ET 08-0036, Supplement to Response to NRC Requests for Additional Information Related to Generating Station License Renewal Application, Closure of the Metal Fatigue Analysis Open Items
| ML081700279 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 06/09/2008 |
| From: | Garrett T Wolf Creek |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| ET 08-0036 | |
| Download: ML081700279 (11) | |
Text
WoL pF CREEK NUCLEAR OPERATING CORPORATION June 9, 2008 Terry J. Garrett Vice President, Engineering ET 08-0036 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
Reference:
- 2) Letter dated February 1, 2008, from P. T. Kuo, to T. J. Garrett, WCNOC
Subject:
Docket No. 50-482: Supplement to Response to NRC Requests for Additional Information Related to Wolf Creek Generating Station License Renewal Application - Closure of the Metal Fatigue Analysis Open Items Gentlemen:
Reference 1 provided Wolf Creek Nuclear Operating Corporation's (WCNOC) License Renewal Application (LRA) for the Wolf Creek Generating Station (WCGS).,!
Reference 2 issued the Safety Evaluation Report (SER) with Open Items Related to the License Renewal of WCGS. The SER, Section 1.5, established open items (01) related to Metal Fatigue Analyses. These open items are 01 4.3-1 and 01 4.3-3.
Following issuance of the SER with Open Items, Reference 3 requested WCNOC to provide additional information regarding Metal Fatigue Analyses so the NRC could.
complete its review for open items 01 4.3-1 and 01 4.3-3.
P.O. Box 411 / Burlington, KS 66839 / Phone: (620) 364-8831 An Equal Opportunity Employer M/F/HC/VET 0(2-C
ET 08-0036 Page 2 of 3 Reference 4 provided response to the requests for additional information (RAIs) 4.3-1 and 4.3-3. This letter supplements information previously provided in Reference 4. This information also addresses the open items related to Section 4.3.2.7 and 4.3.4 of Reference 2. This supplemental information is necessary to clarify the License Renewal Commitments that are applicable to the scope of the Metal Fatigue Aging Management Program (AMP). WCNOC will comply with Commitments 21, 40 and 41 as part of the Metal Fatigue AMP in accordance with 10 CFR 54.21 (c)(1)(iii).
The Attachment contains an update to the License Renewal Commitment List. Please note that there are no changes to Commitment 21. Commitment 21 is provided for the convenience of the reviewer because Commitment 21, in addition to Commitments 40 and 41 are within the scope of the Metal Fatigue of Reactor Coolant Pressure Boundary Aging Management Program (LRA Section A2.1). Commitments 40 and 41 have been revised to reflect that these Commitments are applicable to the Metal Fatigue AMP and analyses generated from these committed actions will be incorporated as part of the Metal Fatigue AMP prior to the period of extended operation.
The License Renewal Commitment List has also been revised to reflect completion of Commitments 24, 25, and 38. Letter ET 07-0058, dated November 30, 2007, completed commitments 24 and 25. Letters ET 08-0007, dated January 25, 2008, and ET 08-0030, dated May 15, 2008 completed Commitment 38.
The Enclosure provides revised pages for LRA Appendix A, Updated Safety Analysis Report Supplement, for the Metal Fatigue of Reactor Coolant Pressure Boundary AMP (LRA Section A2.1). The revised Section A2.1 reflects incorporation of Commitments 40 and 41.
If you have any questions concerning this matter, please contact me at (620) 364-4084, or Mr. Richard Flannigan at (620) 364-4117.
Sincerely, Terry J. Garrett TJG/rlt
Attachment:
Commitment List
Enclosure:
LRA Appendix A, Updated Safety Analysis Report Supplement cc:
E. E. Collins (NRC), w/a, w/e V. G. Gaddy (NRC), w/a, w/e B. K. Singal (NRC), w/a, wle T. M. Tran (NRC), w/a, w/e Senior Resident Inspector (NRC), w/a, w/e
ET 08-0036 Page 3 of 3 STATE OF KANSAS
)
)
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.
Vice SUBSCRIBED and sworn to before me this ?'
day of
+tA__1
,2008.
GAYLE SHEPHEARDi Notary Public -State of Kansast M Appt. Expires 7!2-3/Zd /
C Notary 0/blic Expiration Date t712f/123
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Attachment to ET 08-0036 Page 1 of 5
- LRA, COMMITMENT Appendix A, COMMITMENT DESCRIPTION SUBJECT Section 21 Metal Fatigue of Reactor Coolant Pressure Boundary (RCMS 2006-218)
A2.1 Prior to the period of extended operation, the Metal Fatigue of Reactor Coolant Pressure Boundary program will be enhanced to include:
- 1)
Cycle Count Action Limit and Corrective Actions An action limit will be established that requires corrective action when the cycle count for any of the critical thermal and pressure transients is projected to reach a high percentage (e.g., 90%) of the design specified number of cycles before the end of the next fuel cycle. If this action limit is
- reached, acceptable corrective actions include:
- 1. Review of fatigue usage calculations.-
To determine whether the transient in question contributes significantly to CUF To identify the components and analyses affected by the transient in question.
