Japan iodine release lower than Chernobyl-expert

VIENNA/OSLO, (Reuters) – The release of two types of  radioactive particles in the first 3-4 days of Japan’s nuclear  crisis is estimated to have reached 20-50 percent of the amounts  from Chernobyl in 10 days, an Austrian expert said today.
The calculations published by Austria’s Central Institute  for Meteorology and Geodynamics may add to growing concern in  Japan and elsewhere over the contamination of food products such  as milk and vegetables in areas near the Japanese reactor site.
On Tuesday, France’s IRSN radiation protection and nuclear  safety institute estimated that leaks of radiation from the  Fukushima plant crippled by the March 11 earthquake and tsunami  represented about 10 percent of those from Chernobyl, the  world’s worst nuclear disaster, in 1986.
Astrid Liland, of the Norwegian Radiation Protection  Authority, said there was a peak in radiation in Japan a couple  of days ago and levels had since decreased.
“Radiation measurements from around Japan today are not very  elevated,” she said in Oslo.
In Vienna, the Austrian institute’s Dr Gerhard Wotawa  stressed that the two isotopes from Fukushima he had sought to  estimate — iodine-131 and caesium-137 — normally make up only  one tenth of total radiation.
Unlike the Fukushima crisis, at Chernobyl, in what is now  Ukraine, the reactor was blown apart and spewed heavily  radioactive fuel core material into the atmosphere.
Another key difference between the two was that most of the  radioactivity from the Japanese plant was dispersed across the  Pacific, not over land, Wotawa said.
Based on measurements made at monitoring stations in Japan  and the United States, Wotawa said the iodine released from  Fukushima in the first three-four days was about 20 percent of  that released from Chernobyl during a ten-day period.
For Caesium-137, the figure could amount to some 50 percent.

DRIVING FORCE
Wotawa said it was difficult to make day-by-day comparisons  with Chernobyl, but he added: “For caesium and iodine … the  source terms (amounts released from the two accidents) are not  so different.”
He said iodine — linked to cancer if found in high doses —  and caesium were both “volatile substances” which escape  relatively easily when there are nuclear accidents.
Only minor traces of radiation have been detected in  countries outside Japan, but the U.N. nuclear watchdog this week  said “high levels of contamination” have been measured around  the Fukushima plant, about 250 km north of Tokyo.
Japanese authorities advised parents today not to let  infants drink tap water in the capital because of raised  radiation levels, and the United States became the first nation  to block some food imports from Japan.
Officials from the U.N. nuclear watchdog said a major  difference between Fukushima and Chernobyl was in the  geographical extent of radioactive contamination.
In Chernobyl, the explosion took place because the nuclear  reaction was not halted, unlike in Fukushima, where the reactor  was automatically shut down when the earthquake occurred.
“In the case of Chernobyl, with all the graphite that caught  fire, it was a driving force to distribute radioactivity high in  the air which carried the plume,” Andrew Graham, of the  International Atomic Energy Agency (IAEA), said.

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