ML20210Q732
| ML20210Q732 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 09/25/1986 |
| From: | Miosi A COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 2158K, NUDOCS 8610070015 | |
| Download: ML20210Q732 (2) | |
Text
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N, Commonwealth Edison Z, f 72 West Adams Street, Chicago. Illinois Address Reply to: Post Office Box 767 sV Chicago, Illinois 60690 0767 September 25, 1986 Mr. Harold R. Denton U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulatory Washington, DC. 20555
Subject:
Braidwood Station Units 1 & 2 Technical Specification NRC Docket Nos. 50-456 and 50-457 References (a):
February 20, 1985 T.R. Tramm letter to H.R. Denton (b):
April 8, 1985 T.R. Tramm letter to H.R. Denton
Dear Mr. Denton:
This letter provides confirmation of actions which will be taken to implement the Technical Specification requirements for testing of the Braidwood reactor protection system instrumentation.
This is the same commitment that was made for Byron Station Units 1 and 2 as provided in references (a) and (b) which was in support of changing the analog channel operational surveillance tests for the reactor protection system instrumentation from monthly to quarterly intervals.
The commitments are as follows:
1.
Instrument drift will be monitored for the instruments which are calibrated quarterly for a period of about one year.
This information will be used to verify the adequacy of the drift allowance in the statistical setpoint stu,dy.
2.
Failures of instruments subject to quarterly analog channel operational testing will be reviewed during the first year for possible common mode failures.
The plant procedure for review of deviation reports reflects this commitment.
Completion of deviation records resulting from quarterly analog channel testing will require an evaluation of the failure to determine if that failure could be a common cause failure.
The procedure requires testing of the other channels of like function if the failure is l
determined to be a plausible common cause failure.
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O g For the purposes of this evaluation a common cause failure will be defined as a failure which indicates a systematic deficiency in the design, fabrication, testing, or operation of a system which would be likely to result in the simultaneous failure of redundant systems to fulfill their intended safety function.
Instrument drift and power failure to a single channel are understood to be examples of failures which are not common cause failures.
3.
The quarterly analog channel tests on redundant instruments will be performed throughout the quarter to minimize the possibility of undetected common mode failures.
Redundant channels will not be tested on the same day by the same instrument mechanics using the same test instruments.
Pending resolution of the Westinghouse Owner's Group Subcommittee responsible for Reactor Protection System surveillance intervals, our commirment may need to be revised.
You will be kept informed should this occur.
Should you have any questions concerning this matter please contact this office.
One signed original and fifteen copies of this letter are provided for your review.
Very truly yours, A. D.
iosi Nuclear Licensing Administrator cc:
J.
Stevens 2158K
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