PNO-I-86-096, on 861130,reactor Tripped from Full Power Due to Low Water Level & Steam/Feed Mismatch in Steam Generator 3.Caused by Technician Shorting Out Control Power.Cracked Check Valve Replaced

PNO-I-86-096:on 861130,reactor Tripped from Full Power Due to Low Water Level & Steam/Feed Mismatch in Steam Generator 3.Caused by Technician Shorting Out Control Power.Cracked Check Valve Replaced

ML20214V296
Person / Time
Site:	Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	12/01/1986
From:	Mccabe E, Swetland P NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
References
PNO-I-86-096, PNO-I-86-96, NUDOCS 8612090612
Download: ML20214V296 (2)

e . DCS No: 50213861130 Date: D:cember 1, 1986 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-I-86-96 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety

-or public interest significance. The information is as initially received without v:rification or evaluation, and is basically all that is known by the Region I staff on tnis cate.

Facility: Licensee Emergency Classification:

. Connecticut Yankee Atomic X Notification of Unusual Event

. P:wer Company Alert HaddamNeckPlant(50-213) Site Area Emergency Hiddam Neck, Connecticut General Emergency Not Applicable

Subject:

UNSCHEDULED SHUTDOWN GREATER THAN 48 HOURS Haddam Neck tripped from full power at 4:30 p.m., November 30, 1986, due to low water level and steam / feed flow mismatch in steam generator SG-3. The cause was a technician shorting out control power while correcting a loose connection in the #3 feedwater control drawer. The #3 feedwater regulating valve, which was in manual control for the taintenance, closed on loss of control power, causing low level in SG-3 and the auto-tatic trip. Plant systems responded normally. During flow restoration in loops 1 and 3 (the reactor coolant pumps in these loops trip on reactor trip and are manually restarted), a leak developed in the valve stem leak off line for the loop I cold leg isolation valve (CLIV). This normally-open, back-seated CLIV must be closed to manu-ally start the reactor coolant pump (RCP). When operators closed the loop 1 CLIV, they noted a marked increase in the RCS leak rate and increasing air-borne radiation levels in cor.tainment. After the RCP was started and the CLIV valve was reopened (back-seated), the leak rate slowed from about 20 gallons per minute (GPM) to 1-2 gpm.

Centainment air-borne radiation levels stopped rising, and decreased when the contain-ment air recirculation filters were placed in service. No release was detected outside containment.

Licensee inspection inside containment found steam coming from the body of the h in, chsck valve on the loop 1 CLIV stem leak-off line to the primary drain tank. Valve body erosion was identified by the licensee as the apparent cause. A plant cooldown was begun for replacement of the cracked check valve.

The resident inspector responded to the site. NRC Region I found the actions in progress to be acceptable. Upon further review, the licensee concluded that an Unusual Event had existed while the RCS leak rate exceeded 10 gpm, and made the required notifications. As of 8:00 a.m., December 1, 1986, the plant was cooled down to 375 degrees F and the leakage had decreased to about I gpm af ter manual back-seating of the '

loop 1 CLIV. The licensee expects the shutdown to last 1-3 days.

The licensee made a press release on December 1, 1986. The resident inspector has responded to media inquiries. The State of Connecticut has been informed.

CONTACT: Swetland McCabe 203-267-2571 FTS 488-1231 8612090612 e61201 PDR

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DISTRIBUTION:

N;. St.* MNBB Phillips E/W Willste Mail: ADM:DMB Chairman Zech EDO NRR ~IE- NMSS DOT:Trans only Comm. Bernthal PA OIA RES

-Comm. Roberts ELD AE0D Comm. Asselstine Comm. Carr ACRS Air Rights INP0J@S' SECY SP NSAC dLE'

'CA PDR Regicnal Offices TMI Resident Section d'tD RI Resident Office 2:o o Licensee:

(Reactor Licensees)

Region I Form 83

. (Rev. July 1986)

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