ML060960040
| ML060960040 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 08/22/2006 |
| From: | Raghavan L NRC/NRR/ADRO/DORL/LPLII-2 |
| To: | Singer K Tennessee Valley Authority |
| Chernoff Margaret H. NRR/DORL 415-4041 | |
| References | |
| TAC MC0534 | |
| Download: ML060960040 (8) | |
Text
August 22, 2006 Mr. Karl W. Singer Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801
SUBJECT:
BROWNS FERRY NUCLEAR PLANT, UNIT 1 - RE: REQUEST FOR RELIEF FROM THE REQUIREMENTS OF THE ASME CODE (TAC NO. MD0534)
Dear Mr. Singer:
By letter dated March 15, 2006, the Tennessee Valley Authority (TVA) submitted a request for the use of alternatives to certain American Society of Mechanical Engineers Boiler and Pressure Vessel Code,Section XI requirements at Browns Ferry Nuclear Plant, Unit 1.
The U.S. Nuclear Regulatory Commission staff has reviewed and evaluated the information provided in support of TVAs Relief Request No. 1-ISI-20, related to augmented weld examination requirements. Based on the conclusions contained in the enclosed safety evaluation, the staff authorizes relief pursuant to Title 10, Code of Federal Regulations (10 CFR), Section 50.55a(a)(3)(i) and 50.55a(g)(6)(ii)(A)(5) on the basis that the augmented examination of the reactor pressure vessel welds to the maximum extent possible provides an acceptable level of quality and safety.
Relief is authorized for the above requested one-time augmented inspection as required by 10 CFR 50.55a(g)(6)(ii)(A)(2).
The staffs safety evaluation is enclosed.
Sincerely,
/RA/
L. Raghavan, Chief Plant Licensing Branch II-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-259
Enclosure:
Safety Evaluation cc w/encl: See next page
ML060960040 NRR-028 OFFICE NRR/LPL2-2/PM NRR/LPL2-2/PM NRR/LPL2-2/LA OGC NRR/CVIB/BC NRR/LPL2-2/BC NAME LRegner MChernoff BClayton MZobler MMitchell LRaghavan DATE 8/16/06 8/16/06 8/16/06 8/21/06 8/16/06 8/22/06
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME) SECTION XI AUGMENTED EXAMINATION OF REACTOR VESSEL WELDS REQUEST FOR RELIEF 1-ISI-20 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT UNIT 1 DOCKET NO. 50-259
1.0 INTRODUCTION
By letter dated March 15, 2006, Tennessee Valley Authority (TVA) submitted Request for Relief 1-ISI-20 from certain augmented inservice inspection requirements of Title 10 of the Code of Federal Regulations (10 CFR) Part 50.55a(g)(6)(ii)(A)(2) for Browns Ferry Nuclear Plant, Unit 1 (BFN Unit 1). In support of this one-time relief request, TVA proposes conducting the inspections of reactor pressure vessel welds to the maximum extent possible.
2.0 REGULATORY REQUIREMENTS As stated in 10 CFR Part 50.55a(g)(6)(ii)(A)(2), all licensees shall augment their reactor pressure vessel (RPV) examination by implementing once, as part of the inservice inspection interval in effect on September 8, 1992, the examination requirements for the RPV shell welds specified in Item B1.10 of Examination Category B-A, Pressure Retaining Welds in Reactor Vessel, in Table IWB 2500-1 of Subsection IWB,Section XI of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code). The licensee has adopted the 1995 Edition through the 1996 Addenda of ASME Code,Section XI as the examination Code of record for BFN Unit 1.
For the purpose of this augmented examination, essentially 100% as used in Table IWB-2500-1 means more than 90 percent of the examination volume of each weld, where the reduction in coverage is due to interference by another component or part geometry.
