ML20070F072
| ML20070F072 | |
| Person / Time | |
|---|---|
| Site: | 05200003 |
| Issue date: | 06/29/1994 |
| From: | Gresham J WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML20070F068 | List: |
| References | |
| PCS-GSR-001, PCS-GSR-001-R00, PCS-GSR-1, PCS-GSR-1-R, NUDOCS 9407180164 | |
| Download: ML20070F072 (44) | |
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l AP600 l Passive Containment Cooling l System Design Basis Analysis l Model and Margin l Assessment l
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I AP600 PASSIVE CONTAINMENT COOLING SYSTEM DESIGN BASIS ANALYSIS MODELS AND MARGIN ASSESSMENT I
June 30,1994 I l I
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AP600 DOCUMENT COVER SHEET TDC: IDS. I S Form 58202G(5/94) {tyxxxwpf 1x)
I AP600 CENTRAL FILE USE ONLY.
0058.FRM RFS#. RFS ITEM #:
AP000 DOCUMENT NO. REVISION NO. ASSIGNED TO h-g (d- OO l (') Page 1 of I ALTERNATE DOCUMENT NUMBER:
DESIGN AGENT ORGANIZATION: ,
WORK BREAKDOWN #: 2. (.o . L , L TITLE: A- P(ocac) )AssstrG b M M n m . M h M g' $ g D ty ht s, Aaljs %a % g4 gg ATTACHMENTS: _ DCP #/REV. INCORPORATED IN THIS DOCUMENT REVISION:
I I CALCULATION / ANALYSIS
REFERENCE:
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Copyright statement: A license is reserved to the U S. Government under contract DE-ACO3 90SF18495.
O DOE CONTRACT DELIVERABLES (DELIVERED DATA)
Subject to specified exceptions, disclosure of this data is restncted until September 30,1995 or Design Certification under DOE contract DE-ACO3-90SF16495. whichever is later.
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ORIG;NATOR EDA T%;,o L. u in 6 2 ,. s ef I AP600 HESPONSiBLE MANAGEF, mWaw, Sig4AT U . *
- yG a APPROVAL D TE w 6fM N I Approval of the responsible manager signif.es 1(At oocument is complete, all required reviews aie complets, electroruc f ie es attached and document is
- adcased for use.
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e AP600 DOCUMENT COVER SHEET Pegw 2 ,
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DEFINITIONS CONTRACT / DELIVERED DATA - Consists of documents (e.g. specifications, drawings, reports) which are generated under the DOE or ARC contracts which contain no background proprietary data.
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AP600 PASSIVE CWI AINMENT COOUW sVSTEM DFSIGN IIASIS A% LYSIS MonEL cNn MastGIN AWX% LENT l
I TAllLE OF CONTENTS Section ~ Title Pace EXECUTIVE
SUMMARY
I INTRODUCTION I
3 AP600 Design Overview 3 Passive Containment Cooling System Design Overview 5 I Design Certification Framework Role of Confirmatory PCS Test and Analysis Programs PCS Test Database Scaling 7
7 8
WGOTillC Code Overview 8 WGOTHIC Validation Objectives 9 WGOTillC Configuration Control 10 WGOTHIC CODE SENSITIVITIES 10 Large Scale Test Comparisons 10 WGOTHIC Sensitivity to Mixing 18 i SSAR ANALYSIS WGOTHIC Methodology Basis Summary WGOTHIC Validation Test Basis 22 22 22 WGOTHIC Boundary and Initial Conditions 22 Analysis Methodology 24 Loss of Coolant Accident Analysis Results 25 Main Steamline Break Analysis Results 25 I AP600 VERSUS CURRENT DESIGNS AND ASSUMPTIONS AP600 SSAR Analysis input Conservatisms 31 31 DEMONSTRATION OF ANALYSIS CONSERVATISMS 32 CONCLUSIONS 39 I REFERENCES 40 I
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Al%40 P4%rtt CosTatsMENT Crniuso sisTru DEsics Basts AN4 Lists MonEL nsa stanct% AMESNME%T I EXECUTIVE
SUMMARY
I he AP600 containment analyses are documented in Chapter 6 of the AP600 Standard Safety Analysis l
Report. In that chapter the results of the WGOTHIC analyses for the Loss of Coolant Accident and I I
the Main Steamline Break are presented. The analyses presented in the Safety Analysis Report have ;
been verified to be conservative using the latest version of the WGOTHIC code and the results of 1 I those reanalyses are contained herein.
The WGOTHIC code has been modified as a result of additional comparisons to large scale tests and refinements based on confirmatory phenomenological model evaluations with separate effects tests.
The principal modifications to the WGOTHIC code are the addition of mixed convection heat and mass transfer logic, and the incorporation of enthalpy transport into the passive containment cooling )
system film models. The inclusion of the enthalpy transport model permits the correct modelling of !
the subcooling effects of the exterior film. The reanalyses also incorporate minor containment and ,
large scale test model input modifications. He result of the input model :hanges is a reduction in the l I air velocity used in the calculation of the heat and mass transfer rates in the passive containment 1
l cooling system annular regions. He combination of model and code enhancements improve the 1 WGOTHIC comparison to large scale tests.
As demonstrated in the following report, the AP600 passive containment cooling system design basis l analyses presented in the AP600 Standard Safety Analysis Report clearly bound the results predicted l with the revised WGOTHIC version 1.2 code and input models. In addition, the margin to design I limits held by the conservative input model assumptions is demonstrated by analyzing the transients with the key input boundary and initial conditions set to nominal values. These analyses show that I
there is additional margin to the AP600 containment design pressure limits captured by conservative input assumptions.
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I , AP640 Pnssrvi: Co%TntNutwT Coottsu sisTIM DisicN linsts ANALYSIS MonLL AND MonGI% Assi3wti:NT I INTRODUCTION The AP600 Design Overview The AP600 plant has been designed to meet NRC and industry objectives of enhanced safety, reliability and economy. The design meets these objectives through a unique approach based on simplified safety systems that are passive, making use of natural circulation and gravity driven flow.
Rese systems make limited use of active comp (ments, which are only required for one-time valve alignments. The systems do not require pumps, fans, diesel electric generators or operator actions to accomplish their safety function. This approach has resulted in a significant reduction in the number of safety grade compcments, systems and structures as compared to current commercial reactor designs.
The application of these systems satisfies the goals of system simplification, reduced operator actions, I high reliability, minimum maintenance, and reduced plant size and cost, and are within the bounds of proven technology.
He overall plant design has been developed to ensure effective utilization of the design, operation, and maintenance experience accumulated over the past 30 years of commercial nuclear power generation, and in accordance with NRC plant licensing criteria. The passive safety systems operate on simple principles and have been verified through testing.
Ilased on earlier meetings on passive containment cooling system (PCS) design basis analyses, the NRC and Westinghouse have identified a need for additional documentation between design basis analyses (Reference 1) documentation, presented in Revision 1 of the AP600 Standard Safety Analysis Repon (SSAR), and Revision 1 to WCAP-13246 which will include all results from the confirmatory test analyses. Such documentation will be used to allow the NRC to include the most current status of passive containment cooling systems evaluations in their input to the draft safety evaluation report scheduled for November 1994. A schedule for Westinghouse passive containment cooling meetings I and reports has been established with the NRC to provide this documentation. Meetings with the NRC have been identified for 1994 and early 1995 to review the status and provide NRC consultants with information necessary to independently verify the calculations. A test facility scaling report has been segregated from the WGOTlilC validation repon to facilitate NRC review. A " single blind" test report and associated meetings have also been included.
Additional key reports are scheduled to be issue 1 to the NRC as confirmatory stage work is completed on the various phenomena important to passive wntainment cooling system performance. The first in I the series of passive containment cooling systems meetings has been held (Reference 2), in which WGOTlllC methodology as implemented for the design basis analyses, including comprehensive sensitivities to important passive containment cooling system parameters, has been reviewed. In that meeting, the NRC tequested that Westinghouse provide the following summary report that shows the effects of the confirmatory passive containment cooling system program and quantifies sigrdlicant sources of margin.
