ML092180954
| ML092180954 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 08/24/2009 |
| From: | Boyce T Plant Licensing Branch II |
| To: | Swafford P Tennessee Valley Authority |
| Sreenivas V.NRR/DORL/LPL2-1 415-2597 | |
| References | |
| TAC ME0155 | |
| Download: ML092180954 (7) | |
Text
UNITED NUCLEAR REGULATORY WASHINGTON, D.C. 20555-0001 August 24, 2009 Mr. Preston D. Swafford Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 BROWNS FERRY NUCLEAR PLANT-UNIT 1, THE SECOND TEN-YEAR INTERVAL INSERVICE INSPECTION PROGRAM RELATED TO ASME CODE CASE N-504-3, ALTERNATIVE RULES FOR REPAIR OF CLASSES 1,2, AND 3 AUSTENITIC STAINLESS STEEL PIPING (TAC NO. ME0155)
Dear Mr. Swafford:
By letter dated November 25,2008, the Tennessee Valley Authority (TVA, the licensee) submitted Relief Request (RR) 1-ISI-22 requesting relief'from the requirements specified in the American Society of Mechanical Engineers (ASME) Code,Section XI for repair of Classes 1, 2, and 3 Austenitic Stainless Steel Piping weld overlays under Title 10, Code of Federal Regulations (10 CFR), Section 50.55a(a)(3)(i) for the Browns Ferry Nuclear Plant (BFN), Unit 1. The request proposed that in lieu of the requirements of the ASME Code, Case N-504-3, Paragraph (h), performing a system hydrostatic test, proposed an alternative to perform a system leakage test at normal operating pressure and temperature.
The U.S. Nuclear Regulatory Commission (NRC) staff has completed its review of the information provided in TVA's November 25,2008, letter. The NRC staff concluded that the proposed alternative described in the licensee's letter provides an acceptable level of quality and safety. Therefore, RR-1-ISI-22 is authorized pursuant to 10 CFR 50.55a(a)(3)(i) for Browns Ferry Nuclear Plant, Unit 1. All other requirements of the ASME Code,Section XI 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.
P. Swafford -2 This relief is authorized for the remainder of the second 1 O-year inservice inspection interval at BFN, Unit 1 that is scheduled to end June 1, 2017. Sincerely, Docket No. 50-259
Enclosure:
Safety Evaluation cc w/encl: Distribution via Listserv UNITED NUCLEAR REGULATORY WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION INSERVICE INSPECTION PROGRAM RELIEF REQUEST 1-ISI-22 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT, UNIT 1 DOCKET NO. 50-259
1.0 INTRODUCTION
By letter dated November 25, 2008 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML083380201), the Tennessee Valley Authority (TVA, the licensee), requested relief from certain American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (ASME Code) requirements at Browns Ferry Nuclear Plant, Unit 1 (BFN). As an alternative to the ASME Code requirements, TVA proposed to implement a full structural weld overlay (FSWOL) repair in accordance with ASME Code Case N-504-3, Alternative Rules for Repair of Class 1, 2, and 3, "Austenitic Stainless Steel Piping,Section XI, Division 1," as modified by TVA in its submitlalletters.
The alternative documented in Relief Request (RR) 1-ISI-22 would be used to perform a leak test in lieu of a hydrostatic test on the FSWOL applied to the reactor pressure vessel (RPV) Feedwater N-1'1 B-1 austenitic stainless steel process pipe-to-austenitic stainless steel safe end weld. Although, the licensee has already implemented the installation of the FSWOL prior to the issuance of this safety evaluation (SE), this SE is being issued to document the decision made by the U.S. Nuclear Regulatory Commission (NRC) staff to grant the licensee's request by verbal authorization on November 26,2008. The NRC staff's memorandum dated December 12,2008 (ADAMS Accession No. ML083390526), reflects the basis for verbal approval.
2.0 REGULATORY EVALUATION
Pursuant to Title 10, Code of Federal Regulations (10 CFR), Section 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supportS) will meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, Rules for In service Inspection (lSI) 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 ten-year lSI interval and subsequent intervals comply Enclosure 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. BFN, Unit 1 second 1 O-year lSI interval is scheduled to end on June 1, 2017. The lSI Code of record for BFN for the second 10-year lSI interval is the ASME Code,Section XI, 2001 Edition, including 2003 Addenda. Pursuant to 10 CFR 50.55a(a)(3), alternatives to requirements may be authorized if the licensee demonstrates that: (i) the proposed alternatives 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. TVA, submitted the subject relief request, pursuant to 10 CFR 50.55a(a)(3)(i), which proposed an alternative to the implementation of the ASME Code,Section XI requirements based on ASME Code Case N-504-3, the deposition of a FSWOL for the remaining service life of the identified components.
ASME Code Case N-504-3 was conditionally accepted by the NRC in Regulatory Guide (RG) 1.147, Revision 15, "Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1," issued in October 2007. In RG 1.147, Revision 15, the NRC accepted ASME Code Case N-504-3 with the condition that the inspection requirements of ASME Code,Section XI, Nonmandatory Appendix Q, "Weld Overlay Repair of Class 1,2, and 3 Austenitic Stainless Steel Piping Weldments," shall be met as part of the installation and inspection of the weld overlay. 3.0 TECHNICAL EVALUATION 3.1 ASME Code Requirements for which Relief is Requested The lSI Code of record for BFN for the second 10-year lSI interval was the ASME Code,Section XI, 2001 Edition, including 2003 Addenda. Consistent with IWA-4220, repairs shall be performed in accordance with the licensee's design specification and the original Construction Code. Later editions and addenda of the Construction Code or of ASME Code,Section III, either in their entirety or portions thereof, and ASME Code Cases may be used. In this case, the licensee proposed to implement a weld overlay repair in accordance with ASME Code Case N-504-3 as modified by the condition placed on the code case in RG 1.147, Revision 15 and the approved alternatives.
