ML16004A262

Relief Request 15-ON-004: Limited Visual Examinations of the Reactor Pressure Vessel Support Skirt for the Fourth 10-Year Inservice Inspection Interval Program

ML16004A262
Person / Time
Site:	Oconee
Issue date:	01/07/2016
From:	Markley M Plant Licensing Branch II
To:	Batson S Duke Energy Carolinas
Whited J
References
CAC MF6508, CAC MF6509, CAC MF6510
Download: ML16004A262 (8)

Text

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~ ~ January 7, 2016 oi-~ ~o Mr. Scott Batson Site Vice President Oconee Nuclear Station Duke Energy Carolinas, LLC 7800 Rochester Highway Seneca, SC 29672-0752

SUBJECT:

OCONEE NUCLEAR STATION, UNITS 1, 2, AND 3 - RELIEF REQUEST 15-0N-004: LIMITED VISUAL EXAMINATIONS OF THE REACTOR PRESSURE VESSEL SUPPORT SKIRT FOR THE FOURTH 10-YEAR INSERVICE INSPECTION INTERVAL PROGRAM (CAC NOS. MF6508, MF6509, AND MF6510)

Dear Mr. Batson:

By letter dated July 15, 2015, Duke Energy Carolinas, LLC (the licensee) requested U.S.

Nuclear Regulatory Commission (NRC) approval of relief request 15-0N-004 for the fourth 10-year inservice inspection (ISi) interval program at Oconee Nuclear Station, Units 1, 2, and 3 (ONS). Relief request 15-0N-004 requested relief from the examination requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),

Section XI, for the reactor pressure vessel (RPV) support skirt at ONS.

Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(5)(iii),

the licensee requested relief from the ASME Code Section XI examination requirements for the RPV support skirts at ONS on the basis that conformance with the code requirement is impractical.

The NRC staff has concluded, as stated in the enclosed Safety Evaluation, that granting reli_ef pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property, or the common defense and security, and is otherwise in the public interest given due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility. Furthermore, the NRC staff has concluded that the examinations performed to the extent practical provide reasonable assurance of structural integrity of the subject component. Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(g)(5)(iii). Therefore, the NRC staff grants relief pursuant to 10 CFR 50.55a(g)(6)(i) for the subject limited examination of the RPV support skirt, as described in relief request 15-0N-004, for the fourth 10-year ISi interval at ONS.

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

S. Batson If you have any questions, please contact the ONS Senior Project Manager, Mr. James R. Hall, at randy.hall@nrc.gov or 301-415-4032.

Sincerely, Michael T. Markley, Chief Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-269, 50-270, and 50-287

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 RELIEF REQUEST 15-0N-004 REGARDING LIMITED VISUAL EXAMINATION OF THE REACTOR PRESSURE VESSEL SUPPORT SKIRT DUKE ENERGY CAROLINAS, LLC OCONEE NUCLEAR STATION, UNITS 1, 2, AND 3 DOCKET NOS. 50-269, 50-270 AND 50-287

1.0 INTRODUCTION

By letter dated July 15, 2015, 1 Duke Energy Carolinas, LLC (the licensee) requested U.S.

Nuclear Regulatory Commission (NRC) approval of relief request 15-0N-004 for the fourth 10-year inservice inspection (ISi) interval program at Oconee Nuclear Station, Units 1, 2, and 3 (ONS). Relief request 15-0N-004 requested relief from the examination requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),

Section XI, for the reactor pressure vessel (RPV) support skirt at ONS.

Specifically, pursuant to Title 10 of the Code of Federal Regulations (1 O CFR) 50.55a(g)(5)(iii),

the licensee requested relief from the ASME Code Section XI examination requirements for the RPV support skirts at ONS on the basis that conformance with the code requirement is impractical.

2.0 REGULATORY EVALUATION

Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests conducted during the first 10-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code, which was incorporated by reference in 10 CFR 50.55a(a) 12 months prior to the start of the 120-month interval, subject to the conditions listed in 10 CFR 50.55a(b)(2).

1 Agencywide Documents Access and Management System (ADAMS) Accession No. ML15201A573.

Enclosure

The regulations in 10 CFR 50.55a(g)(5)(iii) state that if licensees determine that conformance with certain ASME Code requirements is impractical, the licensee shall notify the Commission and submit information in support of the determination. Determination of impracticality in accordance with this section must be based on the demonstrated limitations experienced when attempting to comply with the ASME Code requirements during the ISi interval for which the request is being submitted. Pursuant to 10 CFR 50.55a(g)(5)(iv), request~ for relief made in

• accordance with this section must be submitted to the NRC no later than 12 months after the expiration of the initial 120-month inspection interval or subsequent 120-month inspection interval for which relief is sought.

The regulations in 10 CFR 50.55a(g)(6)(i) state, in part, that:

The Commission will evaluate determinations under paragraph (g)(5) of this section that code requirements are impractical. The Commission may grant such relief and may impose such alternative requirements as it determines are authorized by law and will not endanger life or property or the common defense and security,* and are otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.

The licensee requested relief from the ASME Code,Section XI requirements pursuant to 10 CFR 50.55a(g)(5)(iii). The licensee's request for relief is applicable to the fourth 10-year ISi interval program at ONS. The applicable Code of record for the fourth 10-year ISi interval program at ONS is the 1998 Edition of the ASME Code,Section XI, through the 2000 Addenda.

The proposed alternative is requested for the fourth ISi interval for ONS.

The fourth ISi interval for ONS, Unit 1 began on January 1, 2004 and ended on July 15, 2014.

The fourth ISi interval for ONS, Unit 2 began on September 9, 2004 and ended on July 15, 2014.

