快堆钠回路水锤程序开发与应用

本文在基于一维特征线法（MOC）的传统的压力波传播的数学模型中补充和完善了钠腔-气腔外边界模型，同时采用了气泡离散模型模拟低压液柱分离形成的蒸汽穴的生成与溃灭。在此基础上编制了专用程序WHA，利用该程序对快堆实验钠回路中由于阀门的快速开启与关闭引起的压力波的传播进行了分析计算，计算结果的合理性表明了包括钠腔-气腔在内的水锤压力波传播的数学模型的有效性和程序计算的可行性。     

大泄漏钠水反应引起压力波传播的研究

快堆蒸发器内管道发生破损、断裂，水／水蒸汽泄漏涌入液钠空间，会产生剧烈的钠水反应事故，瞬时激发很强的压力波，危及管路和部件。为此要求建立一组完整的钠水反应引起压力波传播的数学模型，进行数值计算，定性分析其基本特征。水力实验证明压力波传播数学模型是正确的，实验钠回路的数值计算也说明全组模型是合理的     

蒸汽发生器大泄漏钠-水反应引起的二回路压力波传播

研究建立了钠冷快堆蒸汽发生器在单管束发生双端断裂情况下钠－水反应中气泡从球形到柱状的变温绝热生长模型,及采用一维特征线方法建立的压力波在快堆二回路中的传播模型。模型中考虑了爆破膜、管壁弹性变形和气蚀的影响。对在两相汽水混合区发生大泄漏后有、无爆破膜情况下的钠－水反应和二回路压力传播瞬态进行了计算,定性分析了其影响以及爆破膜在钠－水反应中的安全保护作用。     

CEFR二回路水锤分析

CEFR以液态钠作为一、二回路冷却剂。二回路蒸汽发生器泄漏发生钠水反应会在二回路系统中引起水锤,水锤事故可以引起管道的甩摆,拉断管道支撑,使管道破裂,甚至直接造成核电厂事故停堆。因此,水锤是CEFR设计和安全分析中的一个重要问题。本工作在清华大学按照CEFR一、二回路系统初步设计参数编制的水锤分析程序的基础上,采用CEFR二回路冷却系统施工设计参数重新进行分析计算。CEFR二回路水锤分析@唐龙 @王彬     

铅铋介质闭式换向器运行特性与水锤现象研究

为研究闭式换向器在液态铅铋合金（LBE）介质换向过程中的流量稳定性及其适用性,采用FLUENT软件结合重叠网格方法对三通切换阀形式的闭式换向器换向时上游的压力与速度波动进行计算分析。结果显示,换向过程中,阀芯启动及停止运动时产生水锤,水锤波以介质声速在管道中传播,从而影响管道内压力和速度的分布,水锤波的峰值大小与介质密度、阀芯运动速度成正比,水锤波频率不受阀芯运动速度影响。由于水锤波的波峰值较大,使此类型闭式换向器在LBE下换向动作时上游管道难以维持稳定流量并威胁装置安全,故在LBE流量标定装置中不适用。     

基于耦合程序的流体瞬变流动水锤现象分析

水锤现象严重威胁系统的安全,而设备的启闭是产生水锤现象的重要因素之一。本文针对并联双泵系统建立耦合程序,计算研究泵启动和阀门关闭时的流体瞬变水锤现象。验证过程证明了耦合程序的正确性,并将三维稳态模型计算结果与实验结果进行了对比,二者符合良好。瞬态分析中,动网格技术成功模拟阀门关闭,并获得了闭合时阀内的重要热工水力参数。通过对比泵启动耦合计算结果与传统RELAP5计算结果可知,耦合程序能正确预测水锤压力波和水锤载荷。耦合分析较一维计算能更直观地展现系统中重要设备内的流体瞬变特性。计算获得的三维瞬态特性能对阀门的设计和优化提供重要的参考。     

压水堆核电厂三回路停泵水锤数值模拟

应用停泵水锤的基本理论．建立了压水堆核电厂三回路水泵、泵出口阀、冷凝器和出水虹吸井等边界条件的数学模型．并采用特征线法进行求解结合工程实例计算说明．泵出口阀的关闭程序对水锤压力的影响较大．水泵出口采用两阶段关闭液控蝶阀可以有效减小停泵水锤压力．但其关闭程序应在水锤数值模拟分析的基础上优化确定。     

止回阀水锤分析

文章分析了止回阀水锤过程,求解了阀板运动微分方程,得到阀门开度无量纲数τ(t)的计算公式。用特征线法计算了止回阀水锤压力波。结果表明,偏置止回阀的水锤压力波最大峰值仅是悬挂式止回阀水锤压力波最大峰值的1/3。增大阀板的转动惯量J、加大限位角Φ_0可以减小水锤压力波峰值并能缓和阀板的振动。分析计算与实验结果符合得较好。     

