UPDATED: At the time of writing, the cooling system for the shared fuel pool remained out of action. However, operation of this system resumed at 0.12am on 20 March.
An electrical failure led to the loss of cooling systems at the fuel pools of Fukushima Daiichi units 1, 3 and 4, as well as the shared pool. The systems at the three units are now back in operation, while that of the shared pool is under repair.
Tokyo Electric Power Company (Tepco) said that power supply facilities in the main anti-earthquake building at the plant "momentarily stopped" just before 7.00pm yesterday. This led to the failure of three switchboards which in turn caused the malfunction of the cooling systems for the used fuel pools of units 1, 3 and 4, as well as the shared fuel pool.
The power failure did not interrupt the operation of the cooling system for unit 2's used fuel pool or the water injection systems employed to cool the damaged reactor cores of units 1-3.
Operation of unit 1's used fuel pool cooling system was resumed at 2.20pm today. The cooling system of unit 4's pool was restarted at 4.13pm through the use of a diesel generator. Unit 3's cooling system was put back into operation at 10.43pm.
The cooling system of the common fuel pool is expected to be restarted at 8.00am tomorrow.
Tepco has now resumed operation of the cooling systems for the pools of units 1, 3 and 4. It expects to have the system for the share pool back in operation tomorrow.
The temperatures in the used fuel pools prior to the power loss ranged from 13.7ºC to 25.2ºC, Tepco noted. It estimated that it would have taken over four days for the temperature of unit 4's fuel pool to exceed 65ºC, while unit 1's would have taken some 27 days to reach this temperature.
Tepco spokesman Masayuki Ono was quoted by Associated Press as saying, "We are attacking this with all necessary speed." However, he added, "If the worst comes to worst, we have a backup water injection system."
Ono noted, "Fukushima Daiichi still runs on makeshift equipment, and we are trying to switch to something more permanent and dependable, which is more desirable. Considering the equipment situation, we may be pushing a little too hard."
Tepco said that it is presumed that some protection circuits responded to the brief power outage by shutting down the switchboards. It added that further investigations were needed to determine the exact cause of the power failure in order to prevent it happening again.
Researched and written
by World Nuclear News