ML20040H233
| ML20040H233 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 05/30/1975 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18023A006 | List: |
| References | |
| NUDOCS 8202170477 | |
| Download: ML20040H233 (6) | |
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ENCLOSURE
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TOPICAL REPORT EVALUATION j.
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1 Report Number: WCAP-8471 (Proprietary), and WCAP-8472 (Non-Proprietary) 1 Report
Title:
The Westinghouse ECCS Evaluation Model: Supplementary Information I
j Report Date:
January 1975
. Originating Organization:
Westinghouse Electric Corporation.
Reviewed By:
Reactor Systems Branch, Office of Nuclear Reactor Regulation
SUMMARY
OF TOPICAL REPORT The subject reports provide the documentation of modifications to the original version of the Westinghouse ECCS evaluat' ion model which were required by the NRC staf f (References 19 & 20) to bring the model into conformance with Appendix K to 10 CFR Part 50 These modifications include:
1 - Deletion of rod-to-rod ' radiation dur.ing blowdown.
2 - Revis, ion of injection section pressure drop.
'. 3 - Deletion of 10% clad strain burst criterion.
4 - Inclusion of hot wall time delay.
5 - Modification of the steam cooling model.
The revised version of the Westinghouse ECCS evaluation model, identified as the December 25, 1974 version, was approved by the staf f when the above modifications were made to the original model, prior to the submittal of i
the documentation of the modifications in WCAP-8471.
In mid-January 1975, additional refinements to the approved December 25, 1975 evaluation model were identified as necessary to provide a better representation of the low pressure FLECHT data for reflood heat transfer for flooding rates less than one inch per second (steam cooling).
The staff held a series of meetings with Westinghouse to resolve the issue generically as it related to the evaluation model for low containment pressure plant designs; the most recent of these meetings was held
.on March 17, 1975. The proposed refinements to the Westinghouse model have been reviewed since January in preliminary form by the NRC staff.
We concluded following the March 17, 1975 meeting, that once the proposed refinements were implemented into the December 25, 1974 version of the model, the further revised (i.e., March 15, 1975) version of the evaluation model would be acceptable. Included in the subject topical reports are a description of the proposed steam cooling model refinements to the December 25, 1974 model and a description of the manner in which they were implemented into the March 15, 1975 version of the codes.
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The stcan cooling modal wc3 rafined to e==ssrvativsly reprassnt the Icv pressure TLECHT data for reflood rates less than one inch per second.
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Westinghouse modified the steam cooling heat transfer correlation by
' adjusting the fitting parameters to more closely agree with the FLECHT date and by introducing a pressure dependence to maintain agreement wirS the FLECHT data at low core pressures.
In addition to the modifications required by the staf f. Westinghouse submitted supplemental information including responses to questions raised by the staff in the course of reviewing the Westinghouse ECCS evaluation model, and documentation of minor code modifications which had no significant e f fect on computational results.
The following supplemental information, re, quested by the staf f, was included as appendices to WCAP-8471:
1 - An input description for the WFLASH computer code.
2 - The determination of flow blockage during a loss of coolant accident.
3 - The ef fects of nitrogen gas on reflood rates.
4 - A comparison of 17 x 17 reflooding data and the 17 x 17 FLECHT design model.
5 - A summary of user options for the Westinghouse ECCS evaluation model codes.
6 - The steam cooling model modifications included in the March 15 1975' version of the Westinghouse evaluation model.
As noted in WCAP-8471, specific code modifications have been implemented which af fected SATAN-VI, WREFLOOD, LOCTA-IV, WFLASH, and LOTIC.
Although the majority of the information found in the original reports, References 1 through 18, is still applicable to the approved Westinghouse ECCS evaluation model, some changes were required in the following referenced reports:
1 - WCAP-8200, Rev. 2 (Proprietary) and WCAP-8261, Rev. 1 (Non-Proprietary) entitled, "WFLASH - A, Fortran IV Computer Program for Simulation of Transients in a Multi-Loop PWR".
2 - WCAP-8301 (Proprietary) and WCAP-8305 (Non-Proprietary) entitled, "LOCTA-IV Program: Loss-of-Coolant Transient Analysis".
3 - WCAP-8170 (Proprietary) and WCAP-8171 (Non-Proprietary) entitled, " Calculational Model for Core Reflooding Af ter a LOCA (WREFLOOD Code)".
4 - WCAP-8339 (Non-Proprietary) entitled, " Westinghouse ECCS Evaluation Model - Summary".
For each modification Westinghouse identified the purpose, method of implementation, and a corrected identification name and date.
.In addition to the summary description of each model change, the results of applicable sensitivity studies and a complete description of the model were included.
Westinghouse, presented the results of a sensitivity study comparing the the December 25, 1974 and March 15, 1b75 versions of the ECCS evaluation 6odel.which evaluated the impact of the steam cooling model refinement
'u2. present and future analyses. Westinghouse concluded that, for analyses in which the peak clad temperature occurred at flooding rates greater than 1.0 inches per second and the difference in peak clad temperatures determined. by the two models was less than 20*F, the December 25, 1974 and March 15, 1975 versions of the evaluation model would be equivalent and either version of the model would be suitable for evaluating ECCS perfor-mance. For analyses in which the peak clad temperature occurs in the steam cooling mode (reflood rate less than 1.0 inches per second) and for all future ECCS analyses, only the March 15, 1975 version of the model would be applicable.
