ML20138G421

Advises That NRC Has No Objection to Plant Resuming Power Operation,Based on Discussion at 851203 & 06 Meetings & Util Re Essential Svc Water Sys.Need for Tech Spec Under Review

ML20138G421
Person / Time
Site:	Byron
Issue date:	12/10/1985
From:	Thompson H Office of Nuclear Reactor Regulation
To:	Harold Denton Office of Nuclear Reactor Regulation
Shared Package
ML20137Y697	List: ML20137Y693 ML20138G421 ML20138G429
References
NUDOCS 8512160320
Download: ML20138G421 (2)

Text

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e as ase oq'o g UNITED STATES

! g NUCLEAR REGULATORY COMMISSION

, s l WASHINGTON.,D. C. 20555

• +.....+' SEC 101985 MEMORANDUM FOR: Harold R. Denton, Director, NRR eqe4 FROM: Hugh L. Thompson, Jr., Director Division of PWR Licensing-A, NRR

SUBJECT:

CORE MELT FREQUENCY ESTIMATE FOR

-SYRON UNIT =1 The concerns which have arisen regarding the calculated contribution of the Byron Unit 1 essential service water system (ESWS) to the estimated core melt frequency during the period before operation of Byron Unit 2 were discussed at meetings on December 3 and 6,1985. The results of the December 3, 1985 meeting with Brookhaven National Laboratory (BNL), Commonwealth Edison Company (CECO), and Westinghouse Q) were previously reported to you, in my December 5, 1985 memorandum (Enclosure 1).

A new calculation of core melt frequency (CHF) was made taking the following into account: 1) the addition of a third ESWS pump; 2) use of the revised success criteria for the cooling tower fans; and 3) use of a revised value for ESW pump failure rate (NRC/BNL's value is greater than CECO _/W's_galue).

These revil gd calculations resulted in a new CMF value of 1.3X10 for NRC/BNL and 6-8X10 for Ceco /W. No credit was taken in the revised calculations for any potential enhancement in the value for probability of an induced reactor coolant pump seal LOCA (this issue will be discussed during a meeting with the W Owners Group on December 16 and 17, 1985).

By letter dated December 6, 1985 (Enclosure 2), Ceco committed to enhancing

, the reliability of the Byron Unit 1 ESWS by making a Unit 2 ESW pump available during operation of Byron Unit 1. The Unit 2 ESW pumps are in their final stages of preoperational testing and can be connected to the Unit 1 ESWS through existing cross-tie piping. The Administrative Controls governing the availability of a Unit 2 ESW pump until Byron Unit 2 is operational are included in Enclosure 2.

Byron Unit 1 is presently shutdown. The Operating Procedures have been revised to include instructions for control room operators to cross-tie the Unit 2 ESWS to the Unit 1 ESWS in the event both Unit 1 ESWS pumps become inoperable. Initial training on these procedures will be provided to control room operators involved with the startup of Byron Unit 1. Based on the above, the staff has no objection to Byron Unit 1 resuming power operation. Startup is expected to occur on Wednesday, December 11, 1985. We will address the need for any technical specification as part of the ongoing review. i

_ l 8512160320 851210

• PDR ADOCK 05000454 P PDR

I l This issue is still being investigated for any potential application to other W plants.

Sincerely, f.

L. Thompson r. , ector Hg Di sion of PWR icen -A

Enclosure:

1. Memo from Thompson to Denton dated 12/5/85

2. Letter from CECO to Denton dated 12/6/85 cc: J. Keppler

, _._. F. Miraglia T. Spets .

R. Bernero W. Russell e

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