Japan's nuclear crisis a long way from over


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Problems continue to arise at the crippled Fukushima Daiichi nuclear power plant in Japan, despite progress in restoring the power needed to cool down its overheating reactors.


Japan's Prime Minister Naoto Kan bows in front of the Japanese flag with a black mourning cloth during a news conference at his official residence in Tokyo March 25, 2011. Kan said on Friday that the situation at a quake-damaged nuclear plant in northeast Japan remained very precarious. [Xinhua]
In recent days, injuries to workers, black smoke rising from No. 3 reactor and abnormal radiation have come one after another.

Some experts say the crisis might not end soon, while others insist its effects will be limited.

The crisis arose from the shutdown of the plant's cooling systems, which are critical to bringing down temperatures in the reactors' cores and stabilizing its nuclear fuel. The systems shut down after the March 11 earthquake and ensuing tsunami wiped out the power supply.

Workers are making efforts to bring the six-reactor facility's cooling systems back online and are spraying stricken reactors with seawater to cool damaged reactors and fuel rods

The Fukushima Daiichi nuclear power plant uses boiling water reactors, which went into emergency shutdown when the earthquake hit. The backup power started automatically to circulate cooling water to carry away the residual heat.

However, the earthquake destroyed the external power supply of the nuclear reactor. The emergency diesel power generators also failed when the tsunami arrived.

With the cooling system shut down, the residual heat built up, bringing down the water level of the fuel pool and threatening eventual core meltdown.

In 1979, a partial core meltdown occurred at Three Mile Island in the United States due to a cooling system failure. It remains the most severe nuclear leak accident in the country and forced the evacuation of at least 150,000 local residents.

Fortunately, Fukushima workers on Monday reconnected power lines to all six reactors, marking a critical first step in getting the overheated reactors under control after days of public anxiety. But much still needs to be done before electricity can be turned on. It is not clear what condition the equipment is in.


Staff members of Tokyo Electric Power Co. (TEPCO) discuss about strategies at the disaster countermeasures unit in Fukushima City, Japan, March 25, 2011. [Huang Xiaoyong/Xinhua]
The plant's operator, Tokyo Electric Power Co. (TEPCO) admitted Friday it might take at least another month to achieve a cold shutdown of all reactors, when temperatures inside fall below boiling point and its cooling systems are back at atmospheric pressure.

"We are still in the process of assessing the damage at the plant, so we can't put a deadline on when the cooling operations will work again. It may take more than a month, " a TEPCO spokesman said.

The biggest worry for the public is radiation leaking from the reactors. Previously, in order to avoid damaging the reactors, the plant released the potentially devastating build up of pressure, with some radioactive particles emitted into the air.

According to the latest news, a possible breach has been found in No. 3 reactor, which might be a crack or a hole in the stainless steel chamber of the reactor core or in the spent fuel pool that is lined with several feet of reinforced concrete.

Suspicions of a possible breach were raised when two workers were exposed to radiation 10,000 times the normal level and suffered skin burns while dealing with an emergency at the No. 3 reactor.

The two workers, in their 20s and 30s, who were laying power cables with their feet submerged in the water of the turbine room at the troubled No. 3 reactor, sustained injuries, including skin burns caused by beta rays. This suggests the reactor or its spent nuclear fuel pool is damaged.

A total of 17 workers have been exposed to radiation exceeding 100 millisieverts since the March 11 earthquake.

Radioactive leaks were detected after a series of explosions and fires at four of the plant's six reactors and the government on Friday suggested residents living within a 20 to 30 kilometer distance of the stricken plant voluntarily evacuate the area.

The radiation leak from the plant has contaminated sea water, food produce, milk and water supplies in regions as far away as Tokyo, 240 km southwest of the plant.

However, some experts said, with continued follow-up measures, the situation was still under control. Judging from historical experience, the effects of the nuclear leak would be limited.

Japan Nuclear and Industrial Safety Agency currently only rates Fukushima at 5 out of 7 on its warning level, the same level as the 1979 accident at Three Mile Island.

Many international organizations also said people outside Japan need not worry about the health effects of the nuclear leak.