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APMW) PAssn F. CO%TAIN4ff%T COOUNG sVSTI:ht DE.StG% ILASIN A%4 lysis 5101111 Anti 314kGl% AssimNtIA'T I
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I The purpose of this report is to summarize supporting information for the AP600 SSAR relative to containment response design basis analysis methodology and to provide a status of the results of the confirmatory passive containment cooling system test and analysis program with respect to containment pressure margin. It is shown that AP600 containment methodology is consistent with approved methodology for currently licensed plants with respect to margins in boundary and initial conditions, and that the containment design has features which result in improved safety and I reliability.
I The WGOTillC code package is a tool for analysis of containment phenomena and the methodology for containment design basis analysis includes appropriate margins. A quantification of the principal margins in boundary and initial conditions for the code is provided.
The confirmatory passive containment cooling systems test and analysis program continues to I demonstrate additional margin relative to the AP600 SSAR submittal and provides scaling and model I u%pNo11073w.wpf:ll>M2994 4
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, Al%00 Passnt CosTatutt%T Coou%c SisTut DuiG4 Il4sts Ascusts Moria awn Mructs Assi.sustwT I validation via a process that is complete and auditable. Such ongoing work continues to demonstrate that the methodology used in AP6(X) SSAR remains conservative.
Passive Containment Cooling System Design Oserview The AP6(K) steel containment vessel prevents radioactive releases to the environment and serves as the I heat transfer path for reactor residual heat removal in the event of postulated pipe breaks inside containment. One of the primary accident mitigation features of the AP600, disdnguishing it from most currently licensed plants, is the reliance on a passive containment cooling system. Figure 1 illustrates key features of the passive containment cooling system.
The passive containment cooling system transfers heat to the environment, the ultimate heat sink.
I Ileat removal from the containment is predominantly by convecdon and evaporative cooling of the outside of the steel vessel. Outside air is directed by air baffles between the steel containment shell I and concrete shield building, cooling the outer vessel surface by natural convection. In postulated accident scenarios, this air-cooling is enhanced by the evaporation of water directed onto the steel containment shell from a 4(X),000 gallon annular storage tank designed into the roof of the shield building. This tank has sufficient water to provide three days of cooling, after which time, additional cooling water could be provided by operator action to maintain a low containment pressure and I temperature. Even if no additional water were to be pmvided at this time, air-cooling alone would be sufficient to maintain the containment pressure below the design limit. Since AC power is not required for design basis events, there is no reliance on offsite power for containment heat removal.
I The passive containment cooling system provides a logical extension of proven containment design ,
technology. Consistent with the objectives of advanced, passive plant development, design features of l the AP600 provide increased reliability in accident mitigation as well as in the fission product containment function. LOCA mass and energy release mitigation is improved by the use of passive !
I systems for primary inventory control. In the event of a pipe mpture, gravity injection from the in-containment water storage tank refueling, nitrogen pressurized accumulators, and core makeup tanks climinate the need for independent AC power sources, pumps, and operator realignment of equipment.
l I The fission product containment function is enhanced relative to currently licensed plants by the use of a design which requires only a one-time alignment of valves to release water onto the external steel I containment vessel. The AP600 containment vesselis constructed from a high strength SA-537 material, effectively providing a substantially Idgher safety factor for the design pressure used in the l
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I design basis analysis. This results in an increase in the margin between the ultimate pressure capacity of the vessel and the design pressure.
Additional containment related design features, summarized in Table 1, yield a design that results in increased safety and reliability. The containment volume is greater than for a standard two loop plant I allowing increased margin in pressure resp (mse to a postulated break, particularly during the blowdown phase. There are 809 fewer safety-grade pipes and less than half the number of valves and welds I u%gwou 073wgf:1bu 2994 5 s
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, APuHi Prwrtr Covt4tsurNT Coot.tso Mstru DistcN Itosis Asrt.Ysis Mont:1. AND Montcis AutMut:NT than conventional reactors, decreasing the likelihood of a primary side pipe rupture. Containment integrity is more easily assured since there are over 507c fewer penetrations, which also reduces the leakage rate. The containment is designed in advance for case of maintenance and operation with the ;
improved containment access and the increased containment diameter. Provisions are made that allow I inspection of the containment shell heat transfer surfaces. Exterior features such as doors and stairways allow inspections to verify adequate containment heat transfer capability, I TAllLE 1 COMPARISON OF AP600 TO Tile STANDARD 2 LOOP WESTINGilOUSE PLANT Plant Feature AP600 Standard 2 Loop Plant 7,210 ft. 44,300 f t.
I Safety Grade Pipe
(>2 inches)
Safety Grade Pipe 4,110 f t. 18,614 ft.
(52 inches)
Valves 1,528 2,553
(>2 inches)
Valves 3,678 8,820 (52 inches)
I Piping System Welds NSSS RCS 5,(H X) 15 10,fKX) 32 i
Containment Penetrations 40 93 Containment Diameter 130 f t. 109 ft. ;
Containment Net Free Volume 1,700.000 ft.$ 1.300,(XX) f t.' l Defense in depth is accomplished by the availability of the following heat removal mechanisms: j external air and evaporative cooling, external auxiliary connections to replenish the passive containment cooling system water, and external air cooling (without evaporative cooling).
The SSAR analyses, supplemented by this report, demonstrate that the AP600 passive containment ;
cooling system can m.t. gate the design basis accidents without the use of ac ive components such as fan coolers or sprays, even though fan coolers are available and are reliable heat removal mechanisms.
Safety and reliability for AP600 containment integrity is also enhanced due to the consideration of Severe Accidents and Probabilistic Risk Assessments performed in the early design stages, so the design includes consideration of such postulated conditions up front rather than as a backDt.
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The AP60() passive containment cooling system characteristics must be more critically addressed by the safety analyses due to the reliance on natural forces. There is a need to understand the effects of non-condensables and steam /non-condensable stratincation on containment heat removal. These u:\apta M 073w.wpf:1MWi2994 6
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AP600 pas 54rr. CosTAtwn:%T Coot.1%G StsTEM Drmc% Basis ANALYSTS MODEL A%D St4kGl% Asstassit NT i
I phenomena exist in current operating plants but are of much less importance in the presence of active l
j fan coolers and sprays. It must be demonstrated that the pressure peaks can be mitigated with passive systems. The effect of longer term adverse conditions on equipment qualification must also be 1
considered. All of these issues are addressed by the SSAR analysis methodology,in that the features '
of the AP600 containment have been analyzed and shown to protect the containment for the design basis accidents.
I Design Certification Framework A summary of the content of AP600 SSAR and WGOTHIC WCAP-13246 (Reference 3) has been j provided to the NRC (Reference 2). At that time, sensitivity studies for parameters potentially ;
affecting passive containment cooling system performance were presented. Such studies had been I used in the decision making process for design attematives to improve the AP600 plant concept. They also show that the containment pressure is not sensitive to wide variations in parameters. Therefore, uncertainties in most of those parameters have a small impact on AP600 SSAR design basis accident results and all sensitivities indicate a robust design. Such investigations have been performed to show that adequate design margin is pmvided for the passive containment.
I The conclusions from the March 17,1994 (Reference 2) meeting were that the passive containment cooling system performance predicted by WGOTHIC is well-behaved; the AP600 containment design g
g hasis accident boundary and initial condition assumptions are consistent with methodology approved for current operating plants. Ilowever, it was identined that additional information is needed by the NRC to understand the impact of confirmatory test and analysis work on AP600 SSAR conclusions.
Role of Confirmatory PCS Test and Analysis Programs The AP600 passive containment cooling system test program serves three purposes: to provide basic research and design information, to validate WGOTHIC calculation methods, and to develop
- I appropnate boundary conditions as input to WGOTHIC. The design basis analyses discussed in this report use tests to validate WGOTHIC calci.'on models. The passive containment cooling system test program has spanned over eight years and can be considered to consist of a design and model development phase prior to AP600 SSAR submittal and a subsequent confirmatory phase.
