Calculation Method of Passive Residual Heat Removal Heat Exchanger and Numerical Simulation

The tube inside and outside heat transfer mechanism of Passive Residual Heat Removal Heat Exchanger (PRHR HX) was analyzed. The calculation method of this special heat exchanger under natural convection condition in In-containment Refueling Water Storage Tank (IRWST) was carried out. The single-tube coupling model three-dimensional natural circulation in the IRWST was simulated numerically using Fluent. The heat transfer and flow characteristics of the fluid in IRWST were obtained. The comparison of the results between theoretical arithmetic and numerical simulation showed that the theoretical calculation method is suitable for the heat transfer calculation of PRHR HX.

Application of grey model on analyzing the passive natural circulation residual heat removal system of HTR-10

Using the grey correlation analysis,it can be concluded that the reactor pressure vessel wall temperature has the strongest effect on the passive residual heat removal system in HTR (High Temperature gas-cooled Reactor), the chimney height takes the second place,and the influence of inlet air temperature of the chimney is the least.This conclusion is the same as that analyzed by the traditional method.According to the grey model theory,the GM(1,1) and GM(1,3) model are built based on the inlet air temperature of chimney,pressure vessel temperature and the chimney height.Then the effect of three factors on the heat removal power is studied in this paper.The model plays an important role on data prediction,and is a new method for studying the heat removal power.The method can provide a new theoretical analysis to the passive residual heat removal system of HTR.

The development and verification of thermal-hydraulic code on passive residual heat removal system of Chinese advanced PWR

The technology of passive safety is the current trend among safety systems in nuclear power plant. Pas- sive residual heat removal system (PRHRS), a major part of passive safety systems of Chinese advanced PWR, is a novel design with three-fold natural circulation. On the basis of reasonable physics and mathematics models, MI- TAP-PRHRS code was developed to analyze steady and transient characteristics of the PRHRS. The calculation and analysis show that the code simulates steady characteristics of the PRHRS very well, and it is able to simulate tran- sient characteristics of all startup modes of the PRHRS. However, the quantitative description is poor during the ini- tial stages of the transition process when water hammer occurs.

Survey of experiments and code development for the passive residual heat removal system of PWR in China

Three different kinds of experiments and their typical results are surveyed for the passive residual heat removal system (PRHRS) of PWR performed in Nuclear Power Institute of China (NPIC) recent ten years. The typi- cal results of MISAP, a special code for PWR passive residual heat removal system developed and assessed by NPIC, are also described briefly in this paper.

Steady characteristic investigation on passive residual heat removal system of Chinese advanced PWR

Thermal-hydraulic characteristic investigation on passive residual heat removal system (PRHRS) of Chinese advanced PWR was conducted to provide input data for PRHRS design and to demonstrate the feasibility of unique design features. A total of 237 sets of test data at steady state have been obtained and the main influence factors on the two-phase natural circulation flow rate and residual heat removal capability were identified. On the basis of theory analysis, a correlation of two-phase natural circulation was obtained, and relative errors of 95% test data were less than ±16%. There is a considerable effect of the system status parameters on the threshold of height between heat source and heat sink, and its correlation of two-phase natural circulation system has been obtained. The steady characteristic research shows that PRHRS has the capability of removing the core decay power through natural circulation.

Analysis of the Presence of Vapor in Residual Heat Removal System in Modes 314 Loss-of-Coolant Accident Conditions Using RELAP5

The Westinghouse Nuclear Safety Advisory Letter NSAL-09-8 investigated the possibility of presence of vapor in RHR （residual heat removal） system in modes 3/4 LOCA （loss-of-coolant accident） conditions. This concerns the Westinghouse standard three-loops plant for which the RHR is the low pressure part of the St （safety injection）. In some cases one or both RHR trains may become inoperable for SI function. As a response to this letter, Westinghouse Electric Belgium is providing RELAP5 analyzes for Westinghouse NSSS （nuclear steam supply system） European plants to assess the thermal hydraulic behavior of the RHR suction piping system for ECCS （emergency core cooling system） initiation events postulated to occur during startup/shutdown operations. Several concerns including condensation induced water hammer and voiding at the RHR pump have been investigated. As a conclusion, the analysis allowed to define the bounding hot leg temperature conditions under which both RHR trains remain safely operable. These bounding conditions are then implemented by the customer in their OPs （operating procedures） to achieve safe operations and successful accident management.

