ML12097A064
| ML12097A064 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 03/28/2012 |
| From: | Rencurrel D W South Texas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NOC-AE-12002811, TAC ME4936, TAC ME4937 | |
| Download: ML12097A064 (17) | |
Text
Nuclear Operating CompanySouth Texas Proect Electric Generating Station P.. Box 289 Wadsworth. Texas 77483 /V --March 28, 2012NOC-AE-1200281110 CFR 54STI: 33375166File: 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 for theSouth Texas Project License Renewal ApplicationAging Management Program, Set 14 (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-1 0002607) (ML1 03010257)2. NRC letter dated February 28, 2012, "Requests for Additional Information for theReview of the South Texas Project, Units 1 and 2 License Renewal Application -Aging Management, Set 14 (TAC Nos. ME4936 and ME 4937)" (ML12053A430)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, the NRC staffrequests additional information for review of the STP LRA. STPNOC's response to the requests foradditional information is provided in Enclosure 1 to this letter. Changes to LRA pages described inEnclosure 1 are depicted in line-in/line-out pages provided in Enclosure 2.There are no regulatory commitments provided 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 on /&z 1.2.0l2-Date,. W.RencurrelChief Nuclear OfficerKJT
Enclosures:
1. STPNOC Response to Requests for Additional Information2. STPNOC LRA Changes with Line-in/Line-out Annotations NOC-AE-12002811Page 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. 0. 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-12002811Enclosure ISTPNOC Response to Requests for Additional Information NOC-AE-12002811Page 1 of 9SOUTH TEXAS PROJECT, UNITS I AND 2REQUEST FOR ADDITIONAL INFORMATIONAGING MANAGEMENT, SET 14(TAC NOS. ME4936 AND ME4937)Open-Cycle Cooling Water System (021)RAI B2.1.9-1a
Background:
Discussions with the applicant during the aging management program (AMP) audit indicatedthat the inclusion of cracking as an aging effect managed by the Open-Cycle Cooling WaterSystem program was an error. The staff issued RAI B2.1.9-1 to confirm this. In its responsedated September 15, 2011, the applicant revised license renewal application (LRA) SectionsA1.9 and B2.1.9 to delete cracking as an aging effect in the Open-Cycle Cooling Water Systemprogram and stated no other sections of the LRA were identified that required revision for thiserror.During its review of plant-specific operating experience, the staff noted that, in Licensee EventReports (LERs) 499/2005-004 and 499/2010-001, cracking had apparently been identified inthe heat affected zones for multiple welds in the aluminum bronze piping of the essentialcooling water (ECW) system. Neither LER provided a cause of the crack initiation. The staffalso noted that, as indicated in "Aluminum Bronze Alloys Corrosion Resistance Guide,"Publication No. 80, Copper Development Association, 1981, a factor to consider in somegrades of aluminum bronze is the formation of microfissures in the heat-affected zones duringwelding, which can act as stress raisers and increase the danger of stress corrosion cracking insubsequent service.Issue:Based on the identification of cracking in plant-specific operating experience, which hasapparently occurred in the heat affected zones for multiple welds in aluminum bronze piping ofthe ECW system, it is unclear to the staff why cracking is not an aging effect that requiresmanagement for the associated material and environment combination.Request:Provide an aging management review (AMR) line item and propose an AMP to managecracking of the aluminum bronze piping exposed to raw water in the ECW system or providethe technical bases giving reasonable assurance that the ECW components will continue tomeet their licensing basis during the period of extended operation without managing this agingeffect. NOC-AE-12002811Page 2 of 9STPNOC Response:STPNOC plans to provide a response by May 30, 2012.RAI B2.1.9-2a
Background:
