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March 20, 1991

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10CFR$0.73

Docket No. 50 461

Nacicar Regulatory CommissionDocument Control DeskWashington, D.C. 20555

Subject: Clinton Power Station Unit 1Licensee Event Rengrt No. 91 002 00

Dear Sir:

Picase find enclosed Licensee Event Report No. 91 002 00:Complete Loss of Service and instrument Air Due t o__ Eculpment Failureand Personnel Error Resulted in Manual SCRAM Insertion to Minimizethe Loss of Reactor Vessel Inventory. This report is being submittedin accordance with the requirements of 10CFR50.73.

Sincerely yours,

,i/

l8b 4A. A. Spangenbe g, Ill

Manager, Licensing and Safety

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Enclosure

ec: NRC Resident OfficeNRC Region III, Regional Administra- -

INPO Records CenterIllinois Department of Nuclear Safe ,

NRC Clinton Licensing Project Manager

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On February 18.-1991, with the plant in Mode 4 (COLD SilUTD0i'N), with thenumber 2 Service Air (SA) compressor in service maintaining header airpressure at 106 pounds per square inch gauge, the number 1 Sn compressor

L automatically started and loaded. Control room instrumentation showedthe running current of both SA compressors to be approximately the same,thus leading the o, to believe that both SA compressors wereoperating and loaded. . prevent equipment damage, the operators shutdown the number 1 SA wompressor. This action resulted in a complete losscf SA and Instrument Air. SCRAM valves started to drift open tesultingin leakage from the reactor vessel to the scram discharge volume.deactor vessel level decreased from 79 inches to 74 inches. The flow of

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| condensate water to the vessel stopped; however, Emergency Core Cooling|. Systems remained capable of supplying makeup to the reactor vessel. To

j minimize the loss of vessel inventory, a manual SCRAM signal wasinserted. The SA system was returned to service and air header pressurej.

' was reestablished within 35 minutes. The cause of the event isattributed to equipment failure compounded by personnel error.Corrective cetion consisted of immediately issuing a priority oneMaintenance Work Request to return the SA compressor to operation. Theoperating shift crews have been informed of this event.

NRC Form 3Ds "' 500

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DESCRIPTION OF EVENT

*At 0325 hours on February 18, 1991, the plant was in OperationalCendition 4 (COLD SHUTDOWN), with the reactor (RCT) coolant temperature

00 degrees Fahrenheit and at atmospheric pressure. The Number 2n

brvice Air System (SA) (LF) compressor (CMP), 2SA010, was in operationand maintaining a steady output at 106 pounds por square inch gauge(PSIG) when on rumber 1 Service Air compressor,1SA010, automaticallystarted and Icaded. _The Auto Start annunciator (ANN) P800 63A 6Benergized indicattng automatic start of the number 1 Service Aircompress w.

- Control roon, indiddorr 'II) showed the running current of Service Aircompressor 1SA01C to bw opproximately the same as the running amps ofSer.' ice Air-compressor 2SA010. Service Air header pressure was 108 psig,

;- tL upper limit of the normal range. To prevent system damage and todetermine _ if Servico Air compressor 2SA01C was capable of carrying the,ystem load requirements to meet system demands, a joint decision was

ide by the utility licensed Control Room Operator (CRO) and by thearations Line Assistant Shift Supervisor (LASS) to shut down Serviceir compressor 1SA01C. The Shift Supervisor concurred with this

cecision. Subsequently, Service Air compressor 1SA01C was shut down.Immediately upon shutdown of Service Air compressor 1SA01C, air headetpressure decreased rapidly. During depressurization of the air header,Service Air compressor 2SA01C indication showed that running ampsremained at approxinstely 70 amps. No Instrument Air (IA) (LO) orService Air system hunder isolation annunciators were energized at thistime.

-IA/SA system header pressure continued to-decrease. An attempt was madeto restart Service Air compressor ISA01C when header pressure reached 100psig,. decreasing, The attempt to start _ Service Air compressor 1SA01C wasunsuccessful; amps reached the maximum indicated value then decreased tozero and the 1SA01C breaker (SKR) tripped, Service Air compressor 1SA010

. surged and tripped because of the rapidly decreasing system pressure.The breaker trip of Service Air compressor 1SA01C was followed by thebreaker trip of Service Air compressor 2SA01C.

