ML070851008
| ML070851008 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 04/30/2007 |
| From: | Hiltz T NRC/NRR/ADRO/DORL/LPLIV |
| To: | Sheppard J South Texas |
| Thadani M, NRR/DORL, 415-1476 | |
| References | |
| TAC MD1064 | |
| Download: ML070851008 (9) | |
Text
April 30, 2007 Mr. James J. Sheppard President and Chief Executive Officer STP Nuclear Operating Company South Texas Project Electric Generating Station P. O. Box 289 Wadsworth, TX 77483
SUBJECT:
SOUTH TEXAS PROJECT, UNIT 1 - RELIEF REQUEST NO. RR-ENG-2-44 ON DEFERRAL OF CODE REPAIR OF ESSENTIAL COOLING WATER SYSTEM INDICATION (TAC NO. MD1064)
Dear Mr. Sheppard:
By letter dated March 23, 2006, STP Nuclear Operating Company (the licensee) submitted Relief Request RR-ENG-2-44 requesting deferral of code repairs of two indications of through-wall dealloying were found during periodic examinations of essential cooling water (ECW) piping in a piping component of the ECW system Class 3 piping of South Texas Project, Unit 1 (STP). The licensee requested relief from certain requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, Subsection IWA-250(a)(3). Specifically, the licensee requests that a code repair of the through-wall flaw at the location may be deferred until the next outage of sufficient duration but no later than the next refueling outage because of the impracticality of performing the repair during operation.
Based on the review of the information provided in the licensees submittal, the Nuclear Regulatory Commission (NRC) staff concludes that the Code required repair was impractical, and that alternative to defer Code repair was acceptable. Furthermore, the NRC staff concludes that the proposed alternative to defer Code repair provides reasonable assurance of structural integrity during the interim period prior to the next refueling outage based on the provisions of Generic Letter 90-05, Guidance for Performing Temporary Non-Code Repair of ASME Code Class 1, 2, and 3 Piping. Therefore, pursuant to Title 10 of the Code of Federal Regulations (10 CFR), paragraph 50.55a(g)(6)(i) the deferral of permanent code repair for the STP, Unit 1, to an outage of sufficient duration, but not later than the next refueling outage is granted.
Granting relief pursuant to 10 CFR 50.55a(g)(6)(i) 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 upon the licensee that could result if the requirements were imposed on the facility.
J. J. Sheppard All other ASME Code,Section XI, requirements for which relief was not specifically requested and authorized herein by the NRC staff remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector. The NRC staffs safety evaluation is enclosed.
Sincerely,
/RA/
Thomas G. Hiltz, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-498
Enclosure:
Safety Evaluation cc: See next page
- No significant change to SE input OFFICE NRR/LPL4/PM NRR/LPL4/PM NRR/LPL4/LA NRR/CSGB/BC*
OGC NRR/LPL4/BC NAME JEargle MThadani LFeizollahi AHiser JBonanno THiltz DATE NA 4/25/07 4/24/07 3/22/07 4/27/07 4/30/07
March 2007 South Texas Project, Units 1 & 2 cc:
Senior Resident Inspector U.S. Nuclear Regulatory Commission P.O. Box 289 Wadsworth, TX 77483 C. M. Canady City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704 J. J. Nesrsta/R. K. Temple E. Alercon/Kevin Pollo City Public Service Board P.O. Box 1771 San Antonio, TX 78296 INPO Records Center 700 Galleria Parkway Atlanta, GA 30339-3064 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011 Steve Winn/Christie Jacobs Eddy Daniels/Marty Ryan NRC Energy, Inc.
211 Carnegie Center Princeton, NJ 08540 Judge, Matagorda County Matagorda County Courthouse 1700 Seventh Street Bay City, TX 77414 A. H. Gutterman, Esq.