RAI B2.1.9-2 addressed plant-specific operating experience at STP which resulted in managingthe loss of material due to cavitation erosion in the ECW system. The applicant's response toRAI B2.1.9-2 stated that erosion/corrosion is being managed by the Open-Cycle Cooling WaterSystem program; however, it did not address the individual program elements affected by thisenhancement to the AMP. Although certain aspects of the affected program elements may beinferred from the response, the staff is not certain which program elements the applicantconsiders as being affected and in what specific manner.With respect to extent of condition reviews performed for components in other systems, theresponse to RAI B2.1.9-2 stated "[I]ocations in other systems were not evaluated [for erosioncorrosion] because the unique material/environment combination of the ECW system is notfound in the other systems and erosion has not been found in other systems." The staff notedthat loss of material from cavitation erosion can occur in many different environments for manydifferent materials. The staff also noted that, in its response to RAI 3.4.2.6-1, the applicantstated that it had identified six systems subject to wall thinning due to erosion-corrosion that arebeing managed by the Flow-Accelerated Corrosion program, and it was not clear to the staffwhat distinction was being drawn by the applicant for the term erosion corrosion between thetwo RAI responses.Issue:The applicant is managing loss of material due to cavitation erosion through the Open-CycleCooling Water System program, but did not provide information in the response to RAI B2.1.9-2as to which specific program elements are affected by this enhancement and in what specificmanner. In addition, the applicant appears to be using different definitions of the term erosioncorrosion in its responses to RAI B2.1.9-2 and RAI 3.4.2.6-1.Request:Describe the specific enhancement to the Open-Cycle Cooling Water System program,including the program elements affected, that has been implemented as a result of the loss ofmaterial identified in plant-specific operating experience discussed above. Also, clarify why theresponse to RAI B2.1.9-2 stated that erosion has not been found in other systems, whenerosion was identified in six systems in the response to RAI 3.4.2.6-1.STPNOC Response:STPNOC plans to provide a response by April 5, 2012. NOC-AE-12002811Page 3 of 9RAI B2.1.9-3aBack.qround:RAI B2.1.9-3 addressed the potential problem associated with reduction in heat transfer in theECW system caused by the degradation of the coatings used to mitigate loss of material. TheRAI asked for information to show that the size and amount of debris, which could result fromprotective coating failures, will not affect intended function of the downstream components.The response to RAI B2.1.9-3 stated that inspections of protective coatings are conductedduring general system inspections and during various preventive maintenance activities. Theresponse also stated that the heat exchangers cooled by ECW are either periodicallyperformance tested or are periodically inspected and cleaned if required. The responsediscussed instances where material from degraded coatings had been found in several ECWheat exchangers, but stated no sheeting-type coating failures had been observed. Theresponse noted these coating failures had no impact on the heat exchangers' performance andconcluded by stating that continued implementation of the Open-Cycle Cooling Water Systemprogram and the tracking of plant operating experience provides reasonable assurance that anyfouling caused by protective coating failures will be adequately managed.Issue:Although STP has not experienced sheeting-type coating failures, on multiple occasions thecoating failures have resulted in material of sufficient size to block various heat exchangertubes. While these occasions to date have not adversely affected the intended functions ofdownstream components, these situations appear to be related to the amount of debrisresulting from coating breakdowns as opposed to the inability of the debris from coatingbreakdowns to affect the intended function.Request:Provide past corrective actions that have either resulted in enhancements to the Open-CycleCooling Water System program or have resulted in changes to the coatings used in the ECWsystem to support the conclusion that the effects of aging will be adequately managed tomaintain intended functions of downstream components.STPNOC Response:A search of condition reports has not found occasions of coating failures resulting in coolingwater heat exchanger tube blockage. There has been no plugging of tubes by Belzonacoatings. Additionally there has been no loss of cooling water heat exchanger intendedfunction due to Belzona coatings.Belzona coatings are applied to locations in the Essential Cooling Water (ECW) system thathave experienced loss of material due to erosion. The ECW pumps and the surfaces of theECW pump discharge piping reducer are coated