福島原子力発電所の事故からみた放射性同位元素と放射線

The words“ radiation and radioactivity” have been become famous after the Fukushima Daiichi nuclear disaster. Alfa, beta, gamma and neutron rays irradiated from radioisotopes are well known to the world. Alfa and beta rays have weak penetration. Alfa and beta rays are stopped by a sheet of paper and a thin aluminum plate, respectively. And those are taken into account at internal exposure because all energy from those rays is absorbed in the surrounding tissues. If DNA strand in the cell is broken by the energy absorbed, some radiation hazard may occur. The units of radiation became also famous. Becquerel (Bq), Sievert (Sv) and Sv/h are addressed under a leaflet for the pubic by public office and citizen has been to monitor the radiation dose contained in food and water. In the early stage 131-I (iodine) having about 8 days half-life period was emitted into the air and many people were exposed. Recently the 131-I at that time was decayed but two types of radioactive cesium 134-Cs and 137-Cs remained. Because 134-Cs and 137-Cs have about 2 years and 30 years halflife period respectively and emit beta and gamma ray, no radiation effect will require hundred years. Therefore I hope that many people will acquire the greater knowledge of radiation.