Dynamic simulation analysis of molten salt reactor-coupled air-steam combined cycle power generation system

A nonlinear dynamic simulation model based on coordinated control of speed and flow rate for the molten salt reactor and combined cycle systems is proposed here to ensure the coordination and stability between the molten salt reactor and power system.This model considers the impact of thermal properties of fluid variation on accuracy and has been validated with Simulink.This study reveals the capability of the control system to compensate for anomalous situations and maintain shaft stability in the event of perturbations occurring in high-temperature molten salt tank outlet parameters.Meanwhile,the control system’s impact on the system’s dynamic characteristics under molten salt disturbance is also analyzed.The results reveal that after the disturbance occurs,the controlled system benefits from the action of the control,and the overshoot and disturbance amplitude are positively correlated,while the system power and frequency eventually return to the initial values.This simulation model provides a basis for utilizing molten salt reactors for power generation and maintaining grid stability.

Core and blanket thermal-hydraulic analysis of a molten salt fast reactor based on coupling of OpenMC and OpenFOAM

In the core of a molten salt fast reactor(MSFR),heavy metal fuel and fission products can be dissolved in a molten fluoride salt to form a eutectic mixture that acts as both fuel and coolant.Fission energy is released from the fuel salt and transferred to the second loop by fuel salt circulation.Therefore,the MSFR is characterized by strong interaction between the neutronics and the thermal hydraulics.Moreover,recirculation flow occurs,and nuclear heat is accumulated near the fertile blanket,which significantly affects both the flow and the temperature fields in the core.In this work,to further optimize the conceptual geometric design of the MSFR,three geometries of the core and fertile blanket are proposed,and the thermal-hydraulic characteristics,including the three-dimensional flow and temperature fields of the fuel and fertile salts,are simulated and analyzed using a coupling scheme between the open source codes OpenMC and OpenFOAM.The numerical results indicate that a flatter core temperature distribution can be obtained and the hot spot and flow stagnation zones that appear in the upper and lower parts of the core center near the reflector can be eliminated by curving both the top and bottom walls of the core.Moreover,eight cooling loops with a total flow rate of0.0555 m3 s-1 ensur an acceptable temperature distribusure an acceptable temperature distribution in the fertile blanket.

Simulation of radiation dose distribution and thermal analysis for the bulk shielding of an optimized molten salt reactor

The Chinese Academy of Science has launched a thorium-based molten-salt reactor(TMSR)research project with a mission to research and develop a fission energy system of the fourth generation.The TMSR project intends to construct a liquid fuel molten-salt reactor(TMSR-LF),which uses fluoride salt as both the fuel and coolant,and a solid fuel molten-salt reactor(TMSR-SF),which uses fluoride salt as coolant and TRISO fuel.An optimized 2 MWth TMSR-LF has been designed to solve major technological challenges in the Th-U fuel cycle.Preliminary conceptual shielding design has also been performed to develop bulk shielding.In this study,the radiation dose and temperature distribution of the shielding bulk due to the core were simulated and analyzed by performing Monte Carlo simulations and computational fluid dynamics(CFD)analysis.The MCNP calculated dose rate and neutron and gamma spectra indicate that the total dose rate due to the core at the external surface of the concrete wall was 1.91μSv/h in the radial direction,1.16μSv/h above and 1.33μSv/h below the bulk shielding.All the radiation dose rates due to the core were below the design criteria.Thermal analysis results show that the temperature at the outermost surface of the bulk shielding was 333.86 K,which was below the required limit value.The results indicate that the designed bulk shielding satisfies the radiation shielding requirements for the 2 MWth TMSR-LF.

Steady thermal hydraulic analysis for a molten salt reactor

The Molten Salt Reactor (MSR) can meet the demand of transmutation and breeding. In this study, theoretical calculation of steady thermal hydraulic characteristics of a graphite-moderated channel type MSR is conducted. The DRAGON code is adopted to calculate the axial and radial power factor firstly. The flow and heat transfer model in the fuel salt and graphite are developed on basis of the fundamental mass, momentum and energy equations. The results show the detailed flow distribution in the core, and the temperature profiles of the fuel salt, inner and outer wall in the nine typical elements along the axial flow direction are also obtained.

