ML20215N410
| ML20215N410 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood, 05000000 |
| Issue date: | 10/23/1986 |
| From: | Hunsader S COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 2303K, GL-86-10, NUDOCS 8611050375 | |
| Download: ML20215N410 (2) | |
Text
...
Commonwealth Edison
. - 72 West Adtms Street Chicago, Illinois Address Reply to: Post Office Box 767
\\
Chicago, Illinois 60690 - 0767 October 23, 1986 d
m c
Mr. Harold R. Denton, Director
>e Office of Nuclear Reactor Regulation
~
U.S. Nuclear Regulatory Commission Washington, DC. 20555
Subject:
Byron Station Unite 1 & 2 Braidwood Station Units 1 and 2.
Review of High-Low Pressure Interface Valves'on Excess Letdown Lines
Dear Mr' Denton:
The purpose of this letter is to provide the results of an l
analysis concerning the spurious operation of the valves that form the High-Low pressure interface on the' Excess Letdown lines.
Generic Letter 86-10 requires the study of spurious operation of all high-low pressure interface points in the plant.
Completion of this analysis completes the review of valves not previously analyzed.
Attachment A provides the scenario of the valve arrangement for the excess letdown flow path.
From this valve arrangement, it can be seen that at least four spurious valve. failures would have to occur simultaneously in order to create an uncontrolled coolant loss to the Reactor Coolant Drain Tank (RCDT).
Due to the number of valves involved, a fire induced event of this type is not postulated.
Should you have any questions concerning this matter, please contact this office.
One signed original and fifteen copies of this letter and the enclosures are provided for your review.
Very truly yours, m/L S.
C. Hunsader Nuclear Licensing Administrator
/klj encl.
cc:
J. Stevens L. Olshan b
2303K b
0611050375 861023 PDR ADOCK 05000454 P
~s ATTACHMENT A Summary of Excess Letdown Flow Path The excess letdown flow path is as follows (refer to Byron /Braidwood FSAR Figure 5.1-1, Sheets 1 through 4 and Figure 9.3-4, Sheet 3):
Reactor' coolant enters the excess letdown line through the reactor coolant loop drain headers.
The four hot leg drain headers, one on each RC loop, are isolated by normally closed manual valves RC8040A, B, C,
and D.
The four cold leg drain headers are isolated by normally closed air-operated valves MC8037A, B, C,
and D.
Excess letdown flow then passes through either air-operated valve CV8153A or CV8153B (note that although Figure 9.3-4, sheet 3, shows CV8153A in the open position, both of these valves are normally closed).
Flow then passes through normally closed flow control valve CVHCV123 (maximum flow rate = 25 gpm) and on to divert valve CV8143.
2303K
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