Evaluation of decontamination method conducted at children's parks located in Chiba prefectural housing complexes

This study evaluates the decontamination methods that were examined at 4 different children's parks located in Chiba prefectural housing complexes with measurement of 1cm dose equivalent rate, monitoring γ ray count rates of playground equipment surface, and determining the concentration of radioactive caesium in the soil. Two decontamination methods were examined. 1) Stripped and removed the topsoil containing radioactive caesium in the range of 3 - 5cm depth, subsequently coverage with uncontaminated soil to the thickness of 3cm to the subsoil layer. 2) Replacement with uncontaminated sand 20cm depth in sandbox. Range of the observed 1cm dose equivalent reduction rate were 41 - 91%. With the combination of these decontamination methods described above, the measurement value of 1cm dose equivalent rate decreased below 0.23μSv/h. The results of this study indicate that decontamination processes performed at children's parks showed significant efficacy. (author)