Morgan, Lewis & Bockius 1111 Pennsylvania Avenue, NW Washington, DC 20004 E. D. Halpin Site Vice President STP Nuclear Operating Company South Texas Project Electric Generating Station P.O. Box 289 Wadsworth, TX 77483 S. M. Head, Manager, Licensing STP Nuclear Operating Company P.O. Box 289, Mail Code: N5014 Wadsworth, TX 77483 C. T. Bowman General Manager, Oversight STP Nuclear Operating Company P.O Box 389 Wadsworth, TX 77483 Marilyn Kistler Sr. Staff Specialist, Licensing STP Nuclear Operating Company P.O. Box 289, Mail Code 5014 Wadsworth, TX 77483 Environmental and Natural Resources Policy Director P.O. Box 12428 Austin, TX 78711-3189 Jon C. Wood Cox, Smith, & Matthews 112 East Pecan, Suite 1800 San Antonio, TX 78205 Director Division of Compliance & Inspection Bureau of Radiation Control Texas Department of State Health Services 1100 West 49th Street Austin, TX 78756 South Texas Project, Units 1 & 2 March 2007 cc:
Mr. Ted Enos 4200 South Hulen Suite 422 Ft. Worth, TX 76109 Brian Almon Public Utility Commission William B. Travis Building P.O. Box 13326 1701 North Congress Avenue Austin, TX 78701-3326 Susan M. Jablonski Office of Permitting, Remediation and Registration Texas Commission on Environmental Quality MC-122 P.O. Box 13087 Austin, TX 78711-3087 Mr. Glenn Adler Senior Research Analyst Service Employees International Union 1313 L Street NW Washington, DC 20005 Ken Coates Plant General Manager STP Nuclear Operating Company South Texas Project Electric Generating Station P.O. Box 289 Wadsworth, TX 77483 Mr. Terry Parks, Chief Inspector Texas Department of Licensing and Regulation Boiler Division P.O. Box 12157 Austin, TX 78711
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST NO. RR-ENG-2-44 STP NUCLEAR OPERATING COMPANY SOUTH TEXAS PROJECT, UNIT 1 DOCKET NO. 50-498
1.0 INTRODUCTION
By letter dated March 23, 2006 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML060900417), STP Nuclear Operating Company (the licensee) submitted Relief Request No. RR-ENG-2-44 requesting deferral of code repairs of two indications of throughwall dealloying found in a piping component of the Essential Cooling Water (ECW) system of South Texas Project (STP), Unit 1. The indications were believed to be associated with the effect of dealloying of the aluminum-bronze piping material.
The licensee stated that it is impractical to perform an American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code repair while the unit is operating and there is reasonable assurance of structural integrity with the existing indications for the unit to continue operation until the next refueling outage subject to a proposed augmented inspection program for the piping component. The Nuclear Regulatory Commission (NRC) staff has reviewed the licensees request for relief pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(6)(i) based on the provisions of Generic Letter 90-05 Guidance for Performing Temporary Non-Code Repair of ASME Code Class 1, 2, and 3 Piping.
2.0 REGULATORY REQUIREMENTS Paragraph 50.55a(g) of 10 CFR requires that inservice inspection (ISI) of ASME Code Class 1, 2, and 3 components be performed in accordance with Section XI of the ASME Code and applicable addenda, except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i).
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 (ISI) of Nuclear Power Plant Components, to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulation at 10 CFR 50.55a(g)(4)(i) requires that ISI components and system pressure tests conducted during the initial 10-year inspection interval must comply with the requirements in the latest edition and addenda of Section XI of the ASME Code, incorporated by reference in 10 CFR 50.55(b) 12 months before the date of the operating license, subject to the limitations and modifications listed therein. The regulation at 10 CFR 50.55a(g)(4)(ii) requires that ISI components and system pressure tests conducted during successive 10-year intervals must comply with the requirement of the latest edition and addenda of Section XI of the ASME Code, incorporated by reference in 10 CFR 50.55a(b) 12 months before the start of of the 120-month inspection interval, subject to the limitations and modifications listed therein. The ISI Code of Record for the current inspection interval for STP, Unit 1, is the 1989 Edition of the ASME Code,Section XI. However, Generic Letter 90-05 provides guidance for performing temporary non-code repair of ASME Code, Class 1, 2, and 3 piping.
3.0 TECHNICAL EVALUATION
System/Component(s) for which Relief is Requested Flange on the ECW line (EW-1383-WT3 ) 10 inches immediately upstream from cross-tie valve 1-EW-0276 connecting essential chillers 11C/12C and 11A/12A.
