单位瞬态法在核电厂疲劳监测系统中的应用

核电厂疲劳监测系统中的非稳态导热反演计算是关键步骤,本文提出的单位瞬态法目的就是解决反演计算问题。首先研究了一维瞬态热传导内外壁温度的线性关系,其次建立了单位瞬态热传导有限元模型,然后通过数值计算实现了由内壁温度计算外壁温度或由外壁温度计算内壁问题双向计算过程,最后通过1组试验数据验证单位瞬态法的正确性,为疲劳监测系统的推广应用奠定了基础。     

铀氢锆瞬态实验装置计算程序的研发

本文针对新型核反应堆电源系统物理特性研究的铀氢锆瞬态实验装置,结合点堆动力学方程、非稳态热传导方程和热弹性动力学方程,研发了专用于铀氢锆瞬态实验装置实验过程模拟的瞬态计算程序。以保健物理研究堆（HPRR）为例,利用研发的程序进行模拟,得到HPRR的功率、反应性、温度和径向位移随时间的变化。程序的计算结果与Fuchs-Hansen模型的结果较为一致,验证了该瞬态计算程序的正确性。     

铀氢锆瞬态实验装置计算程序的研发

正铀氢锆瞬态实验装置是一种新的概念设计,如图1所示。主要用于研究采用块状铀氢锆材料的小型核反应堆电源的物理特性及其启动、运行的特点。为保障铀氢锆瞬态实验装置的安全运行,需要为其配备相应的瞬态计算程序以模拟其启动、运行的过程。本文结合点堆动力学方程、非稳态热传导方程和热弹性动力学方程,开发了专用于铀氢锆瞬态实验装置的瞬态计算程序,用于模拟其启动过程中功率、温度、反应性等物理量的变化情况,并     

蒸汽发生器水位控制瞬态分析及计算优化

蒸汽发生器水位控制的瞬态计算与分析是评估、预测核电站反应堆停堆、汽轮机停机的重要途径。目前的瞬态计算方法,大多未将控制过程纳入计算模型中,且核岛、常规岛按设计边界划分进行独立计算。本文将CPR1000核岛、常规岛瞬态控制过程进行整体分析和计算,在现有瞬态计算方法的基础上,在模型中加入了反馈控制环节,提高了计算的准确度。通过对计算结果及模型的误差进行分析,提出指导设计及运行的结论,进一步提高计算准确度的方法。     

室内氡气传输的数值模拟

根据粒子输运理论和气体分子动力学,建立了室内氡的二维瞬态传输模型,提出了与过去不同的边界条件。利用差分方法离散了室内氡的三维瞬态传输方程、渗流速度方程、压差方程以及定解条件。通过编程计算,对室内氡的三维瞬态传输过程进行了数值模拟。与实测的室内氡浓度比较,计算值与实测值符合得比较好。同时,还模拟了环境气压、气     

利用有限元法求解二维热传导方程

本文采用一种技巧克服了变分原理的困难,使得有限元法成功地应用到二维热传导方程在曲面边界和曲面接触面的条件下,求得了较精确的数值结果。     

核燃料溶液系统瞬态特性分析研究

在核反应堆乏燃料后处理主工艺流程中,核燃料通常以溶液状态存在,可能发生核临界事故。研究核临界事故的产生机理和事故源项,对预防事故发生、缓解事故后果、事故应急响应与医学诊治均具有十分重要的意义。本文采用点堆动力学方程结合二维热传导方程,开发了基于圆柱形溶液贮存容器的瞬态特性分析程序GETAC,利用该程序计算了法国SILENE瞬态实验装置模拟临界事故功率随时间的变化,得到了功率振荡在不同反应性引入大小、方式和有无外中子源等情况下的变化规律,计算分析结果与瞬态实验测量数据以及国外其他程序计算结果较一致。     

SuperLWR在超临界压力下的安全分析

本文描述了带有向下流水棒的高温超临界水冷热堆（称为Super LWR）在超临界压力下的安全分析。选择了11种瞬态和4种事故作为安全分析所考虑的异常类型。包壳温度而不是热流密度被认为是重要的瞬态准则。直流冷却系统和向下流水棒系统体现了Super LWR的安全特征。与沸水堆（BWR）和压水堆（PWR）不同,BWR和PWR“失去给水”同“失去反应堆冷却剂流量”一样重要。然而,向下流水棒通过热传导排出燃料通道的热量并依靠体积膨胀向燃料通道提供水量,在辅助给水系统启动前将缓解堆芯加热。在加压瞬态期间,与BWR不同,由于单相流中不存在空泡溃灭和在直流冷却系统中由流动停滞引起的冷却剂密度降低,Super LWR反应堆功率不会显著增加。所有瞬态和事故都满足准则要求。最热包壳温度在瞬态下大约增加50℃,在事故下最多增加250℃。瞬态下包壳处于高温的时间很短。     

