中间换热器的传热和阻力特性

中间换热器在高温气冷堆氦气透平间接循环发电系统中是耦合高温气冷堆和氦气透平的关键部件,承担着将高温气冷堆中高温氦气的能量传递到氦气透平回路的任务.中间换热器给氦气透平的设计和运行维护带来方便,但它的传热与阻力性能不可避免地影响循环效率,因此,中间换热器的设计和选型需综合考虑传热效率、压力损失、材料性能和紧凑度等因素.本文介绍了印制板式换热器(PCHE)的主要特点,分析了它在间接循环系统中应用的可行性,重点研究了该中间换热器的传热和流动阻力特性,以及影响PCHE换热效率和压力损失的主要因素.在此基础上,提出了优化中间换热器传热和阻力特性的途径和方法.     

高温堆非纯氦气中预氧化对3种高温合金的腐蚀行为影响研究

高温气冷堆（简称高温堆）中,由于一回路冷却剂氦气中含有微量（ppm级）不纯杂质,其在高温环境中会对高温堆合金材料造成腐蚀,影响设备的性能。Inconel 617、Hastelloy X、Incoloy 800H是3种高温堆中间换热器及蒸汽发生器设备候选材料。研究表明,镍铬合金在高温下表面生成的富铬氧化层是防止合金在高温下发生严重腐蚀的重要因素。本文对3种合金在高温含杂质氦气中的腐蚀行为进行研究,探究预氧化对3种合金腐蚀行为的影响。并通过称重、扫描电镜、X射线能谱、电子探针显微分析仪以及碳硫分析仪对腐蚀结果进行分析。结果表明,3种合金均出现了不同的氧化和渗碳现象,预氧化对Hastelloy X合金抗腐蚀能力的提升不明显,对Inconel 617合金的抗氧化和渗碳能力有一定提升,对Incoloy 800H合金的抗渗碳腐蚀能力有一定提升。     

高温气冷堆闭式布雷顿间接循环中氚的来源及其影响

氚是氢的放射性同位素,影响环境和人体健康.目前,全球自然界中的氚主要来自人类的核活动.因此,需研究核反应堆中氚的来源及其影响.在高温气冷堆中,氚是一回路放射性的主要来源之一.由于高温气冷堆堆芯温度较高,不能忽视一回路中氚向外界和二回路渗透造成的污染问题.文章阐述了氚的物理和化学特性,高温气冷堆闭式布雷顿间接循环中氚的生成来源和释放途径,分析了氚对设备材料力学性能的影响,介绍了氚向环境释放的限值、控制措施及防止氚渗透的方法.     

高温气冷堆冷却剂杂质对高温合金材料高温性能影响的研究模型分析

高温气冷堆一回路冷却剂中含有的少量CO、H_2、H_2O、CH_4等杂质,这些杂质对高温堆蒸汽发生器用高温合金的高温性能有重要影响。国外在超高温运行工况下冷却剂杂质对高温合金材料性能的影响方面开展了大量研究,由于研究过程中对试验氦气中痕量的杂质含量控制十分困难,致使相关的研究成果分布比较分散,需要对相关的研究模型进行归纳和分析。高温镍铬合金中的铬是被氧化的主要合金元素,而保护性Cr_2O_3层的形成是合金是否被腐蚀的主要决定因素;铬的稳定相图模型和气体组成三元相图模型是两种被广泛应用的理论模型。本文对铬的这两种理论模型研究方法及其应用情况进行比较和分析。     

气冷堆氦气净化系统改进设计与分析

为防止高温材料的腐蚀,需要通过氦气净化系统对气冷堆回路中各种气体杂质含量进行控制。本文基于高温氧化铜床、室温分子筛床和深冷活性炭床的氧化以及吸附成熟技术,通过比较分析当前各国已有的典型氦气净化回路设计,提出一项改进设计方案。计算结果表明,在保证系统净化效率的前提下,改进设计不增加系统设备,可以明显地降低系统能耗。对回热器回热度的敏感性分析结果表明,回热器回热度并非越高越好。     

高温气冷堆二回路水质控制方法研究

参考压水堆二回路和火电直流炉水质标准，结合高温气冷堆二回路结构和材料特点，对高温气冷堆蒸汽发生器（SG）原设计中的进水标准和精处理出水标准进行了修正，得出比较合理的水质控制标准；研究了提高高温气冷堆二回路水-汽品质的3种方法，即机组启动冲洗方式控制、加药控制和精处理运行方式控制，对3种方法进行了详细的论述，提出了科学、完整的高温气冷堆二回路水-汽品质优化方法。      

