05000339/LER-1981-062-03, /03L-0:on 810810,inadvertent Actuation of ECCS Train B Occurred,Resulting in Borated Water Concentration in Injection Tank Dropping Below Tech Spec Limit.Caused by Defective Low Pressurizer Reset & Block Switch

/03L-0:on 810810,inadvertent Actuation of ECCS Train B Occurred,Resulting in Borated Water Concentration in Injection Tank Dropping Below Tech Spec Limit.Caused by Defective Low Pressurizer Reset & Block Switch

ML20010F723
Person / Time
Site:	North Anna
Issue date:	09/02/1981
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20010F718	List: 05000339/LER-1981-062, Forwards LER 81-062/03L-0 05000339/LER-1981-062-03, /03L-0:on 810810,inadvertent Actuation of ECCS Train B Occurred,Resulting in Borated Water Concentration in Injection Tank Dropping Below Tech Spec Limit.Caused by Defective Low Pressurizer Reset & Block Switch
References
LER-81-062-03L-01, LER-81-62-3L-1, NUDOCS 8109110240
Download: ML20010F723 (3)

LER-1981-062, /03L-0:on 810810,inadvertent Actuation of ECCS Train B Occurred,Resulting in Borated Water Concentration in Injection Tank Dropping Below Tech Spec Limit.Caused by Defective Low Pressurizer Reset & Block Switch

Event date:
Report date:
3391981062R03 - NRC Website

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U.S. NUCLEAR REGULATORY COMMISSION i

LICENSEE EVENT REPORT CONTROL BLOCK / / / / / / / (1)

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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/V/A/N/A/S/2/ (2)

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LICENSEE CODE LICENSE NUMBER LICENSE TYPE CAT

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I DOCKET NUMBER EVENT DATE REPORT DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES (10)

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/ On August 10, 1981, during Mode-3 operation, an inadvertent actuation of Train B /

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/ of the Emergency Core Cooling System occurred.

This actuation caused the borated /

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/ water concentration in the Boron Injection Tank to drop below the minimmr re-

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/ quired by T.S. 3.5.4.1.

Since this was an inadvertent actuation, the health and /

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/ safety of the public were not affected. This event is reportable pursuant to

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/ T.S. 6.9.1.9.b. an( the special reporting requirement of T.S. 3.5.2.

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i SYSTEM

CAUSE

CAUSE COMr.

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CODE CODE SUBCODE COMP 0NFNT CODE SUBCODE SUBCODE

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/S/F/ (11) /E/ (12) /A/ (13) /C/K/T/B/K/R/ (14) /E/ (15)

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SEQUENTIAL OCCURRENCE REPORT REVISION LER/R0 EVENT YEAR REPORT NO.

CODE TYPE NO.

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ACTION FUTURE EFFECT SHUTDOWN ATTACHMENT NPRD-4 PRIME COMP. COMPONENT TAKEN ACTION ON PLANT METHOD HOURS SUBMITTED FORM SUB. SUPPLIER MANUFACTURER g/ (18) LA/ (19) [C/ (20) LZ/ (21) /0/0/0/0/ (22) /Y/ (23) /N/ (24) /N/ (25) /W/1/2/0/ (26) i CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (27)

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/ This event was caused by a defective " Low Pressurizer Pressure SI" Reset and

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/ diock switch. When the switch was released from the " Block" position, it spring /

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/ returned past the center to the " Reset" position reinstating the Low Pressurizer /

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/ Pressure SI function. The detective switch will be replaced when unit conditions /

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/ permit.

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FACILITY METHOD OF DISCOERY DESCRI m 0N (32)

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% POWER OTHER STATUS LA/ (31)

/ Operator Observation /

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N/A ACTIVITY CONTENT RELEASED OF RELEASE AMOUNT OF ACTIVITY (35)

LOCATION OF RELEASE (36)

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PERSONNEL EXPOSURES NUMBER TYPE DESCRIPTION (39)

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LOSS OF OR DAMAGE TO FACILITY (43)

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PUBLICITY ISSUED DESCRIPTION (45)

NRC USE ONLY

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8109110240 ggo902 SR W. R. MRTWRIGHT PHONE (703) 894-5151 PDR ADOCK 05000339 S

PDR

0.

Virginia Electric and Pcwer Company North Anna Power Station, Unit 2 Attachment: Page 1 of 2-Docket No. 50-339 Report No. LER 81-062/03L-0

Description of Event

On August 10, 1981, at 1851 while in Mode 3, the ECCS Train B actuated when the Low Pressurizer Pressure SI Block / Reset switch spring returned past the center (neutral) position to the " Reset" position.

This caused an inadvertent reinstating of the "Lo Pzr Press" SI function.

'Since system pressure at that time was below the activation setpoint of 1765 psig, (cctual pressure was 1494 psig), the ECCS actuated.

The actions of 2-EP-5 were completed and the signal was reset at 1854 when it was determined to be an inadvertent actuation.

As a result of the Safety Injection, the contents of the Boron Injection Tank (BIT) were flushed to the Reactor Coolant System which caused the boron concentration in the BIT to fall below the minimum Technical Specification limit of 20,000 ppm of borated wa.er.

The BIT did perform it's intended function.

2 All of the Train B SI equipment operated as required. This was the third actuation of ECCS reportable as per T.S. 6.9.2.

The usage factor for the affected SI injection nozzles has not exceeded 0.70.

The ECCS actuation is reportable as per T.S. 3.5.2 which requires a Special Report in accordance with T.S. 6.9.2 within 90 days. This Licensee Event Report is intended to satisfy the T.S. 6.9.2 requirements.

Probable Consequences of Occurrence The purpose of the Emergency Core Cooling System is to ensure adequate cooling of the reactor in the event of a loss of coolant accident.

Although the safety injection system performed its intended function to inject borated water into the Reactor Coolant System, an actual accident condition did not exist and therefore the SI was not required. As a result, the health and safety of the general public were not affected.

Cause of Event

The "Lo Pzr Preas" Block switch has three positions; Block, Reset and Center. Both the Block and Reset positions spring return 'to the center position.

When the switch was moved to the " Block" position and released, it returned past the center to the " Reset" position on the Train B switch which unblocked the Train B Low Pressure SI function.

Since system pressure was below the Lo Pzr Pressure SI setpoint of 1765 psig the ECCS inadvertently actuated.

a.

Immediate Corrective Action

The unit was stabilized and the equipment returned to normal.

Using an approved procedure, the defect in the switch was demonstrated several times confirming the cause of the event. This was done without actually injecting water into the RCS. All Control Room Operators were made aware of the defect in the switch.

Scheduled Corrective Action When a replacement switch can be obtained and when unit conditiors allow, the switches will be replaced.

Actions Taken to Prevent Reccurrence All control room operators have been made aware of the deiect in the switch and have been instructed not to release the switch from the unblocked position but to return it to center prior to releasing the switch.

No further actions are necessary at this time. The SI blocked status lights provida positive indication of when the SI function is blocked or when it is reset.

Generic Implications There are no generic implications associated with this event.

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