05000374/LER-1992-016

LER 92-016-01:on 921116,reactor Scram on Loss of Air Occurred.Caused by Inadequate Out of Svc Review & Lack of Administrative Controls.Procedures Revised & Individuals Involved counseled.W/930826 Ltr

ML20056G635
Person / Time
Site:	LaSalle
Issue date:	08/26/1993
From:	Enright D, Schmeltz J COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-92-016, LER-92-16, NUDOCS 9309030365
Download: ML20056G635 (7)

LER-2092-016,

Event date:
Report date:
3742092016R00 - NRC Website

text

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, Commonw::lth Edison LaSalle County Nuclear Station 2601 N. 21st. Rd.

Marseilles. lllinois 61341 Telephone 815/357-6761 August 26, 1993 l

U.S. Nuclear Regulatory Commission Attention: Document Control Desk Hashington, D.C. 20555

Dear Sir:

Licensee Event Report #92-016-01, Docket #050-374 is being submitted to your office in accordance with 10CFR50.73(a)(2)(iv).

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. V. Schmeltz i Acting Station Manager LaSalle County Station JVS/DJE/lja Enclosure xc: Nuclear Licensing Administrator NRC Resident Inspector NRC Region III Administrator INPO - Records Center IDNS Resident Inspector I

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' LICENSEE EVENT REPORT (LER) [

Form Rev 2.0 ;

Facility Name (1) Docket Number (2) Pace (3) i kaSalle County Station Unit 2 O!510101Of317!4 1 lof!0l5 Title (4) [

Peactor Scram On toss Of Air Due To An Inadecuate Out of Service Review i Event Date (5) LER Number (6) Reoort Date (7) Other Facilities Involved (8)

Year Sequential /jj// Revision f j Month Day Year /j//

ff f Month Day Year Facility Names Docket Number (s)  ;

/// Number /// Number ,

015101010131713  !

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l 11 1 11 6 91 2 91 2 0I1 16 011 0l8 21 6 91 3 Ol 51 O! 0101 I I I I

ONM THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10CFR [

(Check one or more of the followino) (11) 1 20.402(b) _ 20.405(c) JL, 50.73(a)(2)(iv) _ 73.71(b) i POWER _ 20.405(a)(1)(i) _ 50.36(c)(1) _ 50.73(a)(2)(v) _ 73.71(c)  !

LEVEL 20.405(a)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vii) Other (Specify 0 l0 i

(10) 1

_ 20.405(a)(1)Oii) _ 50.73(a)(2)fi) _ 50.73(a)(2)(vHi)(A) in Abstract '

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20.405an e 50.73(ax2n n o i HHHHHHHHHHHHB - _ _ 50.73(a>(2)(x) Text)

LICENSEE CONTACT FOR THIS LER (12)

Name TELEPHONE NUMBER f AREA CODE  !

Daniel Enricht. Doeratino Department. Extension 2204 8 1 1 15 31 51 71 -l 61 71 61  !

COMPLETE ONE LINE FOR EACH COMPON NT FAILURE DESCRIBE 0 IN THIS REPORT (13) l CAUSE SYSTEM COMPONENT MANUFAC- REPORTABLE  !

j/ CAUSE SYSTEM COMPONENT MANUFAC- REPORTABLE TURER TO NPRDS / TURER TO NPRDS A L1F l 1 l l l l N k i l i l I l l 1 I I I l l I / I I I l l 1 1 SUPPLEMENTAL REPORT EXPECTED (14) Expected Month i Day I Year  !

Submission lyes (If ves. complete EXPECTED SUBMISSION DATE) X l NO D# * (15) I !l !l {

AdSTRACT (Limit to 1400 spaces, i.e. approximately fif teen single-space typewritten lines) (16) i At 0122 on November 16, 1992. LaSalle County Station's Unit 2 scrammed from approximately 80% power following a load reduction f rom 100% power as a result of a feedwater transient that was caused by a loss of all }

Station Air (SA) Compressors.  !

Operating Personnel isolated cooling water to the Unit 2 SA Compressor as part of a scheduled Out of l

Service. This resulted in cooling water being isolated from the running Unit I and Common SA Compressors due '

to the Unit 2 Turbine Building Closed Cooling Water System (TBCCW) being cross-tied to the Unit 1 and Common SA Compressors while refuel outage activities were being perfonned on the Unit 1 TBCCW System.

Due to the loss of cooling water, the Unit 1 and Common SA Compressors tripped on high lube oil temperature.

This rest.lted in a reduction of Instrument Air pressure. The loss of air pressure, combined with its subsequent restoration, resulted in a feedwater transient that resulted in a Main Turbine trip due to high l reactor water level . The turbine trip caused a reactor scram.

