有温度反馈时超瞬发临界瞬变

对输入大阶跃反应性(ρ0>β)和有温度反馈时的反应堆超瞬发临界变化过程进行研究。求得任意初始功率条件下反应堆反应性与功率的变化规律,并分析、讨论了输入反应性与初始功率大小对瞬发超临界变化过程的影响,给出一些有益的新结果,可为反应堆安全分析和运行管理提供重要的理论依据。     

非平衡态的中子增殖统一公式

导出了反应堆处于非平衡状态条件下的反应性阶跃变化时,反应堆从深度次临界到瞬发超临界整个区间通用的中子增殖统一的计算公式.通过对单组模型的修正,该公式还可以用于计算六组缓发中子的点堆中子动力学方程组.计算结果表明:利用修正后的单组解析方法计算阶跃反应性输入的中子密度响应问题,其计算结果与六组缓发中子的点堆中子动力学方程接近,精度满足工程计算要求.     

用去耦合法解有温度反馈的点堆中子动力学方程

当引入大阶跃反应性时,应用去耦合法求解中子动力学方程,导出了新的反应堆功率响应表达式,可用于堆实际运行的功率区。     

反应性阶跃变化从深次临界到瞬发超临界中子增殖统一公式

根据点堆公式导出了反应性阶跃变化时反应堆内中子增殖的统一公式,可用于反应堆深次临界、次临界、缓发超临界和瞬发超临界状态中子增殖计算.实例计算表明新推导的公式具有较高的计算精度,可用于定量分析与计算.     

反应性阶跃方法测量次临界反应性

反应性阶跃法和落棒法相似,均通过快速改变控制棒的位置快速改变反应堆反应性,但在实验条件上存在较大差异。本文以6群缓发中子点堆方程为基础,反应性阶跃假定为条件,得到了反应性阶跃法所适用的反应性方程,并采用CFBR-Ⅱ堆实验数据验证了该方法。     

渐进周期法测量反应性等待时间分析

反应堆功率增长达到渐进指数周期所需的等待时间是渐进周期法测量反应性的关键问题.本文从点堆动力学方程出发,求解了反应性阶跃变化后中子数增长的时间函数,分析了影响等待时间的物理因素,并为2种周期测量方法(2倍周期法和拟合e倍周期法)建立了测量周期随等待时间的误差函数.通过分析得到结论:等待时间与外源、缓发中子和初、终态反应性有关;拟合e倍周期法所需等待时间比2倍周期法短.     

基于Simulink输入阶跃反应性时有温度和毒物反馈的反应堆动态响应仿真

计算机仿真对核反应堆运行和核电人员的培训具有十分重要的意义.基于Simulink仿真软件,本工作对点堆中子动力学方程输入阶跃反应性考虑6组缓发中子时具有温度和毒物反馈的特性进行研究,计算了某型反应堆在两种典型工况下引入正、负阶跃反应性时各主要运行参数的变化规律,并将最终的结果与三维模型计算数据进行了对比.结果表明:利用Simulink进行点堆仿真研究能够高效、便捷地满足系统要求,且仿真结果与三维模型计算的数据符合得较好.     

考虑初始功率有温度反馈的缓发超临界分析

对输入小阶跃反应性(ρ0＜β)有温度反馈时,反应堆缓发超临界过程进行了研究.在功率与温度关系中考虑初始功率的作用,修正了绝热模型,求得了任意初始功率条件下反应堆反应性和功率随时间的变化规律,并进行分析、讨论.结果表明,初始功率对缓发超临界过程反应性与功率变化的影响明显,初始功率越大,反应堆反应性与功率的响应越快,且功率变化幅度也越大.     

铀氢锆反应堆脉冲参数分析

介绍了铀氢锆反应堆计算模型和程序，分析了反应性引入速率，反应性引入量，燃料瞬发负温度系数，燃料热容和瞬发中子寿命对脉冲参数的影响。计算结果表明，脉冲峰功率与反应性引入量的平方成正比；一次脉冲释放能量与反应性引入量成正比；燃料元件热容随燃料温度变化，脉冲峰功率和释放能量随燃料热容增大而增大。     

近临界系统中子倍增时间行为的实验测量

为确定近临界系统内中子倍增因子随时间的变化与系统的反应性的关系,为反应堆启动提供参考,实验测量了中心中子在1个快中子临界装置3个次临界状态的中子倍增的时间行为,在反应性ρ=-2.27×10^-3和-4.79×10^-4的两个次临界状态下,阶跃加入反应性,分别等待180和450s后,中子密度（正比于中子倍增因子）才达到稳定值。与单群缓发中子假设计算的变化曲线比较表明,实验测量的中子倍增因子的变化比理论预估的变化快。即使如此,在反应堆启动中,仍需考虑中子倍增的延迟,以便推算正确的反应性。     

New analysis of prompt supercritical process with temperature feedback

The prompt supercritical process of a nuclear reactor with temperature feedback and initial power while inserting large step reactivity (ρ₀ > β) is analyzed. The new analytic expressions of reactivity and output power as well as reactor's temperature increase during the course of the prompt supercritical are derived. The maximal power and the related reactivity and time are obtained. The effects of the inserted step reactivity and initial power on the prompt supercritical process are analyzed and discussed. It is found that for considering only the effect of prompt neutron the reactivity, power and temperature vary much more quickly and the power peak value and the increase values of temperature are larger than those for considering the effect of both prompt neutron and delayed neutron.     

