Appropriate treatment of removed soil generated by microspot response, etc.

In Yokohama City, when a space radiation dose exceeding the standard for Motoichi is measured in the so-called "micro spots", where radiation doses are measured very locally than the surrounding area, soil is removed and doubled. After sealing in a plastic bag, it has been stored in a place where no people can enter the facility premises.
This time, the space radiation dose has been re-measured for the removed soil stored on the facility premises, and based on the measurement results, we decided to respond as follows.

As a general rule, it is backfilled on the facility premises and treated with a thickness of about 10 cm.

※The radiation dose has decreased over time and is in a safe state.However, according to the “Municipal Decontamination Implementation Guidelines” (Nuclear Emergency Response Headquarters), by covering the soil with a thickness of about 10 cm, The effect of shielding the radiation dose by 74% is obtained.

After putting it in a plastic container etc. so that water does not enter, in principle, store it underground on the facility premises with a soil covering of 30 cm or more. In addition, mark it so that you can see the buried place and clearly indicate that it is stored.

※According to the “Municipal Decontamination Implementation Guidelines” (Nuclear Emergency Response Headquarters), covering the soil with a thickness of 30 cm can have the effect of blocking the radiation dose by 98%, so the impact on the ground will be extremely small.

(1)In any case, measure the spatial radiation dose at the place covered by the soil, and confirm that it is safe as the surrounding measured values.

In addition, if a situation that does not correspond to these occurs, the Radiation Control Headquarters will consider the response.

[Reference 1]

[Reference 2]
This policy is based on the decontamination-related guidelines (May 2013 (Supplemented in March 2018): 2nd edition) (PDF: 12,637KB) (Ministry of the Environment) "Guidelines for Storage of Removed Soil". I am.
[Reference 3]
Guidelines for decontamination by municipalities (PDF: 566KB) (Nuclear Emergency Response Headquarters)

About treatment of removed soil generated by microspot correspondence, Motoichi established method of safe burial processing in reference to national guidelines. However, with regard to the removed soil stored in schools and nursery schools, the following operation methods have been added so that parents can be able to respond flexibly with consideration for the security of parents.

As a general rule, the above “processing policy” (1) will be handled, but depending on the situation of the facility, etc., the burial method will be devised, such as burying deeper, burying in a container, and taking measures to prevent digging. In addition, if these measures are difficult, the same handling as (2) below can be performed.

For the time being, we will continue to store in places where children do not approach the facility premises as before. When storing, ensure that long-term storage can be withstanded, and regularly measure the space radiation dose to confirm that it is safe as the surrounding measured values.