PNO-III-87-128, on 871002,facility Tripped from 7% Power Due to High Water Level in One of Four Steam Generators,Creating Loss of Offsite Power.Caused by Personnel Error.Licensee Inspecting Damage to Auxiliary Transformer Disconnect Links

PNO-III-87-128:on 871002,facility Tripped from 7% Power Due to High Water Level in One of Four Steam Generators,Creating Loss of Offsite Power.Caused by Personnel Error.Licensee Inspecting Damage to Auxiliary Transformer Disconnect Links

ML20235S466
Person / Time
Site:	Byron
Issue date:	10/02/1987
From:	Forney W, Hinds J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
References
PNO-III-87-128, NUDOCS 8710090009
Download: ML20235S466 (2)

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PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-III-87-128 Date October 2 0 1987 i

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 III staff on this date.

Facility: Commonwealth Edison Company Licensee Emergency Classification:

Byron Unit 2 X Notification of an Unusual Event Byron, IL 61010 Alert Site Area Emergency Docket No. 50-454 General Emergency Not Applicable ,-

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Subject:

LOSS OF 0FF-SITE POWER CAUSED BY PERSONNEL ERROR At 4:46 a.m. on October 2,1987, Byron Unit 2 tripped from 7 percent power because of high water level in one of four steam generators. The high water level was caused by a problem with a feedwater regulating bypass valve. All systems functioned normally during the trip.

(The plant was starting up after a reactor trip on October 1,1987.)

Following the trip, the station's procedures call for the main generator to be disconnected from the distribution system via the disconnect links in addition to the automatic opening of the switch yard breakers. A station operator and a foreman, dispatched to open the disconnect links, mistakenly opened the links for the auxiliary transformer which was providing off-site power to the unit.

When the links were opened, off-site power was lost at 5:01 a.m. and the unit's two emergency diesel generators started to provide power to essential safety systems. (Off-site power could not be restored immediately, because of possible damage ca sed by arcing when the disconnect links were opened on the energized line.)

l Unit I was operating at 97 percent and remains in operation. The loss of Unit 2 off-site l power caused the loss of the Unit 1 process computer because a backup battery inverter was out of service. The process computer was restored to service at 7:40 a.m.

The licensee declared an Unusual Event under its emergency plan. Appropriate governmental agencies were notified.

The resident inspector was notified of the event by the licensee and was at the plant site .

about 7:10 a.m. A team of a section chief and two inspectors was dispatched to the site l from Region III (Chicago).

DISTRIBUTION:

H. St. EDO NRR E/W Willste Mail: ADM:DMB ,

Chairman Zech PA IE NMSS DOT:Trans only l Comm. Roberts ELD OIA RES l Comm. Bernthal AE0D NRC Ops Ctr \b44 I Comm. Carr '

l Comm. Rogers ACRS SP\\ % t Regional Offices SECY CA INP0 M S NSAC \\ AC1 PDR RIII Resident Office l Licensee: W 4.:L (Corp. Office - Reactor Lic. Only)  :

8710090009 871002 hk

$-I!he7-128PDR Region III ] f: y

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PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-III-87-128 Date October 2, 1987 ,

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Plant conditions remain stable with the reactor being cooled down using natural circulation through the steam generators. Both auxiliary feedwater pumps are in operation. The licensee expects the plant to be in cold shutdown in about 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. If no damage occurred to the disconnect links, off-site power could be restored about 12 noon. Power to essential systems continues to be provided by the two Unit 2 emergency diesel generators. The Unit 1 diesel generators are also available through a cross tie.

The licensee is inspecting the auxiliary transformer disconnect links to determine the extent of damage.

The State of Illinois has been informed.

Region III was notified of this event at 6:25 a.m. by the resident inspector. This information is current as of 9:30 a.m., October 2, 1987.

CONTACT: . 2 n (FTS 388-5575) (FTS 388-5590) l

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