ML15091A382
| ML15091A382 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 03/20/2015 |
| From: | Koenig S R Wolf Creek |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RA 15-0025 | |
| Download: ML15091A382 (10) | |
Text
WOLF CREEKNUCLEAR OPERATING CORPORATIONSteven R. KoenigManager Regulatory Affairs March 20, 2015RA 15-0025U. S. Nuclear Regulatory CommissionATTN: Document Control DeskWashington, DC 20555
Reference:
Westinghouse Letter LTR-LIS-15-36, dated February 19, 2015,"Wolf Creek 10 CFR 50.46 Annual Notification and Reporting for2014"
Subject:
Docket No. 50-482: 10 CFR 50.46 Annual Report of EmergencyCore Cooling System (ECCS) Evaluation Model ChangesGentlemen:This letter provides the annual report for the Emergency Core Cooling System (ECCS)Evaluation Model changes and errors for the 2014 model year that affect the peakcladding temperature (PCT) for Wolf Creek Generating Station (WCGS). This letter isprovided in accordance with the criteria and reporting requirements of 10 CFR50.46(a)(3)(ii), as clarified in Section 5.1 of WCAP-13451, "Westinghouse Methodologyfor 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 inthe application of such a model that affects the temperature calculation, the applicant orholder of a construction permit, operating license, combined license, or manufacturinglicense shall report the nature of the change or error and its estimated effect on thelimiting ECCS analysis to the Commission at least annually as specified in §50.4 or §52.3of this chapter, as applicable. If the change or error is significant, the applicant or licenseeshall provide this report within 30 days and include with the report a proposed schedule forproviding 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 the notification andreporting requirements of 10 CFR 50.46 pertaining to the ECCS Evaluation Modelchanges that were implemented by Westinghouse for 2014 as described in the aboveReference. The review concludes that the effect of changes to, or errors in, theEvaluation Models on the limiting transient PCT is not significant for 2014. Therefore,changes to the ECCS Evaluation Models are being reported as an annual report.P.O. Box 411 / Burlington, KS 66839 / Phone: (620) 364-8831 0 -,9An Equal Opportunity Employer M/F/HCNET RA 15-0025Page 2 of 2Attachment I provides an assessment of the specific changes and enhancements to theWestinghouse Evaluation Models for 2014. With the exception of a Wolf CreekContainment Cooling Capacity error which resulted in an estimated effect of 6° Fahrenheit(F) for the BASH evaluation model, the other model changes and enhancements do nothave impacts on the PCT and, generally, will not be presented on the PCT rack-up forms.Attachment II provides PCT rack-up forms for the calculated Large Break Loss of CoolantAccident (LOCA) and Small Break LOCA PCT margin allocations in effect for the 2014WCGS evaluation models. The PCT values determined in the Large Break and SmallBreak LOCA analysis of record, combined with all of the PCT allocations, remain belowthe 10 CFR 50.46(b)(1) regulatory limit of 2200°F. Therefore, WCGS is in compliancewith 10 CFR 50.46 requirements and no reanalysis or other action is required.This letter contains no commitments. If you have any questions concerning this matter,please contact me at (620) 364-4041 or Bill Muilenburg at 620-364-4186.SRK/rltAttachment I -Attachment II -Assessment of Changes to the Westinghouse Emergency Core CoolingSystem (ECCS) Evaluation Models for Large and Small Break Loss ofCoolant Accidents (LOCA)Emergency Core Cooling System (ECCS) Evaluation Model PeakCladding Temperature (PCT) Margin Utilization Rack-up Formscc: M. L. Dapas (NRC), w/aC. F. Lyon (NRC), w/aN. F. O'Keefe (NRC), w/aSenior Resident Inspector (NRC), w/a Attachment I to RA 15-0025Page 1 of 4ASSESSMENT OF CHANGES TO THE WESTINGHOUSE EMERGENCYCORE COOLING SYSTEM (ECCS) EVALUATION MODELS FOR LARGEAND SMALL BREAK LOSS OF COOLANT ACCIDENTS (LOCA)Non-Discretionary Changes With Peak Cladding Temperature (PCT) ImpactWOLF CREEK CONTAINMENT COOLING CAPACITY (BASH)Non-Discretionary Changes With No PCT ImpactFUEL ROD GAP CONDUCTANCE ERROR (NOTRUMP)RADIATION HEAT TRANSFER MODEL ERROR (NOTRUMP)SBLOCTA PRE-DEPARTURE FROM NUCLEATE BOILING (DNB) CLADDING SURFACEHEAT TRANSFER COEFFICIENT CALCULATION (NOTRUMP)Enhancements/Forward-Fit Discretionary ChangesGENERAL CODE MAINTENANCE (NOTRUMP)Editorial ChangesNone Attachment I to RA 15-0025Page 2 of 