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R. E. Ginna Nuclear Power Plant - Issuance of Relief Request Associated with Alternative I6R-01 for the Sixth 10-Year Inservice Inspection Interval
	ML20055F886
Person / Time
Site:	Ginna
Issue date:	03/13/2020
From:	James Danna; Plant Licensing Branch 1
To:	Bryan Hanson; Exelon Generation Co
	Sreenivas V, NRR/DORL/LPL1, 415-2596
References
	EPID L-2019-LLR-0070
	Download: ML20055F886 (7)
	v • d • e

March 13, 2020 Mr. Bryan C. Hanson Senior Vice President Exelon Generation Company, LLC President and Chief Nuclear Officer Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555

SUBJECT:

R. E. GINNA NUCLEAR POWER PLANT - ISSUANCE OF RELIEF REQUEST ASSOCIATED WITH ALTERNATIVE I6R-01 FOR THE SIXTH 10-YEAR INSERVICE INSPECTION INTERVAL (EPID L-2019-LLR-0070)

Dear Mr. Hanson:

By letter dated June 27, 2019 (Agencywide Documents Access and Management System Accession No. ML19178A013), Exelon Generation Company, LLC (the licensee) requested relief from the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel (ASME) Code Case N-722-1, Visual Examinations for PWR [Pressurized Water Reactor] Pressure Retaining Welds in Class 1 Components Fabricated with Alloy 600/82/182 MaterialsSection XI, Division 1, at the R. E. Ginna Nuclear Power Plant (Ginna).

Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(1), the licensee proposed an alternative, I6R-01, regarding the bare-metal visual examinations of the Ginna reactor pressure vessel bottom mounted instrument penetration nozzles on the basis that the alternative provides an acceptable level of quality and safety.

The U.S. Nuclear Regulatory Commission (NRC) staff has determined that the licensees proposed alternative provides an acceptable 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)(1). Therefore, the NRC staff authorizes the use of the licensees proposed alternative I6R-01 at Ginna, for the duration of the sixth 10-year inservice inspection program interval, which began on January 1, 2020, and is scheduled to end on December 31, 2029.

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

If you have any questions, please contact the Ginna Project Manager, V. Sreenivas, at 301-415-2597 or V.Sreenivas@nrc.gov.

Sincerely,

/RA/

James G. Danna, Chief Plant Licensing Branch I Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-244

Enclosure:

Safety Evaluation cc: Listserv

Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST I6R-01 FOR SIXTH 10-YEAR INSERVICE INSPECTION INTERVAL EXELON GENERATION COMPANY, LLC R. E. GINNA NUCLEAR POWER PLANT DOCKET NO. 50-244

1.0 INTRODUCTION

By letter dated June 27, 2019 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML19178A013), Exelon Generation Company, LLC (Exelon or the licensee) requested relief from the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel (ASME) Code Case N-722-1, Visual Examinations for PWR [Pressurized Water Reactor] Pressure Retaining Welds in Class 1 Components Fabricated with Alloy 600/82/182 MaterialsSection XI, Division 1, at the R. E. Ginna Nuclear Power Plant (Ginna).

Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(1), the licensee proposed an alternative, I6R-01, regarding the bare-metal visual examinations of the Ginna reactor pressure vessel (RPV) bottom mounted instrument (BMI) penetration nozzles on the basis that the alternative provides an acceptable level of quality and safety.

2.0 REGULATORY EVALUATION

Pursuant to 10 CFR 50.55a(g)(6)(ii)(E), all licensees of PWRs must augment their inservice inspection (ISI) program by implementing ASME Code Case N-722-1 subject to the conditions specified in paragraphs (g)(6)(ii)(E)(2) through (4) of 10 CFR 50.55a. ASME Code Case N-722-1 requires that the licensee perform a bare-metal visual examination of the Ginna RPV BMI penetration nozzles every other refueling outage.

