05000352/LER-1998-001, :on 980124,Unit 1 HPCI Sys Initiation Occurred. Caused by Less than Adequate Understanding for Potential Loss of Grounding Signal Upon Troubleshooting Control Form. Event Will Be Reviewed by All Work Group Personnel

:on 980124,Unit 1 HPCI Sys Initiation Occurred. Caused by Less than Adequate Understanding for Potential Loss of Grounding Signal Upon Troubleshooting Control Form. Event Will Be Reviewed by All Work Group Personnel

ML20203E290
Person / Time
Site:	Limerick
Issue date:	02/23/1998
From:	Moore T PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:
Shared Package
ML20203E277	List: 05000352/LER-1998-001, :on 980124,Unit 1 HPCI Sys Initiation Occurred. Caused by Less than Adequate Understanding for Potential Loss of Grounding Signal Upon Troubleshooting Control Form. Event Will Be Reviewed by All Work Group Personnel
References
LER-98-001, LER-98-1, NUDOCS 9802270013
Download: ML20203E290 (4)

LER-1998-001, on 980124,Unit 1 HPCI Sys Initiation Occurred. Caused by Less than Adequate Understanding for Potential Loss of Grounding Signal Upon Troubleshooting Control Form. Event Will Be Reviewed by All Work Group Personnel

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv), System Actuation
3521998001R00 - NRC Website

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e spron matety a singie.gateJ typewritten line5J Lib) on 01/24/98, at 0019 hours2.199074e-4 days <br />0.00528 hours <br />3.141534e-5 weeks <br />7.2295e-6 months <br /> a Unit 1 High Pressure Coolant Injection (HPCI) system initiation occurred coincident with the removal of a troubleshooting control form (TCF). The TCP was initiated on 01/21/98, to install a recorder to monitor performar.cc of the IB Residual Heat Removal Pump Minimum Flow Valve control circuit. Following TCP installation, a failed trip unit was identified and was replaced.

With the cause of the spurious valve operation determined, the TCP was no longer required and TCP removal commenced.

While removing a banana jack from one of the control relays, thereby interrupting a series (daisy chained) ground circuit, arching was observed and relay chatter was heard by the technician.

Coincident with this action, the HPC1 system initiated and operated in the minimum flow mode; however, no HPCI injection or power excursions occurred. The HPCI system was secured and lined up for automatic operation. The HPCI initiation resulted from a temporary i

interruption in the ground circuit that caused a current flow through a HPCI initi.4 tion relay.

The cause of this event was less than adequate undert,tanding for the potential loss of grounding signal upon TCP removal.

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liaCh9U:Lundi On January 21, 1998, at 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br />, the Work Week Manager (WWM) contacted the shift I&C technicians stating that the Residual 11 eat Removal ( Rif R, EIIS:BO) System Manager wanted to monitor minimum flow valve, 11V - 0 51 - 1 F 0 07 B, for troubleshooting purposes.

The valve had exhibited previous occurrences related to spurious closure prior to this event.

Through communications between the I&C shift technicians, the Engineering Duty Manager (EDM) and the WWM, it was determined that a Troubleshooting Control Form (TCF) would be utilized to hook up a recorder to monitor valve trip unit input and output, and valve relay status.

Followirg operations approval the TCP was installed on January 22,

998, at 0300 hours0.00347 days <br />0.0833 hours <br />4.960317e-4 weeks <br />1.1415e-4 months <br />.

During the installation of the TCF, I&C technicians noticed that the trip unit output was reading 7.5 volts.

This expected value was zero (0) volts. A work order was generated on January 23, 1998 to replace the trip unit.

Following the trip unit replacement, a satisfactory post maintenance test was performed verifying proper operation of the minimum fluw valve, and removal of the TCF test points began.

