NOC-AE-12002811, Response to Requests for Additional Information for the South Texas Project License Renewal Application Aging Management Program, Set 14
| ML12097A064 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 03/28/2012 |
| From: | Rencurrel D 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 Company South Texas ProectElectric GeneratingStation P.. Box 289 Wadsworth. Texas 77483 /V - -
March 28, 2012 NOC-AE-12002811 10 CFR 54 STI: 33375166 File: G25 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 South Texas Project Units 1 and 2 Docket Nos. STN 50-498, STN 50-499 Response to Requests for Additional Information for the South Texas Project License Renewal Application Aging Management Program, Set 14 (TAC Nos. ME4936 and ME4937)
References:
- 1. STPNOC letter dated October 25, 2010, from G. T. Powell to NRC Document Control Desk, "License Renewal Application" (NOC-AE-1 0002607) (ML103010257)
- 2. NRC letter dated February 28, 2012, "Requests for Additional Information for the Review 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 Renewal Application (LRA) for South Texas Project (STP) Units 1 and 2. By Reference 2, the NRC staff requests additional information for review of the STP LRA. STPNOC's response to the requests for additional information is provided in Enclosure 1 to this letter. Changes to LRA pages described in 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, STP License Renewal Project Lead, at (361) 972-8243 or Ken Taplett, STP License Renewal Project regulatory 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.Rencurrel Chief Nuclear Officer KJT
Enclosures:
- 1. STPNOC Response to Requests for Additional Information
NOC-AE-12002811 Page 2 cc:
(paper copy) (electronic copy)
Regional Administrator, Region IV A. H. Gutterman, Esquire U. S. Nuclear Regulatory Commission Kathryn M. Sutton, Esquire 1600 East Lamar Boulevard Morgan, Lewis & Bockius, LLP Arlington, Texas 76011-4511 Balwant K. Singal John Ragan Senior Project Manager Chris O'Hara U.S. Nuclear Regulatory Commission Jim von Suskil One White Flint North (MS 8B1) NRG South Texas LP 11555 Rockville Pike Rockville, MD 20852 Senior Resident Inspector Kevin Polio U. S. Nuclear Regulatory Commission Richard Pena P. 0. Box 289, Mail Code: MN116 City Public Service Wadsworth, TX 77483 C. M. Canady Peter Nemeth City of Austin Crain Caton & James, P.C.
Electric Utility Department 721 Barton Springs Road C. Mele Austin, TX 78704 City of Austin John W. Daily Richard A. Ratliff License Renewal Project Manager (Safety) Alice Rogers U.S. Nuclear Regulatory Commission Texas Department of State Health Services One White Flint North (MS 011-Fl)
Washington, DC 20555-0001 Tam Tran Balwant K. Singal License Renewal Project Manager John W. Daily (Environmental) Tam Tran U. S. Nuclear Regulatory Commission U. S. Nuclear Regulatory Commission One White Flint North (MS O11F01)
Washington, DC 20555-0001
Enclosure 1 NOC-AE-12002811 Enclosure I STPNOC Response to Requests for Additional Information
Enclosure 1 NOC-AE-12002811 Page 1 of 9 SOUTH TEXAS PROJECT, UNITS I AND 2 REQUEST FOR ADDITIONAL INFORMATION AGING 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 indicated that the inclusion of cracking as an aging effect managed by the Open-Cycle Cooling Water System program was an error. The staff issued RAI B2.1.9-1 to confirm this. In its response dated September 15, 2011, the applicant revised license renewal application (LRA) Sections A1.9 and B2.1.9 to delete cracking as an aging effect in the Open-Cycle Cooling Water System program and stated no other sections of the LRA were identified that required revision for this error.
