Development of mechanical property analysis program for space thermionic fuel element
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摘要: 为了实现对空间热离子反应堆燃料元件运行期间安全性能的预测，研究开发了一种燃料元件力学性能分析程序，并针对多层圆筒状的TOPAZ-Ⅱ热离子燃料元件开展了应力、应变和几何变形的高精度模拟。程序考虑了核燃料在高温辐照环境下的辐照肿胀，并分析了燃料芯块-发射极在发生接触后的力学响应问题，从而快速且准确地求解燃料芯块和发射极的力学状态，以对空间热离子反应堆运行期间的性能提供准确预测。结果表明：在正常运行情况下，空间热离子反应堆燃料会发生显著的肿胀效应，其造成的变形将导致燃料元件热电转换效率降低、元件失效等安全隐患。Abstract: To predict the safety performance of fuel elements during operation of a space thermionic reactor, this study developed a mechanical performance analysis program for fuel elements, and conducted high-precision simulation of stress, strain, and geometric deformation for the multi-layer cylindrical TOPAZ-II thermionic fuel element. The program takes into account the irradiation swelling of nuclear fuel under high-temperature radiation environment, and analyzes the mechanical response of the fuel pellet-emitter after contact, thereby quickly and accurately solving the mechanical state of the fuel pellet and emitter, to provide accurate prediction of the performance during operation of the space thermionic reactor. The results indicate that in normal operating conditions, the fuel of a space thermionic reactor undergoes significant swelling effects, which causes deformation that can lead to potential safety hazards such as reduced thermal-electric conversion efficiency and component failure.
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Key words:
- space reactor /
- fuel element /
- irradiation swelling /
- mechanical analysis
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图 4 晶粒内气态膨胀的实验-模拟对比
Figure 4. Experimental-simulation comparison of intra-granular gaseous swelling
图 5 晶粒间气态膨胀的实验-模拟对比
Figure 5. Experimental-simulation comparison of inter-granular gaseous swelling
图 8 燃料元件径向尺寸随运行时间的变化
Figure 8. Variation of fuel elements radial size with operation time
图 12 发生接触后接触应力和燃料芯块的外表面移动速率
Figure 12. Contact pressure and outer surface movement rate of fuel pellet after contact
图 13 接触后发射极等效应力随时间的变化
Figure 13. Variation of equivalent stress of emitter with operation time after contact
表 1 模型相关系数
Table 1. Constants of the model
${K_1}/{{\text{K}}^{-{{1}}}}$ ${K_2}$ ${K_3}$ ${E_D}{\text{/J}}$ $9.80 \times {10^{ - 6}}$ $2.61 \times {10^{ - 3}}$ $3.16 \times {10^{ - 1}}$ $1.32 \times {10^{ - 19}}$ 
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表 2 算例的主要参数
Table 2. Main parameters of the case
elastic
modulus/GPaPoisson’s
ratioouter diameter of
cylinder/mminner diameter of
cylinder/mmexternal surface
pressure/MPainternal surface
pressure/MPa197 0.3 6 5.4 0.101 0.028
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