ML13239A479

Nuclear Safety Advisory Letter NSL-11-5, Westinghouse LOCA Mass & Energy Release Calculation Issues.

ML13239A479
Person / Time
Site:	Indian Point
Issue date:	07/25/2011
From:	Andrachek J D, Jakub R M, Ofstun R P Westinghouse
To:	Office of Nuclear Reactor Regulation
Shared Package
ML13239A476	List: ML13239A479 NL-13-058, Response to Request for Additional Information Re Containment Integrity Analysis
References
NL-13-058, TAC MF0590, TAC MF0591 NSL-11-5
Download: ML13239A479 (14)

Text

ATTACHMENT 3 TO NL-13-058NUCLEAR SAFETY ADVISORY LETTER NSAL-11-54 Nuclear Safety *sWestinghouseAdvisory LetterThis is a notification of a recently identified potential safety issue pertaining to basic components supplied by Westinghouse.This information is being provided so that you can conduct a review of this issue to determine if any action is required.1000 Westinghouse Drive, Cranberry Township. PA 16066C, 2011 Westinghouse Electric Company LLCAll Rights ReservedSubject: Westinghouse LOCA Mass and Energy Release Number: NSAL-11-5Calculation IssuesBasic Component: Containment Mass and Energy Release Analysis Date: 07/25/2011Substantial Safety Hazard or Failure to Comply Pursuant to 10 CFR 21.21(a) Yes 0 No F0 N/A D-Transfer of Information Pursuant to 10 CFR 21.21(b) Yes D]Advisory Information Pursuant to 10 CFR 21.21(d)(2) Yes EDSUMMARYThis Nuclear Safety Advisory Letter (NSAL) is applicable to loss-of-coolant accident (LOCA) mass andenergy (M&E) release calculations performed for Westinghouse-designed pressurized water reactors(PWRs) utilizing the methodology documented in WCAP-10325-P-A and WCAP-8264-P-A, Revision 1(References I and 2, respectively). Combustion Engineering NSSS designs and BWR designs are notaffected by these issues.The six issues listed below can potentially impact the plant specific LOCA M&E release calculationresults which are used as input to the containment integrity response analyses. The six issues, whichinclude generic errors that can impact the plant specific analyses differently, are:1. The reactor vessel modeling did not include all the appropriate vessel metal mass available frotnthe component drawings.2. The reactor vessel modeling did not include all the appropriate vessel metal mass in the reactorvessel barrel/baffle region.3. The reactor coolant pump (RCP) homologous curve input incorrectly included an absolute zeropoint coordinate.4. The RCP homologous curve input incorrectly contained a sign error in a coordinate value.5. The LOCA M&E release analysis initializes at a non-conservative (low) steam generator (SG)secondary pressure condition.6. An error found in the EPITOME computer code (WCAP-10325-P-A methodology only) that isused to determine the M&E release rate during the long-term (i.e., post-reflood) SGdepressurization phase of the LOCA transient.Additional information, if required, may be obtained from Matt Cerrone (412) 374-6707Authors:J. D. AndrachekPlant LicensingR. P. OfstunContainment and Radiological AnalysisR. M. JakubContainment and Radiological AnalysisApproved:J. A. Gresham, ManagerRegulatory Compliance NSAL-11-5Page 2 of 13These six issues can result in an increase in the LOCA M&E release to the contairunent. The increase inthe LOCA M&E release associated with each of these issues affects the plant specific containment LOCAblowdown and post-blowdown transient conditions differently. The increase in the LOCA M&E releasehas the potential to affect the following analyses. The impact on these analyses is also discussed.Long-term Containment Peak PressureEstimated containment pressure penalties for each issue are listed in Table 1. The WCAP-10325-P-A andWCAP-8264-P-A, Revision I methodology contains modeling and initial condition assumptionconservatisms that result in a calculated peak pressure that is 6 psi higher than the peak pressure thatwould be determined from a more realistic analysis. This 6 psi would offset the resulting increase in thecontainment peak pressure (Pa) associated with these issues. Therefore, if a more realistic analysis wereperformed, Pa would not increase above the current value and there would be no impact on the I OCFR50,Appendix J, Type A, B, and C tests.Containment Peak TemperatureAs discussed above, if a more realistic analysis were performed, Pa would not increase above the currentvalue due to these issues and the containment peak temperature would not be impacted. Temperature is afunction of pressure; therefore, if pressure does not increase., temperature will not increase.Containment Equipment QualificationAs discussed above, if a more realistic analysis were performed, Pa would not increase above the currentvalue due to these issues and the containment