NOC-AE-12002825, Supplemental Response to Requests for Additional Information for the South Texas Project License Renewal Application, Aging Management Program, Set 13 and Set 14
| ML12097A065 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 03/29/2012 |
| From: | Rencurrel D South Texas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| TAC ME4936, TAC ME4937, NOC-AE-12002825, STI: 33417770 | |
| Download: ML12097A065 (24) | |
Text
Nuclear Operating Company South Texas Pro/ectElectric GeneratingStation PO.Box 289 Wadsworth, Texas 77483 ý A AAý March 29, 2012 NOC-AE- 12002825 10 CFR 54 STI: 33417770 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 Supplemental Response to Requests for Additional Information for the South Texas Project License Renewal Application Agingq Management Program, Set 13 and 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-10002607)
- 2. NRC letter dated February 15, 2012, "Requests for Additional Information for the Review of the South Texas Project, Units 1 and 2, License Renewal Application
-Aging Management, Set 13 (TAC Nos. ME4936 and ME 4937)"
- 3. STPNOC letter dated March 12, 2012, from G. T. Powell to NRC Document Control Desk "Response to Requests for Additional Information for the South Texas Project License Renewal Application - Aging Management Program, Set 13 (TAC Nos. ME4936 and ME4937)" (NOC-AE-12002802) (ML12079A015)
- 4. 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)
- 5. STPNOC letter dated March 28, 2012, from D. W. Rencurrel to NRC document Control Desk "Response to Requests for Additional Information for the South Texas Project License Renewal Application Aging Management Program, Set 14 (TAC Nos. ME4936 and ME4937)" (NOC-AE-12002811)
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 and 4, the NRC staff requested additional information for review of the STP LRA. STPNOC provided responses to the requests for additional information in References 3 and 5. Additional responses to References 2 and 4 are provided in Enclosure 1 to this letter. Changes to LRA pages described in Enclosure 1 are depicted as line-in/line-out pages provided in Enclosure 2.
One revised regulatory commitment is provided in Enclosure 3. There are no other regulatory commitments provided in this letter.
A14q
NOC-AE-12002825 Page 2 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 !2.( I Date Wencurrel chief Nuclear Officer KJT
Enclosure:
- 1. STPNOC Supplemental Response to Requests for Additional Information
- 3. Regulatory Commitments
NOC-AE-12002825 Page 3 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. O. 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-F1)
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-12002825 Enclosure I STPNOC Response to Requests for Additional Information
Enclosure 1 NOC-AE-12002825 Page 1 of 8 STPNOC Supplemental Response to Requests for Additional Information SOUTH TEXAS PROJECT, UNITS I AND 2 REQUEST FOR ADDITIONAL INFORMATION -
AGING MANAGEMENT, SET 13 (TAC NOS. ME4936 AND ME4937)
STP TLAA Exemptions (058) (References 2 & 3)
RAI 4.1-2a
Background:
In RAI 4.1-2 the staff asked the applicant to clarify which edition of the American Society of Mechanical Engineers (ASME) Code Section was applicable to the design of the containment liners, and to clarify whether the design code of record for the liners required a metal fatigue analysis. In the applicant's response to RAI 4.1-2 (November 21, 2011), the applicant provided its basis on why a fatigue analysis was not needed to be performed for the containment liners, based on their ASME Section III, Division 2 design code. The applicant stated that this design code did not require the liners to be analyzed to ASME III NE-3000 requirements, and therefore that the current licensing basis (CLB) did not include a fatigue analysis for the containment liners.
Issue:
The staff has confirmed the accuracy of the information in the applicant's response to RAI 4.1-2 through an audit of the applicant's design specification for the STP containment liner, penetrations, airlocks, and equipment hatches. However the design specification states that the "requirements for an 'analysis of cyclical loading' will be investigated in accordance with Section NE-3222.4 and NE-3121 ... of the ASME Code Section II1." Thus, the staff needs further clarification on whether the fatigue analysis statement in the design specification was only applicable to those containment components designed to ASME Code Section III, Division 1 requirements (e.g., the containment penetrations) or whether the fatigue analysis statement in the design specification is also applicable to the containment liners that were designed to ASME Code Section III, Division 2 requirements.
