PNO-II-86-023, on 860326,reactor Tripped from 100% Power Due to ESF Activation Which Occurred on High Steam Line Flow Coincident W/Low Steam Line Pressure.Caused by Closure of Loop B Main Steam Trip Valve.Investigation Underway

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PNO-II-86-023:on 860326,reactor Tripped from 100% Power Due to ESF Activation Which Occurred on High Steam Line Flow Coincident W/Low Steam Line Pressure.Caused by Closure of Loop B Main Steam Trip Valve.Investigation Underway
ML20210G610
Person / Time
Site: North Anna Dominion icon.png
Issue date: 03/26/1986
From: Brownlee V, Ignatonis A
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:
References
PNO-II-86-023, PNO-II-86-23, NUDOCS 8604020556
Download: ML20210G610 (2)


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$ March 26, 1986 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PN0-II-86-23 This preliminary notification constitutes EARLY notice of events of POSSIBl.E safety or public interest significance _ The information is as initially received without verifi-cation or evaluation, and is basically all that is known by the Region II staff on this date.

FACI'ITY:

L Virginia Electric & Power Company Licensee Emergency Classification: ,.

North Anna Unit 1 X Notification of Unusual Event Docket No. 50-338 Alert Mineral, Virginia Site Area Emergency General Emergency Not Applicable

SUBJECT:

ESF ACTUATION FROM 100 PERCENT POWER The licensee declared an Unusual Event this morning after the reactor tripped from 100 percent power due to an Engineered Safety Features (ESF) activation which occurred on high steam line flow coincident with low steam line pressure.

The licensee reported that the ESF actuation was caused by an inadvertent closure of the "B" loop main steam trip valve. A safety injection was initiated and was terminated eight minutes into the event. Approximately 900 gallons of borated water was injected into the reactor coolant system. All . systems functioned as designed with the exception of the recording'of higher than expected readings between intennediate range channels N35 and N36, and failure of source range channel N31 to energize.

The licensee is investigating the cause of the main steam trip valve closure and the reactor protection system instrumentation problems.

Unit 1 is in hot standby, and Unit 2 is shutdown for refueling.

The resident inspectors will conduct a routine follow-up in conjunction with Region II.

The Comonwealths of Virginia has been informed.

The NRC received initial notification of this event by telephone from the licensee to the headquarters duty officer at 8:15 a.m. (EST) today.

This information is current as of 3:00 p.m. (EST) today.

Contact:

A. Ignatonis, 242-5563 V. Brownlee, 242-5583 8604020556 e60326

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