Study of KRUSTY Thermal Expansion Negative Feedback Calculation Based on Unstructured-Mesh MCNP
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摘要: 热管堆KRUSTY的热膨胀负反馈模拟一直是业内计算的难点。本文基于蒙特卡罗方法（MCNP）的非结构网格功能，将KRUSTY非结构网格的功率分布直接输入给有限元软件ABAQUS，利用ABAQUS进行KRUSTY的热力耦合，在统一的非结构网格下研究了KRUSTY热变形模拟、膨胀反应性反馈和密度反馈，重点研究了非均匀密度与均匀密度的差异。结果表明，热膨胀效应带来超过900pcm（pcm=10−5）的负反馈，特殊的燃料变形主要发生在上部和外边缘表面，总位移达到~0.9 cm，反应堆堆芯总温差足够小，只有23 K 左右，并且核热力耦合较核热耦合趋于使堆芯的温度分布更均匀，由于热管的冗余设计，反应堆的设计可以满足单点失效原则。相较于传统的组合实体（CSG）几何，本文基于非结构网格MCNP方法可以更真实地模拟金属燃料堆的热膨胀效应。Abstract: Thermal expansion negative feedback simulation of heat pipe reactor KRUSTY has always been a difficulty in calculation. Based on the unstructured mesh ablility of MCNP, the power distribution of KRUSTY unstructured mesh is directly input to ABAQUS, and the thermal mechanical coupling of KRUSTY is carried out by ABAQUS. The thermal deformation simulation, expansion reactivity feedback and density feedback of KRUSTY are studied under the unified unstructured mesh. The difference between non-uniform density and uniform density is studied. The results show that the thermal expansion effect brings more than 900pcm (pcm=10-5) negative feedback, and the special fuel deformation mainly occurs on the upper and outer edge surface, with a total displacement of about 0.9 cm. The total temperature difference of reactor core is small enough, only about 23 K. Moreover, the neutronics-thermo-mechanics coupling tends to make the core temperature distribution more uniform, and the reactor design can satisfy the single-point failure principle due to the redundant design of the heat pipe. Compared with the traditional CSG geometry, the unstructured-mesh Monte Carlo method can better simulate the thermal expansion effect of metal fuel reactor.
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Key words:
- KRUSTY /
- MCNP /
- Unstructured mesh /
- Neutronics-thermo-mechanics coupling /
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图 2 KRUSTY 的稳态热膨胀负反馈计算流程
Figure 2. Steady-state Thermal Expansion Negative Feedback Calculation Flow of KRUSTY
图 5 归一化的燃料温度、位移和应变压强分布
Figure 5. Normalized Fuel Temperature, Displacement and Strain Pressure Distribution
图 6 不同径向面的燃料位移分布
Figure 6. Fuel Displacement Distribution on Different Radial Surfaces
图 7 热膨胀后非均匀密度情况下燃料密度分布
Figure 7. Distribution of Fuel Density after Thermal Expansion under Non-uniform Density
图 8 核热力耦合与核热耦合下温度对比分布
Figure 8. Temperature Difference Distribution under N-T-M Coupling and N-T Coupling
图 9 单根热管失效下的温度分布和与失效前温度的差异
Figure 9. Temperature Distribution under Single Heat Pipe Failure and Temperature Difference after the Failure
图 10 单根热管失效下的位移和应变压强分布
Figure 10. Displacement and Strain Pressure Distribution under Failure of a Single Heat Pipe
表 1 KRUSTY U-Mo核燃料的热物性参数
Table 1. Thermal and Physical Parameters of KRUSTY U-Mo Fuel
参数 参数值 密度（ρ）/( g·cm−3) 17.34 (300 K) 杨氏模量（E）/ Pa 8.8×1010 泊松比（υ） 0.35 热传导系数（k）/
[ W·(cm·℃)−1]0.12~0.37
(300~1200 K)热膨胀系数（α）/(K−1) 2.0895×10−5 
下载: 导出CSV
表 2 UM几何网格与CSG几何下冷态临界keff的对比
Table 2. Comparison of Cold Critical keff between Unstructured Mesh and CSG Geometry
输入方式 径向网格
尺寸/cm单元数 时间/
minkeff 与CSG
偏差/pcmUM 均匀密度 0.4 15750 795 1.02450 267 0.2 58625 1455 1.02257 74 非均匀密度 0.4 15750 6544 1.02459 276 0.2 58625 22643 1.02243 60 CSG几何 437 1.02183
下载: 导出CSV
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