During its review of plant-specific operating experience, the staff noted that, in Licensee Event Reports (LERs) 499/2005-004 and 499/2010-001, cracking had apparently been identified in the heat affected zones for multiple welds in the aluminum bronze piping of the essential cooling water (ECW) system. Neither LER provided a cause of the crack initiation. The staff also noted that, as indicated in "Aluminum Bronze Alloys Corrosion Resistance Guide,"
Publication No. 80, Copper Development Association, 1981, a factor to consider in some grades of aluminum bronze is the formation of microfissures in the heat-affected zones during welding, which can act as stress raisers and increase the danger of stress corrosion cracking in subsequent service.
Issue:
Based on the identification of cracking in plant-specific operating experience, which has apparently occurred in the heat affected zones for multiple welds in aluminum bronze piping of the ECW system, it is unclear to the staff why cracking is not an aging effect that requires management for the associated material and environment combination.
Request:
Provide an aging management review (AMR) line item and propose an AMP to manage cracking of the aluminum bronze piping exposed to raw water in the ECW system or provide the technical bases giving reasonable assurance that the ECW components will continue to meet their licensing basis during the period of extended operation without managing this aging effect.
Enclosure 1 NOC-AE-12002811 Page 2 of 9 STPNOC 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 managing the loss of material due to cavitation erosion in the ECW system. The applicant's response to RAI B2.1.9-2 stated that erosion/corrosion is being managed by the Open-Cycle Cooling Water System program; however, it did not address the individual program elements affected by this enhancement to the AMP. Although certain aspects of the affected program elements may be inferred from the response, the staff is not certain which program elements the applicant considers as being affected and in what specific manner.
With respect to extent of condition reviews performed for components in other systems, the response to RAI B2.1.9-2 stated "[I]ocations in other systems were not evaluated [for erosion corrosion] because the unique material/environment combination of the ECW system is not found in the other systems and erosion has not been found in other systems." The staff noted that loss of material from cavitation erosion can occur in many different environments for many different materials. The staff also noted that, in its response to RAI 3.4.2.6-1, the applicant stated that it had identified six systems subject to wall thinning due to erosion-corrosion that are being managed by the Flow-Accelerated Corrosion program, and it was not clear to the staff what distinction was being drawn by the applicant for the term erosion corrosion between the two RAI responses.
Issue:
The applicant is managing loss of material due to cavitation erosion through the Open-Cycle Cooling Water System program, but did not provide information in the response to RAI B2.1.9-2 as to which specific program elements are affected by this enhancement and in what specific manner. In addition, the applicant appears to be using different definitions of the term erosion corrosion 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 of material identified in plant-specific operating experience discussed above. Also, clarify why the response to RAI B2.1.9-2 stated that erosion has not been found in other systems, when erosion 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.
Enclosure 1 NOC-AE-12002811 Page 3 of 9 RAI B2.1.9-3a Back.qround:
RAI B2.1.9-3 addressed the potential problem associated with reduction in heat transfer in the ECW system caused by the degradation of the coatings used to mitigate loss of material. The RAI asked for information to show that the size and amount of debris, which could result from protective 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 conducted during general system inspections and during various preventive maintenance activities. The response also stated that the heat exchangers cooled by ECW are either periodically performance tested or are periodically inspected and cleaned if required. The response discussed instances where material from degraded coatings had been found in several ECW heat exchangers, but stated no sheeting-type coating failures had been observed. The response noted these coating failures had no impact on the heat exchangers' performance and concluded by stating that continued implementation of the Open-Cycle Cooling Water System program and the tracking of plant operating experience provides reasonable assurance that any fouling caused by protective coating failures will be adequately managed.
Issue:
Although STP has not experienced sheeting-type coating failures, on multiple occasions the coating failures have resulted in material of sufficient size to block various heat exchanger tubes. While these occasions to date have not adversely affected the intended functions of downstream components, these situations appear to be related to the amount of debris resulting from coating breakdowns as opposed to the inability of the debris from coating breakdowns to affect the intended function.
Request:
Provide past corrective actions that have either resulted in enhancements to the Open-Cycle Cooling Water System program or have resulted in changes to the coatings used in the ECW system to support the conclusion that the effects of aging will be adequately managed to maintain intended functions of downstream components.
