Development of ESRAD2 program for estimation of spatial radioactivity distribution based on Kriging; User's manual

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

JAEA-Data/Code 2015-019, 122 Pages, 2015/12

JAEA-Data-Code-2015-019.pdf:3.65MB

In ensuring compliance with the criterion of site release as the final stage of termination of decommissioning of nuclear facilities, it is supposed to confirm the radioactivity concentration obtained by measurement in the site is less than or equal to the concentration corresponding to the criterion. It is needed to estimate the distribution and mean of radioactivity concentration in the evaluation unit using a number of measured data. It is further needed to compare the estimated result with the concentration corresponding to the criterion of site release and to decide if the evaluation unit should comply with the criterion. The estimated result exhibits uncertainty depending on the number of measurement points, which results in a certain probability of the occurrence of decision error according to the uncertainty. It is important to decide the number of measurement points required by revealing a relationship of the error probability to the number of measurement points for site security. We have developed the ESRAD2 (Estimation of Spatial RadioActivity Distribution program version 2), which is an extended version of the existing ESRAD, for estimating the mean of radioactivity concentration and calculating the number of measurement points required according to the error probability. This report describes a method for ensuring compliance with the criterion of site release, structure and functions, input file format, output examples, execution method of ESRAD2, and sample run with ESRAD2.

Introduction of external drift kriging into the program for estimating radioactivity distribution ESRAD code for supporting final survey of site release

Shimada, Taro; Nabekura, Nobuhide*; Takeda, Seiji

no journal, , 

It is necessary to confirm that the public radiation exposure dose by residual radioactivity is less than the criteria after site release at the completion of decommissioning of nuclear facilities. In order to obtain the radioactivity distribution in the site to evaluate the public dose, we have been developing a computer code, ESRAD, which estimates the radioactivity distribution from limited measurement data of radioactivity of soil in the site using the kriging. In this study, we improved the code by introducing the external drift kriging where dose rate distribution obtained before final survey was used as supplement information. Some calculations were carried out supposing hypothetical radioactivity distribution. As a result, the external drift kriging using dose rate distribution may improve the estimation results rather than the ordinary kriging.