peak temperature would not be impacted. Temperature is afunction of pressure; therefore, if pressure does not increase, temperature will not increase. If the peakpressure and temperature are not impacted, then there Would be no impact on long-term pressure andtemperature.Containment Sump TemperatureIf a more realistic analysis were performed, the overall initial internal energy of the RCS would be lowerand the active containment heat removal systems would be more efficient. This would result in a lowerM&E release to the containment atmosphere and the sump and an increase in the energy removed fromthe containment. The result would be a lower sump temperature transient.Energy Loads to the Ultimate Heat SinkIf a more realistic analysis were performed, the energy transferred to tile ultimate heat sink would bereduced as compared to the design basis analysis; therefore, the ultimate heat sink analyses would not beimpacted.This issue does not affect the LOCA ECCS analysis and does not fall within the reporting requirements of10 CFR 50.46.ISSUE DESCRIPTIONThe LOCA M&E releases are conservatively generated and used as input to the containment integrityresponse analyses. Westinghouse has identified six issues that can potentially result in a non-conservativeplant specific LOCA M&E release calculation:1. Reactor Vessel Metal Mass -The reactor vessel model did not include all the appropriate vesselmetal mass available from the component drawings. The discrepancy results in an inaccuratevessel metal mass that affects the amount of reactor vessel stored energy initially available in theM&E model. Containment pressure sensitivity studies were performed to evaluate the impact of NSAL-I 1-5Paged of 13using a higher metal mass for the lower support plate in the vessel. The sensitivity studiesshowed no significant increase in the calculated peak containment pressure in either theblowdown or post-reflood phase of the LOCA event.2. Missing Barrel/Baffle Region Metal Mass -The reactor vessel model did not include theappropriate amount of vessel metal mass in the reactor vessel barrel/baffle downcomer region.Differences were identified in tile calculated metal mass and surface area input values betweenupflow and downflow barrel/baffle configurations, with more significant differences noted inplants that were converted to an upflow barrel/baffle configuration. Increases in the barrel/bafflemetal mass impact the initial energy stored within the reactor vessel. Sensitivity studies showedno significant increase in the calculated peak containment pressure during tile blowdown phase.However, the calculated peak containment pressure was found to increase during the post-refloodphase. For the downflow barrel/baffle design, the calculated post-reflood phase peak containmentpressure increase was small, approximately 0.05 psi; but for the upflow barrel/baffle design, theincrease was approximately 0.35 psi.3. RCP Homologous Curve Zero Point -The RCP homologous curve inputs in certain plant specificanalyses were found to incorrectly include an absolute zero coordinate data set when positivenon-zero values were required. This error has an impact on the reflood portion of the long-termLOCA M&E release calculations. Sensitivity studies showed no significant increase in thecalculated peak containment pressure during the blowdown phase. The calculated post-refloodphase peak containment pressure was found to increase by approximately 0.4 psi.4. RCP Sign Error -A separate homologous curve input error was identified while performing tileextent of condition for Item 3 above. A positive value for at/v was modeled in the input array inthe reflood code for some plant specific LOCA M&E release analyses when it should have beennegative. This error has an impact on the reflood portion of the long-term LOCA M&E releasecalculations. Sensitivity studies showed no significant increase in tile calculated peakcontainment pressure in either the blowdown or post-blowdown phase of the LOCA event.5. SG Pressure Error -The LOCA M&E release analysis was initialized at a non-conservative (low)SG secondary pressure value. This input value determines the initial SG secondary sidetemperature and pressure used in the LOCA M&E release calculations. Tile pressure at the exitof tile SG outlet nozzle was incorrectly used as the SG secondary side pressure. as opposed to thecorrect, higher tube bundle pressure. The initial SG energy is underestimated; therefore, thecorrection results in an increase in the calculated LOCA M&E release. Sensitivity studiesshowed an approximate 0. 