ML20210U286

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Forwards Description of Proposed Method to Provide Electrical Isolation of P-8 Signal,Per NRC Request.Method Involves Installation of Intervening Relay to Perform Electrical Isolation Function for ATWS Mitigation Sys
ML20210U286
Person / Time
Site: Zion  File:ZionSolutions icon.png
Issue date: 02/06/1987
From: Leblond P
COMMONWEALTH EDISON CO.
To: Harold Denton
Office of Nuclear Reactor Regulation
References
2698K, NUDOCS 8702180434
Download: ML20210U286 (3)


Text

,_______

l - Comm nw::cith Edison 1

V One First National Plaza, Chicago, Illinois Address Reply to: Post Office Box 767 Chicago, Illinois 60690 - 0767 February 6, 1987 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

Zion Nuclear Power Station Units 1 and 2 ATWS Protection - 10 CFR 50.62 NRC Docket Nos. 50-295 and 50-304 References (a): June 5, 1986 letter from P.C. LeBlond to H.R. Denton.

(b): January 9, 1987 letter from P.C. LeBlond to H.R. Denton.

Dear Mr. Denton:

Commonwealth Edison Company has provided the NRC Staff with a description of the proposed ATWS Mitigation System for Zion Station in References (a) and (b). Subsequent conversations with Mr. J.A. Norris and others of your staff have identified the need for additional information regarding the proposed electrical isolation of the P-8 signal.

A description of the proposed method to provide electrical isolation of the P-8 signal is enclosed with this letter. This method involves the installation of an intervening relay to perform the electrical isolation function for the ATWS Mitigation System.

If any further questions arise regarding this matter, please contact this office.

Very truly yours, h

P. C. LeBlond Nuclear Licensing Administrator 1m Enclosure cc: Zion Resident Inspector J. A. Norris - NRR '

h ii 2698K 8702180434 870206 S PDR ADOCK 0500 P

J -' Subiect isolation of P8 0utouts Generic Letter 85-06, in part, requires that safety related circuits be isolated from non-Safety related circuits. The use of the "P8" output brings into cuestion the method used to isolate the ATWS ~P8" signal from the .

R.eactor Protection System (RPS)'P8' signal. Isolation of the RPS and ATWS system will be accomplished by the use of an isolating relay. To begin, tne train 'A" "P8" relays (P8/XA, P8/YA), located in the Reactor Protection Cabinet, are energized by the following logic:

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I To prov10e the recu1 red 1 Solation a new isolating relay (PBXY/ A), located

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at the ATWS cabinet, will be operated by the ~P8 relay contacts as shown.

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  • hE5L Ax $ "TC; RELAYS ARE WESI NSFD s i This 05/AX relay, locatec in the ATwS caDinet, w111 provide the contacts required f ar the "P8" permissives in the ATW5 logic. Separation between ATW5 anc the plant Reactor Protect 1cn Sistem 15 therefore providet by the

?SXY/A relay Th15 relay provice5 suf ficient 15018t;on to prevent any f aiiUre of the ATW5 system from af feClinQ the R?S Ic91c

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