05000305/LER-1985-001, :on 850122,inadvertent Actuation of Internal Containment Spray Sys 1B Occurred,Discharging Approx 2,500 Gallons Borated Water Into Containment Bldg.Operator Secured Sys & Reset Containment Spray

:on 850122,inadvertent Actuation of Internal Containment Spray Sys 1B Occurred,Discharging Approx 2,500 Gallons Borated Water Into Containment Bldg.Operator Secured Sys & Reset Containment Spray

ML20107G070
Person / Time
Site:	Kewaunee
Issue date:	02/21/1985
From:	Hintz D, Pulec R WISCONSIN PUBLIC SERVICE CORP.
To:	NRC OFFICE OF ADMINISTRATION (ADM)
References
CON-NRC-85-29 LER-85-001, LER-85-1, NUDOCS 8502260292
Download: ML20107G070 (5)

LER-1985-001, on 850122,inadvertent Actuation of Internal Containment Spray Sys 1B Occurred,Discharging Approx 2,500 Gallons Borated Water Into Containment Bldg.Operator Secured Sys & Reset Containment Spray

Event date:
Report date:
3051985001R00 - NRC Website

text

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l l'l Ae871ACT (Omst so 7400 apsres, ie seeresamerswy Mvsea omgwe spece typewertsoa poet Het At 1437 on January 22, 1985, during full power oper.ition, there was an inadvertent actuation of the IB Internal Containment Spray Systim. The IB pump ran for 1 minute and 40 seconds discharging an estimated 2500 gallons of borated water into the containment building before being secured. The pump start occurred during the per-fonnance of SP55-155, " Engineered Safeguards Logic Test".

When the pump start occurred, the operator verified that it was inadvertent, secured the system and reset containment spray. The operators received various battery ground alarms as a result of instrument malfunctions in containment.

At 1525 it was discovered that the RWST level was below technical specification limits, refilling was started and preparations were made to begin a-plant power reduction.

The TWST level was above TS setpoint at 1555 hence no reduction in power was initiated.

Immediate actions were taken to assess the situation and identify the cause. Long term actions planned are to clean the containment interior, and perform an evaluation

' to identify potential hardware modifications which would prevent reoccurrence.

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.,im o 1510 lo lo l l l 8l5 0 l 0l1 0 10 0 12 0F 0h At 1437 on January 22, 1985, during full power operation, there was an inadvertent actuation of the IB Internal Containment Spray System [ICS] (BE).

The 1B pump (P) ran for 1 minute and 40 seconds discharging an estimated 2500 gallons of borated water into the containment building before being secured. The pump start occurred during the performance of SP55-155 " Engineered Safeguards Logic Test". This test is perfomed monthly to satisfy plant Technical Specification requirements.

Each safeguards logic train is tested individually. A contact is opened to prevent the slave relay on the train in test from being energized by the master relay.

By procedure the I & C personnel are to monitor the computer printout, the sequence of events recorder points, annunciators and/or trip status lights and the test lamps or permissive status lights actuated by the procedure.

When the pump start occurred the operator verified that it was inadvertent, secured the system and reset containment spray. The operators received battery ground alarms (ALM) as a result of instrument malfunctions in containment. Among the alarms received were 1A RCP fire protection, 1B RCP upper bearing temperature, and rod deviation alarms.

At 1525 it was discovered that the Refueling Water Storage Tank (BQ) level was below Technical Specification limits. Refilling was started and preparations were made to begin a plant power reduction. The RWST was above TS setpoint at 1555 hence no reduction in power was initiated.

AT 1610 a containment entry was made by Operations personnel and plant electricians.

They found pools of water at all elevations of containment that were evaporating and leaving boric acid residue.

Everything else appeared normal with no visible evidence of ground faults.

At 1742 the operators completed SP87-125 " Shift Turnover Channel Checks". All of the parameters were normal and within specification. The only abnormal conditions at that time were battery grounds of 60 volts negative on "B" battery,120 volts positiva on "A" battery, a 1A RCP fire alam which was shown to be invalid during the visual inspection, a high containment humidity indication, a mid-position indication of the emergency airlock inner door switch, and an abnormal RCP upper Radial BRG temperature indication. The last two abnormal conditions were due to water intrusion.

At 2040, indication for control rod (AA).K-7 in Bank D began behaving erratically. All~

cther core conditions showed normal behavior and the rod position indication;for rod K-7 was declared out of service.

