Mud at the bottom of a dam lake near the crippled Fukushima No. 1 nuclear plant is heavily contaminated with radioactive cesium, government research has shown.
Tsukuba University professor Yuichi Onda, commissioned by the Ministry of Education, Culture, Sports, Science and Technology to conduct the survey, released the findings at a symposium on March 13.
Onda's team detected radioactive cesium of some 3 million becquerels per square meter at the bottom of the Horai Dam lake, about 60 kilometers west-northwest of the nuclear plant, along the Abukuma River in Nihonmatsu, Fukushima Prefecture. The level was 10 times higher than those of nearby reservoirs, and was roughly equivalent to soil contamination levels in the 20-kilometer radius exclusion zone around the Fukushima nuclear plant.
From July to August last year, Onda took samples from the 20-centimeter-deep mud on the bottom of the dam lake, dried them and compared them with mud samples from four nearby reservoirs registering contamination in the 200,000 to 400,000 becquerels per square meter range. Cesium from the crippled power station is believed to have condensed in the mud on the bottom of the Horai Dam after flowing into the river with soil and rainwater. Read More