平面除染による空間放射線量率の評価; 公園における除染試験結果

Effects of ground surface decontamination on the air radiation dose rate; Results of a decontamination trial at a playground lot in a Fukushima residential area

田川 明広 

Tagawa, Akihiro

原子力機構は、福島県の生活圏における学校, 公園, 家屋の除染を実施している。150平米の公園について一般の方が購入できるツールを用いて除染試験を実施した。公園では、ブランコや滑り台の遊具、土壌表土の剥ぎ取り、7MPaのストレートノズルによる高圧水洗浄による側溝除染を実施し、それぞれの除染効果を確認した。また、表土除去した土は、ピットを公園内に設け、その中に保管し覆土を実施した。その結果、1m高さの空間線量率が1.5Sv/hrであった公園の空間線量率は0.6Sv/hrにまで低減することができた。

The Japan Atomic Energy Agency decontaminated schools, playgrounds, swimming pools, and houses in non-evacuated, less-contaminated areas in Fukushima for the environmental restoration. A small, 150 m playground lot in the residential area was chosen for the decontamination demonstration, which used routinely available tools and commodities to carry out the work. The surfaces of playground lot equipment such as swings, slides, and horizontal iron bars were completely decontaminated by brushing with water and/or detergent. Side gutters around the playground lot were cleaned up by removing mud, then they were brushed and washed with a high-pressure water jet 7 MPa. The air dose rate at the playground lot was dominated by radiation from the ground surface and from adjacent surroundings such as apartments and rice fields. Two or three centimeters of the surface soil contaminated with cesium were removed manually with shovels, hoes and other gardening tools. This resulted in a significant decrease in the average air dose rate of the entire playground lot from 1.5 Sv/hr before decontamination to 0.6 Sv/hr. These results showed that ground surface decontamination can contribute measurably to a reduction in the air dose rate in relatively small areas in residential areas.