ML19329B582
| ML19329B582 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 08/01/1977 |
| From: | Batch S, Lingenfelter J TOLEDO EDISON CO. |
| To: | |
| Shared Package | |
| ML19329B516 | List: |
| References | |
| NUDOCS 8002050717 | |
| Download: ML19329B582 (3) | |
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LICENSEE EVENT REPORT
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working on the leads without authorizat' ion.
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. TOLEDO EDISON COMPANY DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION O'
SUPPLEMENTAL INFORMATION FOR LER NP-32-77-9 e
DATE OF EVENT: July 22, 1977 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Loss of Decay Heat Flow caused by unauthorized work on pressure transmitter leads.
Conditions Prior to Occurrence: The plant was in Mode 5, with Power (MWT) = 0 and Load (MWE) = 0.
Reactor Coolant Pressure 230 psig and Reactor Coolant Temperature 1100F. Decay Heat Pump 1-2 in operation recirculating Reactor Coolant System (RCS).
Description of occurrence: An Instrument and Control (I&C) mechanic had been directed via a Maintenance Work Order (MWO I&C 368-77) to inspect for proper insulation on the signal lead on the output of the RCS pressure transmitter in Channel 4 of the Saf,ety Features Actuation System (SFAS). While conducting this inspection, the I6C mechanic discovered a loose connection. He attempted to loosen the terminal screw and slide the lead under the screw, momentarily opening and closing the circuit. The closing of the circuit caused a current surge which tripped the bistable and closed the Decay Heat (DH) suction from g the RCS.
The DH Pump 1-2 was then immediately stopped at 2338 hours0.0271 days <br />0.649 hours <br />0.00387 weeks <br />8.89609e-4 months <br /> on July
/ 22, 1977, in violation of Technical Specification 3.4.1.
The decay heat suction from the RCS Valve DHil was re-opened and DH Pump 1-2 was restarted at 2339 hours0.0271 days <br />0.65 hours <br />0.00387 weeks <br />8.899895e-4 months <br />.
The I&C mechanic realized he did not have a proper connection so he removed the wire and replaced it properly.
This again resulted in closure of the DH suction from the RCS Valve DH11 and subsequent tripping of the DH Pump l-2 at 2354 hours0.0272 days <br />0.654 hours <br />0.00389 weeks <br />8.95697e-4 months <br /> on July 22, 1977.
At 0010 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> on July 23, 1977, the DH suction from the RCS was re-opened and DH Pump 1-2 was again restarted. The I&C mechanic was discovered working on the terminals and was immediately stopped. While the DH Pump was off, the station was in violation of Technical Specification 3.4.1 which requires at least one DH Pump or Reactor Coolant Pump to be in operation.
Designation of Apparent Cause of Occurrence: Personnel error is the cause of this The I&C mechanic vas working on the leads from the pressure trans-occurrence.
mitter without authorization. The work performed on the evnnection was not auth-orized under the work order being used.
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DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION
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,EUPPLEMENTAL INFORMATION FOR LER NP-32-77-9 PAGE 2 Analysis of Occurrence: Since flow was not needed for decay heat removal, and the Decay Heat Pump was restarted, no threat resulted to the health and safety of the public or to station personnel.
Corrective Action: The I&C mechanic was stopped from continuing work without authorization. To prevent recurrence due to unauthorized work being performed, the I&C Foreman was instructed to review with all I6C mechanics the requirements of the Maintenance Administrative Procedure, AD 1844.00.
Particular emphasis will be placed on the requirement for having a Maintenance Work Order and Shift Foreman's permission before commencing work.
4 Failure Data: The DH suction from the RCS Valve DHil was closed on three pre-vious occurrences (NP-32-77-2, NP-32-77-3 and NP-32-77-5) but the cause for the closure was not identical since wiring insulation error, procedure error and personnel failure to follow procedure were the causes for the previous occurrences.
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