with Belzona. The component cooling waterheat exchanger throttle valves and the piping near these valves are coated with Belzona. NOC-AE-12002811Page 4 of 9The coated ECW pumps are upstream of the self-cleaning strainers. The self-cleaningstrainers are designed to prevent material larger then 1/16" from entering the componentcooling water heat exchangers. The self-cleaning strainers mesh size is smaller than the heatexchanger tubes and serves to protect the heat exchangers from particles greater than 1/16".The coated locations downstream of the component cooling water return throttle valves aredownstream of the heat exchangers. Failed Belzona coating from these locations does notpass through the component cooling water heat exchangers, but instead flows to piping thatreturns to the ECW pond.Condition Report 05-8601 documents a failure of temporary Belzona 1111 coating applied tothe Unit 1 ECW piping downstream of the component cooling water heat exchanger. Anengineering evaluation concluded that the peeled off Belzona 1111 coating had no impact onoperations of the ECW system. The temporary Belzona 1111 coating was replaced withBelzona 2141 which is cavitation resistant and less susceptible to peeling.During maintenance of Unit 2 standby diesel generator (SDG) 23 in 2007, Condition Report 07-16847 documented the presence of foreign material and minor corrosion in both left and rightbank intercoolers of the diesel generator. An engineering evaluation concluded that theconditions found in the intercoolers did not affect intercooler ability to perform their designfunction and the current inspection interval is adequate. The Open Cycle Cooling WaterSystem program (B2.1.20) requires periodic inspection of diesel generator intercoolers andcleaning, if required. The periodic inspection work scope includes inspecting debris removal,measuring fouling thickness, and cleaning. These inspections demonstrate that the effects ofaging are being managed adequately to maintain the intended function of these intercoolers.Condition Reports 10-12875 and 10-12573 document plugging of the drain valve opening in theessential chiller. The blockage was due to excess Belzona coating applied around the inside ofthe drain hole. The blockage was not due to an accumulation of Belzona particles and was notage-related.Selected components in the ECW system are coated to mitigate the erosive and corrosiveaging effects of open cycle cooling water. Three types of coatings are used: Belzona, Plasticap400 Epoxy Phenolic and coal tar epoxy. These coatings are inspected as part of the OpenCycle Cooling Water System program (B2.1.20). The essential chiller condenser, SDG lube oilcooler, SDG jacket water cooler, and SDG intercooler water boxes are coated with Belzona.The essential chiller condenser coatings are inspected every five years. The SDG lube oilcooler and jacket water cooler water box coatings are inspected every five years duringpreventive maintenance (PM) disassembly. Interconnecting SDG intercoolers piping is coatedwith Plasticap 400 Epoxy Phenolic. The coating is inspected every five years as part of theperiodic intercooler inspection.The ECW intake bay traveling screens upstream of the self-cleaning strainers are coated withcoal tar epoxy. The traveling screens are inspected during PM activities. The ECW pumps arecoated with Belzona. The coating is inspected during pump disassembly. ECW pumpdisassembly is scheduled as a refurbishment activity and controlled by the Major Pump andMotor Maintenance Plan. This maintenance plan has a nominal 10 year refurbishmentperiodicity. The piping near the component cooling water heat exchanger return throttle valvesis coated with Belzona. The piping coatings are inspected every five years during PM activities. -NOC-AE-12002811Page 5 of 9Based on operating history, the ability of the ECW system to perform its intended functions isnot affected by erosion of Belzona coatings. The Open Cycle Cooling Water System program(B2.1.20), in addition to performance testing, requires periodic inspection and cleaning of theECW piping. Operating history demonstrates that the effects of aging are being managedadequately by the Open Cycle Cooling Water System program (B2.1.20) to maintain theintended function of the ECW system.RAI B2.1.9-4aBackqround:RAI B2.1.9-4 asked for the technical bases to show that, without protective coatings, the loss ofmaterial due to worst case cavitation erosion will be adequately managed. The staff noted thatthe AMP basis document stated that