To ensure that the analytical bases of the leak-before-break (LBB) fatigue crack propagation analysis and of the high-energy line break (HELB) locations are maintained.
- 2. Evaluation of remaining margins on CUF based on cycle-based or stress-based CUF calculations using the WCGS fatigue management program software.
- 3. Redefinition of the specified number of cycles (e.g., by reducing specified numbers of cycles for other transients and using the margin to increase the allowed number of cycles for the transient that is approaching its specified number of cycles).
- 2) Cumulative Fatigue Usage Action Limit and Corrective Actions An action limit will be established that requires corrective action when calculated CUF (from cycle based or stress based
Attachment to ET 08-0036 Page 2 of 5 monitoring) for any monitored location is projected to reach 1.0 within the next 2 or 3 fuelocycles.
If this action limit is reached, acceptable corrective actions include:
- 1. Determine whether the scope of the monitoring program must be enlarged to include additional affected reactor coolant pressure boundary locations.
This determination will ensure that other locations do not approach design limits without an appropriate action.
- 2. Enhance fatigue monitoring to confirm continued conformance to the code limit.
- 3. Repair the component.
- 4. Replace the component.
- 5. Perform a more rigorous analysis of the component to demonstrate that the design code limit will not be exceeded.
- 6. Modify plant operating practices to reduce the fatigue usage accumulation rate.
- 7. Perform a flaw tolerance evaluation and impose component-specific inspections, under ASME Section Xl Appendices A or C (or their successors), and obtain required approvals by the NRC Corrective action limits for cumulative fatigue usage will be established to assure that sufficient margin is maintained to allow one cycle of the highest fatigue usage per cycle transient to occur without exceeding CUF = 1.0. (This includes consideration of environmental effects for NUREG/CR6260 locations.) This may require that corrective action is taken more than 2 or 3 fuel cycles before CUF is projected to exceed 1.0.
This is because the projections will be based on historical experience, which is not expected to include many of the low probability design transients.
The low probability design transients to be used in the evaluation will include:
Aux. Spray Actuation, Spray Water Diff.>320F Excessive Feedwater Flow Reactor Trip - Cooldown with no SI
Attachment to ET 08-0036 Page 3 of 5 0
0 0
S 0
0 COMS Reactor Trip No Inadvertent
- Cooldown with Turbine Over-speed Reactor Trip - Cooldown with SI Inadvertent RCS Depressurization Accumulator Safety Injection Operating Basis Earthquake
- 3) 10 CFR 50 Appendix B procedural and record requirements.
[Prior to the period of extended operation, changes in available monitoring technology or in the analyses themselves may permit different action limits and action statements, or may re-define the program features and actions required to address fatigue time-limited aging analyses. (TLAAs)]
Reference:
ET 06-0038 Due: March 11, 2025 Revised: ET 07-0031, ET 07-0037 and ET 07-0046 24 ASME III Subsection NG A3.2.2 WCNOC will obtain a
design report Fatigue Analysis of amendment to either quantify the increase Reactor Pressure Vessel in high-cycle fatigue effects, or to confirm Internals that the increase will be negligible.
(RCMS 2006-221)
WCNOC will complete this action before the end of the current licensed operating period.
Reference:
ET 06-0038 Closed: ET 07-0058 25 Assumed Thermal Cycle A3.2.4 WCNOC will complete the reanalysis of the Count for Allowable reactor coolant sample lines and any Secondary Stress Range additional corrective actions or Reduction Factor in B31.1 modifications indicated by them, before the and ASME III Class 2 and end of the current licensed operating 3 Piping (RCMS 2006-222) period.
Reference:
Attachment to ET 08-0036 Page 4 of 5 38 Metal fatigue baseline CUF (RCMS 2007-283)
N/A Backward projection of CUF was used for NUREG/CR-6260 locations (Surge Line Hot Leg,. Nozzle, Charging Nozzles), and for several locations not covered by NUREG
/CR -6260 locations (Pressurizer Lower
- Head, Pressurizer Spray
- Nozzle, Pressurizer Surge
- Nozzle, Pressurizer Surge
- Line, S/G Feedwater Nozzles).
While the ratios used for back-projection do incorporate accumulated fatigue effects from all transients that occurred during
- PERIOD2, it does not account for transients, which occurred more frequently in PERIODI than during PERIOD2.
Therefore, Wolf Creek will prepare an updated baseline that adequately bounds transients experienced prior to the start of CUF monitoring.
The existing baseline CUF for all monitored locations will be increased to bound the potential CUF contribution from the transients that were under-represented in the existing baseline.
