ML13101A338
| ML13101A338 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 03/30/2013 |
| From: | Westman M Wolf Creek |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RA 13-0045 | |
| Download: ML13101A338 (10) | |
Text
WL, F CRcEFEK NUCLEAR OPERATING CORPORATION Michael J. Westman Manager Regulatory Affairs March 30, 2013 RA 13-0045 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
Reference:
- 1)
Letter ET 12-0023, dated October 15, 2012, from J. P.
- 2)
Westinghouse Letter LTR-LIS-13-116, dated March 1, 2013, "Wolf Creek 10 CFR 50.46 Annual Notification and Reporting for 2012"
Subject:
Docket No. 50-482:
10 CFR 50.46 Annual Report of Emergency Core Cooling System (ECCS) Evaluation Model Changes Gentlemen:
This letter provides the annual report for the Emergency Core Cooling System (ECCS)
Evaluation Model changes and errors for the 2012 model year that affect the peak cladding temperature (PCT) for Wolf Creek Generating Station (WCGS). This letter is provided in accordance with the criteria and reporting requirements of 10 CFR 50.46(a)(3)(ii), as clarified in Section 5.1 of WCAP-13451, "Westinghouse Methodology for Implementation of 10 CFR 50.46 Reporting." Regulation 10 CFR 50.46(a)(3)(ii) states, in part, "For each change to or error discovered in an acceptable evaluation model or in the application of such a model that affects the temperature calculation, the applicant or holder of a construction permit, operating license, combined license, or manufacturing license shall report the nature of the change or error and its estimated effect on the limiting ECCS analysis to the Commission at least annually as specified in §50.4 or §52.3 of this chapter, as applicable. If the change or error is significant, the applicant or licensee shall provide this report within 30 days and include with the report a proposed schedule for providing a reanalysis or taking other action as may be needed to show compliance with
§50.46 requirements."
Wolf Creek Nuclear Operating Corporation (WCNOC) has reviewed Reference 2, which addresses 10 CFR 50.46 reporting information pertaining to the ECCS Evaluation Model changes that were implemented by Westinghouse for 2012. The review concludes that with the exception of the "Rebaseline" of the Analysis Of Record (AOR), which reflects the P.O. Box 411 / Burlington, KS 66839 / Phone: (620) 364-8831 A
An Equal Opportunity Employer M/F/HCNET
RA 13-0045 Page 2 of 2 updates to the codes and methods, and the BASH-EM Evaluation of Fuel Pellet Thermal Conductivity Degradation, which were both addressed in a 30 day ECCS model change report (Reference 1), the additional effect of changes to, or errors in, the Evaluation Models on the limiting transient PCT is not significant for 2012. Therefore, changes to the ECCS Evaluation Model are being reported as an annual report.
Attachment I provides an assessment of the specific changes and enhancements to the Westinghouse Evaluation Models for 2012. Except for the exceptions noted above, these model changes and enhancements do not have impacts on the PCT and, generally, will not be presented on the PCT rack-up forms.
Attachment II provides the calculated Large Break Loss of Coolant Accident (LOCA) and Small Break LOCA PCT margin allocations in effect for the 2012 WCGS evaluation models. The PCT values determined in the Large Break and Small Break LOCA analysis of record, combined with all of the PCT allocations, remain below the 10 CFR 50.46(b)(1) regulatory limit of 2200 *F.
Therefore, WCGS is in compliance with 10 CFR 50.46 requirements and no reanalysis or other action is required.
No commitments are identified in this correspondence.
If you have any questions concerning this matter, please contact me at (620) 364-8831, extension. 4009 or Mr. William Muilenburg at (620) 364-8831, extension 4511.
