球床高温气冷堆燃料颗粒中放射性核素的累积释放份额研究

Study on cumulative fractional release of radionuclides in HTGR fuel particles

本文利用Fick扩散定律,给出经典方法和改进的两种累积释放份额的严格数学表达式,并分析与之相关的穿透时间的物理内涵,并分别用以上两种方法计算137Cs,90Sr,110mAg三种重要放射性核素通过SiC层扩散的累积释放份额.研究表明,传统的"穿透时间"概念并非放射性核素释放到SiC层外的时间,本文提出的改进方法可以更准确的描述放射性核素在燃料元件中的输运和扩散行为.

During high-temperature gas refrigeration reactor （HTGR） operation, SiC in the fuel particles is the key structure for stopping radionuclides diffusing from the particles. Researchers put forward the concept of breakthrough time, which is the time of a large amount of radionuclides released through SiC from the particles, for the consideration of HTGR safety. However, this concept is not so accurate. This paper gives a strict expression of cumulative fractional release interims of classic and improved methods, and also analyses the relevant physical content of breakthrough time in the use of Fick＇s law of diffusion. By computing the cumulative fractional release of three kinds of important radiouuclides 1376s, 9~Sr and ll^mAg, and using the above two methods, we find that the traditional meaning of the physical quantity is not the time of radionuclides released from SiC. The improved method is more accurate for describing the release and transport condition of radionuclides in nuclear fuel particles.