05000272/LER-1978-073, Forwards LER 78-073/01X-1.Detailed Event Analysis Encl

Forwards LER 78-073/01X-1.Detailed Event Analysis Encl

ML18085B116
Person / Time
Site:	Salem
Issue date:	03/25/1981
From:	Uderitz R Public Service Enterprise Group
To:	Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML18085B117	List: 05000272/LER-1978-073, Forwards LER 78-073/01X-1.Detailed Event Analysis Encl 05000272/LER-1978-073-01, /01X-1:on 781127,loss of Vital Instrument Bus 1B de-energized RCP Breaker Open Relay in Solid State Protection Sys,Initiating Reactor Trip.Caused by Failure of Output Transformer in Supply Inverter
References
NUDOCS 8104020481
Download: ML18085B116 (3)

LER-1978-073, Forwards LER 78-073/01X-1.Detailed Event Analysis Encl

Event date:
Report date:
2721978073R00 - NRC Website

text

f PS~G Public Service Electric and Gas Company 80 Park Plaza Newark, N.J. 07101 Phone 201/430-7000 Mr. Boyce H. Grier Director of USNRC March 25, 1981 Off ice of Inspection and Enforcement Region 1 631 Park Avenue King of Prussia, Pennsylvania 19406

Dear Mr. Grier:

LICENSE NO. DPR-70 DOCKET NO. 50-272 REPORTABLE OCCURRENCE 78-73/0lX-l SUPPLEMENTAL REPORT Pursuant to the requirements of Salem Generating Station Unit No. 1 Technical Specifications, Section 6.9.1, we are submitting supple-mental Licensee Event Report for,Reportable Occurrence 78-73/0lX-l.

Sincerely yours,

/!1//1~/*

R. A. Uderit:z General Manager -

Nuclear Production CC:

Director, Office of Inspection and Enforcement (30 copies)

Director, Office of Management Information and Program Control (J)_l'L_G<::::>

( 3 copies)

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• Report Number:

Report Date:

Occurrence Date:

Facility:

78-73/0lX-l March 25, 1981 11/27/78 Salem Generating Station -

Unit 1 Public Service Electric & Gas Company Hancocks Bridge, New Jersey 08038 IDENTIFICATION OF OCCURRENCE:

Loss of lB Vital Instrument Bus CONDITIONS PRIOR TO OCCURRENCE:

Operational Mode 1, Reactor Power 100%

DESCRIPTION OF OCCURRENCE:

At 0445 hours0.00515 days <br />0.124 hours <br />7.357804e-4 weeks <br />1.693225e-4 months <br /> on November 27, 1978, loss of lB Vital Instrument Bus initiated a Reactor Coolant Loop Low Flow above PS reactor trip.

The Action Statement for Technical Specification 3.8.2.l was imple-mented.

Nos. 12 and 13 Auxiliary Feed Pumps did not start with low steam generator level.

No. 12 was manually started by the control room operator.

Recovery from the reactor trip was in prog-ress when a High Steam Flow -

Low Tave inadvertent safety injection occurred at 0502 hours0.00581 days <br />0.139 hours <br />8.300265e-4 weeks <br />1.91011e-4 months <br />.

The loss of lB Vital Instrument Bus resulted in inputs from each Stearn Generator Hi Stearn Flow logic to the Safety Injection logic.

During recovery from the trip, Tave decreased to less than 543°F causing the proper coincident logic for Safety Injection.

The safety injection was reset three minutes later.

The Safeguards Equipment Control System (SEC) was activated by the safety injection signal, however, lB Diesel, No. 11 Charging Pump and No. 12 RHR Pump failed to start.

The Action Statements for Technical Specifications 3.5.2 and 3.8.1.1.b were implemented.

No. 11 RHR Pump started from SEC and was secured after the safety injection.

