View source for 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

{{Adams
| number = ML20212A231
| issue date = 04/10/1990
| title = 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
| author name = Clayton B, Defayette R
| author affiliation = NRC OFFICE OF INSPECTION &amp; ENFORCEMENT (IE REGION III)
| addressee name = 
| addressee affiliation = 
| docket = 05000341
| license number = 
| contact person = 
| document report number = PNO-III-90-026, PNO-III-90-26, NUDOCS 9710230215
| document type = PRELIMINARY NOTIFICATION OF EVENT OR OCCURRENCE (PNO,, TEXT-INSPECTION &amp; AUDIT &amp; I&amp;E CIRCULARS
| page count = 2
}}
{{#Wiki_filter: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        :
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   \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
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