4SummaryWOLF CREEK CONTAINMENT COOLING CAPACITY(Non-Discretionary Change with PCT Impact)BackgroundWolf Creek Nuclear Operating Corporation (WCNOC) identified an error in the containmentfan cooler capacity transmitted for use in the large break loss-of-coolant accident (LBLOCA)Appendix K BASH analyses. This issue has been evaluated to estimate the impact onexisting peak cladding temperature results. The resolution of this issue represents a Non-Discretionary Change in accordance with Section 4.1.2 of WCAP-1 3451.Affected Evaluation Models1981 Westinghouse Large Break LOCA Evaluation Model with BASHEstimated EffectThe estimated effect was determined for the LBLOCA evaluation model w it h B A S Hbased on the change in calculated containment pressure resulting from the correctcontainment cooling capacity. The change in calculated containment pressure leads to anestimated PCT effect of 60 Fahrenheit (F) for the BASH evaluation model analysis.FUEL ROD GAP CONDUCTANCE ERROR(Non-Discretionary Change with no PCT Impact)BackgroundAn error was identified in the fuel rod gap conductance model in the NOTRUMP computer code(reactor coolant system response model). The error is associated with the use of an incorrecttemperature in the calculation of the cladding emissivity term. This error corresponds to aNon-Discretionary Change as described in Section 4.1.2 of WCAP-1 3451.Affected Evaluation Model(s)1985 Westinghouse Small Break LOCA Evaluation Model with NOTRUMPEstimated EffectThe estimated effect was determined based on a combination of engineering judgment of thephenomena and physics of a small break LOCA and sensitivity calculations performed with theadvanced plant version of NOTRUMP. It was concluded that this error has a negligible effecton small break LOCA analysis results, leading to an estimated PCT impact of 0°F.
Attachment I to RA 15-0025Page 3 of 4RADIATION HEAT TRANSFER MODEL ERROR(Non-Discretionary Change with no PCT Impact)BackgroundTwo errors were discovered in the calculation of the radiation heat transfer coefficient withinthe fuel rod model of the NOTRUMP computer code (reactor coolant system response model).First, existing logic did not preclude non-physical negative or large (negative or positive)radiation heat transfer coefficients from being calculated. These erroneous calculationsoccurred when the vapor temperature exceeded the cladding surface temperature or when thepredicted temperature difference was less than I F. Second, a temperature term incorrectlyused degrees Fahrenheit instead of Rankine. These errors represent a closely related groupof Non-Discretionary problems in accordance with Section 4.1.2 of WCAP-1 3451.Affected Evaluation Model(s)1985 Westinghouse Small Break LOCA Evaluation Model with NOTRUMPEstimated EffectThe estimated effect was determined based on a combination of engineering judgment of thephenomena and physics of a small break LOCA and sensitivity calculations performed withthe advanced plant version of NOTRUMP. It was concluded that this error has a negligibleeffect on small break LOCA analysis results, leading to an estimated Peak CladdingTemperature (PCT) impact of 0°F.SBLOCTA PRE-DNB CLADDING SURFACE HEAT TRANSFER COEFFICIENTCALCULATION(Non-Discretionary Change with no PCT Impact)BackgroundTwo errors were discovered in the pre-departure from nucleate boiling (pre-DNB) claddingsurface heat transfer coefficient calculation in the SBLOCTA code (cladding heat-upcalculations). The first error is a result of inconsistent time units (hours vs. seconds) in theparameters used for the calculation of the Reynolds and Prandtl numbers, and the second errorrelates to an incorrect diameter used to develop the area term in the cladding surface heat fluxcalculation. Both of these issues impact the calculation of the pre-DNB convective heattransfer coefficient, representing a closely related group of Non-Discretionary Changes to theEvaluation Model as described in Section 4.1.2 of WCAP-1 3451.Affected Evaluation Model(s)1985 Westinghouse Small Break LOCA Evaluation Model with NOTRUMPEstimated EffectThese errors have been corrected in the SBLOCTA code. Because this condition occurredprior to DNB, it was judged that these errors had no direct impact on the cladding heat-uprelated to the core uncovery period. A series of validation tests were performed and confirmedthat these errors have a negligible effect on SBLOCA analysis results, leading to an estimatedPCT impact of 0°F.
