低温堆上空腔破口失水后期的流动振荡实验研究

在５ＭＷ低温堆的模拟试验台架ＨＴＲＬ－５上对该低温堆上空腔破口失水事故进行了实验研究。重点研究了事故后期的流动振荡现象，揭示了振荡的发展过程和发生机理。经实验研究，给出了小破口失水闪蒸过程中回路内压力、温度、空泡份额、循环流量等重要参数的变化规律，同时表明了小破口失水过程中由于压力下降引起闪蒸产生大量气泡并引起自然循环流量的变化，这些变化又反过来对各参数产生影响，使循环流量的传热情况发生周期性变化     

船用核动力装置小破口失水事故放射性后果分析

建立了小破口失水事故下热工水力分析与放射性源项计算耦合模型,利用研发的反应堆源项放射性计算软件(Nuclear source radioactive compute,NSRC),分别就不同破口尺寸的堆舱放射性泄漏进行了分析和研究,进一步研究了小破口失水事故,冷端安注和热端安注对堆舱放射性影响。结果表明:破口尺寸大小、安全注射位置及破口隔离时间直接影响堆舱放射性泄漏大小。本工作的分析结果为小型船用堆在小破口设计基准事故下,放射性污染后果分析及事故处置提供了依据。     

自然循环回路失水闪蒸时的流动和传热试验研究

研究是在５ＭＷ核供热反应堆的模拟试验台架ＨＴＲＬ－５完成的，经研究，给出了小破口失水闪蒸过程中回路内压力，温度、空泡份额、循环流量等重要参数的变化规律，揭示了闪蒸过程的两个阶段，给出了换热系数的实验结果，结果表明小破口失水过程由于闪蒸改善了自然循环和传热情况，使无件棒温度保持在较低水平，不会烧毁。     

铅铋循环回路小破口事故计算模型研究

铅铋循环回路小破口事故对加速器驱动次临界洁净核能系统(ADS)的安全有重要影响。通过建立一个铅铋循环回路小事故模型,计算分析未破口和小破口以后的铅铋循环回路参数。计算表明:小破口事故相比未破口回路压力下降梯度变大,流量迅速丧失;破口瞬态流量陡降至与进口平衡;破口与管壁压力都会随时间下降直到平衡。     

ACME台架PRHR管线破口位置敏感性试验研究

为研究先进非能动（AP）型核电厂在非能动系统失效条件下的安全性能,利用我国先进堆芯冷却机理整体试验台架（ACME）开展了非能动余热排出（PRHR）管线破口失水试验研究,分析了主要的试验进程和破口位置对事故过程各阶段关键参数的影响。结果表明,ACME PRHR管线破口试验进程与冷管段小破口失水事故（SBLOCA）进程基本一致,再现了非能动核电厂自然循环阶段、自动卸压系统（ADS）喷放阶段和安全壳内置换料水箱（IRWST）安注阶段的安全特性;在不同破口位置的试验中,非能动堆芯冷却系统（PXS）均可保证堆芯得到补水,堆芯活性区始终处于混合液位以下;破口位置对ACME LOCA事故进程、反应堆冷却剂系统（RCS）初期降压速率、PRHR热交换器（HX）流量、喷放流量、堆芯液位、IRWST安注流量等参数具有显著影响,对堆芯补水箱（CMT）和蓄压安注箱（ACC）安注流量的影响较小。      

实验快堆自然循环模拟实验装置的模拟原理及其参数计算

研究了池式快堆自然循环模拟实验的模拟准则，根据模拟准则和自然循环守衡方程式，对池式实验快堆自然循环模拟实验装置，在各种模拟准则条件下的几何与热工设计参数进行了计算。研究了模型比例，事故冷却器一次侧进出口温差和阻力系数等对相似准则数的影响，并且确定了模拟实验装置的设计参数范围，从理论上解决了池式实验快堆自然循环模拟实验装置的模拟问题。     

