Research on Influence of Residual Pores on Thermal-Mechanical Performance of TRISO Particle in High Temperature Reactor
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摘要: 为了明确SiC层中可能出现残余气孔对三向同性燃料（TRISO）颗粒堆内性能影响，确定残余气孔的临界尺寸，本文采用多物理场耦合COMSOL软件对含有残余气孔的TRISO颗粒的堆内行为进行数值模拟，以分析TRISO颗粒裂变气体、CO释放量及内压和残余气孔尺寸对TRISO颗粒包覆层应力分布的影响。分析结果表明，在辐照后期，TRISO颗粒的CO释放比例远高于裂变气体原子，颗粒内压可达49.5 MPa。残余气孔的存在使得碳化硅（SiC）层、内致密热解碳（IPyC）层和外致密热解碳（OPyC）层应力迅速增大，尤其是SiC层，当残余气孔尺寸达到9 μm时，SiC层最大应力达600 MPa，远高于其本征强度；当残余气孔尺寸为5 μm时，SiC层的最大应力约为450 MPa，与其本征强度相当。因此，在制备过程中为保证SiC层的结构完整性， SiC层的残余气孔尺寸应小于5 μm。
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关键词:
- 三向同性燃料（TRISO）颗粒 /
- 残余气孔 /
- 应力状态 /
- 辐照变形
Abstract: In order to investigate the influence of residual pores that may appear in SiC layer on the in-pile performance of TRistructural ISOtropic (TRISO) particle, and find the critical size of residual pores, in this paper, the in-pile performance of TRISO particle with residual pores was numerically simulated by using the multi-physical field coupling COMSOL software, and the effects of fission gas, CO release, internal pressure and residual pore size on the stress distribution of TRISO particle coating were analyzed. The results show that in the later stage of irradiation, the ratio of CO release is much higher than that of fission gas atoms, and the internal pressure of the particle can reach 49.5 MPa in the later stage. The existence of residual pores makes the stress of silicon carbide (SiC), inner dense pyrolytic carbon layer (IPyC) and outer dense pyrolytic carbon layer (OPyC) increase rapidly, especially in the SiC layer. When the size of residual pore reaches 9 μm, the maximum stress of SiC layer reaches 600 MPa, which is much higher than its intrinsic strength. When the residual pore size is 5 μm, the maximum stress of SiC layer is about 450 MPa, which is equivalent to its intrinsic strength. Therefore, in order to ensure the structural integrity of SiC layer in the preparation process, the residual pore size of SiC layer should be less than 5 μm.-
Key words:
- TRISO particle /
- Residual pore /
- Stress condition /
- Irradiation deformation
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图 1 TRISO颗粒的计算模型及边界条件
Figure 1. Calculation Model and Boundary Condition of TRISO Particle
图 2 不同中子注量下裂变气体释放量和CO气体释放量以及内压变化
Figure 2. Changes of Fission Gas Release, CO Gas Production and Internal Pressure under Different Neutron Flux
图 3 间隙包覆层尺寸随中子注量变化曲线
Figure 3. Dimensional Variation of Gap and Coated Layer Size with Neutron Flux
图 4 中子注量为1.8×1026 m−2时不同残余气孔尺寸TRISO颗粒环向应力云图
Figure 4. Contour Plots for Hoop Stress of TRISO Particle with Different Residual Pore Size When the Neutron Flux Reachs 1.8×1026 m−2
图 5 有无残余气孔SiC层最大环向应力变化曲线
Figure 5. Maximum Hoop Stress Curves of SiC Layer With and Without Residual Pores
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