Leaching behavior of multiphase solidified melt prepared from stainless steel and Zircaloy

Ikeuchi, Hirotomo  

Formation of metallic fuel debris is highly probable in the damaged core of the Fukushima Daiichi Nuclear Power Station. Estimating the number of radionuclides released from the fuel debris to an aqueous solution is indispensable for proper handling of fuel debris and waste management. In the present study, a simple approach is introduced to roughly evaluate the mass of elements leached from complex multiphase surfaces considering the surface-area-weighted-average of the contributions of individual phases. Static leaching tests were performed under the acidic and the alkaline conditions to investigate the gap between the simplified assumption and the actual dissolution behavior. Alloy samples of a stainless steel-Zircaloy (SUS-Zry) solidified melt and two single-phase samples (Fe,Cr)Zr- and Zr(Fe,Ni)-type phases, which comprised the surface of the SUS-Zry alloy) were used in the static leaching tests. The masses of the Fe, Cr, Ni, and Zr leached from the SUS-Zry alloy fitted with those evaluated by the surface-area-weighted approach by 1 to 2 orders of magnitude of precision.