大破口失水事故重要模型不确定性评价及应用

在对大破口失水事故进程和物理现象进行深入剖析的基础上,确定了事故中对包壳峰值温度有重要影响的现象及对应的RELAP5/MOD3.3流动传热模型：临界热流密度模型、膜态沸腾传热模型和临界流模型。通过文献调研获得了对应流动传热模型的实验数据。将模型计算值和实验数据进行对比,对这3个模型的不确定性进行评价,并应用正交序列法得到模型不确定范围和概率分布。最后将概率评价结果应用于LOFT LP-02-6大破口失水事故的不确定性分析中,分析结果表明,对RELAP5流动传热模型的概率评价合理。     

小型动力堆码头中破口失水事故大气扩散研究

采用高斯分段烟羽模型估算了某小型动力堆在码头内发生破口尺寸为29.4%当量直径的设计基准事故时,放射性核素在码头20 km区域范围内的大气扩散规律。源项采用严重事故计算程序MELCOR仿真获得,并将计算结果输入到大气扩散分析软件MACCS进行分析计算。计算结果表明：中破口失水事故会造成码头区域的放射性污染,风速越小、气象条件越稳定,放射性的影响范围越大。     

XAPR中破口失水事故下堆芯自然循环冷却能力的功能可靠性研究

功能失效是导致自然循环系统运行失效的重要因素,需在其可靠性分析中予以考虑。针对多维不确定性参数及小功能失效概率问题,提出了一种将改进响应面法及重要抽样子集模拟法相结合的功能可靠性分析方法。以西安脉冲堆(XAPR)堆池水自然循环冷却为例,结合中破口失水事故,考虑输入参数及模型的不确定性,对其进行了功能可靠性评估和灵敏度分析。结果表明:XAPR堆芯自然循环功能失效概率为3.796×10~(-3),需充分考虑系统功能的可靠性。本文方法具有较高的计算效率,同时又能保证很高的计算精度,对XAPR堆芯自然循环非线性功能函数具有很强的适应性。     

XAPR中破口失水事故下堆芯自然循环冷却能力的功能可靠性研究

功能失效是导致自然循环系统运行失效的重要因素，需在其可靠性分析中予以考虑。针对多维不确定性参数及小功能失效概率问题，提出了一种将改进响应面法及重要抽样子集模拟法相结合的功能可靠性分析方法。以西安脉冲堆（XAPR）堆池水自然循环冷却为例，结合中破口失水事故，考虑输入参数及模型的不确定性，对其进行了功能可靠性评估和灵敏度分析。结果表明：XAPR堆芯自然循环功能失效概率为3.796×10^-3，需充分考虑系统功能的可靠性。本文方法具有较高的计算效率，同时又能保证很高的计算精度，对XAPR堆芯自然循环非线性功能函数具有很强的适应性。     

基于CFD方法的非能动余热排出系统数值模拟

本文应用FLUENT软件对APl000的非能动余热排出热交换器和换料水箱进行了数值模拟，分析了不同c型传热管数量和冷却剂入口温度对热交换器换热性能和换料水箱内热分层、自然循环现象的影响。分析表明，总体通流面积不变，随着传热管数量增加，热交换器出口温度变小，水箱水温整体提升，热分层现象显著，自然循环趋势明显；质量流量不变，随着冷却剂入口温度的增加，入口流速增加，热交换器出口温度变大，但降温幅度也变大，水箱平均水温升高，热分层范围扩大，自然循环流速加快。     

快堆主容器内氩气空间传热实验原理及分析

本文研究了池式快堆主容器内氩气空间模拟实验的模拟准则及原理.根据模拟准则和对流换热方程组,研究了模拟实验装置需满足的物理相似和边界相似的条件,并对氩气空间的换热状况进行了计算,确定了实验装置的设计参数范围,从理论上解决了池式实验快堆钠池覆盖气体--氩气空间模拟实验装置的模拟问题.     

