ML15112A702
| ML15112A702 | |
| Person / Time | |
|---|---|
| Site: | Oconee, Mcguire, Catawba, McGuire  |
| Issue date: | 11/24/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML15112A701 | List: |
| References | |
| NUDOCS 9812010075 | |
| Download: ML15112A702 (4) | |
Text
A00 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST FROM ASME CODE, SECTION XI REQUIREMENT DUKE ENERGY CORPORATION CATAWBA NUCLEAR STATION, UNITS 1 AND 2 MCGUIRE NUCLEAR STATION, UNITS 1 AND 2 OCONEE NUCLEAR STATION, UNITS 1. 2, AND 3 DOCKET NOS. 50-413, 50-414, 50-369, 50-370, 50-269, 50-270, AND 50-287
1.0 INTRODUCTION
Pursuant to Title 10 of the Code of Federal Regulations (10 CFR) Section 50.55a(g), the inservice inspection (ISI) of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) Class 1, 2, and 3, components at the Catawba Nuclear Station, Units 1 and 2 (Catawba), McGuire Nuclear Station, Units 1 and 2 (McGuire), and Oconee Nuclear Station, Units 1, 2, and 3 (Oconee), shall be performed in accordance with Section XI of the ASME Code and applicable Addenda, except where 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 NRC if (i) the proposed alternative provides 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.
As published in the Federal Register (No. 154, Volume 61, dated August 8, 1996), the Commission announced an amendment to its regulation of 10 CFR Part 50, Section 55a (rule).
The rule incorporated, by reference, the 1992 Edition with 1992 Addenda of Subsections IWE and IWL of Section XI of the ASME Code. Subsections IWE and IWL provide the requirements for ISI of Class CC (concrete containments), and Class MC (metallic containments) of light water cooled power plants. The effective date for the amended rule was September 9, 1996, which requires the licensees to incorporate the new requirements into their 151 plans and to complete the first containment inspection by September 9, 2001. However, a licensee can submit a request for relief from one or more requirements of the regulation (or the endorsed Code requirements) with proper justification.
By letter dated April 6, 1998, as supplemented by letters dated June 10, and August 18, 1998, Duke Energy Corporation (DEC or the licensee), submitted to the NRC Relief Request No. 98 9812010075 981124 PDR ADOCK 05000269 G
PDR L.
-2 GO-002 for the Catawba Nuclear Station, Units 1 and 2, McGuire Nuclear Station, Units 1 and 2, and Oconee Nuclear Station, Units 1, 2, and 3. The April 6, 1998, letter requested relief under provisions of 10 CFR 50.55a(a)(3)(ii). The licensee is seeking relief from the bolt torque or tension test requirements for pressure-retaining bolting of Class MC pressure-retaining components and metallic liners of Class CC components, as specified in the ASME Code,Section XI, 1992 Edition with the 1992 Addenda, IWE-2500, Table IWE-2500-1, "Examination Categories - Examination Category E-G, Pressure Retaining Bolting," Item No.
E8.20 (Bolted Connections). The letters dated June 10, and August 18, 1998, provided responses to the staffs requests for additional information (RAls). The first RAI was provided in the staffs letter of May 29, 1998, and the second RAI was discussed during a telephone conference on August 17, 1998.
The licensee believes that the above requirement is impractical and that compliance with the specified requirement of Subsection IWE would result in hardship or unusual difficulty without a compensating increase in the level of quality or safety. In addition, the licensee believes that existing surveillance requirements are sufficient to assure the leaktight integrity of containment pressure-retaining seals and gaskets.
2.0 DISCUSSION 2.1 Requirement from Which Relief is Requested:
Relief is requested from ASME Code 1992 Edition, 1992 Addenda, Table IWE-2500-1, "Examination Category E-G Pressure Retaining Bolting," Item No. E8.20 (Bolted Connections).
2.2 System/Components for Which Relief is Requested:
Pressure-retaining bolting of Class MC pressure-retaining components and metallic shell and penetration liners of Class CC components.
2.3 Code Requirement and Relief Request The ASME Boiler and Pressure Vessel Code,Section XI, Division 1, 1992 Edition with the 1992 Addenda, Subparagraph IWE-2500 (a) requires that bolt torque or tension tests be performed on pressure-retaining bolted connections as specified in Table IWE-2500-1, "Examination Category E-G, Pressure Retaining Bolting," Item No. E8.20. The specific requirement is to perform a bolt torque or tension test on 100 percent of the containment pressure-retaining bolted connections that have not been disassembled and reassembled during an inspection.
