ML18094B447

LER 90-010-00:on 900403,reactor Trip Signal Initiated Due to lo-lo Level in Steam Generator 12.Caused by Personnel Error. Event Reviewed by Operations Dept Mgt & Personnel Involved Held accountable.W/900425 Ltr

ML18094B447
Person / Time
Site:	Salem
Issue date:	04/25/1990
From:	Miller L, Pollack M Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-010-01, LER-90-10-1, NUDOCS 9005070358
Download: ML18094B447 (6)

Text

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Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station April 25, 1990 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Dear Sir:

SALEM GENERATING STATION LICENSE NO. DPR-70 DOCKET NO. 50-272 UNIT NO~** 1 LICENSEE EVENT REPORT 90-010-00 This Licensee Event Report is being submitted pursuant to the requirements of the Code of Federal Regulations 10CFR 50.73(a) (2) (iv). This report is required within thirty (30) days of discovery. '

Sincerely yours, L. K. Miller General Manager -

Salem Operations MJP:pc Distribution 9005070358 900425 PDR ADOCK 05000272 S PDC The Energy People

/pt I\ L-2189 (SM) 12-88

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• I.*.* *PPtO*im*r.ly fiffHn ring/.-i,,.** tvJMwritton /inn} 1181 On April 3, 1990 at 1558 hours0.018 days <br />0.433 hours <br />0.00258 weeks <br />5.92819e-4 months <br />, during reactor startup operations, *a reactor trip signal was initiated due to Low-Low Level in No. 12 Steam Generator _(S/G). At the time of the trip signal, the Control Rod shutdown banks were withdrawn and the control banks inserted. The root cause of this event has been attributed to personnel error. The Nuclear Control Operator (NCO) did .not ensure optimum initial conditions prior to swapping from No. 11 S/G to No. 12 S/G for maint.aining RCS temperature. Subsequently, No. 12 S/G level continued to decrease, after the transfer, que to inadequate AFW flow with the trip setpoint eventually being reached. Contributing to this event was inadequate command and control by the Nuclear Shift Supervisor (NSS) during the transient. This event was reviewed with subsequent operating shifts prior to their assuming the watch. Lessons learned from this event was stressed. This event has been reviewed by Operations DePa.rtment management and personnel involved have been held accountable. This event will be reviewed by the PSE&G Nuclear Training Center for incorporation into applicable training programs.

NllCl'oml311 Ill.all

I I LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 90-010-00 2 of 5 PLANT AND SYSTEM IDENTIFICATION:

Westinghouse - Pressurized Water Reactor Energy Industry Identification System (EIIS) codes are identified in the text as f xxl IDENTIFICATION OF OCCURRENCE:

Reactor Protection System Actuation - Caused by No. 12 S/G Low-Low Level due to personnel error Event Date: 4/03/90 Report Date: 4/25/90 This report was initiated by Incident Report No.90-241.

CONDITIONS PRIOR TO OCCURRENCE:

Mode 3 (Hot Standby) - Reactor Startup in Progress Major equipment out of service at the time of the event included the No. 11 Steam Generator Feed Pump, which was cleared and tagged to support thrust wear inspections DESCRIPTION OF OCCURRENCE:

On April 3, 1990 at 1558 hours0.018 days <br />0.433 hours <br />0.00258 weeks <br />5.92819e-4 months <br />, during reactor startup operations *. a reactor trip signal {JCI was initiated due to Low-Low Level in No. 12 Steam Generator (S/G). At the time of the trip signal, the Control Rod {AAI shutdown banks were withdrawn and the control banks inserted.

The Unit was stabilized and remained in Mode 3. On April 3, 1990 at 1630 hours0.0189 days <br />0.453 hours <br />0.0027 weeks <br />6.20215e-4 months <br />, the Nuclear Regulatory Commission was notified of the actuation of the Reactor Protection System {JCI in accordance with Code of Federal Regulations 10CFR 50.72(b) (2) (ii).

SEQUENCE OF EVENTS:

Event 4/3/90 1500 Startup on hold (in Mode 3) awaiting Technical Specification relief relative to Main Steam Isolation Valve testing RCS temperature being maintained by steaming No.

