| TOKYO, Sept 27
TOKYO, Sept 27 Japan's nuclear disaster
minister confirmed on Tuesday that the government soon wants to
lift an advisory for some areas near the quake- and tsunami-hit
Fukushima Daiichi nuclear plant, in a sign that the operator was
making progress with its cleanup work.
Operator Tokyo Electric Power (Tepco) last week
brought forward its goal of bringing crippled reactors at the
plant to a cold shutdown.
Minister Goshi Hosono said in parliament that the government
at the end of this week wants to lift an advisory placed within
a 20 to 30 km (12 to 18 miles) radius of the plant, which had
required residents to stay indoors or evacuate during
The Japanese government and Tepco said at a monthly review
of the Daiichi plant's cleanup timetable that they are now
aiming to bring the plants to a cold shutdown within this year,
instead of by January as initially planned, with their cleanup
work proceeding steadily.
WHAT IS COLD SHUTDOWN AND HOW DOES TEPCO DEFINE IT?
A cold shutdown is when water used to cool nuclear fuel rods
remains below 100 degrees Celsius, preventing the fuel from
reheating. But even when the temperature at the last remaining
reactor falls below 100 degrees, Tepco said it would not
automatically declare that a cold shutdown has been reached.
Under its definition of a cold shutdown, Tepco also said
that radiation leakage from the reactors has to be under control
and that the public's exposure to radiation should be largely
Declaring a cold shutdown will have repercussions well
beyond the plant as it is one of the criteria the government
said must be met before it begins allowing residents evacuated
from the area around the facility to return home.
Tepco said that the Daiichi reactors were emitting about 200
million becquerels of radiation per hour as of mid-September,
about one four-millionths of the amount seen in the days after
the March 11 disaster.
It said this translates to about 0.4 millisievert per year
of radiation measured at the fringes of the plant, below the 1
millisievert legal limit.
To further limit the spread of radiation Tepco has been
building a giant structure to cover the No 1 reactor. It will
also equip all three reactors with devices that would filter out
radioactive substances from the gasses they emit.
HOW HAS TEPCO GOT TO THIS STAGE?
After cooling systems were knocked out on March 11, causing
meltdowns of nuclear fuel rods at three of the plant's six
reactors, Tepco has been trying to cool the plant's reactors and
four of its spent fuel pools.
Immediately after the disaster Tepco tried to cool the
reactors by pouring in tens of thousands of tonnes of water,
much of it from the sea. But this left a vast pool of tainted
runoff, some stored in huge tanks and some in the basements of
the reactor buildings, that threatened to leak into the ocean.
It alleviated this problem by building a cooling system that
decontaminate the tainted water and then reuses some of it to
cool the reactors and spent fuel pools. The system has
repeatedly stalled but, as of Sept. 20, Tepco had treated about
97,000 tonnes of water. It estimates that 120,000 tonnes of
highly radiated water has accumulated at the plant.
Temperatures at all four of its spent fuel pools had fallen
to levels considered stable by August. As of Tuesday
temperatures at all the spent fuel pools were below 40 degrees.
The temperature at the No. 1 reactor dropped below 100
degrees in July and that of the No. 3 reactor fell below the
threshold at the start of September, leaving only the No. 2
reactor above boiling point. As of Tuesday the temperature at
the No 2 reactor was 101.4 degrees.
WHAT IS HAMPERING TEPCO?
The decontamination system was built in a hurry from a
patchwork of technologies from France, the United States and
Japan and its very complexity -- it has to remove oil and
radioactive substances and desalinate the water in different
steps -- has left it prone to breaking down.
Tepco also has to divert resources to other expensive and
labour intensive tasks, such as building a wall underground to
stop contaminated water from leaking into the ocean.
Providing a measure of how long the cleanup could take,
Tepco recently said it wanted to remove fuel stored at spent
fuel pools within three years and fuel from reactors within 10
WHAT ARE SOME OF THE CONSEQUENCES OF THE DISASTER?
Nearly 80,000 people have been forced to evacuate their
homes, most of them from a 20 km radius around the plant. Living
in fear of radiation has become part of life for residents both
near and far from the plant.
The crisis prompted then Prime Minister Naoto Kan to say
Japan should wean itself off nuclear power, and the parliament
passed a feed-in-tariff bill in August that promotes the use of
(Editing by Chris Gallagher)