ML17284A653
| ML17284A653 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 06/02/1998 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | |
| Shared Package | |
| ML17284A645 | List: |
| References | |
| 50-397-98-05, 50-397-98-5, NUDOCS 9806100421 | |
| Download: ML17284A653 (6) | |
See also: IR 05000397/1998005
Text
ENCLOSURE
NRC INSPECTION REPORT 50-397/98-05
ATTACHMENT2
"DETAILEDCHRONOLOGY OF MARCH 11, 1998, MAINSTEAM
LINE ISOLATIONVALVECLOSURE AND REACTOR SCRAM"
CORRECT! ON
980610042i
980602
PDR"
ADOCK 05000397
8
ATTACHMENT2
DETAILEDCHRONOLOGY OF MARCH 11, 1998
MAINSTEAM LINE ISOLATIONVALVECLOSURE AND REACTOR SCRAM
March 10
Reactor power at 100 percent
Day
March 11
The licensee noted an increase in the containment instrument air (CIA) usage
(from 1 to 1.5 SCFM) and began reviewing the potential causes for the increased
usage.
Reactor power was at 100 percent and all safety systems w'ere available and in
standby.
05:16:05
Main Steam Isolation Valve 22D fast closed on loss of containment
instrument air (CIA) nitrogen supply to the valve operator.
05:16:10
A reactor scram signal was generated
on an average power range
monitor (APRM) high flux of 118 percent.
05:16:11
Nuclear steam supply system (NSSSS) isolation and all main steam
isolation valves close on high main steam line flows.
05:16:13
Reactor pressure increases to 1085 psig and 2 safety relief valves
automatically actuate to reduce pressure.
Each safety relief valve
properly reseats.
05:16:14
The high pressure core spray diesel generator started on Level 2
(-50 inches reactor vessel level narrow range).
05:16:15
The reactor core isolation cooling and high pressure core spray systems
initiated and subsequently began injection into the reactor vessel. A main
turbine trip was initiated and the reactor closed cooling system pumps
tripped and was isolated from the drywell, resulting in a loss of drywell
cooling. A slow increase in drywell pressure begins because of the loss of
the drywell,coolers.
05:16:16
Four control rod position indications were lost, requiring operators to verify
the control rods had fullyinserted using the rod worth minimizer. All
control rods subsequently indicated full in.
05:16:38
The reactor core isolation cooling system reached maximum flow at 860
gallons per minute.
05:17:17
The reactor core isolation cooling system automatically isolated on high
reactor vessel level by closing the steam admission Valve V-45.
-2-
05:17:18
The high pressure core spray injection Valve 4 automatically closed on
high reactor vessel level.
05:19:00
The operators started residual heat removal Pump A and service water
Pump 1A in the wetwell cooling mode
.
05:26:00
The standby gas treatment system was started to reduce drywell pressure
by venting.
05:26:59
05:27:21
The reactor core isolation cooling system tripped when manually initiated.
Drywell pressure increased to approximately 1.65 psig resulting in
engineered safety feature actuation of the Division tl emergency diesel
generator.'5:28:00
The operators were able to restore the reactor closed cooling system and
established drywell cooling for pressure reduction.
05:28:29
The operator was subsequent(y able to reclose the reactor core isolation
cooling system trip and throttle valve from the control room and reinitiate
the system.
05:28:35
Drywell pressure increased to approximately 1.65 psig and resulted in the
engineered safety feature actuation of the Division I emergency diesel
generator.
05:29:08
The high drywell pressure engineered safety feature actuation signals
cleared on decreasing drywell pressure.
05:38:00
Standby gas treatment system secured.
05:54:00
High pressure core spray pump secured
05:58:00
06:00:00
The operators reset the reactor scram.
The high pressure core spray emergency diesel generator was secured.
Earlier, the emergency diesel generator restarted when the system was
shutdown prior to resetting the initiation circuitry
06:07:00
A reactor protection action signal initiated on low reactor vessel level. The
reactor core isolation-cooling system could not be operated in the
recirculation mode resulting in difficultyin controlling reactor vessel level
between plus 13 inches {lowlevel) and plus 54 inches (high level).
06:11:00
The licensee made a four hour nonemergency notification that a reactor
protection system actuation had occurred from a main generator lockout.
e
-3-
07:30:00
Pressure
and temperature indicated cooldown had exceeded the
allowable pressure and temperature curve
07:37:00
Main steam isolation valves opened (except 22D) and main turbine
bypass valves placed in auto.
07:41:00
07:44:00
07:45:00
09:00:00
09:11:00
Operators placed reactor pressure vessel level control in auto.
Reactor core isolation cooling injection secured.
Pressure
and temperature within area on the cooldown curve
Pressure
and temperature exceeds the allowable limits established by the
pressure and temperature curve
10 CFR 50.72(b)(2)(ii) 4-hour non-emergency notification of RPS
actuation (scram)
10:24:00
Reactor water cleanup system placed back in service with the
demineralizes bypassed.
10:28:00
10 CFR 50.72 (b)(2)(ii) and (iii)4-hour nonemergency notification of a
second RPS actuation and an engineered safety feature actuation
involving a reactor pressure level low level scram
10:30:00
Pressure and temperature returned to the to the right of the pressure and
temperature curve (acceptable limits) based on temperature indications
provided by the reactor water cleanup system.
11:13:00
Started reactor recirculation Pump 1A establishing forced circulation.
March 12
02:00:00
Plant entered Mode 4.
20:42:00
Event updated report to the NRC operations officer which provided
supplemental and corrected information.