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Researchers from home and abroad report on research results of black rain

by Junji Akechi, Staff Writer

On March 3, Hiroshima University's Research Institute for Radiation Biology and Medicine (RIRBM) held a study session on the "black rain" that fell in the aftermath of the atomic bombing of Hiroshima on the university's Kasumi Campus in Minami Ward, Hiroshima. Researchers from home and abroad are scheduled to present 13 research results of the rainfall area and the radiation dose of the black rain through March 4.

Evgeniya Granovskaya, a Russian researcher of the Burnasyan Federal Medical Biophysical Center in Moscow, estimated the radiation dose accumulated for a year from August 6, 1945, to be up to 46 mGy, based on the data that 0.8 percent of fission products released by nuclear tests of the former Soviet Union during the 1950s fell to the ground.

At the end of February, a research group led by Tetsuji Imanaka, a research associate at Kyoto University Research Reactor Institute in Osaka Prefecture, estimated the radiation dose by the black rain to be "50 mGy at a maximum, or about 50 times as much as the annual dose limit set by the Japanese government," after analyzing the soil in the city of Hiroshima. Masaharu Hoshi, a professor at RIRBM, praised the report by the Russian researcher, saying, "The estimate will be one of the factors backing the data presented by Professor Imanaka."

On the day, there were also reports on the estimate of the height of the mushroom cloud that formed over the city of Hiroshima after the atomic bomb exploded and the change in the black rainfall area over time.

(Originally published on March 4, 2010)

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