The purpose of this study is to improve a quick method for estimation of 131I concentrations in the air using data measured by monitoring posts in case that a nuclear disaster occurs. In this method, 131I concentrations were estimated by multiplying 131I count rates of cloud-shine measured with Na(Tl) detector by concentration conversion factor. A previous study suggested that it was difficult to determine passing-through time of plume from temporal change of 131I count rates or dose rate. Our study applies the method for estimating passing-through time of plume from temporal change of noble gas counts. The 131I concentrations in the air at Oarai center, Japan Atomic Energy Agency resulting from the accident at the Fukushima Daiichi Nuclear Power Station were estimated by proposal technique. The result of comparison of this method with sampling method for 131I concentrations in the air were within factor 3.
As a countermeasure against the nuclear disaster that took place in Fukushima, Japan in mid-March, 2011, a number of monitoring posts, including portable ones, have been introduced particularly to Fukushima prefecture among others. First, in this paper the damages and countermeasures concerning principally the air dose-rate monitoring systems that were prepared prior to the Great East Japan Earthquake, which triggered the giant tidal waves, and then caused the nuclear accident are reviewed. The tidal waves also damaged the radiation monitoring systems in Fukushima prefecture so severely that for nearly half a month following the nuclear accident there were hardly any organized monitoring activities within the 20 km range of the nuclear power plant. Nevertheless, outside the 20 km range the promptly constructed air dose-rate monitoring system could largely track main flows of radioactive plumes emitted from the nuclear plant. Starting from this situation, in this report, how a large-scale monitoring system with over 600 portable monitoring posts among others has been developed in Fukushima prefecture is reviewed. Furthermore, the operation records of the newly constructed monitoring system are analyzed. Consequently, it is revealed that more missing data tend to emerge at considerably high rates in every winter, and the trend is still maintained.
This paper provides a broad overview of the regulatory framework on medical radiation safety and current medical radiation protection issues such as diagnostic reference levels, shielding calculations for X-ray facilities, accidental excessive emissions of gaseous 18F, security of radioactive sources, and induced radioactivity in Japan, and discusses the impact from the 2011 Fukushima nuclear disaster regarding risk communication issues. The Fukushima nuclear disaster has had an inevitable impact on issues related to protection from medical radiation. However by taking this situation, communication activations on radiation are being accelerated in certain initiatives utilizing quantitative risk expression on the premise of seeking fairness for risk allocation to the society.