The root cause of this event is an inadequate review of the Out of Service. A contributing factor to the  !

cause of this event is a lack of c.dministrative control over the abnormal lineup of the TBCCW Systems. The l procedure used for cross-tying the SA Compressor's cooling water to the other unit did not provide provisions for positive administrative control over this abnormal lineup nor did it provide provisions for alerting operating personnel that the abnormal lineup existed.

Corrective actions include counseling the individuals involved, and revising the procedure utilized for cross-tying SA Compressor Cooling Water to the other unit to provide provisions for positive control over this abnormal lineup. In addition, engraved plaques have been placed at the applicable SA Compressor Supply, Return, and Cross-Tie Valves to instruct operators to verify cooling water will be available to the required SA Compressors prior to repositioning them.

4 LICENSEE EVENT REPORT (LER) TEXT COWINUATf0N Fom Rev 2.0 FACILITY, NAME ('1) DOCKET NUMBrR (2) tER NUMBER (6) _

Pace (31 Year / Sequential f/j/j/ Revision j/j/j/

// Number /// Number LaSalle County Station Unit 2 015101010l31714 9l2 -

0I1 I6 -

O l1 Of 2 0F 01 5 TEXT Energy Industry Identificatien System (EIIS) codes are identified in the text as [XX)

PLANT AND SYSTEM IDENTIFICATION General Electric - Boiling Water Reactor Energy Industry Identification System (EIIS) codes are identified in the text as [XX).

A. CONDITION PRIOR TO EVENT Unit (s): 2 Event Date: 11/16/92 Event Time: 0122 Hours Reactor Mode (s): 1 Mode (s) Name: Run Power Level (s): }H B. DESCRIPTION OF EVENT LaSalle County Station Unit 2 scrammed from approximately 80% power as a result of a transient that was caused by a loss of all Station Air Compressors (SA) [LF).

The following is a list of events that lead up to and resulted in the scram of Unit 2 from approximately 900 megawatts on November 16, 1992.

On October 5,1992, the Unit 2 Turbine Building Closed Cooling Water (TBCCW) (WT) [KB] System was cross-tied to the Unit 1 and Comon SA Compressors in accordance with Step F.4 of LOP-WT-02 "Startup and Operation of the Turbine Building Closed Cooling Water System". This was perfomed in order to provide cooling to the Unit I and Comon SA Compressors while the Unit : TBCCW System was shutdown for refuel outage activities. Administrative Out of Service (005) 1-0705-91 was hung at this time to provide control over the cross-tying operation, and to ensure that the Un.t 1 SA Compressor TBCCW Supply and Return Valves remained closed to prevent connecting the running Un t 2 TBCCW System to the shutdown Unit 1 TBCCW System. In addition to hanging 005 cards on the Unit 1 SA Compressor TBCCW Valves 005 cards were hung on the Unit 1 TBCCW Pump Control Switches.

On November 14, 1992, the Operating Department comenced actions to return the Unit 1 TBCCW System to operation. TBCCW System Electrical and Mechanical Lineup Checklists were started and completed on Sunday, November 15. It was noted by the Equipment Attendant (EA, non-licensed) perf oming Mechanical Checklist LOP-WT-01M, that the SA Compressor TBCCW Cross-Tie Stop Valves OWT098 and OWT099 were open, and that the Unit 1 SA Compressor TBCCW Supply and Return Valves 1WT106 and 1WT107 were 005 closed.

Administrative DOS 1-0705-92 was cleared in order to return the Unit 1 TBCCW Pumps to service for system startup. The Unit 2 TBCCW System was to be lef t cross-tied to the Unit 1 and Common SA Compressors until it could be verified that the system was operating properly, and that there were no plans to shutdown the Unit 1 TBCCW System again. The Unit 1 TBCCW System was started on Sunday, November 15.

At approximately 0015 on November 16, the Operating Shift Crew began hanging 005 2-2202-92 on the Unit 2 SA Compressor in accordance with an established schedule for planned maintenance. Although the Operating Supervisors on shift were aware that the Unit 2 TBCCW System was supplying cooling to the running Unit 1 and Comon SA Compressors, they were not aware of the fact that 005 2-2202-92 included closing Unit 2 SA Compressor TBCCW Supply and Return Valves 2WT106 and 2WT107, which would isolate cooling water to all SA Compressors due to the cross-tied lineup in place at the time.

' t LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Form Rev 2.0 i FACILITY,NAME (1) DOCKET NUMBER (2) LER NUMBER (6) Pace (3) f Year Sequential Revision j g/// Number g//

/ Number -

Ldalle County Station Unit 2 0 l S 1 O l 010131714 9I2 -

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O l1 01 3 0F 01 S TEXT Energy Industry Identification System (EIIS) codes are identified in the text as [XX]  !

