Study on cesium compound formation by chemical interaction of CsOH and concrete at elevated temperatures

Luu, V. N. ; Nakajima, Kunihisa  

Recently, extremely high dose rates were detected in the three-layer concrete plugs of Units 2 and 3 at the Fukushima Daiichi Nuclear Power Plant. The high dose rates suggest that there are some trapping effects of radioactive materials on shield plugs when gas species and aerosols (e.g., CsOH, CsI) are released from reactor through the plug layers. To determine the trapping mechanism, concrete and commonly used aggregate and minerals are pulverized and mixed with CsOH, followed by heating at different temperatures to clarify the chemical interaction. The results showed that interactions of CsOH and CaCO in concrete occurred even at room temperature to form CsCO(HO). The interaction with aggregates occurred above 100C and resulted in the formation of CsAlSiO. Additionally, amorphous and crystalline SiO interacted with CsOH, forming a glass-like product above 200C. These results suggest that formation of CsCO(HO) would be one of the main trapping mechanism at shield plugs because CaCO is commonly formed on concrete surface and reacts with CsOH at room temperature.