1 psi increase in the calculated blowdown peak containment pressureand an approximate 0.4 psi increase in the calculated post-blowdown peak containment pressure.6. An error was found in the EPITOME computer code which determines the M&E release (post-reflood) during the long-term SG depressurization phase of the LOCA transient. The error resultsin an underestimated energy release in the long-term, post-reflood phase of the transient. Theimpact of this single issue is expected to be less than 3.0 psi for most Westinghouse PWRs withdry and sub-atmospheric designs. However, since engineering safety features can varyconsiderably from plant to plant, the impact could be as much as 4.0 psi for some plants.TECHNICAL EVALUATIONShort-term Sub-compartment Differential Pressure AnalysesThe LOCA M&E release during a short-term sub-compartment differential pressure analysis lasts onlyI second to 3 seconds. The short-term LOCA break flow rate is dominated by the initial RCS pressure NSAL-I I-5Page 4 of 13and RCS primary side fluid temperatures that are defined in the transient initial conditions. Analysisassumptions such as stored RCS metal energy and SG secondary pressure do not affect the calculation ofthe short-term LOCA M&E releases because of the duration of the transient. Therefore, none of the sixissues previously described will have any impact the short-term LOCA M&E release input used in theshort-term sub-compartment differential pressure analyses.Long-term Containment Peak Pressure AnalysesThe long-term containment peak pressure analyses are conservatively performed to confirm that the peakpressure is less than the containment design pressure value. The magnitude of the calculated peakcontainment pressure for a LOCA event depends upon the LOCA M&E release rates, the volume of thecontainment, and the energy absorption rates of the passive containment heat sinks and the activeengineered safety features (fan coolers and containment spray). Depending upon the magnitude of theM&E releases, the containment volume, and the effectiveness of the containment heat removal systems,the time of the peak containment pressure can vary from the early blowdown phase (less than 30 secondsafter event initiation) to the longer term post-reflood phase. The peak calculated pressure from the long-term LOCA containment peak pressure analysis (Pa) is contained in the Containment Leakage RateTesting Program Specification for most plants. IOCFR50, Appendix J, Type A, B, and C tests areperformed at the LOCA Pa.Sensitivities were performed to estimate the cumulative impact of the six issues on the calculated peakcontainment pressure value. The estimated containment pressure increase for the double-ended hot leg(DEHL) break case is approximately 0.1 psi and the estimated containment pressure increase for thedouble-ended pump suction (DEPS) break case is between 3.0 and 4.0 psi. Table I identifies which of thesix issues impacts each plant specific analysis and provides an estimated total impact on the containmentpeak pressure. While Westinghouse may not perform containment integrity analysis for all of the plantslisted in Table 1. estimates of the peak containment pressure increase are provided based on similar plantsensitivities and engineering judgment.Various changes to analysis input parameters can produce margin that may offset these estimated impacts.Therefore, plant-specific containment analyses are recommended to determine the actual impact on thecalculated peak containment pressure.Containment Peak Temperature AnalysesThe containment peak temperature analyses are performed to confirm that the upper limit of thecontainment liner design temperature is not exceeded. The containment vapor temperature can be higherthan the upper limit of the containment liner design temperature for a short period of time, since thethermal response time of the steel is much slower due to the surface heat transfer rate and conduction.The containment peak temperature for a large break LOCA is calculated using the containment peakpressure LOCA M&E releases as an input; however, the containment model initial conditions are adjustedto calculate an upper bounding containment temperature response. The containment temperature willincrease between I.0°F and 1.5°F per psi increase in the steam partial pressure. Therefore, the totalestimated increase in the containment peak temperature, considering all six LOCA M&E issues, isestimated to be less than 6'F.Containment Equipment Qualification AnalysesContainment equipment qualification (EQ) analyses are performed to confirm that the equipment pressureand temperature test envelopes are not exceeded during the time period for which the equipment isrequired to perform its safety function. These analyses use the long-term LOCA containment integrityM&E releases as an input.