In the design and model development phase, engineering analyses have been used to demonstrate that the AP600 meets all relevant safety criteria with appropriate margins. The purpose of the confirmatory passive containment cooling system test and analysis phase is to demonstrate scalability and completeness of the methodology used. A blind test exercise has also been included to provide l
L further confidence that WGOTHIC meets the requirements for containment analyses and is able to adequately predict containment transient conditions. The AP600 passive containment cooling system tests and literature sources used in developing WGOTHIC contaitunent methodologies, such as boundary and initial conditions and code validation, are summarized under the discussion of the WGOTHIC methodology basis.
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APf*H PAssivr CosTAl%MI:%T CootJsu sysTI 4 DLsics hosts ANALists Mor>LL ANr> Manct% Anst_%4tt:s*1 I PCS Test Database Scaling I 13ased on discussions with the NRC and the ACRS, the Severe Accident Scaling hiethodology (SASN1) is being applied to the evaluation of passive containment cooling system perfonnance and the development of the WGOTlilC design basis code. The process shows that experimental and analytical methods used to resolve issues are comprehensive, auditable, systematic, and traceable. The purpose of the scaling methodology is to demonstrate that:
. All important phenomena have been addressed, and the relative importance is correctly ranked I . The test database is appropriate to validate WGOTlilC
. Factors affecting AP600 passive containment cooling system perfonnance have been clearly identified I Reports using the SASH 1 methodology and reviews in meetings with the NRC are scheduled to close out questions in this area. Preliminary results of the scaling evaluation indicate that the large scale test facility provides a good representation of the heat and mass transfer mechanisms associated with the passive containment cooling system. Although there may be some small, local distortions in ;
thermal-hydraulic phenomena, it is expected to be shown that the large scale tests remain adequate for I code validation. Therefore, comparisons ta the data from the large scale tests are presented in this report to support the conclusions regarding the acceptability of WGOTillC as an analysis tool, the safety margins, and the acceptability of the AP6(X) SSAR containment response analyses.
WGOTillC Code Oser iew I The AP6(X) test program, which is used to develop phenomenological models, such as the condensation heat transfer correlation used in WGOTIllC,is discussed in Reference 3. The AP6(X)
I passive containment cooling system test database is extended by the inclusion of separate effects tests from literature. The use of tests from the literature demonstrates that the methodology and test j
program are sufficiently diverse.
As a result of meetings with the NRC and the ACRS and in response to requests for additional !
information, detailed phenomenological model reports are being issued to confirm the validity of analyses performed for the AP6(X) SSAR. These reports provide a detailed comparison of each of the I
heat and mass transfer models to sets of AP6(K) data and literature data, and discuss the significance of ;
phenomena of interest in a fonnat consistent with a non-dimensional presentation of data.
hiinor enhancements to the calculational models in WGOTillC beyond version 1.0 used in the AP600 SSAR analyses have been made. Enhancements to the WGOTillC code subsequent to AP600 SSAR can be summarized as follows .
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I I, . APMN) P4ssivE CONTalutEST COOLING sV5 TEM Df.Mc% n4sts A%At.Ysts MODEL 4%T3 M ARGi% Asst 3s4f t NT I
- Entrance effects multiplier on heat and mass transfer coefficients I
- Addition of a log-mean noncondensable pressure term to the boundary layer mass transfer 1
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- Minor error corrections according to documented error repons for GOTIIIC and WGOTIIIC 1
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- Liquid film enthalpy transport
- Dimensionless group printout These modifications were made to allow: !
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- The modelling of separate effects and literature tests l'
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- Code calculation of mixed convection rather than user choice of free or forced i
. Successful predictions over the full range of separate effects condensation test data including the effect on mass transfer of the induced normal velocity component near the boundary layer I e (the " suction effect")
improvement in accuracy (mean values) of predictions i
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l Biese code enhancements meet the objective of developing an accurate tool for assessing the passive containment cooling system performance of the AP6(X). It is necessary to demonstrate understanding of important passive containment cooling system phenomena and their interactions in a large scale system. Using WGOTIIIC tool allows a more direct assessment of improvements in safety than if I bounding or limiting models are developed. For the design basis analysis, margins to safety limits can be quantified, and realistic guidance can be provided for emergency response planning.
WGOTillC Validation Objectives The AP600 passive containment cooling system represents a unique design which relics on evaporative and convective cooling systems. Since there was little or no data available, Westinghouse embarked on a thorough test and analysis program to verify this innovative design. The principal basis for I validation of the AP600 is the large scale test; however, a number of other tests are used to provide separate effects and integral systems data.
The tests can be separated into two categories: the short term or blowdown portion of the transient and the longer term balance of the transient. The AP600 containment response to the high pressure blowdown portion ofloss of coolant and main steamline break transients is not significantly different I than that for standard Westinghouse 2 kop plants. During blowdown, the time during which the u:\apMNA1073w.wpf:lb-062944 9
E , AP600 Passn r CO57AINFE%T Coou%G SYSTEM DESIGN Hosts A%4 Lists MODEL AND M4RGl% AN$lASMFST I coolant system contents is expelled through a postulated break, the large time constant for heat transfer through the containment shell causes the AP600 containment response to be governed primarily by the energy absorbed by pressurizing the internal containment volume and by heat removal by internal stmetures, historically referred to as heat sinks. Therefore, the predicted containment I resp (mse during the blowdown phase is similar to that for a standard Westinghouse 2 loop plant.
I The long term portion of the transient begins after the affected coolant system has blown down.
During this time period the mass and energy releases are greatly reduced and the passive coolant system is operating and transferring energy stored inside the containment to the ultimate heat sink.
The primary mechanism of heat removal from inside of containment is the condensation of steam on the inner side of the containment shell and its ultimate rejection to the environment via convective and evaporative cooling from the contaimnent outer surface. To a lesser degree radiative heat transfer also I assists in removing energy from the containment.
I Since the blowdown phase of this type of transient is governed, to the greater extent, by net free volume and internal heat sink surface area, the analysis focus has been on the balance of Ole transient.
As is shown in the section on "WGOTillC Comparison to the Large Scale Test Data", the WGOTHIC predictions are in good agreement with the test data. This demonstrates that the post-blowdown phase of the APfm containment analyses will be accurately predicted.
WGOTillC Configuration Control Details of the WGOTHIC developmem and Quality Assurance processes which clearly demonstrate which models are con'.ained ir: Specific versions of the code are provided in the May 25,1994 meeting (Reference 4). The AP600 SSAR version of WGOTHIC is maintained under configuration control and will be referred to as WGOTHIC 1.0 in this report. WGOTHIC 1.2 includes the upgrades described earlier in this report.
I WGOTIIIC CODE SENSITIVITIES l
Large Scale Test Comparisons The objective of this analysis is to demonstrate that version 1.2 is conservative and accurate, and to add confidence that WGOTHIC is an appropriate tool to model the AP600 passive containment l cooling system response.
To assess the effects of the WGOTHIC code modifications, baseline tests R7L, R1IL, R12L and R9L have been run with version 1.2 of WGOTHIC. These tests are discussed and the test conditions are given in Section 5.2 of WCAP-13246 (Reference 3). The noding as presented in WCAP-13246 is used in these analyses.
! u%p6m\l073w wpf.lbM2994 ]O
, Al%00 P4ssivt CoNTAINMETr Cmpt.ING SYSTEM Dt.slGN n4sts ANat.tsis MODIL AND M4kGIN AmLnMENT s
The containment pressure and axial wall temperature distributions are considered to be the primary measures of code success. Predicting the correct pressure indicates the correct amount of heat removal is being calculated. Predicting the correct wall temperature distributions is an indicadon that the steam and non-condensables concentrations are being calculated correctly. These parameters will be compared to measured results and presented in the same manner as in WCAP-13246.
Version 1.0 of WGOTIIIC does not account for the sensible heat of the cool external water as it is applied and flows over the dome. Therefore, the correlations were not used to model the large scale test facility dome where subcooling occurs. In the AP6(X) plant model subcooling was not simulated at all since the area over which the film could be subcooled was so small. A method to account for subcooling in the Large Scale Tests, while validating the wall heat and mass transfer, was developed.
