The Environment Ministry has drafted a plan to bury the ash of incinerated radioactive debris and sludge that is contaminated with more than 8,000 becquerels of radioactive cesium per kilogram in a carefully regulated manner to prevent leakage in final disposal sites.
The ministry submitted the draft plan to the Disaster-Related Waste Safety Assessment Committee, its advisory body, on Wednesday. The ministry will officially decide its policy on how to bury the radioactive ash by the end of August at the earliest.
In June, the ministry announced it would allow ash with radioactive cesium levels measuring less than 8,000 becquerels per kilogram to be buried. At that time, the ministry advised that ash exceeding that amount be temporarily stored.
Regarding how to bury ash exceeding 8,000 becquerels, the draft plan released on Wednesday said it is necessary to ensure that the contaminated ash would not mix with rainwater or groundwater.
The draft plan has suggested several possibilities, such as using disposal sites with roofs to shield the ash from rain water, a drainage treatment system to prevent underground water from being contaminated, placing the ash in highly durable containers or solidifying ash with cement.
For ash contaminated with more than 100,000 becquerels per kilogram, the draft urged that isolated disposal sites similar to those used for toxic heavy metals be used.
The ministry did not expect that ash with more than 8,000 becquerels per kilogram would be detected outside of Fukushima Prefecture.
However, since late June, ash with more than 8,000 becquerels of radioactive cesium per kilogram was found in incineration facilities in Tokyo, Chiba and other prefectures.