Development of a mixed oxide fuel pin performance analysis code "CEDAR"; Models and analyses of fuel pin irradiation behavior

Uwaba, Tomoyuki ; Mizuno, Tomoyasu; Nemoto, Junichi*; Ishitani, Ikuo*; Ito, Masahiro*

A deterministic computer code CEDAR has been developed to analyze irradiation behaviors of a mixed-oxide fuel pellet pin in a FBR. The FEM was incorporated into the mechanical calculation part of the code for properly analyzing stress-strain status in the fuel pellet and cladding, and mechanical interaction between the fuel pellet and cladding. The code features mechanistic analyses of irradiation behaviors of a fuel pin by integrating a lot of models to analyze major irradiation phenomena, thus expressing actual fuel pin irradiation behaviors. Analysis capabilities of the code were validated by calculations of fuel pellet temperatures, fractional fission gas releases of fuel pins and fuel pin cladding diametral strain profiles. The mechanisms of the fuel pin irradiation behaviors such as redistribution of Americium, PCMI and JOG formation were interpreted from the code analyses for the actual irradiation test fuel pins.