Japanese authorities published on July 19 the first detailed timeline for decommissioning the damaged reactors of the Fukushima No. 1 nuclear power plant but offered no dates for lifting the evacuation zones around the stricken facility.
Japanese authorities published on July 19 the first detailed timeline for decommissioning the damaged reactors of the Fukushima No. 1 nuclear power plant but offered no dates for lifting the evacuation zones around the stricken facility.
In the first preparatory phase of decommissioning, expected to be completed within three years, nuclear fuel will be removed from fuel pools at the plant and concrete shield walls will be dug into the ground to prevent radiation-contaminated groundwater from leaking into the sea.
The government and the plant's operator, Tokyo Electric Power Co. (TEPCO), which jointly announced the new road map, said the amount of radioactive material being discharged into atmosphere had fallen by the end of June to 1/2,000,000th of that escaping immediately after the initial accidents at the plant.
Officials said the initial goal of the disaster response effort, to achieve stable cooling of the reactors, had been achieved, as expected, by mid-July. The installation of a circulating cooling system, which treats radiation-contaminated water and then uses it to cool down the reactors, was critical in achieving stable cooling, they said.
The next stage, scheduled to be concluded some time between October and January, will aim at achieving a "cold shutdown" of the reactors.
The plan specifies for the first time what the Japanese authorities mean by a "cold shutdown," which is one of the key conditions for lifting the evacuation zones around the plant.
According to the new document, it will require a drop in the temperature in the bottom portions of the reactors' pressure vessels to 100 degrees or lower and a legally stipulated reduction in radiation levels at the borders of the nuclear power plant compound to one millisievert or lower a year.
Excluding the radioactive materials already discharged, the radiation currently being released is equivalent to about 1.7 millisieverts per year near the border of the nuclear plant's compound.
After cold shutdowns have been achieved, TEPCO and the government will consider plans to decontaminate soil and work with local governments to lift evacuation zones around the plant. They will move onto the first preparatory phase of decommissioning, while monitoring the reactors and keeping them in the "cold shutdown" state for the following three years.
A previous official plan, published by the Japanese authorities in April, did not define what was meant by a "cold shutdown" and was criticized for its vagueness. The new plan is more specific but still offers no dates for when evacuation zones will be lifted. It only says that the government will consider lifting restrictions after cold shutdowns of the reactors.
The evacuation restrictions cover all areas within a radius of 20 kilometers of the power plant and additional "keikakuteki (planned)" evacuation zones beyond that radius that are considered particularly at risk from radiation.
Goshi Hosono, the state minister responsible for handling the nuclear crisis, said conditions for lifting the "evacuation stand-by zones," where residents have been told to be ready for evacuation in an emergency, were likely to be met in early August. He said the cooperation of local governments would be required to lift those restrictions.