Ash from wood-burning stoves in Miyagi Prefecture has been found to contain alarmingly high levels of radioactive cesium.
Ash from wood-burning stoves in Miyagi Prefecture has been found to contain alarmingly high levels of radioactive cesium.
Up to 59,000 becquerels of cesium per kilogram has been detected in samples from the northeastern prefecture, the Environment Ministry said Feb. 10.
In late January, the ministry inspected logs and ash collected from private households in nine municipalities in the south of Miyagi Prefecture, close to the border with Fukushima Prefecture, site of the crippled Fukushima No. 1 nuclear power plant.
The radioactive content in the ash ranged from 1,180 becquerels per kilogram in a sample from Kakuda to 59,000 becquerels per kilogram in a sample from Marumori.
A log from Marumori came from a local forest and had been stored outdoors, ministry officials said.
The maximum level of 59,000 becquerels per kilogram is more than seven times higher than the Environment Ministry's safety standard of 8,000 becquerels or less per kilogram for authorizing landfill along with other types of waste.
Radioactive substances in wood condense rapidly during incineration. That likely explains the high cesium content, sources said.
Earlier, on Jan. 19, the Environment Ministry said that up to 43,780 becquerels of radioactive cesium was detected per kilogram of ash from logs collected in November at a yard in a private home in Nihonmatsu, Fukushima Prefecture. The ministry then issued a notice calling on residents and local governments to store ash in plastic bags instead of scattering it in yards and farmland. The ministry also said that ash should be collected and inspected by the municipal governments.
The ash can be used in landfill if they contain 8,000 becquerels or less of radioactive cesium per kilogram. However, disposal should be entrusted to the central government if the concentration exceeds 8,000 becquerels per kilogram.