Influence of Nuclear Reactor Accident at Chernobyl' on the Environmental Radioactivity in Toyama

Abstract

The environmental radioactivity caused by the reactor accident at Chernobyl'was investigated from May 7 to May 31 of 1986 in Toyama. Measurement of radioactivities in airborne particles, rain water, drinking water, milk, and mugwort are carried out by gamma-ray spectrometry (pure Ge detector; ORTEC GMX-23195) . Ten different nuclides (¹⁰³Ru, ¹⁰⁶R, ¹³¹I, ¹³²Te-I, ¹³⁴Cs, ¹³⁶Cs, ¹³⁷Cs, ¹⁴⁰Ba-La) are identified from samples of airborne particles. In the air samples, a maximum radioactivity concentration of each nuclide is observed on 13th May 1986. The time of the reactor shut-down and the flux of thermal neutron at the reactor were calculated from ¹³¹I/¹³²I and ¹³⁷Cs/¹³⁴Cs ratio.
The exposure dose in Toyama by this accident is given as follows: internal exposure; [thyroid] adult-59 μSv, child-140 μSv, baby-130 μSv, [total body] adult-0.2 μSv, child, baby-0.4μSv, external exposure; 7 μSv, effective dose equivalent; adult-9μSv, child-12 μSv, baby-11 μSv.