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Assessment of Exposure Doses and Decontamination


How is the concentration of radioactive cesium measured in air? What is the radiation dose by breathing?

Continuous monitoring of cesium concentrations in air has been conducted at many spots in different environments in Yamagiya District, Kawamata Town. The concentration of Cs-137 has been lower than 0.001 Bq/m3 since several months after the accident. If a person constantly breathes air with radioactive cesium of 0.001 Bq/m3, the radiation dose in a year is estimated to be less than 0.001 mSv.

Fig.1 Measurement of Radioactive cesium in the atmosphere

Continuous monitoring og radioactive cesium in many spots with different environments has been conducted.

Concentration of 137Cs in the atmosphere

Fig.2 Concentration of 137Cs in the atmosphere

The concentraion of 137Cs in the atmosphere decreased in the months after the accident.After that, the concentration has been changing,but the values has never exceeded 0.001 Bq/m3.