The method is discussed in Section 9.2.2 of WCAP-13246.
A liquid film enthalpy transport model which models the transient energy equation for the liquid film is included in WGOTillC version 1.2. This climinates the need to simulate subcooling by the method used in WCAP-13246. The large scale test predictions presented are the result of using WGOTillC version 1.2 for internal and external heat transfer for the entire vessel and baffle.
The relevant test conditions and the vessel pressure predictions using WGOTillC version 1.0 and 1.2 are shown in Table 2.
TAlllE 2 1 ARGE SCAllTEST COMPARISONS Vessel External Test inlet Version 1.0 Version 1.2 Measured Test Wetting Film Water Steam Mass Calculated Calculated Test No. Percentage Temperature Flow Rate Pressure Pressure Pressure R7 OG, N/A 658 lbm/hr 95.9 psig 86.0 psig 78.2 psig RI1 67G 86*F 13M lbm/hr 29.4 psig 31.5 psig 28.1 psig R12 71G 66 F 3610 lbm/hr 33.4 psig 35.5 psig 29.0 psig R9 100G 50"F 3976 lbm/hr 6.2 psig 8.0 psig 8.7 psig Figures 2,3,4. and 5 show the WGOTlilC version 1.2 predicted and the measured vessel wall surface temperatures versus the vessel integrated surface area; the area integration begins at the bottom of the vessel. The wall temperatures are predicted very well with the exception of the temperature below the operating deck (at ~280 ft2 ). The test thermocouple is reading a relatively low temperature. This is caused by non-condensables collecting in the bottom of the vessel (Section 6.4 of WCAP-13246) causing less heat and mass transfer and thus a cooler measured wall temperature. The WGOTIIIC version 1.2 model is predicting the vessel is well mixed resulting in higher steam concentrations below the operating deck, thus the internal mass transfer is over predicted at this location.
u:VyW10\l073w wpf:llwori2W4 ]j g
I,
, APidM) Passn E Cos74tswr%T Conusc hisTf:st DE: sics Itasts Asat. hts Mot >t L c%1 %1Ancts AssrssMr%T I In Figures 3. 4, and 5 it is obvious that die subcooled enthalpy transport model along with the other code enhancements have resulted in good temperature predictions over the dome where the subcooling occurs. Figure 6 graphically represents the good agreement between the measured and predicted vessel pressures using WGOTillC version 1.2.
The code improvements incorporated into WGOTHIC version 1.2 result in good agreement with the large scale test data and further support the conclusions made in WCAP-13246 that:
- WGOTHIC gives a conservative pressure response
. WGOTillC is an acceptable code for containment analyses I
I '
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I 1 l
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u:hpNKA1073wspf:lt42094 12
I , . AP600 PAuryt: CosTAtsus %T CootN SYsitM Distc% ILuis AMLysis Monti AND Mancis AmtssursT I '
l 340
- \
I 320 - - - -
o.. -_g V
A
- -- w
_s3---- -e - - E --e-- ---o.
C
-a---
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-O 300 - - - - - - -- ---- ------ -- -- --- --- -- -- -- - --- -- -- ---- ------- --
I
~
280 - -- - -- -- - -- -- -- -- - * -- --- --- - - - ---- - '- -- - -
i
~
l 260 - --- --- -- -- --- - --- -- - - --- --- - - ------ -- - ---- - --- ---
C I
- i o
. . I 4
a t m
u E240 -- ---- - --- - --
I E
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=
m 220 --- -- -- ------ -- -- -- -- -- - ---- ------- ----- -- - --- --- - --- -
4 I 200 - ... . ...... ... ... .. .. .... .. ..... ... ........ ......... .... .. ..... .
180 - - - - - ------- - --- - - --- -- --- --------- ----- - - - - - -- -- -
160 - - - - - --- --
---h- -- ---- -- ----- -- - - - - - -- --- ----- --- -- - --
l l
140 I O.0 110.0 220.0 330.0 440.0 550.0 660.0 770.0 880.0 990.0 1,100.8 Integrated Vessel Area (ft^2)
Measured Predicted l
- . .. .o - . g I
Figure 2 Test R7L,0% Wet, Containment Vessel Temperature Profile, I WGOTIIIC Ver.1.2 I uhptda1073w.wpf:ltwo62W4 13
I, . APMN) Passivt costa:NMt:NT Coou%c SYSTEM DI.5IGN llAsts ANALuts hiott.L AND hickcIN Asst'.w.Mt%7 I
300 I _
280 - ~ - - ----- - -- - - - - - - - - - -- - -- - ~ ~ - - - --- --
i 260 -- -- -- -- - ---- --- - - - - - - ---- -- -- -- ---- - ---- - - - - -
=*j- - -
240 -- -- ----
--Wz- ;-- .- ::..:.:-Q
=
&==.5E=~E
. .g -
I
....m-C 220 - - - -- ---
- R. '"
- - ~ - - -- -- - - - - - - -- -- --
y _ ! ;3- -- -
I m , ~
-W~ T ~-
$200 --- - --- ~~~ - ---
- ^ -- ~~ - - - ~ ~
l 5 : O A A
I r- I
% V l B;180 - - - - - - - - -- ----- --- - - - - --- - ~ - - ~~~~ ~--- ~~~~ '
I
- 160 - --- - - - - ~ ~ ~ -- --~ ~ - - - ----- - - - - '~~~ ~ ~ - -
I 140
- - - - - - -~ ~ - -~ - -~ - - - - ~ ~ ~ ~ --- - ~ ~ ~ -~~
120 - - - - - - -- - - - - - -- -- - - - - - - ~~~~ ~ - - - - - - --
I 100 O.0 110.0 220.0 330.0 440.0 550.0 660.0 770.0 880.0 990.0 1,100.i Integrated Vessel Area (ft^2) l Measured Wet Predicted Wet
.-o-.
l Measured Dry Predicted Dry
.. 3 _ ._ g
)
j I
Figure 3 Test R11L,677c Wet, Containment Vessel Temperature Profile, WGOTillC Ver.1.2 uM;WYA1073w.wpf ItM2994 ]4
l I .
- AP600 PASStT E CONTAlWE%T COOUNG SWEM DE51GN 04 Sis A%ctYsis MonEL a%D Manct% Amtssurs r l
300 I _
l l
I 280 - - - - - - - - - - - ~ ~ -- -- - - - - ---- - - - - - -- --- - - -- -- - ~ ~ ~
- - - ~ ~
260 --- - - - - -- -- - --- - ~~- --~~ ~ - - - --
~
. .g --- 2-- ----2 *A l
- 9. -g .. ,,.3._ .
I 240 --- -
-- - - - - - ---~ -- --- - --
y
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~ 220 ---- - .~ -- -- - -- * -- -
E e
, - g-.O
~_-- --- -
,, 9 j--
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R200 - - - - - - ------ - ~ - -
-i -4 - - - - -- - - - - - +------ - ---- -- - ---
E A
/
I ii B 180 - - - - ~ ~ - - - - ~ ~ -
-- W - --- - - - - - -- - ---- -- - - - - - - - - - - -
5 I
160 ------ - - - - ------ - -- -- -- - - - - ------ ----
I 140
- - - - - ~ ~ ~ - - -- - ~~ ~ ~ - ~ ~ -- - - - - - ~~~--- ~~~-
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I 120
- - - ~ ~ ~ ~ ~ - ---- --~~~ - -- - ~~~~ - -- - ~ ~ -- ---
1 i
100 O.0 110.0 220.0 330.0 440.0 550.0 660.0 770.0 880.0 990.0 1,100J Integrated Vessel Area (ft^2) l l Measured Wet Predicted Wet c ._o. ;
l Measured Dry Predicted Dry
...g... O g Figure 4 Test R12L,717c Wet, Containment Vessel Temperature Profile, g WGOTillC Ver.1.2 1
u Aapt 00\l073 wspf:ltwo62944 15
. . APNeo PAssn1: CONTAINktEST Coousc SwrtM DE.sicN Rasts A%Aixsts moi >EL Anis MitctN AssrssMrsT I
200 180 - - - - - - - ---- - -- -- - ------- --- - - -------- -- -- - ------ - --- -- -- --
160 - - - - - -- - - - --- - - --- --- - --- --- - - ---- -- - - - --- - -----
Qs s,
i 140 - -- -- -------- ------ ^-- - - -- - -- -- -- -- --- ---- --- - - - --
s s
I 120
\
O s
s
/, -j 0---- -G , '
4 u.
s, N e
w -
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R100 - - - - - - --- -- - ----- --- --- - - -- -- --- -- - -- ---
I s
=
E o
c
% e0 - ... ... ....... ...... .. . ... .. .. . . ... . . . . .. .... . ....... .......