高温和超高温气冷堆动力转换方案研究

动力转换单元是高温和超高温气冷堆的重要组成部分。本文对高温和超高温气冷堆的动力转换单元进行研究。从4个关键参数(反应堆出口温度、反应堆入口温度、压缩比和主蒸汽参数)入手,对5个循环方案进行比较分析。综合考虑各种工程因素,上位循环为简单氦气透平循环、下位循环为有再热的蒸汽轮机循环的联合循环方案是具有竞争力的,其中下位循环在高温气冷堆范围是亚临界参数循环,在超高温气冷堆范围是超临界参数循环。联合循环可实现高温和超高温气冷堆热量的高效率转化,且反应堆入口温度在反应堆压力壳材料允许的范围内,具有足够的安全性。     

Inconel 617合金在非纯氦气环境中的高温腐蚀行为研究

Inconel 617合金是高温气冷堆蒸汽发生器的候选材料,在反应堆超高温运行时可能会受到氦气中痕量杂质的腐蚀。为探究合金在高温堆环境中的腐蚀机理,本研究开展了Inconel 617合金在980℃的非纯氦气中的腐蚀实验,对气相以及腐蚀行为进行了分析。通过化学热力学和动力学计算,阐明了合金脱碳的机理,并建立了碳迁移判定模型和脱碳反应预测模型,与实验数据有良好的一致性。在此基础上,研究了预氧化和温度对脱碳反应的影响。研究结果表明,即使杂质含量极低,也会诱发相关的腐蚀行为。降低运行温度可以有效避免合金脱碳,但预氧化的抗脱碳效果不理想。因此,极低杂质含量并非高温堆一回路净化目标,应该根据模型预测和实验分析来选择更加合理的杂质控制方案。     

高温和超高温气冷堆动力转换方案研究

动力转换单元是高温和超高温气冷堆的重要组成部分。本文对高温和超高温气冷堆的动力转换单元进行研究。从4个关键参数（反应堆出口温度、反应堆入口温度、压缩比和主蒸汽参数）入手，对5个循环方案进行比较分析。综合考虑各种工程因素，上位循环为简单氦气透平循环、下位循环为有再热的蒸汽轮机循环的联合循环方案是具有竞争力的，其中下位循环在高温气冷堆范围是亚临界参数循环，在超高温气冷堆范围是超临界参数循环。联合循环可实现高温和超高温气冷堆热量的高效率转化，且反应堆入口温度在反应堆压力壳材料允许的范围内，具有足够的安全性。     

10MW高温气冷堆一回路氦气品质研究

10MW高温气冷堆以氦气作为冷却剂,氦气中含有H2O、CO2、H2、CO、CH4、N2、O2等7种影响氦气品质的杂质。分析反应堆在不同工况下的氦气品质数据的变化规律,可证明一回路氦气在反应堆功率运行过程中经氦气净化系统净化后,氦气品质能够满足技术规格书要求。但随一回路氦气平均温度的升高,氦气品质呈下降趋势,并可初步判断存在缓慢变化的杂质源项为水。     

Parametric evaluation of large-scale high-temperature electrolysis hydrogen production using different advanced nuclear reactor heat sources

High-temperature electrolysis (HTE), when coupled to an advanced nuclear reactor capable of operating at reactor outlet temperatures of 800-950 °C, has the potential to efficiently produce the large quantities of hydrogen needed to meet future energy and transportation needs. To evaluate the potential benefits of nuclear-driven hydrogen production, the UniSim process analysis software was used to evaluate different reactor concepts coupled to a reference HTE process design concept. The reference HTE concept included an intermediate heat exchanger and intermediate helium loop to separate the reactor primary system from the HTE process loops and additional heat exchangers to transfer reactor heat from the intermediate loop to the HTE process loops. The two process loops consisted of the water/steam loop feeding the cathode side of a HTE electrolysis stack, and the sweep gas loop used to remove oxygen from the anode side. The UniSim model of the process loops included pumps to circulate the working fluids and heat exchangers to recover heat from the oxygen and hydrogen product streams to improve the overall hydrogen production efficiencies.The reference HTE process loop model was coupled to separate UniSim models developed for three different advanced reactor concepts (a high-temperature helium cooled reactor concept and two different supercritical CO₂ reactor concepts). Sensitivity studies were then performed with the objective of evaluating the affect of reactor outlet temperature on the power cycle efficiency and overall hydrogen production efficiency of the integrated plant design for each of the reactor power cycles. The results of these sensitivity studies showed that overall power cycle and hydrogen production efficiencies increased with reactor outlet temperature, but the power cycles producing the highest efficiencies varied depending on the temperature range considered.     

