ML20137Y693
| ML20137Y693 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 12/05/1985 |
| From: | Thompson H Office of Nuclear Reactor Regulation |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20137Y697 | List: |
| References | |
| NUDOCS 8512110119 | |
| Download: ML20137Y693 (1) | |
Text
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NOTE TO: Harold R. Denton, Director, NRR-i FROM:
Hugh L. Thompson, Jr, Director e
l Division of PWR Licensing-A, NRR a
i
SUBJECT:
CORE MELT FREQUENCY ESTIMATE FOR BYRON 1 In his note to you dated December 2,1985, Themis Speis stated that recent
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review of a Byron PRA-type study indicates the Byron I core melt frequency is presently about 1.2x10-3/yr. The staff and Brookhaven National Laboratory (BNL) met with the Commonwealth Edison (CECO) and Westinghouse on December 3 1985, and there were several conference calls on the following day, to discuss this matter. As a result, the following efforts are currently underway:
1.
BNL reanalysis - It was learned that the modeling of the cooling tower fans was not in accordance with operating reality.. This modification, plus several others, are being made and BNL is re-running the model to compute a new core melt frequency. The results should be available by Friday, December 6.
I 2.
Induced seal LOCA - Westinghouse and BNL assumed that the
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probability for an induced reactor coolant pump seal LOCA, given loss of seal cooling, is 0.5.
Westinghouse now claims that recent
, testing done in France should justify a lower probability.
3.
Interim owration - The Unit 2 essential service water (ESW) pumps will not,>e fully operable for several months. CECO is investigating various modes of operating in the interim until the Unit 2 pumps are fully operable. These include leaving both Unit 1 pumps running continuously, not allowing maintenance of either pump, or making a Unit 2 pump available, though not fully operational, to pump water if the emergency need arises. BNL is assessing the effect of these various options on the core melt frequency.
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All these issues will be discussed at a meeting with CECO and Westinghouse scheduled for Friday, December 60 Byron
- n Wednesday, December 11,' unless we issue an(order to not restart.is schedule to restart
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currently meets all our rules and regulations. I will make a reconnendation regarding. restart prior to December 11, 1985.
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Hu L. Thompson J.,
irector -
Di ion of PWR Li ens ng-A, NRR D
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