Sincerely, Michael J. Westman MJW/rlt Attachment I -
Assessment of Changes to the Westinghouse Emergency Core Cooling System (ECCS) Evaluation Models for Large and Small Break Loss of Coolant Accidents (LOCA)
Attachment II -
Emergency Core Cooling System (ECCS) Evaluation Model Peak Cladding Temperature (PCT) Margin Utilization cc:
E. E. Collins (NRC), w/a C. F. Lyon (NRC), w/a N. F. O'Keefe (NRC), w/a Senior Resident Inspector (NRC), w/a
Attachment I to RA 13-0045 Page 1 of 4 ASSESSMENT OF CHANGES TO THE WESTINGHOUSE EMERGENCY CORE COOLING SYSTEM (ECCS) EVALUATION MODELS FOR LARGE AND SMALL BREAK LOSS OF COOLANT ACCIDENTS (LOCA)
Non-Discretionary Changes With Peak Cladding Temperature (PCT) Impact "REBASELINE" OF THE ANALYSIS OF RECORD (AOR), WHICH REFLECTS THE EFFECTS OF UPDATES TO THE CODES AND METHODS (BASH)
BASH-EM EVALUATION OF FUEL PELLET THERMAL CONDUCTIVITY DEGRADATION (BASH)
Non-Discretionary Changes With No PCT Impact NOTRUMP-EM EVALUATION OF FUEL PELLET THERMAL CONDUCTIVITY DEGRADATION (NOTRUMP)
Enhancements/Forward-Fit Discretionary Changes General Code Maintenance (BASH)
Editorial Changes None
Attachment I to RA 13-0045 Page 2 of 4 Summary "REBASELINE" OF THE ANALYSIS OF RECORD (AOR). WHICH REFLECTS THE EFFECTS OF UPDATES TO THE CODES AND METHODS (Non-Discretionary Change with PCT Impact)
Background
A method has been developed to extend BASH Evaluation Model transients beyond the point at which downcomer boiling is predicted to occur in BASH by correlating the boiling induced reduction in downcomer driving head to a corresponding reduction in the core inlet flooding rate. This approach, which is referred to as the LOCBART transient extension method (TEM),
is used to ensure adequate termination of the fuel rod cladding temperature and oxidation transients predicted by LOCBART as required to demonstrate compliance with the pertinent acceptance criteria of 10 CFR 50.46. The LOCBART TEM has been reviewed and approved by the Nuclear Regulatory Commission (NRC) as documented in Reference 1.
The rebaseline penalty is a combination of the new code versions, changes in the resulting core inlet flooding rate, and implementation of the LOCBART TEM.
This represents a non-Discretionary Change in accordance with Section 4.1.2 of WCAP-13451 (Reference 2),
"Westinghouse Methodology for Implementation of 10 CFR 50.46 Reporting."
Affected Evaluation Model(s) 1981 Westinghouse Large-Break LOCA Evaluation Model with BASH Estimated Effect The estimated effects for Wolf Creek Generating Station (WCGS) were determined to be 87 OF, based on the bounding results from available sensitivity calculations for other plants. These calculations incorporated the approved LOCBART TEM and met the Limitations and Conditions in Reference 1.
References
- 1. WCAP-10266-P-A, Revision 2, Addendum 3-A, Revision 1, "Incorporation of the LOCBART Transient Extension Method into the 1981 Westinghouse Large Break LOCA Evaluation Model with BASH (BASH-EM)," October 2007.
- 2. WCAP-13451, "Westinghouse Methodology for Implementation of 10 CFR 50.46 Reporting," October 1992.
Attachment I to RA 13-0045 Page 3 of 4 BASH-EM EVALUATION OF FUEL PELLET THERMAL CONDUCTIVITY DEGRADATION (Non-Discretionary Change with PCT Impact)
Background
Evaluations have been completed to estimate the effect of fuel pellet thermal conductivity degradation (TCD) on peak cladding temperature (PCT) for analyses using the 1981 Westinghouse Large-Break Loss-of-Coolant Accident Evaluation Model with BASH (BASH-EM) with the LOCBART Transient Extension Method.
These evaluations utilized fuel rod performance input from a version of the PAD code that accounts for pellet TCD and considered the beneficial effects of assembly power and peaking factor burndown resulting from the depletion of fissionable isotopes.
This change represents a Non-Discretionary Change in accordance with Section 4.1.2 of WCAP-1 3451.
Affected Evaluation Model(s) 1981 Westinghouse Large-Break LOCA Evaluation Model with BASH Estimated Effect The estimated effect was determined on a plant-specific basis. The peaking factor burndown used in the evaluation is provided in Table 1; it is conservative for the current cycle and will be validated as part of the reload design process. Wolf Creek Nuclear Operating Company and its vendor, Westinghouse Electric Company, LLC, utilize processes which ensure that the corresponding LOCA analysis input parameters conservatively bound the as-operated plant values.
Table 1: Peaking Factors Assumed in the Evaluation of TCD Rod Burnup FAH(1)(2)
FQ()
(GWD/MTU) 0 1.65 2.50 30 1.65 2.50 60 1.40 2.00 62 1.40 2.00 (1)
Includes uncertainties.
(2)
Hot assembly average power (PHA) follows the same burndown since it is a function of FAH.
Attachment I to RA 13-0045 Page 4 of 4 NOTRUMP-EM EVALUATION OF FUEL PELLET THERMAL CONDUCTIVITY DEGRADATION (Non-Discretionary Changes with no PCT Impact)
Background
An evaluation has been completed to estimate the effect of fuel pellet thermal TCD on PCT for plants in the United States with analyses using the 1985 Westinghouse Small Break LOCA Evaluation Model with NOTRUMP (NOTRUMP-EM).
This change represents a Non-Discretionary Change in accordance with Section 4.1.2 of WCAP-13451.
