Japan’s roadmap for cold shutdown of reactors

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.

PTI



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

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