Setagaya Ward officials said Thursday night that an extremely high level of radiation has been detected in bottles kept in a box beneath the floorboards of an unoccupied house in Setagaya, and that this is most likely the source of radiation detected on a nearby street on Wednesday.
Researchers found radiation levels of 3.35 microsieverts per hour in tree leaves at a height of one meter by the fence of the unoccupied house along the street in Tsurumaki — much higher than previously reported levels. Initially, officials thought that the radiation may have come from the crippled Fukushima Daiichi nuclear power plant which is 220 kilometers away.
According to NHK, officials now believe that the radiation emanated from the contents of the bottles, believed to be radium, and not the nuclear power plant. No cesium was detected in the bottles. Cesium is one of the main isotopes that leaked from the Fukushima nuclear plant.
Setagaya Mayor Nobuto Hosaka told a news conference the ward obtained the owner’s consent and entered the house to measure radiation levels. The search uncovered four old and dirty bottles in a mud-covered box underneath the floorboards. The radiation level in the bottles exceeded 30 microsieverts per hour.
Hosaka said that experts from the science ministry’s nuclear safety department placed the bottles in a lead container. On Friday, ward officials will begin to decontaminate the house but said they are not sure yet how to decontaminate the street.