Affected Evaluation Model(s) 1985 Westinghouse Small Break LOCA Evaluation Model with NOTRUMP Estimated Effect Based on the phenomena and physics of the SBLOCA transient, in combination with limited sensitivity calculations, it is concluded that TCD has a negligible effect on the limiting cladding temperature transient, leading to an estimated PCT impact of 0 °F.
General Code Maintenance (BASH)
(Enhancements/Forward-Fit Discretionary Changes)
Background
Various changes have been made to enhance the usability of the codes and to help preclude errors in analyses. This includes items such as modifying input variable definitions, units and defaults; improving the input diagnostic checks; enhancing the code output; optimizing active coding; and eliminating inactive coding. These changes represent Discretionary Changes that will be implemented on a forward-fit basis in accordance with Section 4.1.1 of WCAP-1 3451.
Affected Evaluation Model(s) 1981 Westinghouse Large-Break LOCA Evaluation Model with BASH Estimated Effect The nature of these changes leads to an estimated PCT impact of 0 OF.
Attachment II to RA 13-0045 Page 1 of 4 EMERGENCY CORE COOLING SYSTEM (ECCS) EVALUATION MODEL PEAK CLADDING TEMPERATURE (PCT) MARGIN UTILIZATION
Evaluation Model:
Fuel:
Peaking Factor:
SG Tube Plugging:
Power Level:
Limiting transient:
LICENSING BASIS 1981 EM with BASH 17x17 V5H w/IFM, non-IFBA, 275 psig FQ=2.50, FdH=1.65 10%
3565 MWth Cd=0.4, Min. SI, Reduced Tavg Clad Temp (0F) 1916 OF Ref.
Notes 1
(a)
Analysis of Record PCT MARGIN ALLOCATIONS (APCT)
A. PRIOR PERMANENT ECCS MODEL ASSESSMENTS
- 1. Structural Metal Heat Modeling
- 2. LUCIFER Error Corrections
- 3. Skewed Power Shape Penalty
- 4. Hot Leg Nozzle Gap Benefit
- 5. SATAN-LOCTA Fluid Error
- 6. LOCBART Spacer Grid Single-Phase Heat Transfer Error
- 7. LOCBART Vapor Film Flow Regime Heat Transfer Error
- 8. LOCBART Cladding Emissivity Errors
- 9. LOCBART Radiation to Liquid Logic Error Correction
- 10. LOCBART Pellet Volumetric Heat Generation Rate B. PLANNED PLANT CHANGE EVALUATIONS
- 1. Loose Parts Evaluation
- 2. Effects of Containment Purging
- 3. Cycle 10 Fuel Assembly Design Changes
- 4. Fuel Rod Crud C. 2012 PERMANENT ECCS MODEL ASSESSMENTS
- 2. PWROG TCD Evaluation - Effect of TCD and Assembly Power/Peaking D. TEMPORARY ECCS MODEL ISSUES E. OTHER
- 1. Cold Leg Streaming Temperature Gradient
- 2. Rebaseline of AOR (12/96)
- 3. LOCBART Zirc-Water Oxidation Error
-25
-6 152
-136 15 15 9
6 17 45 20 0
95 0
8 10 11 11 2
9 12 13 14 15 3
4 5
6 16 16 87 0
(e)
(e) 0 0
-63 28 8
9 7
(b)
(c)
(d)
LICENSING BASIS PCT + MARGIN ALLOCATIONS PCT = 2175 OF CUMULATIVE ABSOLUTE MAGNITUDE OF PCT CHANGES Ej'APCTI = 0 °F SINCE LAST 30-DAY REPORT (LETTER ET 12-0023)
Attachment II to RA 13-0045 Page 2 of 4
References:
- 1.
Westinghouse Topical Report WCAP-13456, "Wolf Creek Generating Station NSSS Rerating Licensing Report," October 1992.
- 2.
Westinghouse to WCNOC letter SAP-97-102, "Wolf Creek Nuclear Operating Corporation, Wolf Creek Generating Station, 10 CFR 50.46 Annual Notification and Reporting," February 17, 1997.
- 3.
Westinghouse to WCNOC letter SAP-90-148, "Wolf Creek Nuclear Operating Corporation, RCS Loose Parts Evaluation," April 18, 1998.
- 4.
Westinghouse to WCNOC letter SAP-94-102, "Containment Mini purge Isolation Valve Stroke Time Increase," January 12, 1994.
- 5.
Westinghouse to WCNOC letter 97SAP-G-0009, "Wolf Creek Nuclear Operating Corporation, Wolf Creek Generating Station, Safety Assessment for the Wolf Creek Generating Station with ZIRLO TM Fuel Assemblies," February 7, 1997.
- 6.