Request:
Clarify whether the fatigue analysis statement in the containment liner design specification is only applicable to those components in the specification that were designed to ASME Code Section III, Division 1 requirements (e.g., the containment penetrations) or whether the fatigue analysis statement is also applicable to the containment liners as well, which were designed to ASME Code Section III, Division 2 requirements.
Enclosure 1 NOC-AE-12002825 Page 2 of 8 If the fatigue analysis statement in the design specification is applicable to the containment liners, clarify whether the liners would have been required to be analyzed for a fatigue analysis in accordance with the ASME Section III NE-3222.4 and NE-3121 code paragraphs, or else, provide clarification on whether the liners were exempted from a fatigue analysis in accordance with the fatigue waiver provision in NE-3222.4(d).
If the NE-3222.4 code provisions are applicable to containment liners, provide your justification on why the fatigue analysis or fatigue waiver analysis (whichever is applicable to the liners) would not need to be identified as a TLAA, when compared to the six criteria for TLAAs in 10 CFR 54.3.
STPNOC Response:
The code jurisdiction for the design of the concrete containment and steel liner is clarified in the STP Design Criteria for the containment building (Section 3.2, "Code Jurisdiction", of Design Criteria SQ-1005, Revision 3, "Reactor Containment Building"),
which says:
A. The prestressed concrete shell and dome, together with the reinforced concrete mat forming the pressure boundary, shall be designed in accordance with the ASME Code,Section III, Division 2.
B. The carbon steel liner plate, together with the brackets supporting the polar crane runway girders and rail accessories, shall be designed according to the ASME Code,Section III, Division 2.
C. The equipment hatch, personnel airlock, and auxiliary personnel airlock, together with all mechanical and electrical penetration sleeves, are classified as ASME Section III, Division 1, Class MC components.
Consistent with the above, the liner design specification reviewed by the NRC staff states in Section 1.1.2.3.2 of the specification that the liner "shall serve as a leak-tight membrane (but not as a pressure vessel)".
Paragraph CC-3760 ("Fatigue") of ASME Section III, Division 2 (ASME-ACI 359) states:
In general, the design of metallic liners is not fatigue controlled, since most stress and strain changes will occur only a small number of times and/or produce only minor stress-strain fluctuations. ... Nevertheless, because of the critical nature of the metallic liner, the designer shall ensure the suitability of the metallic liner for the specific operating conditions involving cyclic application of loads and thermal conditions that have been establishedin the Design Specification. The fatigue methods and limits established by Section III, Division 1 shall apply.
[Italics added]
STP concludes that the fatigue analysis requirement in paragraph CC-3760 is applicable only to the portions of the liner designated in the design specification as critical pressure-retaining class MC elements, i.e. the openings and penetrations because:
Enclosure 1 NOC-AE-12002825 Page 3 of 8
- The Code refers back to the Design Specification;
- The Code states that the fatigue analysis is required because of the critical nature of the metallic liner; and
" The Code specifically requires use of Division 1 methods for performing fatigue analysis.
Accordingly, there is no fatigue analysis of the metallic liner, other than at openings and penetrations.
A review of the containment liner plate design report verifies that ASME Section III NE-3222.4 and NE-3121 are not applicable to the containment liner. Therefore, there is no associated TLAA.
RAI 4.1-3a Backgqround:
In the applicant's response to RAI 4.1-3 (November 21, 2011), the applicant indicated that the design basis information in the Updated Final Safety Analysis Report (UFSAR)
Section 5.2.3.3.2 provides the applicant's design basis for addressing underclad cracking in the reactor vessel nozzles made from SA-508, Class 2 forging materials.
The applicant also stated that the referenced "special evaluation" UFSAR Section 5.3.1.2 does not need to be identified as a TLAA because the regulatory position in NRC RG 1.43 for qualifying clad-to-forging weld qualification tests do not account for an aging mechanism or involve a time-dependent aging parameter. The staff's original request for additional information (RAI) 4.1-3 provides a more detailed background and summary of the staffs initial concern regarding this issue.
