ML20011E393

LER 90-001-00:on 900106,turbine Trip on Moisture Separator High Level Resulted in Reactor Scram.Caused by Combination of Equipment Failure & Cognitive Personnel Errors.Moisture Separator Drain Control Instrumentation tuned.W/900205 Ltr

ML20011E393
Person / Time
Site:	Hope Creek
Issue date:	02/05/1990
From:	Cowles R, Hagan J Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-001-02, LER-90-1-2, NUDOCS 9002130341
Download: ML20011E393 (9)

Text

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e"4 -O PSEG Pubhc SN ,e Eloctric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Hope Creek Operations -

i February 5, 1990 t

U. S. Nuclear Regulatory Commission Document: Control Desk '

Washington, DC 20555 Dear Sir

' HOPE CREEK GENERATING STATION  !

DOCKET NO. 50-354 UNIT NO. 1  !

LICENSEE EVENT REPORT 90-001-00 f

This Licensee Event Report is being submitted pursuant to the requirements of 10CFR50.73 (a) (2) (iv) . .

Sincere:gy ,

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. . Ha an General- ager -

Hope Creek Operations RBC/'

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On 1/6/90 at 0120, during performance of a surveillance procedure which tcsts the Main Turbine Combined Intermediate Valves (CIV), the "A" i Moisture Separator experienced a high level condition. In response to ,

this high level condition, the associated dump valve opened, but not in i timo to prevent a turbine trip on moisture separator high level.

ICmediately following the turbine trip, the reactor scrammed on a Turbine Control Valve Closure signal from the Reactor Protection System. All control rods were verified to be inserted, and plant systems responded as expected, with minor exceptions as noted in the text of this report.

Investigation subsequent to the scram determined that multiple causes  ;

combined to result in the scram - moisture separator level controllers which were not optimally tuned and the cycling of a CIV prior to atabilization of moisture separator level after cycling a previous CIV. Corrective actions included tuning of the moisture separator drain control instrumentation loops, procedurally increasing the time between cycling of CIV's 6uring the subject surveillance, counselling the Nuclear Control Operator (NCO, R9 licensed) who performed the surveillance, and l i

including a review of the event during the next licensed operator i requalification cycle.

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PLANT AND SYSTEM IDENTIFICATION General Electric - Boiling Water Reactor (BWR/4)

Main Turbine (EIIS Designation: TA) .  :

Reactor Protection System (EIIS Designation: JC)

[ Moisture Separator (EIIS Designation: SN)

Feedwater System (EIIS Designation: SJ) i Condensate System (EIIS Designation: SD) .  ;

I IDENTIFICATION OF OCCURRENCE Turbine Trip on Moisture Separator High Level Results in Reactor Scram Due to Equipment Deficiencies and Personnel Error Event Date: 01/06/90 Event Time: 0120 .

This LER was initiated by Incident Report No.90-001 3:

CONDITIONS PRIOR TO OCCURRENCE Plant in OPERATIONAL CONDITION 1 (Power Operation), Reactor ,

Power 97%, Unit Load 1062 MWo. Output limited by feedwater heaters 1C and 2C being out of service. [

t DESCRIPTION OF OCCURRENCE On - 1/6/90 at 0120, during performance of a surveillance- -

procedure which tests the Main Turbine Combined Intermediate  !

Valves (CIV), the "A" Moisture Separator experienced a high

• 1evel condition. In response to this high level condition, the associated dump valve opened, but not in time to prevent a turbine trip on moisture separator high level. Immediately following the turbine trip, the reactor scrammed on a Turbine Control Valve (TCV) closure signal from the Reactor Protection System (RPS). All control rods were verified to be inserted,

• and plant systems responded as expected, with the following exceptions:

1. The "B" Secondary Condensate Pump (SCP) minimum flow valve -

failed to open, resulting in a trip of the "B" SCP on low flow.  ;

2. Post-accident monitoring (PAMS) pressure recorders "A" and "B"_did not function properly.

3. Redundant Reactivity Control System (RRCS) Division I, channel "B" failed to trip.

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I DESCRIPTION OF OCCURRENCE, CONT'Q  !