3.2 Duration of Relief Request This relief request for Unit 1 is applicable to its second 1 O-year lSI interval that is scheduled to end on June 1,2017. 3.3 Licensee's Proposed Alternative to ASME Code Case N-504-3 ASME Code Case N-504-3, Requirement (h) specifies that a hydrostatic test be performed in accordance with ASME Code,Section XI, IWA-5000 if the flaw penetrates the original pressure boundary.
As an alternative, leak testing in accordance with IWA-5000 at nominal operating pressure and temperature in lieu of the system hydrostatic testing will be performed.
-3 3.4 Licensee's Justification for the Proposed Alternative Licensee stated in their justification for the granting of relief that, the stresses generated in the material during the system leak test at nominal operating pressure is less than 30 percent of the allowable stress and the stress generated by the hydrostatic pressure test was in the low 30-percent region of the allowable stress for that material.
Material stress conditions in these ranges would not tend to drive flaw growth to such an extent that leakage would be generated or significantly increased.
Therefore, no significant observable differences would be provided by the performance of the hydrostatic test and the system leakage test would provide an acceptable alternative.
On this technical basis, hydrostatic test requirements were deleted from ASME Code Cases N-416, "Alternative Pressure Test Requirement for Welded or Brazed Joints for Replacement Parts and Piping Subassemblies, or Installation of Replacement Items by Welding or Brazing, Classes 1, 2, and 3 Section XI, Division 1," and N-498, "Alternative Requirements for 10-Year System Hydrostatic Testing for Class 1, 2, and 3 SystemsSection XI, Division 1." The use of a system leak test at nominal operating pressure in lieu of a hydrostatic test has been incorporated in ASME Code,Section XI beginning in the 1998 Edition with the 1999 Addenda. Therefore, the licensee determined that this alternative provides an acceptable level of quality and safety. 3.5 Evaluation The licensee's proposed modification to Requirement (h) of ASME Code Case N-504-3 was to perform a system leak test at the nominal operating pressure corresponding to 100 percent rated reactor power in accordance with ASME Code,Section XI (2001 Edition with the 2003 Addenda), IWA-5000 and, by reference, ASME Code,Section XI, IWB-5000.
Precedence for use of a system leak test at the nominal operating pressure corresponding to 100 percent rated reactor power in lieu of a hydrostatic test, which would be conducted at a higher pressure, has been set with ASME Code Case N-416-1. ASME Code Case N-416-1 was accepted by the NRC staff in RG 1.147 and has been incorporated into ASME Code,Section XI beginning in the 1998 Edition with the 1999 Addenda. Unit 1 is currently in its second 10-year lSI interval and the lSI Code of record for this interval is the ASME Code,Section XI, 2001 Edition, including 2003 Addenda. The NRC staff reviewed the licensee's justification for the proposed alternative and finds it acceptable based on the following: since similar stresses are produced in the material during a system leak test at the nominal operating pressure corresponding to 1 OO-percent rated reactor power or during the hydrostatic test, any leakage that would otherwise occur during operation due to an existing defect will be identified regardless of the type of test (Le., hydrostatic test or system leak test) that is performed on the weld overlay, substitution of a system leak test at the nominal operating pressure corresponding to 100-percent rated reactor power for a hydrostatic test was incorporated in ASME Code,Section XI, 1998 Edition, 1999 Addenda, and
-4TVA, the licensee's alternative is consistent with the current industry practice, and a similar request by the license holder for the Cooper Nuclear Station was approved by the NRC staff in its letter dated August 15, 2008. Based on the above, the NRC staff determined that TVA, the licensee's proposed alternative to perform a system leak test at the nominal operating pressure corresponding to 1 OO-percent rated reactor power on the FSWOL applied to the Feedwater N-11 B-1 austenitic stainless steel process pipe-to-austenitic stainless steel safe end weld in lieu of a hydrostatic test provides an acceptable level of quality and safety.
4.0 CONCLUSION
The NRC staff has reviewed the licensees submittal and determined that, in accordance with 10 CFR 50.55a(a)(3)(i), to perform a system leak test at the nominal operating pressure corresponding to 100-percent rated reactor power on the FSWOL applied to the Feedwater N-11 B-1 austenitic stainless steel process pipe-to-austenitic stainless steel safe end weld in lieu of a hydrostatic test provides an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the alternative proposed in Relief Request 1-ISI-22 is authorized for the second 10-year lSI interval at BFN, Unit 1 that is scheduled to end June 1, 2017. All other ASME Code,Section XI 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:
G. Cheruvenki Date: August 24, 2009 P. Swafford -2 This relief is authorized for the remainder of the second 10-year inservice inspection interval at BFN, Unit 1 that is scheduled to end June 1,2017. Docket No.
Safety cc w/encl: Distribution via LPL2-2
DDiaz-Toro, ADAMS ACCESSION No*..
Sincerely, IRA! Thomas H. Boyce, Chief Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation NRR-106 OFFICE LPL2-1/PM LPL2-2/PM LPLP-WB/LA CVIB/BC LPL2-2/BC NAME VSreenivas SLingam for EBrown BClayton MMitchell by memo TBoyce DATE 8/12/09 08/19/09 08/20109 02/9109 08/24/09 OFFICIAL RECORD COPY