Study on Micro Reactor Physics for Improvement of Neutronics Calculation

1)发展了考虑微堆物理效应的暂态分析理论，并在此基础上开发了计算程序。由于CCCP方法能严格模拟燃料组件中销钉电池结构等非均匀结构，并能在计算有效截面时处理非均匀问题，因此在改进的理论中采用了电流耦合碰撞概率方法(CCCP方法)；2)基于微堆物理的分析表明，中子注量角分布受周围几何和成分的影响很大，因此新的CCCP方法可以及时处理瞬变过程。因此，我们考虑了测量堆芯内中子通量角分布的技术。所设计的技术使用了光纤探测器和CD管。将该方法应用于库车C堆堆芯堆芯角分布的测量，结果表明该方法能有效地测量中子注量角分布。3)建立了中子学-热力学耦合程序，用于评估燃料棒在瞬变过程中温度分布的影响。利用所开发的程序，通过直接模拟燃料棒内温度分布的不均匀等，对冷备用状态和热备用状态下的控制棒掉落事故进行了分析。结果表明，基于微堆物理的分析方法对于考虑燃料棒内复杂的温度分布是必要的和有用的，而有效温度模型由于燃料棒内的温度分布是平坦的，由于其复杂的温度分布带来了繁杂的结果。

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.