Ileseription of the Event :

At 0019 hours2.199074e-4 days <br />0.00528 hours <br />3.141534e-5 weeks <br />7.2295e-6 months <br /> on January 24, 1998, the High Pressure Coolant Injection (llPCI, EIIS:BJ) system opuriously started and began operating in the minimum flow mode of operation.

The Plant Reactor Operator (PRO) verified Unit 1 11PCI did not inject into the reactor vessel.

The Unit 1 Reactor Operator (RO) verified no power excursions had occurred.

The Floor Supervisor was sent to the auxiliary equipment room to investigate.

The Floor Supervisor confirmed that no trip units actuated.

Unit 1 IIPCI was secured and lined up for automatic operation in accordance with the applicable operating procedure.

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An investigation identified that the llPCI initiation occurred upon removal of a banana jack located on the ground circuit of RHR relay EllA K5B.

Removal of the banana jack was being performed by an I&C technician during the restoration of the TCP for monitoring of the RHR minimum flow valve. While properly removing the banana jack in accordance with the TCP restoration, the I&C technician observed arching and heard relay chatter.

The llPCI initiation was caused when a temporary interruption in the series (daisy chained) ground circuitry occurred between two relays fed from a single trip unit during removal of the banana jack.

The ground interruption caused a current path through a llPCI initiation relay.

At. 0348 hours0.00403 days <br />0.0967 hours <br />5.753968e-4 weeks <br />1.32414e-4 months <br /> on January 24, 1998, a 4-hour notification was made to the NRC in accordance with the requirements of 10CFR50.72 (b) (2) (ii),

since this event resulted in an unplanned automatic ESF actuation.

This report is submitt ed in accordance with 10CFR50.73 (a) (2) (iv).

Analysin of tht_liYf.DL The consequences of this event were minimal.

The llPCI system operated in the minimum flow mode, taking a suction from the condensate storage tank (CST), and returning flow back to the CST again.

There were no events which occurred during the time the HPCI system had been c perating in minimum flow which would have required injection of the llPCI system.

Additionally, operatier of HPCI in the minimum flow mode would not have prevented automatic lineup of the system if injection was required.

The steam use for llPCI did not impact reactor power and there were no adverse radiological consequences due to the use of reactor steam for operation of HPCI.

A Health Physica review of the event determined that no unexpected exposures incurred due to the HPCI initiation.

Cause of the Event

Less than adequate understanding of the potential for a loss of ground that could result in the energizing of a llPCI initiation relay.

During the removal of the TCF, the daisy chained circuit ground was interrupted, and this resulted in an energized relay back feeding a llPCI initiation relay that resulted in the HPCI initiation.

The removal of the banana jack was a required step in the TCP restoration process; however the I&C technician did not understand the impact the banana jack removal would have on the system during the TCF planning

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The less than adequate understanding of the daisy chained ground circuit by the I&C technician lead to insufficient research of the troubleshooting activity.

Cross-disciplinary interaction was less than adequate.

The I&C technician and the system manager did not directly discuss the troub.1.eshooting activity prior to installation.

Such a discussion may have lead to choosing alternate monitoring locations.

Corrective Actions

This event will be reviewed by all work group personnel that are expected to perform similar troubleshooting to address: t rouble shoot.ing techniques including initial point checks vs. intrusive monitoring, researching all relevant documentation prior to TCP generation, and ensuring adequate pre-job cross-disciplinary interaction.

This review was completed for station I&C technicians as of February le, 1998.

Evaluations for the remaining relevant organizations addressing the above concerns will be completed by February 27, 1998, Contractors will likewise be briefed on this event by April 01, 1998, prior to performing work in the upcoming refuel outage.

Troubleshooting techniques related to daisy chained circuits will become part of the formal Routine Continuing Training (RCT) program to ensure continued emphasis in this area.

The next cycle of RCT training will be implemented by October 01, 1998.

En yipus similar Occurrences No previous occurrences were identified enat related to HPCI system initiations as a result of test equipment removal.

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