_ l l
60 - ------ - - --- ----- - ---- -- -- - -- - - -- -- - -- - - --- - - --
I
~
40 - - - - - ------ --- -- - ---- --- --- - - -- - --- -- -- - -- - --- - ----
20 - - - - - - - -- ---- -- - - -- ------ - - '- -- ------- - --- - - ----- - --- - -
0 O.0 110.0 220.0 330.0 440.0 550.0 660.0 770.0 880.0 990.0 1,100.4 Integrated Vessel Area (ft^2)
Measured Predicted
- --g-.
I Figure 5 Test R9L,1007c Wet, Containment Vessel Temperature Profile, WGOTHIC Ver.1.2 u:\ap60lM 073w3pf:lb-062994 16
- AP600 Passivr Co .TatetE%T CowiLi%c SYSTEM DrslGN ItosLs ANALYSIS MotiEL 4%D MAuct% ANSESSMENT l
120 I ./
/
/
i
/
/
100 - - - - - - -- -- -- - - -------- -- ---- ---
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80 - - - - - - - ----- -- ----- - ---
--y*-- -- -- - -- - -- -
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m 60 - - - - - - -- --- - - - --- -- - --- /-- - - - - - - - ----- - -
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. . . . . . . . . . . . , i.... . . ..... . . .... .. ... .... .. .. ... . . .. ... ...
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n l 20 -----------i
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./
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0' ' ' ' ' ' '
0 20 40 60 80 100 120 Measured Pressure (psia)
Dry LST Wet LST o
- I Figure 6 Large Scale Test Measured Pressures Versus WGOTIIIC Ver.1.2 Predictions I
unapNYA107.1wspf:lt>M2994 17
, . APWI PrutVr Co%TAIntr%T Conusc M m3t Druc% ltests A%Atists stonit. 4%D \1ancis AwLsnti's7 WGOTIIIC SENSITIVITY TO MIXING I The AP6f X) SSAR presents the pressure and temperature predictions for the AP6(K) containment following a loss of coolant accident and main steamline break. The pressure and temperature calculations, performed with the WGOTillC computer code, predicted a well-mixed containment.
110 wever, the AP6(X)large scale tests results showed less mixing. The large scale test results indicate that the steam and air tend to separate and stratify within the containment.
The results predicted by WGOT111C are consistent with the use of lumped parameter noding within the AP6(K) containment model. Variations in fluid conditions within volumes can be better modelled using a distributed parameter noding scheme. This method can increase the accuracy of the ,
calculations. 'Ihe AP6(K) SSAR model and large scale test models were constructed using lumped parameter nodes. The stratification of steam within the vessels was underpredicted using this methodology.
Evaluation of the WGOTillC heat and mass transfer correlations has resulted in the conclusion that a well-mixed containment is conservative for calculations of passive containment cooling system heat removal. Mixing in the AP6(4) containment will increase the predicted air concentration above the operating deck. This increase in air concentration results in a net decrease in heat removal.
Discussion I Convective heat transfer in WGOTillC 1.2 is based uptm the correlations from McAdams and the flatplate correlation for free and forced convection, respectively. The mass transfer correlation is derived form the heat transfer correlations using the heat and mass transfer analogy.
I The mass and heat transfer coefficients resulting from the above correlations are directly dependent on the quantity of air and steam present. AP6(X) large scale tests show that the air and steam are I expected to tend to separate and stratify within the containment following a postulated accident. The tests showed the existence of an air rich region below the injection point and a steam rich region I above this point. The injected steam forms a buoyant plume and rises from the point of injection. As the steam rises it entrains some of the surrounding air. Once the steam-air mixture reaches the top, condensation removes some of the steam. The remaining steam-air mixture is heavier than the adjacent fluid and begins to fall. As the fluid progresses downward along the sides of the containment wall, additional condensation occurs. Finally, the heavier air sinks to the bottom of the vessel.
The stratification of steam was not predicted with the lumped parameter large scale test model.
During the initial blowdown depressurization in the AP6(X) model, WGOT111C predicts variations within the subcompartments due to the etfects of the primary system blowdown.110 wever, following blowdown, WGOTillC begins to predict a mixing of the containment. With the exception of some
" dead-ended" compartments, well-mixed conditions are achieved throughout containment within the first one thousand seconds.
u:\apNIOuO7kupf:lt42W4 18 r--
I.
AP(M Passrvr Co%Tatut:37 CoouNG SuTt:M DEstGW Basts ANcLuis h1 ODE:L AND N14kGl% AssExutt %T I In the AP6N and the large scale test facility, the passive containment cooling system operates form the top for the containment vessel to the operating deck level. It is in this region where steam tends to concentrate. The net result of WGOT111C predicting a well mixed containment is an increase in the air concentration above the operating deck in the region of the passive containment cooling system.
As indicated earlier, the heat and mass transfer coefficients are directly relat:d to the relative amounts I of air and steam present within the gaseous mixture. Figures 7 and 8 show calculated mass transfer coefficients for free and forced convection at various steam and air concentrations. The figures confirm that mass transfer coefficients increase with increasing steam concentration. Through the heat and mass transfer analogy, the same conclusion can be applied to the heat transfer coefficient.
Since WGOTillC over predicts mixing within the containment, the air concentration above the I operating deck region will be greater than actual. Therefore, the overall predicted heat and mass transfer coefficients for the passive containment cooling system will be lower than the actual heat and mass transfer coefficients.
He AP6tX) WGOTillC containment model has predicted a well-mixed containment following a postulated accident. This large scale test showed that the steam and air tend to stratify within the containment. A well-mixed containment is conservative for predictions of passive containment cooling system heat removal since more air is present in the upper containment reducing the heat transfer to I the containment shell.
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I I uMpfdP.1073w.wpf.lb42904 j9
. xi un, ..ssn, cosniw m c. ,usc smni n,s1G% Hrsts ANAusts MODE AND MacW Assi;ssstIM i
I l l Mass Transfer Coefficient l Versus Steam Concentration l
cm l c.,0.0006 o
I I O -
w 1
(N 0.0005 - - - - - - - - - - - - - - - - - - - - - - - " - - - - - " " " " " - - - " - " " - -
u-N -
e
=
O 0.0004 - - - - - - - - - - - - " " - " " - - - - - - -
I v
c -
er O g -
o 0.0003 - - - - - - - - - - - - - - - - - - - - - - - - - - - " " - " - " " - - - - - " - " - -
C L
I 0
O U 0.0002 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - " " " " - - " " " - - " - - " -
I 6 L
U m
9,999} - ..... ..... ..... ........ ..... ......... ....................... .................
E L h4 -
I m z 1 I .l. I I j- 0 0.2 0.4 0.6 0.8 1 1.2 l steam concentration Free Convection P=30 psig, T=300 F. T(film)=265 F I
Figure 7 WGOTillC Ver.1.2 Free Convection Mass Transfer Coefficient Versus Steam Concentration I - _ , , , _ 2o
I.
