ML12073A106
| ML12073A106 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 03/05/2012 |
| From: | Rencurrel D South Texas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NOC-AE-12002809, TAC ME4936, TAC ME4937, STI: 33372978 | |
| Download: ML12073A106 (15) | |
Text
Nuclear Operating Company C7L7 LT:ý South Texas Pro/ect Electric Generating Station P.O. Box 289 Wadsworth, Texas 77483
-v-
-I March 5, 2012 NOC-AE-12002809 10 CFR 54 STI: 33372978 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 Revised Response to Requests for Additional Information for the South Texas Project License Renewal Application Aqinq Mana qement Pro qram, Set 10 (RAI 4.7.3-2) (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) (ML103010257)
- 2. NRC letter dated December 14, 2011, "Requests for Additional Information for the Review of the South Texas Project, Units 1 and 2 License Renewal Application -
Aging Management, Set 10 (TAC Nos. ME4936 and ME 4937)"(ML11332A100)
- 3. STPNOC letter dated February 6, 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 10 (RAI 4.7.3-2) (TAC Nos. ME4936 and ME 4937)" (NOC-AE-12002786) (ML12041A170)
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 (RAI), including RAI 4.7.3-2, for review of the STP LRA.
By Reference 3, STPNOC provided a response to RAI 4.7.3-2. The response provided in Reference 3 is retracted. Enclosure 1 to this letter provides a revised response to RAI 4.7.3-2. LRA changes described in Enclosure 1 are depicted in 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.
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.
NOC-AE-12002809 Page 2 I declare under penalty of perjury that the foregoing is true and correct.
Executed on 3 Is- /2
/ 1, Date W1currel Senior Vice President, Technical Support & Oversight KJT
Enclosure:
NOC-AE-12002809 Page 3 cc:
(paper copy)
(electronic copy)
Regional Administrator, Region IV U. S. Nuclear Regulatory Commission 1600 East Lamar Boulevard Arlington, Texas 76011-4511 Balwant K. Singal Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint North (MS 8B1) 11555 Rockville Pike Rockville, MD 20852 Senior Resident Inspector U. S. Nuclear Regulatory Commission P. 0. Box 289, Mail Code: MN1 16 Wadsworth, TX 77483 C. M. Canady City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704 John W. Daily License Renewal Project Manager (Safety)
U.S. Nuclear Regulatory Commission One White Flint North (MS 011-Fl)
Washington, DC 20555-0001 Tam Tran License Renewal Project Manager (Environmental)
U. S. Nuclear Regulatory Commission One White Flint North (MS O11F01)
Washington, DC 20555-0001 A. H. Gutterman, Esquire Kathryn M. Sutton, Esquire Morgan, Lewis & Bockius, LLP John Ragan Chris O'Hara Jim von Suskil NRG South Texas LP Kevin Polio Richard Pena City Public Service Peter Nemeth Crain Caton & James, P.C.
C. Mele City of Austin Richard A. Ratliff Alice Rogers Texas Department of State Health Services Balwant K. Singal John W. Daily Tam Tran U. S. Nuclear Regulatory Commission NOC-AE-12002809 Enclosure I STPNOC Revised Response to RAI 4.7.3-2 NOC-AE-12002809 Page 1 of 2 STPNOC Revised Response to RAI 4.7.3-2 SOUTH TEXAS PROJECT, UNITS I AND 2 REQUEST FOR ADDITIONAL INFORMATION -
AGING MANAGEMENT, SET 10 (TAC NOS. ME4936 AND ME4937)
RAI 4.7.3-2 (066)
Background:
In a letter dated September 21, 2011, the staff issued RAI 4.7.3-1, requesting that the applicant state how visual inspections in the Open-Cycle Cooling Water System program are capable of ensuring that corrosion in the essential cooling water (ECW) system will not exceed the 40-mil corrosion allowance, given that LRA Section 4.7.3 documented the use of this program as the disposition for the related TLAA.
In its response dated November 21, 2011, the applicant stated that ECW corrosion is managed consistent with NRC Generic Letter 89-13. The applicant also stated that, when visual inspections identify corrosion, thickness measurements are taken as part of the corrective action program.
Issue:
The staff lacks sufficient information to conclude that visual inspections alone will be capable of prompting follow-up thickness measurements such that the 40-mil corrosion allowance will not be exceeded during the period of extended operation. The staff believes that visual examinations may need to be augmented with physical measurements, using tools such as inside calipers, to ensure that corrosion is not approaching the limit. Given that physical measurements may be required to augment the visual inspections, the staff requires further details on how the program will manage this TLAA, such as how often physical measurements will be conducted, how many locations will be checked, how the most susceptible location will be selected, what devices will be used, and the criteria that would result in a follow-up volumetric examination.
Request:
- 1. State how visual inspections of the ECW system, without augmented physical measurements, will be capable of detecting a 40-mil loss of material.
- 2. Alternatively, state what augmented inspection techniques will be used to detect loss of material.
Include information such as how often physical measurements will be conducted, how many locations will be checked, how the most susceptible location will be selected, what devices will be used, and the criteria that would result in a follow-up volumetric examination in sufficient detail such that the staff can independently conclude that the inspection methodologies will adequately manage loss of material for this TLAA.
