Geostatistical deconvolution to find and locate punctual sources

Abstract – The purpose of geostatistics deconvolution is to improve the processing of nondestructive radiological data (dose rate measurement, in situ gamma spectrometry…) using an advanced algorithm. The objective is to better estimate the real activity content of the measured object (tank, pit, concrete slab, wall…). This deconvolution method can be used for Very Low-Level Waste characterization to High-Activity cases.
Due to the fact input data are not punctual (nor only the average value on a supposedly homogeneous area), the spatial response of the probe can advantageously be taken into account to benefit from the spatial correlation between partially overlapping measurements. This weighting function is derived from the probe characteristics as well as from the measuring conditions (distance to the surface, possible collimation…). Therefore, the map of the radiological sources can be directly obtained from the map of the radiation by deconvolution. This is a smart resolution of an inverse problem. This paper illustrates first and promising results on a simple case with two punctual sources. This improved knowledge of the radiological state of the characterized surface then impacts the destructive sampling campaign, necessary for the full radiological characterization (including hard-to-detect radionuclides).