WM 07-0077, Response to NRC Requests for Additional Information Related to Wolf Creek Generating Station License Renewal Application and Supplement to the Wolf Creek Generating Station License Renewal Application
| ML072980026 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 10/17/2007 |
| From: | Garrett T Wolf Creek |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| ET 06-0038, ET 07-0044, ET 07-0048, WM 07-0077 | |
| Download: ML072980026 (11) | |
Text
ý.LF CREEK'NUCLEAR OPERATING CORPORATION October 17, 2007 Terry J. Garrett Vice President, Engineering ET 07-0048 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
Reference:
- 1) Letter ET 06-0038, dated September 27, 2006, from T. J. Garrett, WCNOC, to USNRC 2) Letter dated September 27, 2007, from V. Rodriguez, USNRC, to T. J. Garrett 3) Letter ET 07-0044, dated September 27, 2007 from T. J. Garrett, WCNOC, to USNRC 4) Letter WM 07-0077, dated October 11, 2007, from S. E. Hedges, WCNOC, to USNRC
Subject:
Docket No. 50-482: Response to NRC Requests for Additional Information Related to Wolf Creek Generating Station License Renewal Application and Supplement to the Wolf Creek Generating Station License Renewal Application Gentlemen:
Reference 1 provided Wolf Creek Nuclear Operating Corporation's (WCNOC) License Renewal Application (LRA) for the Wolf Creek Generating Station (WCGS). Reference 2 requests additional information (RAI) regarding the WCGS LRA. The attachment provides the responses to the RAIs.The enclosure provides an updated Steam Generator Tube Integrity supplement as requested in response to RAI B2.1.8-1 and RAI B2.1.8-2.License renewal commitment number thirty-nine is closed with this submittal.
WCNOC committed to evaluate changes to the WCGS current licensing basis and update the WCGS LRA (Reference 3). Reference 4 provided an amendment to the WCGS LRA that partially satisfied commitment number thirty-nine.
The enclosure provides the remaining changes.P0. Box 411 / Burlington, KS 66839 / Phone: (620) 364-8831 An Equal Opportunity Employer M/FIHCNET/AJ U~
ET 07-0048 Page 2 of 3 If you have any questions concerning this matter, please contact me at (620) 364-4084, or Mr.Kevin Moles at (620) 364-4126.Terry J. Garrett TJG/rlt
Attachment:
Enclosure:
WCNOC Response to NRC Requests for Additional Information Supplement cc: E. E. Collins (NRC), w/a, w/e J. N. Donohew (NRC), w/a, w/e V. G. Gaddy (NRC), w/a, w/e V. Rodriguez (NRC), w/a, w/e Senior Resident Inspector (NRC), wo/a, wo/e ET 07-0048 Page 3 of 3 STATE OF KANSAS )ss COUNTY OF COFFEY )Terry J. Garrett, of lawful age, being first duly sworn upon oath says that he is Vice President Engineering of Wolf Creek Nuclear Operating Corporation; that he has read the foregoing document and knows the contents thereof; that he has executed the same for and on behalf of said Corporation with full power and authority to do so; and that the facts therein stated are true and correct to the best of his knowledge, information and belief.Terry J. /rrett Vice Prsident Engineering SUBSCRIBED and sworn to before me this 17"/day RHONDA L. TIEMEYER il-OFFIcIAL=-N tryP bi A IF I SEAL : MY COMMISSION EXPIRES Notary Public January 11,2010 Expiration Date 0'v'j //'U Attachment to ET 07-0048 Page 1 of 4 The license renewal application (LRA) states that the Steam Generator Tube Integrity aging management program (AMP) is consistent, with exceptions, to the Generic Aging Lessons Learned (GALL) Report. The GALL states, in part, that the degradation management program in Nuclear Energy Institute (NEI) initiative 97-06, "Steam Generator Tube Integrity," is adequate to manage the effects of aging of the steam generator tubes. NEI 97-06 references guideline documents developed by the Electric Power Research Institute (EPRI) for managing areas important to steam generator tube integrity including tube inspections.