Development of a dynamics model for graphite-moderated channel-type molten salt reactor

A molten salt reactor(MSR) is one of the six advanced reactor concepts selected by the generation Ⅳ international forum because of its advantages of inherent safety, and the promising capabilities of Th-U breeding and transuranics transmutation. A dynamics model for the channel-type MSR is developed in this work based on a three-dimensional thermal–hydraulic model(3DTH) and a point reactor model. The 3DTH couples a three-dimensional heat conduction model and a one-dimensional single-phase flow model that can accurately consider the heat conduction between different assemblies. The 3DTH is validated by the RELAP5 code in terms of the temperature and mass flow distribution calculation. A point reactor model considering the drift of delayed neutron precursors is adopted in the dynamics model. To verify the dynamics model, three experiments from the molten salt reactor experiment are simulated. The agreement of the experimental data and simulation results was excellent.With the aid of this model, the unprotected step reactivity addition and unprotected loss of flow of the 2 MWt experimental MSR are modeled, and the reactor power and temperature evolution are analyzed.

Study on dynamic characteristics of fission products in 2 MW molten salt reactor

In this study,a numerical flow model of the fission products(FPs)in the primary loop system of a molten salt reactor(MSR)was established and solved using Mathematica 7.0.The simulation results were compared with those of the ORIGEN-S program in the static burnup mode,and the deviation was found to be less than 10%,which indicates that the results are in good agreement.Furthermore,the FPs distribution in the primary loop system under normal operating conditions of the 2 MW MSR was quantitatively analyzed.In addition,the distribution phenomenon of the FPs under different flow rate conditions was studied.At the end of life,the FPs activity in the core region(including active region,and upper and lower plenum regions)accounted for 77.3%,and that in the hot leg #1,main pump,hot leg #2,heat exchanger,and cold leg region accounted for 1.2%,16.15%,0.99%,2.5%,and 1.9%,respectively,of the total FPs in the primary loop under normal operating conditions.The proportion of FPs in the core decreased with the increase in flow rate in the range of 2.24-22,400 cm^3 s^-1.The established analytical method and conclusions of this study can provide an important basis for radiation safety design of the primary loop,radioactive source management design,thermal-hydraulic safety analysis,and radiochemical analysis of FPs of 2 MW MSRs.

The design of RMT-based IOC redundancy at RCPI experimental platform in TMSR

In the RCPI(rod control and position indication) system prototype of the TMSR(Thorium Molten Salt Reactor) project, EPICS(Experimental Physics and Industrial Control System) was adopted as instrumentation and control software platform. According to long time running, high availability and safety for the system, RMT(redundancy monitor task) software package for Input/Output Controller(IOC) redundancy was employed, and the driver for redundancy control was realized. Test shows that the system could achieve IOC redundancy switch-over quickly and ensure the IOC running with long-term stability.

导热油槽式光热发电机组传储热系统运行控制的优化

光热发电作为一种新兴的清洁能源,在降低能源消耗、改善环境污染方面有着重要的意义。本文针对导热油槽式光热发电机组传储热系统运行控制问题,分析了传储热系统工作特性和运行控制方式,提出了控制模式的优化,并对系统常用运行模式的自动控制提出了建模方向和方式,有效提高了系统运行效率和稳定性,实现了太阳能光热发电的高效利用。

Avoiding sealing failure of flanged connection for tubes made of dissimilar materials subjected to elevated temperature