STAFF EVALUATION ne model modifications required by the NRC staff have been satisfactorily implemented into the Westinghouse ECCS evaluation model and Westinghouse has provided the supplemental documentation as required by Appendix K to 10 CFR Part 50 De NRC staff evaluation.of the comparison of plant analyses performed with both the December 25, 1974 and March 15, 1975 versions of the Westinghouse evaluation model concluded that there was a threshold flooding rate at the time of peak clad temperature turnaround above which the two versions of the the model were equivalent (i.e., less than 20 *F difference in peak clad temperature). A threshold flooding rate of 1.1 inches per second vaa established by the staff (compared to the value of 1.0 inches per second proposed by Westinghouse) as the criterion for evaluating the ECCS performance analyses submitted using,the December 25, 1974 version of the evaluation model.
STAFF POSITION Re NRC staf f has completed its evaluation of the subject topical reports in conjunction with its review of the Westinghouse ECCS evaluation model.
The
'staf f concluded that:
- 1) The subject topical report, WCAP-8471, is an accepted topical report when referenced in licensing applications as part of l.
the Westinghouse ECCS evaluation model. We find WCAP-8472 to be an acceptable non-proprietary version of WCAP-8471.
- 2) The December 25, 1974 version of the Westinghouse evaluation
- model, i.e., the version without the modifications described in WCAP-8471 is acceptable for previously analyzed plant s for which the peak clad temperature turnaround was identified prior to the reflood rate decreasing below 1.1 inches per second or for which the reflood rate was identified to remain above 1.0 inch per second; conditions for which the December 25, 1974 and March 15, 1975 versions would be equivalent.
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- 3) The March 15, 1975 version of the Westinghouse evaluation model is an acceptable model to be used for all previously analyzed plants for which the peak clad temperature turnaround was identified to occur af ter the reflood rate decreased below 1.1 inches per second, and for which steam cooling conditions (reflood rate less than 1 inch per second) exist prior to the time of peak clad temperature turnaround. The March 15,1975 version will be used for all future plant analyses.
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REFERENCES
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1.
WCAP-8200, Rev. 2, "WFLASH - A Fortran IV Computer Program fcr Simulation of Transients in a Multi-Loop PWR," (Proprietary), June 1974.
2.
WCAP-8261, Rev.1, "WFLASH - A Fort ran IV Computer Program for Simulation of Transients in a Multi-Loop PWR," (Non-proprietary), July 1974.
3.
" Effects of Fuel Densification Power Spikes on Clad Thermal Transients," (Non-proprietary), July 1974.
4.
WCAP-8354 "Long-Tern Ice Condenser containment Code - LOTIC code,"
(Proprietary), July 1974.
5.
WCAP-8355 "Lons-Tern Ice condenser Containment Code - LOTIC code,"
(Non-proprietary), July 1974.
6.
" Westinghouse ECCS - Plant Sensitivity Studies " (Proprietary),
July 1974.
7.
" Westinghouse ECCS - Plant Sensitivity Studies," (Non-l proprietary), July 1974.
i 8.
" Containment Pressure Analysis Code (COCO)," (Proprietary),
July 1974.
9.
" Containment Pressure Analysis Code (C0CO)," (Non-proprietary),
July 1974.
- 10. WCAP-8302
" SATAN-VI Program: Comprehensive Space-Time Dependent.
Analysis of Loss-of-Coolant," (Proprietary), June 1974.
- 11. WCAP-8306
" SATAN-VI Program:
Compr.ehensive Space-Time Dependent Analysis of Loss-of-Coolant," (Non proprietary), June 1974.
12.
" Calculational Model for Core Reflooding After a LOCA (WREFLOOD Code)," (Proprietary),1 June 1974.
l 13.
" Calculational Model' for Core Reflooding After a LOCA (WREFLOOD Code)," (Non proprietary), June 1974.
(Proprietary), June 1974.
15.
WCAP-8305 "LOCTA-IV Program:
Loss-of-Coolant Transient Analysis,"
(Non-proprietary), June 1974.
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l f 6.
'.' Westinghouse ECCS Evaluation Model - Summary " (Non-
- t... proprietary), June 1974.
- 17. WCAP-8341
" Westinghouse ECCS Evaluation Model Sensitivity Studies "
(Proprietary), July 1974.
j 18.
" Westinghouse ECCS Evaluation Model Sensitivity Studies,"
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(Non-proprietary), July 1974.
19.
" Status Report by the Directorate of Licensing in the Matter of Westinghouse Electric Company ECCS Evaluation Model Conformance to 10 CFR 50, Appendix K," Cetober 15,197{.
j 20
" Supplement to the Status Report by the Directorate of Licensing in the Matter of Westinghouse Electric Company ECCS Evaluation Model Conformance to 10 CFR 50, Appendix K," November 13, 1974.
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