Estimation of air dose rate using measurement results of monitoring posts in Fukushima Prefecture

For the return of the residents evacuated from the vicinity of the Fukushima Daiichi Nuclear Power Plant, it is necessary to estimate how the air dose rate in the evacuation order area decreases. For this purpose, we developed a method of estimating the temporal change in the air dose rate at the location with sparse (in time) measurements by using continuous measurement data from a nearby monitoring post. This method determines an observation model from the correlation between sparse data at the target location and dense data at the monitoring post based on a hierarchical Bayesian model. The developed method was validated against the air dose rate measured at the monitoring posts in Fukushima Prefecture from 2012 to 2017. The findings showed that the developed method can predict the air dose rate at almost all target locations with an error rate of less than 10%. Moreover, the developed method often gives better results than other estimation methods. (author)