压水核反应堆堆芯燃料棒热工数值计算与研究

发布时间：2018-02-12 07:46

本文关键词： 压水核反应堆燃料棒数值计算 (火用)分析　出处：《南京理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着核电事业的高速发展,针对先进压水核反应堆堆芯热工水力优化设计成为核电领域的研究热点。在核反应堆热工设计中,安全性能是第一要素,必须保证任何情况下反应堆的安全运行。本文基于非结构化网格中的有限容积法,采用全隐格式离散非稳态导热方程,通过可视化语言Fortran90/95进行数值计算,分析堆芯燃料棒传热温度和(火用)损失分布规律以及不同运行工况下热安全特性。首先,对单通道模型稳态传热工况进行计算分析。通过理论推导获得核燃料棒包壳内外壁面、燃料芯块表面和中心温度场分布的解析解,并将精确解的结果与定热导率和热导率随温度变化两种情况下的数值解对比分析。两者结果吻合良好,并且后者误差更小。研究发现正常运行工况下高温区在燃料棒中心偏上,向两端逐渐减小;在芯块区和气隙区有较大温降,且气隙区温降速率最大。包壳外壁面温度均匀分布,最大温度值出现在热通道中心和出口之间。其次,以秦山二期工程压水堆为原型,讨论常见的三种事故工况下燃料棒传热和温度分布规律。当有反应性引入时,温度反馈效应可使急剧上升的温度逐渐趋于稳定,负温度系数更有利于调节堆芯功率,和确保反应堆安全运行;同时燃料棒上下壁面边界条件的改变对于温度场影响很小。当燃料芯块发生偏置时,燃料棒整体温度有所下降,高温区向芯块偏置反方向偏移;偏心率越大,偏移程度越大,并且包壳外壁面温度分布不再均匀,最大温度值也越高。当发生失流事故(LOFA)时,对流换热系数沿热通道变化幅度很小;对流换热系数越小,芯块中心和包壳温升越快。尤其在小于20 kW/(m2·℃C)时影响越大,此时包壳外壁面最高温度出现的位置越接近燃料棒中心点,但是热流密度值变化很小。最后,结合热力学第一定律和热力学第二定律,基于燃料棒温度场采用(火用)分析法计算分析反应堆内能量转换,以及热量传递过程中(火用)损失分布规律。研究结果发现,核燃料温度越高,传热温差越小,(火用)损失越小。但二者又相互制约,在总(火用)不变情况下内热源分布的改变对总(火用)损影响很小,只是改变燃料棒(火用)损失分布。该分析方法可为优化反应堆热工设计和可靠性评估提供有益参考。
[Abstract]:With the rapid development of nuclear power industry, the advanced pressurized water reactor core thermal hydraulic optimization design has become a research hotspot in the field of nuclear power. In the thermal design of nuclear reactor, safety is the first element, must ensure safe operation of the reactor under any situation. The finite volume method based on unstructured grids, by a full implicit to discretize the unsteady heat conduction equation, through the visual language Fortran90/95 numerical calculation, analysis of reactor core fuel rod heat transfer temperature and heat loss (exergy) distribution and safety characteristics under different operating conditions. Firstly, calculation and analysis of the single channel model for steady heat transfer conditions. Access to nuclear fuel rod cladding wall through theoretical derivation. The analytical solution distribution temperature of the fuel pellet surface and center, and the exact solution and the thermal conductivity and thermal conductivity change with temperature under two conditions The comparative analysis of the numerical solutions. The results are in good agreement, and the latter error is smaller. The study found that under normal operating conditions in the high temperature zone of fuel rod centre, gradually reduced to the ends of the core block; and the air gap area has a larger temperature drop, and the air gap region temperature drop rate. Maximum cladding surface temperature distribution and the maximum temperature value between the thermal channel center and export. Secondly, in the two phase of the project of Qinshan PWR as the prototype, discusses three common accident conditions of fuel rod heat transfer and temperature distribution. When the reaction temperature is introduced, the feedback effect can make a sharp rise in temperature gradually stabilized, negative temperature the coefficient is more conducive to regulating core power, and ensure the safe operation of the reactor; at the same time under the wall boundary condition on the fuel rod changes for temperature effects is very small. When the fuel pellets bias, the overall temperature under the fuel rods Drop, high temperature area to the core block bias against the direction of migration; the larger the eccentricity ratio, the greater the degree of deviation, and shell surface temperature distribution is not uniform, the maximum temperature is higher. When the loss of flow accident (LOFA), the convective heat transfer coefficient along the hot channel variation is very small; convective heat transfer the coefficient is small, the core block center and cladding temperature rise fast. Especially in less than 20 kW/ (M2 C C) when the greater the impact, the shell wall of the highest temperature is closer to the center of the fuel rods, but the heat flux changes little. Finally, according to the first law of thermodynamics and thermodynamics the second law, the fuel rod temperature field based on the calculation and analysis of energy (exergy) conversion reactor analysis method, and the heat transfer process (exergy loss distribution). The results of the study showed that nuclear fuel temperature is high, the heat transfer temperature difference is small (exergy) losses is small. But the two and restrict each other, Under the condition of total exergy invariance, the change of heat source distribution has little effect on total exergy loss, but only changes the exergy loss distribution of fuel rods. This analysis method can provide a useful reference for optimizing reactor thermal design and reliability evaluation.

【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TL329

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