PNO-I-88-010, on 880120,reactor Scrammed from 42% Power Based on Low Reactor Vessel Water Level.Caused by Equipment Operator Error.Nrc Dispatched Augmented Insp Team to Site to Review Generic Safety Implications of Event

PNO-I-88-010:on 880120,reactor Scrammed from 42% Power Based on Low Reactor Vessel Water Level.Caused by Equipment Operator Error.Nrc Dispatched Augmented Insp Team to Site to Review Generic Safety Implications of Event

ML20148G961
Person / Time
Site:	Nine Mile Point
Issue date:	01/21/1988
From:	Cook W, Jerrica Johnson NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
References
PNO-I-88-010, PNO-I-88-10, NUDOCS 8801270073
Download: ML20148G961 (2)

DCS No: 50410880120 Date: January. 21, 1988 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-I-88-10 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as initially received without verification or evaluation, and is basically all that is known by the Region I staff on this date.

Facility: Niagara Mohawk Power Corporation Licensee Emergency Classification:

Nine Mile Point Unit 2 X Notification of Unusual Event Scriba, New York Alert.

Docket No. 50-410 Site Area Emergency General Emergency Not Applicable

Subject:

REACTOR SCRAM AND VESSEL OVERFILL; AIT DISPATCHE0 At 9:45 a.m. on January 20, 1988, the reactor at Nine Mile Point Unit 2 scrammed from 42% power based on a low reactor vessel water level. The event was initiated when an equipment operator incorrectly isolated an instrument air filter, resulting in rapidly -

decreasing pressure in the instrument air system. This resulted in the feedwater minimum flow recirculation valve going full open (returning feedwater to the main condenser) and reducing the feedwater flow to the reactor.

Following the reactor scram, the high pressure core spray (HPCS) and reactor core isolation cooling (RCIC) systems injected water into the reactor vessel to return the water level to normal. Subsequently, the HPCS and RCIC systems were secured as intended when water level exceeded the normal range, but the condensate booster pumps continued to inject water. This eventually resulted in the water level reaching the main steam lines and water flowing into these lines. The operators then terminated the feedwater injection by closing the feedwater control valves and blocking valves.

During the event an unusual Event was declared due to entry into the Emergency Operating Procedures for control of reactor vessel water level. The Unusual Event was terminated within one hour when control of water level was restored.

On January 21 the NRC dispatched an Augmented Inspection Team to the site to review the generic safety implications of the overfilling of the reactor vessel and the interaction of nonsafety-related equipment in the feedwater system on the reactor.

The inspection is expected to last five days. Nine Mile Point Unit 2 entered into a planned seven day outage one day early. Niagara Mohawk has agreed to remain shutdown until authorized to start-up by the Regional Administrator of NRC Region I.

This PN is issued for information only. The State of New York has been notified.

CONTACT: William Cook Jon Johnson 8-315-342-4041 346-5234 d

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CA PDR- . Regional Offices TM1 Resident Section RI Resident Office Licensee:

(Reactor Licensees)

Region I' Form 83 (Rev. August 1987) t t

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