The LRA discusses several exceptions taken to the EPRI guidelines.
With respect to these exceptions, please address the following:
RAI B2.1.8-1 The LRA states that the rotating pancake probe is used to inspect from 3 inches above to 3 inches below the top of the tubesheet and that the bobbin probe is used to inspect the entire engagement length of the hydraulically expanded tubesheet region. However, the bobbin probe is not qualified for inspection in this area. The application also states that there was a one-cycle license amendment request to use an alternate tube repair criteria which, in part, eliminated the need to inspect near the tube ends on the hot-leg side of the steam generator.
The EPRI guidelines indicate that the full length of the steam generator tubes requires an inspection with an inspection technique qualified for each region of the tube.The staff requests that the applicant clarify this exception to the GALL Report and the EPRI guidelines.
For example, clarify whether the exception being taken to the EPRI guidelines is that the entire tube is not inspected or whether Wolf Creek Generating Station (WCGS) is not inspecting the portions of the tube required to be inspected with techniques capable of detecting flaws that may be occurring in that region. The staff notes that the tube is required to be inspected with the objective of detecting flaws of any type and that may satisfy the applicable tube repair criteria (WCGS Technical Specification 5.5.9.d).
As a result, if cracking of the tube could occur at various locations within the tubesheet, these areas should be inspected with techniques capable of finding these flaws (and consistent with the sampling and tube integrity requirements of the technical specifications).
The staff notes that inspection near the tube ends on the hot-leg side of the steam generator is not required for refueling outage fifteen and the subsequent operating cycle (since this portion of tube is explicitly exempted from the inspection requirements in the technical specifications).
Response: This issue is no longer being tracked as an exception.
NEI 97-06, "Steam Generator Program Guidelines", and the associated EPRI Guidelines are established to perform Degradation Assessments and Condition Monitoring and Operational Assessments to ensure steam generator tube integrity.
Since the License Renewal Application was submitted, Amendment Number 164 to the Operating License was implemented to revise various Technical Specifications associated with steam generator (SG) tube integrity to adopt Rev. 4 to TSTF-449, "Steam Generator Tube Integrity." Wolf Creek Generating Station (WCGS) is in compliance with Technical Specification 5.5.9.d which states:
Attachment to ET 07-0048 Page 2 of 4"Provisions for SG tube inspections.
Periodic SG tube inspections shall be performed.
The number and portions of the tubes inspected and methods of inspection shall be performed with the objective of detecting flaws of any type (e.g., volumetric flaws, axial and circumferential cracks) that may be present along the length of the tube, from the tube-to- tubesheet weld at the tube inlet to the tube-to-tubesheet weld at the tube outlet, and that may satisfy the applicable tube repair criteria.
For Refueling Outage 15 and the subsequent operating cycle, the portion of the tube below 17 inches from the top of the hot leg tubesheet is excluded.
The tube-to-tubesheet weld is not part of the tube. In addition to meeting the requirements of d.1, d.2, and d.3 below, the inspection scope, inspection methods, and inspection intervals shall be such as to ensure that SG tube integrity is maintained until the next SG inspection.
An assessment of degradation shall be performed to determine the type and location of flaws to which the tubes may be susceptible and, based on this assessment, to determine which inspection methods need to be employed and at what locations..." Inspections are performed with techniques capable of detecting flaws at locations identified in the Degradation Assessment as susceptible.