Description of the Flaw Two indications of through-wall dealloying were found during periodic examination of ECW large bore piping on a flange of the Unit 1 ECW line immediately upstream from cross-tie valve 1-EW-0276 connecting essential chillers 11C/12C and 11A/12A. The flaws appeared to be porous, dealloyed pipe material, with no measurable leakage. The dealloying indications were several localized small spots in two groups showing residue buildup with one group arrayed in a linear configuration.
ASME Code Requirement The requirements of the 1998 Edition, ASME Code,Section XI, stated under Subsection IWA-5250(a)(3) in regard to corrective measures for the source of leakage detected during a system pressure test is that repairs or replacement of components be performed in accordance with IWA-4000 or IWA-7000, respectively. However, any repair or replacement in accordance with the ASME Code would necessitate a plant shutdown. Temporary non-code repairs are not permitted on ASME Code piping without prior relief from the NRC.
Licensees Request for Relief Relief is requested from the requirements of ASME Code,Section XI, Subsection IWA-5250(a)(3) so that a code repair of the through-wall flaw at the location may be deferred until the next outage of sufficient duration but no later than the next refueling outage.
Licensees Basis for Requesting Relief In accordance with Generic Letter 90-05, a code repair is required for Class 1, 2, and 3 piping unless specific written relief is granted by the NRC. However, a relief from the ASME Code requirement for a repair may be granted by the NRC on a case-by-case basis under the following circumstances.
The location of the flaw in a Class 3 piping cannot be isolated to perform a code repair.
Performance of a code repair necessitates a plant shutdown due to time constraint to complete the repair within the allowed outage time for ECW system under Technical Specifications.
Assessing the structural integrity of the flawed piping by flaw evaluation methodology of the Generic Letter and assessing the overall degradation of the system by an augmented inspection program.
Evaluation of potential system interactions due to flooding, water spray on equipment, and loss of flow to the system.
4.0 NRC STAFF EVALUATION The NRC staff has evaluated the licensees request for relief in accordance with the guidelines of Generic Letter 90-05. The staff determined that the repair of dealloying indications would be considered impractical since the flaws in the subject piping components detected during operation cannot be isolated to complete a code repair within the time period permitted by the limiting condition for operation of the affected system as specified in the plant Technical Specifications. The ASME Code repair, therefore, would necessitate a plant shutdown.
Pursuant to 10 CFR 50.55a(g)(6)(i), the staff has evaluated the request for relief for a temporary non-code repair. In assessing the structural integrity of the flawed piping, the staff verified the licensees flaw evaluation approach as suggested in Generic Letter 90-05 under through-wall flaw that the flaw is stable under the operating loads and there is an adequate safety margin for various loading conditions. The staff reviewed the consequences of potential system interactions due to flooding, spray on equipment, and loss of flow to the system and found them to be minimal. The licensee has committed to perform augmented inspection of the component once a month to detect any change in the size of the flaw or leakage. If significant changes in the condition of the dealloyed area are observed in the augmented inspection, structural integrity and the inspection frequency will be reassessed. The licensee has further committed to repair the flaws should there be an outage of sufficient duration but no later than the next refueling outage. Since there is no measurable leakage from the dealloying indications, the staff has authorized deferral of the ASME Code repair to the outage as stated above under the guidelines of Generic Letter 90-05.
5.0 CONCLUSION
The staff concludes that for the indication of through-wall dealloying in aluminum-bronze piping components, impracticality exists in performing an ASME Code repair while the unit is operating based on the guidance of Generic Letter 90-05. The licensee has assessed structural integrity of the piping components containing flaws, which indicates that adequate safety margins remain under various loading conditions based on a flaw evaluation. The licensee has further implemented an augmented inspection program to detect any change to the size of the flaw and leakage. In granting relief requested in the licensees Relief Request RR-ENG-2-44 under the provisions of Generic Letter 90-05, the NRC staff authorizes temporary non-code repair of the components containing flaws for STP, Unit 1, to continue operation and deferral of permanent ASME Code repair to an outage of sufficient duration but no later than the next refueling outage. Granting relief pursuant to 10 CFR 50.55a(g)(6)(i) 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 upon the licensee that could result if the requirements were imposed on the facility.
All other ASME Code,Section XI, requirements for which relief was not specifically requested and authorized herein by the NRC staff remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: P.Patnaik Date: April 30, 2007