Research on rare-earth element reaction processes with fuel cladding materials in FBR

Reaction tests of diffusion couple of ferritic martensitic steel (PNC-FMS), a candidate for fast reactor fuel cladding, and the rare-earth element Ce by diffusion pairing have been performed for up to 600 h. The results indicated that the reaction process is diffusion-controlled. Chemical and microstructural analyses by SEM and TEM revealed that Ce3(Fe, Cr)29 was formed in the early stage of the reaction, which was subsequently converted into CeFe2. The reaction phase changed depending on the presence of Cr in the base metal and increasing Ce concentration, indicating a multi-reaction process.