Issue:
In its response to RAI 4.1-3, the applicant based its "absence of a TLAA" conclusion for the RV SA-508 Class 2 forging components on the criteria that were established in RG 1.43 and not on the activities or analyses that were implemented in the CLB in order to conform to the weld qualification test criteria in RG 1.43. Nor was the applicant's conclusion based on a comparison of these activities or evaluations to the criteria for identifying TLAAs in 10 CFR 54.3.
Request:
Summarize and describe in sufficient detail the type of tests or evaluations that were performed as part of the CLB in order to meet the recommended weld qualification criteria RG 1.43. If an analysis, evaluation, or calculation was performed as part of the CLB for STP's weld qualification basis, clarify how the applicable document of record compares to each of the six (6) criteria for TLAAs in 10 CFR 54.3, and identify whether
Enclosure 1 NOC-AE-12002825 Page 4 of 8 the analysis, evaluation or calculation needs to be identified as a TLAA in accordance with 10 CFR 54.21(c)(1). Justify the basis for your determinations and conclusions.
STPNOC Response:
STP reevaluated the issue of intergranular separation in the heat-affected zone of reactor vessel low-alloy steel under austenitic stainless steel (SS) cladding as a potential TLAA and conservatively dispositioned this as a TLAA in accordance with 10 CFR 54.21 (c)(1)(i). WCAP-1 5338-A, A Review of Cracking Associated with Weld Deposited Cladding in OperatingPWR Plants, documents that underclad cracking does not represent a challenge to reactor vessel integrity for an operating term of 60 years.
WCAP-1 5338-A concludes that in the presence of underclad cracks, the maximum expected flaw predicted by the crack growth analysis is less than the ASME Section Xl allowable flaw size. WCAP-15338-A uses 1.5 times the numbers of cyclic and transient loads assumed for the original 40-year life which bounds the numbers of cycles projected over 60 years. The cyclic and transient loads used in WCAP-1 5338-A bound those expected in the STP pressure vessels for the 60-year life as shown in LRA Table 4.3-2 This TLAA is dispositioned in accordance with 10 CFR 54.21(c)(1)(i).
LRA Section 3.1.2.2.5, Section 4.7.4, Table 4.1-1 and Table 4.1-2 are revised, and LRA Appendix A3.6.5 is added to disposition intergranular separation in the heat-affected zone (HAZ) of reactor vessel low-alloy steel under austenitic SS cladding as a TLAA in accordance with 10 CFR 54.21(c)(1)(i). provides the line-in/line-out revision for changes to LRA Sections 3.1.2.2.5 and 4.7.4 and to Tables 4.1-1 and 4.1-2. Enclosure 2 also provides the lined-in new LRA Appendix A3.6.5.
Enclosure 1 NOC-AE-12002825 Page 5 of 8 STPNOC Supplemental Response to Requests for Additional Information SOUTH TEXAS PROJECT, UNITS I AND 2 REQUEST FOR ADDITIONAL INFORMATION -
AGING MANAGEMENT, SET 14 (TAC NOS. ME4936 AND ME4937)
References 4 & 5 RAI B2.1.9-2a Backgqround:
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.
Enclosure 1 NOC-AE-12002825 Page 6 of 8 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:
The locations managed for cavitation erosion in the essential cooling water (ECW) system are the piping flange connections at the ECW throttle valves. The 30-inch aluminum bronze ECW pipe is welded to a 30-inch slip-on carbon steel flange that bolts to the ECW throttle valve. The Open-Cycle Cooling Water System program (B2.1.9) manages the piping and slip-on flanges for loss of material due to cavitation erosion.
LRA Appendix B2.1.9, Table A4-1, and the LRA Basis Document, XI.M20, Open-Cycle Cooling Water System program are revised to address cavitation erosion at these locations.
Program Elements 3 and 4 are revised to clarify that inspection of the aluminum bronze piping and slip-on flanges downstream of the throttle valves for cavitation erosion are being performed every five years. The inspections verify that affected areas are acceptable until the next inspection period.
Program Element 7 is revised to include an enhancement that requires a condition report and an engineering evaluation to determine the extent and depth of as-found cavitation erosion. The engineering evaluation is to determine if the affected areas are acceptable for continued operation until the next inspection period. If the engineering evaluation determines unacceptable loss of material, the component is repaired or replaced.