- APf.O PASSIVE CONT 4t% MENT COOUNG M STEM DLMGN H4sts ANALisis MoDEt, G%D MakGIN AssEssME%T I
I I Mass Trans er Coefficient l Versus
.c z
Steam Concentration cu0.0014 i
O I
O z
N' O.0012 N
~
e-
= 0.001 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
o v -
w
= 0.0008 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
.O -
O -
l C "O0.0006 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
o _
U u 0.0004 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
6 O
m ~
m m
6 0.0002 - - - - - - - - - - - - - - - - - - - - - - -
m m I I I l I
[ y m 0 0 0.2 0.4 0.6 0.8 1 1.2 Steam Concentration Forced Convection P=30 psig, T=300 F, T(film)= 265 F, V=5 ft/sec
[ Figure 8 WGOTillC Ver.1.2 Forced Convection Mass Transfer CoefUcient Versus Steam Concentration r-uM;W.00\1073w.wpf:1M6254 21
- APMH) passive CONTatutE%T ConLING sVSTEM DESIGN 84sts A%4 Lists MoDEL AND NtARGIN AssLwME%1
'I SSAR ANAIJSIS i WGOTillC Methodology liasis Summary The basis of WGOTillC methodology can be considered to be separable into three areas: development of phenomenological models; validation of the WGOTHIC code; and development of conservative I boundary and initial conditions for WGOTillC design basis accident analyses. WGOTHIC has been developed as a tool for modelling containment phenomena.
As is shown in the analysis results sections, there is substantial conservatism included in the AP600 containment design basis analyses. The conservatism is primarily in initial and boundary conditions, although additional conservatism exists in the AP600 SSAR analyses resulting from recent I phenomenological model enhancements and also from ovenuixing of containment as discussed in the WGOTillC Sensitivity sections. Table 3 summarizes the test data basis as used in the AP600 WGOTillC methodology for design basis accidents. 1 WGOTillC Validation Test liasis I The phenomenological models used in WGOTIllC have been developed based on separate effects tests l and literature reviews as shown in Table 3. Phenomenological reports have been issued or will be for:
. liquid film heat transfer coefficient I .
fog in the riser annulus boundary layer correlation for convective heat transfer e condensation and evaporation mass transfer, including effects of inclined plate
- convective heat transfer basis with respect to laminar / turbulent flow
. internal transients and stratification processes The WGOTillC code validation is primarily based on comparisons to AP600 passive containment -
cooling system integral system tests in the large scale test facility. To provide additional confidence in l the predictive capability of WGOTHIC, a single blind large scale test analysis is planned.
WGOTillC lloundary and Initial Conditions Other tests have been used to determine appropriate boundary or initial conditions for use in the AP600 WGOTHIC model. Reports have been issued or are to be issued for:
I I
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- APfiDO PassiVr Covwwt%T CmuNG $Ysim litsIGN H4sts A%ct.Ysts MoDEL AND DRGl% AsstssMENT l
ll
- TABLE 3
SUMMARY
OF TEST IIASIS FOR APMX) WGOTillC CONTAINMENT Dita METilODOLOGY
! Methodology Category Topic Tests Used in Validation Analytical liasis i l
Model Devekipment Free Convection Vliet angled Hat plate McAdams i Heat Transfer Forced Convection STC dry flat plate Colbum Heat Transfer Mixed Eckert & Diaguila's Churchill I Convection database Hugot data Siegell & Norris data i ANL data Miyamoto data SST data LST data Mass Transfer Univ. Wisconsin data Heat / Mass STC flat plate data Transfer Analogy Sherwocxl data Liquid Film lleat Transfer Chun & Seban data Chun & Selun Univ. Wisconsin data l I WGOTillC Validation Integral Systems Interaction LST data Internal Flow Fields I Internal Non-con-densables Internal Condensate Potential for Rain Extemal Free Convection Condensauon/ Convection Evaporation / Convection Univ. Wisconsin data STC flat plate data I WGOTHIC Input /
Boundary Conditions External now path loss coefficients External flow path AP test Bench Wind Tunnel Wind External flow path - density Tunnel Phases 1,2AAAB head only Water Distribution Tests I Vessel wetting fraction and delay Phases 1,2,3 I
I I _ , _ n
,rV AP(m Prutva: COVI AINMLST COOU%G sHTE:M DLNG% B4Ms As4Lnts MoniL AND M4kats Amtswit:NT L
. external density driving head, including effects of wind and turbulence due to buildings and terrain, based or wind tunnel Phases 1, ?, and 4, demonstrating a largely wind-positive design, .
and allowing wind effects to be conserv ttively neglected
[
- uniformity of static pressure at bottom of lai;e de vncomer plenum, allowing assumptiori of uniform driving pressure in the four quadrants of AP600 WGOTillC model
{
In the next section, the SSAR reanalyses are discussed. The modifications that were incorporated into the WGOTHIC input deck are presented. The results of the reanalyses are also provided.
ANAI,YSIS METilODOI.OGY The AP600 containment model input deck used in the AP600 SSAR Rev. O analyses was revised to utilize the latest version of the WGOTHIC code, Version 1.2. The following input changes were made to the base WGOTHIC AP600 SSAR containment model.
! The annulus flowpath inertia lengths were modified to balance the steady state volume average velocity with the corresp(mding flowpath velocity.
- 2. Ileat and mass tran&r multipliers, which are needed to account for entrance effects in the annulus, were calculated and applied to the lower, upward flowing volumes of the annulus.
L
- 3. Inner vessel wall heat transfer multipliers were computed and applied to the inside surface of
- the containment to convert from the Colburn correlation to the flat plate correlation.
L
- 4. The annulus hydraulic diameter input was changed to be consistent with the mixed convection heat transfer correlation with entrance effect multipliers applied.
- 5. In the original SSAR analysis, a constant break droplet diameter was used throughout the entire transient, even though liquid was expected to spill from the break after blowdown was complete. A forcing function was applied to climinate the formation of a drop field after the r blowdown phase is complete.
6, The number of subregions in the larger, outer concrete sections of two conductors were reduced.
- 7. Based on the results of the loss of coolant accident analyses no significant level of zirconium-r
( water reaction occurs so the energy release was excluded from the mass and energy calculations.
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u An[WKh1073w.spf:ltvo62004 24 _
- I APfm Paurvt Cos7a:Nurs7 Coousa synru DisicW hosts Asattsts Moint1 cNo Manc N Amtswit sT l I De modifications described above were incorporated into the AP600 base input deck. This deck is used for both the loss of coolant accident and main steamline break analyses. He results of these analyses are presented below.
1,oss of Coolant Accident Analysis Results I %e AP600 SSAR loss of coolant accident and main steatrJine break containment analyses were re-run to assess the effects of the WGOTillC code modifications and input changes which have been made since the original analyses were completed. Figure 9 and Table 4 show a comparison of the loss of coolant accident transient pressure results. The blowdown peak pressure was 36.7 psig and the transical peak pressure was 39.5 psig (which occurred at about 1100 seconds) in the original SSAR analysis. With the improved heat transfer calculations in WGOTIIIC version 1.2, the transient peak iI pressure occuned at the end of blowdown and was 36.5 psig. De blowdown peak pressure is relatively independent of the wall heat transfer since the thermal lag time and passive cooling system g initiation time are longer than the time to reach the end of blowdown; therefore, it was not a significantly affected by the code changes made to create WGOTHIC version 1.2. De wall heat transfer changes should affect the transient results later in time - v.hich they did. De second peak was approximately 4 psi lower using WGOTillC version 1.2.
I Figure 10 shows a comparison of the loss of coolant accident break companment transient temperature results. De temperature response is nearly identical during the blowdown phase (as was expected);however, the WGOTillC version 1.2 temperature transient is higher from 60 to 300 seconds.
This is due to the input change in the break drop diameter after blowdown. De drops were able to remove heat flike a spray) during this time period in the original SSAR analysis. The break compartment temperature, as calculated by WGOT111C version 1.2,is lower for the rest of the transient due to the improved wall heat transfer.
