Penetration Branch, Office of Nuclear Reactor Regulation By letter dated March 14, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20076A549), as supplemented by two e-mail transmittals on March 16, 2020 (ML20076C833 and ML20076F300), Dominion Energy Nuclear Connecticut, Inc. (the licensee), proposed an alternative to the requirements of the

American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, paragraph IWD-3132 and article IWD-3400, for Millstone Power Station, Unit 3 (Millstone Unit 3).

Pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(2), the licensee submitted Alternative Request, IR-4-03, requesting NRC approval of a proposed alternative to demonstrate that moderate-energy (i.e., = 200°F (93°C) and = 275 psig (1.9 Mpa) maximum operating conditions) service water (SW) system piping, line designation, 3-SWP-19-2-7-3 is operable without repair or replacement in accordance with the ASME Code,Section XI. The licensee has concluded that complying with the specified ASME Code requirement to repair or replace the SW system piping would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety, noting that unnecessary plant shutdown activities result in additional plant risk. The licensee requested approval of the proposed alternative until no later than the Millstone Unit 3 refueling outage scheduled for October 2020, or until such time that leakage exceeds the maximum acceptable leakage rate of 5 gallons per minute (gpm), or ultrasonic testing (UT) examinations determine that the licensees structural integrity analysis is no longer bounding.

On March 11, 2020, the licensee discovered water dripping from a weep hole in a reinforcing pad (also referred to as a branch reinforcement by the ASME Code, or as a saddle plate in Attachment 2 of the licensees March 14, 2020, submittal) on a 30-inch diameter section of SW supply piping (i.e., 3-SWP-19-2-7-3) in the 'A' SW train at Millstone Unit 3. Water was observed to be leaking at a rate of about 1 drop every 40 seconds with one 'A' header SW pump running, or 1 drop every 20 seconds with both 'A' header SW pumps running. The upper reinforcing pad is fillet welded to the intersection of two 30-inch diameter pipes to provide structural support for the piping joint. The reinforcing pad is 60 inches long and 0.75-inch thick with a 69.75-degree arc rolled to a 30-inch inside diameter.

The presence of the reinforcing pad precluded identifying and characterizing the flaw in the underlying piping as required by ASME Code,Section XI.

The licensee performed a structural evaluation based on loads at the location up to and including safe shutdown earthquake conditions. Thermal and deadweight load stresses are approximately 50% of the ASME Code allowable stresses. The licensee performed visual and UT examinations of the location, as documented in its March 14, 2020 submittal, as supplemented by the information provided in the licensees March 16, 2020 e-mail supplements, which substantiated that the current material condition is consistent with the assumptions in the licensees structural evaluation. The licensees structural evaluation demonstrated significant margin for the fillet welds and reinforcing pad. The piping analysis shows that the reinforcing pads are well supported in the vicinity, and isolated from vibrations. The staff found the licensees structural evaluation to be acceptable and that the results showed significant margins for short term operability when combined with leakage monitoring measures.

The licensee proposed to monitor and record the leak rates at the location daily and to implement a 5 gpm limit as the maximum allowable leakage indicative of maintaining structural integrity. In addition, the licensee will perform periodic UT examinations on the degraded piping system adjacent to and under the reinforcement fillet weld pad and reinforcing pad base metal to ensure that the material condition of these locations remain within the bounds of the structural integrity evaluation provided in Attachment 2 of the licensees March 14, 2020 submittal as clarified by the information provided in the licensees March 16, 2020 supplements.

Based on the results of the information provided above, the NRC staff finds that (1) there is adequate margin in the structural integrity evaluation of the subject location in the SW system piping in the A SW train at Millstone Unit 3, (2) the leak rate from the existing flaw is less than the allowable leak rate, thus, the SW supply piping in the A SW train is capable of performing its intended function, (3) the licensees performance of daily monitoring and leak rate recording with a maximum acceptable leak rate of 5 gpm is acceptable as an indicator of the ongoing structural integrity of the location, (4) the licensees performance of UT of the degraded piping area every 30 days +/- 25% unless the leak rate increases to 100 drops per minute prior to the previous 7 days is also acceptable for monitoring the ongoing structural integrity of the location, and (5) the licensees hardship justification is acceptable.

The NRC finds that the proposed alternative will provide reasonable assurance that the structural integrity will be maintained until the next scheduled refueling outage in October 2020 when an ASME Code repair will be performed. If the observed leak rate or the UT examination results exceed the limits cited in the licensees March 14, 2020 submittal and March 16, 2020 supplements, the basis for the licensees alternative will no longer hold and an ASME Code repair shall be performed.

Authorization read by James Danna, Chief of the Plant Licensing Branch I, Office of Nuclear Reactor Regulation As Chief of the Plant Licensing Branch I, Office of Nuclear Reactor Regulation, I agree with the conclusions of the Piping and Head Penetration Branch.

The NRC staff concludes that the proposed alternative will provide reasonable assurance that the structural integrity will be maintained until the next scheduled refueling outage in October 2020 when an ASME Code repair will be performed. The NRC staff finds that complying with the requirements of the 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, effective March 16, 2020, the NRC authorizes the use of the proposed alternative IR-4-03, at Millstone Unit 3, until completion of the next scheduled refueling outage, scheduled for October 2020.

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

This verbal authorization does not preclude the NRC staff from asking additional clarification questions regarding the proposed alternative while subsequently preparing the written safety evaluation.