Carbonic composite materials and ceramics appear to be excellent structural materials for parts subjected to very high temperatures in molten salt reactors(MSRs), in which the reactor core outlet temperature is normally above 700℃. Because of the high temperature,there are major challenges in the sealing of flanged connections for tubes made of alloys and nonmetallic materials. In this study, an improved method for sealing bolted flange connections for tubes made of dissimilar materials at high temperature is analyzed. The study focuses on the compensation mechanism for the difference in thermal expansion between the bolts and the flanges. An angle is introduced for the sealing surface in the flanged connection to provide effective sealing. The arctangent of the angle is the ratio of the thickness between the theoretical core of the sealing surface and the outside end face of the flange to the distances between the axis of the flanged joint and the theoretical core of the sealing surface of the flange; the sealing surface of the flange, which is made of the same material as the fastening assemblies, faces the fastening assemblies. To ensure effective sealing, the frictional coefficient between the two sealing surfaces should not exceed the tangent of the angle. This result does not agree well with the solution given by previous researchers. Further, in the modified flanged connection, the compression of each bolt in the clamped condition is increased to maintain the compaction force unchanged without increasing the number of bolts on the flanged joint.

氟锂铍熔盐热中子散射效应对熔盐堆中子学性能的影响

氟锂铍(FLiBe)熔盐作为液态熔盐堆的冷却剂和载体盐,具有一定的慢化性能,其热中子散射数据影响熔盐堆的中子学性能,进而影响熔盐堆物理设计和安全运行。基于通用蒙特卡罗粒子输运程序分析了液态FLiBe熔盐的热中子散射数据对65 MW熔盐堆堆芯中子能谱、不同能谱下有效增殖因数k_(eff)、核素反应率、温度反应性系数等中子学性能的影响。研究结果表明:考虑FLiBe熔盐热散射效应,堆芯中子能谱变硬,导致~(235)U裂变反应率和k_(eff)变小,燃料的温度反应性系数中多普勒系数减小0.28×10~(-5) K~(-1),而密度反应性系数几乎无变化。当堆芯由热谱转变为相对较快的中子能谱时,FLiBe熔盐热散射效应导致~(235)U裂变率减少的变化量降低,k_(eff)的下降幅度从9.2×10~(-4)变为2×10~(-4)。因此,熔盐堆堆芯物理计算需开展FLiBe熔盐的热中子散射数据影响的量化。

基于EPICS架构的熔盐堆实时建模与仿真平台开发及验证

核电仿真技术被广泛地应用于反应堆设计、安全分析、独立安全评价、事故缓解措施、控制与保护系统设计与优化、先进主控室设计验证、操作员培训等方面的研究,有效地提高了核电厂的安全性和经济性。为满足液态燃料熔盐堆实时建模与仿真需求,基于实验物理与工业控制系统(Experimental Physics and Industrial Control System,EPICS)的开源、开放式架构,集成了具备实时动态交互功能的液态燃料熔盐堆系统分析程序RELAP5-TMSR和图形化人机交互界面模块,扩展了可视化控制与保护系统模块,开发了适用于液态燃料熔盐堆的开放式实时建模与仿真平台ThorTypography。以熔盐实验堆(Molten Salt Reactor Experiment,MSRE)的启泵、停泵、自然循环和反应性引入实验作为基准题,对ThorTypography平台开展了正确性验证和实时性测试。验证和测试结果表明:ThorTypography实时建模与仿真平台的计算结果和RELAP5-TMSR独立计算结果基本一致,均与MSRE实验数据符合较好;实时性测试数据显示,平台具有良好的实时性能。ThorTypography适用于液态燃料熔盐堆系统实时建模与仿真,能够为熔盐堆设计、运行和安全分析提供有效的支持。

熔盐槽式聚光集热镜场的夜间防凝运行方案研究

基于某熔盐槽式聚光集热供汽-供暖项目,针对夜间熔盐排空方案和夜间熔盐低速循环方案这两种主要的镜场夜间防凝运行方案,分别从方案的技术特点、需要配置的设备、运维难易程度、运维成本,以及方案优缺点等方面进行了全面的分析计算和比选研究。研究结果表明:1)采用夜间熔盐排空方案时,熔盐槽式聚光集热镜场的热损失较小,但聚光集热系统整体有效工作时间减少,导致整体的集热量和产出的蒸汽量减少,同时该方案对运维水平的要求较高;2)采用夜间熔盐低速循环方案时,熔盐槽式聚光集热镜场的热损失较大,配置的设备初始投资较高,但整体的运维成本及运维难度均较低;3)针对熔盐槽式聚光集热镜场,建议采用“夜间熔盐低速循环+防凝电加热器补热”的防凝运行方案,能够以较低的综合成本获得较好的运行效果。

