Dose Estimation for the Reuse of Wooden Chips Contaminated by Radioactive Cesium

Wood and wooden wastes potentially contaminated by radioactive cesium released by Fukushima Daiichi Nuclear Power Plant have been reused for various purposes as wooden chips. The Ministry of the Environment indicated that the general disaster wastes including the wooden wastes were reusable with the criteria of total radioactive cesium (cesium-134 and cesium-137) concentration of 100 Bq/kg. The criteria were determined, based on the existing clearance level of concrete and metal generated at nuclear power plant and not on dose estimation for reuse of wooden chips. The purpose of this study is to confirm the validity of the criteria by the dose estimation approach. We investigated actual conditions og production and use for main five reuse purposes of wooden ships around Fukushima. On the basis of this investigation, exposure pathways and parameters for workers and public involved with the reuse of wooden chips were selected. We calculated dose for the exposure pathways and evaluated radioactive concentrations of wooden chips corresponding to dose criteria for safety reuse of radioactive materials. From the calculation result, all radioactive concentrations corresponding to the dose criteria are more than the reuse criteria of 100 Bq/kg, which ensures the validity of the criteria for the safety of present reuse of wood and wooden wastes.