An analysis of Japan radiation protection measurements after the Fukushima nuclear accident

On March 11th 2011, Japan was struck by a devastating earthquake followed by a tsunami wave that took the lives of thousands and started a major nuclear accident in the Fukushima Dai-ichi power plant complex. Right from the beginning, the information published by the Japanese government and by the International Atomic Energy Agency (IAEA) was followed by a team of experts at the Institute for Radiation Protection and Dosimetry (IRD) of Brazil. Radiation monitoring data, such as radionuclide activity concentration in water and food, ambient dose rate and fallout concentration in specific cities have been compiled and analyzed, with emphasis on dose limits established by Brazilian regulatory authority. A computer code for dose assessment, developed at the IRD and based upon the IAEA documents TECDOC-1162 and TECDOC-955, was used to assess the doses due to intakes of radionuclides and external exposure for individuals of different age groups. The IAEA model predictions for the ambient dose rates, when the fallout is known, are compared with the measured values in different cities. The Japanese recommendations for evacuation, sheltering and restriction of food and water consumption are evaluated with regards to the Brazilian limits defined in the CNEN NN 3.01 standard. (author)