Power has been restored to two fuel storage pools at Japan's tsunami-damaged nuclear plant, but two others have been without fresh cooling water for more than a day, raising concerns about the fragility of a facility that still runs on makeshift equipment.
Tokyo Electric Power Co. 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.
The cooling system was restored at two of the four pools by Tuesday evening, and the systems for the two other pools were to resume by Wednesday morning as workers complete repairs and try to determine the cause of the problem, TEPCO spokesman Masayuki Ono told reporters.
"We now have better prospects for cooling to resume," he said.
About 50 workers in hazmat suits and full-face masks were mobilized to fix cabling that involved the last of the three switchboards that they suspect as a possible cause of the problem. The utility was also preparing a backup system in case the repairs didn't fix the issue and "the worse comes to worst," Ono said.
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. Massive radiation leaks from the plant have contaminated air, water and soil around the plant, causing some 160,000 residents to evacuate.
The current power outage is a test for TEPCO to show if it has learned anything from the disaster. TEPCO, which has repeatedly faced cover-up scandals, was slammed by local media Tuesday for waiting hours to disclose the blackout.
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."
Ono 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 but prioritized power restoration after all.
There is a backup cooling system but no backup outside power. TEPCO has backup cooling systems with separate power sources for reactor cooling, but fuel storage pools only have emergency diesel generators as a backup. TEPCO said it will consider installing backup outside power for the pools.
Units 3 and 4 reactors shared a makeshift switchboard that sits on the back of a truck but an upgrade for permanent, safer location was being planned later this month. Reactor cooling water pumps also sit on the back of a truck, with hoses traveling several kilometers (miles) to reach the reactors.
"We have a ton of problems that still needs to be taken care of to overcome the challenges that we have never experienced," Ono said. But he denied the power outage would affect the plant's long-term cleanup plans.
Regulators have raised concerns about the makeshift equipment and urged the plant to switch them to a more permanent arrangement. The operator still has to remove melted, fatally radioactive fuel from the reactors before fully decommissioning the plant, which officials say could take 40 years.
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," Suga told reporters in a regular briefing.
The command center at the plant suffered a brief power outage before 7 p.m. Monday. Electricity was quickly restored to the command center 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 degrees Celsius, TEPCO said.
"We don't believe the Fukushima disaster is under control," said Yuko Endo, chief of Kawauchi village, part of which remains restricted due to radiation contamination, keeping hundreds of residents away from home. Officials are struggling to make the area livable again, but people cannot return home unless they feel confident about the plant's stability, he said.