NSAL-1 1-5Page 5 of 13The six LOCA M&E issues listed above affect the calculated energy release rates during the first hourfollowing a LOCA event. Typically, the margin between the calculated pressure and temperatureconditions from those contained in the EQ pressure and temperature profiles is tile greatest during the firstfew hours of the LOCA event. Exceeding the EQ pressure and temperature envelopes is typically aconcern well beyond the first hour of a LOCA M&E release. Therefore., these six issues should have verylittle impact on the long-term EQ.Containment Sump Temperature AnalysesContainment sump temperature analyses are performed to confirm the minimum net positive suction headavailable (NPSHa) for the emergency core cooling system (ECCS) recirculation and containment spraysystem (CSS) pumps is always greater than the required value (NPSHr). The NPSHa is the sum of theatmospheric pressure and static fluid heads, minus the sum of the velocity and vapor pressure heads. TheNPSHa decreases as the pump flow rate and sump temperature increase.The containment sump temperature response is calculated using the containment peak pressure LOCAM&E releases as an input, however, the energy released as steam is minimized in these analyses tomaximize the calculated sump temperature. Tile sump temperature is expected to increase slightly due tothe impact of these six issues.Various changes to analysis input parameters can produce margin that may offset the sump temperatureincrease (i.e., reducing the as-analyzed RWST temperature to the Technical Specification limit, reducingthe accumulator temperature to measured values plus uncertainty, etc.). For this reason, plant-specificcontainment analyses are recommended to determine the actual impact on the calculated NPSHa.Ultimate Heat Sink AnalysesAnalyses are performed to determine the energy load on the ultimate heat sink. The six LOCA M&Eissues listed above can affect the calculated energy release rates during the first hour following a LOCAevent. The energy in the containment atmosphere and the containment sump is eventually transferred tothe plant's ultimate heat sink. Typically, the loads on the ultimate heat sink are the highest shortly afterthe transfer to sump recirculation. The increase in the peak calculated temperature for the ultimate heatsink is not expected to be significant; however, the duration of the temperature increase may be longerthan currently analyzed. For this reason, plant specific containment analyses are recommended todetermine the actual impact on the ultimate heat sink analyses.SAFETY SIGNIFICANCEWestinghouse has assessed this deviation relative to IOCFR Part2l and determined that it would notresult in a substantial safety hazard even if left uncorrected. This conclusion was based on inherentconservatism in the Westinghouse LOCA M&E analysis methodology, WCAP-10325-P-A and WCAP-8264-P-A. Revision I (References I and 2, respectively), that are sufficient to offset the impact of theidentified errors.The Westinghouse LOCA M&E analysis methodology is based on non-mechanistic assumptions thatmaximize the M&E release rates during the first hour. These assumptions generate very limitingblowdown and post-blowdown peak containment pressure conditions that are extremely conservative.The non-mechanistic methodology assumptions are part of the approved methodology and theseconservatisms were not considered in the substantialPsafety hazard assessment; however, they arediscussed since they represent additional conservatism.

NSAL-1 1-5Page 6 of 13The post-blowdown LOCA M&E releases, when calculated with a more mechanistic LOCA analysis codelike WCOBRA-TRAC, are significantly lower than those calculated using the WCAP-10325methodology. As a result, the calculated post-blowdown containment pressure for the large dry and sub-atmospheric containment designs would be significantly reduced if the more accurate LOCA M&Ereleases were used.Additionally, because of the lower energy release rate, the time of ice bed melt-out in the ice condensercontainment design would be extended. This would result in a potentially lower sump temperature andpeak containment pressure, since the residual heat removal system would be able to remove energy fromthe containment sump over a longer period of time.Separate from the non-mechanistic assumptions are inherent input, initial condition, and modelconservatisms, which are sufficient to offset the impact of the identified errors for all plants. Section 5.1of WCAP-10325-P-A documents the conservatisms that are inherent in the methodology. Theseconservatisms include modeling aspects and initial conditions assumptions that result in a peak calculatedcontainment pressure that is a mininmum of 6 psi higher than what would be calculated with "morerealistic" input values. These inherent conservatisms also apply to the methodology described in WCAP-8264-P-A, Revision 1. If these more realistic input values were applied to the WCAP-10325-P-A orWCAP-8264-P-A., Revision I LOCA M&E release calculation methodology, a similar reduction in thecalculated peak containment pressure would be observed. The input, initial condition and modelassumption conservatisms include:* Core power and primary side fluid temperatures apply an uncertainty.* The RCS system volume used in M&E release calculation has an additional 1.4% for uncertaintyand 1.6% of the system volume is added for thermal expansion." Steam generator parameters are skewed to maximize available energy. These assumptions arebased on full power, maximum Tavg (with applied uncertainty), 0% SG tube plugging (assumingno fouling), maximum SG level plus uncertainty with an additional 10% increase in secondarymass.* Decay heat is maximized and a two sigma uncertainty has been applied to ensure conservatism.* Core stored energy is maximized by assuming the conditions at the most limiting time in life andmaxi mum core fluid temperatures." The moisture carryover fraction correlation used in the reflood transient for a DEPS break wasdeveloped for ECCS type applications for a DECL break. At the beginning of the reflood phasein an M&E energy release transient for a DEPS break, the initial core temperature is greatlyreduced compared to a DECL for a peak clad temperature analysis. This core temperaturereduction would greatly reduce the carryover fraction for a DEPS case by as much as 50%. Inturn, the releases to the containment would be reduced.Since the conservatisms in the LOCA M&E release calculation methodology offset the estimated penaltiesdue to the combined effect of the errors, it was determined that a substantial safety hazard does not exist.Appendix A contains information that can be used as input to an Operability Determination.

