Study on chemical form and diffusion behavior of solid fission products in FBR fuels

从反应堆安全的角度研究了快堆燃料棒中固体裂变产物的化学形态和扩散行为。本文从燃料燃耗的角度研究了Ba和Zr的物理化学行为，并利用电子探针对高燃耗燃料样品进行了PIE分析。(1)在高燃耗下，Ba和Zr均以BaZrO_3的形式析出。在低燃耗时，在混合氧化物燃料中只观察到BaO沉淀物。(2)在高燃耗下观察到的Ba-Zr-O沉淀的组成取决于O/M比。(3)在燃料基质中观察到的Ba浓度在包壳附近较高。Zr在燃料中分布均匀。结果表明，Ba易于在燃料中扩散，而Zr几乎不能在燃料中扩散。

Chemical form and diffusion behavior of solid fission products in FBR fuel rods were studied from aspect of reactor safety. In this study, physico-chemical behaviors of Ba and Zr were researched in terms of fuel burn-up.Using EPMA, specimens from high burn-up fuels were analyzed in PIE.(1) Both Ba and Zr were precipitated as the chemical form of BaZrO_3 at high burn-up. At low burn-up, only BaO precipitates were observed in MOX fuels.(2) The composition of Ba-Zr-O precipitated observed at high burn-up was dependent on O/M ratio.(3) The concentration of Ba observed at fuel matrix was high near the cladding. That of Zr was uniformly distributed in fuels. As the result, it was clear that Ba easily diffused in fuel and that Zr could hardly diffuse in it.