Local measurement results of air radiation dose at municipal elementary and junior high schools (updated on October 19, 2020)

　The measurement results to date have been stable and are below the Ministry of the Environment's standard value (0.23 microsieverts per hour). Measurement of quantity has been suspended since 2017.
In addition, measurements of rainwater basins, etc. at Shiroyama Elementary School and Inagi Daigo Junior High School were carried out once a year (August), but since 2021, the values ​​have been stable and within standard values. In Tokyo, the radiation monitoring post in Shinjuku Ward, which had been set up before the Great East Japan Earthquake, has dropped to pre-earthquake levels. Measurement will be suspended. However, if any concerns arise, measurements will be resumed immediately.

【explanation】
The annual equivalent of 0.23 microsieverts per hour is 0.99864 millisieverts, which is an indicator of the normal radiation dose received by the general public (less than 1 millisievert per year (natural radiation dose, etc.), as recommended by the International Commission on Radiological Protection (ICRP). )), this value is the city's criterion value .
According to the Ministry of the Environment's "Decontamination-related Guidelines," no further action will be taken if the radiation level at 1 meter of the ground surface is below 0.23 microsieverts per hour, but the city is on the safer side. , decisions are made based on measurement results at the location closest to the target location (1 centimeter above the ground).

Measurer

City staff

measuring equipment

PA-1000

Measuring method

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

Inagi City Shiroyama Elementary School

Measurements at the rainwater catch basin on the school grounds showed a reading of over 0.23 microsieverts per hour, so work was carried out to reduce radiation levels by cleaning. The soil that had accumulated in the rainwater catch basin was removed, placed in a sandbag, and then covered with two plastic bags to seal it. A 50-centimeter deep hole was then dug outside the baseball fence on the north side of the school grounds, where the soil was buried and then covered with soil.
After cleaning, the radiation level in the rainwater manhole was found to be below the standard level, and it was confirmed that the radiation level outside the baseball fence on the north side of the schoolyard, where soil had been buried, was also below the standard level (see "Past Measurement Results" for numerical values).

Inagi City Inagi Daigo Junior High School

(1) As a result of measurements taken under the rain gutters in the gymnasium, the readings were over 0.23 microsieverts per hour, so work was carried out to reduce radiation levels through cleaning. Remove the soil from the gutter under the rain gutter for 1.5 meters in front and back of the rain gutter, put the removed soil in a sandbag, cover it twice with a plastic bag, seal it, and dig a hole 70 cm deep to the southwest of the gymnasium. After digging and burying it, we covered it with soil. It was confirmed that the radiation level under the rain gutter after cleaning was below the standard value, and that the radiation level in the southwest part of the gymnasium, where the soil was buried, was also below the standard value (see "Past measurement results" for numbers).

(2) As a result of measurements taken under the rain gutters of the school building, the readings were over 0.23 microsieverts per hour, so work was carried out to reduce the radiation dose through cleaning. The soil from the gutters under the rain gutters was removed, the removed soil was placed in sandbags, and a plastic bag was placed over the top to seal it, and a hole 70 centimeters deep was dug to the southwest of the gymnasium and buried. We covered the soil. We also used a high-pressure washer to clean the walls near the rain gutter, the asphalt below the gutter, and the inside of the gutter. It was confirmed that the radiation level under the rain gutter after cleaning was below the standard value, and that the radiation level in the southwest part of the gymnasium, where the soil was buried, was also below the standard value (see "Past measurement results" for numbers).

Regular measurements are taken at locations where cleaning has been carried out to monitor progress. The results of follow-up measurements 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)