ML20084D687
| ML20084D687 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 03/23/1973 |
| From: | Worden W COMMONWEALTH EDISON CO. |
| To: | Anthony Giambusso US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| 2025, 218-73, NUDOCS 8304120209 | |
| Download: ML20084D687 (2) | |
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. 'k 50-237 Commonwealth Edison Company 72 WEST ADAMS STREET
- C H I C A G O.
ILLINOIS AWr.ss f.pir to:
POST Of RICE SOX 747
- C H I C A G O, IL LIN OIS 40490 Dresden Nuclear Power Station ri 4 R. R. #1
'U}F Morris, Illinois 60450 N.
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WFW Ltr. #218-73 March 23, 1973 A
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'l f W Mr. A. Giambusso
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Deputy Director for Reactor Projects 1
Directorate of Licensing O/
[/7 U. S. Atomic Energy Cer.J.ssion 1
Washington, D.C.
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SUBJECT:
LICDISE DPR-10 DRESDEN NUCIEAR PO'.TER STATION, UNIT #2, v
SECTION 6.6 e.1 of THE TECFNICAL SPECIPICATIONS, N
Dear Mr. Giambusse:
This is to report a conditien relatine to the operation of the unit, in which, en February 22, 1973, during valve operability checks for the r.cnthly unit 2/3 diesel generater outage, low pressu e coolant injection (LPCI) valve MO-2-1501-32A was cycled closed, but tripped im=ediately when the control switch was placed in the "open" position.
PROBLEM AND INVESTIGATION On February 22, lc73, at 1800, the tulit 2 reactor was at 735.!Ne, 2238 int with reactor pressure at 1000 psig and reactor water level'at 30 inches. The reactor mede switch was in the run positien. Surveillance testing was in progress.
At 1815, LPCI valve !!O-2-1501-32A (LPCI system cross tie valve, P &
ID M-29) was closed during surveillance testing. An attempt was then made to open the valve. However, when the centrol switch for the valve was placed in the "open" positien, the breaker tripped.
This valve had been cycled successfully during routine surveillance on February 20, 1073. This is the first failure on this particular valve.
However, similar problems have been experienced on other valves at the site.
The investigation revealed the toraue switch settines to be 2 3/4 for opening tcrque and 2 1/2 for closing torque. The torque settings were changed to 3 and 11/2 respectively. The thermal overloads and breaker trip settings were checked and found to be within acceptable limits, sk Ycg 3 B304120209 730323 PDR ADDCK 05000237 S
PDR 2025
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The cause of the breaker trips is believed to be in the design of a circuit breaker. It is postulated that, when power is applied to the load device the carnetic trip levers contact the trip bar with sufficient feree to partially disengage the trip mechanism. This action is repeated each time the load device is energized. The result of this action is that the circuit breaker opens at a much lower current than its design trip setting.
The LPCI syctem cross tie valves, 1501-32A and B, are normal locked open valves which are cycled during surveillance testire. The cross tie valves allow discharre to either reactor recirculation loop in the event of LPCI initiatien. The failure of valve 1501-32A would have reduced the capa-city of the LPCI system during the short time the valve was inoperative.
However, both core sprav subsystems, the containment cooling subsystem and l
the diesel generators were operative.
CORRECTIVE ACTION l
As a precautien, the torque settings en valve 1501-32A were changed from 2 3/4 opening and 21/2 closing to 3 and 11/2, which is in agreement with the meter operater verrior reec:mendations. The possible_high current resulting frem the.inco rect torque switch settings could have hastened the breaker malfunctien. The torque switches on similar safety system valves will be checked for proper settings.
A sample breaker has been sent to the manufacturer for further investigation of the apparent design problem. The results of the breaker analysis will dictate additional corrective action.
N.
h W. P. Worden Superintendent WP4:CES:jw cc: WFW Ltr. File 2025 e