0 The fourth ISi interval for ONS, Unit 3 began on January 2, 2005 and ended on July 15, 2014.

The licensee submitted relief request 15-0N-004 no later than 12 months after the expiration of the fourth 10-year ISi interval at ONS. Therefore, the licensee has satisfied the requirement of 10 CFR 50.55a(g)(5)(iv) that requests for relief must be submitted no later than 12 months after the expiration of the ISi interval for which relief is sought.

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 proposed relief request.

3.0 TECHNICAL EVALUATION

3.1 Component Identification and Code Requirements Relief request 15-0N-004 requests relief for the RPV support skirt for the fourth 10-year ISi interval program at ONS. Specifically, the licensee requested relief for the following components:

ASME Code Licensee's ONS Examination ASME Code Component Component Unit Cateqorv *Item Description Number Unif 1 F-A F1 .40 RPV Support Skirt 1-RPV-WR36 Unit 2 F-A F1 .40 RPV Support Skirt 2-RPV-WR36 Unit 3 F-A F1.40 RPV Support Skirt 3-RPV-WR36 The RPV support skirt is an ASME Code Class 1 support that is subject to the examination requirements of Examination Category F-A in Table IWF-2500-1 of the 1998 Edition of the ASME Code,Section XI, through the 2000 Addenda. The ASME Code,Section XI, Table IWF-2500-1, Examination Category F-A requires a VT-3 visual examination of 100 percent of the RPV support skirt (Item No. F1 .40) once each 10-year inspection interval.

3.2 Licensee's Basis for Relief In its letter dated July 15, 2015, the licensee noted tha.t performing the VT-3 visual examination of essentially 100% of the RPV support skirt as required by the ASME Code is impractical due to the existence of insulation panels that partially obstruct the visual examination surfaces.

Although these insulation panels can be removed, the result of removing the insulation to perform visual examination of essentially 100% of the reactor vessel support skirt would be excessive personnel radiation dose and additional personnel safety risk. Below are details as stated in the licensee's relief request:

The minimum estimated radiation dose associated with obtaining the maximum **

available coverage on the exterior surfaces of the support skirt is approximately 282.4 rem for each Unit.

The minimum estimated radiation dose associated with obtaining the maximum available coverage on the interior surfaces of the support skirt is approximately 1100 mrem for each Unit.

In order to remove the bottom row of mirror insulation needed to access the entire exterior surface of the support skirt, removal of additional rows of mirror insulation is necessary because they are supported by the bottom row of insulation. The upper rows of these insulation panels can slip when the supporting row of insulation is removed, creating a potential personnel safety risk.

Even if all insulation panels are removed, there will still be some portions of the skirt interior and exterior surfaces that cannot be examined because of permanef")t attachments to the support skirt to which the insulation is attached.

In its letter dated July 15, 2015, the licensee proposes the following alternative to performing the 100 percent VT-3 examination of the support skirt:

For each Unit, a VT-3 visual examination was performed on accessible surfaces of the Reactor Vessel Support Skirt. The calculated coverage is approximately 66.5%

(percent] of the support surface areas within the examination boundary specified in Figure IWF-1300-1 (c).

The VT-3 visual examinations were performed using personnel, equipment, and procedures qualified in accordance with the ASME Code,Section XI, 1998 Edition with the 2000 Addenda.

There were no unacceptable conditions or indications detected during these examinations.

3.3 NRC Staff Evaluation The ASME Code,Section XI, Table IWF-2500-1, Examination Category F-A, requires a VT-3 visual examination of 100 percent of the RPV support skirt. The VT-3 visual examination is conducted to observe the general mechanical and structural condition of the support skirt to ensure that it can continue to perform its intended function of providing load-bearing support to the RPV and internal components. The VT-3 examination provides a means of detecting gross structural deformation, misalignments, and'missing parts for the support items; it is not intended for detecting localized flaws or other small-scale degradation such as stress-corrosion cracking.

The ASME Code specifies a VT-3 because the support skirt is not susceptible to the types of localized aging affects that would require, at a minimum, a high resolution visual examination (such as a VT-1 visual) of all accessible surfaces. The licensee proposed as an alternative to the above ASME Code,Section XI, examination requirements, that the VT-3 visual examination of 66.5 percent of the interior and exterior surfaces of the support skirt can be examined on accessible surfaces, without removal and reinstallation of the insulation panels.

The licensee has shown that it is impractical to meet the ASME Code-required 100 percent VT-3 visual examination coverage for the RPV support skirt due to the d~sign configurations.

Based on the VT-3 visual examination coverage of 66.5 percent of the interior and exterior surfaces of the RPV support skirt obtained, it is reasonable to conclude that if significant service-induced degradation such as seismic-induced deformation, buckling, or misalignments had occurred, evidence of it would have been detected by the examinations that were performed. Furthermore, the NRC staff determined that the examinations performed provide reasonable assurance of structural integrity of the subject component.

4.0 CONCLUSION

The NRC staff has concluded, as set forth above, that granting relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property, or the common defense and security, and is otherwise in the public interest given due consideration to the burden upon the licensee that could result if the requirements were imp9sed on the facility.

Furthermore, the NRC staff has concluded that the examinations performed to the extent practical provide reasonable assurance of structural integrity of the subject component.

Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(g)(5)(iii). Therefore, the NRC staff grants relief pursuant to 10 CFR 50.55a(g)(6)(i) for the subject limited examination of the RPV support skirt, as described in relief request 15-0N-004, for the fourth 10-year ISi interval at ONS.

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

Principal Contributor: J. Jenkins Date: January 7, 2016

ML16004A262 *via memo dated OFFICE' DORL/LPLll-1/PM DORL/LP LI 1-1 /LA DE/EVIB/BC DORL/LPLll-1/BC NAME JWhited SFigueroa JMcHale* MMarkley DATE 12/30/15 01/05/16 12/17/15 01/07/16