Analysis of the effect of the chemical composition ratio of soil samples on pretreatment methods (direct method, AMP) and MDA

Abstract

By analyzing the chemical composition of soil samples and effectively removing spontaneous radionuclides of cesium isotopes from the samples using the direct method and AMP, the MDA value is measured and compared with the direct method, and how much it can be reduced is analyzed and evaluated. A standard soil sample was made by diluting 37 kBq/kg of 134Cs aqueous solution in distilled water to prepare 500, 1000, 2500, and 5000 Bq/kg of aqueous solution at the Institute of Standard Science. As a result of AMP pretreatment using soil samples and reducing the loss of cesium isotopes that may occur during chemical pretreatment using AMP reagents, a satisfactory result of an average of 89.5% was obtained. As a result of measuring the standard soil sample after calibration, a very satisfactory result could be derived with a difference of at least 0 to 5 Bq/kg from the standard sample. In addition, the efficiency measurements in the three methods (direct method, AMP) after correction showed uncertainty within 3% compared to Monte Carlo values, which matched well. Several factors, such as background, sample measurement time, and recovery rate, affect the MDA value, especially when the radioactivity concentration is above 2500 Bq/kg, by shortening the measurement time, MDA values can be reduced. As the amount of sample increased, the efficiency decreased clearly due to the self-absorption effect. Therefore, it was confirmed that the higher the soil type and component ratio, the more the radioactive concentration was affected.