RAI B2.1.8-2 The LRA states that the bobbin probe is used to detect primary water stress corrosion cracking at tube dents in support plates and stress corrosion cracking in free span regions. However, the bobbin probe is not qualified for detection of these degradation mechanisms when the voltage of the dent exceeds certain threshold values.The EPRI guidelines indicate that the full length of the steam generator tubes requires an inspection with an inspection technique qualified for each region of the tube.The staff requests that the applicant clarify the nature of this exception to the GALL Report and EPRI guidelines since the WCGS technical specifications require, in part, to (a) perform an assessment of the type and location of flaws to which the tubes may be susceptible and, based on this assessment, to determine which inspection methods need to be employed and at what locations; and (b) to inspect the tubes with the objective of detecting flaws that may satisfy the applicable tube repair criteria.In light of these requirements, if WCGS concluded that primary water stress corrosion cracking could occur at tube dents in support plates or outer diameter stress corrosion cracking could occur in free span regions, these regions should be inspected with techniques capable of finding these forms of degradation.
Response: This issue is no longer being tracked as an exception.
NEI 97-06, "Steam Generator Program Guidelines", and the associated EPRI Guidelines are established to perform Degradation Assessments and Condition Monitoring and Operational Assessments to ensure steam generator tube integrity.
Since the License Renewal Application was submitted, Amendment Number 164 to the Operating License was implemented to revise various Technical Specifications associated with steam generator tube integrity to adopt Rev. 4 to TSTF-449,"Steam Generator Tube Integrity." WCGS is in compliance with Technical Specification 5.5.9.d which states:
Attachment to ET 07-0048 Page 3 of 4"Provisions for SG tube inspections.
Periodic SG tube inspections shall be performed.
The number and portions of the tubes inspected and methods of inspection shall be performed with the objective of detecting flaws of any type (e.g., volumetric flaws, axial and circumferential cracks) that may be present along the length of the tube, from the tube-to-tubesheet weld at the tube inlet to the tube-to-tubesheet weld at the tube outlet, and that may satisfy the applicable tube repair criteria.
For Refueling Outage 15 and the subsequent operating cycle, the portion of the tube below 17 inches from the top of the hot leg tubesheet is excluded.
The tube-to-tubesheet weld is not part of the tube. In addition to meeting the requirements of d.1, d.2, and d.3 below, the inspection scope, inspection methods, and inspection intervals shall be such as to ensure that SG tube integrity is maintained until the next SG inspection.
An assessment of degradation shall be performed to determine the type and location of flaws to which the tubes may be susceptible and, based on this assessment, to determine which inspection methods need to be employed and at what locations..." Inspections are performed with techniques capable of detecting flaws at locations identified in the Degradation Assessment as susceptible.
RAI B2.1.8-3 The LRA indicates that the EPRI guidelines require that if active damage mechanisms are identified then all steam generators shall be examined at the end of each fuel cycle.The application also states that although WCGS currently has one active damage mechanism (i.e., wear at anti-vibration bars), only two steam generators are inspected at each refueling outage on an alternating basis so that each steam generator is examined every other refueling outage.The staff requests that the applicant confirm that WCGS has verified the acceptability of this approach each outage by confirming that tube integrity will be maintained for the period of time between the planned inspections of the steam generators (consistent with the technical specification requirements).
Response: This issue is no longer being tracked as an exception.
NEI 97-06, "Steam Generator Program Guidelines", and the associated EPRI Guidelines are established to perform Degradation Assessments and Condition Monitoring and Operational Assessments to ensure steam generator tube integrity.
In accordance with these requirements, the Condition Monitoring evaluation is performed to compare the observed tube eddy current indication parameters against structural and leakage integrity limits that are included in the pre-outage Degradation Assessment.
An Operational Assessment is also performed to project the inspection results and trends to the next inspections, and to provide reasonable assurance that the structural and leakage requirements will continue to be met during the planned operating interval.
These evaluations are conducted as required during each inspection.
Attachment to ET 07-0048 Page 4 of 4 RAI B2.1.8-4 The LRA states that structural integrity limits consistent with Regulatory Guide 1.121,"Bases for Plugging Degraded PWR Steam Generator Tubes" are applied as part of the Steam Generator Tube Integrity AMP. The staff requests that the applicant confirm that the AMP also includes the structural integrity limits contained within the WCGS technical specifications.