GH3535合金表面渗铝层原位氧化工艺研究

高温工况下钍基熔盐堆中存在氚泄漏的风险,建立氚渗透屏障涂层有助于应对这一问题。采用包埋渗铝和原位氧化工艺,在GH3535合金表面制备了Al2O3/Ni-Al复合阻氚涂层,重点分析了氧化温度和真空度对氧化铝薄膜微观结构的影响。利用掠入射X射线衍射、扫描电子显微镜、透射电子显微镜等手段对氧化铝薄膜表面及截面的微观形貌、相构成进行了实验分析。实验结果表明:低氧分压能降低氧化铝薄膜的形成速度,促进形成更致密、表面平整的薄膜;高的氧化温度有利于形成α相氧化铝及更厚的氧化铝薄膜,但会大大增加表面缺陷。1.2 Pa真空度气氛、850℃氧化温度、72 h氧化时间是较优的原位氧化工艺参数,可以在GH3535合金基体表面获得性能较好的氧化铝薄膜,其相结构为γ和α相,厚度约为0.8μm,且表面致密无缺陷。

浅谈首批熔盐堆操纵员的职业素养

随着核能利用水平的不断提升和核安全等级标准的日趋提高,核能的安全发展对反应堆操纵员的综合能力提出了更高的要求。首批熔盐堆操纵员队伍建设正在有序推进,首批熔盐堆操纵员不仅担负着熔盐堆安全稳定运行的重任,而且对未来熔盐堆操纵员的培养起到示范作用。为了提高首批熔盐堆操纵员的职业素养,本文结合熔盐堆的运行特点和熔盐堆操纵员培养的现状,从四个方面建立熔盐堆操纵员的职业素养模型,旨在提高熔盐堆操纵员综合素养,培养一批适合熔盐堆并服务熔盐堆的优秀操纵员队伍。

熔盐堆中氚的控制和监测

熔盐堆中氚除了从废气中排出,还能经熔盐管道渗透进入环境。氚在管道中的渗透严重影响熔盐堆结构材料的力学性质和使用寿命,同时对环境造成污染。为了减少氚对材料和环境的危害,必须对熔盐堆中的氚进行严格控制。控制氚产生和渗透的主要方法包括提高7Li的浓度、向熔盐中补充Li或Be等。对氚进行监测是氚控制的基础,能及时反映熔盐堆的运行状况。本文讨论了测氚的方法:液体闪烁法、电离室法和正比计数器法。相比于液闪的离线测量,电离室和正比计数器都能达到在线测量的目的,然而液闪的灵敏度高,有更低的探测下限。为了能准确测量熔盐堆中氚的排放情况,可以同时采用液闪和电离室来进行测量。

新概念熔盐堆的固有安全性及相关关键问题研究

新概念熔盐堆是6种第四代反应堆中唯一的液体燃料反应堆,在固有安全性、经济性、核资源可持续发展及防核扩散等方面具有其它反应堆无法比拟的优点。针对熔盐堆的特点,建立通用的物理分析、热工水力分析和安全分析模型,并采用隐式方法实现物理热工的耦合。将建立的数学模型应用于锕系元素再循环嬗变熔盐堆(MOSART)的计算,对其堆芯物理特性、热工水力特性和安全特性进行了系统分析,考察了入口温度、速度及燃料盐在堆芯外运行时间的影响。

