(iii) A method of measuring ambient dose rates

At the radiation monitoring posts set up in various areas of Fukushima Prefecture, ambient dose rate measurements are taking. This section explains how these radiation monitoring posts are measuring the ambient dose rate.

Ambient dose rate measurement

The ambient dose rate is obtained by measuring γ-ray doses in the air, and is indicated in microsieverts per hour. The measured value is not limited to the amount of radiation derived from accidents. Natural radiation mainly comes from the ground and cosmic rays.
Normally, a measuring instrument is placed at a height of about 1 m from the ground, because most important internal organs are located at this height in the case of an adult. The height of measuring instruments may be set to 50 cm from the ground in places mainly visited by children, such as schools and pre-schools.

For more information about ambient dose rates, see page 52 of Vol. 1, FY2022 edition.