NSAL-1 1-5Page 7 of 13Additional margin in plant specific LOCA M&E analysis input values have been identified to offset thepenalties associated with these six issues. Analysis inputs where margin may be available are listedbelow." Crediting a lower maximum Tavg within the analyzed limits* Reduce the maximum initial accumulator temperature* Utilizing a maximum steam pressure that is lower than current analysis, yet bounding for plantoperation* Reduce the maximum refueling water storage tank (RWST)temperature" Revised drain down times for the RWST (which would delay the switchover to cold legrecirculation)* More accurate accounting of SG secondary side metal mass above the water level" Credit for extraction steam to run the turbine driven AFW pumps and valves" Plant specific valve closure characteristics for the main feedwater isolation valve closure time" Revised safety injection flow ratesThe following changes to the containment model inputs may also be used to offset the penalty due to thesix LOCA M&E issues and increase the plant specific analysis margin:* Lower the initial containment pressure* Identify ice mass margin (ice condenser plants)" Increase the containment spray flow" Improve the containment fan cooler performance" Increase the containment volume provided for the containment integrity analysis" Increase the containment heat sink massDepending on the magnitude of the analysis input change for a particular plant, the benefits obtained fromthe above items can be 0.1 psi to 0.5 psi for individual changes and combinations of several of these inputchanges have shown that the impact of the errors can be offset.AFFECTED PLANTS LISTThe affected plants and the estimated impact on the containment peak pressure values are listed inTable 1.NRC AWARENESSWestinghouse had a telephone conference call with the U.S. Nuclear Regulatory Commission (NRC)regarding some of these LOCA M&E release issues and stated that the margins that are contained in theWCAP-10325-P-A (Reference 1) methodology were the basis for the no substantial safety hazarddetermination.RECOMMENDED ACTIONS1. Determine the estimated impact by adding the estimated penalties provided in Table I to thecurrent licensing basis analysis of record calculated containment LOCA blowdown and post-blowdown peak pressure result values. Add any other known containment pressure penalties thatmay have been determined from plant specific evaluations.2. Determine the impact of the errors (from information provide in the Technical Evaluation andTable 1.) on the containment peak pressure and containment peak temperature/EQ. A plant NSAL-I 1-5Page 8 of 13specific analysis can be performed to determine these impacts, in addition to the potential sumptemperature and ultimate heat sink input impacts.3. Determine the available margin that may exist between the current analysis input assumptionsversus actual plant conditions that can be used to offset the estimated penalty.4. Revise the affected analyses as required based on revised analysis input assumptions to addressthese issues to offset the penalty.5. If it is ultimately determined that sufficient offsetting margin cannot be identified, an alternativeapproach may be considered such as a morse realistic analysis methodology.REFERENCESI1. WCAP-10325-P-A, "Westinghouse LOCA Mass and Energy Release Model for ContainmentDesign-March 1979 Version," May 1983 (Proprietary), WCAP- 10326-A (Non-Proprietary)2. WCAP-8264-P-A, Revision 1. "Topical Report -Westinghouse Mass and Energy Release Datafor Containment Design," August 1975.This document is available via the Internet at www.rle.westinghousenuclear.com. This web site is a free service forWestinghouse Electric Company LLC (Westinghouse) customers and other electric power industry-related organizations.Access will be provided based on Westinghouse's judgment of appropriate business affiliation. Westinghouse reservesthe right, at its sole discretion, to grant or deny access to this web site. Requests for access should be made togiampora@westinghouse.com.

