Dose estimate for the reuse of wooden chips

Takai, Shizuka ; Seki, Masaya; Kimura, Hideo; Takeda, Seiji 

Wood (thinned wood from forest etc.) and wooden wastes (demolished wood etc.) potentially contaminated by radioactive cesium released by Fukushima Daiichi Nuclear Power Plant have been used for various purposes as wooden chips. However, there has been no dose estimation for use of such contaminated wood so far. Up to now, use of wood has been conducted according to a standard value of 100 Bq/kg for radioactive cesium based on clearance level of concrete and metal generated at nuclear power plant. The purpose of this study is to evaluate the safety of present use of wood by dose estimation for reuse of contaminated wooden chips, which are reused for main five use purposes (particle board, paper, compost, biomass power fuel, mulching). We also calculated activity concentrations of radioactive cesium in wooden chips corresponding to standard dose for safety reuse of radioactive wastes and regarded the minimum calculated activity concentration as a standard value of activity concentration for each reuse purposes. From the result, the minimum standard value of activity concentration of radioactive cesium in wooden chips for all reuse purposes is estimated to be 120 Bq/kg for reuse of wooden chips for particle board. Since this standard value is more than 100 Bq/kg, the safety of present use of wood is confirmed.