ML090750923

Relief Request NDE-Leak Path, Proposed Alternative to ASME Code Case N-729-1 as Conditioned by 10 CFR 50.55(g)(6)(ii)(D)(3), Demonstrated Volumetric or Surface Leak Path Assessment for Spring 2009 Refueling Outage, ME0200

ML090750923
Person / Time
Site:	Diablo Canyon
Issue date:	04/08/2009
From:	Markley M Plant Licensing Branch IV
To:	Conway J Pacific Gas & Electric Co
Wang, A B, NRR/DORL/LPLIV, 415-1445
References
TAC ME0200
Download: ML090750923 (7)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 April 8, 2009 Mr. John 1. Conway Senior Vice President - Generation and Chief Nuclear Officer Pacific Gas and Electric Company Diablo Canyon Power Plant P.O. Box 3, Mail Code 104/6/601 Avila Beach, CA 93424

SUBJECT:

DIABLO CANYON POWER PLANT, UNIT NO.1 - APPROVAL OF REQUEST FOR RELIEF FROM 10 CFR 50.55a(g)(6)(ii)(D)(3) REQUIREMENT FOR DEMONSTRATED VOLUMETRIC LEAK PATH ASSESSMENT (TAC NO.

ME0200)

Dear Mr. Conway:

By letter dated December 4,2008, Pacific Gas and Electric Company (the licensee), requested U.S. Nuclear Regulatory Commission (NRC) authorization for relief, "NDE-Leak Path," from the requirements of Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(6)(ii)(D)(3) for the 2009 spring refueling outage at Diablo Canyon Power Plant (DCPP), Unit 1. The licensee requested relief from the requirement to perform an NRC-approved demonstrated volumetric leak path assessment of each reactor pressure vessel (RPV) upper head penetration nozzle.

The relief request proposes an alternative to use a previously NRC authorized volumetric leak path technique used under the requirements of the First Revised NRC Order EA-03-009, dated February 20, 2004, which was revoked by rulemaking dated September 10, 2008 (73 FR 52742). During a conference call on March 5, 2009, the NRC staff authorized the relief request verbally to allow the plant to start the RPV penetration inspections using the proposed alternative.

The NRC staff has completed its review of Relief Request NDE-Leak Path. The VOlumetric leak path assessment technique as described in the licensee's proposed alternative provides a best effort defense-in-depth inspection beyond the required bare metal visual inspection to identify leakage through each J-groove weld. Based on the enclosed safety evaluation (SE), the NRC staff determined that the proposed alternative provides reasonable assurance of structural integrity of the RPV upper head, and that compliance with the additional requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(ii), the NRC authorizes the use of the proposed alternative, NDE-Leak Path, for the spring 2009 refueling outage at DCPP, Unit 1.

All other requirements 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.

J. Conway -2 If you have any questions regarding the SE, please contact Alan B. Wang at (301) 415-1445.

Sincerely, bc-, \lO&\LL' tJ~ l,~~ ~ivl Michael T. Markley, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-275

Enclosure:

Safety Evaluation cc w/encl: Distribution via Listserv

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555*0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR RELIEF FROM 10 CFR 50.55A(G)(6)(II)(D)(3) REQUIREMENT RELIEF REQUEST NDE-LEAK PATH PACIFIC GAS AND ELECTRIC COMPANY DIABLO CANYON POWER PLANT, UNIT 1 DOCKET NO. 50-275

1.0 INTRODUCTION

By letter dated December 4, 2008 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML083440421), Pacific Gas and Electric Company (PG&E, the licensee), requested U.S. Nuclear Regulatory Commission (NRC) authorization for relief, "NDE-Leak Path," from the requirements of Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(6)(ii)(D)(3) for the 2009 spring refueling outage at Diablo Canyon Power Plant (DCPP) , Unit 1. PG&E requests relief from the requirement to perform an NRC-approved demonstrated volumetric leak path assessment of each reactor pressure vessel (RPV) upper head penetration nozzle. The relief request proposes an alternative to use a previously NRC authorized vOlumetric leak path technique used under the requirements of the First Revised NRC Order EA-03-009, dated February 20, 2004, which was revoked by rulemaking dated September 10, 2008 (73 FR 52742). During a conference call on March 5, 2009, the NRC staff authorized the relief request verbally to allow the plant to start the RPV penetration inspections using the proposed alternative.

2.0 REGULATORY EVALUATION

Paragraph 50.55a(g)(6)(ii) of 10 CFR states that the NRC may require the licensee to follow an augmented inservice inspection program for systems and components for which the NRC deems that added assurance of structural reliability is necessary. Under this section, 10 CFR 50.55a(g)(6)(ii)(D) defines the requirements for reactor vessel head inspections.

Paragraph 50.55a(a)(3) of 10 CFR states that alternatives to the requirements of paragraph (9) may be used, when authorized by the NRC if: (i) the proposed alternatives would provide an acceptable level of quality and safety, or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. The licensee, in accordance with 10 CFR 50.55a(a)(3)(ii),

has requested relief from the demonstrated volumetric leak path inspection requirements of 10 CFR 50.55a(g)(6)(ii)(D)(3).

Enclosure

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3.0 TECHNICAL EVALUATION

3.1 Component for Which Relief Was Requested American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code)

Class 1 vessel head penetration nozzles and associated welds (79 total) identified by item number B4.20 of Code Case N-729-1, "Alternative Examination Requirements for PWR

[Pressurized-Water Reactor] Reactor Vessel Upper Heads With Nozzles Having Pressure Retaining Partial-Penetration WeldsSection XI, Division 1 Supp 4," Table 1. The code of record for the third-1 0 year inservice inspection at DCPP, Unit 1 is the ASME Code,Section XI, 2001 Edition through the 2003 Addenda.

