2012 年 47 巻 4 号 p. 247-259
Dehydrated sludge generated through sewage and water supply processing has been contaminated by radioactive cesium after the severe accident at the Fukushima Nuclear Plant. Incineration and disposal of the dehydrated sludge should be carried out while ensuring the safety of radiation for the workers and the public. In this study, in order to provide the technical information for making the guideline on the incineration and disposal of dehydrated sludge, the dose estimate for scenarios on the incineration and disposal is conducted, based on the method used for driving the clearance levels in Japan. From the result of dose calculation, it is suggested that it is necessary to forbid reusing the disposal site as construction, resident and agriculture in which the calculated effective doses for the public are higher than those in the other exposure pathways. Minimum activity concentration of radioactive cesium in dehydrated sludge and incineration ashes, corresponding to the effective dose criterion indicated by Nuclear Safety Commission of Japan, is estimated to be 8.9 Bq/g under the condition of limited reuse of the site. In the case of the activity concentration below 8.9 Bq/g, the calculated dose of the resident due to direct and sky-shine radiation from the temporary storage place is less than 1 mSv/y, irrespective of the distance from the storage place.