The regulations in 10 CFR 50.55a(z) state that alternatives to the requirements of paragraphs (b) through (h) of 10 CFR 50.55a, or portions thereof, may be used when authorized by the Director, Office of Nuclear Reactor Regulation. A proposed alternative must be submitted and authorized prior to implementation. Paragraph 50.55a(z)(1) of 10 CFR states that alternatives to the requirements of paragraphs (b) through (h) may be used when authorized by the U.S. Nuclear Regulatory Commission (NRC) if the licensee demonstrates that the proposed alternative would provide an acceptable level of quality and safety.

Based on the above, and subject to the following technical evaluation, the NRC staff finds that the licensee may propose an alternative, and the NRC staff has the regulatory authority to authorize the proposed alternative requested by the licensee.

3.0 TECHNICAL EVALUATION

3.1 Applicable Code Requirement and Components Affected Paragraph 50.55a(g)(6)(ii)(E) of 10 CFR requires, in part, that licensees of PWRs augment their ISI program by implementing the requirements of ASME Code Case N-722-1. The 36 RPV BMI penetration nozzles at Ginna are classified as Item No. B15.80 (Table 1 of Code Case N-722-1),

which requires that all penetrations undergo bare-metal visual examinations every other refueling outage.

3.2

Reason for Request

During manufacture of the Ginna RPV, the RPV bottom head was coated with a grey carboline paint (ADAMS Accession No. ML033510022). Consequently, the licensee is unable to perform a complete bare-metal visual examination per the requirements of ASME Code Case N-722-1.

The licensee has documented the extent of the paint occlusion, which ranges from 12.5 percent to 100 percent across all 36 BMI nozzles, with 10 BMI nozzles being 100 percent occluded with paint at the annuli. The licensee has also confirmed through replication that the paint occlusion would be difficult to remove such that a 100 percent bare-metal visual inspection could be performed per the requirements of the ASME Code case.

3.3 Licensees Proposed Alternative and Basis for Use The licensees proposed alternative, I6R-01, is to perform an as-found visual examination of the painted BMI penetration nozzle surfaces during every refueling outage, as opposed to a bare-metal visual examination in accordance with Code Case N-722-1.

The licensee submitted an identical proposed alternative in a relief request by letter dated December 16, 2011, for the fifth 10-year ISI interval at Ginna (ADAMS Accession No. ML11363A074). As part of that submittal, the licensee conducted a comprehensive full-scale BMI mockup testing with the assistance of the Southwest Research Institute (ADAMS Accession No. ML11363A076). Based on those tests, it was determined that the presence of carboline paint applied to the Ginna RPV bottom head would not prevent the observation of evidence of a leak from the RPV BMI penetration nozzles. Specifically, those tests confirmed that the paint in the annulus was not an effective barrier for either liquid or steam when exposed to pressures significantly lower than operating conditions. Furthermore, those tests also confirmed that the presence of paint in the annulus did not significantly alter the corrosion rates within the annulus when compared with unpainted surfaces. By letter dated June 29, 2012, the NRC staff approved the licensees proposed alternative (ADAMS Accession No. ML12179A322).

The licensee has performed similar visual examinations during each refueling outage since 2003 and has not identified any leakage related to the BMI nozzles or their associated J-grove welds. Additionally, the licensee performed volumetric examinations on all 36 BMI nozzles during the 2011 refueling outage. These examinations did not reveal any service-related degradation.

Based on the examinations and testing performed to date, Exelon concluded that proposed alternative I6R-01 provides an equal or better leakage detection capability than the current requirements; therefore, the criteria of 10 CFR 50.55a(z)(1) is satisfied.

3.4 Duration of Proposed Alternative The licensee requested relief until such time that 10 CFR 50.55a(g)(6)(ii)(E) is revised to impose visual examinations of BMI nozzle bare-metal surfaces more frequently than once every other refueling outage. The staffs understanding is that the licensee is requesting this relief for all future ISI intervals unless the requirements of 10 CFR 50.55a(g)(6)(ii)(E) are revised, at which time the licensee would have to request relief again. However, as discussed in the staffs evaluation below, the staff considered the applicability for the licensees proposed alternative only for Ginnas sixth 10-year ISI interval.