TAltLE 4 APHO SSAR REY. O VERSUS WGOTIIIC VER.1.2 RESULTS Case SSAR Pressure Version 1.2 Pressure Double Ended Cold Leg 39.5 psig 36.5 psig I
Main Steamline lireak Analysis Results The two main steamline break cases presented in the AP600 SSAR were remn using WGOTillC sersion 1.2. The mass and energy releases were regenerated using the methodology consistent with standard plants for these cases. De assumptions made for the revised main steamline break mass and energy release calculations are:
u%peaNON.wpf.lM162994 2$
l
- APMH) PcsmT Co%TatNMr%T CooIJ%G SYSTI.M DESIGN B4 fits A%Atysis MoDIL AND ht4kGIN A%IK%411l%T I = The rated full power Reactor Coolant System temperature increased from 562.8*F to 565.9'F I =
=
=
The steam generator narrow range level span increased from 210" to 240" Minor corrections to an unisolable steamlir.c volume Passive Residual Heat Removal actuation on the Core Makeup Tank actuation signal l
= Reduced low Tcold startup feedwater isolation setpoint of 490*F
= AP600 revised feedwater flows I These modifications resulted in a decrease of approximately 2.4% in the mass and energy releases for the 30% power case and a 4% reduction for the 102% power case. ' Die results of these two cases are presented in Figures 11 and 12 for pressure and temperature respectively. The revised analysis values )
versus the AP600 SSAR values are presented in Table 5. l 1
1 TAllLE 5 l AP600 SSAR VERSUS WGOTillC VER.1.2 j MAIN STEAMLINE IIREAK RESULTS Case SSAR Pressure Version 1.2 SSAR Version 1.2 Pressure Temperature Temperature l
309 Power 41.4 psig 35.4 psig 305.1 *F 320.l *F 102% Power 41.2 psig 34.4 psig 320.3*F 321.2*F I
I I
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E u:%pMVA1073w.wpf.1MR,2904 26
APfho PAssrvr CONTAINMr%T Coou%c SysTI:M Desic% It4sts A%At.ists biol EL A%V htARGIN ARstr.shtt:%T I
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1 YVALUE 0 SSAR Press (Ver 1.0)
I 1 0 s sYVALUE 1 0 0 SSAR Press (Ver 1.2) 60
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10 O 1 2 3 4 5 10 10 10 10 10 10 Time (seconds)
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F k Figure 9 AP600 LOCA SSAR Version 1.0 Versus Version 1.2 Pressure Comparison a
_ u:h tWRh1073w.wpf:lt>M2994 27 ._
l* APMW Passive Co%Tatwtr.NT CoouNG $nTEM DistCN llasts A%Luis MonEL a%D Mancis Asistasscr% r I
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I YVALUE 1 0 0 SSAR Temp (Ver 1.0) 0 SSAR Temp (Ver 1.2)
, aYVALUE 1 0 I 300 I :
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L E Figure 10 AP600 I.OCA SSAR Version 1.0 Versus Version 1.2 Temperature I- Comparison n
u:\apNU1073w.wpf;1M62991 28 ,
APMH) PA%2fVE COYTAINMENT COOUNG SYSTEM DINGN I!ASI% ANALYSIS MODE 1. AND MARGtW AssiwMENT I
I I
102% Power. WGOTHIC Ver. 1.2 E ---- 30% Power. WCOTHlc Ver. 1.2 102% Power. WGOTHIC Ver. 1.0 l
I ---30%
60 Power. WGOTHIC Ver. 1.0
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! Figure 11 Main Steamline lireak Containment Pressure Transient with WGOTIIIC Ver.1.2 I u:\apMO\lomw.wpf.!N062W4 29
AP600 PA%SIVE CONTAINMENT COOUNG hYFTEM DESIGN Basis ANALYSTS MODEL AND MARGl% A!sst3sME%T '
I I l I
102% Power. WGOTHIC Ver. 1.2 l I ----30% Power. WGOTHIC Ver. 1.2
102% Power. WGOTHIC Ver. 1.0
--- 30% Power. WGOTHIC Ver. 1.0 350 n
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O Time (sec)
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- I Figure 12 Main Steamline Ilreak Containment Temperature Transient with I WGOTillC Ver.1.2 uwxNo73 *vf
- it>o82994 30
APf40 Pawtvr Co4TorwtE%T Coousa SYSTEM DratcN Bosts A%cLysts MoDEL cWu McRGIN AwEssut%T AP600 VERSUS CURRENT DESIGNS AND ASSUMPTIONS AP600 SSAR Analysis Input Conservatisms The SSAR LOCA mass and energy release analysis was performed using assumptions which would maximize the initial system mass and energy available for release to containment. These assumptions, which are consistent with current licensing design basis analysis assumptions, yield a conservatively high estimate of the containment pressure and temperature response following a LOCA event. He conservatisims in the AP600 mass and energy release calculation are listed below:
- 1. The maximum expected RCS full power operating temperature is used to maxindre the initial mass and energy available for release to containment. An additional 5* F is added to account for instmment error
- 2. The volume of the RCS is increased by 39:: to account for thermal expansion and uncenainty in as-built dimensions. Tids increases the initial mass and energy available for release to containment
- 3. The core licensed power level is increased by 29 to account for calorimetric error
- 5. The initial core stored energy is increased by 157c to account for manufacturing tolerances and to account for fuel densification
- 6. The initial system pressure is increased by 30 psi to account for instrument uncertainty. Tids increases the initial mass and energy available for release to containment
- 7. We containment design pressure is used as the back-pressure for the blowdown calculation.
This increases the mass and energy release rate because the steam density is higher
- 8. We 1979 decay heat standard with 2 sigma uncertainty, all U-235 fission, and 3 years full power operation is used to maximize the core decay heat
- 9. The full power SG secondary mass is increased by 107c The SSAR containment model was created using assumptions which would maximize the initial stored energy within containment and minimize the rate of heat transfer from containment. These assumptions yield a conservatively high estimate of the containment pressure and temperature response throughout a transient event. He conservatisms in the AP600 containment model are listed below:
1, De maximum outside air temperature of 115'F is used as a boundary condition to reduce the heat transfer rate from containment uwwxnio7h.wpf.tiwen4 31 ,
l
I 8* AP600 Pcssivt cont 4tutE%T Coou%c sisTEM DEsic% Itasis A%4 Lists MoDEL AND h1ARGt4 Asst. ssMf'%I l l
i
- 2. The maximum containment air temperature of 120*F, pressure of 1 psig, and 100% humidity l initial conditions are used to increase the initial stored energy inside containment I
- 3. The subcooling of the passive containment cooling system water temperature is ignored to reduce the heat transfer rate from containment I 4. A single failure of I out of 2 valves controlling the passive containment cooling system cooling water flow is assumed. This assumption provides the minimum passive containment cooling system liquid film flowrate and reduces the heat transfer rate from containment I 5. The passive containment cooling system liquid film flow is initiated following an 11 minute delay period. This corresponds to the time needed to establish a steady liquid film coverage I pattern in the liquid film distribution tests I 6. A 409 passive containment cooling system water film coverage is used on the top of the dome and 70% coverage is used on the side walls. These values are based on the minimum coverage observed in the liquid film distribution tests I 7. The vessel wall emissivity values were reduced by 10% to reduce the radiation heat transfer i
Demonstration of Analysis Conservatisms l
I As described in the Analysis Methodology section, the SSAR containment model input was revised to use version 1.2 of the WGOTHlC code. This revised deck was changed furtler to climinate a portion of the conservative assumptions described above in the section on Analysis input Conservatisms. The I
i following changes were made to create a containment model with nominal operating conditions:
- 1. The initial outside air temperature was set to 70* F (nominal value) l l
i
- 2. The initial containment air temperature was set to 100* F and the relative humi:lity was set to 89 (nominal value)
- 3. The initial containment pressure was set to 14.7 psia (nominal value)
- 4. The corresponding conductor initial temperatures were set to 70*F and 100* F 1
- 5. The passive containment cooling system water temperature was set to 80* F (nominal value) 1
- 6. The material emissivities were modified to remove the 0.9 multiplier fl u%p60th1073w.wphlM62%4 32
I I
Arto rw.svE covmwEvr coou%G s)FTEM IMNGW basis AsnYsis MODEL ep McHcr* AussMEm I Re LOCA mass and enugy release calculation was also revised to eliminate some of the conservative assumptions described in the Analysis input Conservatisms Section. The following changes were made in the calculation of the mass and energy releases:
- 1. The nominal full power temperatures (without adding 5*F for instrument uncertainty) and j normal operating RCS pressure were used l
- 2. The nominal RCS geometric (cold) volume (without uncertainty) was increased to account for thermal expansion only I 3. The core licensed power was used (without adding 29 for calorimetric error)
- 4. The nominal core stored energy was used (without adding 159 for tolerance)
I 5. The 1979 decay heat standard (without uncertainty) for an 800 day average burnup was used to estimate the core decay heat l
- 6. The nominal full power SG secondary mass was used (without adding 109)
The revised mass and energy releases were input into the WGOTHIC version 1.2 containment model I to determine the effects on the LOCA containment pressure and temperature response. Figure 13 shows a comparison of the transient pressure results. The blowdown peak pressure was 36.7 psig and I the transient peak pressure was 39.5 psig (which occurred at about 11(X) seconds)in the original SSAR analysis. Using the nominal input conditions listed above and more representative mass and energy releases, the blowdown peak pressure is reduced to 33.1 psig (about 3.4 psi lower). The second peak is also lower and occurs earlier in time,28.9 psig at around 900 seconds. The reduction in the second peak is caused by a combination of using the nominal initial conditions, representative mass and I energy releases and the improved heat transfer correlations in WGOTHIC version 1.2. Figurt 14 shows a comparison of the break compartment transient temperature results. The tempi rature response is nearly identical during the blowdown phase and the WGOTHIC version 1.2 tew,crature transient is lower for the rest of the transient (as expected).