3.2 Regulatory Requirement Paragraph 50.55a(g)(6)(ii)(D)(3) of 10 CFR requires, in part, a licensee to perform a demonstrated volumetric or surface leak path assessment through all vessel head penetration nozzle J-groove welds as identified by Figure 2 of ASIVIE Code Case N-729-1.

3.3 Proposed Alternative The licensee's proposed alternative is to perform a volumetric leak path inspection using the same techniques used to satisfy the requirements of the First Revised NRC Order EA-03-009, dated February 20, 2004.

3.4 Licensee's Basis The licensee notes that while industry has initiated efforts to accomplish a generic demonstration of the volumetric leak path assessment technique, the extent of remaining tasks will likely preclude successful completion in time to support the upcoming spring 2009 refueling outage at DCPP, Unit 1. The licensee also states that performance of alternative surface examinations of each J-groove weld would be a significant hardship due to the personnel exposure associated with the inspections in a locked high radiation area and high contamination area without a compensating increase in the level of quality and safety. The licensee provided details on several enhancements to the volumetric leak path inspection technique which have been developed over the past 5 years, including the previously completed baseline inspection data available for assessment comparison.

3.5 NRC Staff Evaluation ASIVIE Code Case N-729-1 did not include a volumetric leak path assessment as part of the long-term re-inspection plans for RPV upper head penetration nozzles and their associated welds. The NRC staff believed this omission was, in part, due to the difficulty for ASME members to establish qualification requirements for this inspection technique. The NRC staff determined that surface examination of all associated penetration J-groove welds was necessary as a defense-in-depth approach to detect leakage through the J-groove weld.

The NRC staff presented this position in the proposed rule to mandate upper head inspections in accordance with ASME Code Case N-729-1. During the public comment

-3 period, several stakeholders noted hardships in performing this examination, and some stakeholders requested the option of performing a volumetric leak path assessment which would provide a similar defense-in-depth inspection to detect leakage through the J-groove weld. The NRC staff found that the stakeholder's request had merit and amended the final rule. However, due to the question regarding the effectiveness of the examination technique raised during the development of ASME Code Case N-729-1, the NRC staff included the requirement for a demonstrated volumetric leak path assessment in the final rule.

On November 24, 2008, the NRC staff held a public meeting with representatives from the Nuclear Energy Institute and industry to discuss generic activities going forward to demonstrate the volumetric leak path inspection technique. A meeting summary, dated February 24, 2009, with presentation slides is available under ADAMS Accession No. ML090560434. During the meeting, industry representatives provided a presentation on advances in the volumetric leak path assessment technique over the past 5 years. The industry described a living program being run by both major inspection vendors to ensure effective examinations were being performed. The industry representatives noted that recent concerns raised by the NRC Office of Nuclear Reactor Research contractors, including questions regarding the interpretation of signal data, were being incorporated into a generic standards document for use by inspectors in the field. The industry representatives explained that since baseline examinations have been performed on all RPV upper head penetration nozzles throughout the U.S. PWR fleet, that there would be significant enhancements in analyzing future inspection results. The industry representatives also stated their intention to provide details of each of these enhancements to the NRC in a guideline in the spring of 2009 and that this information was already being put into use by vendors in the field. Further, industry representatives discussed activities to complete an industry generic demonstration of the volumetric leak path technique, but they did not expect to complete the project in time to support the spring 2009 outage at DCPP, Unit 1.

Surface examination of the entire wetted surface of each J-groove weld is an option for the licensee under the requirements of 10 CFR 50.55a(g)(6)(ii)(D)(3). However, the licensee has provided sufficient plant-specific information regarding weld surface condition and personnel radiological dose exposure for the NRC staff to conclude that compliance with these provisions by performing a surface examination constitutes a hardship upon the licensee. Given the delay in implementation of a generic demonstration of the volumetric leak path technique, the NRC staff finds that the previously NRC authorized volumetric leak path assessment technique, as described in the licensee's proposed alternative, when combined with the required bare metal visual examination provides a best effort defense-in depth inspection to identify leakage through each J-groove weld. Thus, the NRC staff concludes that the licensee's proposed alternative provides reasonable assurance of structural integrity of the RPV upper head, and compliance with the additional requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

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4.0 CONCLUSION

The NRC staff has reviewed the licensee's basis and concludes that the licensee's proposed alternative provides reasonable assurance of structural integrity of the RPV upper head, and that compliance with the additional requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

Therefore, in accordance with 10 CFR 50.55a(a)(3)(ii) the NRC authorizes the licensee's proposed alternative, NDE-Leak Path, for the spring 2009 refueling outage at DCPP, Unit 1.

All other requirements 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.

Principal Contributor: J. Collins Date: Apr i 1 8, 2009

J. Conway -2 If you have any questions regarding the SE, please contact Alan B. Wang at (301) 415-1445.

Sincerely, IRA!

Michael 1. Markley, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-275

Enclosure:

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(*) Concurrence via SE OFFICE NRR/LPL4/PM NRR/LPL4/LA DCI/CPNB/BC OGC NRR/LPL4/BC NRR/LPL4/PM MMarkley BSingal NAME AWang JBurkhardt TChan (*) MSmith for AWang JHall for DATE 3/20109 3/19/09 3/16/09 3/27/09 j.4JaJo9 1 4/ 8/09 I

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