Influence of drying temperature on the migration of cesium chloride initially dissolved in the liquid water of sugi (Cryptomeria japonica D. Don) sapwood

A method to be potentially used for radiocesium decontamination from timber harvested in Fukushima region, where fallout from the Fukushima Daiichi nuclear disaster was deposited, involves drying the timber and planing away the contaminated wood. The objective of this study was to investigate the influence of drying temperature on the migration of cesium dissolved in the liquid water of sugi (Cryptomeria japonica D. Don) sapwood during the drying process. Small specimens of sugi sapwood impregnated with aqueous cesium chloride (CsCl) solution were dried at 20 or 90 °C, and the migration of CsCl during drying was examined by means of X-ray imaging. The results of this study indicate that the drying of sugi sapwood at any temperature causes surface accumulation of dissolved cesium, which is affected by both the drying temperature and grain orientation of the surface. Statistical analysis confirmed that a high drying temperature causes greater surface accumulation of CsCl during drying. It is recommended to use higher temperatures to dry sugi sapwood when employing the drying/planing method for radiocesium decontamination from timber.