ML12139A131

South Texas Project, Units 1 & 2, Response to Request for Additional Information (RAI) 3.2.2.1-1a for the South Texas Project License Renewal Application (TAC ME4936 and ME4937)

ML12139A131
Person / Time
Site:	South Texas
Issue date:	05/14/2012
From:	Rencurrel D W South Texas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NOC-AE-12002855, TAC ME4936, TAC ME4937
Download: ML12139A131 (10)

Text

Nuclear Operating CompanySouth Texas Project Electric Generating Station P.O Box 289 Wadsworth. Texas 77483 -May 14, 2012NOC-AE-1200285510 CFR 54STI: 33547424File: G25U. S. Nuclear Regulatory CommissionAttention: Document Control DeskOne White Flint North11555 Rockville PikeRockville, MD 20852-2738South Texas ProjectUnits 1 and 2Docket Nos. STN 50-498, STN 50-499Response to Requests for Additional Information(RAI) 3.2.2.1-1a for theSouth Texas Project License Renewal Application (TAC Nos. ME4936 and ME4937)

References:

1. STPNOC letter dated October 25, 2010, from G. T. Powell to NRC DocumentControl Desk, "License Renewal Application" (NOC-AE-10002607)(ML1 03010257)2. NRC letter dated May 14, 2012, "Requests for Additional Information for theReview of the South Texas Project, Units 1 and 2, License Renewal Application-Aging Management, Set 18 (TAC Nos. ME4936 and ME4937)"(ML1 2124A094)By Reference 1, STP Nuclear Operating Company (STPNOC) submitted a License RenewalApplication (LRA) for South Texas Project (STP) Units 1 and 2. By Reference 2, STPNOCreceived RAI 3.2.2.1-1a. The response is provided in Enclosure 1 to this letter.One new regulatory commitment is added to Table A4-1 of the LRA and is provided inEnclosure 2 to this letter. There are no other regulatory commitments in this letter.Should you have any questions regarding this letter, please contact either Arden Aldridge, STPLicense Renewal Project Lead, at (361) 972-8243 or Ken Taplett, STP License Renewal Projectregulatory point-of-contact, at (361) 972-8416.I declare under penalty of perjury that the foregoing is true and correct.Executed onDateW. Renr relChief Nuclear OfficerKJT

Enclosures:

1. STPNOC Response to RAI 3.2.2.1-1a2. New Regulatory CommitmentA~7 NOC-AE-12002855Page 2cc:(paper copy)(electronic copy)Regional Administrator, Region IVU. S. Nuclear Regulatory Commission1600 East Lamar BoulevardArlington, Texas 76011-4511Balwant K. SingalSenior Project ManagerU.S. Nuclear Regulatory CommissionOne White Flint North (MS 8B1)11555 Rockville PikeRockville, MD 20852Senior Resident InspectorU. S. Nuclear Regulatory CommissionP. O. Box 289, Mail Code: MN116Wadsworth, TX 77483C. M. CanadyCity of AustinElectric Utility Department721 Barton Springs RoadAustin, TX 78704John W. DailyLicense Renewal Project Manager (Safety)U.S. Nuclear Regulatory CommissionOne White Flint North (MS 011-Fl)Washington, DC 20555-0001Tam TranLicense Renewal Project Manager(Environmental)U. S. Nuclear Regulatory CommissionOne White Flint North (MS O11F01)Washington, DC 20555-0001A. H. Gutterman, EsquireKathryn M. Sutton, EsquireMorgan, Lewis & Bockius, LLPJohn RaganChris O'HaraJim von SuskilNRG South Texas LPKevin PolioRichard PenaCity Public ServicePeter NemethCrain Caton & James, P.C.C. MeleCity of AustinRichard A. RatliffAlice RogersTexas Department of State Health ServicesBalwant K. SingalJohn W. DailyTam TranU. S. Nuclear Regulatory Commission NOC-AE-12002855Enclosure 1Enclosure ISTPNOC Response to RAI 3.2.2.1-1a NOC-AE-1 2002855Page 1 of 5SOUTH TEXAS PROJECT, UNITS 1 AND 2REQUEST FOR ADDITIONAL INFORMATIONAGING MANAGEMENT, SET 18(TAC NOS. ME4936 AND ME4937)Instances of Recurrent Reactor Coolant Leakage (019)NRC RAI 3.2.2.1-1a

Background:

