ML20041C347

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Responds to NRC 820127 Request for Addl Info Re Mods to Combustible Gas Control Sys.Each Pair of Containment Isolation Valves Is Controlled by Class IE Keylocked Switches Located in Class IE Control Panel
ML20041C347
Person / Time
Site: Pilgrim
Issue date: 02/23/1982
From: Deacon W
BOSTON EDISON CO.
To: Vassallo D
Office of Nuclear Reactor Regulation
References
82-60, NUDOCS 8203010197
Download: ML20041C347 (2)


Text

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BOSTON EDISON COMPANY

?l moo nonevo= st est Boston. M ASSACMum(TTB D2199 l,

February 23, 1982 BECo Ltr. #82-60 to to Mr. Domenic B. Vassallo, Chief Operating Reactors Branch #2 GECEWED 1 Division of Licensing Office of Nuclear Reactor Regulation ' MAR 011982> Es 4 - U.S. Nuclear Regulatory Commission "

W unarmame s Washi ngton, D. C. 20555 s pa g License No. DPR-35 6 Docket No. 50-293 Response to Request for Additional Information Concerning Modifications to the Combustible Gas Control System (CGCS)

Reference (a): NRC letter to Soston Edison dated January 27,1982 (BECo. Ltr. #1.82.022)

Dear Sir:

We submit the following in response to the question contained in the enclosure of the above reference.

Ea-h pair of series CGCS containment isolation valves are controlled by Class IE keylocked control switches located in a Class IE control panel. The valves are closed during normal operation, receive no automatic initiation signal, and re-quire a key operation to open.

Wiring within the control panel is arranged so that the containment isolation valve circuits are bundled separately from all non-safety related control cir-cuits and all instrument circuits. The control panel is located in the PNPS main control room and is therefore not subject to harsh environments and/or hazards that could damage the panel and/or internal wiring.

,' Cables are routed from the control panel to the area of the solenoid operated

isolation valves through a common raceway system used exclusively for cables from the same safety train of CGCS containment isolation valves. Damage to this conduit system causing the cables to open or short (short beina the most likely)'will result in the fail safe isolation valves remaining closed.

Whe'n the solenoid valves are deenergized, the valve position circuits are the only source of power in the subject raceway system'. The only ungrounded (hot) leads in'tais circuit first pass through position indicating lights before entering the reacevray system. If there were a cable failure within the conduit system, and if cables feeding two series valves are damaged, the power source available would be insuffici'ent to energize either solenoid valve.

8203010197 820223 '

' 0 fDR ADOCK 05000 p

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e a 803 TON EDISON COMPANY Mr. Domenic B. Vassallo, Chief Februa ry 23, 1982 Page 2 The position of each vent and purge valve is verified and recorded daily by the control room operator and the key lock control switches are annunciated to alarm when positioned to open a valve. Therefore, control room personnel are cognizant of valve position at all times.

We trust this information is responsive to your needs; however, should you have any questions, please call .

Very truly yours ,

?d c&t_

W. H. Deacon Acting Manager Nuclear Operations Support