Np-237在AP1000首循环堆芯中的嬗变研究

Transmutation of Np-237 in the First Cycle of AP1000 Core

摘要: 核电站所产生的乏燃料中含有大量的放射性核素，主要包括长寿命裂变产物(LLFP)和少量锕系元素(MA)，这些核素要通过上万年的衰变才能消除放射性危害。分离嬗变技术(P&T)是将这些放射性核素从乏燃料中分离出来，放入特定装置中，对其进行中子照射，使其转变成低放射性核素或稳定核素。镎(Np)作为一种最主要的MA核素，其含量高，半衰期长。本文利用MCNP程序搭建AP1000反应堆堆芯模型，以二氧化镎(NpO₂)嬗变棒为引入方式，设计出在首循环堆芯中添加嬗变材料的10种方案。通过计算比较各种方案中有效增殖因子(ke_ff)、二氧化镎的添加质量和使堆芯重新达到临界所需要改变堆芯的程度，结果显示在堆芯燃料富集度为4.45%区域添加二氧化镎涂层的方案具有优势，本文对该方案进行了分析并进行了优化。

Abstract: The spent fuel generated by nuclear power plants contains large quantities of radionuclides, in-cluding long-lived fission products (LLFP) and minor actinides (MA). These nuclides decay to no harm through thousands of years. Partitioning and transmutation technology (P&T) is to separate these nuclides from the spent fuel into specific device for neutron irradiation, making it into a low-level radioactive nuclides or stable nuclides. As a major MA nuclide, neptunium (Np) has a high productivity and long half-time. In this paper, MCNP code is used to build the AP1000 reactor core model, and neptunium dioxide (NpO₂) transmutation rod is introduced to design 10 schemes where transmutation material is putted into the first cycle core. By calculation and comparing the effective multiplication factor (ke_ff), the added quality of neptunium dioxide and the changing extent to make the core reach the critical again, the result shows that the scheme where neptunium dioxide coating is putted in the fuel enrichment 4.45% of the core has advantages. This paper analyzes the scheme and optimized.