Study on Micro Reactor Physics for Improvement of Neutronics Calculation

1)建立了考虑微堆物理效应的瞬态分析理论，并在此基础上编制了计算程序。由于现行的耦合碰撞概率法（CCCP）可以严格模拟燃料组件中销电池结构等非均质性，并且可以在计算有效截面时处理非均质性，因此所开发的理论采用了现行的耦合碰撞概率法（CCCP）。基于微堆物理的分析表明，中子通量的角分布受周围几何形状和成分的影响较大。因此，我们考虑了测量堆芯内中子通量角分布的技术。所设计的技术采用光纤探测器和Cd管。将该技术应用于kua c型堆芯槽内堆芯的角分布测量，结果表明该技术是测量中子通量角分布的有效方法。3)开发了中子-热力学耦合程序来评价瞬态现象中燃料棒内温度分布的影响。应用该程序对燃料棒内部温度分布的非均质性等进行了直接建模，分析了冷、热待机状态下的控制棒掉落事故。结果表明，基于微堆物理的分析对于考虑瞬态燃料棒内复杂的温度分布是必要的和有用的，而有效温度模型中燃料棒内温度分布是平坦的，由于温度分布的复杂而导致结果的杂化。

1)We have developed the theory for transient analysis with the consideration of Micro-reactor physics effect, and have developed the calculation code based on the developed theory. The current Coupling Collision probability method (CCCP method) is adopted in the developed theory because the CCCP method can strictly model the heterogeneity such as a pin cell structure in a fuel assembly and can treat the heterogeneity in calculating the effective cross sections: New CCCP method, which can treat the transient in time has been developed, because the conventional CCCP method does not consider the transient2)The analysis based on Micro-reactor physics shows that the angular distribution of neutron flux is greatly affected by the surrounding geometry and composition. Therefore, we considered the technique to measure the angular distribution of neutron flux in the core. The designed technique uses the optical fiber detector and Cd tube. The technique was applied to the measurement of the angular distribution in the core assembled in C-core tank at KUCA, and the technique was found to be effective to measure the angular distribution of neutron flux.3)The neutronics-thermodynamics coupling code has been developed to evaluate the effect of temperature distribution in fuel rods during the transient phenomena. The developed code was used to analyze the control rod drop accidents at the cold and hot stand-by states with the direct modeling of the heterogeneity of temperature distribution etc. in fuel rods. As the results, it is found that the analysis based on Micro-reactor physics is necessary and useful to consider the complex temperature distribution in fuel rods at a transient, and also the effective temperature model, which has a flat temperature distribution in fuel rods, bring the miscellaneous results because of the complex temperature, distribution.