正常运行工况熔盐堆主回路衰变热特性研究

基于Mathematica 7.0建立了熔盐堆(Molten Salt Reactor,MSR)主回路系统衰变热流动模型,并与参考程序ORIGENS在静态燃耗下的计算结果以及熔盐实验堆(Molten Salt Reactor Experiment,MSRE)衰变热结果进行了初步验证,相对偏差分别在±4%和±2.76%的范围内符合较好。对2 MW液态燃料钍基熔盐实验堆(Thorium Molten Salt Reactor-Liquid Fuel 1,TMSR-LF1)正常运行工况下主回路系统管道及设备内的衰变热分布进行了定量分析。结果表明:启堆达到满功率和设定流量后约20 s各区域衰变热快速积累,随后便开始平缓上升并趋平衡。平衡时堆芯活性区衰变热占总衰变热的46.7%,上腔室、热管段#1、主泵、热管段#2、换热器、冷管段及下腔室区域分别占比31.8%、1.21%、14.6%、0.89%、2.21%、1.67%和0.94%。所建立的分析方法及结论可为熔盐堆主回路系统的热工水力安全分析、余热排出系统设计、反应堆功率调节与安全控制提供重要参考。

外围熔盐层堵塞状态下熔盐堆内部温度分布分析

出于冷却结构材料上的考虑,石墨慢化通道型熔盐堆通常在石墨反射层与反应堆容器间设置了外围熔盐层。针对2 MW液态燃料熔盐堆的概念设计,利用三维稳态热工水力学模型分析了外围熔盐层在不同堵塞情况下对反射层和合金温升造成的影响。熔盐堆内石墨慢化材料等固体区域的温度计算采用三维热传导模型,各个通道内熔盐采用一维单相流体模型描述。外围熔盐层在不同堵塞情况下分别采用一维单相流体模型和三维层流模型。计算结果表明:在外围熔盐层内总流量降低的堵塞情况下,外围熔盐层对反射层的冷却效果受到显著影响,在外围熔盐层的流量降低至堆芯额定流量0.365%时,反应堆容器的最高温度接近730°C,临近合金材料温度上的安全限值;当外围熔盐层内存在直径为4 cm的圆形局部堵塞(接近下熔盐通道半径)区域时,堵塞没有显著改变堆内的温度分布,堵塞区域的最高温度为621.74°C,未超过合金材料的安全限值。

新概念熔盐堆堆芯稳态热工水力计算

针对第四代国际核能论坛提出的新概念熔盐堆堆芯的具体特点,采用DRAGON程序计算了堆芯轴向和径向功率分布因子,并对熔盐堆的燃料盐和石墨慢化剂分别建立数学模型,通过数值方法对新概念熔盐堆的稳态热工水力特性进行了模拟。计算得到了堆芯燃料盐的流量分配,代表元件内燃料盐和内外壁温度沿轴向的变化。

TMSR核功率控制系统的PID设计与仿真

功率控制系统(Power Control System,PCS)是反应堆控制系统(Reactor Control System,RCS)的重要组成部分,它完成功率提升、功率保持与功率调节的作用。在钍基熔盐堆(Thorium Molten Salt Reactor,TMSR)核能系统固态堆设计方案中,功率控制器根据实测功率与设定功率值之间的偏差和偏差的变化趋势,按照经典的比例-积分-微分(Proportional Integral Derivative,PID)控制算法,给出调节控制棒的运动距离和运动方向等信号。PCS的PID算法设计与基于反应堆中子物理、热工及控制棒的传动性能构成的闭环控制系统的特性有关,其不同参数的确定与系统的静态和动态性能指标的要求相对应。本文从控制的角度出发,在已有的控制棒样机中设计的棒控棒位系统及相关中子物理的基础上对PCS的PID算法进行多层次仿真与参数分析,并对系统的可控性与可测性进行分析验证。分析及仿真结果表明两种控制模型下的系统均是完全可控及完全可测的,在合适的PID参数集下均能体现响应的快速性及系统的良好鲁棒性和抗干扰能力,具有实际的应用意义。