STPNOC Response:
A search of condition reports has not found occasions of coating failures resulting in cooling water heat exchanger tube blockage. There has been no plugging of tubes by Belzona coatings. Additionally there has been no loss of cooling water heat exchanger intended function due to Belzona coatings.
Belzona coatings are applied to locations in the Essential Cooling Water (ECW) system that have experienced loss of material due to erosion. The ECW pumps and the surfaces of the ECW pump discharge piping reducer are coated with Belzona. The component cooling water heat exchanger throttle valves and the piping near these valves are coated with Belzona.
Enclosure 1 NOC-AE-12002811 Page 4 of 9 The coated ECW pumps are upstream of the self-cleaning strainers. The self-cleaning strainers are designed to prevent material larger then 1/16" from entering the component cooling water heat exchangers. The self-cleaning strainers mesh size is smaller than the heat exchanger 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 are downstream of the heat exchangers. Failed Belzona coating from these locations does not pass through the component cooling water heat exchangers, but instead flows to piping that returns to the ECW pond.
Condition Report 05-8601 documents a failure of temporary Belzona 1111 coating applied to the Unit 1 ECW piping downstream of the component cooling water heat exchanger. An engineering evaluation concluded that the peeled off Belzona 1111 coating had no impact on operations of the ECW system. The temporary Belzona 1111 coating was replaced with Belzona 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 right bank intercoolers of the diesel generator. An engineering evaluation concluded that the conditions found in the intercoolers did not affect intercooler ability to perform their design function and the current inspection interval is adequate. The Open Cycle Cooling Water System program (B2.1.20) requires periodic inspection of diesel generator intercoolers and cleaning, if required. The periodic inspection work scope includes inspecting debris removal, measuring fouling thickness, and cleaning. These inspections demonstrate that the effects of aging 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 the essential chiller. The blockage was due to excess Belzona coating applied around the inside of the drain hole. The blockage was not due to an accumulation of Belzona particles and was not age-related.
Selected components in the ECW system are coated to mitigate the erosive and corrosive aging effects of open cycle cooling water. Three types of coatings are used: Belzona, Plasticap 400 Epoxy Phenolic and coal tar epoxy. These coatings are inspected as part of the Open Cycle Cooling Water System program (B2.1.20). The essential chiller condenser, SDG lube oil cooler, 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 oil cooler and jacket water cooler water box coatings are inspected every five years during preventive maintenance (PM) disassembly. Interconnecting SDG intercoolers piping is coated with Plasticap 400 Epoxy Phenolic. The coating is inspected every five years as part of the periodic intercooler inspection.
The ECW intake bay traveling screens upstream of the self-cleaning strainers are coated with coal tar epoxy. The traveling screens are inspected during PM activities. The ECW pumps are coated with Belzona. The coating is inspected during pump disassembly. ECW pump disassembly is scheduled as a refurbishment activity and controlled by the Major Pump and Motor Maintenance Plan. This maintenance plan has a nominal 10 year refurbishment periodicity. The piping near the component cooling water heat exchanger return throttle valves is coated with Belzona. The piping coatings are inspected every five years during PM activities.
Enclosure 1-NOC-AE-12002811 Page 5 of 9 Based on operating history, the ability of the ECW system to perform its intended functions is not 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 the ECW piping. Operating history demonstrates that the effects of aging are being managed adequately by the Open Cycle Cooling Water System program (B2.1.20) to maintain the intended function of the ECW system.
RAI B2.1.9-4a Backqround:
RAI B2.1.9-4 asked for the technical bases to show that, without protective coatings, the loss of material due to worst case cavitation erosion will be adequately managed. The staff noted that the AMP basis document stated that coatings are not credited in aging management to protect metal surfaces. The response to RAI B2.1.9-4 states that it is acceptable if coatings erode away between inspections because the piping inspections ensure that the piping is repaired or replaced before it reaches the minimum allowable wall thickness. The response also stated that the 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 the amount of time that the coating has protected the component appears to be unknown. As a result, the staff would expect that the "conservatism" noted above in the applicant's response would assume the worst case loss of material which could occur between inspections without any coating. The applicant did not define the conservatisms used to calculate the lifetime of the component and how those conservatisms were established.