coatings are not credited in aging management to protectmetal surfaces. The response to RAI B2.1.9-4 states that it is acceptable if coatings erode awaybetween inspections because the piping inspections ensure that the piping is repaired orreplaced before it reaches the minimum allowable wall thickness. The response also stated thatthe wear rate is calculated from the measurement of wear and the previous inspection results,which is then used with conservatisms to calculate the lifetime of the component.Issue:Since the applicant states that it is acceptable for coatings to erode away between inspections,it is not clear to the staff how the lifetime of the component can be calculated because theamount of time that the coating has protected the component appears to be unknown. As aresult, the staff would expect that the "conservatism" noted above in the applicant's responsewould assume the worst case loss of material which could occur between inspections withoutany coating. The applicant did not define the conservatisms used to calculate the lifetime of thecomponent and how those conservatisms were established.Request:For each location where coatings are used in the ECW system, provide information relative tothe conservatisms used in the calculation that establishes the lifetime of the component todemonstrate that the coatings are not credited in aging management to protect metal surfaces.STPNOC Response:STPNOC plans to provide a response by April 5, 2012. NOC-AE-12002811Page 6 of 9Heat Exchangers (085)RAI 3.3.2.4-2
Background:
SRP-LR Table 2.1-3 states that both the pressure boundary and heat transfer functions for heatexchangers should be considered because heat transfer may be a primary safety function ofthese components. The staff noted that the NRC provided this clarification of the SRP-LR to theindustry by letter dated November 19, 1999 (see ADAMS Accession No. ML993350072). Inaddition, the GALL Report,Section IX.F, "Aging Mechanisms," states that fouling can becategorized as particulate fouling from dust and that fouling can result in a reduction of heattransfer.In RAI 3.3.2.4-1, the staff noted that heat exchangers with an intended function of heat transferin various air environments were not being managed for reduction of heat transfer, and thatthese heat exchangers may be adversely affected by fouling due to dust. The staff requestedSTP to provide the technical bases demonstrating that reduction of heat transfer does not needto be managed for these components. In its response dated November 21, 2011, STP statedthat the heat exchanger components exposed to the environments of "plant indoor air" and"ventilation atmosphere" are located inside buildings that are subject to a clean air environment,since the outside air is filtered prior to entry into the associated buildings. The responseconcluded that the building air environment is not considered conducive to heat exchangerfouling and accumulation of dust on heat exchanger surfaces.Issue:Although outside air may be filtered prior to entry into the buildings, from a practicalperspective, the air within the associated buildings cannot be considered a "clean airenvironment," because dust and debris are also generated inside the buildings during normalplant activities. If, however, the heat exchanger surfaces (like a room cooler) have air filters justprior to the component, that are periodically maintained, then the component could beconsidered to be exposed to a clear air environment. Otherwise, if the room air is circulatedpast heat exchanger surfaces without a filter that is periodically maintained, then thedetermination that this aging effect is not expected to occur would need to be confirmed. Asnoted in GALL AMP XI.M32, One-Time Inspection, "situations in which additional confirmationis appropriate include (a) an aging effect is not expected to occur, but data are insufficient torule it out with reasonable confidence, or (b) an aging effect is expected to progress very slowlyin the specified environment, but the local environment may be more adverse than generallyexpected."Request:For heat exchanger-related AMR items in the LRA that list an intended function of heat transferin an environment of "plant indoor air," or "ventilation atmosphere," but do not considerreduction of heat transfer as an aging effect requiring management, either (a) provideinformation demonstrating that each item has an air filter that is periodically maintainedreasonably close to the heat exchanger surfaces, (b) provide information