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固体裂变产物在快堆燃料棒中的化学形态和扩散行为。本研究从燃料燃耗的角度研究了Ba和Zr的物理化学行为，利用EPMA对高燃耗燃料样品进行了分析。(1)在高燃耗时，以BaZrO_3的化学形式析出了Ba和Zr。在低燃耗下，MOX燃料中只有BaO析出。(2)在高燃耗下观察到的Ba-Zr-O析出物的组成与O/M比有关。(3)在燃料基质中，在包壳附近观察到的BaO浓度较高。在燃料中，Zr的分布比较均匀。结果表明，Ba很容易在燃料中扩散，而Zr很难在燃料中扩散。

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.