The radiation level at the disaster-hit Fukushima No. 1 nuclear plant, 230 km north of Tokyo, remained unchanged Thursday morning even after Japanese military helicopters dumped huge amounts of water onto its damaged No. 3 reactor in an effort to cool down a spent fuel storage pool.
The radiation level at a spot located 110 meters from the No.3 reactor stood at 3,782 microsievert per hour at 9:40 a.m. (0040 GMT) before Self-Defense Force helicopters dropped tons of water onto the hardest-hit reactor.
But the radiation level only edged down to 3,754 microsievert per hour at 10:20 a.m. (0120 GMT) after the CH-47 helicopters dumped seawater onto the No. 3 reactor four times, the power plant’s operator Tokyo Electric Power Co. said.
The detected levels pose no harm to human health, according to the authorities.
The Self-Defense Force dispatched two CH-47 helicopters equipped with a device for dumping 7.5 tons of water, accompanied by another helicopter that is measuring radiation levels above the plant. The mission is part of efforts to cool down the storage pools at the No.3 reactor to prevent it from emitting highly contaminated radioactive materials.
The Tokyo Metropolitan Police Department also prepares to spray water with a water cannon truck later in the day.
Fears of radiation leaks are rising for the No.3 and No.4 reactors in the Fukushima plant, as the cooling systems at both reactors are not functioning.
There are six reactors at the Fukushima No.1 nuclear plant.
According to Kyodo News Agency, the government’s Nuclear and Industrial Safety Agency has said the first priority should be pouring water into the pools at the No. 3 and No. 4 reactors, which may be boiling and are not fully covered by roofs that would reduce any radiation leaks, since they were blown off by apparent hydrogen blasts earlier this week.
On Wednesday, a massive cloud believed to be steam rose from the No. 3 reactor and a second fire in two days broke out at the No. 4 reactor, suggesting rising temperatures at their fuel pools.
Although the No. 1, No. 2 and No. 3 reactors that were operating at the time of the March 11 quake halted automatically with jolts, their cores are believed to have melted as they lost cooling functions in an ensuing tsunami, said Kyodo.