Improvement of Estimation of ¹³¹I Concentrations in the Air Using Data Measured by Monitoring Posts Applied by Determination of Passing-through Time of Plume Using Noble Gas Counts

Abstract

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.