基于RELAP5平台的LOCA评估程序中喷放模型与CHF模型的修改与验证

为开发核电厂保守性的冷却剂丧失事故(LOCA)安全评审用程序,本文按照10CFR50附录K的核电厂失水事故评估模式要求,对RELAP5 / MOD3.3的两相喷放模型与临界热流密度(CHF)模型进行了修改,并与Marviken Test-22和ORNL THTF相关试验结果分别进行比较,探讨了模型修改的合理性与保守性,为进一步完成认证级LOCA安全评估程序奠定了初步基础.     

基于RELAP5的螺旋管蒸汽发生器热工水力程序研发与验证

由于较高的换热效率和紧凑的结构设计,螺旋管式直流蒸汽发生器（HCOTSG）在多种模块化小型堆的设计中得到了广泛应用。RELAP5作为广泛应用于反应堆热工水力特性分析的大型系统程序之一,采用的热工水力关系式仅针对直管模型开发,不适用于HCOTSG一次侧和二次侧。本文选用螺旋管及横掠管束的热工水力模型,基于RELAP5程序开发了HCOTSG模块。采用实验数据及程序对比等方式对螺旋管模块的流动和换热模型进行了单独验证,利用开发的RELAP5-HCOTSG程序针对国际革新安全反应堆（IRIS）的蒸汽发生器设计进行了整体的热工水力模拟,与原始RELAP5的计算相比,RELAP5-HCOTSG程序计算得到的热工水力参数与设计值符合良好,确认了本文开发的程序模块在HCOTSG热工水力分析中的适用性。     

基于缩比模型的AP1000自动泄压系统泄压工况下内置换料水箱过冷水流动特性实验研究

以AP1000为原型,搭建整体缩比实验台架,模拟内置换料水箱(IRWST)中自动泄压系统(ADS)泄压工况下,高温高压蒸汽在水下的喷放、冷凝过程,主要利用热电偶点阵、粒子图像测速(PIV)等技术监测喷洒器附近蒸汽喷放过程中的行为以及池内三维温度场、速度场分布。通过对喷放情况下内置换料水箱内过冷水的热分层及自然循环现象的研究,提出优化方案,从而提高内置换料水箱中水的利用率。     

System Code Calculation and Experimental Verification for Double-hole Steam Jet Condensation Heat Transfer Process Based on ADS1 3 Scaled Model

The steam direct contact condensation of high-temperature steam in sub-cooled water is an important way to reduce the temperature and pressure in the primary circuit in the third generation of advanced pressurized water reactors such as AP1000 and CAP1400 in the event of accidental overpressure. Based on the system codes of RELAP5 and COSINE, the process of saturated steam injecting into large volume sub-cooled water through a double-hole nozzle was modeled, calculated and analyzed. The temperature distributions along the axial direction of the high-temperature steam ejected from the nozzle were obtained. At the same time, the visual experiments of steam jet condensation were performed. The thermocouple matrix and high-speed camera were used to measure the key thermal-hydraulic parameters to obtain the temperature distributions along the steam plume and the flow patterns of the steam jet, which were used to verify the accuracy of the system code to simulate the process of steam spraying and condensation. The results show that the system code RELAP5 can basically simulate the general trend of ADS steam condensation process under the simplified model. The average error of the simulation results is 2.97% compared with the experimental results. In addition, the COSINE code was used to further modify and improve the model of the spraying condensation process. Considering the influence of the overall flow in the water tank on the condensation characteristics, the simulation results fit well with the experimental results, with an average error of 1.89%. However, the actual double-hole spraying process is complex and has obvious three-dimensional characteristics, so the relevant condensation heat transfer model in the system code still needs to be further improved to simulate its local condensation characteristics more accurately.     

含不凝性气体蒸汽浸没射流冷凝压力振荡实验研究

实验研究了不凝性气体（空气）含量、水温和蒸汽质量流速对蒸汽浸没射流冷凝压力振荡特性的影响,实验工况横跨冷凝振荡（CO）区和稳定冷凝（SC）区。结果表明：对于纯蒸汽射流,压力振荡主频随水温的升高而降低,振荡强度随水温的升高而升高;在CO区,振荡主频和振荡强度均随蒸汽质量流速的升高而升高;在SC区,振荡主频随蒸汽质量流速的升高而降低,振荡强度基本上不随蒸汽质量流速的变化而发生改变;对于含空气射流,随空气质量分数的增加,振荡主频总体呈下降趋势,振荡强度先迅速下降后小幅上升,在空气质量分数为0.05～0.1区域内振荡主频和振荡强度均存在极小值。     

水平管内蒸汽冷凝局部换热特性实验研究

以水蒸气为工质,实验研究了水平管内纯蒸汽冷凝的局部换热特性。实验选取换热管内径为25 mm、换热管进口压力为0.15~0.4 MPa、局部蒸汽的Re=5756~92289,分析了蒸汽压力及流速、壁面过冷度对冷凝传热系数的影响,并将采用现有关系式计算的冷凝传热系数与实验结果进行了对比。结果表明：冷凝传热系数随壁面过冷度的增大而减小,随压力的升高和流速的增大而增大;采用现有关系式计算的冷凝传热系数与实验值的偏差较大,关系式有待进一步改进;在实验范围内,由拟合换热关系式计算所得冷凝传热系数与实验结果的相对偏差在15%左右。     

