ML050610679
| ML050610679 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 03/07/2005 |
| From: | Pickett D NRC/NRR/DLPM/LPD2 |
| To: | Singer K Tennessee Valley Authority |
| Pickett D, NRR/DLPM, 415-1364 | |
| References | |
| TAC MC5368 | |
| Download: ML050610679 (8) | |
Text
March 7, 2005 Mr. Karl W. Singer Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, Tennessee 37402-2801
SUBJECT:
WATTS BAR NUCLEAR PLANT, UNIT 1 REQUEST TO USE BAR-LOCK MECHANICAL COUPLER FOR SPLICING REINFORCING BARS IN THE SHIELD BUILDING (TAC NO. MC5368) (TS-04-18)
Dear Mr. Singer:
By letter dated December 9, 2004 (WBN-TS-04-18), pursuant to Title 10 of the Code of Federal Regulations Section 50.90, Tennessee Valley Authority (TVA) requested an amendment to Watts Bar Nuclear Plant (WBN) license NPF-90. The proposed amendment would revise the WBN Updated Final Safety Analysis Report to permit the use of an alternate methodology for reinforcing bar (rebar) splicing. The change in methodology applies to restoration of the concrete shield building dome as part of the steam generator replacement project for Unit 1 scheduled for the fall of 2006. The alternate methodology uses a Bar-Lock mechanical coupler for splicing rebar in lieu of the Cadweld splice used during the original design and construction of the plant. TVA indicated its preference to use the Bar-Lock mechanical splice over the Cadweld splice because it is easier to install, requires no special equipment and rebar preparation, and requires minimal operator training. TVA also requested that the staff allow the use of the Bar-Lock coupler system without a prequalification test program because the system had been qualified for use in a similar application at the Sequoyah Nuclear Plant (SQN).
Based upon the our review of the amendment application and subsequent discussions with your staff, we have concluded that the request to use the Bar-Lock coupler system cannot be approved without a prequalification test program. As discussed in the attached safety evaluation, we have concluded that the essential variables in the Bar-Lock coupler system to be used at WBN are not identical to those used at SQN, and, therefore, a new prequalification test program will be required for WBN.
Your staff has previously been informed of this decision and, as a result, it is our understanding that TVA has agreed to perform a prequalification test program similar to that performed at
SQN. Your staff was also informed of the need to document a summary of the test results and that our review of the proposed amendment will be contingent upon these results.
Sincerely,
/RA/
Douglas V. Pickett, Senior Project Manager, Section 2 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-390
Enclosure:
As stated cc w/enclosure: See next page
SQN. Your staff was also informed of the need to document a summary of the test results and that our review of the proposed amendment will be contingent upon these results.
Sincerely,
/RA/
Douglas V. Pickett, Senior Project Manager, Section 2 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-390
Enclosure:
As stated cc w/enclosure: See next page DISTRIBUTION:
PUBLIC PDII-2 r/f KManoly JMa OGC ACRS MMarshall BClayton DPickett SCahill, R2 ADAMS ACCESSION NO. ML050610679 NRR-106 OFFICE PM:LPDII-2 LA:LPDII-2 SC:EMEB SC:LPDII-2 NAME DPickett BClayton KManoly MMarshall DATE 3/4/05 3/3/05 02/ 24 /05 3/7/05 OFFICIAL RECORD COPY
Mr. Karl W. Singer Tennessee Valley Authority WATTS BAR 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, General Manager Nuclear Engineering Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Mr. William R. Lagergren Site Vice President Watts Bar Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Spring City, TN 37381 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. Fredrick C. Mashburn Senior Program Manager Nuclear Licensing Tennessee Valley Authority 4X Blue Ridge 1101 Market Street Chattanooga, TN 37402-2801 Mr. Paul L. Pace, Manager Licensing and Industry Affairs Watts Bar Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Spring City, TN 37381 Mr. Jay Laughlin, Plant Manager Watts Bar Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Spring City, TN 37381 Senior Resident Inspector Watts Bar Nuclear Plant U.S. Nuclear Regulatory Commission 1260 Nuclear Plant Road Spring City, TN 37381 County Executive Rhea County Courthouse 375 Church Street Suite 215 Dayton, TN 37321 County Mayor P. O. Box 156 Decatur, TN 37322 Mr. Lawrence E. Nanney, Director Division of Radiological Health Dept. of Environment & Conservation Third Floor, L and C Annex 401 Church Street Nashville, TN 37243-1532 Ms. Ann P. Harris 341 Swing Loop Road Rockwood, Tennessee 37854
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT, UNIT 1 DOCKET NO. 50-390
1.0 INTRODUCTION
By letter dated December 9, 2004, pursuant to Title 10, Code of Federal Regulations (10 CFR)
Section 50.90, Tennessee Valley Authority (TVA, the licensee) requested an amendment to Watts Bar Nuclear Plant (WBN) license NPF-90. The proposed request provides a revision to the WBN Updated Final Safety Analysis Report to permit the use of an alternate methodology for reinforcing bar (rebar) splicing. The change in methodology applies to restoration of the concrete shield building dome as part of the steam generator replacement project for Unit 1 scheduled for the fall of 2006. The alternate methodology uses a Bar-Lock mechanical coupler for splicing rebars in lieu of the Cadweld splice used during the original design and construction of the plant. TVA indicated its preference to use the Bar-Lock mechanical splice over the Cadweld splice because it is easier to install, requires no special equipment and rebar preparation, and requires minimal operator training. TVA also requested that the staff allow the use of the Bar-Lock coupler system without a prequalification test program because the system had been qualified for a similar application at the Sequoyah Nuclear Plant (SQN), Unit 1.