By letter dated September 22, 2011, the staff issued RAI 3.2.2.1-1 requesting that theapplicant state why the stainless steel closure bolting exposed to borated water leakage inLRA Table 3.2.2-4, Safety Injection System, was not managed for cracking. In its responsedated November 21, 2011, the applicant stated that the bolting was in an ambient temperatureless than 140°F; therefore, stress corrosion cracking is not an applicable aging effect.NRC Inspection Report No. 05000449/2011005 dated February 13, 2012 describes safetyinjection (SI) system hot leg check valve 1N122XSI001OA, on which a seal cap enclosure hadbeen installed in 1997 due to reactor coolant leakage from the body to bonnet gasket. Theenclosure surrounds the valve bolting, preventing direct inspection. The NRC inspection reportalso cites multiple occasions of leakage from the seal cap enclosure from 1997 to 2011,indicating that the leak from the bolted connection inside the enclosure was ongoing.Another instance of borated water leakage is described in the "operating experience" programelement of LRA Section B2.1.4, "Boric Acid Corrosion," which states that recurring coolantleakage in reactor coolant pump 2C resulted in the replacement of seal housing bolts in 2004and 2009. The LRA also states that disassembly of this pump was scheduled for RefuelingOutage 2RE15 in October 2011 to perform flatness checks of the seal.Issue:1. Given the multiple instances of reactor coolant leakage from the seal cap enclosure ofSI system hot leg check valve 1N122XSIOO1OA, the stainless steel bolting within theenclosure may be submerged in a reactor coolant environment with a temperaturegreater than 1400F. The staff noted that the environment within the enclosure may notbe sufficiently controlled for oxygen and other contaminants to preclude stresscorrosion cracking. The LRA does not contain an AMR item to address the submergedenvironment and the potential for stress corrosion cracking. It is unclear to the staffhow bolting within this and other seal cap enclosures will be age managed, since directinspection is not possible.2. Regarding the recurring borated water leakage from reactor coolant pump 2C, the staffdoes not have sufficient information to determine if the Boric Acid Corrosion program iseffective at preventing recurring leakages. NOC-AE-12002855Page 2 of 5Request:1. For all instances where pressure-retaining bolting is surrounded by seal capenclosures:a. Describe the bolting alloy and the leaking water environment (i.e., reactorcoolant, secondary water).b. Add aging management review (AMR) items for the aging management of thebolting for loss of material, loss of preload, and cracking due to stress corrosioncracking, as appropriate, in the submerged environment. Provide technicaljustification for any cases where cracking due to stress corrosion cracking is notincluded as an applicable aging effect.c. If the aging management approach in item (b) does not include direct inspectionof the bolting, provide technical justification for how the aging effects will beeffectively managed during the period of extended operation.2. Describe the results and any identified corrective actions from the reactor coolant pump2C seal flatness checks to demonstrate the effectiveness of the Boric Acid Corrosionprogram.STPNOC Response:la. The bolting alloy for SI system hot leg check valve 1N122XSI001OA and the otherinstances where pressure-retaining bolting is surrounded by seal cap enclosures is A-286(SA-453 Gr. 660). The leaking water environment is reactor coolant. The material is aniron-based and precipitation hardened high strength material. This material has a highchrome and nickel content and is specifically designed to be resistant to boric acidcorrosion. The systems where seal cap enclosures currently exist are the Safety InjectionSystem and the Chemical and Volume Control System. Seal cap enclosures are currentlyinstalled on Safety Injection System Check Valve SI0010A in Unit 2 and on ChemicalVolume Control System Check Valves CV0001, CV0002, CV0004, and CV0005 in bothUnit 1 and Unit 2.The LRA Aging Management Review (AMR) tables that show thematerial and environments for the affected systems and components are provided below. NOC-AE-1 2002855Page 3 of 5Table 3.2.2-4 Engineered Safety Features -Summary of Aging ManagementEvaluation -Safety Injection SystemComponent Intended Material Environment Aging Effect Aging NUREG- Table I NotesType Function Requiring Management 1801 ItemManagement Program Vol. 2ItemClosure LBS, PB, Carbon Borated Water Loss of material Boric Acid V.E-2 3.2.1.45 ABolting SIA Steel Leakage (Ext) Corrosion (B2.1.4)Closure LBS, PB, Carbon Plant Indoor Loss of material Bolting Integrity V.E-4 3.2.1.23 BBolting SIA Steel Air (Ext) (B2.1.7)Closure LBS, PB, Carbon Plant Indoor Loss of preload Bolting Integrity V.E-5 3.2.1.24 BBolting SIA Steel Air (Ext) (B2.1.7)Valve PB Stainless Reactor Cracking ASME Section Xl IV.C2-5 3.1.1.68 ASteel Coolant (Int) InserviceInspection,Subsections IWB,IWC, and IWD forClass 1components(B2.1.1) andWater Chemistry(B2.1.2)Valve PB Stainless Reactor Loss of material Water Chemistry IV.C2-15 3.1.1.83 E, 1Steel Coolant (Int) (B2.1.2) and One-Time