墙壁反射中子对脉冲堆波形的影响  

Influence of reflected neutrons of wall on waveform of burst reactors

作　　者：高辉[1] 宋凌莉[1] 李兵[1] Gao Hui;Song Ling-Li;Li Bing(Institute of Nuclear Physics and Chemistry,China Academy of Engineering Physics,Mianyang 621900,China)

机构地区：[1]中国工程物理研究院核物理与化学研究所,绵阳621900

出　　处：《物理学报》2018年第17期72-76,共5页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11775197)资助的课题~~

摘　　要：墙壁的反射中子会对快脉冲堆的波形产生明显的影响.堆芯中子泄漏后,经过墙壁的反射有一定的概率返回堆芯,由于能量的差异,泄漏中子的返回时间是一个连续的分布.传统的双区模型只考虑了相互作用概率,而没有时间信息,尽管可以很好地解决稳态问题,而无法解决瞬态问题.本文采用等效的方法,把泄漏中子等效为时间相关的堆芯本征源,建立了含有反射效应的时间关联双区模型.求解得到的脉冲波形与CFBR-Ⅱ的实验结果一致,从而合理解释了脉冲波形后沿衰减变慢和坪功率提高的实验现象.The reflected neutrons from the wall of the reactor have a significant effect on the waveform of the fast burst reactor. The leakage neutrons from the reactor core have a certain probability that they will come back. Their return time displays a continuous distribution because of the difference in energy among the reflected neutrons. In the stable state, the influence of the reflected neutrons is not obvious. However, in a prompt state, it is obvious because the reflected neutrons are not synchronized with the neutrons in the reactor core, which leads to some strange phenomena in experiment. For example, in the process of erupting a fission burst in a metal reactor, the number of neutrons in core increases very rapidly, while the return time of reflected neutrons lags behind, which causes the falling edge to slow down.The two-region kinetic model, which divides the reactor core into a fission region and a reflected region, is generally used to study the reflected reactor. The traditional two-region kinetic model only takes into account the interaction probability between the two regions but the time property of the interaction is not considered at all. Therefore, the traditional two-region model can well describe the stable state process rather than the prompt one. In the early stage,the delayed neutron approximation method was used to study the reflected neutron problem of metal burst reactors.Although some parameters were obtained to be in accordance with the experimental results, there existed a significant difference in behavior between delayed neutrons and reflected neutrons. In this paper, we present a time-dependent two-region model which can effectively describe the behavior of the reflected neutrons in both stable and prompt states.Firstly, we use the Monte-Carlo method to calculate the returning behavior of one leakage neutron from the reactor core. The equivalent eigen source is obtained by solving the kinetic equation with the Monte-Carlo calculating result.This source, including time information, cau

关 键 词：反射中子 等效中子 脉冲堆 动力学方程 

分 类 号：TL32[核科学技术—核技术及应用]