Response: Since the License Renewal Application was submitted, Amendment Number 164 to the Operating License was implemented to revise various Technical Specifications associated with SG tube integrity to adopt Rev. 4 to TSTF-449, "Steam Generator Tube Integrity." WCGS is in compliance with plant Technical Specifications.
Enclosure to ET 07-0048 Supplement Steam Generator Integrity Appendix B AGING MANAGEMENT PROGRAMS B2.1.8 Steam Generator Tube Integrity Program Description The scope of the Steam Generator Tube Integrity program includes the preventive measures, condition monitoring inspections, degradation assessment, repair and leakage monitoring activities necessary to manage cracking, loss of material, denting, and wall thinning.
The aging management measures employed include non-destructive examination, visual inspection, sludge removal, tube plugging, in-situ pressure testing and maintaining the chemistry environment by removal of impurities and addition of chemicals to control pH and oxygen. NDE inspection scope and frequency, and primary to secondary leak rate monitoring are conducted consistent with the requirements of WCGS Unit 1 Technical Specifications.
Structural integrity limits consistent with Regulatory Guide 1.121, Revision 0, "Bases for Plugging Degraded PWR Steam Generator Tubes" are applied.Steam generator management practices are consistent with NEI 97-06, "Steam Generator Program Guidelines." Program deviations from NEI 97-06 are prepared and approved in accordance with NEI 97-06 and EPRI steam generator management program guidance.License amendment requests to use alternate repair criteria (B*) were approved for refueling outages 14 and 15 and the subsequent operating cycles following these outages.Tube sleeves are not approved for use at WCGS and have not been used.NUREG-1801 Consistency The Steam Generator Tube Integrity program is an existing program that is consistent, with exceptions, to NUREG-1801,Section XI.M19, "Steam Generator Tube Integrity." Exceptions to NUREG-1801 Program Elements Affected Preventive Actions -Element 2 When in wet layup conditions WCGS is meeting the requirements for mixing of the steam generator bulk solution and ensuring adequate sample line flush times are employed.
This ensures the chemistry of the bulk fluid is uniform and that samples are representative of the bulk steam generator secondary side water. The WCGS design incorporates pumps for periodic recirculation of the steam generator fluid. Operating experience has shown that a 33 hour3.819444e-4 days <br />0.00917 hours <br />5.456349e-5 weeks <br />1.25565e-5 months <br /> recirculation period will provide adequate bulk mixing. If sample results after 33 hours3.819444e-4 days <br />0.00917 hours <br />5.456349e-5 weeks <br />1.25565e-5 months <br /> of recirculation indicated a failure to meet the layup specifications, corrective action is taken to correct the layup mixture. After any chemical additions necessary to adjust chemistry, the steam generator is recirculated for another 33 hours3.819444e-4 days <br />0.00917 hours <br />5.456349e-5 weeks <br />1.25565e-5 months <br /> prior to sampling.
The intent of the EPRI Secondary Water Chemistry Guidelines for mixing is met after 33 hours3.819444e-4 days <br />0.00917 hours <br />5.456349e-5 weeks <br />1.25565e-5 months <br /> of recirculation.
Three samples per week are not necessary to demonstrate adequate mixing.Enhancements None Wolf Creek Generating Station Page B-26 License Renewal Application Appendix B AGING MANAGEMENT PROGRAMS Operating Experience The Steam Generator Tube Integrity program has been developed to be consistent with NEI 97-06, "Steam Generator Program Guidelines," and it benefits from the industry operating experience available when the initiative was issued as well as the EPRI guidelines it endorses.
Procedures require that the Steam Generator Degradation Assessment for WCGS be updated every operating cycle to incorporate the latest industry and plant specific experience regarding steam generator degradation mechanisms.
