PNO-III-90-026, on 900410,reactor Scrammed When Inboard MSIVs Began to Drift Shut Because of Loss of Pressure in Containment Pneumatic Nitrogen Sys

PNO-III-90-026:on 900410,reactor Scrammed When Inboard MSIVs Began to Drift Shut Because of Loss of Pressure in Containment Pneumatic Nitrogen Sys

ML20212A231
Person / Time
Site:	Fermi
Issue date:	04/10/1990
From:	Beverly Clayton, Defayette R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
References
PNO-III-90-026, PNO-III-90-26, NUDOCS 9710230215
Download: ML20212A231 (2)

APR 10 '90 13: 35 NRC REGION 3B P01 j/)u . ., rg PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-!!!-90-26 Date April 10, 1990 it ir eliminary notification constitutes EARLY notice of events of POSSIBLE safety or public

,t significance. The information is as initially received without verification or eva tion, and is basically all that is known by the Region 111 staff on this date.

Facility: Detroit Edison Company Licensee Emergency Fermi 2 Classification:

Newport, MI 48166 Unusual Event Alert Docket No. 50-341 Site Area Emergency General Emer ency X Not App 11 cab c Iy' / p 1 gj g)e

Subject:

REACTOR SCRAM CAUSED BY MSIV CLOSURE The rcactor scrammed at 2:02 a.m. (EDT) on April 10, 1990, when the inboard main steam isolation valves (MSIVs) began to drift shut because of a loss of pressure in the c:ntainment pneumatic nitrogen system. Nitrogen pressure maintains the inboard MSIVs in their open position, and they close if pressure is lost.

The licensee believes the loss of nitrogen pressure was caused by a leak in the pneumatic system. Contributing to the pressure loss was the trip of a reactor protection system motor generator set. This trip isolated the drywell pneumatic nitrogen system, preventing the addition of nitrogen to maintain pressure in the system.

Subsequent to the scram, the licensee identified a significant leak in a feedwater heater.

The cause of the leak was identified as a broken line to a relief valve on the feedwater sifmf the heater, and the nature of the break is still under investigation. Access is ri )ted to portions of the turbine building as a result of feedwater on the floor.

Cidp is in progress and access is expected to be restored later today.

The plant is being cooled down for an outage of approximately three days to com)1ete the repairs, conduct surveillance testing, and perform maintenance which could not de done while the plant was at power.

The resident inspectorr are monitoring the licensee's inspection and repair activities.

Th2 licensee expects the plant to remain shut down about three days.

The State of Michigan will be notified. The information in this preliminary notification has b:en reviewed by licensee management.

The Headquarters Operation Center was notified of this event at 4:45 a.m. (EDT), April 10, 1990. This information is current as of 10:00 a.m., April 10, 1990.

q CONTACT: . DeFayette B. Clayton FIS 388-5767 N FTS 388-5574 , l n v' 2  :

~

p h . _. El; Q =

\v 9710230215 900410 PDR I&E PNO-III-90-026 PDR

, APR 10*'90,G,136 NRC REGIDH 3B P02

[RELIMINARY_ NOTIFICATION OF CVENT OR UNUSUAL GCCURRENCE PNO-Ill-90-26 Date April 10, 1990 DISTRIBUTION:

KADQUARTERSOFFICES __

REGIONS Mall TO Chifrman C'arr es Region I Dc5 Conn. Roberts GPAtSLITP Region 11 00T(Orig)

(Trans.

Cose. Rogers GPA:PA Regior IV Only)

CowJ. Curtiss GPA:CA Region V Cohan. Realck *0!G EDO *ASLAP __

FAX T01 <

I Gen. Counsel Research INPO N5AC LIG NRR 1RM NRC O W TTR AE00 ACRb POR (8/634-3343]

Enforcement

' Denotes a Displaywriter/PC not an IBM 5520 Terminal.

Rev. 12/05/89 O

=e.

O