Attachment I to RA 15-0025Page 4 of 4GENERAL CODE MAINTENANCE(Enhancements/Forward-Fit Discretionary Changes)BackgroundVarious changes have been made to enhance the usability of codes and to streamlinefuture analyses. Examples of these changes include modifying input variable definitions, unitsand defaults; improving the input diagnostic checks; enhancing the code output; optimizingactive coding; and eliminating inactive coding. These changes represent DiscretionaryChanges that will be implemented on a forward-fit basis in accordance with Section 4.1.1 ofWCAP-13451.Affected Evaluation Models1985 Westinghouse Small Break LOCA Evaluation Model with NOTRUMPEstimated EffectThe nature of these changes leads to an estimated PCT impact of 00F.
Attachment II to RA 15-0025Page 1 of 4EMERGENCY CORE COOLING SYSTEM (ECCS) EVALUATION MODEL PEAKCLADDING TEMPERATURE (PCT) MARGIN UTILIZATION RACK-UP FORMS*** LARGE BREAK LOCA PCT MARGIN UTILIZATION ***Evaluation Model:Fuel:Peaking Factor:SG Tube Plugging:Power Level:Limiting transient:LICENSING BASIS1981 EM with BASH17x17 V5H w/IFM, non-IFBA, 275 psigFQ=2.50, FdH=1.6510%3565 MWthCd=0.4, Min. SI, Reduced TavgClad Temp (OF)1916 OFRef. Notes1 (a)Analysis of Record (AOR) PCTMARGIN ALLOCATIONS (APCT)A. PRIOR PERMANENT ECCS MODEL ASSESSMENTS1. Structural Metal Heat Modeling2. LUCIFER Error Corrections3. Skewed Power Shape Penalty4. Hot Leg Nozzle Gap Benefit5. SATAN-LOCTA Fluid Error6. LOCBART Spacer Grid Single-Phase Heat Transfer Error7. LOCBART Vapor Film Flow Regime Heat Transfer Error8. LOCBART Cladding Emissivity Errors9. LOCBART Radiation to Liquid Logic Error Correction10. LOCBART Pellet Volumetric Heat Generation Rate11. PWROG TCD EVALUATION -Rebaseline of AOR12. PWROG TCD Evaluation -Effect of TCD and AssemblyPower/Peaking Factor BurndownB. PLANNED PLANT CHANGE EVALUATIONS1. Loose Parts Evaluation2. Effects of Containment Purging3. Cycle 10 Fuel Assembly Design Changes4. Fuel Rod CrudC. 2014 PERMANENT ECCS MODEL ASSESSMENTS1. Containment Fan Cooler CapacityD. TEMPORARY ECCS MODEL ISSUESE. OTHER1. Cold Leg Streaming Temperature Gradient2. Rebaseline of AOR (12/96)3. LOCBART Zirc-Water Oxidation Error-25-6152-136151596174587020095068101111291213.14151616(e)(e)34561700-6328897(b)(c)(d)LICENSING BASIS PCT + MARGIN ALLOCATIONS PCT = 2181 °FCUMULATIVE ABSOLUTE MAGNITUDE OF PCT CHANGES El APCTI =6 °FSINCE LAST 30-DAY REPORT (LETTER ET 12-0023,ADAMS Accession No. ML12298A504)
Attachment II to RA 15-0025Page 2 of 4
References:
- 1. Westinghouse Topical Report WCAP-13456, "Wolf Creek Generating Station NSSSRerating Licensing Report," October 1992.2. Westinghouse to WCNOC letter SAP-97-102, "Wolf Creek Nuclear OperatingCorporation, Wolf Creek Generating Station, 10 CFR 50.46 Annual Notification andReporting," February 17, 1997.3. Westinghouse to WCNOC letter SAP-90-148, "Wolf Creek Nuclear OperatingCorporation, RCS Loose Parts Evaluation," April 18, 1998.4. Westinghouse to WCNOC letter SAP-94-102, "Containment Mini purge Isolation ValveStroke Time Increase," January 12, 1994.5. Westinghouse to WCNOC letter 97SAP-G-0009, "Wolf Creek Nuclear OperatingCorporation, Wolf Creek Generating Station, Safety Assessment for the Wolf CreekGenerating Station with ZIRLOTM Fuel Assemblies," February 7, 1997.6. Westinghouse to WCNOC letter 97SAP-G-0075, "Wolf Creek Nuclear OperatingCorporation, Wolf Creek Generating Station, Wolf Creek Crud Deposition/Axial OffsetAnomaly Safety Evaluation," September 29, 1997.7. Westinghouse to WCNOC letter