快猫短视频

RADIOACTIVE food and jewellery from homes near the Tokaimura nuclear plant in
Japan are revealing the impact of the accident there last year. Local people
were exposed to radiation levels up to 30 times safety limits because they were
not evacuated until five hours after the accident occurred, say Japanese
scientists.

The first independent studies of Japan鈥檚 worst nuclear accident, which has
already caused the death of two workers from multiple organ failure, also
suggest that radiation doses outside the 350-metre evacuation zone breached the
safety limit.

In Tokaimura, northeast of Tokyo, a company called JCO was making reactor
fuel rods from enriched uranium. At 10.35 am on 30 September, workers
accidentally mixed together enough uranium to start a chain reaction, causing a
burst of neutron and gamma radiation that lasted for 20 hours
(快猫短视频, 9 October 1999, p 4).

But it wasn鈥檛 until 3.30 pm that the local authority began to evacuate the
301 people who lived within 350 metres of the plant, and there was no monitoring
of high-energy neutrons for the first six hours after the accident. 鈥淭he
emergency response at Tokaimura was grossly inefficient,鈥� says Murdoch Baxter, a
radiation expert and editor of the Journal of Environmental
Radioactivity.

This week, the journal publishes 22 reports by scientists who have
reconstructed radiation levels from scanty official measurements and samples of
metals and food. Baxter concludes that 50 workers within 100 metres of the plant
could have received doses of 100 millisieverts or more. According to Britain鈥檚
National Radiological Protection Board, one in 200 people exposed to 100
millisieverts contracts cancer as a result.

Dudley Goodhead, director of the Radiation and Genome Stability Unit at
Harwell in Oxfordshire, says that 鈥渨ith good fortune鈥� no one will contract
cancer as a result of the accident. But he adds that the health risks of
high-energy neutrons are poorly understood. 鈥淭he work of these independent
scientists is very important to establish accurately the doses.鈥�

Combining official measurements with evidence from Hiroshima and Nagasaki of
the shielding that houses provide, Jun Takada from Hiroshima University
calculates that residents within the 350-metre zone would have received a
maximum dose of 30 millisieverts outdoors, or 12 millisieverts indoors. The
annual safety limit for the public recommended by the Stockholm-based
International Commission on Radiological Protection is 1 millisievert.

Extrapolating from the sparse official monitoring data, trade union
scientists from the Japan Atomic Energy Research Institute at Tokaimura reckon
that the average neutron radiation dose 350 metres from the plant was 2
millisieverts. They say that doses to some people who were not
evacuated鈥攂ecause they lived farther away鈥攎ay have exceeded the
safety limit.

Kazuhisa Komura from Kanazawa University measured radioactive isotopes in
their jewellery, coins and cutlery. 鈥淕old was the most sensitive way of
evaluating the neutron flux,鈥� he says. One reading in a gold necklace worn by a
woman working more than a kilometre from the accident was 30 times as high as
normal. It turned out that this was because she returned twice to her house 350
metres from the plant to feed her dogs.