ASME规范概率评价方法对细颗粒石墨的适用性研究

Study on Application of Probabilistic Method in ASME Standard on Fine-grained Graphite

石墨由于其高中子散射截面和低中子吸收截面特性,被广泛应用于第四代高温气冷堆中作为慢化剂、反射层和堆芯结构,故保证其结构完整性对反应堆的安全运行非常重要。由于石墨材料强度分散,概率论方法评价其失效较常用的确定论评价方法更为合适。目前,美国ASME规范采用的概率方法主要针对NBG-18这种大颗粒石墨,对我国高温气冷堆核电站工程项目采用的细颗粒石墨IG-110的适用性未知。同时,我国成都碳素生产的高温堆备选石墨NG-CT-01颗粒大小与IG-110相似,也为细颗粒石墨。因此,文章研究ASME规范概率方法对细颗粒石墨的适用性,并通过实验数据加以验证。结果表明,对于细颗粒石墨,ASME规范过于保守,低估了材料的强度性能。

Graphite has high neutron scattering cross section and low thermal neutron absorption cross section. Therefore, graphite is widely used in HTR as moderator, reflector and core structure material. In the design of HTR, it is important to guarantee the structural integrity of graphite components. Because of the variability of material strength, probabilistic approach is well suited for nuclear graphite. However, the prob-abilistic method adopted by ASME code focuses on coarse-grained graphite such as NBG-18 and its application on fine-grained graphite like IG-110 remains unknown. In the present paper, the probabilistic method of ASME was introduced and its application on fine-grained graphite was verified with different tests. The results indicate that the aforementioned method will lead to very conservative failure probability for fine-grained graphite.