A review of the surveillance procedure perfomance was initiated to identify the cause of the actuation. From the Sequence of Events Recorder printout, it was discovered that during the performance of the containment Hi pressure logic testing, the Hi-Hi containment pressure alarm actuated twice. This Hi-Hi containment pressure bistable (IS) actuation durin~g the test on the Hi containment pressure ligic is attributed to an interaction between the-two bistables, referred to as cross-talk. This is possible because the Hi and the Hi-Hi containment pressure actuation circuitry are contained in the same duplex bistable unit. The problem of cross-talk has been detected before and Na Fomu 3esa

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This cross-talk may have resulted in energizing the Containment Spray Master Relay (RLY).

At the end of the procedure, when safety injection was reset, the slave relay was energized and the IB ICS pump actuated.

A retest was perfomed two days after the event in an attempt to reproduce the occurrence.

In two of seventeen attempts Hi-Hi containment pressure alarmed during testing of the Hi containment pressure channel.

In addition, recorders were set up to monitor the coils on the bistable outputs.

Fluttering of the de-energized bistable was otserved. This evidence indicates that cross-talk may have occurred, but is not conclusive as to the cause of the pump start. Additional testing is planned during the in-progress 1985 refueling outage.

A related event occurred on February 10, with the plant in cold shutdown and RCS pressure at approximately 320 psig. The control room operator noticed that the 1B Reactor Coolant Pump (AB) had started without swtich action. Upon discovery the operator secured the pump and started the associated oil lift pump. Residual water (believed to be from the-ICS actuation) discovered in the pump pressure switch housing had grounded the RCP 4160V breaker SCR circuitry sending a close signal to the breaker and starting the pump.

(ReferenceLER85-04).

CORRECTIVE ACTIONS

The following actions were taken:

1) The NSSS vendor (Westinghouse) and the A/E (Fluor Engineers) were contacted immediately to aid in the evaluation of the incident. The effects of the spray on equipment operability and potential for Boric Acid and Na0H corrosion of metal components was considered. The decision was made to remain at full power.

2) Chemistry samples were taken to determine the amount of caustic discharged to containment. The results were a PH of 6.8 in the spray discharge line and a PH of 5.9 in the Refueling Water Storage Tank.

3) The Operations Superintendent routed a letter to the operating crews alerting them to potential problem areas based on conversations with Westinghouse. These areas are:

the reactor coolant pumps, nuclear instrumentation, individual rod position indication and limit switch indication.

4) A valve timing test was performed on the air operated containment isolation valves within containment. All:were within specification.

6) k. following day the IB ICS piping was flushed to remove caustic in the system and the lines were sampled to ensure the caustic was flushed.

6) A core flux map was performed which confimed that control rod K-7 was at its normal bank position.

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7) On January 24, the Safeguards Logic Test was repeated to aid in identifying the cause of the pump start. The results were not conclusive.

8) Our initial review of the RCP start (breakaway measurements, vibration measurements, and thrust bearing temperatures) indicated that no damage occurred. (Reference LER85-04).

Long term actions planned are:

1) Cleanup the residual boric acid crystals.

2) Perfonn further testing on the safeguards actuation logic during refueling.

3) Monitor reactor coolant pump performance during startup.

4)

Inysstigate replacing the duplex bistables used in the energize to actuate applications.

5) Perfonn a random check on insulated carbon steel lines inside containment to ensure no boric acid is on the piping.

SAFETY CONSEQUENCES

The immediate concerns following this event were proper operation of equipment. The containment tour verified that there was no major problems and abnormal instrument indications could be attributed to water instrusion.

The other concernwas possible corrosion of carbon steel co;nponents covered by mineral based insulation material when exposed to boric acid solution. According to infonnation received from Westinghouse, when the solution evaporates boric acid crystals are left; as long as the crystals remain unwetted there should be no short nr medium term corrosion concern. However, because of the design of the insulation and the high operating temperature of the carbon steel components it is unlikely that the solution came in contact with the components.

Containment humidity returned to normal conditions, (the 15-20 percent range) by 1937

n January 22 indicating that the water inside containment looked dry, with boric acid crystals coating exposed surfaces.

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NRC-85-29 WISCONSIN PUBLIC SERVICE CORPORATION P.O. Box 1200, Green Bay, WI 54305 February 21, 1935 U. S. Nuclear Regulatory Comission Document Control Desk Washington, D.C.

20555 Gentlemen:

Docket 50-305 Operating License DPR-43 Kewaunee Nuclear Power Plant Reportable Occurrence 85-001-00 In accordance with the requirements of 10 CFR 50.73 " Licensee Event Report System",

the attached Licensee Event Report for reportable occurrence 85-001-00 is being submitted.

Very truly yours,

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D. C. Hintz Manager - Nuclear Power JGT/js Attach.

cc - INP0 Records Center Suite 1500,1100 Circle 75 Parkway Atlanta, GA 30339 Mr. Robert Nelson,' NRC Resident Inspector Mr S k.

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