Appendix B 2.1.9 Operating Experience is revised to discuss the operating experience associated with cavitation erosion. The operating experience associated with through-wall de-alloying is deleted. Through-wall de-alloying operating experience is addressed in aging management program B2.1.37 "Selective Leaching of Aluminum Bronze".
Table A4-1 Item 4 is revised to add commitments to require loss of material in piping and protective coating failures be documented in the corrective action program and require an engineering evaluation be performed when loss of material in piping or protective coating failures is identified.
The terms "erosion" and "erosion corrosion" are used to describe loss of material in piping and piping components due to several mechanisms, such as cavitation erosion, impingement, and flow erosion. RAI B2.1.9-2 requested information regarding the cavitation observed at the component cooling water (CCW) heat exchanger ECW return throttle valves during the Aging Management Program Audit walkdown and the cavitation erosion documented in condition reports. The response to RAI B2.1.9-2 inadvertently stated that erosion has not been found in other systems. However, various
Enclosure 1 NOC-AE-12002825 Page 7 of 8 types of erosion have been found in other systems. As noted in the response to RAI B2.1.6-1 a, the components in these systems that are subject to erosion are managed by the Flow-Accelerated Corrosion (FAC) program as susceptible non-modeled lines. provides the line-in/line-out revision to LRA Appendix B2.1.9. Enclosure 3 provides the line-in/line-out revisions to LRA Table A4-1 Item 4.
RAI B2.1.9-4a
Background:
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:
The coated locations in the essential cooling water (ECW) system managed for cavitation erosion are the piping flange connections to the ECW throttle valves. The 30-inch aluminum bronze pipe is welded into a 30-inch slip-on carbon steel flange that bolts to the ECW throttle valve. Belzona coating is used sacrificially to minimize cavitation erosion of the aluminum bronze pipe that is internal to the slip-on carbon steel flange. The purpose of the coatings is to extend the service life of the aluminum bronze pipe before replacement of the slip-on flange becomes necessary. The coatings are
Enclosure 1 NOC-AE-12002825 Page 8 of 8 replaced, as needed, during the five-year preventive maintenance inspections. The Belzona coating is considered a short-lived commodity.
The Open-Cycle Cooling Water System program manages the piping and slip-on flanges using preventive maintenance inspections every five years. The program does not determine the ultimate lifetime of the slip-on flanges. The program inspects for erosion of the aluminum bronze piping inside the slip-on flanges. The corrective action program is used to document erosion found during inspections. An engineering evaluation is performed to determine the extent and depth of the erosion and whether the affected areas are acceptable for continued operation during the following five-year period. If the engineering evaluation determines unacceptable loss of material, the aluminum bronze piping and slip-on flange are repaired or replaced.
Beginning in 2007, the first five-year inspection for the six ECW trains found some locations of eroded coatings due to cavitation erosion to the bare aluminum bronze metal pipe. The loss of material was evaluated and considered superficial. The eroded areas were recoated and the system was returned to service. ECW Train 2A was inspected in the second five-year period. Corrosion in the carbon steel gasket seating area resulted in replacement of the slip-on flange and a section of aluminum bronze piping. The second five-year period inspections of the remaining five ECW trains are scheduled for second quarter of 2012 and first quarter of 2013.
The ECW pump casings, diffuser, flanges, and discharge elbows are coated with Belzona to minimize loss of pump performance from flow erosion of the internal pump components. The Open-Cycle Cooling Water System program manages the ECW pumps and discharge piping reducers that are inspected during pump disassembly for refurbishment. ECW pump refurbishment is managed by the Major Pump and Motor Maintenance Plan. The next cycle of pump refurbishments is planned to start in 2012 and be completed in 2021. Thereafter, STP expects to refurbish the ECW pumps approximately every 10 years. The corrective action program is used to address erosion found during inspections. An engineering evaluation is performed to determine the extent and depth of the erosion and if the affected areas are acceptable for continued operation. If the engineering evaluation determines loss of material is unacceptable, the components are repaired or replaced.