11 S/G via the llMSlO Atmospheric Relief valve 1515 4x12 shift assumes the watch 1550 RCS temperature control swapped from llMSlO to

I I LICENSEE EVENT REPORT {LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 90-010-00 3 of 5 SEQUENCE OF EVENTS: {cont'd)

Date Event 12MS10 due to work on Turbine Deck No. 12 S/G was approximately 28% and trending down at the time of the swap 1550 - 1558 12 S/G level continued trending down Control Room indication of Auxiliary Feedwater (AFW) {BAI flow at zero (0) to No. 12 S/G Operator attempts to increase Aux. Feedwater flow to No. 12 S/G by increasing demand (tapping the controls) for the 12AF21 valve (No. 12 S/G AFW Level Control Valve)

Tav 9 decreases from its initial value of 547°F to 542°F (just after RPS actuation)

Two (2) minutes prior to RPS actuation, measurable AFW flow to 12 S/G begins* (flow of 5.5x10 3 #/hr does not occur until one minute after RPS actuation) 1558 RPS Actuation - No. 12 S/G Low-Low Level; trip breakers open and shutdown banks insert APPARENT CAUSE OF OCCURRENCE:

The root cause of this event has been attributed to personnel. error.

The Nuclear Control Operator (NCO) did not ensure optimum initial conditions prior to swapping from No. 11 S/G to No. 12 S/G for maintaining RCS temperature. Subsequently, No. 12 S/G level continued to decrease, after the transfer, due to inadequate AFW flow with the trip setpoint eventually being reached. Contributing to this .event was inadequate command and control by the Nuclear Shift Supervisor (HSS) during the transient.

The NSS witnessed the entire evolution leading to the RPS actuation but did not-intervene to ensure that No. 12 S/G conditions were .

optimized prior to the transfer. The operating requirement for S/G level is 33%, with the operating margin between 28% and 38%.

Additionally, the NCO's poor methodology for the transfer was not

\ challenged. No aggressive intervention was applied to arrest and restore No. 12 S/G level.

The NCO did not terminate (and reverse) the decreasing level trend in No. 12 S/G prior to the transfer. In addition, the transfer was accomplished by matching demands and MSlO setpoints. A more appropriate method would have been to slowly transfer heat sinks

I LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUM_BER PAGE Unit 1 5000272 90-010-00 4 of 5 APPARENT CAUSE OF OCCURRENCE: (cont'd) while adjusting feed flow level and steaming rate based on indicated parameters.

After the transfer was accomplished, the No. 12 S/G level further decreased to the trip setpoint. The NCO made small incremental increases to AFW demand, despite indication of no flow and no change in the rate of No. 12 S/G level decrease. Also, the initially established steaming rate was not reduced to minimize the S/G mass inventory loss and halt the RCS Tavg decreasing trend until RPS setpoint actuation was impossible to avoid.

ANALYSIS OF OCCURRENCE:

The purpose of the S/G low-low level reactor trip is to prevent operation with the steam generator water level below the minimum

.volume required for adequate heat removal. The trip is actuated on two out of three low-low water level signals in any S/G. The setpoint ensures adequate inventory in the S/Gs, at the time of a reactor trip, to allow for any possible starting delays of the Auxiliary Feedwater Pumps {BAJ; thus preventing S/G dryout and the Reactor Coolant System

{ABf thermal and hydraulic transients that would be associated with a loss of the heat sink.

The Reactor Protection System (RPS) {JCI functioned as designed and the heat sink was maintained during this event. Since the RPS is designed to withstand the thermal and hydraulic effects of four-hundred (400) reactor trips from full power, the reactor trip while in Mode 3 resulted in a thermal transient well within the design limits of the system. This event involved no undue risk to the health or safety of the public. However, due to-the actuation of the RPS, this event is reportable in accordance with Code of Federal Regulations 10CFR 50.73(a) (2) (iv).

This was the first startup, of either Salem unit, with the S/G Low-Low Level trip setpoint.at 16%. The setpoint was changed from 8.5% to 16%

in January 4, 1990 as per Design Change Package lSC-2241. Discussions with the operators on shift during the event indicated that thi~

change di~ not contribute to the cause of this event.

During the event, the No. 12 Auxiliary Feedwater flow indication was not indicating the increased flow as the Operator increased demand on valve position. Investigation revealed that the Auxiliary Feedwater flow control valve had responded as designed. However, the "pot" for the instrument square rooter had failed. As a result of this failure, flow indication would not respond until flow reached 20%. The square rooter "board" was subsequently replaced. The failure of the flow indicator did not contribute directly to the cause of the RPS actuation.

CORRECTIVE ACTION:

Prior to subsequent operating shifts assuming the watch, this event

I LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 90-010-00 5 of 5 CORRECTIVE ACTION: (cont'd) was reviewed with them. Lessons learned from this event were stressed.

This event has been reviewed by Operations Department management and those personnel involved have been held accountable.

This event will be reviewed by the PSE&G Nuclear Training Center for incorporation into applicable training programs.

General Manager -

Salem Operations MJP:pc

. SORC Mtg.90-042