IFBA/WABA可燃毒物元件的燃耗特性分析

Analysis of Burnup Characteristic on IFBA/WABA Burnable Poison Element

针对AP1000反应堆采用的燃料元件表面涂硼毒物(IFBA)和湿式环状可燃毒物棒(WABA),分别采用蒙卡程序MCNP5和组件均匀化计算程序CASMO构建含可燃毒物的燃料组件计算模型,基于MCNP5分析了可燃毒物棒布置方式及数目对组件初始k_(inf)、局部功率分布的影响;基于CASMO分析了不同类型可燃毒物组件的燃耗特性。结果表明:在燃料表面涂硼作为可燃毒物具有良好的燃耗跟踪特性,燃耗寿期内k_(inf)变化较小且几乎没有残留;同时将含IFBA毒物燃料元件交叉布置可获得较小的组件初始k_(inf)值,并能更好地展平组件局部功率分布,但随IFBA涂层变厚,组件k_(inf)的变化率逐渐变小,但温度系数绝对值呈上升趋势。

In allusion to Integer fuel burnable assembly（IFBA） and Wet annular burnable assembly（WABA） used in API000 reactor,assemblies calculation of core with burnable poison were modeled in Monte Carlo Code（MCNP5） and fuel assembly burn-up program CASMO.The arrangement and number of burnable poison rods were analyzed for influence of assemblies initial k_（inf） and distribution of power density based on MCNP5.Burnup characteristics of different kinds of burnable poison assemblies were analyzed based on CASMO.The results show that：Coating with boron on fuel surface as burnable poison has good tracking burnup characteristics,Small changes with k_（inf） and almost no residual during the whole lifetime of burnup;IFBA burnable poison with across arrangement in assembly can get smaller initial k_（inf）,and it can flatten local power distribution of assemblies effectively as well.The change ratio of k_（inf） diminished along with increase of the thickness of coating,but the absolute value of temperature coefficient of assemblies shows an increasing trend.