多重耦合自然循环载热系统瞬态特性及其热工水力解耦

多重耦合自然循环载热系统热工水力具有流动换热耦合和回路间耦合的特点,本文采用理论分析结合数值计算的方法对自然循环的建立时间、流动方向及多重耦合自然循环系统的热工水力解耦等问题进行了研究。提出了自然循环载热系统瞬态流动的理论模型,该模型能预测自然循环建立时间、流动衰减等现象,模型计算结果与数值计算结果吻合。初始流速为零的自然循环流动方向与系统的加热及冷却设备布置位置有关,垂直布置换热面使系统具有固有循环流动方向。具有初始流速的自然循环系统,即使换热面垂直布置,初始反向流速超过临界流速后也可使自然循环系统流动方向发生翻转,从而使系统在与固有循环流动方向相反的方向运行。提出了多重耦合自然循环载热系统热工水力的简单解耦计算方法,能快速对多重耦合自然循环载热系统热工水力进行分析计算,理论分析和计算结果均表明,以水为工质的自然循环回路载热能力近似与冷热源温差的1.5次方呈正比。     

A new method to derive one set of scaling criteria for reactor natural circulation at single and two-phase conditions

Natural circulation is one of the most important thermal-hydraulic phenomena that makes the fluid flow along a closed loop without any external driving force. With this merit, it is adopted by the passive heat removal system to bring the residual heat out of the core at accidents, and by the primary system of some new conceptual reactors instead of pumps to drive the coolant in the loop at operation. To investigate the reactor natural circulation and verify system thermal-hydraulic codes, it is a way to construct an integrated effect test facility and perform experiments on it with the scaling criteria. With one-dimensional assumption, the natural circulation system was simplified as the heat source, heat sink and pipes, and described by two groups of equations independently for the single-phase and two-phase flow conditions. Based on these equations, a set of non-dimensional equations were derived and the criteria were obtained both applicable for single-phase and two-phase natural circulation. According to these criteria, the practical application was analyzed and discussed. In the paper, the property similarity was strongly suggested in most cases. Though equal height simulation was widely used in the past, the reduced height simulation is a good way to reproduce three-dimensional (3D) phenomena that are of concern in the investigation. The CHF simulation is not suggested. The mass of metal and its distribution is of concern instead of heat transfer at transient simulation.     

反应堆失流事故下堆芯自然循环冷却能力的模拟实验研究

为分析不同热工参数对强迫循环向自然循环过渡过程及稳定自然循环阶段传热及流动特性的影响,在内径为6 mm的竖直实验段内开展实验,研究不同入口过冷度、热流密度及初始流量对强迫循环向自然循环过渡过程以及稳定自然循环过程的影响。实验结果表明：入口过冷度及热流密度对自然循环向强迫循环过渡过程及稳定自然循环过程的换热能力有明显影响,而初始流量对该过渡过程及稳定自然循环的换热能力的影响并不显著。     

非能动安全壳冷却系统空气流道自然循环的比例分析与设计

在考虑建设试验台架经济性的前提下,缩小比例的单项和整体效应试验台架对研究和开发大型先进压水堆核电站及其分析验证程序都具有重要意义。非能动安全壳冷却系统（PCS）壳外空气流道内的自然循环在安全壳非能动冷却性能中发挥着重要的作用。本文从自然循环的数学模型出发,推导出了单项和整体效应试验台架的比例设计方法。在给定壳内热流密度的条件下,通过PCCSAP-3D程序对CAP1400非能动安全壳的2/5比例单项效应试验理想比例台架（ISF）进行模拟。结果表明,本比例分析与设计方法以及在降低高度台架上模拟自然循环是可行的。     