Current situation and development of solar heating technology in China

It is introduced the current situation and development for solar heating technology including passive solar heating and solar heating combisystems in China in this paper. Combined with the engineering application projects, the author gave the technical and economic analysis of the passive solar and solar heating combisystems in China and summarized the developing obstacle and the spreading tactics for raising marketing of the solar heating in China.

Experimental study of primary and secondary side coupling natural convection heat transfer characteristics of the passive residual heat removal system in AP1000

Passive residual heat removal heat exchanger(PRHR HX),which is a newly designed equipment in the advanced reactors of AP1000 and CAP1400,plays an important role in critical accidental conditions.The primary and secondary side coupling heat transfer characteristics of the passive residual heat removal system(PRHRS)determine the capacity to remove core decay heat during the accidents.Therefore,it is necessary to investigate the heat transfer characteristics and develop applicable heat transfer formulas for optimized design.In the present paper,an overall scaled-down natural circulation loop of PRHRS in AP1000,which comprises a scaleddown in-containment refueling water storage tank(IRWST)and PRHR HX models and a simulator of the reactor core,is built to simulate the natural circulation process in residual heat removal accidents.A series of experiments are conducted to study thermal-hydraulic behaviors in both sides of the miniaturized PRHR HX which is simulated by 12 symmetric arranged C-shape tubes.For the local PRHR HX heat transfer performance,traditional natural convection correlations for both the horizontal and vertical bundles are compared with the experimental data to validate their applicability for the specific heat transfer condition.Moreover,the revised natural convection heat transfer correlations based on the present experimental data are developed for PRHR HX vertical and lower horizontal bundles.This paper provides essential references for the PRHRS operation and further optimized design.

国和一号关键核安全技术研发

基于当前各类能源技术基础和核电技术发展水平判断,核能是社会清洁低碳转型与可持续发展的重要支撑,高安全高可靠性的大型先进压水堆核电机组是未来30年内的主力机型。本文围绕大型先进压水堆核电站国家科技重大专项所面临的重大挑战,主要阐述了通过解决“高功率核燃料冷却难”“超高温熔融物滞留难”和“高温高压高放射性包容难”三大关键技术难题,来保证从设计上消除大规模放射性释放可能性或进一步降低核电批量化建设的核安全风险。

基于“一维系统+三维CFD”耦合方法的快堆非能动余热排出系统自然循环特性的数值模拟

池式快堆采用了新型非能动堆内直接余热排出(DRACS)方式,提升了快堆的安全性。目前针对池式快堆自然循环开展的数值模拟研究中,系统程序难以准确预测池内复杂自然循环路径,难以准确模拟池内三维热工水力现象,如果采用三维CFD计算建模及网格划分难度较高,且所需计算资源较大。为此本文开发了“一维系统+三维CFD”耦合方法,用于快堆非能动余热排出系统自然循环特性计算分析。利用日本大型钠回路实验台架(PLANDTL)DRACS自然循环模式对该耦合方法进行验证,稳态工况关键位置参数相对误差小于3%,瞬态工况关键位置参数与实验值变化趋势吻合较好,相对误差小于10%,验证了该耦合方法的适用性和准确性。利用该耦合方法,开展了中国实验快堆(CEFR)自然循环及余热排出特性计算分析,识别了池内自然循环流动路径,揭示了池内温度分层以及盒间流现象。本文方法可为大型钠冷快堆自然循环三维瞬态特性分析提供重要数值方法。

新型分散型抗垢剂在S Zorb装置的工业应用

中国石化广州分公司S Zorb装置为有效抑制原料侧换热器E-7101A-G因高温结垢而导致的换热器传热效率下降、换热器总压差上涨过快等影响装置长周期运行问题,决定使用浙江杭化科技股份有限公司生产的新型分散型抗垢剂HK-17DC。工业应用结果表明,HK-17DC在线除垢及阻垢作用良好,且使用HK-17DC对装置运行和产品质量无不良影响。