钠冷快堆主回路系统的建模及动态仿真

采用模块式结构,建立了一套钠冷快堆主回路系统的数学模型。在有效的仿真工具DSNP的有力支持下,该模型具有简便实用、替换灵活、适应面广的独特优点,以此模型为基础,编制了计算快堆主回路系统动态过程的仿真程序,并对EBR-Ⅱ的4个试验瞬态进行了实际计算。     

压水堆主回路失水事故下水锤与管道结构的相互作用分析

传统的水锤分析和管道动力响应计算是分开的,存在一定的缺陷。本文针对核电站主回路假想双端断裂时系统的受力和力矩分析这一问题,对破裂管道分充体和管道的耦合机制,引入描述流体－管道单元的１４个参数和１４个偏微分方程,利用特征线法对水锤和管道结构的相互耦合作用进行了模拟计算。计算得到了更为准确的水锤波和管道的受力和力矩,其波形和数值均与不考虑耦合作用时有所不同。这些计算结果为压水堆核电站的核安全设计和分析     

Using Anemometer for Particle Size Measurement of Sodium Mist

A code “ACTFCI” has been developed for analyses of Fuel Coolant Thermal Interaction in a coolant channel. The code can deal with the dynamic behavior of coolant in r-z geometry, but does not take into account the dynamics of fuel particle two-dimensional movement, the fuel being considered only as heat source for the coolant. The ICED-ALE method was used for the numerical analyses of the three conservation equations and two equations of state for single and two-phase sodium. A sample calculation is given concerning the period up to initiation of sodium boiling, for a geometry representing a wrapper tube of reduced size. Despite this difference of the model from actual size, the calculated results suffice for demonstrating the utility of this method in obtaining stable solutions on single-phase pressure wave propagation in both r and z directions, and on sodium boiling initiation triggered by the rarefaction wave returning to the interaction region from channel extremity.     

Density Wave Instability of Sodium Boiling Two-phase Flow in a Vertical Annulus at Low Pressure

Experiments of density wave instability in a sodium boiling two-phase flow in an annulus were carried out with the parameters of heat flux from 80 to 976kW/m², inlet subcooling from 25.6 to 226.8°C, mass flow rate from 7.92 to 68.9 kg/h, and system pressure from 2,600 Pa to 0.06 MPa. It was found that the density wave instability occurred in the case of low exit quality, and the oscillation of flow rate was so large that the flow would be reversal. The lower inlet temperature, the higher system pressure and the larger mass flow rate could result in a more stable boiling two-phase flow. The oscillation period of the instability increased with the system pressure and the inlet subcooling, but it decreased with the mass flow rate. A correlation for the onset condition of the density wave instability was obtained from the experimental data.     

钠冷行波堆和驻波堆堆芯特性对比分析

采用自开发的MCNP-ORIGEN耦合程序MCORE对所设计的钠冷行波堆和驻波堆开展中子学和燃耗分析;基于MCORE获得的功率分布,采用自开发的钠冷快堆堆芯稳态热工水力分析程序SAST对钠冷行波堆和驻波堆堆芯开展热工水力分析。对比钠冷行波堆和驻波堆的堆芯物理特性和热工水力特性,结果表明：驻波堆在燃耗、最高包壳和燃料芯块温度方面具有优势,而行波堆在反应性波动和堆芯冷却剂出口温度均匀性方面具有优势。     

A study on sodium spray combustion

Sodium spray combustion was studied through experiments and analysis, in order to clarify the burning rate, pressure and temperature transients in a sodium spray fire. In the experiments, about 400 g sodium was sprayed in a closed vessel of 2 m³, containing nitrogen and 0–21 vol% oxygen. Pressure, temperature and oxygen concentration were measured during and after sodium injection. The experimental results revealed that the temperature in the spray outer region was higher than that of inner region and observed oxygen consumption was not more than 80% of that expected for complete combustion of sodium. To analyze the experiments, a computer program SOFIA-II was developed based on an analytical single droplet combustion model and a two-dimensional temperature and oxygen concentration distribution model in the vessel. The calculated pressure agreed with the experimental pressure on the whole and the peak pressure difference was within 10% error.     

钠冷快堆钠池火事故数值模拟

为了估计和预测钠火事故的后果，构建了以“有火焰薄层”为理论基础的燃烧模型和热传输模型，给出了程序计算结果与试验值的比较。比较结果证实，该计算结果可信、模型合理。程序可用来分析和预测钠池火事故。     

基于多孔介质模型的行波堆TP-1堆芯稳态温度场与流场数值模拟

根据TerraPower公司最新设计的钠冷行波堆TP-1的具体结构和运行特点,采用多孔介质模型,使用商用软件CFX对行波堆堆芯的热工水力特性进行数值模拟,得到了TP-1稳态运行条件下堆芯温度场、速度场和压力场分布。结果表明：应用多孔介质模型对行波堆堆芯进行三维热工水力数值模拟的方法直观、快速、有效,将它应用于行波堆堆芯稳态条件下三维流场和温度场分析具有一定的意义。     

A theoretical model with variable masses for the molten fuel-sodium thermal interaction in a nuclear fast reactor

In the model proposed in this paper, the reaction has been asumed to occur in two successive phases, A and B.