自然循环铅基快堆一回路系统驱动力的关键影响因素研究

为深入研究影响自然循环铅基快堆一回路系统驱动力的关键因素,以自然循环铅基快堆SNCLFR-10为研究对象构建描述反应堆一回路自然循环稳态运行模型;从理论上量化分析冷/热池的热量传递、热源和热阱温度非线性分布、反应堆压力容器壁散热3种因素对自然循环能力的影响,并开展了相关数值模拟验证。结果表明,数值模拟结果与本研究理论计算值吻合较好;3种自然循环能力影响机制耦合作用将降低SNCLFR-10系统自然循环能力,导致自然循环流量与功率之间不再满足理论所得的1/3次方关系。      

Two-phase instability analysis in natural circulation loops of China advanced research reactor

In this paper, two-phase flow instability in natural circulation loops of China Advanced Research Reactor (CARR) has been investigated. CARR is a low pressure and low power density research reactor. A natural circulation instability analysis model is developed for the natural circulation loop of CARR. The homogeneous flow model is used to establish the system control equations. The non-uniform heating and subcooled boiling heat transfer is included. The accumulation heat of the wall is also included. Numerical method of Gear is employed to solve the system equations documented in terms of ordinary differential equations. According to the calculation results, stability maps of the natural circulation loop, which confirm the presence of an instability region under the conditions of low equilibrium quality in the outlet and low pressure, are obtained. It is a special kind of density wave oscillation (DWO) that occurs in very low equilibrium quality region with the characteristics of geysering and ‘Type-I’ DWO at the same time. The calculation results show such oscillation course clearly. The variations of the mass flow rate, the pressure drop and the boiling boundary are analyzed separately. Especially, the phase-space trajectory of the boiling boundary and the mass flow rate is discussed. Finally the oscillation frequency is discussed. The calculated results have important significance for the safety operation and accidental analysis of CARR.     

Scaling laws for thermal-hydraulic system under single phase and two-phase natural circulation

Scaling criteria for a natural circulation loop under single phase and two-phase flow conditions have been derived. For a single phase case the continuity, integral momentum, and energy equations in one-dimensional area average forms have been used. From this, the geometrical similarity groups, friction number, Richardson number, characteristic time constant ratio, Biot number, and heat source number are obtained. The Biot number involves the heat transfer coefficient which may cause some difficulties in simulating the turbulent flow regime. For a two-phase flow case, the similarity groups obtained from a perturbation analysis based on the one-dimensional drift-flux model have been used. The physical significance of the phase change number, subcooling number, drift-flux number, friction number are discussed and conditions imposed by these groups are evaluated. In the two-phase flow case, the critical heat flux is one of the most important transients which should be simulated in a scale model. The above results are applied to the LOFT facility in case of a natural circulation simulation. Some preliminary conclusions on the feasibility of the facility have been obtained.     

Thermal hydraulic calculation in a passive residual heat removal system of the SMART-P plant for forced and natural convection conditions

An investigation of the thermal hydraulic characteristics in the passive residual heat removal system of the System integrated Modular Advanced ReacTor-P (SMART-P) has been carried out using the MARS code, which is a best estimate system analysis code. The SMART-P is designed to cool the system during accidental conditions by a natural convection. The dominant heat transfer in the steam generator is a boiling mode under a forced convection condition, and it is a single-phase liquid and a boiling heat transfer under a natural convection condition. Most of the heat is removed in the heat exchanger of the passive residual heat removal system by a condensation heat transfer. The passive residual heat removal system can remove the energy from the primary side as long as the heat exchanger is submerged in the refueling water tank. The mass flow is stable under a natural circulation condition though it oscillates periodically with a small amplitude. The parameter study is performed by considering the effects of an effective height between the steam generator and the heat exchanger, a hydraulic resistance, an initial pressure, a non-condensable gas fraction in the compensating tank, and a valve actuation time, which are useful for the design of the passive residual heat removal system. The mass flow in the passive residual heat removal system has been affected by the height between the steam generator and the heat exchanger, and the hydraulic resistance of the loop.