Preliminary issues associated with the next generation nuclear plant intermediate heat exchanger design

The Next Generation Nuclear Plant, with emphasis on production of both electricity and hydrogen, involves helium as the coolant and a closed-cycle gas turbine for power generation with a core outlet/gas turbine inlet temperature of 850-950 °C. In this concept, an intermediate heat exchanger is used to transfer the heat from primary helium from the core to the secondary fluid, which can be helium, a nitrogen/helium mixture, or a molten salt. This paper assesses the issues pertaining to shell-and-tube and compact heat exchangers. A detailed thermal-hydraulic analysis was performed to calculate heat transfer, temperature distribution, and pressure drop inside both printed circuit and shell-and-tube heat exchangers. The analysis included evaluation of the role of key process parameters, geometrical factors in heat exchanger designs, and material properties of structural alloys. Calculations were performed for helium-to-helium, helium-to-helium/nitrogen, and helium-to-salt heat exchangers.     

The He/He heat exchanger — Design and semitechnical testing

This is a report on the development of the He/He heat exchanger which is used for high-temperature reactors (HTR) combined with the steam gasification of coal. A concept has been agreed on the basis of the requirements resulting from the application of the HTR. Subsequently those steps, which are required for the development of this component up to construction maturity are described. Simultaneously, questions dealing with material, construction, design, manufacture and related experimental development are taken into consideration.     

高温气冷堆主氦风机惰转特性研究

高温气冷堆主氦风机与压水堆主泵一样,均为反应堆一回路的关键设备.在反应堆正常工况下,两者具有相同的功能要求,但在事故工况时,因反应堆的运行特性不同,其功能要求各异.目前,对压水堆主泵的惰转特性已有大量的实验研究和实际运行结果,但有关主氦风机惰转特性的实验研究与理论研究还很缺乏.本文结合风机的气动特性与高温气冷堆一回路的阻力特性,从理论上研究高温气冷堆主氦风机的惰转特性,建立主氦风机惰转时的流量与转速的预测公式,并给出其数值预测结果,为高温气冷堆设计的初步安全分析提供依据.     

HTR-10一体化换热装置和联合循环

10MW高温气冷实验堆 (HTR 10 )有两个突出的特点 :(1)采用气体轮机和汽轮机联合循环 ,可以提高其发电效率 ,并且能保持较低的堆芯入口温度 (30 0℃ )。 (2 )中间换热器和蒸汽发生器一体化设计 ,减少了一个壳体和一个热气导管 ,提高了安全性和经济性。描述了一体化的中间换热器和蒸汽发生器以及气体轮机和蒸汽轮机联合循环的设计特点。     

HTR蒸汽发生器环形通道内单液滴蒸发行为研究

高温气冷堆进水事故的机理研究对该反应堆安全具有重要意义。本文对液滴在蒸汽发生器环形通道内的流动和传热进行数值模拟研究,采用单液滴模型,利用龙格库塔方法进行求解。结果表明,初始直径小于420 μm的液滴将无法运动到环形通道顶部。氦气压力的改变对于液滴完全蒸发需要的时间和液滴最大运动距离影响很小。     

高温气冷堆氦气透平直接循环启动参数分析计算

开发了包括堆芯、蒸汽发生器、透平、压气机及换热器等模块在内的高温气冷堆氦气透平直接循环系统的稳态计算程序。对系统的启动过程进行了模拟分析,并对压气机的喘振问题进行了分析,考虑了换热能力、温度和压力的影响。结果表明：在变负荷过程中压气机有足够的安全裕度。     

A specialized code for operation transient analysis and its application in fluoride salt-cooled high-temperature reactors

Fluoride salt-cooled high-temperature reactors (FHRs) include many attractive features,such as high temperature,large heat capacity,low pressure and strong inherent safety.Transient characteristics of FHR are particularly important for evaluating its operation performance.Thus,a specialized code OCFHR (operation and control analysis code of FHR) issued to study an experimental FHR's operation behaviors.The geometric modeling of OCFHR is based on one-dimensional lumped parameter method,and some simplifications are taken into consideration during simulation due to the existence of complex structures such as pebble bed,intermediate heat exchanger (IHX),air radiator (AR) and multiply channels.A point neutron kinetics model is developed,and neutron physics calculation is needed to provide some key inputs including axial power density distribution,reactivity coefficients and parameters about delayed neutron precursors.For analyzing the operational performance,five disturbed transients are simulated,involving reactivity step insertion,variations of coolant mass flow rate of primary loop and intermediate loop,adjustment of air inlet temperature and mass flow rate of air cooling system.Simulation results indicate that inherent self-stability of FHR restrains severe consequences under above transients,and some dynamic features are observed,such as large negative temperature feedbacks,remarkable thermal inertia and high response delay.