21 janvier 2014
La situation a été classée critique suite à l’arrêt automatique simultané des deux réacteurs de la centrale après la perte des alimentations électriques de 13 000 puis 4 000 volts.
Type : PWR - Puissance : n° 1 et 2, 2 700 MWTh - Première divergence : n°1 10/1974 - n° 2 11/1976
Available in english only.
L’alimentation en eau du réacteur n° 2 a été perdue pour une raison indéterminée (en cours de recherche). L’évacuation de la chaleur du réacteur n° 2 a été indisponible suite à la perte des pompes à eau, perte elle-même liée à une perte de vide du condenseur. Les groupes diesels de secours ont pris le relais de l’alimentation électrique. Le 27 janvier, la NRC a envoyé une équipe d’inspecteurs pour analyser cet évènement.
Event Number : 49754
Facility : CALVERT CLIFFS - State : MD - Unit : [1] [2] - RX Type : [1] CE,[2] CE
Event Date : 01/21/2014- Event Time : 21:25 -
Emergency Class : NON EMERGENCY - 10 CFR Section : 50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL 50.72(b)(3)(iv)(A) - VALID SPECIF SYS ACTUATION
Reactor n° 1 A/R Y 100 Power Operation 0 Hot Standby Reactor n° 2 A/R Y 100 Power Operation 0 Hot Standby
Event Text
DUAL UNIT TRIP ON THE LOSS OF THE "21" 13KV BUS
"Dual Unit Trip due to loss of ’21’ 13 KV bus . All safety functions are met for both units. Unit 1 remained with normal heat removal. Unit 2 lost power to its normal heat sink and is stable on Auxiliary Feed water and Atmospheric Dump Valves for temperature control. Both trips were automatic trips. Due to loss of power a Under Voltage actuation occurred on both units (’14’ and ’24’ 4Kv bus). Due to loss of main feed on Unit 2 a Auxiliary Feed water Actuation System [AFW] actuation occurred on Unit 2. Cause is under investigation."
All control rods fully inserted on the loss of power to the Control Rod Drive Mechanisms [CRDMs]. Both Units Reactor Coolant Pumps [RCPs] remained running during the transient. The normal Unit 2 heat sink was unavailable due to the loss of the operating circulating water pumps resulting in a loss of condenser vacuum. The Unit 2 AFW actuation included one of two steam-driven pumps and the motor-driven pump. Both Units Emergency Diesel Generators started and loaded and have since been secured. Both Units are stable and will remain in mode 3 (Hot Standby) pending the results of the investigation.
The licensee will inform the NRC Resident Inspector.
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2014/20140122en.html
Mon Jan 27, 2014 3:07pm EST
Jan 27 (Reuters) - The U.S. Nuclear Regulatory Commission on Monday sent a special inspection team to Constellation Energy Nuclear Group LLC’s Calvert Cliffs nuclear power plant in Maryland to inspect an unplanned shutdown of both the reactors that occurred last week.
"We want to gain a better understanding of the chain of events that caused both of the reactors to simultaneously shut down and equipment anomalies subsequent to the plant trips," NRC’s region I administrator Bill Dean said in a statement.
"This inspection is designed to shed additional light on not only why the outages happened, but how the plant operators handled them," he added.
Both its 855-megawatt Unit 1 and 850-megawatt Unit 2 were shut on Jan. 21 due to an electrical malfunction on the non-nuclear side of the plant.
Unit 1 was operating at 97 percent power and Unit 2 was at full power by early Monday, the company said.
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