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B. DESCRIPTION OF EVENT CONTINUED i

At approximately 0115, EAs assigned to hang 005 2-2202-92 closed Unit 2 SA Compressor TBCCW Supply and l Return Valves 2WT106 and 2WT107 (located in the Unit 2 SA Compressor Room) in accordance with the 005 i checklist and proceeded to the Unit 1 SA Compressor Room to continue hanging the 005. The EAs found the [

cross-tie valves OWT098 and OWT099 open which they had not expected, and lef t to call the Control Room.

At approximately 0118, the Unit 1 SA Compressor tripped followed approximately one minute later by a trip of the Comon SA Compressor, both tripping due to high lube oil temperature. The EAs were made aware of the SA Compressor trips via a plant page made by Control Room Personnel, and imediately took actions to restore cooling to the SA Compressors and return them to operation.  !

k Upon receiving the SA Comprsssor trip alarms, Control Room Personnel imediately observed indications of  ?

decreasing Instrument and Service Air Pressures. The Shif t Engineer (SE, licensed SRO) and Shif t i Supervisors (SS, licensed SRO) reported to the Control Room. The Unit 2 Nuclear Station Operator (NSO, licensed RO) began reducing reactor power from 100'4 by reducing reactor recirculation (RR) [AD] flow. A reactor water level transient began due to the reduction in Instrument Air (IA) [LD) Pressure which caused: the 2B Turbine Driven Reactor Feed Pump (TDRFP) (FW) [JK), which was in manual, to stop pumping due to a loss of control air pressure; the Feedwater Minimum Flow Valves to fall open; and the Heater Drain (HD) [$M] Pump Forward Valves to fail closed. The extra NSO in the Control Room took a position  !

at the Feedwater Control Panel to respond to the transient. The 'A' TDRFP, which was in three element control continued to pump water to the reactor, and the Motor Driven Reactor Feed Pump (MDRFP) was manually started due to the loss of flow from the 'B' TDRFP and the decreasing reactor water level.

Instrument Air Pressure decreased to approximately 60 psig before the SA Compressors were restarted.  !

The Control Room personnel utilized LOA-IA-01 " Loss Of Instrument Air", and LOA-SA-01, " Loss Of Service  !

Air", during the transient. Upon restoration of instrument air, the 'B' TDRFP began to pump to the reactor again until it was manually tripped due to increasing reactor water level. In addition, the Feed Pump Minimum Flow Valves went closed and the Heater Drain Pump Forward Valves went open due to the restoration of Instrument Air Pressure, both contributing to a high reactor water level condition. The operation of the Feedwater and Heater Drain System components was consistent with the reduction and f

restoration of air pressure.

l, At approximately 0123, the Unit 2 Main Turbine (TG) [TA] tripped due to high reactor water level (Level '

8, 45S.S" reactor water level) which resulted in a reactor scram due to Turbine Stop Valve (EH) [TG) closure. Reactor water level reached a maximum level of approximately +60", followed by a decrease of  !

level to a minimum of approximately +2" caused by " shrink" during the turbine trip and scram pressure I transient. This resulted in a reactor low level scram .ignal (Level 3, +12.S"). Recovery actions from  ;

the scram were nonnal and reactor parameters were stabilized.

Af ter the scram, the "U" Safety Relief Valve (SRV) (NB) [AD), which is a Group 1 Safety Relief Valve, lifted. Group 1 Safety Relief Valve's have the lowest relief pressure settings and would be 1xpected to lift first during a pressure transient. Review of the pressure transient indicates that the Safety f Relief Valve operated consistert with its design setpoint.

During the transient the Reactor Core Isolation Cooling System (RCIC) (RI) [BN] initiated due to an l instrument rack pressure spike which caused an invalid low reactor level (Level 2 - S0") to be sensed. }

The RCIC Turbine was imediately tripped by the NSO in the Control Room before the system injected into  ;

the reactor vessel. The level spike resulted from pressure waves traveling from the Turbine Control and j Stop Valves up the steam lines into the Reactor Pressure Vessel Dome. General Electric, the Nuclear I Steam Supply Syste.n (NSSS) Supplier, has indicated that these spikes are expected and were present on i the initial cycle startup tests.

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_ LICENSEE EVENT REPORT (LER) TEXT CONVINUATION Fom Rev 2.0 FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) Paoe (3)

Year // Sequential /j/j/ Revision j/jj/

// Number f

/// Number LaSalle County Station Unit 2 015 i 0 l 010 l 317! 4 912 - 0I116 -

0 11 01 4 0F 01 5 TEXT Energy Industry Identificatioe System (EIIS) codes are identified in the text as [XX)

B. DESCRIPTION OF EVENT CONTINUE 0 It should be noted that Unit 1 experienced the same reduction in Instrument and Service Air Pressures  ;

during the event. However, Unit I was in its fif th refuel outage with the reactor defueled at the time, ,

and experienced no adverse consequences.

