FeCrAl和Zr-2燃料包壳在中子辐照下的热力响应模拟

Thermomechanical Response Simulation of FeCrAl and Zr-2 Fuel Claddings Under Neutron Irradiation

摘要:

选用FeCrAl合金中具有代表性的C35M合金为研究对象，建立小型燃料棒模型，基于用户材料子程序（UMAT），将C35M合金的辐照蠕变模型嵌入子程序中，通过有限元软件ABAQUS计算了其在中子辐照下的热力耦合行为。选用Zr-2合金作为对比，分析了包壳的温度场、应力场、位移场以及间隙距离随时间的演变。结果表明，2种合金的温度场、应力场分布相同，温度分布主要受冷却剂影响，应力场则与温度、蠕变速率有关。在运行过程中，Zr-2合金以辐照生长为主，C35M合金则为辐照蠕变以及少量的热膨胀变形。Zr-2合金的间隙闭合速率远大于C35M合金，这表明C35M合金可以延长事故反应时间，但为了适应反应堆内的复杂环境，材料仍需继续优化，提高其强度以及蠕变速率。

Abstract:

The representative C35M alloy among FeCrAl alloys was selected as the research object, and a small fuel rod model was established. Based on the user material (UMAT) subroutine, the radiation creep model of the C35M alloy was embedded in the subroutine. The thermomechanical coupling behavior of C35M alloy under neutron irradiation was calculated by the finite element software ABAQUS. Using Zr-2 alloy as a comparison, the evolution of the distribution of the temperature field, stress field, displacement field, and gap distance of the cladding over time of the alloys was analyzed. Results show that the temperature field and the stress field of the two alloys are basically the same. The temperature distribution is mainly affected by the coolant, while the stress field is related to the temperature and creep rate. During the simulation, the Zr-2 alloy mainly grows through irradiation, while C35M alloy shows the irradiation creep and has a little thermal expansion deformation. The gap closure rate of Zr-2 alloy is much faster than that of C35M alloy, which indicates that C35M alloy can prolong the accident response time. However, in order to adapt to the complex environment in the reactor, the material still needs to be optimized to improve its strength and creep rate.