三维结构瞬态温度,位移和热应力计算的等效时间法

本文提出了一种计算二维结构瞬态温度，位移和热应力的近似方法－等效时间法。利用事先得出的热边界幅值的单位变化所引起的结构响应的有限元分析结构。通过简单的代数运算即可求出同样热边界模式下热边界模式下热边界幅值的任意变化过程在结构中产生的响应。这种近似方法有很高的计算效率。通过算例表明，与详细的有限元计算结果相比，在工程允许的范围内误差满足工程需要。等效时间法可肜于对计算效率要求较高的复杂结构的实时分析     

钠冷快堆蒸汽发生器的模块化模型及瞬态仿真研究

研究了钠冷快堆电厂直管式直流蒸汽发生器可移动边界的模块化模型。采用ＭＡＴＬＡＢ语言,Ｃ语言编程与ＳＩＭＵＬＩＮＫ仿真工具相结合的建模方法,建立了仿真系统,对直管式直流蒸汽发生器的瞬态特性进行了研究,并获得了令人满意的结果。     

Effects of Boundary Conditions on Thermal Response of a Cellulose Acetate Layer Using Hottel’s Zonal Method

Energy can transfer internally by radiation in addition to conduction in translucent polymers. Since radiant propagation is very rapid, it can provide energy within the layer more quickly than diffusion by heat conduction. Thus, the transient thermal response of a layer for combined radiative and conduction may be extremely different from that of conduction alone. In this paper, the behavior of a heat conducting, absorbing, and emitting layer of Cellulose Acetate layer is investigated during the transient interval when both conductive and radiative heat transfer are considered. Specifically, the effects of boundary conditions on the response of the layer are considered here. These boundary conditions include both conductive boundary conditions, such as convection coefficient and convective fluid temperature, and radiation boundary conditions, like radiation surrounding temperature and specular reflectivity. To this end, the governing differential equations including the equation of radiative heat transfer within the material coupled to the transient energy equation with radiative terms are presented. The solution procedure is based on nodal analysis and Hottel’s zonal method extended by the ray tracing method. The transient energy equation including the radiative internal energy source is solved using a time marching finite difference procedure with variable space and time increments.     

Finite element formulation and solution of nonlinear heat transfer

A general and effective finite element formulation for analysis of nonlinear steady-state and transient heat transfer is presented. Heat conduction conditions, and convection and radiation boundary conditions are considered. The solutions of the incremental heat transfer equations is achieved using Newton-Raphson iteration, and in transient analysis using a one-step α-family time integration scheme. The stability and accuracy of the time integration is discussed. The solution techniques have been implemented, and the results of various sample solutions are discussed and evaluated.     

Transient heat conduction problems in inhomogeneous media discretized by means of boundary-volume element

An integral equation formulation is presented for the transient heat conduction problems in inhomogeneous media. The material constants are assumed to be prescribed as arbitrary, continuous and differentiable functions of position vector. The governing integral equations are derived from the weighted residual statement of the problems in which the fundamental solution to the corresponding heat conduction problems in homogeneous media is used as the weight function. The whole domain of interest is discretized into a series of boundary-volume-time elements, and then a set of linear simultaneous equations are obtained. Their solutions yield the temperature in the whole domain as well as the heat flux on the boundary.     

Transient Heat Transfer Analysis of a Layer by Considering the Effect of Radiation

The transient heat transfer analysis of a layer has been studied much less than the steady state. However, transient temperature distribution resulted from including radiation and conduction simultaneously, is significantly different from those obtained by considering conduction alone. In order to include the effect of radiation heat transfer, we must insert the gradient of radiative flux in the energy equation. For this purpose, a variety of multi-flux methods have been suggested. A simplified procedure is the two-flux method, which is the one used in the present paper. This paper is focused on one-dimensional transient heat transfer of a layer using Finite Difference Method. To this end, a computer implementation has been written, which is based on implicit finite difference formulation and is capable of considering effect of radiation. By subjecting the layer to various boundary conditions, the effect of variation of refractive index and scattering on transient temperature distribution is discussed.     

