Japan’s roadmap for cold shutdown of reactors
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Last Updated: Tuesday, July 19, 2011, 15:07
Tokyo: Japan is set to release later on Tuesday an updated work schedule to achieve a "cold shutdown" of the crippled reactors at the Fukushima Daiichi power plant now that a new water circulation system has stabilised cooling operations and the risk of hydrogen explosions has been eliminated.

Prime Minister Naoto Kan told a parliamentary committee in the morning, "We are starting to see a tremendous critical condition heading toward a certain level of settlement," with the completion "almost as scheduled" of the initial phase of Tokyo Electric Power Co.'s timetable to bring the nuclear disaster under control.

Under the timetable initially drawn up by the utility, the cold shutdown is scheduled to be achieved by January at the latest, but Kan said earlier that the government and the plant operator would try their best to move up the schedule so that people forced to evacuate their homes because of the crisis can return.

Restoration efforts have continued since the March 11 magnitude 9.0 earthquake and tsunami hit the six-reactor complex and led the cooling functions of the reactors and spent nuclear fuel pools at the Nos 1 to 4 units to fail.

One of the key challenges during the past months has been how to deal with the massive amount of highly radioactive water that has accumulated in the reactor turbine buildings and nearby areas as an outcome of an emergency measure to keep injecting water into the reactors to cool the fuel inside.

Workers have now succeeded in installing devices to remove radioactive substances from the polluted water and recycle the decontaminated water to cool the crippled Nos 1 to 3 reactors.

Nitrogen, an inert gas, is also being injected into the three reactors to prevent hydrogen explosions from occurring inside the reactors, since such explosions may lead to the release of massive amounts of radioactive substances.

As for the No 4 unit, where all of its fuel rods had been stored in the spent fuel pool for maintenance work before the disaster struck, work is proceeding to create a system involving a heat exchange device to stably and efficiently cool the water inside the pool.

Kan said that the goals stipulated in the so-called "step one" of the restoration roadmap had been achieved by July 17 almost as scheduled.

But not all of the process has gone smoothly. Most notably, the key water decontamination devices, which started operating in June, have repeatedly faced problems such as water leakage.


First Published: Tuesday, July 19, 2011, 15:07

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