This event is reportable pursuant to the requirement of 10CFRSO.73(a)(2)(iv) due to the automatic actuation of the Reactor Protection System (RPS) (RP) [JC).

C. APPARENT CAUSE OF EVENT The cause of this event was the reduction in Instrument Air pressure which caused a Feedwater transient. This resulted in a trip of the Main Turbine due to high reactor water level and a subsequent reactor scram.

The loss of, Instrument Air pressure was the result of trips of the two running SA Compressors due to high lube oil temperature as a result of the loss of all cooling water.

The loss of all cooling water to the SA Compressors was caused by the closure of the Unit 2 SA Compressor TBCCW Supply and Return Valves by Operating Personnel as part of a scheduled 005 while the Unit 2 TBCCW System vai cross-tied to supply cooling water to the Unit 1 and Coninon SA Compressors.

This was caused by a lack of realization on the part of the preparers and the personnel hanging OOS e 2-2202-92 that closing these valves would isolate cooling water to the running SA Compressors.  !

The Out of Services at LaSalle Station are prepared by qualified individuals well in advance of the time they will be actually utilized. This methodology allows a thorough review, without any time pressure,  :

to ensure that the equipment will be properly isolated. When the Out of Service is to be hung, the unit supervisor reviews the equipment being removed from service to ensure that it is not required for plant operations.

The root cause of this event was an inadequate review of the Out of Service. In this event, the Out of Service was written assuming a normal cooling water line-up. The preparer did not identify the possible impact of the Out of Service if the cooling water was in a non-normal configuration. When the Out of Service was hung, the unit supervisor was aware of the abnormal configuration, but not how this would be affected. Because no previous dif ficulties have been experienced as a result of the interaction between l two off normal conditions, the individuals did not put enough detail into their reviews to prevent the probl em.

D. SAFETY ANALYSIS OF EVENT Turbine trip with bypass is classified as a transient of moderate frequency in Chapter 15 of the Update  ;

Final Safety Analysis Report (UFSAR). The turbine trip in this event initiated the reactor scram as required. Following the scram, reactor pressure was controlled by the Safety Relief Valve and Turbine Bypass Valves. These events are consistent with the UFSAR analysis of this event. ,

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LICENSEE EVENT REPORT (LERI VEXT CONTfNUATION Form Rev 2.0 FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) Paoe t3) l Year /// Sequential /// Revision j jjj/

// Number j///

ff Number LaSelle County Station Unit 2 015101010131714 912 - 0I1I6 -

0 11 01 5 0F 01 5 i VEXT Energy Industry Identification System (EIIS) codes are identified in the text as [XXJ D. SAFETY ANALYSIS OF EVENT CONTINUED  !

Safety features were initiated as designed and expected, with the exception of the RCIC System initiation which occurred due to a pressure spike sensed in the variable leg of its associated level  !

instruments. ,

E. CORRECTIVE ACTIONS >

The individuals involved have been counseled on the need to thoroughly consider the effects of their actions, j All Shif t Supervisors have been briefed on the need to ensure that they have thorough understanding of (

the ef fect of Out of Services hung on their shif t. ,

All Out of Service preparers have been counselled on the need to consider the effects of boundary isolations on systems where there is more than one design configuration. Where such configurations exist, the need for a heightened level of review will be clearly identified on the Out of Service before j it is delivered to the shift supervisor. j i

LOP-WT-02 "Startup and Operation of the Turbine Building Closed Cooling Water System" will be revised to I include provisions for positive control and to alert operators of the abnormal cross-tied lineup of the SA Compressor TBCCW by means of established station administrative methcds and procedures. Action Item Reccrd (AIR) 374-180-92-08201 will track procedure revisions.

Engraved plaques have been installed at each of the applicable SA Compressor TBCCW Supply, Return, and Cross-tie Valves (lWT106,1WT107, 2WT106, 2WT107, OWT098, and OWT099) instructing operators to verify that coolirg will be available to the required SA Compressors prior to repositioning them. AIR -

374-163-92-08202 will track completion of the installation of the engraved plaques. l A letter will be sent to all Shif t Engineers with system procedure assignments asking them to review their systems for similar physical configurations that could result in inadvertent system / unit crossties. AIR 374-180-92-08233 will track completion of these reviews.

F. PREVIOUS EVENTS A search of the LER/DVR data base indicated no previous similar events.

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G. COMPONENT FAILURE DATA None.

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