小型堆二次侧非能动余热排出系统特性计算分析

为提高反应堆安全性,基于自然循环的非能动余热排出系统在小型反应堆中有着广泛的应用。本文基于已完成的小型一体化核动力装置中间回路换热实验,用RELAP5(Reactor Excursion and Leak Analysis Program)对中间回路自然循环运行特性开展了计算分析工作。研究发现,载热功率的程序计算结果与实验数据符合良好,可表征系统的自然循环特性。在余热排出系统中,系统回路的压力由蒸汽发生器(Steam Generator,SG)一次侧平均温度所决定,SG一次侧入口温度、质量流量与冷热源高度差对余热排出系统换热性能影响显著。当SG一次侧入口温度较高时,余热排出系统换热性能对系统回路阻力更加敏感,这些结果为进一步研究小型堆非能动系统提供了有价值的应用。

绕丝棒束组件过渡流摩擦阻力实验研究

绕丝棒束组件低流速下摩擦阻力是钠冷快堆堆芯热工水力研究的重点内容之一。通过对现有组件摩擦阻力系数公式应用于过渡流存在的问题、现有组件摩擦阻力实验在低流速时出现的不同摩擦阻力特性的分析讨论,以及对一个37棒组件低流速摩擦阻力的实验研究,提出了组件内流动的转捩特性和提高经验公式在低流速时计算准确性的有效策略。研究结果表明:绕丝棒束组件内流动转捩并不是同时发生,而是在部分子通道的局部先发生,随着流速的增加扩散到整个组件,只有当一定数量子通道都发生转捩时,棒束的平均摩擦阻力才会显著增加。绕丝棒束组件摩擦阻力系数公式应尽可能使用小的层流向过渡流转捩的临界Re和插值指数,使公式尽早开始转捩,并平滑向过渡流过渡。

烟气凝变过程中SO_(3)酸雾凝结长大与脱除特性模拟研究

烟气冷凝技术能够回收湿烟气中的废水和余热,同时降低SO_(3)酸雾排放量。该文通过建立烟气冷凝、颗粒运动及颗粒凝结长大模型,对烟气凝变过程中SO_(3)酸雾的凝结长大和脱除特性进行研究,分析关键影响因素,并讨论了酸雾长大和脱除机理。结果表明:SO_(3)酸雾经过凝结长大后在换热器出口粒径呈双峰分布,最高数量浓度在微米范围;亚微米粒径的酸雾捕集机理以热泳和扩散泳为主,提高入口烟气温度和相对湿度,降低壁面温度和入口烟气流速都有利于酸雾粒径的增长和脱除。微米粒径的酸雾捕集机理以惯性碰撞和拦截为主,提高烟气流速有助于微米粒径酸雾的脱除。

新型兆瓦级紧凑核动力装置的非能动余热排出系统设计分析

热管堆具有结构简单、布局紧凑、固有安全性高的特点,是无人潜航器的理想堆型之一。针对采用热管堆的新型兆瓦级高效紧凑核动力装置,设计了一种利用自然循环冷却热管绝热段的非能动余热排出系统。使用计算流体力学方法对不同几何参数的余排系统的排热能力进行模拟分析,使其保守满足最大余排功率的需求。结果表明:热管管束周围设计围板导流有利于降低流体最高温度,围板进出口宽度几乎不影响换热能力,而延长围板下部不利于自然循环;3.5兆瓦热管堆的应急冷却舱轴向长度为160 mm时可以保守满足最大余排功率,并在5~25℃的环境温度下均可正常工作。

基于MBSE的铅冷快堆非能动余热排出系统设计需求分析

针对传统的铅冷快堆非能动余热排出系统设计中存在开发效率低、迭代周期长、模型二义性等前期需求问题,本研究将基于模型的系统工程(Model-based System Engineering,MBSE)方法应用于铅冷快堆非能动余热排出系统设计需求中,结合设计流程进行系统架构的初步设计,该系统架构由需求分析、功能分析和设计综合三部分组成。结果表明:需求分析阶段生成的需求图和用例图可捕获系统需求并确定系统顶层用例;功能分析阶段绘制的时序图、活动图和状态机图可形成系统功能模型并提供早期确认与验证;设计综合阶段建立的白盒模型最终实现系统架构的分析与设计。采用该方法设计的系统架构可确保前后设计需求一致性,进一步降低设计风险并提高设计效率,可为数字化铅冷快堆非能动余热排出系统设计与优化提供应用参考。