ECW pump inspections have found the coatings intact with some coating discoloration on the pump columns. Blistering of the coatings has been found on the pump diffuser, flanges, and discharge elbow that are two-phase aluminum bronze alloy castings. The blistering is caused by buildup of corrosion products under the coating. Loss of material due to flow erosion has not been observed. Areas of blistering are cleaned and recoated.
The Open-Cycle Cooling Water System program is effectively managing the aging effects for cavitation erosion in the ECW system. The area susceptible to cavitation erosion in the ECW system is being inspected, evaluated, and repaired or replaced (if required) on an on-going basis such that there will be no loss of system or component intended functions.
Enclosure 2 NOC-AE-12002825 Enclosure 2 STPNOC LRA Changes with Line-inlLine-out Annotations
Enclosure 2 NOC-AE-12002825 Page 1 of 9 List of Revised LRA Sections RAI Affected LRA Section 4.1.3a Section 3.1.2.2.5 Section 4.7.4 Table 4.1 -1 Table 4.1-2 Appendix A.3.6.5 B2.1.9-2a Appendix B2.1.9
Enclosure 2 NOC-AE-12002825 Page 2 of 9 3.1.2.2.5 Crack Growth due to Cyclic Loading An analysis of crack growth of underclad flaws in reactor vessel forgings due to cyclic loading to qualify them for the current licensed operating period would be a TLAA.
TLAAs are evaluated in accordance with 10 CFR 54.21(c)(1). No u'ndercad flaws have been detected or analyzed for the STP vessel and therefore i, not a TLAA. Section 4.7.4 describes the evaluation of this effect in the STP reactor vessel for the period of extended operation.
Enclosure 2 NOC-AE-12002825 Page 3 of 9 4.7.4 Absonco of a TL--A. for-Reactor Vessel Underclad Cracking Analyses Summary Description NUREG-1800 identifies "Intergranular separation in the heat-affected zone (HAZ) of reactor vessel low-alloy steel under austenitic SS cladding" as a potential TLAA. No such crGcks have becn discGvered at STP, nor analyzed, in the absence of which no su-ch TLA*A exists. This phenomenon has also been addressed in the STP vessels by weld cladding processes designed to avoid these defects, consistent with Regulatory Guide 1.43, Control of Stainless Steel Weld Cladding of Low Alloy Steel Components.
WCAP-15338-A demonstrates that the vessel inteqrity is maintained in the presence of underclad cracks. No cracks have been detected in the underclad of STP vessels.
Analysis Westinghouse summarized fatigue crack growth analyses and ASME Section Xl allowable flaw size evaluations for typical Westinghouse vessels.
Underclad cracks were first discovered in October 1970 during examination of the Atucha reactor vessel. They have been reported to exist only in SA-508, Class 2 reactor vessel forgings manufactured to a coarse grain practice and clad by high-heat-input submerged arc processes.
The question of the existence of a TLAA for underclad cracking rests on (1) the susceptibility of the STP reactor nozzles, safe ends, flanges, and top and bottom head cap forgings to this phenomenon, and (2) on the detection of any such cracks in the STP vessels. Neither the Westinghouse report nor the NRC staff safety evaluation of it requires an inspection to detect such cracks. No cracks have been detected in the STP vessels underclad, nor therefore have any been analyzd. in the absence of an analysis, no TLA. exists.
South Texas Vessel Materialthat Might be Subject to UndercladCracking At STP only the vessel carbon steel forgings are SA-508 Class 2. The clad is stainless steel weld metal, Analysis A-7; and Ni-Cr-Fe Weld Metal, F-Number 43.
The STP ISI program examines flanges under IWB Table 2500-1 Category B-A, and examines RV nozzles under Category B-D. A review of the Examination Reports found no record of indications in the RV nozzles or flanges.
Qualificationof Clad Welding Processes to Avoid UndercladCracking Although the STP vessels contain these SA-508 forgings clad by high-heat-input processes, the procedure qualification for cladding low alloy steel (SA-508 Class 2) requires a special evaluation to assure freedom from underclad cracking.