from past inspectionsof components, which have never been cleaned, showing that fouling of heat exchanger NOC-AE-12002811Page 7 of 9surfaces in these environments is not occurring or is occurring so slowly that this aging effectdoes not require management, or (c) provide an appropriate program to manage reduction ofheat transfer for the subject heat exchanger-related AMR items with a heat transfer function.STPNOC Response:Outside air is supplied to the Electrical Auxiliary Building (EAB) heating ventilation and airconditioning (HVAC) systems through safety-related filter units. The air enters the EAB througha prefilter and a high efficiency filter before distribution throughout the EAB HVAC system(Reference Boundary Drawing LR-STP-HE-5V119V25000#1)'. One hundred percent of the airis filtered before passing through the EAB main air-handling unit heat exchanger surfaces.The Fuel Handling Building (FHB) HVAC system is normally supplied by outside filtered air.One hundred percent of the outside air is filtered before passing into the building HVAC system.The filtered air provides ventilation for high head safety injection pump cubicles, low headsafety injection pump cubicles, containment spray pump cubicles, spent fuel pool pumpcubicles and containment sump isolation valve cubicles (Reference Boundary DrawingLR-STP-HF-5V129V00012#1) .Supplementary recirculating-type coolers recirculate cubicleair. The recirculating coolers do not have filters. Preventive maintenance (PM) activities areperformed on the coolers. One PM attribute inspects cooler unit cleanliness with cleaning asrequired. A review of past cooler inspections determined fouling of cooler fins is not occurring.The Mechanical Auxiliary Building (MAB) HVAC system is supplied by outside filtered air. Onehundred percent of incoming air is filtered before passing into the building HVAC system. Thefiltered air provides ventilation for component cooling water pump cubicles, charging pumpcubicles, valve cubicles, boric acid transfer pump rooms, reactor water makeup pump rooms,radiation monitor rooms and essential chiller area rooms (Reference Boundary DrawingLR-STP-HM-5V109V00008 #1)1. Supplementary recirculating type coolers recirculate cubicleair. The recirculating coolers do not have filters. PM activities are performed on the coolers.One PM attribute inspects cooler unit cleanliness and cleans as required. A review of pastcooler inspections determined fouling of cooler fins is not occurring.Plant indoor air in the EAB, MAB and FHB buildings is filtered prior to entry into the buildings.The filtered air is distributed throughout the buildings and then exhausted to the outside thusmaintaining a dust-free environment in each building. These buildings are not openconstruction areas and are maintained clean by general housekeeping procedures. Ifdust-generating activities are to take place, the immediate area is secured and any dustgeneration is contained. PM activities maintain the building supplementary coolers clean.There is no plant operating experience related to loss of heat transfer intended function due toheat exchanger fouling because of dust. Since the plant indoor air is filtered and there is nooperating experience that shows fouling of heat exchangers is occurring, the aging effect offouling due to dust is not applicable to the South Texas Project.1 Drawings transmitted to the NRC on October 25, 2010 by STPNOC letter NOC-AE-10002612 NOC-AE-12002811Page 8 of 9One-Time Inspection of ASME Code Class I Small-Bore Piping (036)RAI B2.1.19-4Backqround:In its RAI response dated January 18, 2012, the applicant indicated that its amendment, datedJune 16, 2011, to the LRA provided sections with changes but did not provide the completeLRA Section B2.1.19 for the One-Time Inspection of ASME Code Class 1 Small-Bore Pipingprogram. The applicant further stated that the most recent revision to LRA Section B2.1.19 wasprovided in its letter dated November 17, 2011, which includes an exception to GALL AMPXI.M35, "One-Time Inspection of ASME Code Class 1 Small-Bore Piping."The program exception states that the applicant's risk-informed inservice inspection(RI-ISI) is based on EPRI TR-1 12657, "Revised Risk-informed Inservice InspectionEvaluation Procedure," which incorporated EPRI Report 1000701, "Interim ThermalFatigue Management Guideline (MRP-24)." The exception also states that the applicantuses its RI-ISI, instead of MRP-24, to manage thermal fatigue in reactor coolant systembranch lines. It further states that