Paris: Radioactive contamination levels from
Japan`s crippled Fukushima nuclear plant have fallen sharply
since the accident but will be "chronic and lasting" for many
years, a French watchdog said today.
"The initial contamination linked to the accident has
greatly declined," Didier Champion, crisis manager at the
Institute for Radiological Protection and Nuclear Safety
(IRSN), told reporters almost a year after the disaster.
"That doesn`t mean that there won`t be any more, far from
it. Today, and for many years to come, we will have a
situation of chronic and lasting contamination of the
It was essential for Japan to maintain vigilant monitoring
of fruit, milk, mushrooms, game and fish, Champion said.
"There are risks of chronic exposure at low dosage, and
without care this can build up over time," he warned.
The March 11 catastrophe saw the plant swamped by a
quake-generated tsunami that knocked out coolant pumps,
triggered hydrogen explosions and caused three of its six
reactors to suffer meltdowns of nuclear fuel.
Radioactive elements were spewed into the air by the blast
and into the sea by cooling water that was pumped in in a
desperate attempt to keep the overheated reactors under
The IRSN said the main radioactivity leaks occurred
between March 12-25 in about 15 incidents, "of which the
biggest probably took place before March 15".
It gave a provisional estimate that 408 peta-becquerels,
or 408 million billion becquerels, of radioactive iodine had
been emitted into the air.
This was 10 times lower than in the 1986 Chernobyl
disaster in Ukraine, the world`s worst nuclear accident.
The iodine releases posed a sharp but temporary hazard as
the element quickly decays. A bigger problem, the IRSN said,
was caesium-137, a long-lasting element which takes around 30
years to decay to half its level of radioactivity.
Caesium of all kinds released at Fukushima was estimated
by the agency at 58 peta-becquerels, or three times less than
Chernobyl. Caesium 137 accounted for 21 peta-becquerels.=
Of around 24,000 square kilometres of land contaminated by
caesium 137, only 600 sq kms breached a safety threshold of
600,000 becquerels per square metre, the IRSN said.
This, again, was only a fraction of the territory
contaminated by caesium after Chernobyl.
However, there remained "hot spots" of contamination, up
to 250 kilometres away, where radioactive particles had been
deposited by the weather.