Headquarters Daily Report
MARCH 05, 2001
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REPORT NEGATIVE NO INPUT
ATTACHED INPUT RECEIVED RECEIVED
HEADQUARTERS X
REGION I X
REGION II X
REGION III X
REGION IV X
PRIORITY ATTENTION REQUIRED MORNING REPORT - REGION IV MARCH 5, 2001
Licensee/Facility: Notification:
Nebraska Public Power District MR Number: 4-01-0001
Cooper 1 Date: 03/05/01
Brownville,Nebraska Resident Inspectors
Dockets: 50-298
BWR/GE-4
Subject: LEVEL CONTROL PROBLEMS FOLLOWING REACTOR SCRAM (Event 37805)
Discussion:
On March 3, 2001, at 9:42 a.m., licensed operators manually scrammed the
Cooper reactor from 18 percent power as part of a planned shutdown for a
midcycle outage. Following the reactor scram, vessel water level
initially dropped, as expected, then increased until a reactor high level
signal tripped the operating reactor feedwater pump at approximately
9:45 a.m.
In response to the high level condition, operators initiated a vessel
drain through the reactor water cleanup system. At 9:53 a.m., a reactor
equipment cooling system surge tank high level alarm was received. At
9:54 a.m., the reactor water cleanup system isolated on high temperature
caused by the high flowrate through the system heat exchangers and the
reduced return flow through the regenerative heat exchanger. At
9:58 a.m., operators observed reactor equipment cooling system high
pressure and surge tank low level alarms. Plant operators found water on
the floor surrounding the system surge tank, and no water level was
indicated in the tank.
Operators could not restart either feedwater pump following the high
level trip. At 10:26 a.m., 45 minutes after the loss of feedwater,
operators started the reactor core isolation cooling (RCIC) system to
restore reactor water level. Immediately after initiating injection, the
shrink from the cold water caused a reactor low water level scram signal,
and resulted in Groups 2, 3, and 6 containment isolations. The reactor
water cleanup system and secondary containment automatically isolated.
Reactor water level was recovered using the RCIC system. Operators
reduced the RCIC system flow once reactor vessel level increased to clear
the low level alarm point.
With reduced flow from the RCIC system, reactor vessel water level again
decreased rapidly. Licensed operators inserted a manual scram of the
reactor at 10:40 a.m. in lieu of an automatic scram on low reactor vessel
level. Level was restored and RCIC cooling was secured at 10:46 a.m.
During recovery of secondary containment, following the group isolation,
licensed operators could not maintain the required differential pressure
and declared secondary containment inoperable. Approximately 10 minutes
later, secondary containment was restored.
The senior resident inspector was in the main control room for most of
the event, and regional management established a 24-hour control room
watch by the resident inspectors until the plant was in cold shutdown.
The reactor is currently in Mode 5 being cooled with the residual heat
removal system.
REGION IV MORNING REPORT PAGE 2 MARCH 5, 2001
MR Number: 4-01-0001 (cont.)
Regional Action:
Resident inspectors will follow up and further evaluation of the risk
consequences of this event is ongoing.
Contact: David Loveless (817)860-8161
C. Marschall (817)860-8185
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