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

Tagawa, Akihiro 

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.