2014 Volume 63 Issue 1 Pages 45-55
The efficacy of decontamination methods was evaluated with the measurement of 1cm dose equivalent rate and concentration of radioactive caesium in the soil, plants and water of the pond before and after decontamination at Japanese garden located in Chiba Prefectural Kashiwa-no-ha Park. Examined decontamination methods were:1)The topsoil of walkway was stripped and removed to the depth of 10mm. 2)Washing the stone pavement walkway using high-pressure water jet washer. At the height of 50cm, we observed 45% and 36% of 1cm dose rate equivalent dose reduction rate(the natural dose rate derived from the ground was subtracted) for 1) and 2) decontamination methods respectively. Due to the decontamination process, the measurement value of 1cm equivalent dose rate decreased below 0.23μSv/h at most of the examined sites, which showed significant efficacy of decontamination methods performed at this Japanese garden.