NSAL-I1-5Page 9 of 13TABLE 1: LIST OF AFFECTED PLANTSEstimated PeakContainment Reactor Pressure Increase (psi)Plant List Scope Vessel Metal RCP Input SG Pressure Barrel Baffle EPITOME DEHL DEPSAlmaraz I & 2(8) Westinghouse L L I Upflow i 0.1 3.85A.W. Vogtle 1 & 2(l) Westinghouse Lj [7 Upflow 0.1 3.1Angra 1(1) Westinghouse Li Li Ui Downflow 1i 0.1 0.1API000* PWR Westinghouse Upflow N/A 0(5) 0(5)(7)Asco 1 & 2(8) No Scope F ', Upflow 1 0 3.45Beaver Valley 1 & 2 No Scope El L!sign [7 L Upflow Li 0.1 3.75Braidwood 1 & Byron I Westinghouse Upflow 0(5) 0(5)Braidwood 2 & Byron 2 Westinghouse Upflow 0(5) 0(5)Callaway I No Scope _ _ Lj EL Upflow LU 0.1 3.75Comanche Peak I & 2 Westinghouse LU Li , Upflow E, 0.1 2.45(6)Diablo Canyon 1(1) Westinghouse r] Li lI Downflow [E 0.1 3.1Diablo Canyon 2(l) Westinghouse LI FI Li Upflow Li 0.1 0.07(6)Donald C. Cook I & 2(2) Westinghouse -i Downflow LI 0 2.8H.B. Robinson 2 Westinghouse j [10 point , Downflow [7 0 3.0(6)Indian Point 2 Westinghouse Li L Downflow Li 0.1 3.45Indian Point 3 Westinghouse 7- Downflow 1 0.1 3.45Joseph Farley I & 2 No Scope I 7] Upflow Di 0.1 3.75Kewaunee Westinghouse L j L Downflow 11 0.1 3.45Kori I(]) Westinghouse E, FL0 point L Li Upflow -i 0.1 3.1Kori 2 No Scope [E K L] Upflow 1 0.1 3.75Kori 3 & 4 No Scope 0i [7 Li Upflow Li 0.1 3.75Krsko(8) No Scope L __ Downflow 7] 0 3.15Maanshan I & 2 No Scope Li ]1 f[ Upflow i1 0.1 3.75Millstone 3 No Scope D3 L [ Upflow N/A 0.1 0.75North Anna I No Scope [7 _3 L Upflow N/A 0.1 0.75North Anna 2 No Scope El L LI Downflow N/A 0.1 0.45Point Beach I & 2(l) (4) Westinghouse _F__ ____ Upflow 0(5) 0(5)

NSAL-I1-5Page 10 of 13TABLE 1: LIST OF AFFECTED PLANTSEstimated PeakContainment Reactor Pressure Increase (psi)Plant List Scope Vessel Metal RCP Input SG Pressure Barrel Baffle EPITOME DEHL DEPSPrairie Island I & 2(4) Westinghouse H- Downflow 0.1 3.45R.E. Ginna Westinghouse Li H _ Downflow 7 0.1 3.45Ringhals 3(8) Westinghouse T FT Downflow 0.0 0.5Salem I Westinghouse _____ [7 Downflow 0.1 3.45Salem 2 Westinghouse 1 i L] Downflow_, 0.1 2.8(6)Seabrook 1 No Scope H sign _ _ __ _ _ Upflow -_ 0.1 3.75Sequoyah I & 2(2) Westinghouse rj H Downflow 0 2.8Shearon Harris 1 No Scope Upflow 0(5) 0(5)South Texas I & 2 No Scope [ , _ _ Upflow r 0.1 3.75Surry I & 2 No Scope _ _ _ -" I Downflow N/A 0.1 0.45Turkey Point 3&4 (AOR) Li A0 point 1i E F](4) Westinghouse Downflow 0.1 4.3Vandellos 11(8) No Scope H _ Upflow 1 0 3.45V.C. Summer No Scope Fl ?Isign L 12 Upflow L] 0.1 3.75Watts Bar 1(2) Westinghouse L_ H _ Upflow F] 0 2.8Watts Bar 2(2) Westinghouse Upflow 0 0(5)Wolf Creek(3) No Scope H _ __ Upflow N/A N/A N/AYonggwang I & 2 No Scope F1 _ ] Upflow [ 0.1 3.75(I) Blowdown peak limited(2) Ice condenser containment, no blowdown peak(3) WCAP-8264-P-A, Rev. I analysis methodology(4) Recent EPU analyses are NOT impacted(5) Current licensed configuration recently reanalyzed for all issues so no penalty applies(6) Reflects internal evaluation impact(7) Double-ended cold leg break(8) Reflects a separate impact from steam generators without any tube fouling*API 000 is a trademark or registered trademark in the United States of Westinghouse Electric Company LLC, its subsidiaries and/or its affiliates. This mark mayalso be used and/or registered in other countries throughout the world. All rights reserved. Unauthorized use is strictly prohibited. Other names may be trademarksof their respective owners.