OOSAP-G-0006, "Wolf Creek Nuclear OperatingCorporation, 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 OperatingCorporation, Wolf Creek Generating Station, 10 CFR 50.46 Notification and ReportingInformation," January 25, 1993.9. Westinghouse to WCNOC letter SAP-99-148, "Wolf Creek Nuclear OperatingCorporation, Wolf Creek Generating Station, 10 CFR 50.46 BART/BASH EvaluationModel Mid-Year Notification and Reporting for 1999," September 22, 1999.10. Westinghouse to WCNOC letter SAP-94-703, "Wolf Creek Nuclear OperatingCorporation, 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 OperatingCorporation, Wolf Creek Generating Station, LOCA Axial Power Shape SensitivityModel," August 14, 1995.12. Westinghouse to WCNOC letter SAP-00-1 18, "Wolf Creek Nuclear OperatingCorporation, Wolf Creek Generating Station, 10 CFR 50.46 Appendix K(BART/BASH/NOTRUMP) Evaluation Model, Mid-Year Notification and Reporting for2000," June 30, 2000.13. Westinghouse to WCNOC letter SAP-00-150, "Wolf Creek Nuclear OperatingCorporation, Wolf Creek Generating Station, 10 CFR 50.46 BART/BASH EvaluationModel Mid-Year Notification and Reporting for 2000," December 2000.14. Westinghouse to WCNOC letter SAP-02-32, "10 CFR 50.46 BART/BASH EvaluationModel Mid-Year Notification and Reporting for 2002," June 2002.15. Westinghouse to WCNOC letter LTR-LIS-07-312, "10 CFR 50.46 Reporting Text forLOCBART Version 37.0 Issues and Revised PCT Rackup sheets for Wolf Creek," May14, 2007.16. Westinghouse to WCNOC letter LTR-LIS-12-515, "Wolf Creek, 10 CFR 50.46Notification and Reporting for Fuel Pellet Thermal Conductivity Degradation and PeakingFactor Burndown," September 20, 2012.17. Westinghouse to WCNOC letter LTR-LIS-14-400, "10 CFR 50.46 Report for the WolfCreek Large Break LOCA Evaluation of the Change in Containment Cooling Capacity,"August 28, 2014.
Attachment II to RA 15-0025Page 3 of 4Notes:(a) An evaluation was performed to support removal of the transition core penalty for Cycle12 (Ref. 7).(b) A PCT benefit of < 2.5 OF was assessed, however, a benefit of 0 OF will be tracked forreporting purposes.(c) This previously unclaimed benefit was realized through prior rebaseline of the limitingcase.(d) This assessment is a function of analysis PCT plus certain margin allocations and assuch may increase/decrease with margin allocation changes.(e) This effect was estimated based on the bounding value from the available plant-specificcalculations.
Attachment II to RA 15-0025Page 4 of 4*** SMALL BREAK LOCA PCT MARGIN UTILIZATION ***Evaluation Model: 1985 EM with NOIFuel: 17x17 RFA-2 w/IFIPeaking Factor: FQ=2.50, FdH=1.6SG Tube Plugging: 10%Power Level: 3565 MWthLimiting transient: 4-inch BreakLICENSING BASISClaiAnalysis of Record PCTMARGIN ALLOCATIONS (APCT)A. PRIOR PERMANENT ECCS MODEL ASSESSMENTS1. NoneB. PLANNED PLANT CHANGE EVALUATIONS1. Loose Part EvaluationC. 2014 PERMANENT ECCS MODEL ASSESSMENTS1. NoneD. TEMPORARY ECCS MODEL ISSUES1. NoneE. OTHER1. NoneLICENSING BASIS PCT + MARGIN ALLOCATIONSCUMULATIVE ABSOLUTE MAGNITUDE OF PCT CHANGESRUMP]5d Temnp (*F) Ref. Notes936 OF 10452 (a)000PCT = 981 OF1IAPCTI =0-F
References:
- 1. WCAP-16717-P, Rev. 0, "Wolf Creek Generating Station (SAP), MSIV/MFIV ReplacementProject, Small Break Loss of Coolant Accident Analysis Engineering Report," January2007.2. SAP-90-148/NS-OPLS-OPL-1-90-239, "Wolf Creek Nuclear Operating Corporation, RCSLoose Part Evaluation," April 1990.Notes:(a) This penalty will be carried to track the loose part which has not been recovered.