Space radiation dose local measurement result (October 19, 2020 update) of municipal elementary and junior high school

　The measurement results to date have been stable and are below the standard value (0.23 microsieverts per hour) set by the Ministry of the Environment. About the measurement of the quantity, I am suspended from 2017.
In addition, measurements of the rainwater basins at Shiroyama Elementary School and Inagi Daigo Junior High School were conducted once a year (August). In Tokyo, the radiation monitoring post in Shinjuku Ward, which had been installed since before the Great East Japan Earthquake, has decreased to the level before the earthquake. We will suspend the measurement. However, if any concerns arise, the measurement will be resumed immediately.

【explanation】
When converted from 0.23 microsieverts per hour to 0.99864 millisieverts per year, the International Commission on Radiological Protection (ICRP) recommends that the normal dose of radiation received by ordinary people (below 1 millisievert per year (natural radiation dose, etc.) (Excluding)), so this value is the city's judgment standard value .
According to the Ministry of the Environment's "Decontamination Guidelines", if the radiation dose at 1 meter of the ground is below 0.23 microsieverts per hour, no further action will be taken. , the response is determined based on the measurement results at the location closest to the target location (1 cm on the ground surface).

Measurer

city official

measuring equipment

PA-1000

Measuring method

Average of 5 repeated measurements every 60 seconds (PA-1000)

Inagi Municipal Shiroyama Elementary School

As a result of measuring in the rainwater catchment on the school grounds side, the measured value was more than 0.23 microsieverts per hour, so we carried out work to reduce the radiation dose by cleaning. Remove the soil accumulated in the rainwater basin, put the removed soil in a sandbag, cover it with a double plastic bag and seal it, then dig a 50cm deep hole outside the north fence of the schoolyard. , After filling it, we covered it with soil.
After the cleaning, the radiation dose in the rainwater catch basin was below the standard value, and it was confirmed that the radiation dose outside the ball fence on the north side of the school grounds, which was covered with soil, was also below the standard value (see "Past Measurement Results" for figures). ).

Inagi Municipal Inagi Fifth Junior High School

(1) As a result of measuring under the rain gutter of the gymnasium, the value was more than 0.23 microsieverts per hour, so we carried out work to reduce the radiation dose by cleaning. Remove the soil from the gutter under the rain gutter for 1.5 meters before and after the rain gutter, put the removed soil in a sandbag, cover it with a double plastic bag and seal it, and then make a 70-centimeter deep hole in the southwest of the gymnasium. After digging and burying it, we covered it with soil. After the cleaning, it was confirmed that the radiation level under the rain gutter was below the standard value, and that the radiation level in the southwest of the gymnasium, where soil was buried, was also below the standard value (see "Past Measurement Results" for figures).

(2) As a result of measuring under the rain gutter of the school building, the value was more than 0.23 microsieverts per hour, so we carried out work to reduce the radiation dose by cleaning. Remove the soil from the gutters under the rain gutters, put the removed soil in a container bag, cover it with a double plastic bag and seal it, then dig a 70cm deep hole in the southwest of the gymnasium and bury it. I covered it. In addition, a high-pressure washer was used to wash the walls near the rain gutters, the asphalt under the rain gutters, and the inside of the rain gutters. After the cleaning, it was confirmed that the radiation level under the rain gutter was below the standard value, and that the radiation level in the southwest of the gymnasium, where soil was buried, was also below the standard value (see "Past Measurement Results" for figures).

We regularly measure the locations where cleaning has been carried out and observe the progress. The follow-up measurement results are as follows.

[Measurement overview]
Measurer
City staff
measuring equipment
PA-1000
Measuring method
Average of 5 repeated measurements every 60 seconds (PA-1000)
measured value
Unit: microsievert per hour (1 centimeter of the earth's surface)