Generic Letter 95-05 addresses issues related to Alternate Repair Criteria (ARC). License amendment requests to use alternate repair criteria (B*) were approved for refueling outages 14 and 15, and the subsequent operating cycles following these outages. Tube sleeves are not approved for use at WCGS and have not been used.NRC Information Notice 97-88 addressed the importance of recognizing the potential for degradation in areas that have not previously experienced tube degradation-and the importance of licensees to assess the significance of indications with respect to the qualification of the inspection techniques and the manner in which the indications were detected.
The WCGS Steam Generator Degradation Assessment evaluates industry experience as well as WCGS experience to identify active, relevant and potential tube damage mechanisms.
The inspection sample size, location and method are developed to fully address active mechanisms and provide assurance that relevant and potential mechanisms will be identified if they become active at WCGS. The inspection expansion criteria take into account both increasing the area inspected when degradation is found and changing the technology used to accurately examine ambiguous or unexpected degradation.
WCGS is a four loop Westinghouse plant with four identical Model F steam generators.
As of refueling outage 15 in the Fall of 2006, a total of 204 tubes have been plugged in the plant representing less than 1% of the total tubes. These tubes have been plugged for manufacturing issues at the shop, anti-vibration bar wear, loose part wear, tube support wear (most likely due to a trapped loose part), flow distribution baffle wear (due to pressure pulse cleaning) and preventive measures (manufacturing anomalies discovered in the field).As of the end of the refueling outage 15, no corrosion degradation has been detected in any of the WCGS steam generator tubes. Wear due to anti-vibration bars and loose parts is the only active effect observed in the WCGS steam generators.
Conclusion The continued implementation of the Steam Generator Tube Integrity program provides 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.
Wolf Creek Generating Station Page B-27 License Renewal Application Appendix A Updated Safety Analysis Report Supplement program are consistent with EPRI NP-5069, "Good Bolting Practices, Volume 1 and Volume 2," and EPRI TR-104213, "Bolted Joint Maintenance and Applications Guide." A1.8 STEAM GENERATOR TUBE INTEGRITY The Steam Generator Tube Integrity program includes the preventive measures, condition monitoring inspections, degradation assessment, repair and leakage monitoring activities necessary to manage cracking and loss of material.
The aging management measures employed include non-destructive examination, visual inspection, sludge removal, tube plugging, in-situ pressure testing, maintaining the chemistry environment by removal of impurities and addition of chemicals to control pH and oxygen.NDE inspection scope and frequency, and primary to secondary leak rate monitoring are conducted consistent with the requirements of WCGS Unit 1 Technical Specifications.
Structural integrity limits consistent with Regulatory Guide 1.121, Revision 0, "Bases for Plugging Degraded PWR Steam Generator Tubes," are applied. Steam generator management practices are consistent with NEI 97-06 "Steam Generator Program Guidelines".
Program deviations from NEI 97-06 are prepared and approved in accordance with NEI 97-06 and EPRI steam generator management program guidance.A1.9 OPEN-CYCLE COOLING WATER SYSTEM The Open-Cycle Cooling Water (OCCW) System program manages loss of material and reduction of heat transfer for components exposed to raw water. The program includes chemical treatment and control of biofouling; heat exchanger performance testing; and periodic inspections to ensure that the effects of aging will be managed on the OCCW systems or structures and components serviced by the OCCW systems for the period of extended operation.
The program is consistent with commitments as established in WCGS responses to NRC Generic Letter 89-13 "Service Water System Problems Affecting Safety-Related Components." The Open-Cycle Cooling Water System program provides the general requirements for implementation and maintenance of programs and activities which mitigate aging of OCCW systems and components.
The various aspects of the WCGS program (control, monitoring, maintenance and inspections) are implemented in station procedures.
A1.10 CLOSED-CYCLE COOLING WATER SYSTEM The Closed-Cycle Cooling Water System Program manages loss of material, cracking, and reduction in heat transfer for components in closed cycle cooling water systems. The program includes maintenance of system corrosion inhibitor concentrations and chemistry parameters following the guidance of EPRI TR-107396 to minimize aging, and periodic Wolf Creek Generating Station Page A-5 License Renewal Application