Development of ESRAD program for estimation of spatial radioactivity distribution based on kriging to support confirmation survey for site release

Shimada, Taro ; Ishigami, Tsutomu; Seki, Masaya; Mukai, Masayuki 

Nuclear Safety Research Center is developing a safety evaluation code system for exposure dose of public and workers at the stage of decommissioning nuclear facilities from planning to site release. ESRAD program for estimation of spatial radioactivity distribution based on kriging was developed to support confirmation survey for site release. ESRAD has functions such as estimation of radioactivity concentration distribution in the region from some measured points considering spatial correlation, calculation of estimated mean value and variance comparable to the criterion by mean kriging, and calculation of a minimum numbers of measured points to satisfy the estimated mean value with the criterion including uncertainty. In addition, ESRAD calculated the Cs-137 concentration distribution of sea bottom soil at the port of Fukushima Daiichi Nuclear Power Plant as an application example.