1. Phase A. A given number (function of time) of fuel particles come into intimate contact with a given mass of liquid sodium (function of time). The heat transfer process is characterized by good direct thermal contact between the fuel and the liquid coolant, and by a large contact area due to the small size of the particles. The heat transfer coefficient decreases with time due to the formation of a temperature profile inside the fuel particles. The heated volume of sodium is constrained by the surrounding unheated coolant and by the other materials present in the core. The mechanical constraint is schematized by a sodium column of finite length which is contained in a channel located above the reaction volume. The sudden expansion of the heated volume first produces acoustic waves which travel along the sodium column. Later the sodium column behaves like a piston which is pushed inertially upwards. The pressure rises, reaches a maximum, and then falls as soon as the expansion of the liquid sodium becomes inportant. At the time at which the pressure reaches the saturation point, sodium boiling starts and phase B begins.

2. Phase B. The heat transfer process is now characterized by a very large contact area, and by thermal contact between the fuel and coolant which becomes increasingly worse with time, due to the formation of a sodium vapour layer at the external surface of the fuel fragments. The sodium will boil in a large quantity, and will therefore produce large volume changes. The sodium piston will be further accelerated and its movement will allow the pressure in the reaction volume to decrease.

The model accounts for the time history of the temperatures of each fuel particle by means of the use of specially averaged temperature values. The calculation of the heat transfer coefficient during phase B is based on experimental results. The presence of fission gases can also be taken into account. A size distribution of fuel particles has also been incorporated into the model as well as the effect of friction due to the channel walls and that of the pressure losses at the outlet of the channel. Numerical evaluations are also included and the results are discussed. It has been concluded that the total work produced decreases with the time scale of the vapour film layer around the particles and increases with the speed at which the fuel breaks down into fragments and mixes with the liquid sodium. The effect of sodium column length has also been investigated.     

Investigation of the fast magnetosonic wave excited by the Alfvén wave phase mixing by using the Hall–MHD model in inhomogeneous plasma

The inhomogeneity is introduced by a nonzero density gradient which separates the plasma into two different regions where plasma density are constant. The Alfvén waves, the phase mixing and the fast magnetosonic wave are excited by the boundary condition in inhomogeneous magnetized plasma. By using the Hall–magnetohydrodynamics(MHD) model, it is found that there are Alfvén waves in the homogeneous regions, while the phase mixing appears in the inhomogeneous region. The interesting result is that a fast magnetosonic wave is excited in a different direction which has a nonzero angle between the wave propagation direction and the direction of the background magnetic field. The dependence of the propagation direction of the excited fast magnetosonic wave and its strength of the magnetic field on the plasma parameters are given numerically. The results show that increasing both the driving frequency and the ratio of magnetic pressure to thermal pressure will increase the acceleration of the electrons. The electron acceleration also depends on the inhomogeneity parameters.     

铅基快堆SGTR事故下热工水力模拟及气腔扩散行为研究

本文针对铅基快堆蒸汽发生器传热管破裂（SGTR）事故,利用计算流体力学（CFD）程序对LIFUS5/MOD2台架的汽水注射进液态金属铅铋环境进行研究。研究了3种热工水力现象：铅铋环境压力上升与压力波传递,铅池液位波动和气泡夹带与铅池液位上升和蒸汽扩散。研究结果表明：CFD模型在模拟SGTR事故的压力变化和压力波传递方面具有很小的计算误差;压力波峰值会随着水侧背压的升高而增大,且局部的蒸汽腔压力会低于附近的铅池压力,抑制蒸汽爆炸发生;同时事故引起的铅铋液位上升既会引起小尺寸气泡的输运夹带,也会对铅铋环境结构件造成冲击。     

Flooding correlation based on the concept of hyperbolicity breaking in a vertical annular flow

Flooding is classified into exit flooding and entrance flooding depending on the positions at which it is initiated. It is postulated that flooding may result from the instabilities of roll waves and the stationary wave generated at the entrance and the exit respectively. Based on the two-fluid model, the neutral stability condition for wave instabilities is derived by studying hyperbolicity breaking near a singular point in two-phase flow. It turns out to be a type of onset condition of Helmholtz instability; the critical relative velocity depends on the void fraction derivative of the interfacial pressure force as well as on the void fraction and density ratio. In order to obtain information on the interfacial pressure force, a Korteweg-de Vries solitary wave is studied with the assumption that its wavenumber is the same as that of the fastest-growing sine wave. Predictions by the correlations for entrance flooding and exit flooding are in good agreement with experimental data. Also, the present model is able to consider the effect of the test section length on flooding.