The U.S. Nuclear Regulatory Commission (NRC) approved the Bar-Lock coupler system for use in the shield building restoration at SQN. The approval was based on the licensees application dated March 18, 2002, along with their letter dated December 10, 2002, which responded to our request for additional information. The approval was limited to SQNs specific request and was not applicable to other plants.
2.0 EVALUATION The staffs approval of TVAs request to use the Bar-Lock coupler system at SQN was based on satisfactory implementation of the following:
1.
Requirements of 10 CFR Part 50, Appendix B, were applicable to the design, purchase, fabrication, handling, shipping, storage, inspection, testing, and installation of the Bar-Lock mechanical couplers.
2.
TVA had reviewed and approved Bechtels Sequoyah Steam Generator Replacement Project Nuclear Quality Assurance (QA) Manual. The policies in this manual correspond to each of the 18 criteria of 10 CFR Part 50, Appendix B, and met the requirements of American National Standards Institute (ANSI) N45.2 and N45.2 series standards and QA related NRC regulatory guides.
Bechtel, in its role as a contractor to TVA, imposed the applicable 10 CFR Part 50, Appendix B requirements, along with the technical and document submittal requirements on the subcontractors involved in the material supply, fabrication, and testing of the rebar and Bar-Lock couplers. Bechtel reviewed the quality programs for the rebar supplier (Consolidated Power Supply), the manufacturer of the Bar-Lock couplers (Valley Machining ), Idaho National Engineering and Environmental Laboratory (INEEL), and, where appropriate, required changes to these programs to bring them into compliance with the requirements of 10 CFR Part 50, Appendix B.
3.
Bechtel witnessed and verified implementation of the Bar-Lock manufacturing quality control process and procedures for compliance with the applicable provisions of ANSI/American Society of Mechanical Engineers (ASME) document N45.2.
4.
Bechtel and INEEL developed and performed an independent mechanical testing and analysis program to assess the mechanical performance characteristics of the Bar-Lock coupler system using the qualification criteria of ASME Section III, Division 2, CC-4333, as a standard of reference. The test program demonstrated that the mechanical properties of the Bar-Lock coupler system met the ASME Code and NRC requirements.
The staff also reviewed the test program for SQN. Bechtel/INEEL performed static tensile tests for 40 couplers with #6 rebars and 40 couplers with #8 rebars. Bechtel/INEEL also performed cyclic tests for 40 couplers with #6 rebars and 40 couplers with #8 rebars. The test results indicated that the 160 individual coupler specimens and the relevant specimen sample set averages met the ASME Code, Section CC-4333.2.3 requirements.
ASME Section III, Division 2, CC-4333.4, Initial Qualification Tests, states that the qualification splices shall be made using rebar identical to that used in the structure. CC-4333.2.4, Essential Variables, states that the qualification test must be completely re-conducted when any of the essential variables are not maintained, such as a change in torque or in thread geometry for taper threaded splices. These requirements ensure that the actual splice system to be used in a structure is nearly identical to the one that passed the qualification test, and any change of an essential variable in a system prompts a need for requalification.
The Bar-Lock coupler system consists of two pieces of rebars joined by a coupler barrel and tightened by lockshear bolts through torque and with serrated rails as inserts between the rebars and the barrel. The coupler barrel, lockshear bolts, serrated rails, and rebars are elements that influence and contribute to the performance of the Bar-Lock coupler system. The purpose of the qualification test for the Bar-Lock coupler system is to demonstrate that the entire assembly containing these elements can transfer the force from one rebar to the other, through the coupler, in a desirable manner as specified in the ASME Code, Division 2, CC-4333.2.3 requirements. Since the material and geometry of the rebars, coupler barrels, lockshear bolts, and serrated rails to be used in the shield building at WBN would not be identical to those used at SQN, the Bar-Lock coupler system to be used at WBN would require a new qualification test program. The staff considers the rebar, coupler, lockshear bolt, serrated rail, and torque to be essential variables for the Bar-Lock coupler system. Therefore, any change in one of the essential variables prompts a need for requalification of the Bar-Lock coupler system. During discussions with the licensee, TVA stated that it planned to use the leftover couplers from SQN for WBN. The staff does not object to the use of the leftover couplers, however, these couplers will have to be requalified as a new system, as well as new couplers intended for use with the new rebars.
3.0 CONCLUSION
Based upon the staffs review as discussed above, the staff concludes that the licensees request to use the Bar-Lock coupler system cannot be approved without a prequalification test program. A prequalification test program, similar to that performed for SQN, will be required.
The test program should be conducted in accordance with the requirements specified in ASME Code,Section III, Division 2, CC-4333, Mechanical Splices. Requirements of 10 CFR Part 50, Appendix B, are applicable to the design, purchase, fabrication, handling, shipping, storage, inspection, testing, and installation of the Bar-Lock mechanical couplers. TVA should also commit to the same QA Manual it used at SQN for WBN, and require QA programs and activities at the same level it had committed at SQN.
The staff will resume its review of the licensees amendment request to use the Bar-Lock coupler system upon successful completion of a prequalification test program and submittal of the test results.
Principal Contributor: John Ma Date: March 7, 2005