ML19242A132
| ML19242A132 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 06/04/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19242A130 | List: |
| References | |
| NUDOCS 7907310336 | |
| Download: ML19242A132 (2) | |
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Safety Evaluation Report Point Beach, Units I and 2
_ Docket Nos. 50-266/301
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Introduction By letter dated March 20,1973 (Reference 1) Wisconsin Electric Power Company (the licensee) submitted the Emergency Core Cooling System (ECCS) reanalysis for the Point Beach Nuclear Plant, Units 1 and 2.
This reanalysis was perfomed in response to tha Order for Modification cT 1.icense issued on April 28, 1978 (Ref erence 2) for Units 1 and 2 as a result of the discovery of an error in tne Zr-witer reaction model in the evaluation model computer codes used in the LOCA anil sis (Reference 3). The February 1978 version of the ECCS aaluation model (R3f aren;e 4) was used in the rea.ialysis.
It included the correction of the error and other approved 'nodel.;hanges.
The re nalysis also included input assumption of 10 percent of steam generator tubes plugged and was perfomed wi th the total peaking factor, F, of 2.32.
Q Ev al Jatio n On Mtrch 21, 1978 an error as discovered in the Westinghouse ECCS evaluation model.
The error involved the calculated heat generation resulting from the Zr-wate: reaction and affected the calculated cledding temperatures after a LOCA.
Following discovery of this error we promptly determined that no immediate operating change was required to assure safe ooeration of the plants a f fected, but that reanalysis und reevaluation were needed.
After the sub-sequent discussions with Westinghouse and with the licenset we issued an Crder for Mudification of License for the Point 9each Nuclear Plant, Units 1 and 2 (Reference 5).
The Order dit "cted that the licensee submits as soon as possible a re-evaluation of ECCS performance calculated in accordance with a revised and approved Westinghouse ECCS evaluation n.Sdel.
In response to this request the licensee submitted the present analysis. The analysis was perfomed with the NRC apnroved February 1973 version r f the Westinghouse Evaluation Model (Reference 4) which,in addition to including toe correction of the Zr-v:ater reaction error and 0.-verai cc a maintenance and analytical improvements, cor,tained the following cnanges: rodification of the input to the containment code, modified accumulator model, steam dynamic cooling and an improved 15x15 FLECHT heat transfer correlation.
The submitted analyses was performed with the total peaking factor, Fg, of 2.32 and assuming 10 percent of steam generator t"bes pl ugge d.
Although the subnitted analysis was limited to a single break, the DEJLG break with C =0.4, the licensee referenced a generic two-loop LOCA D
spectrum of DECLG breaks with a range of discharge coefficients of from 0.4 to 1.0 (Reference 1).
These analys m demonstrated that the limiting break was independent of che version of the Westinghouse ECCS evaluation model used.
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. The consideration of upper plenum injection (UPI) effect was not included in the However, it was previously demonstrated (Reference 6) that present analysis.
this ef fect would cause a 60 F increase in peak clad temperature (PCT).
In order to use the present ECCS evaluation model to analyze a postulated LOCA in the Point Beach plant and remain in compliance with 10 CFR 50.46, a limit of 2140 F on calculated peak clad temperature must be observed.
T:
results of the analysis are provided below:
e Limiting Break:
DECLG with CD=0.4 Steam generator Tubes Plugged:
10 percent Peak Clad Temperature:
2007 F Local Zr-Water Reaction:
3.6%
Total Zr-Water Reaction:
<0.3%
All the values reported are bclow Sw: limits of 10 CFR 50.46.
l Conf usions Based on the review of the submitted documents we conclude from the results of the ECCS reanalysis pe ' formed with the previously approved February 1978 version of the Westino'.ouse evaluation model, that operation of Point Beach Units 1 and 2 at a ;eas ;g factor limit of 2.32 will be in conformance with the 10 CFR 50.46 criteria.
We consider the ECCS analysis acceptable for allowing the plant to be operated with up to a maximum of 10 percent of steam generator tubes plugged.
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