His same input deck was used with the main steamline break mass and energies as used in Figures 11 and 12. The revised main steamline break mass and energy release calculations do not take credit for the same input assumptions as were made for the nominal loss of coolant accident mass and energy I release calculations. He results for he main steamline break cases assuming only nominal containment conditions are presented in Figures 15 and 16. The results of all cases presented in this report are summarized below in Table 6.
l I
I u%pNKn1073w.wpf:Ibh2994 33
r AP600 Passive Co%TcINMENT Coou%G SYSTEM DESIGN llasts ANALVsis MonrE cNo MamGIN Asst.ssME%T l
TAllLE 6 I OVERALL CONTAINMENT INTEGR11Y RESULTS COMPARISON Parameter DECLG LOCA MSI.11 M S Lil I 102% Power 45.0 psig 30% Power 45.0 psig AP600 Design 45.0 psig ;
I SSAR Peak Pressure 39.5 psig 41.2 psig 41.4 psig WGothic Version 1.2 Pressure 36.5 psig 34.4 psig 35.4 psig I Norninal Conditions Pressure 33.1 psig 32.4 psig 33.2 psig l
l
)
9 Margin SSAR to Design 12.2G 8.4 % 8.0 %
G Margin Ver.1.2 to Design 18.9% 23.6 % 21.3%
% Margin Nominal to Design 26.49 28.0 % 26.2 %
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e 1 AP600 Passive CosTotutE%T ContrNG SYSTEM IDESIGN 116 515 ANAt.Ysts MODEL AND M4Rcg% AssEssMI NT i l
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YVALUE 1 0 0 SSAR Press (Ver 1.0) u .YVALUE 1 0 0 Case 3 Press 60 I
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0 1 2 3 4 5 10 10 10 10 10 10 Time (seconds)
Figure 13 AP600 LOCA Design Initial vs. Nominal Initial Conditions, Pressure I
I I . - , < , , , . , , _ m
AP600 PASSIVE CONTAIMfENT COOUNG SYSTEM DI31cN llasts ANALYSIS hlODEL AND hl4RGIN AESIASMENT I
I I
I v u YVALUE YVALUE 1
1 0
0 0 SSAR Temp (Ver 1.0) 0 Case 3 Temp 300 I L 250
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Figure 14 AP600 LOCA Design Initial vs. Nominal Initial Conditions, Temperature u%pfdlO\l073w.wpf.1h-%2944 36
1 AP(M Passive CovralNMEvr Coou%G SvvrEM DEsicN B4sts ASSEtsis MoDEL AND M4kGth A%hEhSMENT i
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I ----30%
102% Power. WGOTHIC Ver. 1.2. Nominal Conditions Power. WGOTHIC Ver. 1.2. Nominal Conditions
102% Power. WGOTHic Ver, 1.0
- - - 3 0% Power. WGOTHic Ver. 1.0 I 60 e 'X N '
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Figure 15 AP600 Main Steamline Ilreak Nomina' Initial Conditions u:wamo7%puuc994 37
i AIW) Passn r Com1Nuf;NT Coouw SVFTEM DrSIGN B4El5 ANALYSTS MOD 11 AND MAQcIN AssmMENT I
I I
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102% Power. WG0THIC Ver 1.2. Nominal Conditions 30% Power. WGOTHIC Ver. 1 2. Nominal Conditions
- - - - 10 2 % Power. WG0THIC Ver 1.0
- -- 3 0% P o w e r . WGOTHiC Ver. 1.0 350 I L -
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IO api,03 PAnn t CosTriwir%T Conusc sistru DLsics IMsts A%4 Lists MoDrL mm MakGt% AwLssur%T j
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Conclusions I In this report, an overview of the entire process used for the AP600 containment analyses has been i
presented. This includes discussions on the test programs used to verify the passive safety systems of the AP6(K) containment as well as validate the heat and mass transfer correlations incorporated into the WGOTlilC code, Version 1.2. In addition, a comparison of WGOTlilC results to a variety of large I scale tests has been included.
The agreement between the large scale tests and the WGOTHIC Version 1.2 predictions demonstrates the acceptability of using WGOTillC to analyze AP600 containment. The inclusion of the subcooled enthalpy transport model and mixed convection improvements have resuhed in good agreement with the test data without requiring the anificial simulation of the effects of subcooling. He modifications I to the'WGOTlilC code have resulted in a tool that can be used to analyze the AP6(U containment.
I in order to assess the margin available in the current AP600 design, including model input assumptions, an additional set of cases are included which quantify the principal margins in the containment integrity analyses presented in the AP600 SSAR. He results of these cases graphically present the margin to the containment pressure resuhs preserNd in the SSAR and to the AP600 containment design limits. Reanalyzing the limiting uwainment integrity cases with the improved version of WGOTilIC has resuhed in the increase in margin to the design pressure of 45 psig from 8.09 margin to 18.99 margin.
I Finally, a set of runs for the loss of coolant and main steamline break cases are included where the input conservatisms are removed to the degree practical. These cases demonstrate the margin held by the conservative input assumptions that are made in accordance with accepted containment analysis methodologies. The results of these analyses indicate that the margin 1(. the design pressure increases to at least 269.
As demonstrated in this report, the AP600 passive containment cooling system design basis analyses presented in the AP600 SSAR clearly bound the results predicted with the revised WGOTHIC code and input models. in addition, the margin to design limits held by the conservative input model assumptions is demonstrated to be significant, prmiding additional margin to the AP600 containment design limits.
I I
I u:\apNurs10"%.wpf.lb-062094 39 l 1
r Ie AP600 PAssrVE CONTAINMENT COOUNG SYFTFM DESIGN BASIS AuEYsts MultL AND MARGIN ASSESSMENT j
1 I References I l. Document No. GWGLO21, " Westinghouse AP600 Standard Safety Analysis Report," Revision 1, 13 January 1994.
- 2. Presentation materials from March 17,1994 meeting on AP600 Passive Containment Cooling Design Basis Analyses, Westinghouse Letter NTD-NRC-94-4083,21 March 1994.
- 3. WCAP-13246, " Westinghouse-GOTIllC: A Computer Code for Analyses of 'Ihermal Hydraulic Transients For Nuclear Plant Containments and Auxiliary Buildings," July 1992.
- 4. Presentation materials from May 25,1994 meeting on AP600 Passive Containment Cooling l I System Analyses, Westinghouse Letter NTD-NRC-94-4152,31 May 1994.
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