When air header pressure reached 70 psig, the annunciator for " TroubleInstrument' Air Dryer" energized. The Operations Staff Assistant Shif tSupervisor (SASS) and the utility Non-Licensed "D" Area Operator weredispatched to the Service Air compressors for the purpose of starting anair compressor. %naurrently with this activity, at 0327 hours, a SCRAMdischarge volun< high alarm ( AL) was printed on the alarm typt e. Thisalarm indicate that containment IA pressure was less than 60 psig andthat SCRAM vaivos (V) were starting to drift open. Additionally, venti.

| and drain volves on the SCRAM discharge volume were in their normalposition, open, providing a flow path allowing reactor water to drain

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through the SCPAM discharge volume. Reactor vessel level decreasedapproximately Jive inches from 79 inches to 74 inches on the shutdown

,*range. Coniensate [SD] pump [P) 1D had been operating in short cycle.

.The loss of IA pressure caused all condensate and booster pump minimumflow valves to fail open per design. - As a result of the loss of 1A,condensate pump 1D vaa eihut down at 0328 hours to prevent pump run out.

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At this time, all normal methods of vessel makeup were lost. EmergencyCore Cooling Systems remained capable of supplying makeup to the reactor-vessel-throughout the event.

At 0330 hours, based on recommen tations of the CRO and of the IASS, theOperations Shift Supervisor directed that a manual SCRAM be initiated tominimizo loss of reactor inventory. At this time and over the nextseveral minutes, the following heating, ventilation and air conditioningsystems automatically shut down as a result of the IA system pressureloss:

Fuel Building lleating, Ventilation and Air Conditioning (VF)*

[VG)Turbine Building ileating, Ventilation and Air conditioning*

(VT) [VK)Laboratory llenting, Ventilation and Air Conditioning (VL)*

Radwaste Building lleating, Ventilation and Air Conditioning*

(VW) [Vii) .

Machine Shop ileating, Ventilation and Air conditioning (VJ)*

Containment Continuous Purge-system (CCP)*'

Station off-normal pr * dure CPS 4004.01, " Instrument Air Loss," was m

referred to by the .:lons crew during this event. Applicabicsutomatic actions s * verified to have occurred, per design.Additionally, the Shift Supervisor initiated a priority one emergencywork request to repair a Service Air compressor.

. Operations Non Licensed Operators attempted to restart each of the three1 compressors but, due to misinterpretation of procedural steps, they wereunsuccessful after each attempt. Subsequently, at 0400 hours, ServiceAir Compressor 2SA01C was restarted.

At 0418 hours, CCP ventilation and VF ventilation systems were restored.At 0440 hours, condensate pump 1D was started to reestablish a normalmethod for reactor vessel-makeup.

No other automatic or manually initiated safety system responses werenecessary to place the plant in a safe and stable condition. No other

l; equipment-or components were inoperable at the time of the event such.

that their inoperable condition contributed to this event.

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CAUSE OF SVENT

*Tl'e cause of this event was attributed to equipment failure compounced by

pe.'sonnel error. On February 17, 1991, Control and Instrumentation (C&l)tec)nicians performed work on Service Air compressor 2SA01C underMaintenance Work Request (MWR) D16908. During performance of this work,the surge suppression switch was recalibrated. Post maintenance testingincluded operating Service Air compressor 2SA010 at the completion ofwork associated with MVR D16908. The compressor ranintained a steadyoutput within the normal operating range. Service Air compressor 2SA010remained running and Service Air compressor 1SA010 was placed in Standby.

The compressors remained in this configuration until Service Aircompressor 1SA010 automatically started and loeded on February 18, 1991.Based on running amperage indications provided in the contrcl room, i.e.,

both compressors-indicating approximately 70 amps, the Operations crewsecured Service Air compressor 1SA01C without first determining thereason'that Service Air compressor 1SA01C automatically started.Subsequent investigation showed that Service Air compressor 2SA01Cunloaded due to a surge suppression switch which had not been calibratedin accordance with the most recent recommendations contained in themanufacturer factory service manual update. This condition wasidentified by a utility C&1 technician who had attended external trainingon maintenance and repair of the Service Air compressors. Investigationshowed that this updai.e to the manufacturer factory service manual hadnot been previously sent to Illinois Power Company by the manufacturer.Additionally, the inlet valve on Service Air compressor 2SA01C failed togo from full open to its minimum position, approximately 40 percent open,when 2SA01C unloaded, The inlet valve positioner was determined to bebroken. .Rttnning current was not reduced since a flow path existed fromthe inlet valve through the blowdown valve. This provided Control RoomOperators with a misicading indication as to which Service Air compressorwas actually loaded.