Request:
For each location where coatings are used in the ECW system, provide information relative to the conservatisms used in the calculation that establishes the lifetime of the component to demonstrate 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.
Enclosure 1 NOC-AE-12002811 Page 6 of 9 Heat 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 heat exchangers should be considered because heat transfer may be a primary safety function of these components. The staff noted that the NRC provided this clarification of the SRP-LR to the industry by letter dated November 19, 1999 (see ADAMS Accession No. ML993350072). In addition, the GALL Report,Section IX.F, "Aging Mechanisms," states that fouling can be categorized as particulate fouling from dust and that fouling can result in a reduction of heat transfer.
In RAI 3.3.2.4-1, the staff noted that heat exchangers with an intended function of heat transfer in various air environments were not being managed for reduction of heat transfer, and that these heat exchangers may be adversely affected by fouling due to dust. The staff requested STP to provide the technical bases demonstrating that reduction of heat transfer does not need to be managed for these components. In its response dated November 21, 2011, STP stated that 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 response concluded that the building air environment is not considered conducive to heat exchanger fouling and accumulation of dust on heat exchanger surfaces.
Issue:
Although outside air may be filtered prior to entry into the buildings, from a practical perspective, the air within the associated buildings cannot be considered a "clean air environment," because dust and debris are also generated inside the buildings during normal plant activities. If, however, the heat exchanger surfaces (like a room cooler) have air filters just prior to the component, that are periodically maintained, then the component could be considered to be exposed to a clear air environment. Otherwise, if the room air is circulated past heat exchanger surfaces without a filter that is periodically maintained, then the determination that this aging effect is not expected to occur would need to be confirmed. As noted in GALL AMP XI.M32, One-Time Inspection, "situations in which additional confirmation is appropriate include (a) an aging effect is not expected to occur, but data are insufficient to rule it out with reasonable confidence, or (b) an aging effect is expected to progress very slowly in the specified environment, but the local environment may be more adverse than generally expected."
Request:
For heat exchanger-related AMR items in the LRA that list an intended function of heat transfer in an environment of "plant indoor air," or "ventilation atmosphere," but do not consider reduction of heat transfer as an aging effect requiring management, either (a) provide information demonstrating that each item has an air filter that is periodically maintained reasonably close to the heat exchanger surfaces, (b) provide information from past inspections of components, which have never been cleaned, showing that fouling of heat exchanger
Enclosure 1 NOC-AE-12002811 Page 7 of 9 surfaces in these environments is not occurring or is occurring so slowly that this aging effect does not require management, or (c) provide an appropriate program to manage reduction of heat 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 air conditioning (HVAC) systems through safety-related filter units. The air enters the EAB through a 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 air is 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 head safety injection pump cubicles, containment spray pump cubicles, spent fuel pool pump cubicles and containment sump isolation valve cubicles (Reference Boundary Drawing LR-STP-HF-5V129V00012#1) . Supplementary recirculating-type coolers recirculate cubicle air. The recirculating coolers do not have filters. Preventive maintenance (PM) activities are performed on the coolers. One PM attribute inspects cooler unit cleanliness with cleaning as required. 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. One hundred percent of incoming air is filtered before passing into the building HVAC system. The filtered air provides ventilation for component cooling water pump cubicles, charging pump cubicles, valve cubicles, boric acid transfer pump rooms, reactor water makeup pump rooms, radiation monitor rooms and essential chiller area rooms (Reference Boundary Drawing LR-STP-HM-5V109V00008 #1)1. Supplementary recirculating type coolers recirculate cubicle air. 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 past cooler 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 thus maintaining a dust-free environment in each building. These buildings are not open construction areas and are maintained clean by general housekeeping procedures. If dust-generating activities are to take place, the immediate area is secured and any dust generation 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 to heat exchanger fouling because of dust. Since the plant indoor air is filtered and there is no operating experience that shows fouling of heat exchangers is occurring, the aging effect of fouling due to dust is not applicable to the South Texas Project.