Westinghouse meets the intent of RG 1.43 by requiring qualification of any high-heat process, such as the submerged-air wide-strip welding process and the submerged-arc-6-wire process used on SA-508 Class 2 material, with a performance test as described
Enclosure 2 NOC-AE-12002825 Page 4 of 9 in regulatory position 2 of the guide. No qualifications are required by the RG for SA-533 material and equivalent chemistry for forging grade SA-508 Class 3 material.
Production welding is monitored to ensure that essential variables remain within the limits established by the qualification. If the essential variables exceed the qualification limits, an evaluation will be performed to determine if the cladding is acceptable for use.
Applicability of Westinghouse Generic 60-Year Flaw Growth Analysis to South Texas Westinghouse topical report WCAP-15338-A reports a generic 60-year flaw growth analysis which assumes 1.5 times the number of 40-year design basis cycles and found that the expected maximum flaw predicted by the crack growth analysis is less than the ASME Section Xl allowable flaw size. It therefore demonstrated that these effects are acceptable for a 60-year life. The NRC safety evaluation of this topical report determined that it might be incorporated by reference in a license renewal application, provided that the analysis is applicable to the applicant's plant, specifically (1) that the cyclic and transient loading assumptions of the topical report bound those expected by the licensee for a 60-year life; and (2) that this evaluation be described in the application, including the description of supporting programs in the UFSAR supplement.
This Weistinghouse topical rpor"t coul d be applied to For STP, (1) Tthe cyclic and transient load assumptions of this topical report bound those expected in the STP vessels for the 60-year life as demonstrated in LRA Table 4.3-2; and (2) LRA Appendix A3, the UFSAR supplement, provides a description of the evaluation of TLAA for the period of extended operation. if invoked, the topical rFepot would be a TLI. valid for the period of evtended operation. However, in the absence of under,,ad cGraks requi in*
this analysis, the topical report has not been applied to STP. This report is thereforo not part of the STP CL1 and i0s ot a TLAA by 10 CFIR 54.3(a), CriterFin 6.
WCAP-15338-A addresses the aging mechanism of underclad cracking. It is a TLAA, which is valid for the period of extended operation and dispositioned in accordance with 10 CFR 54.21(c)(1)(i).
Disposition: Validation, 10 CFR 54.21 (c)(1)(i)
Enclosure 2 NOC-AE-12002825 Page 5 of 9 Table 4.1-1 List of TLAAs TLAA Disposition Report Category Descripton Category(1 ) Section TLAA for the Corrosion Effects in the Essential Cooling iii 4.7.3 Water (ECW) System Absence of aTLA*, for Reactor Vessel Underclad 4.7.4
-Cracking Analyses Reactor Coolant Pump Flywheel Fatigue Crack Growth i 4.7.5
_Analysis Table 4.1-2 Review of Analyses Listed in NUREG-1800, Tables 4.1-2 and 4.1-3 NUREG-1800'Examples, , Applicability to-STP : Section NUREG-1800, Table 4.1 Additional Examples of Plant-Specific TLAAs Intergranular separation in the heat-affected zone No No 14XAZ analyses were identified within (HAZ) of reactor vessel low-alloy steel under .. G.B-Yes
.-
austenitic SS cladding _Ye Low-temperature overpressure (LTOP) analyses Yes
Enclosure 2 NOC-AE-1 2002825 Page 6 of 9 A3.6.5 Reactor Vessel Underclad Cracking Analyses Reactor vessel underclad cracking has been addressed in the STP vessel low-alloy steel (SA-508, Class 2) forgings by weld cladding processes designed to avoid these defects, consistent with Regulatory Guide 1.43. WCAP-1 5338-A found that the maximum flaw predicted by the crack growth analysis is less than the ASME Section Xl allowable flaw size and does not represent a challenge to reactor vessel integrity for an operating term of 60 years. WCAP-15338-A assumes 1.5 times the numbers of cyclic and transient loads assumed for the original 40-year life which bounds the numbers of cycles projected in 60 years. This TLAA is dispositioned in accordance with 10 CFR 54.21(c)(1)(i).
