6 juin 2012
La fuite de liquide de refroidissement radioactif à l’intérieur de l’enceinte de confinement du réacteur n° 1 est estimée à environ à 1/10e de gallon par minute (0,38 litre par minute). Le réacteur était en « hot standby ».
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Degrated condition due to discovery of pressure boundary leakage
Engineers at the Davis-Besse nuclear reactor near Toledo found a pinhole coolant leak in a pipe weld Wednesday evening while doing a walk-down inspection of the plant.
Engineers were preparing to resume operations after more than a month-long reactor shutdown for refueling and maintenance. They were conducting the inspection while the reactor was in "hot standby" mode. The coolant system was running at normal operating temperatures and pressures.
In a report early Thursday to the Nuclear Regulatory Commission, plant owner FirstEnergy Corp. estimated the leak of radioactive coolant inside the reactor containment building at the about one-tenth gallon per minute.
The report noted that the coolant was spraying from a pinhole in the socket weld of a three-quarter inch pipe at a 90 degree elbow between the reactor coolant pump and a safety valve.
Reactor operators immediately began shutting down the reactor as engineers began repair preparations.
Spokeswoman Jennifer Young today said the leaked coolant was cleaned up and no radioactivity escaped into the atmosphere. There were no injuries.
FirstEnergy shut down the 908-megawatt reactor on May 6 for normal refueling, inspections and maintenance. More than 1,000 contractors worked with Davis-Besse employees to replace 68 of the reactor’s 177 fuel rods.
Contractors also were involved with preventive maintenance of major components including pumps, valves and the emergency diesel generators. Others also worked on the power plant’s cooling tower to improve efficiency.
https://www.cleveland.com/business/index.ssf/2012/06/davis-besse_1.html
Facility : DAVIS BESSE
Unit : [1]
HQ OPS Officer : DONG HWA PARK
Event Date : 06/06/2012
Event Time : 19:56 [EDT]
Emergency Class : NON EMERGENCY
Event Text DEGRADED CONDITION DUE TO DISCOVERY OF PRESSURE BOUNDARY LEAKAGE
"On June 6, 2012, at 1956 EDT, with the Unit shutdown for refueling, leakage was identified from a 3/4-inch weld during Reactor Coolant System (RCS) walkdown inspections. The leakage amount was approximately 0.1 gpm pinhole spray.
"During the performance of MODE 3 engineering walkdown inspections in accordance with procedure DB-PF-03010 (ASME Section III, Class 1 and 2), with the RCS at Normal Operating Temperature and Pressure, a pressure boundary leak was identified on the Reactor Coolant Pump (RCP) 1-2 1st seal cavity vent line upstream weld of 3/4 inch small bore pipe socketweld at a 90 degree elbow between the RCP pump and valve RC-407 (1st Seal Cavity Vent Isolation). The plant was in MODE 3 at Normal Operating Pressure and Normal Operating Temperature (NOP/NOT) for the inspections.
"The plant entered Technical Specification (TS) Limiting Condition for Operation (LCO) 3.4.13, ’RCS Operational Leakage,’ Condition B and procedure DB-OP-02522. ’Small RCS Leaks,’ abnormal operating procedure. Plant cooldown to comply with LCO 3.4.13, Condition B, Required Action B.2 is in progress. The cause and resolution are under evaluation.
"This event is reportable within 8 hours under 10CFR50.72(b)(3)(ii)(A).
"The NRC Resident Inspector has been notified. This condition has been documented in the Davis-Besse Corrective Action program as Condition Report 2012-09381."
The plant is required to be in MODE 5 within 36 hours.
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2012/20120607en.html
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