Clinton Nuclear Station Loss of RHR Cooling due to incorrect water level indiciation

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Power Reactor Event Number: 47533
Facility: CLINTON
Region: 3 State: IL
Unit: [1] [ ] [ ]
RX Type: [1] GE-6
Notification Date: 12/18/2011
Notification Time: 18:08 [ET]
Event Date: 12/18/2011
Event Time: 09:30 [CST]
Last Update Date: 12/18/2011
Emergency Class: NON EMERGENCY
10 CFR Section:
50.72(b)(3)(v)(B) – POT RHR INOP
Person (Organization):
Unit SCRAM Code RX CRIT Initial PWR Initial RX Mode Current PWR Current RX Mode
1 A N 0 Cold Shutdown 0 Cold Shutdown
LOSS OF RHR COOLING DUE TO INCORRECT REACTOR WATER LEVELINDICATION”On 12/18/11 at approximately 0930 CST, with the plant in Mode 4, while Operations was lowering reactor water level as part of restoration activities following the Reactor Pressure Vesselhydrostatic test, an automatic reactor scram and Residual Heat Removal (RHR) ‘A’ pump trip occurred due to a valid Reactor Water Level Low (Level 3) signal. The cause of the low level appears to be due a significant disparity between the Upset and Shutdown Range level instrumentation and the Level 3 RPS [Reactor Protection System] instrumentation. No rod motion occurred during the reactor scram as all control rods were fully inserted at the time of the event. Operations immediately entered the station off-normal procedures for Loss of Shutdown Cooling and Reactor Scram. The ‘A’ RHR pump was restored at 0956 CST. Reactor coolant temperature increased from approximately 128.7 deg F to 131.7 deg F during the event. At 1112 CST, the scram was reset and at 1216 CST, the off-normal procedures were exited.”Following the event as part of trouble shooting, maintenance personnel performed a fill and vent of reactor water level transmitter, 1B21N027. At the completion of this fill and vent, indicated water level changed from 195″ to 86″ on Shutdown Range and from off-scale high (>180″) to 103″on Upset Range. No change in other reactor water level indication was observed.

“This event is reportable under 10 CFR 50.72 (b)(3)(v)(B), as an event or condition that could have prevented the fulfillment of a safety function needed to remove residual heat, and 10 CFR 50.72 (b)(3)(iv)(A), event or condition that results in a valid actuation of the reactor protection system (RPS).”

The licensee has notified the NRC Resident Inspector.

Source: NRC Event Notifications

The Clinton Power Station is located near Clinton, Illinois, USA. The nuclear power station has a General Electric boiling water reactor on a 14,300 acres (57.9 km2) site with an adjacent 5,000 acres (20.2 km2) cooling reservoir, Clinton Lake.

Due to inflation and cost overruns, Clinton’s final construction cost exceeded $2.6 billion. The power station began service on April 24, 1987 and is currently capable of generating 1,043 MW.

After more than a decade of operation the plant’s original owner, Illinois Power, deduced that it was not economical to own and operate only one nuclear generating station. They subsequently sold Clinton Generating Station to Exelon Corporation for a more modest price of $40 million dollars, with the purchase including the fuel in the reactor vessel and responsibility of all the radioactive waste in the spent fuel storage pool. The reactor design is of the type called the Generation II reactor.

Clinton Nuclear Station is a BWR-6 with a Mark III containment structure. The present reactor operating license was issued April 17, 1987, and will expire September 29, 2026.

The Operator and Owner is the Exelon Corporation.

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