Evaluation of the efficacy of decontamination methods conducted at athletic site Bouken-no-toride located in Chiba Prefectural Kashiwa-no-ha Park

To evaluate the efficacy of decontamination methods with the measurement of 1cm dose equivalent rate and concentration of radioactive caesium in the soil and plants before and after decontamination at Bouken-no-toride located in Chiba Prefectural Kashiwa-no-ha Park, five decontamination methods were examined. 1) Coverage of ground with uncontaminated soil to thickness of 5cm. 2) The topsoil was stripped and removed to the depth of 5cm. 3) Replacement with uncontaminated sand 10 - 20cm depth in sandbox. 4) Lawns were mowed at 2cm length. 5) The interchanging of 10cm of the topsoil with the underlying 20cm of subsoil. The observed 1cm dose equivalent dose reduction rate were 57%, 64%, 74%, 31% and 85% (refer to the decontamination model project article published by JAEA), respectively. (author)