Updating fission product chemistry database based on recent investigation in Fukushima-Daiichi Nuclear Power Station, 3; High-temperature thermochemistry of CaCO-CsOH

Rizaal, M.   ; Luu, V. N. ; Nakajima, Kunihisa  ; Miwa, Shuhei  

Thermochemistry prevailing between gaseous CsOH and concrete main chemical phase CaCO at temperatures up to 570C was investigated with various scenarios using the thermogravimetric method. The aim was to elucidate the decreasing behavior of cesium (Cs) trapping on CaCO observed in the transpiration method. A quasi-two-compartment platinum crucible was developed to realize co-measurements of both CsOH and CaCO during thermal treatment. Post-test X-ray diffraction was conducted to identify the chemical compound formed on the CaCO precursor. The early presence (timely sensitivity) of CsOH near the heated surface of CaCO was found to play a key role in the trapping (in the form of CsCO). Such a factor is crucial because, otherwise, the Ca(OH) would predominate the surface upon CaCO decomposition where leading to no reaction with CsOH.