We present post-irradiation examination results on two type of annular mixed oxide fuel pins irradiated in the Fast Flux Test Facility (FFTF) sodium cooled reactor to an average burnup between 4% and 5% fission of initial heavy atom (FIMA). The pins differed only from the initial Pu content, which was 22 wt% and 26 wt%, respectively. The overall performance of the pins was excellent, in line with previous historical results. The pins with higher Pu content experienced higher irradiation temperatures which influenced the fission gas release, fuel swelling, and Cs distribution compared to the other pins. All the post-irradiation examinations results are discussed against the irradiation parameters. In particular, the pins with higher initial Pu content, i.e., 26 wt %, experienced higher power that resulted in enhanced fission gas release compared to the other two pins with 22 wt% initial Pu content. For the pins with higher fission gas release, onset of Cs redistribution was observed. The two pins that had lower initial Pu content and burnup showed a Cs axial distribution similar to the as-produced one.

我们介绍了在快速通量测试设施（FFTF）钠冷反应堆中辐照到初始重原子（FIMA）的4％至5％裂变之间平均燃耗的两种环形混合氧化物燃料销的辐照后检查结果。销钉仅与初始Pu含量不同，其分别为22wt％和26wt％。引脚的整体性能非常好，与以前的历史结果一致。与其他销钉相比，具有较高Pu含量的销钉承受的辐射温度更高，这会影响裂变气体的释放，燃料溶胀和Cs分布。针对辐照参数讨论了所有辐照后检查结果。特别地，具有较高初始Pu含量，即26wt％的销，与其他两个初始Pu含量为22 wt％的销钉相比，它具有更高的功率，从而导致裂变气体释放增加。对于具有较高裂变气体释放的销，可以观察到Cs重新分布的开始。具有较低的初始Pu含量和燃耗的两个销钉显示的Cs轴向分布与所生产的相似。