. t The "H" and "P" Safety _ Relief Valves (SRVs) lifted as designed'

. to control reactor pressure, and vessel level decreased to L approximately 10" (narrow range indication) during-the course ,

of the transient, well above any Emergency Core Cooling System actuation levels. Vessel level was restored using the "A" .

Reactor Feed pump. Plant parameters were stabilized within 30  !

minutes. A.four hour non-emergency report was made to the NRC  ;

Operations Center IAW 10CFR50.72, and an investigation -was l initiated to determine the cause of the scram. Due to a scheduling error ~by the LER Coordinator, this report is being f submitted 1 day late, a

ANALYSIS OF OCCURRENCE On.1/6/90 at 0045, the control room Nuclear Control Operator I (NCO, RO licensed) initiated performance of the weekly Turbine Overspeed Protection System Operability Test procedure. The

? purpose of this surveillance is to demonstrate the operability ,.

of the main turbine overspeed protection system by cycling the Turbine.Stop Valves (TSVs) and the Combined. Intermediate Valves 3 h (CIVs) as required by technical specifications.

The first caution in the procedure stated that "At least one L ,

minute between valve operations shall be exercised.to allow the r

' 'EHC System time to stabilize.".. The TSVs were cycled with P satisfactory results, and at 0117:20, the NCO cycled CIV-#1 closed. 31 seconds after completing the cycling of CIV-#1,the .;

! NCO began to cycle CIV-#4. At 0119:36, a " Moisture Separator  ;

"A" Emergency Dump Tank High Level" alarm was received, and at 0120:19, the turbine tripped on moisture separator high level i and the reactor scrammed on a TCV closure signal via RPS.

Investigation subsequent to the scram focused on two primary ,

areas; the instrumentation for moisture separator level control l and the NCO's performance of the surveillance test. l l

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~&NALYSIS OF OCCURRENCE. CONT'D

1. Moisture Separator Level Control Instrumentation Refer to Attachment 1. Moisture Separator level is normally controlled via the cycling of level control valves LV-1364A, B,

• and C, which route condensate from the Moisture Separator Drain Tank to Feedwater lleaters SA, B and C via individual 8" lines.

In the event of a high Drain Tank level, the Emergency Dump Valve opens and drains directly to the Main Condenser via a single 8" line. The cycling of a CIV induces a significant ,

transient on the-associated Moisture Separator, and a swing in level during the course of cycling a CIV is normal and '

expected, however, not as severe as was experienced in this event.

Following the scram, the response and settings of the Drain Tank level control system (instrumentation and valves) was checked. Investigation determined that a variety of factors '

contributed to a less than adequate response of the level control system for "A" Moisture Separator:

A. Level Controller LIC-1040A was determined to be adjusted

• to a less than optimum setting, which led to a sluggish response of LV-1364A and LV-1364B above the 50% open position. There is no recurring task for preventive maintenance of this controller or tuning of the entire control loop.

B. The air supply to the positioner for LV-1364C was isolated, as such, this valve did not open in response to the Moisture Separator high level transient. LV-1364C was worked several times during the station 2nd refueling outage. Subsequent investigation has determined that the air supply to the positioner was not properly restored by Maintenance Department personnel following one of these maintenance activities.

C. The response for Emergency Dump valve LV-1039A was sluggish above the 50% open position. Again, the tuning ,

of the level control loop for this valve was less than optimum. All instruments in this loop had been individually calibrated during September of 1989, however, a total loop functional test was not required to be performed.

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Lastly, the response of the Moisture Separators during previous testing was reviewed. During the course of interviews with Operations Department control room personnel following the .

i scram, it was determined that the "A" Moisture Separator has experienced level control oscillations in the past during .

CIV cycling. This finding was confirmed by review of plant process computer printouts from past CIV testing. -It was i apparent that the personnel performing the tests waited up to three minutes between CIV cycles to. allow Moisture Separator levels to stabilize. This system response, however, was considered normal and as such, a work request was not initiated

, to troubleshoot the level control system.