渣油加氢装置高压换热器内漏分析及建议

渣油加氢装置在运行过程中发现热低压分离器油存在硫含量异常上升、加氢渣油产品质量不合格的问题,通过杂质脱除率分析、加热炉取热分析和傅里叶变换离子回旋共振质谱分析,判断为高压换热器内漏,估算运行至末期时内漏量已将近15%。停工后对换热器进行了水压试压,判断内漏原因为顶压螺栓预紧力偏小,在运行初期反应器的压降较小时换热器正常运行,随着运行时间延长换热器管壳程之间的压降增大,壳程的压力超过了金属包覆垫的回弹力,换热器的管壳程密封处渗漏,杂质含量较高的混氢原料油直接泄漏至加氢产品中,导致产品的杂质含量不断上升。建议采用金属齿形垫加钢环的结构替代目前使用的金属包覆垫,并重新核算换热器的预紧力,确保高压换热器长期高效运行。

热输入量对换热器管板焊接接头缺陷及残余应力的影响

文章通过改变焊接的电流和电压,研究热输入量(2.16 kJ/mm,2.52 kJ/mm,2.88 kJ/mm)对换热器管板焊接接头缺陷的影响。基于有限元算法,研究热输入量对换热器管板焊接接头处残余应力的影响,进一步改进焊接工艺。结果表明,与热输入量为2.16 kJ/mm和2.88 kJ/mm相比,在热输入量为2.52 kJ/mm时,管板焊接接头的焊接质量最佳,具有焊缝成形好,无裂纹及少量可接受的焊接缺陷。通过对多管-板焊接接头的残余应力计算发现,中心换热管处热影响区残余应力较大。而且残余应力并不是随着热输入的增加而增加。与热输入量为2.16 kJ/mm和2.88 kJ/mm相比,当热输入量为2.52 kJ/mm时,管板接头处的残余应力分布最均匀且稳定,表明焊接质量最佳,这与实验结果一致。最后,通过增加焊间冷却时间和改变焊接顺序来改进焊接工艺,解决了局部残余应力分布集中的问题,改进了焊接接头质量。

PCS内部换热器外低浓度氢气燃烧及其影响分析

为研究严重事故条件下对华龙一号非能动安全壳冷却系统(PCS)内部换热器的影响,以华龙一号PCS内部换热器为研究对象,使用商业流体计算软件ANSYS对低浓度氢气燃烧工况及其影响进行了分析。利用西安交通大学的圆柱形实验作为验证实验,证明了选用燃烧模型的正确。选取经验证的氢气燃烧模型对氢气浓度为8%、10%、12%分别进行分析,得到PCS内部换热器换热管表面的最高温度及最大压力分别为676 K与1.95 MPa,并利用得到的温度、压力载荷对PCS内部换热器进行应力分析,按照ASME规范第Ⅲ卷第1分卷NC分册、第1分篇附录进行应力评定校核,结果表明应力水平满足标准的要求。本文研究结果表明,在严重事故下安全壳内浓度为12%的氢气燃烧后不影响PCS内部换热器的安全使用。

基于不同功率的非能动安全壳热量导出系统实验研究

“华龙一号”非能动安全壳热量导出系统(passive containment heat removal system,PCS)和“玲龙一号”非能动安全壳热量导出系统设计原理相同,但系统功能和设计准则不尽相同。为了掌握影响系统换热能力和运行的关键因素,本文结合不同项目的特点,从综合性能实验需求和实验结果等方面,研究、分析“华龙一号”非能动安全壳热量导出系统与“玲龙一号”非能动安全壳热量导出系统设计中的典型现象,发现降低冷却水箱水位可以提升系统的换热能力、改变冷管段阻力对系统的换热能力更敏感和冷管段隔离阀关闭方案在开启时可能会有一定的风险,从而提出后续优化研究和设计中需要重点关注的影响因素。文中结论可用于指导相关系统设计工作。