Ag-In-Cd芯体辐照后化学成分的计算

Ag-In-Cd芯体的辐照肿胀规律是评价控制棒堆内运行安全性的基础。辐照后Ag-In-Cd芯体的成分变化是引起肿胀的主要物理原因,但目前尚未看到定量计算成分变化的研究报道。本文根据Ag-InCd芯体中各核素的嬗变反应方式和反应截面,建立描述芯体成分变化的微分方程组,编写该微分方程组的数值计算程序,计算预测芯体成分随热中子注量的变化规律。当热中子注量为1.5×1021~6.2×1021 cm-2时,芯体中各元素的含量与热中子注量之间呈较好的线性关系,而芯体表层Sn和Cd的含量会达到中心含量的2倍以上。

Calculation of Chemical Composition of Ag-In-Cd Alloy after Irradiation

Ag-In-Cd control rods are widely used in PWR nuclear power plants. The irradiation swelling behavior of Ag-In-Cd alloy is very important to the safety assessment of control rod during its operation, and the change of composition is the primary cause for the swelling. The relationship between the alloy composition and thermo neutron fluence was seldom reported up to today. In this work, a group of differential equations was proposed to describe the composition of Ag-In-Cd alloy during irradiation based on the transmutation reactions and the reaction cross sections. A numeric resolution to the equations was established. The alloy compositions at different thermo-neutron fluences were calculated and a group of formula for composition prediction was obtained. The average content for each element is approximately a linear function of thermo neutron fluence, and the content of Cd and Sn in the surface layer will be higher than two times of that in the center.