Sunday 13th March, 04:30 PM JST
Japanese authorities scrambled Sunday to control overheating reactors at the troubled Fukushima No. 1 nuclear power plant, injecting sea water into them and reducing the pressure inside, top government spokesman Yukio Edano said.
While acknowledging that the core of the No. 3 reactor at the plant may have been deformed due to overheating, the chief Cabinet secretary denied it has led to a ‘‘meltdown,’’ a critical situation where fuel rods have melted.
Edano warned, however, that a hydrogen explosion similar to one that occurred at the No. 1 reactor at the same facility nearby on Saturday could occur at the No. 3 reactor because large amounts of hydrogen were created when the water injection procedure briefly ran into trouble.
The plant’s operator, Tokyo Electric Power Co, began injecting fresh water into the reactor to deal with the problem that the tops of MOX fuel rods were 3 meters above the water in the reactor following a magnitude 9.0 earthquake which hit northeastern and eastern Japan on Friday.
But it began injecting sea water after trouble developed with a fresh water pump, a step that will lead to the reactor’s dismantlement.
Radiation around the reactor measured 1,557 micro sievert at 1:52 p.m., Edano said, adding the figure went down to 184 about 50 minutes later. He dismissed concerns that the radiation level would affect human health.
Meanwhile, radiation monitored at the Onagawa nuclear power plant in Miyagi Prefecture on the Pacific coast shot up on Sunday, Tohoku Electric Power Co said, adding that it was likely caused by radioactive substances let out at the troubled Fukushima No. 1 nuclear power plant in Fukushima Prefecture.
Radiation levels were very low but about 400 times as high as in normal times, the power supplier said, dismissing the possibility that the Miyagi plant was to blame.
The Nuclear and Industrial Safety Agency said Tokyo Electric Power acknowledged that the No. 3 reactor of the Fukushima plant had lost its cooling functions, while 19 people at a nearby hospital were found to have been exposed to radioactivity, in addition to three cases of exposure recorded Saturday.
It was the sixth reactor overall at the Fukushima No. 1 plant and the Fukushima No. 2 plant, which is located just south of the No. 1 plant, to undergo cooling failure since the massive earthquake and ensuing tsunami struck Japan on Friday.
The disaster raised fears of radioactive leaks from the plants after cooling systems there were hampered, most seriously at the No. 1 reactor.
An explosion Saturday at the No. 1 plant blew away the roof and the walls of the building housing the No. 1 reactor’s container.
The government and nuclear authorities said there was no damage to the steel container housing the troubled No. 1 reactor, noting that the blast occurred as vapor from the container turned into hydrogen and mixed with outside oxygen.
Tokyo Electric Power has begun new cooling operations to fill the reactor with sea water and pour in boric acid to prevent an occurrence of criticality. Edano said in a news conference Sunday morning that there had been no major changes in the results of radioactivity monitoring near the No. 1 reactor.
No significant changes in radiation levels have been monitored.
Following the explosion, the authorities expanded from 10 kilometers to 20 km the radius of the evacuation area for residents living in the vicinity of the Fukushima plants.
The Fukushima prefectural government said Saturday that three people had their clothes contaminated with radioactive substances while fleeing from the No. 1 nuclear plant.
The Fire and Disaster Management Agency said Sunday that 15 people were found to have been contaminated at a hospital located within 10 km of the No. 1 reactor. Edano said there was a possibility that nine people who fled on a bus had been exposed to radioactivity.