1Drawings transmitted to the NRC on October 25, 2010 by STPNOC letter NOC-AE-10002612
Enclosure 1 NOC-AE-12002811 Page 8 of 9 One-Time Inspection of ASME Code Class I Small-Bore Piping (036)
RAI B2.1.19-4 Backqround:
In its RAI response dated January 18, 2012, the applicant indicated that its amendment, dated June 16, 2011, to the LRA provided sections with changes but did not provide the complete LRA Section B2.1.19 for the One-Time Inspection of ASME Code Class 1 Small-Bore Piping program. The applicant further stated that the most recent revision to LRA Section B2.1.19 was provided in its letter dated November 17, 2011, which includes an exception to GALL AMP XI.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 Inspection Evaluation Procedure," which incorporated EPRI Report 1000701, "Interim Thermal Fatigue Management Guideline (MRP-24)." The exception also states that the applicant uses its RI-ISI, instead of MRP-24, to manage thermal fatigue in reactor coolant system branch lines. It further states that the recommended inspection locations in MRP-24 are identical 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 of Thermal Fatigue in Normally Stagnant Non-Isolable Reactor Coolant System Branch Lines (MRP-146)." The staff further noted that MRP-146 and its supplement contain many improvements, including inspection locations, in managing thermal fatigue in reactor coolant system branch lines. GALL Report, Revision 2, recommends and references the revised guidance, MRP-146.
Given the different submittals provided by the applicant regarding this program, the staff needs clarification regarding the applicant's latest proposed One-Time Inspection of ASME Code Class 1 Small-Bore Piping program, specifically regarding whether the applicant intended to credit the previously proposed exception to GALL AMP XI.M35. As indicated above, the staff also does not find such exception acceptable as it does not provide a technical justification as to why use of the RI-ISI is sufficient when compared to 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 of ASME Code Class 1 Small-Bore Piping program.
As part of this submittal provide the technical basis to justify why the RI-ISI and its comparison to the outdated guidance in MRP-24 is adequate in managing thermal fatigue in reactor coolant system branch lines.
Enclosure 1 NOC-AE-12002811 Page 9 of 9 STPNOC Response:
LRA Appendix B2.1.19 and LRA Basis Document XI.M35, One-Time Inspection of ASME Code Class 1 Small-Bore Piping program, Exceptions to NUREG-1801, Scope of Program (Element
- 1) is revised to state South Texas Project follows the guidance in EPRI Report 1011955, Materials Reliability Program: Management of Thermal Fatigue in Normally Stagnant Non-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). provides the latest revision to the LRA with respect to the One-Time Inspection of ASME Code Class 1 Small-Bore Piping program as line-in/line-out revision for the changes to Appendix B2.1.19.
Enclosure 2 NOC-AE-12002811 Enclosure 2 STPNOC LRA Changes with Line-in/Line-out Annotations
Enclosure 2 NOC-AE-12002811 Page 1 of 4 List of Revised LRA Section RAI Affected LRA Section RAI B2.1.19-4 Appendix B2.1.19
Enclosure 2 NOC-AE-12002811 Page 2 of 4 B2.1.19 One-Time Inspection of ASME Code Class I Small-Bore Piping Program Description The One-Time Inspection of ASME Code Class 1 Small-Bore Piping program manages cracking 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 as part of the fourth interval of the ISI Program.
