ML20084D527
| ML20084D527 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 04/13/1973 |
| From: | Worden W COMMONWEALTH EDISON CO. |
| To: | Anthony Giambusso US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084D531 | List: |
| References | |
| 2531, 293-73, NUDOCS 8304120076 | |
| Download: ML20084D527 (2) | |
Text
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O Commonwealth Edison Company ONE FIRST N A T I O-N A L PLAZA lir CHICAGO. ILLINOIS l
AMr.u S.oJr to:
POST OPPICE BOX 747 & C H IC A G O, ILLINOl$ 60490 WPW Ltr.#293-73 Dresden Nuclear Power Station R. R. #1 Morris, Illinois 60450 CD April 13, 1973 Y
C6 Mr. A. Giambusso 50-237 APR1G 1973 > -II Deputy Director for Reactor Projects
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Directorate of Licensing C m s:Ica U. S. Atomic Energy Comission gN, M
Washington, D. C.
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SUBJECT:
LICENSE DPR-19, DRESDEN NUCLEAR POWER STATION, UNIT #2, SECTION 6.6.B.3 0F THE TECHNICAL SPECIFICATIONS.
Dear Mr. Giambusso:
This is to report a condition relating to the operation of the unit in which on April 5,1973, the supply breaker for the isolation condenser valve MO-2-1301-1 was found tripped, thus rendering the system inoperable as specified in the Technical Specifiestions section 3.7.D.I.
PROBLEM AND INVESTICATION On April 5,1973, at 0900 hours0.0104 days <br />0.25 hours <br />0.00149 weeks <br />3.4245e-4 months <br />, position indicating lights for the isolation condenser valve MO-2-1301-1 were found to be out.
Several checks were made in the control room, which indicated the problem was at the supply bus for the valve. A check of the supply breaker for the valve revealed that it had tripped.
The breaker and overloads were then removed and tested.
The test showed that both the breaker and the overload operated correctly. The equipment was then reinstalled and the valve returned to service.
Upon further investigation, it was discovered that the valve had been cycled on April 4, 1973 between 1600 and 1730, and is believed to have tripped at this time. At approximately 1800, it was noted that the light was out, but erroneously attributed this to a problem with the light socket.
It is believed.that the breaker trip can be attributed to the cycling of the valve during line break sensor surveillance.
During each cycle of the valve, power is applied to the breaker trip mechanism. Each time that power is applied to the load trip device, the magnetic trip levers contact
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Mr. A. Giambumco April 13, 1973 the trip bar with sufficient force to partially disengage the trip mechanism.
The result of this action is that the current at which the breaker opens is at a much lower value than its design trip setting.
The function of the 1301-1 valve is to isolate the reactor from the isolation condenser in the event an isolation condenser steam line break should occur.
Since the 1301-1 valve failed in the open position, it would not have been able to perform its isolation function. Had an isolation condenser steam line break occurred in the relatively short length of pipe between the 1301-1 and 1301-2 valves, no isolation protection would have been avialable, however, the 1301-2 valve would have provided protection for 4
i downstream line breaks.
CORRECTIVE ACTION A sample breaker has been sent to the manufacturer for analysis as a result of a similar failure reported in our letter dated March 23, 1973.
1 The results of the breaker analysis will dictate future corrective action.
J Additionally, discussions with representatives of our Electrical Engineering Department are in progress to formulate a program to remedy the problems which have been experienced with breakers, torque switch settings, and overload ratings. The program is expected to be formulated by June 1, 1973.
In the meantime, the station will review the line break sensor 4
surveillance procedures to see if it is possible to reduce valve cycles during this testing.
Sincerely, death
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W. P. Worden i
~ Superintendent WPW:do cc:
WPW Ltr. File
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