ML20006F865

LER 90-002-00:on 900119,HPCI Outboard Steam Supply Isolation Valve Auto Closed on High Room Differential Temp Signal. Caused by Inoperative Temp Control Loop.Troubleshooting of Loop Initiated to Determine malfunction.W/900219 Ltr

ML20006F865
Person / Time
Site:	Hope Creek
Issue date:	02/19/1990
From:	Cowles R, Hagan J Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-002-02, LER-90-2-2, NUDOCS 9003010283
Download: ML20006F865 (5)

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.. Public Service Electric add Gas dc.mpany* P.O. Box 236 Hancocks Bridge, New Jerse/ 08038 '

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Hope Creek Operations 1

I February 19, 19 l

U. S. Nuclear Regulatory Commission Document Control Desk-i Washington, DC 20555 p

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Dear Sir:

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llOPE CREEK GENERATING STATION i

[ DOCKET NO. 50-354 '

k- UNIT.NO. 1

, LICENSEE EVENT REPORT 90-002-00 This Licensee Event Report is being submitted pursuant to

?. the requirements of 10CFR50.73(a)(2)(iv).

Sincerely,

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J . J . %(g an General Manager -

llope Creek Operations RBC/- '

L Attachmentt PORC Mtg.90-018 C Distribution e

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On 1/19/90 at 0717, the HPCI Outboard Steam Supply Isolation Valve (HV-F003) auto-closed on a High Room Differential Temperature Signal via the Steam Leak Detection System. Investigation by control room personnel determined that the signal was initiated due to the differential between outside ambient air temperature sensed in the ventilation supply to the llPCI room (approximately 36' F.) and HPCI room exhaust temperature (approximately 105' F.). Room Coolers for the HPCI room were manually placed in service to lower the room temperature to enable resetting of the isolation. IIV-F003 was re-opened at 0802, and HPCI was returned to a normal, standby lineup. The root cause of this event was determined to be en inoperative temperature control loop which recessitated isolating heating cteam to the Reactor Building Ventilation S)atem (RBVS) to control reactor building temperatures. Corrective actions include initiating troubleshooting of the temperature control loop to determine the source of loop malfunction, conducting thermography in the HPCI room to determine

. sources of excessive heat, and reviewing this incident with all operations Department personnel.

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4 PLANT AND SYSTEM IDENTIFICATION ,

General Electric - Boiling Water Reactor (BWR/4)

High Pressure Coolant Injection (EIIS-Designation: BJ)

Reactor. Building' Ventilation System (EIIS Designation: )

IDENTIFICATION OF OCCURRENCE

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High Differential Temperature In High Pressure Coolant  !

Injection-(HPCI) Room Results in Engineered Safety Feature Actuation (HPCI Outboard Steam Supply Isolation Valve Closure) ,

l - Equipment Malfunction Event Date:.1/19/90 Event Time: 0717 This LER was initiated by Incident Report No.90-004 CONDITIONS PRIOR TO OCCURRENCE ..;

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Plant $n OPERATIONAL CONDITION 1 (Power- Operation), Reactor Power 96%, Unit Load 1060MWe, ,

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DESCRIPTION OF OCCURRENCE On 1/19/90.at 0717, the HPCI Outboard Steam Supply Isolation '

Valve- (HV-F003) auto-closed on a High Room Differential Temperature Signal via the Steam Leak Detection- System.

Investigation by control room personnel determined that the ,

signal was initiated due to the differential betseen outside

. ambient air' temperature sensed in the ventilation supply to the-e HPCI room (approximately 36' F.) and HPCI room exhaust k

temperature (approximately 105'.F.). Room Coolers for the HPCI )

room- were manually placed' in service to lower the room temperature to enable resetting of the isolation. HV-F003 was E re-opened at 0802, and HPCI was returned to a normal, standby lineup.. .

ANALYSIS OF OCCURRENCE Due to unseasonably high outside air temperatures, the Heating  !

Steam System supply to the Reactor Building Ventilation System f* (RBVS) had been isolated the previous day due to a previously

.id6ntified problem with the RBVS temperature control loop.

During the ensuing evening, outside air temperature decreased, .

but heating steam was not returned to service. As previously ,

noted,- at the time of this event, ventilation supply temperature to the HPCI room had decreased to about 36e F.

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i The HPCI room-is normally maintained at between 90* and 100*

F., which appears,~ based on limited industry sampling, to be consistent:with HPCI room temperatures at other BWRs. However, l

J at .tlie time of. this occurrence, the HPCI room temperature was i about 105* . (PSE&G will be conducting thermography of the HPCI L -room to' determine sources of excessive heat.)

b The Steam Leak Detection System is set to isolate HV-F003- at  !

70* differential temperature between the room supply and i

[. ' exhaust ventilation on the assuinption that a steam line break '

has occurred and caused this differential temperature. There is no alarm prior to the isolation signal to alert operators that room temperature 'is approaching the isolation trip J setpoint. When the outside ambient air had decreased to a i

~ temperature: sufficient to. reach this differential temperature trip setpoint, HPCI isolated.

b AEEARENT CAUSE OF OCCURRENCE

.The root cause of this occurrence was an equipment maltuction in the RBVS ' temperature control loop which necessitated isolating the heating steam system. Contributing to the event was the fact that- heating steam to the RBVS had been removed

.trom service and'that the consequences of this condition were not recognized by control room personnel- as outside air temperatures decreased through the night. As a result, heating steam'wasinot returned to service.-

PREVIOUS OCCURRENCES

'There han .been one previous occurrance at Hope Creek -of inolating HPCI due to high room differential temperature

(

Reference:

LER 87-007). This occurrence was attributed to instrument drift in the djfferential temperature monitoring

'T circuitry and an : inadequately established setpoint. The-differential temperature monitor was recalibrated, and the setpoint was raised from 60* F. differential to 70* F.

' differential.

SAFETY SIGNIFICANCE i

As previously noted, no steam leak occurred, and as such the ]

health and safety of the public was not compromised. This i event represents an unecessary challenge to a plant safety '

system. During the time HPCI was out of service (about 50 minutes), the Reactor . Core Isolation Cooling system (RCIC)  !

provided backup to the HPCI system.

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CORRECTIVE ACTIONS

, 1. The RBVS heating steam and chilled water systems were l returned to a normal winter configuration.

l-l 2. The RBVS heating steam temperature control loop will be  !

calibrated or repaired, as necessary, based on completion  !

,- of. troubleshooting' activities.

3. PSE&G will conduct . thermography of the llPCI room to determine sources of excessive room temperatures. ,

4. This incident will be discussed with all Operations Department personnel to stress the need for remaining

, aware of changing weather conditions which could affect

operability of plant as' stems.

Since oly, ]

y J . 11 - an Gene M Manager - -

llope Creek Operations RBC/

CDRC Mtg.90-018

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