For ASME Code Class 1 small-bore piping, the ISI Program requires volumetric examinations (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, Revised Risk-Informed Inservice Inspection Evaluation Procedure. Ultrasonic examinations are conducted in accordance with ASME Section Xl with acceptance criteria from paragraph IWB-3000 and IWB-2430 for butt welds. Unit 1 has 182 Class 1 small-bore butt welds and 49 Class 1 small-bore socket welds. The inspection sample for the Unit 1 Class 1 small-bore butt welds is 19 and the inspection sample for the Unit 1 Class 1 small-bore socket welds is 5, which is 10 percent of each population. In Unit 2, there are 190 Class 1 small-bore butt welds and 59 Class 1 small-bore socket welds. The inspection sample size for the Unit 2 Class 1 small-bore butt welds is 19 and the inspection sample size for Unit 2 Class 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 ASME Section XI Code requirements. If a qualified volumetric examination procedure for socket welds endorsed by the industry and the NRC is available and incorporated into the ASME Section XI Code at the time of STP small-bore socket weld inspections, then this will be used for the volumetric examinations. If no volumetric examination procedure for ASME Code Class 1 small-bore socket welds has been endorsed by the industry and the NRC and incorporated into ASME Section Xl at the time STP performs inspections of small-bore piping, a plant procedure for volumetric examination of ASME Code Class 1 small-bore piping with socket welds will be used.
The One-Time Inspection of ASME Code Class 1 Small-Bore Piping program inspections will 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 Class 1 Small-Bore Piping program, periodic inspection will be proposed, as managed by a plant-specific aging management program.
In conformance with 10 CFR 50.55a(g)(4)(ii), the STP ISI Program is updated during each successive 120-month inspection interval to comply with the requirements of the latest edition 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 during the 10 year period prior to the period of extended operation (fourth interval) and during the period of extended operation.
Enclosure 2 NOC-AE-12002811 Page 3 of 4 NUREG-1801 Consistency The One-Time Inspection of ASME Code Class 1 Small-Bore Piping program is a new program 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-1801 Program Elements Affected Scope of Program (Element 1)
NUREG 1801,Section XI.M35 specifies that guidelines for identifying piping susceptible to potential effects of thermal stratification or turbulent penetration are provided in EPRI Report 1000701, "Interim Thermal Fatigue Management Guideline (MRP-24)," January 2001. The STP risk informed process examination requirements are performed consistent wiAt EPRI TR 112657, R1vi5ed Risk infeomed lnsded4i Inspection Evaluation Pro-eddureP, Revision B A, instead of EPRI Report 1000701,inteRIm Thermal Fatigue lanagemeni Guidance (MRP 24). Guidelines fRn EPI g ceptible to ptential effects o thermal stratification orturbulent penetration tided in EPRI Report 10007-01 are also provided in EPRI TR 11265:7. The recommIe~ndedG inspection volumes for welds in EPRI Report 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 recommendations of NUREG 1801. STP follows the guidance in EPRI Report 1011955. Materials Reliability Program: Management of Thermal Fatigue in Normally Stann No-Isolable 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).
Enhancements None Operating Experience In order to estimate the extent of cracking in Class 1 piping socket welds, NEI conducted a review of LERs. Of 141 LERs reviewed, 48 were determined to be associated with failures of Class 1 socket welds. For the 46 LERs where a cause was identified, 42 of the failures were due to either vibration-induced high cycle fatigue or improper installation and are not age-related. Of the four remaining failures, one was due to randomly applied loads during maintenance and not age-related, and three were related to aging: two due to insulation contamination on the outside surface, and one associated with IGSCC, although there were other contributing factors not associated with aging (poor weld fit up, weld repair, nearby missing support, etc.).
The NEI review indicates that there have been a relatively small number of Class 1 socket weld failures of which only three were related to aging.
Enclosure 2 NOC-AE-12002811 Page 4 of 4 A review of plant-specific operating experience indicates that no cracking has been observed 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-bore pipe welds less than or equal to NPS 4 has not been observed. This provides confidence that the One-Time Inspection of ASME Code Class 1 Small-Bore Piping program is adequate 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 reporting and operating experience programs.
Conclusion The implementation of the One-Time Inspection of ASME Code Class 1 Small-Bore Piping program will provide reasonable assurance that aging effects will be managed such that the systems and components within the scope of this program will continue to perform their intended functions consistent with the current licensing basis for the period of extended operation.