NOC-AE-12002809 Page 2 of 2 STPNOC Response:
RAI 4.7.3-2 Revised Response:
South Texas Project has re-evaluated the TLAA associated with corrosion of Class 3 ECW piping and determined that the TLAA remains valid for the period of extended operation. Loss of material due to corrosion will be managed by the Open-Cycle Cooling Water System program (B2.1.9) using volumetric inspections. This TLAA is dispositioned in accordance with 10 CFR 54.21 (c)(1)(iii).
LRA Appendix A1.9, Appendix B2.1.9 and LRA Basis Document XI.M20 (B2.1.9), Open-Cycle Cooling Water System program is revised to measure wall thickness of a sample of ECW piping, using volumetric inspections, prior to the period of extended operation. The rate of wall thinning will be calculated from the results of the measurements, and subsequent inspections will be scheduled prior to the pipe wall thickness reaching minimum allowable wall thickness.
The sample size will include a minimum of 25 locations. The location of the inspections will be selected based on engineering evaluation of the system and will include locations considered to have the highest corrosion rates, such as areas of stagnant flow.
If component wall thickness is found unacceptable, an engineering analysis is performed to determine acceptable safety margin for continued operation. Components with unacceptable safety margin will be isolated, repaired, or replaced. Extent of condition will be determined through the Corrective Action Program.
LRA Table 3.3.2-4 is revised to include an aging management review line for the management of the TLAA identified in LRA Section 4.7.3.
LRA Table A4-1 Item 4 is revised to include a commitment to require wall thickness measurements of a minimum of 25 ECW piping locations 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. provides the line-in/line-out revisions for the changes to Appendices A1.9 and B2.1.9, and LRA Table 3.3.2-4. provides the line-in/line-out revisions to LRA Table A4-1 Item 4.
NOC-AE-12002809 STPNOC LRA Changes with Line-inILine-out Annotations NOC-AE-12002809 Page 1 of 6 List of Revised LRA Section RAI Affected LRA Section RAI 4.7.3-2 A1.9 B2.1.9 Table 3.3.2-4 A4-1 Item 4 (See Enclosure 3)
Note: Because the response provided in Reference 3 to this letter is retracted, LRA Section 4.7.3 remains as it appears in the original LRA (Reference 1).
NOC-AE-12002809 Page 2 of 6 A1.9 OPEN-CYCLE COOLING WATER SYSTEM The Open-Cycle Cooling Water System program manages loss of material7 and reduction of heat transfer for components within the scope of license renewal and exposed to the raw water of the essential cooling water system. Included are components of the essential cooling water (ECW) system that are within the scope of license renewal, the component cooling water heat exchangers and the other safety related heat exchangers cooled by the essential cooling water system. The program includes chemical treatment and control of biofouling, periodic inspections, flushes and physical and chemical cleaning, and heat exchanger performance testing/ inspections to ensure that the effects of aging will be managed during 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. The program is consistent with STP commitments as established in responses to NRC Generic Letter 89-13, Service Water System Problems Affecting Safety-Related Components.
NOC-AE-12002809 Page 3 of 6 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, 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 Problems Affecting Safety-Related Components.
The surveillance techniques utilized in the Open-Cycle Cooling Water System program include visual inspection, volumetric inspection, and with-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.
NOC-AE-12002809 Page 4 of 6 Exceptions to NUREG-1801 Program Elements Affected:
Preventive Actions (Element 2), Parameters Monitored 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:
Parameters Monitored 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), Parameters Monitored 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.
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 de-alloying have been observed in aluminum bronze components. STP has analyzed the effects of the through-wall de-alloying and found that the degradation is slow so that rapid or catastrophic failure is not a consideration, and NOC-AE-12002809 Page 5 of 6 determined that the leakage can be detected before the flaw reaches a limiting size that would affect the intended functions of the essential cooling water and essential cooling water screen wash system. A long range improvement plan and engineering evaluation were developed to deal with the de-alloying of aluminum bronze components. Based on these analyses, the approach has been to evaluate components, and schedule replacement by the corrective action 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 program provides confidence in the ability to detect the leakage.
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.
NOC-AE-12002809 Page 6 of 6 Table 3.3.2-4 Auxiliary Systems - Summary of Aging Management Evaluation - Essential Cooling Water and ECW Screen Wash System (Continued)
Component Intenfled Material Enviro0nment Aging Effect [ Aging Management`
NUREG-Table I Item,?:Notes Type Function Requiring -
Program 1801 Vol.
jManagement [_....._
2 Item
~Piping Piping LBS, PB, SIA LBS, PB, SIA Copper Alloy (Aluminum >
8%)
80/)
Raw Water (Int)
Raw Water (Int)
Raw Water (I nt)
Loss of material Loss of material iLoss of material Open-Cycle Cooling Water System (B2.1.9)
ýVIl.C1-9 3.3.1.81 B
LBS, PB, jCopper Alloy SIA (Aluminum >
8° j8%)
Time-Limited Aging Analysis evaluated for the period of extended operation ISelective Leaching of
!Aluminum Bronze
,(B2.1.37)
E, 3 VII.C1-10 3.3.1.84 NOC-AE-12002809 Regulatory Commitments NOC-AE-12002809 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 #
Commitment
- !> LRA 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.