Subsequently, MWR D16908 was revised and reissued to Maintenancepersonnel to perform additional work on Service Air compressor 2SA01C.Numerous compressic.n fittings on air lines located under the compressorskid were found to be loose and leaking excessively. Leakage of thecompressor air line compression fittings is attributed to normal

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compressor vibration over an extended period of tine. Excessive Icakagefrom compression fittings in addition to normal system demands may have

-resulted in the surge suppression switch sensing a pressure surge versusan increase in pressure demand. The major equipment problems noted onthe Service Air compressor were the surge suppression switch which wasnot operating correctly, excessive leakage through compression fittingson the air lines and the inlet valve positioner which was not

'functioning.

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Shutdown of Service Air compressor 1SA01C by Operations personnel withoutdetermining the reason for the automatic start resulted in securing the ,*

only Service Air compressor providing air supply to the SA/IA header.This caused air header pressure to drop to zero psig.

The duratiot, of the event was extended due to Operations non licensedpersonnel misinterpretation of procedural requirements contained instation procedure 3214.01 while attempting to restart the pre lube pumpsfor Service Air compressors. Specifically, the Service Air compressorpro-lube pumps failed to start because insufficient control air pressurewas supplied to the control panel, Additionally, personnel errorresulted in the isolation of an air dryer to Service Air compressor2SA01C due to a misinterpretation of procedural requirements.

CORRECTIVE ACTION

The Operations crew has recognized their errors associated with theshutdown of Service Air compressor 1SA01C without thoroughlyinvestigating and determining the cause for the automatic start.Additionally, the area operator has recognized his errors associated withthe procedural misinterpretations including isolation of the air dryers.

The Operations shift crews have been informed of this event through theissuance of an Operations Night Order.

The surge suppressior, switch on Service Air compressor 2SA010 has beenrecalibrated utilizing the most current methodology contained in themanufacturer factory service manual. Compression fittings on thecompressor air' lines have been tightened to eliminate leakage, This workhas been completed under HWR D16908.

The surge suppression switch on Service Air compressor OSA01C has beenrecalibrated utilizing the most current methodology contained in the

; manufacturer factory service manual. Excessive dirt has been removedfrom the control components. Compression fittings on the compressor havebeen checked for tightness. This work has been completed under MWRD17204.

The preventive maintenance program for the Service Air compressors willha anhanced to provide specific calibration requirements incorporating

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guidance of the manufacturer factory service manual. Additionally, thepreventive maintenance program will address requirements to improvecleanliness of the control components associated with Service Aircompressors. Secureness of air line fitt.ings will be checked duringperiodic preventative maintenance. This revision to the preventivemaintenance program is expected to be completed by July 7, 1991.

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Calibration of the surge suppression switch and removal of excessive dirtfrom the control components, if applicable , on Service Air compressor

*1SA010 has been scheduled and will be completed by April 30, 1991.

Annuntiator procedure 5041.06B, " Auto Start Service Air Compressor", willbe revised to change operator action number 2. The revision will requirean area operator be dispatched to the affected Service Air compressor i

skid to determine the cause as indicated by local panel status lights andvalve positions. This action is expected to be completed by May-15,1991.

Station procedure 3214.01 will be revised for clarity of initial startupof Service Air compressors with the Service Air system decreased to zeropsig. This action is expected to be completed by April 30, 1991.

Training will be provided to Operations Non, Licensed.Operat. ors on the-revisions of station crocedure 3214.01. This training will beaccomplished during requal.,1 cation training and vill be completed byAugust 16, 1991.

ANALYSIS OF EVENT

This event is reportable under the provisions of 10CFR50.73(a)(2)(iv) dueto a manual actuation of a reactor protection system.

Assessment of the safety consequences and implications of this eventindicates that the event-was not safety significant for existing plantcondit!;ns or other plant modes and power levels. The Service Air andInstrument Air systems perform no nuclear safety related functions.Events resulting from the loss of the Instrument Air system have beenanalyzed in Chapter 15 of the-Updated Safety Analysis Report and-theresulting transients were determined to be within limits of the plant.

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ADDITIONAL INFORMATION

*The Service Air compressors discussed in this 1,1censee Event Report were i

manufactured by-Ingersoll-Rand, Model Number 1C25M4,

No Licenaee Event Reports have been. issued at Clinton Power Station for asimilar event.

For additional-information regarding this event, contact P. D. Yocum,Director - Plant Operations at (217) 935-8881, extension 3205.

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