NSAL-1 1-5Page II of 13Appendix A: Information to be Used as Input to an Operability DeterminationLong-term Containment Peak Pressure Design Basis AnalysesThe post-blowdown LOCA M&E releases, when calculated with a more mechanistic LOCA analysis codelike WCOBRA-TRAC, are significantly lower than those calculated using the WCAP-1 0325 methodology.As a result, the calculated post-blowdown containment pressure for the large dry and sub-atmosphericcontainment designs would be significantly reduced if the more accurate LOCA M&E releases were used.Additionally, because of the lower energy release rate, the time of ice bed melt out in the ice condensercontainment design would be extended. This would result in a potentially lower sumnp temperature and peakcontainment pressure, since the residual heat removal system would be able to remove energy from thecontainment sump over a longer period of time.Separate from the non-mechanistic assumptions are inherent input, initial condition, and modelconservatisms, which are sufficient to offset the impact of the identified errors for all plants. Section 5.1 ofWCAP-10325-P-A documents the conservatisms that are inherent in the methodology. These conservatismsinclude modeling aspects and initial conditions assumptions that result in a peak calculated containmentpressure that is a minimum of 6 psi higher than what would be calculated with "more realistic" input values.These inherent conservatisms also apply to the methodology described in WCAP-8264-P-A, Revision 1. Ifthese more realistic input values were applied to the WCAP-10325-P-A or WCAP-8264-P-A, Revision 1LOCA M&E release calculation methodology, a similar reduction in the calculated peak containmentpressure would be observed. The input, initial condition and model assumption conservatisms include:" Core power and primary side fluid temperatures apply an uncertainty.* The RCS system volume used in M&E release calculation has an additional 1.4% for uncertainty and1.6% of the system volume is added for thermal expansion." Steam generator parameters are skewed to maximize available energy. These assumptions are basedon full power, maximum Tavg (with applied uncertainty), 0% SG tube plugging (assuming nofouling), maximum SG level plus uncertainty with an additional 10% increase in secondary mass." Decay heat is maximized and a two sigma uncertainty has been applied to ensure conservatism.* Core stored energy is maximized by assuming the conditions at the most limiting time in life andmaximum core fluid temperatures.* The moisture carryover fraction correlation used in the reflood transient for a double-ended pumpsuction (DEPS) break was developed for ECCS type applications for a double-ended cold leg(DECL) break. At the beginning of the reflood phase in an M&E energy release transient for aDEPS break., the initial core temperature is greatly reduced compared to a DECL for a peak cladtemperature analysis. This core temperature reduction would greatly reduce the carryover fractionfor a DEPS case by as much as 50%. In turn, the releases to the containment would be reduced.Since the conservatisms in the LOCA M&E release calculation methodology offset the estimated penaltiesdue to the combined effect of the errors, it was determined that a substantial safety hazard does not exist. Asdiscussed above, the WCAP-10325-P-A and WCAP-8264-P-A, Revision 1 methodology contains modelingand initial condition assumption conservatisms that result in a calculated peak pressure that is 6 psi higherthan the peak pressure that would be determined from a more realistic analysis. This 6 psi would offset theresulting increase in the contaiment peak pressure (Pa) associated with these issues. Therefore, if a morerealistic analysis were performed, Pa would not increase above the current value, and there would be noimpact on the IOCFR50, Appendix J, Type A, B, and C tests.