Approximate solutions of point kinetics equations with one delayed neutron group and temperature feedback during delayed supercritical process

In the present investigation, the delayed supercritical process of a nuclear reactor with temperature feedback while inserting small step reactivity is analyzed. It is found that there exist some problems in the results obtained in the published literatures. The expression of relation between reactivity and time is derived, and the effects of the small inserted step reactivity and initial power on the delayed supercritical process are analyzed and discussed. To test the developed solution and to prove the validity of the method for application purposes, a comparison with other methods indicates the superiority of temperature prompt jump approximation. Some useful new conclusions are drawn, which can provide an important theory for the safety analysis and operating administration of the nuclear reactor.     

核临界安全中的监督现场测量技术--源倍增方法的某些问题

给出了核临界安全中监督现场的测量技术——源倍增法的实验理论和实验方法。源倍增法实际测量的是有源次临界中子有效增殖系数k2而不是中子有效增殖系数Keff。在铀溶液核临界装置上进行了实验研究用源倍增法测量了次临界系统在外中子源作用下铀溶液不同液位的有源次临界中子有效增殖系数k2;用周期法测量了单位铀溶液位的反应性系数,然后用临界液位与次临界液位之差乘以单位铀溶液位的反应性系数,给出系统次临界液位时的反应性．由反应性给出传统观念上的中子有效增殖系数keff 。讨论了它们的差别及对核临界安全的影响。     

Spectrum behavior for the nonlinear fractional point reactor kinetics model

The nonlinear fractional point reactor kinetics equation in the presence of Newtonian temperature reactivity feedback with a multi-group of delayed neutrons,which describes the spectrum behavior of neutron density into the homogenous nuclear reactors, is developed. This system is one of the most important stiff coupled nonlinear fractional differentials for nuclear reactor dynamics. The generalization of Taylor's formula that involves Caputo fractional derivatives is developed in an attempt to overcome the difficulty of the stiffness of the nonlinear fractional differential model. Moreover, the general fractional derivatives are calculated analytically throughout this work. Furthermore, the local and global estimated errors were analyzed, which suggest that the error quantification should take into account the possible grow in time of the error. This observation provides a motivation for going beyond more classical local-in-time concepts of error(local truncation error). The neutron density response with time is analyzed for the anomalous diffusion, sub-diffusion, and super-diffusion processes.     

经355 nm激光预处理后熔石英的损伤增长

为研究经预处理的熔石英损伤点随激光脉冲的增长关系,采用355 nm脉冲激光辐照预处理熔石英,再辐照位于后表面的损伤点,然后用Mias软件采集损伤增长的图像并测量每次脉冲后损伤点的面积。通过与未经预处理熔石英的损伤增长相比较可得出,经预处理与未经预处理的熔石英损伤点面积均随激光辐照脉冲数呈指数增长,但前者的损伤增长速度比后者的快。355 nm激光预处理能够有效提高熔石英元件的抗损伤阈值,但损伤一旦发生将会更加快速地扩展。     

中子倍增理论应用于碘坑仿真研究

采用中子倍增理论对碘坑仿真进行研究：首先,建立碘坑仿真模型;然后,将碘坑仿真模型对不同初始功率下反应堆突然停堆后的氙毒反应性变化进行计算,并将所得结果与点堆模型进行比较,计算结果表明,碘坑深度和初始功率呈线性关系;最后,将碘坑仿真模型应用于反应堆碘坑内机动性研究。本工作所得结论对反应堆安全分析和控制运行有一定的理论意义和参考价值。     

Solution of the point reactor kinetics equations with temperature feedback by the ITS2 method

The ITS2 method is used to solve the point-reactor kinetics equations in the integral formulation with arbitrary number of delayed neutron groups and Newtonian temperature feedback. The method is based on low-order Taylor series expansions of neutron density and reactivity functions and uses variable time steps to control the numerical instabilities resulting from the stiff nature of the governing equations. Time steps are determined through an analytic criterion relating their magnitudes to the maximum admissible truncation error in the neutron-density expansion series. Temperature feedback is included in the reactivity as a function of the neutron density for different input types, including step change with adiabatic temperature feedback and compensated ramp functions. An iterative procedure is applied to determine the time steps while simultaneously updating the reactivity function. Numerical results show the ITS2 method is highly accurate for solving point reactor dynamics problems with temperature feedback.     

Analysis of prompt supercritical process with heat transfer and temperature feedback

The prompt supercritical process of a nuclear reactor with temperature feedback and initial power as well as heat transfer with a big step reactivity (ρ0>β) is analyzed in this paper.Considering the effect of heat transfer on temperature of the reactor,a new model is set up.For any initial power,the variations of output power and reactivity with time are obtained by numerical method.The effects of the big inserted step reactivity and initial power on the prompt supercritical process are analyzed and discussed.It was found that the effect of heat transfer on the output power and reactivity can be neglected under any initial power,and the output power obtained by the adiabatic model is basically in accordance with that by the model of this paper,and the analytical solution can be adopted.The results provide a theoretical base for safety analysis and operation management of a power reactor.     

Sensitivity analyses of the use of different reflector materials on the neutronics parameters of Tehran research reactor

In this paper, the effect of changes in neutron reflector type on neutronics parameters of Tehran research reactor is analyzed. In this study, at first, calculations for the HEU and LEU fuel configurations of the reactor core in which the light water is used as a neutron reflector in the core is done. Then, by using the reflectors such as graphite, beryllium and heavy water, changes on the neutronic parameters are examined. The results show that by altering the reflector, at HEU core configuration (compared with LEU), more changes appear in parameters such as neutron multiplication factor, average fast and thermal neutron flux, excess reactivity and shut down margin. Moreover, at LEU core configuration, changes are tangible specifically on parameters of cycle length and power peaking factor. In addition, the evaluated fuel temperature coefficient of reactivity is greater at HEU than LEU, while the temperature alteration of fuels represented greater influence on reactivity at LEU configuration.