振荡区下蒸汽冷凝过程的热工水力模型建立及验证

蒸汽射流冷凝过程具有强烈的凝结换热能力,广泛应用于先进非能动反应堆安全系统中,但该过程会产生强烈的压力振荡现象。为研究蒸汽浸没射流冷凝振荡现象的本质,从基本守恒方程式出发,建立了气泡边界层质量交换模型、气泡控制方程模型、气泡内蒸汽压力计算模型、水池中任意位置处压力计算模型等关键模型,构建了模拟水池中蒸汽气泡冷凝振荡过程的热工水力模型。运用建立的气泡半径和水池内压力的计算模型获取气泡半径和压力随时间变化的规律,并与Chun实验和Fukuda实验的实验数据进行比对,验证了模型的有效性,为后续开展冷凝振荡机理研究打下理论基础。     

高压条件下含有非凝结性气体的水蒸气凝结传热模型研究

研究高压条件下含有非凝结性气体的水蒸气凝结传热过程对于小型堆的安全非常重要。当前对这一物理过程的研究集中于压力较低的工况,高压条件下的研究尚不成熟。本文建立了一种适用于高压条件下含有非凝结性气体的水蒸气自然对流凝结传热理论模型,使用真实气体状态方程求解扩散方程中摩尔浓度梯度和分压梯度之间的关系,取代了前人方法中的理想气体假设。计算结果与已有的实验数据吻合较好,证明本方法可用于小型堆紧凑型安全壳和汽 气稳压器等安全级设备的热工分析。     

基于RELAP5的氦氙流动换热计算模块开发与验证

反应堆热工系统分析程序是开展热工水力计算与安全评价的重要工具。为开发适用于氦氙气冷空间堆的热工系统分析程序,本文在RELAP5/MOD40程序中拓展了氦氙混合气体（He Xe）物性计算模块,添加了适用于He Xe的传热关系式,将拓展后程序计算值与实验值进行对比。结果表明：程序默认的Sutherlands定律用于He Xe物性计算时将引入较大误差;Dittus Bolter公式对He Xe对流换热时的Nu预测偏高,将导致不保守的壁温计算结果。拓展后的程序对He Xe压降和换热计算结果均与实验值吻合较好,验证了程序开发的正确性以及程序用于He Xe流动换热计算的功能。本研究可为系统层面程序开发奠定基础。     

熔融物液柱碎化模型对先进压水堆堆外蒸汽爆炸计算的影响分析

在堆外蒸汽爆炸计算中,液柱碎化模型影响着熔融物液滴生成速率、液滴直径、液滴分布、液滴凝固和气泡比例等粗混合参数和现象,从而影响了蒸汽爆炸的冲击载荷。本文基于MC3D V3.8程序,采用不同的液柱碎化模型（CONST模型和KHF模型）对先进压水堆堆外蒸汽爆炸进行计算分析,探讨了CONST和KHF模型对蒸汽爆炸计算的影响。结果表明,两种模型计算的粗混合状态类似;在熔融物触底时刻,爆炸性准则几乎相同,此时触发爆炸得到的冲击载荷差别很小,表明该时刻触发爆炸时不同液柱碎化模型对爆炸冲击计算的影响较小;在本文所定义的工况下,先进压水堆堆坑墙体承受的最高压力约为20 MPa,最大冲量小于0.2 MPa•s。     

Application of Simplified Condensation Model to PWR LBLOCA Transient Analysis with TRAC-PF1 Code

In the system analyses of a large-break loss-of-coolant accident (LBLOCA) of pressurized water reactors (PWRs), the TRAC-PF1 code predicted an unrealistic depressurization and required much computational time due to the problem of the condensation model. To eliminate the unrealistic depressurization, the TRAC-PF1 code was improved using a simplified condensation model that determined the total condensation rate at cold leg. Through the assessment calculations for CCTF, UPTF and LOFT tests, it was confirmed that the simplified model could eliminate the unrealistic depressurization and reduce the computational time. It was also confirmed that the model could improve the accuracy of the system calculation for the core inlet flow rate and clad temperature as the result of the elimination of the unrealistic depressurization. It has been concluded that the simplified condensation model is useful for the system calculation of the PWR LBLOCA.     

基于RELAP5 MOD3.2的钠冷快堆热工水力系统分析程序开发及验证

对大型核反应堆热工水力分析程序RELAP5 MOD3.2进行了改造,使之适用于钠冷快堆系统安全分析。在不影响原程序功能的基础上添加了气液两相钠物性和液态金属对流换热模型,并改造了相应的初始化模块和计算模块。改造后的程序可正确模拟钠的流体力学特性和热物性,搭建钠冷快堆热工水力流体网络进行分析计算。对EBR-Ⅱ试验堆基准题进行了稳态模拟和失流事故分析,其中稳态计算主要参数与实验值相对偏差小于1%,瞬态计算相对偏差小于10%,各参数变化趋势与实验值相符良好,初步验证了改造程序的可靠性。