14 juillet 2015
C’est suite à la perte des circuits de refroidissement des baies électriques des voies A et B des alimentations de 4 kV que cet arrêt des trois réacteurs de la centrale est imposé. Les actions d’arrêt doivent être lancées dans l’heure pour amener les réacteurs dans le mode 2 dans les 10 h puis en mode 3 dans les 13 heures et enfin en mode 4 dans les 37 heures.
Type : Fukushima 1 (BWR Mark 1) - Puissance : 3 458 MWth - Première divergence : n° 1 : 08/1973 ; n° 2 : 7 / 1974 ; n° 3 : 08/1976
Available in english only.
Event Number : 51231
Facility : BROWNS FERRY - State : AL
Unit : [1] [2] [3] - RX Type : [1] GE-4,[2] GE-4,[3] GE-4
Event Date : 07/14/2015 - Event Time : 17:15
Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(2)(i) - PLANT S/D REQD BY TS
Initial PWR Current PWR
1 N Y 100 % Power Operation 99 % Power Operation
2 N Y 100 % Power Operation 99 % Power Operation
3 N Y 100 % Power Operation 99 % Power Operation
Event Text
TECHNICAL SPECIFICATION REQUIRED SHUTDOWN
"At 1810 (Central Daylight Time) on July 14, 2015, Browns Ferry Units 1, 2, and 3 initiated actions to commence a reactor shutdown to comply with TS [Technical Specifications] LCO 3.0.3. TS LCO 3.0.3 was entered at 1715 (Central Daylight Time) due to concurrent losses of the A and B Control Bay Chillers. This resulted in a loss of cooling to the U1 and U2 4kV Shutdown Board Rooms. Required actions for the loss of cooling to the U1 and U2 4kV Shutdown Board Rooms are to declare the electrical equipment in the 4kV Shutdown Board Rooms inoperable. The declaration of inoperability of the equipment supported by the U1 and U2 4kV Shutdown Boards resulted in TS LCO 3.0.3 for Units 1, 2, and 3. TS LCO 3.0.3 requires actions to be initiated within one hour to place the affected units in MODE 2 within 10 hours ; MODE 3 within 13 hours ; and MODE 4 within 37 hours.
"This event requires a 4-hour report in accordance with 50.72(b)(2)(i), ’The initiation of any nuclear plant shutdown required by the plant’s Technical Specifications.’
"The NRC Resident Inspector has been notified.
"Condition Report #1056829 has been initiated in the Corrective Action Program."
The 4kV shutdown electrical boards are required in all modes of operation.
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2015/20150715en.html#en51231