3.5

NRC Staff Evaluation

The regulations delineated in 10 CFR 50.55a(g)(6)(ii)(E) require licensees to implement the inspection requirements of ASME Code Case N-722-1, as conditioned. These requirements in part provide reasonable assurance that reactor coolant system leakage as a result of primary water stress corrosion cracking of Alloy 600 RPV BMI penetration nozzles is identified before:

1.

Conditions exist that could lead to the failure (ejection) of a BMI nozzle due to outside diameter stress corrosion cracking of the BMI nozzle, or

2.

Conditions exist that could lead to the failure (rupture) of the low alloy steel of the RPV head due to boric acid corrosion.

The staff has evaluated the proposed alternative to achieve these objectives.

The effectiveness of the licensees proposed alternative is predicated on two specific points:

1.

A visual examination of the occluded Ginna RPV BMI penetration nozzles will reliably result in the identification of signs of reactor coolant system leakage.

2.

The proposed frequency of the visual examinations will ensure that signs of reactor coolant system leakage will be identified in a timely fashion such that there is reasonable assurance that BMI nozzle ejection due to outside diameter stress corrosion cracking or RPV head rupture will not occur.

As the licensee is not able to perform bare-metal visual examination as defined in ASME Code Case N-722-1, it proposes to perform a visual examination every refueling outage rather than every other refueling outage. The paint occlusion that is hindering the performance of the bare-metal examinations has been documented by the licensee and ranges from 12.5 percent to 100 percent for the 36 BMI nozzles at Ginna, with 10 nozzles being 100 percent occluded.

For BMI nozzles where the occlusions are less than 100 percent, it is highly likely that any leakage of borated water through the nozzle wall or through the J-groove weld would flow down, fill up the portions of the annulus that are not occluded, and provide evidence of leakage through visible boric acid deposits. Therefore, the concern with partially occluded BMI nozzles is the possibility that leaks may take longer to reach the outside of the annulus if the annulus is partially full of paint. However, the licensees proposal to perform the visual examination every outage compensates for any additional time that may be needed for evidence of leakage to become apparent.

The licensees mockup testing provided convincing evidence that even when the annulus was very tight and fully occluded, leakage occurred at significantly lower pressures than the expected operating pressures at Ginna, and evidence of leakage was readily discernable. The staff previously evaluated the results of the mockup testing during the fifth ISI interval submittal as documented by the staffs safety evaluation dated February 22, 2013 (ADAMS Accession No. ML13039A292), and determined that the 2011 mockup tests demonstrated that even in the worst-case scenario, leakage was apparent. Specifically, these tests verified that significant wicking of the mockup paint into the annulus region produced little impediment to leakage.

Consequently, the staff concluded that there is reasonable assurance that the presence of paint at the BMI nozzles would not hinder the observation of leakage and would function in a manner nearly similar to BMI nozzles without paint (bare metal).

In summary, the staff concludes that the licensees proposal to perform inspections of Ginnas BMI nozzles to the visual examination requirements of ASME Code Case N-722-1, but in the as found condition and every refueling outage, provides an acceptable level of quality and safety. By performing the visual examinations in the as found condition every refueling outage, the licensee will address the potential delay in identifying leaks due to the paint occlusions because the visual examinations will identify the presence or absence of leakage from the BMI nozzles, hence providing an opportunity for the licensee to take appropriate corrective action if leakage occurs. Therefore, the NRC staff finds that the licensee has provided an adequate technical basis to demonstrate that its proposed alternative provides an acceptable level of quality and safety.

Exelon requested relief until such time that the requirements in 10 CFR 50.55a(g)(6)(ii)(E) are revised to impose bare-metal visual examination of BMI nozzles more frequently than currently required. The available operating experience indicates that for the majority of the PWR fleet that is able to perform the 100 percent bare-metal visual examinations, the current requirements are adequate. Therefore, currently there are no plans to impose more frequent examinations.

4.0 CONCLUSION

As set forth above, the NRC staff determines that the licensees proposed alternative provides an acceptable 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)(1). Therefore, the NRC staff authorizes the use of the licensees proposed alternative I6R-01 at Ginna for the duration of the sixth 10-year ISI Interval.