High-Temperature Gaseous Reaction of Cesium with Siliceous Thermal Insulation: The Potential Implication to the Provenance of Enigmatic Fukushima Cesium-Bearing Material.

Here, we report an investigation of the gas-solid reaction between cesium hydroxide (CsOH) and siliceous (calcium silicate) thermal insulation at high temperature, which is postulated as the origin for the formation mechanism of cesium-bearing material emitted from the Fukushima Daiichi nuclear power plant. A developed reaction furnace consisting of two heating compartments was used to study the reaction at temperatures of 873, 973, and 1073 K. Under the influence of hydrogen-steam atmospheric conditions (H 2 /H 2 O = 0.2), the reaction between cesium hydroxide vapor and solid thermal insulation was confirmed to occur at temperatures of 973 and 1073 K with the formation of dicalcium silicate (Ca 2 SiO 4 ) and cesium aluminum silicate (CsAlSiO 4 ). Water-dissolution analyses of the reaction products have demonstrated their stability, in particular, CsAlSiO 4 . Constituent similarity of the field-observed cesium-bearing materials near the Fukushima Daiichi nuclear power plants with CsAlSiO 4 suggests for the first time that gaseous reaction between CsOH with calcium silicate thermal insulation could be one of the original formation mechanisms of the cesium-bearing materials.