the recommended inspection locations in MRP-24 areidentical to those for inspection of thermal fatigue in its RI-ISI.Issue:The staff noted that MRP-24 was superseded in 2005 by revised guidance, "Management ofThermal Fatigue in Normally Stagnant Non-Isolable Reactor Coolant System Branch Lines(MRP-146)." The staff further noted that MRP-146 and its supplement contain manyimprovements, including inspection locations, in managing thermal fatigue in reactor coolantsystem branch lines. GALL Report, Revision 2, recommends and references the revisedguidance, MRP-146.Given the different submittals provided by the applicant regarding this program, the staffneeds clarification regarding the applicant's latest proposed One-Time Inspection ofASME Code Class 1 Small-Bore Piping program, specifically regarding whether theapplicant intended to credit the previously proposed exception to GALL AMP XI.M35. Asindicated above, the staff also does not find such exception acceptable as it does notprovide a technical justification as to why use of the RI-ISI is sufficient when comparedto the latest recommendation in GALL Report, Revision 2 (i.e., MRP-146).Request:Provide or confirm the latest revision to the LRA with respect to the One-Time Inspection ofASME Code Class 1 Small-Bore Piping program.As part of this submittal provide the technical basis to justify why the RI-ISI and its comparisonto the outdated guidance in MRP-24 is adequate in managing thermal fatigue in reactor coolantsystem branch lines. NOC-AE-12002811Page 9 of 9STPNOC Response:LRA Appendix B2.1.19 and LRA Basis Document XI.M35, One-Time Inspection of ASME CodeClass 1 Small-Bore Piping program, Exceptions to NUREG-1801, Scope of Program (Element1) is revised to state South Texas Project follows the guidance in EPRI Report 1011955,Materials Reliability Program: Management of Thermal Fatigue in Normally StagnantNon-lsolable Reactor Coolant System Branch Lines (MRP-146). EPRI Report 1011955 (MRP-146) incorporates and expands on the interim guidance provided in EPRI Report 1000701(MRP-24).Enclosure 2 provides the latest revision to the LRA with respect to the One-Time Inspection ofASME Code Class 1 Small-Bore Piping program as line-in/line-out revision for the changes toAppendix B2.1.19. NOC-AE-12002811Enclosure 2STPNOC LRA Changes with Line-in/Line-out Annotations NOC-AE-12002811Page 1 of 4List of Revised LRA SectionRAI Affected LRA SectionRAI B2.1.19-4 Appendix B2.1.19 NOC-AE-12002811Page 2 of 4B2.1.19 One-Time Inspection of ASME Code Class I Small-Bore PipingProgram DescriptionThe One-Time Inspection of ASME Code Class 1 Small-Bore Piping program managescracking of ASME Code Class 1 piping less than or equal to four inches nominal pipe size(NPS 4). This piping is ASME examination category B-J. This program is implemented aspart of the fourth interval of the ISI Program.For ASME Code Class 1 small-bore piping, the ISI Program requires volumetricexaminations (by ultrasonic testing) on selected butt weld locations to detect cracking.Weld locations are selected based on the guidelines provided in EPRI TR-1 12657, RevisedRisk-Informed Inservice Inspection Evaluation Procedure. Ultrasonic examinations areconducted in accordance with ASME Section Xl with acceptance criteria from paragraphIWB-3000 and IWB-2430 for butt welds. Unit 1 has 182 Class 1 small-bore butt welds and49 Class 1 small-bore socket welds. The inspection sample for the Unit 1 Class 1small-bore butt welds is 19 and the inspection sample for the Unit 1 Class 1 small-boresocket welds is 5, which is 10 percent of each population. In Unit 2, there are 190 Class 1small-bore butt welds and 59 Class 1 small-bore socket welds. The inspection sample sizefor the Unit 2 Class 1 small-bore butt welds is 19 and the inspection sample size for Unit 2Class 1 small-bore socket welds is 6, which is 10 percent for each population.Socket welds that fall within the weld examination sample will be examined following ASMESection XI Code requirements. If a qualified volumetric examination procedure for socketwelds endorsed by the industry and the NRC is available and incorporated into the ASMESection XI Code at the time of STP small-bore socket weld inspections, then this will beused for the volumetric examinations. If no volumetric examination procedure for ASMECode Class 1 small-bore socket welds has been endorsed by the industry and the NRC andincorporated into ASME Section Xl at the time STP performs inspections of small-borepiping, a plant procedure for volumetric examination