Reference:
ET 07-0037, ET 07-0046 Closed: ET 08-0007, ET 08-0030 40 Configuration of Charging A2.1 Validate the presence or absence of Nozzles charging nozzle thermal sleeves.
If WCNOC determines that the sleeves are not present, the analyses will be re-performed and the new analyses will be incorporated into the WCGS fatigue monitoring program.
Reference:
ET 08-0030 Due: March 11, 2023 Revised: ET 08-0036
Attachment to ET 08-0036 Page 5 of 5 41 Metal Fatigue Baseline CUF A2.1 Backward projection of CUF was used in the WCGS fatigue monitoring program for NUREG/CR-6260 Locations (Surge Line Hot Leg Nozzle, and Charging Nozzles).
While the ratios used for back-projection do incorporate accumulated fatigue effects from all transients that occurred during Period 2, it does not account for transients, which occurred more frequently in Period 1 than Period 2.
Therefore, WCNOC will prepare a
fatigue monitoring program updated baseline for the pressurizer hot leg surge nozzle based on the additional insurge/outsurge cycles accumulated in a pre-MOP environment.
Additionally WCNOC will update the fatigue monitoring program baseline for the charging nozzles with consideration for the differential contribution of fatigue for each category of charging event.
Reference:
ET 08-0030 Due: March 11, 2023 Revised ET 08-0036
Enclosure to ET 08-0036 Appendix A Updated Safety Analysis Report Supplement
Appendix A Updated Safety Analysis Report Supplement A2.1 METAL FATIGUE OF REACTOR COOLANT PRESSURE BOUNDARY The WCGS Metal Fatigue of the Reactor Coolant Pressure Boundary program ensures that actual plant experience remains bounded by the assumptions used in the design calculations, or that appropriate corrective measures maintain the design and licensing basis by other acceptable means. The more-recent fatigue monitoring results indicate that none of the design transients should occur more than the currently-specified number of times before the end of a 60-year period of extended operation, and that fatigue usage factors should remain below the code allowable limit of 1.0, including effects of the reactor coolant environment as described by NUREG/CR-6260.
Prior to the period of extended operation, the Metal Fatigue of Reactor Coolant Pressure Boundary program will be enhanced to include:
A cycle count action limit and corrective actions.
An action limit will be established that requires corrective action when the cycle count for any of the critical thermal and pressure transients is projected to reach a stated percentage of the design-specified number of cycles before the end of the next fuel cycle. If this action limit is reached, acceptable corrective actions include:
- 1. Review of fatigue usage calculations To determine whether the transient in question contributes significantly to CUF.
To identify the components and analyses that are affected by the transient in question.
To ensure that the analytical bases of the leak-before-break (LBB) fatigue crack propagation analysis and of the high-energy line break (HELB) locations are maintained.
- 2. Evaluation of remaining margins on CUF based on cycle-based or stress-based CUF calculations using the WCGS fatigue management program software.
- 3. Redefinition of the specified number of cycles (e.g., by reducing specified numbers of cycles for other transients and using the margin to increase the allowed number of cycles for the transient that is approaching its specified number of cycles).
A cumulative fatigue usage action limit and corrective actions. An action limit will be established that requires corrective action when calculated CUF (from cycle-based or stress-based monitoring) for any monitored location is projected to reach 1.0 within the next 2 or 3 fuel cycles.
If this action limit is reached acceptable corrective actions include:
- 1. Determine whether the scope of the monitoring program must be enlarged to include additional affected reactor coolant pressure boundary locations.
This determination will ensure that other locations do not approach design limits without an appropriate action.
- 2. Enhance fatigue monitoring to confirm continued conformance to the code limit.
Wolf Creek Generating Station A-19 License Renewal Application
Appendix A Updated Safety Analysis Report Supplement
- 3. Repair the component.
- 4. Replace the component.
- 5. Perform a more rigorous analysis of the component to demonstrate that the design code limit will not be exceeded.
- 6. Modify plant operating practices to reduce the fatigue usage accumulation rate.
- 7. Perform a flaw tolerance evaluation and impose component-specific inspections, under ASME Section XI Appendices A or C (or their successors), and obtain required approvals by the NRC.
These corrective actions are equally applicable to the WCGS NUREG/CR-6260 locations described in Section A3.2.3, "Effects of the Reactor Coolant System Environment on Fatigue Life of Piping and Components," including consideration of the effects of the reactor coolant environment.
10 CFR 50 Appendix B procedural and record requirements.
Validation of the presence or absence of charging nozzle thermal sleeves.
If sleeves are not present, the fatigue monitoring program analysis for the charging nozzle will be re-performed.
A fatigue monitoring program updated baseline for the pressurizer hot leg surge nozzle based on the additional insurge/outsurge cycles accumulated in a pre-MOP environment. Additionally, the fatigue monitoring program baseline for the charging nozzles will be updated with consideration for the differential contribution of fatigue for each category of charging event.
Wolf Creek Generating Station License Renewal Application A-20