ML17252B009
| ML17252B009 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 12/08/1972 |
| From: | Worden W Commonwealth Edison Co |
| To: | Anthony Giambusso US Atomic Energy Commission (AEC) |
| References | |
| Download: ML17252B009 (3) | |
Text
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Commonwealth Edison Company 7 2. W E S T A D A M S S T R E E T * *C H I CA G 0,
I L L I N 0 I S X 7 6 7
- C H f C A G.0, I l l I N 0 I S 6 0 6 9 0 Mr. A.
Deputy Director for Reactor Projects Directorate of Licensing U. s. Atomic Energy Commission Washington, D. c..
20545 Dresden Nuclear Power Station R. R. #1 Morris, Illinois 60450 December 8, 1972
SUBJECT:
LICENSE DPR-25 1 DRESDEN NUCLEAR POWER STATION, UNIT #3, SECTION 6. 6. C. l OF THE TECHNICAL SPECIFICATIONS.
Dear Mr. Giambusso:
This is to report a condition relating.~o the operation of the station, when during surveillance testing, main steam isolation
- valve (MSIV) 3-203-lB was found to have a closure time of 2~.l seconds,
- which is outside the limits specified in the Technical Specifications.
PROBLEM AND INVESTIGATION At 0530, November 11, 1972, with the reactor at a power level of 1113 MWt, quarterly MSIV timing surveillance was being conducted.
During these tests, it was discovered that MSIV 3-203-lB had a closure time of 2.1 seconds, faster than the 3 second to 5 second limits specified in the Technical Specifications (Table 3.7.1).
Both valves in the "B" steam line were promptly closed in accordance with section 3.7.2 of the Technical Specifications, and maintained in that condition until a subsequent shutdown.
The MSIV's on the other three steam lines had closutte times within the 3. second to 5 second limits.
The limits specified on fast closure of the MSIV's are intended tp prevent ~ rapid reactor_.isolation, and subsequent rapid reactor pressurization and resulting relief valve operation.
Closure of one MSIV in 2 seconds instead of 3 seconds does not significantly increase the pressure spike or the potential for relief valve operation.
Additionally, any pressure transient from the fast closure of one MSIV would be "softened" by the slower MSIV closure on the other three lines.
Consequently, it is concluded that the fast closure of the 3-203-lB MSIV was of no safety significance.
- December 8, 1972 CORRECTIVE ACTION On November 19, 1972, during a subsequent plant shutdown, MSIV 3-203-lB was inspected and* found to have a slight oil leak in a fitting (see attached figure). *This ~itting is in the valve's hydraulic speed control system.* On loss of o"il, the speed control system causes the valve to close faster.
The fitting probaoly leaked due to insufficient tighten-ing during installation. *The slight leakage eventual~y resulted in sufficient loss of oil to affect closure time.
The fitting was tightened, oil added, and the valve retimed.
The valve operated satisfactorily and the 2 valves on "B" steam line were opened for startup.
This problem is considered a one time occurrence and no further action is planned at this time.
WPW:do Sincerely, JJ././J~
r W. P. Worden Superintendent
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