2.4 Basis for Requesting Relief If bolt tension tests are to be performed, the bolting must be detensioned and then retensioned to determine acceptability. This activity could potentially affect the leaktightness of the joint.
Bolt torque tests performed on bolting under tension could also affect the leaktightness of the joint. To ensure the bolted joint remains leaktight, a 10 CFR Part 50, Appendix J, Type B test would be required following these maintenance activities. The performance of the Type B test
A 0e
-3 itself provides assurance that the bolt torque or tension is adequate to prevent a leak rate that exceeds allowable limits. Torque or tension tests do not provide this assurance. Once a bolt is properly torqued or tensioned, it is not subject to dynamic loading that could cause it to experience significant change. Furthermore, relaxation of bolting occurs after initial installation, and accurate estimates of the expected pre-load loss are not always reliable, making it difficult to establish an acceptance range for torque testing. Verification of torque or tension values on bolted joints is proven through Appendix J testing, and visual examination of bolting in accordance with IWE-2500 is sufficient to detect potential degradation that may cause the bolted connection to violate the leaktight integrity of the containment. Additionally, experience has shown that containment bolted connections have not exhibited excessive leakage due to inadequate bolt torque or tension.
2.5 Alternative Examinations DEC has stated that the adequacy of containment pressure-retaining bolted connections shall be verified by the following examinations and tests required by the Subsection IWE Code and pertinent provisions of plant specifications:
(1) Bolted connections shall receive a visual VT-1 examination in accordance with requirements of Table IWE-2500-1, "Examination Category E-G, Pressure Retaining Bolting," Item No. E8.10 (Bolted Connections), and (2) A local leak rate test shall be performed on all containment penetrations, airlocks, and other pressure-retaining bolted connections in accordance with 10 CFR 50, Appendix J (Option A of 10 CFR 50, Appendix J for Type B tests).
3.0 EVALUATION The staff has reviewed the information provided by the licensee's letters dated April 6, June 10, and August 18, 1998, in support of Relief Request No. 98-GO-002, for the Catawba Nuclear Station, Units 1 and 2, McGuire Nuclear Station, Units 1 and 2, and the Oconee Nuclear Station, Units 1, 2, and 3. The licensee has provided information that shows that the alternative examinations and testing will provide assurance of leaktight integrity of bolted connections and that requirements of the Code would result in a hardship without a compensating increase in the level of quality and safety. This supports the granting of relief from the bolt torque or tension test requirements for pressure-retaining bolting of Class MC pressure-retaining components and metallic liners of Class CC components, as specified in the ASME Code,Section XI, 1992 Edition with the 1992 Addenda, IWE-2500, Table IWE-2500-1, "Examination Category E-G Pressure Retaining Bolting," Item No. E8.20 (Bolted Connections).
Also, in response to the staff's RAI (letter dated May 29, 1998), related to the number of pressure unseating penetrations where bolts are used to keep the seals and metal surfaces leaktight, the licensee indicated that there are only two airlocks in each of the Catawba and McGuire plants and none in Oconee plants that are installed with pressure unseating configurations. The fact that there are no pressure unseating penetrations at Oconee, and only two air locks with pressure unseating penetrations for Catawba and McGuire, lessens our concern regarding the approval of the requested relief.
-4 Additionally, in a telephone conference held between the staff and the representatives of DEC on August 17, 1998, the licensee confirmed that the test activities covered by Item 2.5(2) above included the implementation of the requirements of Item Nos. E9.30 (Air Locks) and E9.40 (Seals and Gaskets) in Table IWE-2500-1, "Examination Categories - Examination Category E-P, All Pressure Retaining Components," ASME Code,Section XI, Division 1, Subsection IWE.
This assured the staff that the licensee is complying with the requirements of E9.30 and E9.40, and therefore, providing assurance that the penetrations would provide the required pressure-retaining function. On August 18, 1998, the licensee provided the NRC a letter which formally documented the above confirmation.
3.0 Conclusion Having considered past experience of operating plants related to the subject matter and the assurance of leaktight integrity of the bolted connections, the staff finds that the torque or tension testing of bolts during IWE examination, when the bolts are not disassembled, will result in hardship without a compensating increase in the level of quality or safety. Therefore, the proposed alternative in Relief Request 98-GO-002 is authorized pursuant to 10 CFR 50.55a(a)(3)(ii).
Principal Contributor: D. Jeng Date: November 24, 1998