TOKYO (AP) - Four fuel storage pools at Japan's tsunami-damaged nuclear plant have been without fresh cooling water for nearly 20 hours due to a power outage, the plant's operator said on Tuesday, raising concerns about the fragility of a facility that still runs on makeshift equipment.
Tokyo Electric Power Co. (TEPCO) said that pool temperatures at the Fukushima Dai-ichi plant were well within safe levels, and that pools would remain safe for at least four days without fresh cooling water. The utility said the reactors were unaffected and no other abnormalities were found.
TEPCO workers were scrambling to find the cause and repair the problems.
Workers were fixing the last of the three switchboards that they suspect as a possible cause of the problem and the utility was preparing a backup system in case the repairs did not fix the issue, TEPCO spokesman Masayuki Ono told reporters.
"If worse comes to worst, we have a backup water injection system," said Mr Ono.
Japan's March 11, 2011, earthquake and tsunami destroyed the plant's power and cooling systems, causing three reactor cores to melt and fuel storage pools to overheat.
The current power outage is a major test for TEPCO to show if it has learned anything from the disaster. TEPCO, which has repeatedly faced cover-up scandals, was already slammed by local media on Tuesday for waiting hours to disclose the blackout.
Mr Ono acknowledged the plant was vulnerable.
"Fukushima Dai-ichi still runs on makeshift equipment, and we are trying to switch to something more permanent and dependable, which is more desirable," he said. "Considering the equipment situation, we may be pushing a little too hard."
He said the utility did not immediately try to switch to a backup cooling system because doing so without finding and fixing the cause could lead to a repeat of the problem. There is a backup cooling system but no backup outside power.
Regulators previously have raised concerns about the makeshift equipment and urged the plant to switch them to more permanent arrangement. The operator still has to remove melted, fatally radioactive fuel from reactors before fully decommissioning the plant, which officials say could take 40 years.
Mr Yoshihide Suga, the chief government spokesman, sought to allay concerns.
"In a sense, we have put in place measures that leave no room for worry," he told reporters in a regular press briefing.
The command centre at the plant suffered a brief power outage before 7 pm local time on Monday. Electricity was quickly restored to the command centre but not to equipment pumping water into the fuel pools.
The temperature in the four pools had risen slightly, but was well below the utility's target control temperature of 65 deg Cel, TEPCO said.