As stated in 10 CFR Part 50.55a(g)(6)(ii)(A)(5) and 10 CFR 50.55a(a)(3)(i), licensees that make a determination that they are unable to completely satisfy the requirements for the augmented RPV shell weld examination specified in 10 CFR Part 50.55a(g)(6)(ii)(A) shall submit information to the Nuclear Regulatory Commission (NRC) to support that determination and also propose an alternative RPV examination that provides an acceptable level of quality and safety. The licensee may use this alternative examination when authorized by the Director of the Office of Nuclear Reactor Regulation.
3.0 TECHNICAL EVALUATION
Code Requirement:
Examination requirements for the RPV shell welds are specified in Item B1.10 of Examination Category B-A, Pressure Retaining Welds in Reactor Vessel, in Table IWB 2500-1 of Subsection IWB,Section XI of the ASME Code. The licensee has adopted the 1995 Edition through the 1996 Addenda of ASME Code,Section XI as the examination Code of record for BFN Unit 1.
Component Identification:
The affected component is the BFN Unit 1 RPV; specifically, the components identified in the table below. The examination categories and item numbers are from the Table IWB-2500-1 of the 1995 Edition of ASME Code,Section XI.
Examination Category Item Number Description Component IDs B-A B1.12 Longitudinal Shell Welds V-3-A, V-3-B, V-3-C Licensees Code Relief Request: (as stated)
Relief is requested from the requirement to perform a volumetric examination of essentially 100 percent of the three RPV longitudinal shell welds.
Licensees Basis for Requesting Relief: (as stated)
Areas of the V-3-a, V-3-B and V-3-C welds are inaccessible for ultrasonic examination due to the design configuration of the RPV and vessel internals.
Licensees Proposed Alternative Examination: (as stated)
In lieu of the Code required essentially 100 percent volume ultrasonic examination, BFN Unit 1 proposes an ultrasonic examination of accessible areas to the maximum extent practical given the component design, and configuration of the subject welds.
Basis for Proposed Alternative In accordance with 10 CFR 50.55a(g)(6)(ii)(A)(5), the licensee has requested relief from certain augmented weld examination requirements, which are performed according to Section XI of the ASME Boiler and Pressure Vessel Code.
TVA maintains that some areas of the V-3-A, V-3-B, and V-3-C welds are inaccessible for ultrasonic examination due to the design configuration of the RPV and vessel internals. The examinations were performed to the maximum extent practical with automated ultrasonic equipment from the vessel inside surface. The V-3-A, V-3-B, and V-3-C RPV longitudinal shell weld scans were partially obstructed by the core spray piping and feedwater spargers. TVA also states that conducting ultrasonic examination of these subject welds from the outside surfaces is not practical because of the design of the RPV insulation and proximity of the bio-shield wall. The licensee states in the relief request that performing 100 percent volumetric examination of the RPV shell welds as required by the ASME Code would not provide a substantial increase in quality and safety.
In lieu of the ASME Code-required essentially 100 percent volume coverage using ultrasonic examination, the licensee proposes an ultrasonic examination of accessible areas to the maximum extent practical given the component design and configuration of the subject welds.
4.0 STAFF EVALUATION To comply with the augmented reactor vessel examination requirements of 10 CFR 50.55a(g)(6)(ii)(A), licensees must volumetrically examine essentially 100 percent of each of the Item B1.12 longitudinal shell welds. However, given design and geometry considerations, essentially 100 percent coverage is sometimes not physically practical. Thus, pursuant to 10 CFR Part 50.55a(g)(6)(ii)(A)(5), an alternative examination can be approved for use if that alternative can provide an acceptable level of quality and safety. As an alternative to the 10 CFR Part 50.55a(g)(6)(ii)(A) requirements, the licensee proposes that the examination coverage obtained provides an acceptable level of quality and safety for the subject RPV welds.
At BFN Unit 1, the augmented coverage requirements could not be met for 3 of the 15 RPV longitudinal shell welds due to interference by the core spray piping and feedwater spargers.
These physical obstructions limit the coverage to less than essentially 100 percent of the required volume. To achieve complete coverage, design modifications would be required to increase access from the inside surface.
