In order to clarify biological effects on whole body due to damage of cells by ionizing radiation, authors used the following assumption; absorbed dose was allocated only to ionization of water molecule in a place of DNA damage. The number of DNA damage calculated from ionized water was about 2.6 times of previously reported ones. The value calculated is considered to correspond to the maximum number of DNA damage. When all deaths due to spontaneous cancer of natural occurring were assumed due to only DNA double-strand breaks (DSB) by ionizing radiation, the number of DSB was over-estimated to be about 1,500-2,000 times of the number of DSB necessary for death due to cancer produced by acute exposure of ionizing radiation. It would be necessray to consider at least the dose rate effect for biological effects on human body when estimating the simply accumulated dose of low-level ionizing radiation.
In July 2015, during the renovation of the facility, the Isotope Science Center in the University of Tokyo was found to have exceeded its storage capacity of unsealed radiation source. This storage capacity overshoot was resolved by discarding and transferring the radiation source to the Japan Radioisotope Association. In addition, radiation safety management was re-inspected by on-site inspection conducted by the Radiation Regulation Office of Nuclear Regulation Authority, Japan. This case report included instructions on how to improve potential deficiencies in radiation safety management.
In 2012, JAEA has established a laboratory in Fukushima-city to implement radioactivity analysis of environmental samples. Key nuclides measured in this laboratory are 134Cs and 137Cs (radiocesium). For the purpose, situation of radiocesium inflow into the laboratory building and its effects on the analyses were investigated based on the gamma-spectrometry with germanium detectors. As a result, the surface densities of radiocesium in the laboratory was found to be far below the minimum detectable activities of survey instruments routinely used for the radiation control purposes.
As an example of public health emergency response for a radioactive source, the case of public health center response for the detection of a radioactive orphan source in a public park in Toshima, Tokyo was reported. Issues were categorized as (1) lack of experiences of radiation emergencies of the public health center, (2) diversity in residents of issues regarding radiation and (3) difficulties of risk communication. It was experiences that importance of collaboration with a public health center and an expert organization and engagement with local residents to strengthen trust relationships between local government and residents rather than by persuading safety.