Enclosure 2 NOC-AE-12002825 Page 7 of 9 B2.1.9 Open-Cycle Cooling Water System Program Description The Open-Cycle Cooling Water (OCCW) System program manages loss of material and reduction of heat transfer for components in scope of license renewal and exposed to the raw water of the essential cooling water (ECW) and essential cooling water screen wash system. The program includes surveillance techniques and control techniques to manage aging effects caused by biofouling, corrosion, erosion, cavitation erosion, protective coating failures and silting in components of the ECW system, and structures and components serviced by the ECW system, that are in scope of license renewal.
The program also includes periodic inspections to monitor aging effects on the OCCW structures, systems and components, component cooling water heat exchanger performance testing, and inspections of the other safety related heat exchangers cooled by the ECW System, to ensure that the effects of aging on OCCW components are adequately managed for the period of extended operation. The program also includes inspections of a sample of ECW piping for wall thickness prior to the period of extended operation. Subsequent inspections will be scheduled based on the results of the initial inspections. Components within the scope of the OCCW System program are:
- 1) components of the ECW system that are in scope of license renewal and 2) the safety-related heat exchangers cooled by the ECW system: component cooling water heat exchangers, diesel generator jacket water heat exchangers, diesel generator lube oil coolers, diesel generator intercoolers, essential chiller condensers, and component cooling water pump supplementary coolers. The program is consistent with STPNOC commitments established in responses to NRC Generic Letter 89-13, Service Water System ProblemsAffecting Safety-Related Components.
The surveillance techniques utilized in the Open-Cycle Cooling Water System program include visual inspection, volumetric inspection, and thermal and hydraulic performance monitoring of heat exchangers. The control techniques utilized in the Open-Cycle Cooling Water System program include (1) water chemistry controls to mitigate the potential for the development of aggressive cooling water conditions, (2) flushes and (3) physical and/or chemical cleaning of heat exchangers and of the ECW pump suction bay to remove fouling and to reduce the potential sources of fouling.
Additional measures used to manage loss of material due to selective leaching for aluminum bronze components in the ECW system are detailed in the plant-specific aging management program Selective Leaching of Aluminum Bronze (B2.1.37).
NUREG-1801 Consistency The Open-Cycle Cooling Water System program is an existing program that, following enhancement, will be consistent with exception to NUREG-1801,Section XI.M20, Open-Cycle Cooling Water System.
Enclosure 2 NOC-AE-12002825 Page 8 of 9 Exceptions to NUREG-1801 Program Elements Affected:
Preventive Actions (Element 2), ParametersMonitored or Inspected (Element 3),
Detection of Aging Effects (Element 4)
NUREG-1801,Section XI.M20, Elements 2, 3 and 4, provide for a program of flushing and inspection to confirm that fouling and degradation of surfaces is not occurring. An exception is taken to flushing the ECW train cross-tie dead legs and inspecting the interior of these lines. Instead, the external surfaces of the cross-tie lines are included in the six month dealloying visual external inspection walkdowns. The cross-tie valves and piping are also included in the essential cooling water system inservice pressure test, which includes VT-2 inspections of these components. Measures used to manage loss of material due to selective leaching are detailed in the Selective Leaching of Aluminum Bronze program (B2.1.37). These inspections and tests provide confidence in the ability to detect leakage in the piping and valves. The cross-tie lines do not have an intended function and are not required for any accident scenario within the design basis of the plant. The cross-tie valves are maintained locked closed.
Enhancements Prior to the period of extended operation, the following enhancements will be implemented in the following program elements:
ParametersMonitored or Inspected (Element 3) and Detection of Aging Effects (Element 4)
Procedures will be enhanced to include visual inspection of the strainer inlet area and the interior surfaces of the adjacent upstream and downstream piping. Material wastage, dimensional change, discoloration, and discontinuities in surface texture will be identified. These inspections will provide visual evidence of loss of material and fouling in the ECW system and serve as an indicator of the condition of the interior of ECW system piping components otherwise inaccessible for visual inspection. Procedures will also be enhanced to include the acceptance criteria for this visual inspection.
Scope (Element 1), ParametersMonitored or Inspected (Element 3), Detection of Aging Effects (Element 4), and Monitoring and Trending (Element 5)
Procedures will be enhanced to require a minimum of 25 ECW piping locations be measured for wall thickness. Selected areas will include locations that are considered to have the highest corrosion rates, such as areas with stagnant flow.