As a result of the augmented volumetric examination requirements, licensees must make a reasonable effort to maximize examination coverage of their RPV welds. In cases where examination coverage from the inside surface is inadequate, examination from the outside surface using manual inspection techniques may be an option. However, extensive surface preparation (removal of insulation, weld preparation and scaffolding erection) would be required for the licensee to perform supplemental examinations from the outside surface. The effort expended to obtain access to the examination surface from the outside surface would result in considerable radiological exposure that is not warranted for the additional volumetric coverage that may be achieved. Therefore, imposition of this requirement would result in a significant hardship without a compensating increase in the level of quality and safety.
TVA justifies their proposed alternative weld examination on grounds that 12 of the 15 RPV longitudinal shell welds received essentially 100 percent coverage using the ultrasonic examination technique while the remaining three welds (V-3-A, V-3-B, and V-3-C) received coverage to the maximum extent possible. The lowest coverage obtained was still greater than 76 percent. Based on the volumetric examination coverage attained, the fact that no reportable findings resulted from the inspections that were performed, and the low likelihood of significant fatigue damage, the staff concludes that any significant patterns of degradation, if present, would have been detected and that the examinations performed provide reasonable assurance of the continued structural integrity of the subject welds.
5.0 CONCLUSION
The staff concludes that the licensees proposed alternative of conducting the augmented examination of the subject RPV welds to the maximum extent possible provides an acceptable level of safety and quality. Therefore, the licensee's proposed alternative is authorized pursuant to 10 CFR 50.55a(a)(3)(i) and 10 CFR50.55a(g)(6)(ii)(A)(5). All other requirements of the ASME Code,Section XI for which relief has not been specifically requested remain applicable, including third party review by the Authorized Nuclear Inservice Inspector. Relief is authorized for the above requested one-time augmented inspection as required by 10 CFR 50.55a(g)(6)(ii)(A)(2).
Principal contributors: Atif A. Shaikh Thomas McLellan
Karl W. Singer Page 1 of 2 Browns Ferry Nuclear Plant cc:
Mr. Ashok S. Bhatnagar, Senior Vice President Nuclear Operations Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Mr. Larry S. Bryant, Vice President Nuclear Engineering & Technical Services Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Brian OGrady, Site Vice President Browns Ferry Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Decatur, AL 35609 Mr. Robert J. Beecken, Vice President Nuclear Support Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 General Counsel Tennessee Valley Authority ET 11A 400 West Summit Hill Drive Knoxville, TN 37902 Mr. John C. Fornicola, Manager Nuclear Assurance and Licensing Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Mr. Bruce Aukland, Plant Manager Browns Ferry Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Decatur, AL 35609 Mr. Masoud Bajestani, Vice President Browns Ferry Unit 1 Restart Browns Ferry Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Decatur, AL 35609 Mr. Robert G. Jones, General Manager Browns Ferry Site Operations Browns Ferry Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Decatur, AL 35609 Mr. Larry S. Mellen Browns Ferry Unit 1 Project Engineer Division of Reactor Projects, Branch 6 U.S. Nuclear Regulatory Commission 61 Forsyth Street, SW.
Suite 23T85 Atlanta, GA 30303-8931 Mr. Glenn W. Morris, Manager Corporate Nuclear Licensing and Industry Affairs Tennessee Valley Authority 4X Blue Ridge 1101 Market Street Chattanooga, TN 37402-2801 Mr. William D. Crouch, Manager Licensing and Industry Affairs Browns Ferry Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Decatur, AL 35609 Senior Resident Inspector U.S. Nuclear Regulatory Commission Browns Ferry Nuclear Plant 10833 Shaw Road Athens, AL 35611-6970 State Health Officer Alabama Dept. of Public Health RSA Tower - Administration Suite 1552 P.O. Box 303017 Montgomery, AL 36130-3017 Chairman Limestone County Commission 310 West Washington Street Athens, AL 35611