Westinghouse to WCNOC letter 97SAP-G-0075, "Wolf Creek Nuclear Operating Corporation, Wolf Creek Generating Station, Wolf Creek Crud Deposition/Axial Offset Anomaly Safety Evaluation," September 29, 1997.
- 7.
Westinghouse to WCNOC letter OOSAP-G-0006, "Wolf Creek Nuclear Operating Corporation, Wolf Creek Generating Station, Wolf Creek Cycle 12 LOCA Current Limits,"
February 10, 2000.
- 8.
Westinghouse to WCNOC letter SAP-93-701, "Wolf Creek Nuclear Operating Corporation, Wolf Creek Generating Station, 10 CFR 50.46 Notification and Reporting Information," January 25, 1993.
- 9.
Westinghouse to WCNOC letter SAP-99-148, "Wolf Creek Nuclear Operating Corporation, Wolf Creek Generating Station, 10 CFR 50.46 BART/BASH Evaluation Model Mid-Year Notification and Reporting for 1999," September 22, 1999.
- 10. Westinghouse to WCNOC letter SAP-94-703, "Wolf Creek Nuclear Operating Corporation, Wolf Creek Generating Station, 10 CFR 50.46 Notification and Reporting,"
February 8, 1994.
- 11. Westinghouse to WCNOC letter SAP-95-716, "Wolf Creek Nuclear Operating Corporation, Wolf Creek Generating Station, LOCA Axial Power Shape Sensitivity Model," August 14, 1995.
- 12. Westinghouse to WCNOC letter SAP-00-1 18, "Wolf Creek Nuclear Operating Corporation, Wolf Creek Generating
- Station, 10 CFR 50.46 Appendix K
(BART/BASH/NOTRUMP) Evaluation Model, Mid-Year Notification and Reporting for 2000," June 30, 2000.
- 13. Westinghouse to WCNOC letter SAP-00-150, "Wolf Creek Nuclear Operating Corporation, Wolf Creek Generating Station, 10 CFR 50.46 BART/BASH Evaluation Model Mid-Year Notification and Reporting for 2000," December 2000.
- 14. Westinghouse to WCNOC letter SAP-02-32, "10 CFR 50.46 BART/BASH Evaluation Model Mid-Year Notification and Reporting for 2002," June 2002.
- 15. Westinghouse to WCNOC letter LTR-LIS-07-312, "10 CFR 50.46 Reporting Text for LOCBART Version 37.0 Issues and Revised PCT Rackup sheets for Wolf Creek," May 14, 2007.
- 16. Westinghouse to WCNOC letter LTR LIS-12-515, "Wolf Creek, 10 CFR 50.46 Notification and Reporting for Fuel Pellet Thermal Conductivity Degradation and Peaking Factor Burndown," September 20, 2012.
Attachment II to RA 13-0045 Page 3 of 4 Notes:
(a) An evaluation was performed to support removal of the transition core penalty for Cycle 12 (Ref. 7).
(b)
A PCT benefit of < 2.5 OF was assessed, however, a benefit of 0 OF will be tracked for reporting purposes.
(c) This previously unclaimed benefit was realized through prior rebaseline of the limiting case.
(d)
This assessment is a function of analysis PCT plus certain margin allocations and as such may increase/decrease with margin allocation changes.
(e) This effect was estimated based on the bounding value from the available plant-specific calculations.
Attachment II to RA 13-0045 Page 4 of 4
Evaluation Model:
1985 EM with NOT Fuel:
17x17 RFA-2 w/IFF Peaking Factor:
FQ=2.50, FdH=I.6 SG Tube Plugging:
10%
Power Level:
3565 MWth Limiting transient:
4-inch Break LICENSING BASIS Clai Analysis of Record PCT MARGIN ALLOCATIONS (APCT)
A.
PRIOR PERMANENT ECCS MODEL ASSESSMENTS
- 1. None B.
PLANNED PLANT CHANGE EVALUATIONS
- 1. Loose Part Evaluation C.
2012 PERMANENT ECCS MODEL ASSESSMENTS
- 1. None D.
TEMPORARY ECCS MODEL ISSUES
- 1. None E.
OTHER
- RUMP M
5 IdTemnp (F)
Ref.
Notes 936 OF 1
0 45 2
(a) 0 0
0 PCT = 981 OF IIAPCTI =0°F
References:
- 1. WCAP-16717-P, Rev. 0, "Wolf Creek Generating Station (SAP), MSIV/MFIV Replacement Project, Small Break Loss of Coolant Accident Analysis Engineering Report," January 2007.
- 2. SAP-90-148/NS-OPLS-OPL-I-90-239, "Wolf Creek Nuclear Operating Corporation, RCS Loose Part Evaluation," April 1990.
Notes:
(a) This penalty will be carried to track the loose part which has not been recovered.