Corrective Actions (Element 7)
Procedures will be enhanced to require loss of material in piping and protective coating failures be documented in the corrective action program. The resolution will include an enqineerinq evaluation of the condition.
Enclosure 2 NOC-AE-12002825 Page 9 of 9 Operating Experience Industry operating experience evaluations, Maintenance Rule Periodic Assessments, and OCCW component performance testing results have shown that the effects of aging are being adequately managed.
A review of the STP plant specific operating experience indicates that macrofouling, general corrosion, erosion corrosion, and through wall d*all-yi, g cavitation erosion have been observed in aluminum bronze components. STP has analyzed the effects of the through wall do alloying and found that the degradation is slow so that rapido catastrophic failure is not a consideration, and deter*ined that the leakage can be detected before the flaw reaches a limiting size that would affecst the intended functions of the essential cooling water and essential cooling water screen wash system. A long ran improvement plan and engineering evaluation were developed to deal with the de alloying of aluminum bFroze components. Based on these analyses, the approach has becn to evaluate components, and schedule replacement by the corrective action4 program. Components with indications of through wall de alloying, greater than one inch, will be replaced by the end of the next refueling outage. A monitoring and inspection programn provides confidence in the ability to detect the leakage.
In 2001 plant inspections of the ECW pumps revealed signs of flow erosion and corrosion on the pump internal and external surfaces. The pump vendor recommended application of Belzona coating to provide protection against erosion and corrosion and the coating was applied to the internal wetted surfaces of all ECW pumps. Use of Belzona has improved pump performance and service life of the components.
In May 2005, damage was discovered in the slip-on flange immediately downstream of the component cooling water heat exchanger 1 B ECW return throttle valve. The damage was due to cavitation erosion. The corresponding locations in the other ECW trains were inspected. The damaged areas of all six trains were replaced or reworked in accordance with the applicable codes and piping specifications. A design modification was performed to coat the affected areas with Belzona, and PMs were generated to perform regular inspections. The use of Belzona for mitigating cavitation erosion has been successful in prolonging service life of the components.
The OCCW System program operating experience information provides objective evidence to support the conclusion that the effects of aging are adequately managed so that the structure and component intended functions are maintained during the period of extended operation.
NRC Generic Letter 89-13 was based on industry operating experience and forms the basis for the STP OCCW System program.
Conclusion The continued implementation of the Open-Cycle Cooling Water System 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.
Enclosure 3 NOC-AE-12002825 Enclosure 3 Regulatory Commitments
Enclosure 3 NOC-AE-12002825 Page 1 of 1 A4 LICENCE RENEWAL COMMITMENTS Table A4-1 identifies proposed actions committed to by STPNOC for STP Units 1 and 2 in its License Renewal Application. These and other actions are proposed regulatory commitments. This list will be revised, as necessary, in subsequent amendments to reflect changes resulting from NRC questions and STPNOC responses. STPNOC will utilize the STP commitment tracking system to track regulatory commitments. The Condition Report (CR) number in the Implementation Schedule column of the table is for STPNOC tracking purposes and is not part of the amended LRA.
Table A4-1 License Renewal Commitments Item # Item
- ::i- Commitment Commitment:* :LRA >i! Implementation Section, Schedule 4 Enhance the Open-Cycle Cooling Water System program procedures to: B2.1.9 Prior to the period of
" include visual inspection of the strainer inlet area and the interior surfaces of the extended operation adjacent upstream and downstream piping. Material wastage, dimensional change, discoloration, and discontinuities in surface texture will be identified. These inspections CR 10-23256 will provide visual evidence of loss of material and fouling in the ECW system and serve as an indicator of the condition of the interior of ECW system piping components otherwise inaccessible for visual inspection.
- include the acceptance criteria for this visual inspection.
- require a minimum of 25 ECW piping locations be measured for wall thickness prior to the period of extended operation. Selected areas will include locations considered to have the highest corrosion rates, such as areas with stagnant flow.
- require loss of material in piping and protective coating failures be documented in the corrective action progqram, and
- require an engineering evaluation be performed when loss of material in piping or protective coating failures is identified..