ML20062F629
| ML20062F629 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 12/15/1978 |
| From: | Roe L TOLEDO EDISON CO. |
| To: | Baer R Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7812200166 | |
| Download: ML20062F629 (2) | |
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TDLEDO EDISON LOWELL E. ROE Docket Nos. 50-500 and 50-501 v ** *=' ai Fec* tees Deveiopment (4191 259-5242 Serial No. 2-138 December 15, 1978 o
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s s Director of Nuclear Reactor Regulation
[ P Attention:
Mr. Robert L. Baer, Chief
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Light Water Reactors Branch No. 2
--E y Division of Project Management M
U.S. Nuclear Regulatory Commission
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Washington, D.C.
20555 e
Dear Mr. Baer:
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This letter is in response to your letter dated June 12, 1978 concerning 1
the capability for cold shutdown of Davis-Besse Nuclear Power Station Unit Nos. 2 and 3.
As requested, this letter contains the commitments by the Applicants addressing the NRC cold shutdown design requirements detailed in the above letter. It also reflects discussions and clarifica-d tions of NRC criteria by your Licensing Project Manager and NRC Staff i'
reviewers.
Additional seismic Category I, safety grade steam generator vent valves
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(one additional valve per steam generator) will be incorporated into the design of the Davis-Besse Nuclear Power Station Unit Nos. 2 and 3.
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~ These additional valves are being provided to ensure the capability of cooling down the Davis-Besse Unit Nos. 2 and 3, assuming the most limiting single failure with only off-site or on-site power available and a safe shutdown earthquake. Operation of these valves will be by local manual valve operators. A test of the local control for these modulating aW p'ine vent valves will be conducted prior to unit operation to demonstrate that the units can be cooled in a controlled manner, and i
that the valves can be operated safely and effectively, a
The addition of these modulating atmospheric vent valves to the Davis-Besse Nuclear Power Station Unit Nos. 2 and 3 is intended to provide the capability, assuming the most limiting single failure with only on-site or off-site power available and a safe shutdown earthquake, to cooldown to the decay heat. removal system cut-in conditions.
78122001%
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THE TOLEDO EDISON COMPANY EDISON PLAZA 300 MADISON AVENUE MEDO. CHIO 43652 A
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. -:p The Davis-Besse Unit Nos. 2 and 3 design will be analyzed to confirm the 4
capability to depressurize, borate, and cooldown to the decay heat removal system cut-in conditions using only safety grade equipment, and Z.
with only on-site or off-site power available. This analysis will also confirm that sufficient boration capability exists to maintain the q
reactor coolant system at 1% ok/k subcritical margin. When considering boration requirements, the highest worth control rod is assumed to be at gf the fully withdrawn position. The analysis will also determine the time required to attain the decay heat removal system cut-in conditions with the present design as modified by this commitment letter. Should the analysis show that cooldown cannot be accomplished in approximately 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. a cost-benefit analysis will be performed to determine the impacts i
of ada;tional hardware changes required to attain approximately 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> cooldown. The results of the cost-benefit analysis will be presented to the NRC for their review.
Davis-Besse Unit Nos. 2 and 3 will reference a planrad first-of-a-kind prototype steady state natural circulation qualification test to provide g
assurance of adequate boron mixing and natural circulation.
Specific procedures for cooling down using natural circulation will be provided at the Operating License review stage.
f-A saismic Category I auxiliary feedwater supply is provided which will f
permit cooldown to the DHR cut-in conditions, assuming the most limiting r.',
single failure.
Q With these additional commitments concerning the cold shutdown issue, it E
is our understanding that Toledo Edison has satisfied the requirements on this issue required to allow the Safety Evaluation Report Supplement u
to be written. Should the NRC modify its position with regard to cold shutdown, Toledo Edison reserves the right to modify these commitments
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accordingly.
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h The only remaining issue is the quality classification of the main steam non-return valves and the main feedwater control valves. We anticipate forwarding further information to support our present design of these valves in the near future.
Yours very truly, db d/2-3 6I i,
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