An experimental investigation of influencing chemical factors onCs-chemisorption behavior onto stainless steel

Abstract

ABSTRACT A more accurate cesium hydroxide (CsOH)-chemisorption model is required to improve the estimation of the Cs distribution in Fukushima Daiichi Nuclear Power Station by severe-accident (SA) analysis codes. The current CsOH-chemisorption model incorporated in SA analysis codes was developed with insufficient information of chemical factors such as H2/H2O ratio, concentration of chemically affecting elements, heating time, and surface condition of the stainless steel (SS). Therefore, we have conducted experimental tests for CsOH-chemisorption onto SS type-304 (SS304) in order to examine the effect and dependence of such chemical factors on the CsOH-chemisorption behavior in detail. It was found that the first-order surface-reaction rate constant was influenced by not only temperature, as already known, but also H2/H2O ratio, CsOH concentration in the gas phase, and silicon content in SS304. Such chemical factors should be considered for the construction of the improved CsOH-chemisorption model. Another important finding is that the chemisorption behavior at lower temperatures, around 873 K, could differ from those above 1073 K. Namely, Cs–Fe–O compounds would form as the main chemisorbed Cs compounds at 873 K while Cs–Si–Fe–O compounds at more than 1073 K.