Risk Management on Radiation Under Prolonged Exposure Situation - Focusing on the Tokyo Metropolitan Area in Japan Under the TEPCO Fukushima dai-ich NPP Accident -

Examples and experiences of risk management on radiation under prolonged exposure situation are shown. The accident of the Fukushima dai-ichi nuclear power plant after the great east Japan earthquake (11 March, 2011) elevates background level of environmental radiation around the east Japan. For example, ambient dose equivalent rate around Tohkatsu area next to Tokyo located about 200 km-south from the plant, is about 0.1-0.6 micro-Sv $h^{-1}$ mainly due to $^{134}Cs$ and $^{137}Cs$ falling on the ground soil. This level is about double or up to ten times higher than the genuine natural level around the area. International Commission on Radiological Protection (ICRP) recommends how to face the existing exposure situation; that is the prolonged exposure situation. Referring to ICRP's reports and/or related international/domestic documents, we have been discussing and acting to gain public's safety and relief, who have a possibility to be exposed to prolonged lower-dose radiation. Here, we introduce our several experiences on risk management, especially focusing on risk communication, radiation education to public, and stakeholder involvements into making decision in local governments on radiation protection, relating to the accident.