of ASME Code Class 1 small-borepiping with socket welds will be used.The One-Time Inspection of ASME Code Class 1 Small-Bore Piping program inspectionswill be completed and evaluated within six years prior to the period of extended operation.Should evidence of cracking be revealed by the One-Time Inspection of ASME Code Class1 Small-Bore Piping program, periodic inspection will be proposed, as managed by aplant-specific aging management program.In conformance with 10 CFR 50.55a(g)(4)(ii), the STP ISI Program is updated during eachsuccessive 120-month inspection interval to comply with the requirements of the latestedition of the ASME Code specified 12 months before the start of the inspection interval.STP will use the ASME Code Edition consistent with the provisions of 10 CFR 50.55a duringthe 10 year period prior to the period of extended operation (fourth interval) and during theperiod of extended operation. NOC-AE-12002811Page 3 of 4NUREG-1801 ConsistencyThe One-Time Inspection of ASME Code Class 1 Small-Bore Piping program is a newprogram that, when implemented, will be consistent, with exception to NUREG-1801,Section XI.M35, One-Time Inspection of ASME Code Class 1 Small-Bore Piping.Exceptions to NUREG-1801Program Elements AffectedScope of Program (Element 1)NUREG 1801,Section XI.M35 specifies that guidelines for identifying piping susceptible topotential effects of thermal stratification or turbulent penetration are provided in EPRIReport 1000701, "Interim Thermal Fatigue Management Guideline (MRP-24)," January2001. The STP risk informed process examination requirements are performed consistentwiAt EPRI TR 112657, R1vi5ed Risk infeomed lnsded4i Inspection Evaluation Pro-eddureP,Revision B A, instead of EPRI Report 1000701, inteRIm Thermal Fatigue lanagemeniGuidance (MRP 24). Guidelines fRn EPI g ceptible to ptential effects othermal stratification or turbulent penetration tided in EPRI Report 10007-01 arealso provided in EPRI TR 11265:7. The recommIe~ndedG inspection volumes for welds in EPRIReport 1000701 are identical to those for inspection of thermal fatigue in R!IS'5 Programs;--thus, the ST-P risk infomed process examination requirements mneet the recommendationsof NUREG 1801. STP follows the guidance in EPRI Report 1011955. Materials ReliabilityProgram: Management of Thermal Fatigue in Normally Stann No-Isolable ReactorCoolant System Branch Lines (MRP-146). EPRI Report 1011955 (MRP-146) incorporatesand expands on the interim guidance provided in EPRI Report 1000701 (MRP-24).EnhancementsNoneOperating ExperienceIn order to estimate the extent of cracking in Class 1 piping socket welds, NEI conducted areview of LERs. Of 141 LERs reviewed, 48 were determined to be associated with failuresof Class 1 socket welds. For the 46 LERs where a cause was identified, 42 of the failureswere due to either vibration-induced high cycle fatigue or improper installation and are notage-related. Of the four remaining failures, one was due to randomly applied loads duringmaintenance and not age-related, and three were related to aging: two due to insulationcontamination on the outside surface, and one associated with IGSCC, although there wereother contributing factors not associated with aging (poor weld fit up, weld repair, nearbymissing support, etc.).The NEI review indicates that there have been a relatively small number of Class 1 socketweld failures of which only three were related to aging. NOC-AE-12002811Page 4 of 4A review of plant-specific operating experience indicates that no cracking has beenobserved for ASME Code Class 1 small-bore pipe welds less than or equal to NPS 4.Based on a review of operating experience, cracking of ASME Code Class 1 small-borepipe welds less than or equal to NPS 4 has not been observed. This provides confidencethat the One-Time Inspection of ASME Code Class 1 Small-Bore Piping program isadequate to manage cracking in ASME Code Class 1 small-bore piping.As additional industry and plant-specific applicable operating experience becomes available,it will be evaluated and incorporated into the program through the STP condition reportingand operating experience programs.ConclusionThe implementation of the One-Time Inspection of ASME Code Class 1 Small-Bore Pipingprogram will provide reasonable assurance that aging effects will be managed such that thesystems and components within the scope of this program will continue to perform theirintended functions consistent with the current licensing basis for the period of extendedoperation.