ML070851008
| ML070851008 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 04/30/2007 |
| From: | Hiltz T G NRC/NRR/ADRO/DORL/LPLIV |
| To: | Sheppard J J South Texas |
| Thadani M C, NRR/DORL, 415-1476 | |
| References | |
| TAC MD1064 | |
| Download: ML070851008 (9) | |
Text
April 30, 2007Mr. James J. SheppardPresident 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 ONDEFERRAL 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) submittedRelief 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 licensee's submittal, the NuclearRegulatory 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-2-All other ASME Code,Section XI, requirements for which relief was not specifically requestedand authorized herein by the NRC staff remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector. The NRC staff's safety evaluation is enclosed.Sincerely,/RA/Thomas G. Hiltz, ChiefPlant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor RegulationDocket No. 50-498
Enclosure:
Safety Evaluation cc: See next page
ML070851008*No significant change to SE inputOFFICENRR/LPL4/PMNRR/LPL4/PMNRR/LPL4/LANRR/CSGB/BC*OGCNRR/LPL4/BCNAMEJEargleMThadaniLFeizollahiAHiserJBonannoTHiltz DATENA4/25/074/24/073/22/074/27/074/30/07 March 2007South Texas Project, Units 1 & 2 cc:Senior Resident Inspector U.S. Nuclear Regulatory Commission P.O. Box 289 Wadsworth, TX 77483C. M. CanadyCity of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704 J. J. Nesrsta/R. K. TempleE. Alercon/Kevin Pollo City Public Service Board P.O. Box 1771 San Antonio, TX 78296INPORecords Center 700 Galleria Parkway Atlanta, GA 30339-3064Regional Administrator, Region IVU.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011Steve Winn/Christie JacobsEddy Daniels/Marty Ryan NRC Energy, Inc.
211 Carnegie Center Princeton, NJ 08540Judge, Matagorda CountyMatagorda County Courthouse 1700 Seventh Street Bay City, TX 77414A. H. Gutterman, Esq.Morgan, Lewis & Bockius 1111 Pennsylvania Avenue, NW Washington, DC 20004E. D. HalpinSite Vice President STP Nuclear Operating Company South Texas Project Electric Generating Station P.O. Box 289 Wadsworth, TX 77483S. M. Head, Manager, LicensingSTP Nuclear Operating Company P.O. Box 289, Mail Code: N5014 Wadsworth, TX 77483C. T. BowmanGeneral Manager, Oversight STP Nuclear Operating Company P.O Box 389 Wadsworth, TX 77483Marilyn KistlerSr. Staff Specialist, Licensing STP Nuclear Operating Company P.O. Box 289, Mail Code 5014 Wadsworth, TX 77483Environmental and Natural ResourcesPolicy Director P.O. Box 12428 Austin, TX 78711-3189Jon C. WoodCox, Smith, & Matthews 112 East Pecan, Suite 1800 San Antonio, TX 78205DirectorDivision of Compliance & Inspection Bureau of Radiation Control Texas Department of State Health Services 1100 West 49th Street Austin, TX 78756South Texas Project, Units 1 & 2 March 2007 cc:Mr. Ted Enos 4200 South Hulen Suite 422 Ft. Worth, TX 76109Brian AlmonPublic Utility Commission William B. Travis Building P.O. Box 13326 1701 North Congress Avenue Austin, TX 78701-3326Susan M. JablonskiOffice of Permitting, Remediation and Registration Texas Commission on Environmental Quality MC-122 P.O. Box 13087 Austin, TX 78711-3087Mr. Glenn AdlerSenior Research Analyst Service Employees International Union 1313 L Street NW Washington, DC 20005Ken CoatesPlant General Manager STP Nuclear Operating Company South Texas Project Electric Generating Station P.O. Box 289 Wadsworth, TX 77483Mr. Terry Parks, Chief InspectorTexas Department of Licensing and Regulation Boiler Division P.O. Box 12157 Austin, TX 78711 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATIONRELIEF REQUEST NO. RR-ENG-2-44STP NUCLEAR OPERATING COMPANYSOUTH TEXAS PROJECT, UNIT 1DOCKET NO. 50-49
81.0INTRODUCTION
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 MechanicalEngineers (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 licensee's request for relief pursuant to Title 10 of the Code of FederalRegulations (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."2.0REGULATORY REQUIREMENTSParagraph 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 (includingsupports) 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 limitationsand 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.
3.0TECHNICAL EVALUATION
System/Component(s) for which Relief is RequestedFlange 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 FlawTwo indications of through-wall dealloying were found during periodic examination of ECWlarge 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 RequirementThe 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.Licensee's Request for ReliefRelief 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.Licensee's Basis for Requesting Relief In accordance with Generic Letter 90-05, a code repair is required for Class 1, 2, and 3 pipingunless 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 coderepair.*Performance of a code repair necessitates a plant shutdown due to timeconstraint 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 evaluationmethodology 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 onequipment, and loss of flow to the system. 4.0NRC STAFF EVALUATIONThe NRC staff has evaluated the licensee's request for relief in accordance with the guidelinesof 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 licensee's 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.
5.0CONCLUSION
The staff concludes that for the indication of through-wall dealloying in aluminum-bronze pipingcomponents, 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 licensee's 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 andwill 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 requestedand authorized herein by the NRC staff remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.Principal Contributor: P.PatnaikDate: April 30, 2007