Inspection(B2.1.16) NOC-AE-12002855Page 4 of 5Table 3.3.2-19 Auxiliary Systems -Summary of Aging Management Evaluation -Chemical and Volume Control SystemComponent Intended Material Environment Aging Effect Aging NUREG- Table I NotesType Function Requiring Management 1801 Vol. ItemManagement Program 2 ItemClosure LBS, SIA Carbon Borated Water Loss of material Boric Acid VII.I-2 3.3.1.89 ABolting Steel Leakage (Ext) Corrosion (B2.1.4)Closure LBS, SIA Carbon Plant Indoor Air Loss of material Bolting Integrity VII.l-4 3.3.1.43 BBolting Steel (Ext) (B2.1.7)Closure LBS, SIA Carbon Plant Indoor Air Loss of preload Bolting Integrity VII.I-5 3.3.1.45 BBolting Steel (Ext) (B2.1.7)Valve PB Stainless Reactor Cracking ASME Section XI IV.C2-5 3.1.1.68 ASteel Coolant (Int) InserviceInspection,Subsections IWB,IWC, and IWD forClass 1components(B2.1.1) andWater Chemistry(B2.1.2)Valve PB Stainless Reactor Loss of material Water Chemistry IV.C2-15 3.1.1.83 E, 2Steel Coolant (Int) (B2.1.2) and One-Time Inspection(B2.1.16)Valve LBS, PB, Stainless Treated Loss of material Water Chemistry VII.El-17 3.3.1.91 E, 2SIA Steel Borated Water (B2.1.2) and One-(Int) Time InspectionS(B2.1.16)Valve LBS, PB, Stainless Treated Cracking Water Chemistry VII.E1-20 3.3.1.90 E, 2SIA Steel Borated Water (B2.1.2) and One-(Int) Time Inspection1 (B2.1.16)1 b. South Texas Project will permanently remove the seal cap enclosures from the affectedcomponents at the next available opportunity. After the seal cap enclosures are removed,the component bolting will be replaced or inspected for intergranular stress corrosioncracking. New LRA Table A4-1 Commitment 43 is provided in Enclosure 2. Therefore, theaging effects and environment for the affected components will be consistent with the AMRtable description in the LRA. No changes to the AMR tables are required.Enclosure 2 provides the line-in of new Commitment 43.lc. The submerged environment associated with the affected components will no longer existafter the seal cap enclosures are permanently removed. The aging effects of the closurebolting of these components will be effectively managed during the period of extendedoperation by the Boric Acid Corrosion and Bolting Integrity Aging Management Programs. NOC-AE-12002855Page 5 of 52. Seal housing leakage for reactor coolant pump 2C was initially identified by the Boric AcidWalkdown Program in 2004. The joint was disassembled and the gasket was replacedwhich stopped the leakage. The seal housing leakage for reactor coolant pump 2C wasagain identified through the Boric Acid Walkdown Program during the Fall 2008 refuelingoutage (2RE13). A monitoring plan for the reactor coolant pump 2C seal housing leakagewas established and permanent repairs were scheduled for the Fall 2011 refueling outage(2RE15). Following a Unit 2 trip in November 2010, the Boric Acid Walkdown Programinspected the seal housing leakage for reactor coolant pump 2C and identified increasedleakage. Following plant pressurization to normal operating temperature and pressure, theleak exceeded predetermined leakage criteria. The plant was depressurized to facilitatecorrective action implementation. The corrective actions were replacement of the reactorcoolant pump seal housing and gasket.The apparent cause of the reactor coolant pump 2C seal housing leakage is deformationand distortion of the #1 seal housing caused by pressure cycles and successiveretightening of the joint. The deformation and distortion interfered with the fit between theseal housing and the thermal barrier, and between the seal housing and the #1 insertsupport. Progression of deformation and distortion over time eventually contributed to aleak path between the seal housing and the thermal barrier.As outlined above, the Boric Acid Walkdown Program effectively identified, evaluated andtracked this joint leakage from initial identification to subsequent correction.The Boric Acid Walkdown Program has not identified any leakage at the seal housing jointof the other seven Reactor Coolant Pumps. NOC-AE-12002855Enclosure 2New Regulatory Commitment NOC-AE-12002855Page 1 of 1A4 LICENSE RENEWAL COMMITMENTSTable A4-1 identifies proposed actions committed to by STPNOC for STP Units 1 and 2 in its License Renewal Application. Theseand other actions are proposed regulatory commitments. This list will be revised, as necessary, in subsequent amendments toreflect changes resulting from NRC questions and STPNOC responses. STPNOC will utilize the STP commitment tracking systemto track regulatory commitments. The Condition Report (CR) number in the Implementation Schedule column of the table is forSTPNOC tracking purposes and is not part of the amended LRA.Table A4-1 License Renewal CommitmentsItem # Commitment LRA ImplementationSection Schedule43 The seal cap enclosures from Unit 2 Safety Iniection System Check Valve SI001OA and from B2.1.7 2012 RefuelingUnit 1 and Unit 2 Chemical Volume Control System Check Valves CV0001, CV0002, CV0004, Outage (Unit 1)0 2013and CV0005 will be permanently removed. After removal of the seal cap enclosures, the Refueling Outagecomponent bolting will be replaced or inspected for intergranular stress corrosion cracking. (Unit 2)CR 12-21155