NSAL-1 1-5Page 12 of 13Discussion of Potential Impacts on other Design Basis Analyses andEvaluations that use the LOCA M&E Releases as an InputContainment Peak Temperature AnalysesThe containmrent peak temperature analyses are performed to confirm that the upper limit of the containmentliner design temperature is not exceeded. The containment vapor temperature can be higher than the upperlimit of the containment liner design temperature for a short period of time, since the thermal response timeof the steel is much slower due to the surface heat transfer rate and conduction.The containment peak temperature for a large break LOCA is calculated using the containment peak pressureLOCA M&E releases as an input; however, the containment model initial conditions are adjusted to calculatean upper bounding containment temperature response. The containment temperature will increase betweenI.0°F and 1.5°F per psi increase in the steam partial pressure. Therefore, the total estimated increase in thecontainment peak temperature, considering all six LOCA M&E issues, is estimated to be less than 6°F. EQprograms typically include approximately a 15'F peak temperature margin as discussed in IEEE Std 323-2003, "IEEE Standard for Qualifying Class I E Equipment for Nuclear Power Generating Stations."Typically, the overall limiting containment temperature is associated with a MSLB during the early portionof the profile (i.e., approximately the first 10 to 20 minutes) and the LOCA transient is limiting for theremainder of the profile (i.e., approximately 30 to 120 days).As discussed above, if a more realistic analysis were performed, Pa would not increase above the currentvalue due to these issues, and the containment peak temperature would not be impacted. Temperature is afunction of pressure; therefore, if pressure does not increase, temperature will not increase.Containment Equipment Qualification AnalysesContainment equipment qualification (EQ) analyses are performed to confirm that the equipment pressureand temperature test envelopes are not exceeded during the time period for which the equipment is requiredto perform its safety function. These analyses use the long-term LOCA containment integrity M&E releasesas an input.The six LOCA M&E issues listed above affect the calculated energy release rates during the first hourfollowing a LOCA event. Typically, the margin between the calculated pressure and temperature conditionsfrom those contained in the EQ pressure and temperature profiles is the greatest during the first few hours ofthe LOCA event. Typically, the limiting short-term containment conditions from an EQ standpoint areassociated with a MSLB. Exceeding the EQ pressure and temperature envelopes is typically a concern wellbeyond the first hour of a LOCA M&E release. Therefore, these six issues should have very little impact onthe long-term EQ.As discussed above, if a more realistic analysis were perfonned, Pa would not increase above the currentvalue due to these issues, and the containment peak temperature would not be impacted. Temperature is a NSAL-1 1-5Page 13 of 13function of pressure: therefore, if pressure does not increase, temperature will not increase. If the peakpressure and temperature are not impacted, then there would be no impact on long-term pressure andtemperature.Containment Sump Temperature AnalysesContainment sump temperature analyses are performed to confirm the minimum net positive suction headavailable (NPSHa) for the emergency core cooling system (ECCS) recirculation and containment spraysystem (CSS) pumps is always greater than the required value (NPSHr). The NPSHa is the sum of theatmospheric pressure and static fluid heads, minus the sum of the head losses and vapor pressure heads. Ingeneral, the NPSHa decreases as the pump flow rate and sump temperature increase due to the correspondingincreases in head loss and vapor pressure, respectively. However, in accordance with USNRC RegulatoryGuide 1. 1, the NPSHA is calculated assuming the atmpshperic pressure and vapor pressure are equal. Thiscalculational technique results in a slight increase in NPSHA as sump temperature increases due to reducedfriction losses.The containment sump temperature response is calculated using the containment peak pressure LOCA M&Ereleases as an input; however, the energy released as steam is minimized in these analyses to maximize thecalculated sump temperature. The sump temperature is expected to increase slightly due to the impact ofthese six issues.If a more realistic analysis were performed, the overall initial internal energy of the RCS would be lower andthe active containment heat removal systems would be more efficient. This would result in a lower mass andenergy release to the containment atmosphere and the sump and an increase in the energy removed from thecontainment. The result would be a lower sump temperature transient.Ultimate Heat Sink AnalysesAnalyses are performed to determine the energy load on the ultimate heat sink.. The six LOCA M&E issueslisted above can affect the calculated energy release rates during the first hour following a LOCA event. Theenergy in the containment atmosphere and the containment sump is eventually transferred to the plant'sultimate heat sink. Typically, the loads on the ultimate heat sink are the highest shortly after the transfer tosump recirculation. The increase in the peak calculated temperature for the ultimate heat sink is not expectedto be significant; however, the duration of the temperature increase may be longer than currently analyzed.If a more realistic analysis were performed, the energy transferred to the ultimate heat sink would be reducedas compared to the design basis analysis: therefore, the ultimate heat sink analyses would not be impacted.