First detection of uranium from atomic bomb in Hiroshima soil

March 5, 2010

by Junji Akechi, Staff Writer

On March 4, it was learned that uranium believed to have been released from the atomic bombing of Hiroshima was, for the first time, detected in the soil collected in the aftermath of the blast. A researcher of the National Institute of Radiological Sciences (NIRS) in the city of Chiba presented the findings at a study session on the "black rain," held on Hiroshima University's Kasumi Campus in Minami Ward, Hiroshima. Though cesium had already been detected, uranium, which is technically difficult to find, had previously eluded detection.

Sarat Kumar Sahoo, a senior researcher at NIRS, has focused anew on the seven samples collected by a group of people, including the late Dr. Yoshio Nishina, who was a member of the Institute of Physical and Chemical Research and entered Hiroshima on August 8, 1945, or two days after the atomic bombing. Dr. Sahoo, through the use of mass spectrometry, detected uranium 236, which does not exist in the natural environment. He said that he is continuing to conduct analysis of the accurate radiation dose.

Tetsuji Imanaka, a research associate at Kyoto University Research Reactor Institute in Osaka Prefecture, praised the report, saying, "It has been technically difficult to detect uranium 236 so far. We have gained another piece of scientific evidence."

A research group of the Burnasyan Federal Medical Biophysical Center in Russia, with the use of the data obtained from the Semipalatinsk nuclear test site in the former Soviet Union, made a trial calculation of the radiation dose of internal exposure caused by the black rain in Hiroshima. The group has estimated that if an infant aged one or under continues to drink the milk of a goat which feeds on grass contaminated by the black rain the exposure dose in the baby's thyroid gland will amount to one Gy at the maximum.

(Originally published on March 5, 2010)