Performance of Surveillance Procedure by NCO  :

The NCO who performed the testing had done so on many prior  ;

occasions. Post scram analysis determined that on this occasion, the NCO deviated from the surveillance procedure during performance of the test. The NCO did not wait 1 minuto '

between cycling CIV's, as required by the procedure for stabilization of EHC system pressures. He did, however, verify EHC system stabilization prior to cycling CIV-#4. As mentioned above, during previous tests, operators had waited up  :

to 3 minutes for Moisture Separator levels to stabilize. It-should be noted that the procedure did not specify a waiting period for Moisture Separator stabilization. i APPARENT CAUSE OF OCCURRENCE All of the above factors combined to result in the scram, and

• it is not feasible to reconstruct the event and determine which factor played the primary role in the final result. As such, ,

.the root cause of this event has been classified as a combination of equipment failure and cognitive personnel errors.

PLANT TRANSXENT EMSPONSE

1. The "B" Secondary Condensate Pump Minimum Flow Valve did not open due to a failed air line on the valve actuator.

L The severe service of these valves subjects the valve and actuator to significant movement when cycled, making the actuator air lines failure prone. The air line was replaced and the valve retested satisfactorily.

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2. PAMS Pressure Recorder "A" was inoperable prior to this  !

event due to recorder not advancing properly. .The ,

recorder was repaired and returned to service on 1/11/90.

L l' PAMS Pressure Recorder "B" did not ink properly during this event. The pens were replaced and the recorder was I, returned to service. '

3. A review was conducted of the failure of RRCS Division I ,-  !

channel B failing to trip. This channel should trip when '

reactor pressure reaches 1071 PSIG. During the course of this event, the highest reactor pressure seen was 1075 i PSIG. Troubleshooting of associated RRCS pressure instrumentation found no problems, and tho' Channel "B" input was tested satisfactorily. It was concluded that Channel "B" did not trip because, with instrumentation  ;

tolerances. considered, reactor pressure' did not quite' '

reach the setpoint for Channel "B" RRCS.  !

PREVIOUS OCCURRENCES This'isthe first occurrence of a scram (or other type of reportable occurrence) at Hope Creek as a result of level control problems with a Moisture Separator. Additionally, a review of in-house experience indicates no history of significant operational type- problems with the Moisture .

Separators.

SAFETY' SIGNIFICANCE The potential safety impact of this event was minimal, as a- '

plant scram is an analyzed event, and with minor exceptions, all' systems responded as expected. None of the abnormal system -

responses posed a threat to the ability to achieve and maintain -

safe shutdown conditions. This event posed no threat to the i health and safety of the general public.

CORRECTIVE ACTIONS  :

1. The "A" and "B" Moisture Separator instrumentation loops were tuned while at 25% reactor power following plant "

restart and the subject surveillance was again performed.

Level control of the Moisture Separators was observed during power - ascension from restart to 100%, and no deviations from expected responses were noted. ,

2. Planning Department will initiate a recurring task to calibrate Moisture Separator Drain Tank level controller (LIC-1040A).

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3. Systems Engineering will develop a loop response functional test for the Moisture Separator level control i instrumentation.  !

4. The. General Manager and Operations Manager have communicated their expectations to all operators and supervisors regarding deficiencies noted in'this report. . ]

l S. The NCO who performed the subject surveillance test was counselled with regards to his actions in not adhering to the procedure.

6. Systems Engineering is pursuing a resolution to the movement of Secondary Condensate Pump Minimum Flow Valves.

~7. This event will be reviewed with all licensed personnel by- I the Nuclear Training Department during the next licensed operator requalification cycle.

8. The Maintenance Manager will review control of air I supplies to valve positioners following maintenance on air operated valves with all Maintenance Department personnel.

Sincer ly, 1 -

J .F gai enera nager - t Hope Creek Operations RBC/

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