Fukushima accident

The author presents the Fukushima accident and details the composition and hazards of the radioactive plume that followed the degassing of the reactors. The plume was composed mainly of I¹³¹ (T = 8.02 days), Cs¹³⁴ (T = 2.2 years) and Cs¹³⁷ (T = 30.2 years). In the humane body the Iodine set (30%) in the thyroid gland is eliminated with an effective period of 7 days, the rest of the iodine set in other parts of the body is mostly excreted by kidneys with an effective period of 6 hours. Concerning cesium, its radio-toxicity is due to internal irradiation and is exacerbated by the fact that a great part of cesium is assimilated in the body as an analog of potassium. The ingestion of 1 becquerel of Cs¹³⁷ corresponds to a 12 nSv absorbed dose. A list of likely radiation hazards is given according to the value of the dose. (A.C.)