Transient Temperature Response of an Annular Flow with Step Change in Heat Generating Rod

An analysis is made on the transient temperature response of fluid and of heat generating rod in the case of annular flow. Special consideration is given to the effects of the rod heat capacity and radial thermal conduction in the rod during the transient.

The analysis is based on the following assumptions: (1) Initially the system has a uniform temperature distribution, and the rod undergoes a step change in heat generation; (2) the temperature of the fluid entering the annular space is kept constant; (3) the velocity distribution of fluid is uniform; (4) all physical properties remain unchanged during the transient; (5) axial thermal conduction in the rod is neglected in comparison with that in the radial direction; (6) axial thermal conduction in the fluid is neglected in comparison with axial thermal convection.

The present result is compared with values by quasi-static solution for various heat transfer parameters.     

Analysis of transient heat conduction with phase changes by a boundary integral equation method

A combined method of a latent heat model and a boundary integral equation is presented for solving transient heat conduction problems with solidification and melting. Some typical problems are solved in order to confirm the validity of the proposed method. The present results show good agreement with results obtained by using finite difference, finite element and boundary element methods. It is shown that the method admits the use of rather large time steps and a relatively coarse mesh. The computational property of the function which is introduced in deriving the boundary integral equation is discussed in connection with a condition for smooth motion of the interface.     

Application of conformal mapping to the determination of unsteady temperature distribution in thermally orthotropic plates

Very few papers and reports are available on the solution of heat conduction problems in anisotropic solids. This situation is of particular interest in some nuclear engineering applications (for instance, fuel elements possess, in general, anisotropic characteristics). The present study deals with the solution of an unsteady heat conduction problem in domains of complicated boundary shape, considering a particular case of anisotropy: a thermally orthotropic material. It is shown that the conformal mapping technique coupled with the Ritz method leads to a unified solution of the title problem for an arbitrary orientation for the axes of orthotropy with respect to the directions of the sides of the plates.     

K-FIX程序开发及其在自然对流中的应用

在洛斯－阿拉莫斯科学实验室开发的多维两流体瞬态流动计算程序Ｋ－ＦＩＸ基础上,补充边界传热条件及单相传热、粘性力等项,使之可以用于计算自然对流工况。用扩展后的Ｋ－ＦＩＸ程序计算自然对流状态下的流场和温度场,与ＣＯＭＭＩＸ－１Ａ程序的计算结果符合良好。     

Steady state and transient temperature profiles in a multishell spherical system heated internally by reactor-grade plutonium

Steady state and transient temperature distributions are analysed for multishell spherical systems which are heated in their inner part by the alpha-particle heat power of reactor-grade plutonium. Different geometrical thickness of the spherical shells and temperature dependent thermal material properties are assumed. Boundary conditions at the surface of the multishell system are natural convection by air and thermal radiation or cooling by cryogenic liquids. In addition, cooling by internal thermally conducting structures in outer shells is investigated by applying an approximate heat conduction model. The steady state and transient temperature distributions allow defining limits for alpha-particle heat power at different outer boundary conditions for which e.g. the melting points or other temperature limits of different materials are exceeded.     

Transient behavior of the sodium–potassium alloy heat pipe in passive residual heat removal system of molten salt reactor

High temperature heat pipes, as highly-effective heat transfer elements, have been extensively employed in thermal management for their remarkable advantages in conductivity, isothermality and self-actuating. It is of significance to apply heat pipes to new concept passive residual heat removal system (PRHRS) of molten salt reactor (MSR). In this paper, the new concept PRHRS of MSR using sodium–potassium alloy (NaK) heat pipes is proposed in detail, and then the transient behavior of high temperature NaK heat pipe is numerically investigated using the Finite Element Method (FEM) in the case of MSR accident. The two-dimensional transient conduction model for the heat pipe wall and wick structure is coupled with the one-dimensional quasi-steady model for the vapor flow when vaporization and condensation occur at the liquid–vapor interface. The governing equations coupled with boundary conditions are solved by FORTRAN code to obtain the distributions of the temperature, velocity and pressure for the heat pipe transient operation. Numerical results indicated that high temperature NaK heat pipe had a good operating performance and removed the residual heat of fuel salt significantly for the accident of MSR.