An attempt was made to restart No. 11 RHR Pump at 0630 hours0.00729 days <br />0.175 hours <br />0.00104 weeks <br />2.39715e-4 months <br /> but the breaker would not close.

Investigation of the bus failure showed that the inverter had failed and the bus was re-energized from the emergency supply solatron transformer.

The surveillance requirement for Technical Specification 3.8.1.1.2.a.2 was satisfactorily completed by 0756 hours0.00875 days <br />0.21 hours <br />0.00125 weeks <br />2.87658e-4 months <br /> and lB Diesel was declared operable at 1200 hours0.0139 days <br />0.333 hours <br />0.00198 weeks <br />4.566e-4 months <br /> upon completion of a one hour run.

Boration commenced at 0825 hours0.00955 days <br />0.229 hours <br />0.00136 weeks <br />3.139125e-4 months <br /> to bring the RCS to Xenon free cold shutdown condition.

At 1315 hours0.0152 days <br />0.365 hours <br />0.00217 weeks <br />5.003575e-4 months <br />, the plant started cooldown and entered Hot Shutdown Mode 4 at 2100 hours0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br />.

RHR was initiated at 2240 hours0.0259 days <br />0.622 hours <br />0.0037 weeks <br />8.5232e-4 months <br /> and cooldown continued.

All Technical Specification Action Statements were terminated prior to reaching cold shutdown.

ECCS Actuation Report for Reportable Occurrence 78-74/990 was submitted on January 26, 1979, as required by Technical Specification 6.9.2.a.

March9s, 1981 LER 78-73/0lX-l 2 -

DESIGNATION OF APPARENT CAUSE OF OCCURRENCE:

The loss of lB Vital Instrument Bus was traced to the failure of the output transformer and two regulating resistors in the supply inverter.

The loss of the bus de-energized the "12 RCP Breaker Open" input relays to the Solid State Protection System.

This erroneous indication of a tripped RCP caused the low flow reactor trip logic to initiate the reactor trip.

The failure of lB Diesel, No. 11 Charging Pump and No. 12 RHR Pump to start with the initiation of safety injection is due to none of this equipment receiving an actuating signal from the lB SEC cabinet which was de-energized by the lB Vital Instrument Bus failure.

ANALYSIS OF OCCURRENCE:

Technical Specification 3.8.2.1 for on-site power distribution systems requires 115 volt vital instrument buses and inverters operable for lA, lB and lC buses.

The Action Statement requires that with less than the above complement of AC buses operable, restore the inoperable bus to operable status within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> or be in at least Hot Standby within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in Cold Shutdown within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

The lB Vital Instrument Bus was re-energized from the emergency supply solatron transformer and the inverter was returned to service within 21 hours2.430556e-4 days <br />0.00583 hours <br />3.472222e-5 weeks <br />7.9905e-6 months <br />.

The RCS was borated to Xenon free cold shutdown condition and entered Hot Shutdown 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> after the reactor trip.

Cooldown continued until all Technical Specification limiting conditions were terminated.

The failure of Noo lB Diesel, No. 11 Charging Pump and No. 12 RHR Pump to start at the time of safety injection is predictable under the circumstances and has been accounted for in the overall plant design of the safety systems.

The failure of No. 13 Auxiliary Feed Pump to start appears to be a random failure.

Operational testing has been done which shows the pump to be fully operational.

CORRECTIVE ACTION

The failed output transformer and regulating resistors in the lB Instrument Bus inverter were replaced and tests were run to verify operability.

The overspeed trip reset latch mechanism on No. 13 Auxiliary Feed Pump was readjusted to provide more positive latch operation.

No. 11 RHR Pump breaker was replaced and tested satisfactory.

No further corrective action is necessary.

FAILURE DATA:

Garrett Static Power Conditioning - Static Inverter -

Model Series 1 Transformer/Regulating Mode 5 kva Manufacturer:

Airesearch Manufacturing Company Prepared By W. J. Steele SORC Meeting No.

81-19