Japan nuclear meltdown 'no Chernobyl'
2011-03-12 08:59
Fukushima - Japan warned of a meltdown on
Saturday at a nuclear reactor damaged when a massive earthquake and tsunami
struck the northeast coast, but said the risk of radiation contamination was
small.
Media reports estimate at least 1 300 people
may have been killed by the biggest earthquake ever recorded in Japan and then
a 10-metre tsunami that swept inland.
Experts said any threat of widespread
radiation leaks would be contained as long as the reactor's outer container is
intact.
State broadcaster NHK quoted officials as
saying there was no need to extend an evacuation area already set up around the
damaged plant.
Authorities have been scrambling to reduce
pressure at two nuclear power plants in Fukushima, 240km north of Tokyo,
damaged by the quake, which measured a massive 8.9, the biggest since records
began in Japan 140 years ago.
Jiji news agency quoted nuclear authorities
as saying that there was a high possibility that nuclear fuel rods at Tokyo
Electric Power's (Tepco's) Daiichi No 1 reactor may be melting or have melted.
Experts said if that is the case, it means
the reactor is heating up. If that is not halted, such as by venting steam
which releases small amounts of radiation, there is a chance it would result in
a rupture of the reactor pressure vessel.
But the risk of contamination can be
minimised as long as the external container structure is intact, they said. The
worry then becomes whether the quake has weakened the structure.
There has been no official word so far on
whether the structure was damaged in the quake.
Japanese officials and experts have been at
pains to say that while there would be radiation leaks, they would be very
small and have dismissed suggestions of a repeat of a Chernobyl-type disaster.
"No Chernobyl is possible at a light
water reactor. Loss of coolant means a temperature rise, but it also will stop
the reaction," Naoto Sekimura, a professor at the University of Tokyo,
said.
"Even in the worst-case scenario, that
would mean some radioactive leakage and equipment damage, but not an explosion.
If venting is done carefully, there will be little leakage. Certainly not
beyond the 3km radius."
