ML16141B010
| ML16141B010 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 02/23/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML16141B009 | List: |
| References | |
| NUDOCS 9602280035 | |
| Download: ML16141B010 (3) | |
Text
pREGU 01 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION OF THE THIRD TEN-YEAR INTERVAL INSERVICE INSPECTION PROGRAM PLAN REQUEST FOR RELIEF NO. 95-05 FOR DUKE POWER COMPANY OCONEE NUCLEAR STATION, UNIT 1 DOCKET NO. 50-269
1.0 INTRODUCTION
The Technical Specifications for Oconee Nuclear Station, Unit 1, state that the inservice inspection of the American Society of Mechanical Engineers (ASME) Code Class 1, 2, and 3 components shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicable Addenda as required by Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g),
except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i).
Section 50.55a(a)(3) states that alternatives to the requirements of paragraph (g) 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 difficulties without a compensating increase in the level of quality and safety.
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, "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. 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 incorporated by reference in 10 CFR 50.55a(b) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable edition of Section XI of the ASME Code for the Oconee Nuclear Station, Unit 1 third 10-year inservice inspection (ISI) interval is the 1989 Edition, No Addenda. The components (including supports) 9602280035 960223 PDR ADOCK 05000269 P
-PDR
-2 may meet the requirements set forth in subsequent editions and addenda of the ASME Code incorporated by reference in 10 CFR 50.55a(b) subject to the limitations and modifications listed therein and subject to Commission approval.
Pursuant to 10 CFR 50.55a(g)(5), if the licensee determines that conformance with an examination requirement of Section XI of the ASME Code is not practical for its facility, information shall be submitted to the Commission in support of that determination and a request made for relief from the ASME Code requirement. After evaluation of the determination, pursuant to 10 CFR 50.55a(g)(6)(i), the Commission may grant relief and may impose alternative requirements that are determined to be authorized by law, will not endanger life, 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. In a letter dated December 4, 1995, Duke Power Company submitted to the NRC its third 10-year interval inservice inspection program plan, Request for Relief No. 95-05, for the Oconee Nuclear Station, Unit 1.
2.0 EVALUATION The staff has evaluated the information provided by the licensee in support of Request for Relief No. 95-05 for the Oconee Nuclear Station, Unit 1, as follows:
2.1 Licensee's Request The licensee requested relief from the Code-required 100% volumetric examination of the 1A High Pressure Injection (HPI) Letdown Cooler, primary side inlet and outlet, channel nozzle to tube side channel body welds.
Code Requirement ASME Section XI, 1989 Edition (no addenda), Paragraph IWA-7530, IWB-2200, IWB-7400, and Table IWB-2500-1, Examination Category B-D, require replacement welds receive a preservice inspection prior to the return of the plant to service. Code Case N-460 specifies-90 percent or greater examination coverage as meeting the criteria of an adequate examination.
Licensee's Basis for Requesting Relief (as stated):
Conformance with the ASME Section XI requirements for examination coverage for the subject welds is impractical.
During the replacement of the Unit 1 'A' HPI letdown cooler, the nozzle welds for the primary side inlet and outlet were ultrasonically examined to satisfy the preservice examination requirements of ASME Section XI.
Due to component geometry, joint configuration, and interferences, 90%
examination coverage could not be obtained on these welds. The examination coverage obtained on the Channel Nozzle weld on the inlet and outlet was 36.5%. The joint configurations for these two welds are
-3 such that radiographic examination [cannot] be used to supplement the ultrasonic examination to increase the examination coverage. These welds have received a liquid penetrant examination of the root and final weld passes by the manufacturer. The primary side of the cooler was hydrostatically tested by the manufacturer at 3750 PSIG.
Licensee's Proposed Alternative Examination (as stated):
An acceptable NDE and hydrostatic test were performed by the Manufacturer. A limited ultrasonic examination was performed by Duke Power Company.
2.2 Staff Evaluation As part of the evaluation of the relief request, the NRC staff reviewed the component drawings and UT limitation data. Based on this review, it has been determined that part geometry, joint configuration, and interferences preclude full volumetric coverage of the subject welds. Therefore, obtaining the Code required preservice examination coverage is impractical.
To obtain Code required coverage, design modifications would be necessary to eliminate the coverage limitations. Imposition of this requirement would cause a considerable burden on the licensee.
The manufacturer performed liquid penetration examinations of the root and final welds, and hydrostatically tested the heat exchanger to 3750 psig.
During replacement, the licensee performed the required fabrication nondestructive examinations associated with the replacement welds. The preservice volumetric examination coverage obtained included 36.5% coverage on each of the nozzle-to-vessel welds. Based on the examinations and tests performed, it is reasonable to conclude that flaws, if present, should have been detected. As a result, reasonable assurance of structural integrity has been provided.
3.0 CONCLUSION
The staff has reviewed the Oconee Nuclear Station, Unit 1, Request for Relief 95-05. Based on this evaluation, it is concluded that obtaining the preservice Code-required volumetric coverage for the subject High Pressure Injection Letdown Cooler nozzle welds is impractical for Oconee Nuclear Station, Unit 1. Therefore, that relief is granted pursuant to 10 CFR 50.55a(g)(6)(i). The relief is authorized by law and will not endanger life or property or the common defense and security, and is otherwise in the public interest giving due consideration to the burden that could result if the requirements were imposed on the facility.
Principal Contributor: L. Wiens Date:
February 23, 1996