Investigation of in-reactor cesium chemical behavior in TEPCO's Fukushima Daiichi Nuclear Power Station accident, 2; Experimental investigation of Cs chemisorption behavior onto stainless steel

Nakajima, Kunihisa  ; Suzuki, Eriko   ; Nishioka, Shunichiro; Osaka, Masahiko  

Information on the Cs distribution inside the reactors at Fukushima Daiichi Nuclear Power Station (1F) is important to proceed the decommissioning. For contribution to analysis of the Cs distribution, Cs chemisorption behaviors and chemical characteristics of the chemisorbed products have been investigated to establish a chemisorption model considering influences of the chemical reaction and the chemical characteristics of reaction products. As a first step, reproducibility tests were carried out to validate the existing model incorporated into sever accident analysis codes such as SAMPSON. As a result, reaction rate constants under an argon and hydrogen gas atmosphere do not increase with temperature as expected by the existing model and the chemisorbed amounts at 1000C become lower than those at 800C. On the other hand, in the case of steam-containing argon hydrogen gas atmosphere, the reaction rate constants in such a high concentration Cs gas as expected in 1F tend to become lower than those derived from the existing model. Therefore, it was found that a chemisorption model considering difference of reducing and oxidizing atmospheres and dependence of Cs concentration in gas phase was necessary.