Tokyo, March 19: Workers should be able to reconnect a nuclear reactor to the electrical grid Saturday as they seek to restore cooling functions at a quake and tsunami-damaged Japanese power plant, the plant’s operator said.
The Tokyo Electric Power Company (TEPCO) said, however, that it would take time to bring the cooling systems back on line because of checks that need to be carried out on equipment at the plant in Fukushima that is home to six reactors, the Kyodo News agency reported.
Power was restored at reactors No.5 and No.6 through a diesel generator, and cables were being laid from reactor No.2 to a temporary substation, where power was brought Friday, TEPCO said.
Water cannons were used for a third day Saturday to spray water on the reactors and spent fuel pools at the plant, 250 km north of Tokyo, to lower their temperatures. Ninety tonnes of water were sent onto reactor No.3, Kyodo said.
Temperatures and pressure have risen at the reactors since their cooling systems failed after the coastal plant was swamped in the March 11 tsunami, leading to fears of reactor meltdown at the plant.
Hydrogen explosions, fires and releases of radiation have occurred, and core damage has been confirmed at three of the reactors.
Military helicopters flew over the facility Saturday so their heat-sensitive cameras could determine the temperatures at the reactors, the defence ministry said. Personnel on board were also to try to determine whether water remained at a pool of spent fuel in reactor No.4.
Rising temperatures have been recorded at the pool, increasing the risk of a nuclear chain reaction and releases of radioactivity.
Saturday’s work was carried out a day after Japan raised the rating of the nuclear accident up one step to level 5 on the 7-step International Nuclear Event Scale, labelling it an “accident with wider consequences” because reactor cores have been damaged.
The new rating puts the accident on the same level as the 1979 accident at Three Mile Island in the US, where a reactor core was severely damaged. The Chernobyl accident in 1986 in Ukraine rated a 7.
Meanwhile, TEPCO raised the limit of radiation exposure for its workers remaining at the plant from 100 millisieverts per shift to 150 after they exceeded the earlier limit, the public broadcaster NHK said.
The new limit applies to outside workers and was made because of the “unprecedented” nature of the crisis, which demands immediate action, TEPCO said.
The annual exposure limit for nuclear industry workers and uranium miners is usually 20 millisieverts, and nuclear experts said a dose of 150 millisieverts per shift would significantly increase cancer risks while levels of 1,000 millisieverts per hour can cause radiation poisoning.
NHK reported that TEPCO said it would not send any workers back in to the plant after exposures of more than 100 millisieverts.
TEPCO had evacuated all but 50 of its workers from the plant, but Friday, they got reinforcements of 120 personnel, TEPCO said.
Firefighters dousing the reactors were also getting relief. About 100 firefighters were dispatched to the plant Saturday to replace the first contingent of 139, NHK said.
The rotation was meant to safeguard the health of the emergency crews working in heightened radiation levels.
Meanwhile, TEPCO reported lower temperatures at the spent-fuel pool at reactor No.5, Kyodo said.
Reactors 5 and 6, which were under maintenance when the quake struck, have posed the fewest worries since the disaster, but temperatures has risen at the pool. The global nuclear watchdog, the International Atomic Energy Agency, reported Thursday that they were at 60 degrees Celsius when 25 degrees is normal.
In contrast, the temperature of the spent-fuel pool at reactor No.4 hit 84 degrees March 13 before its measurement devices failed.
–IANS