基于MOREL2.0对石墨慢化熔盐堆的稳态分析

熔盐堆采用熔融的氟化盐混合物作为燃料和堆芯的冷却剂,由于燃料的流动,熔盐堆在中子学和热工水力学方面与传统固体燃料反应堆有着较大区别。本文基于熔盐堆分析程序MOREL2.0对钍基熔盐堆（TMSR）初步堆芯设计方案进行了稳态计算分析,结果表明：燃料流动对缓发中子先驱核的分布影响较大,并导致169 pcm反应性损失;随燃料在外部回路中滞留时间的增加,k_eff降低,80 s后趋于平稳;TMSR具有负的入口燃料温度系数,具有固有安全性。     

Development of a MCNP5 and ORIGEN2 based burnup code for molten salt reactor

The Molten Salt Reactor(MSR) is one of the six advanced reactor nuclear energy systems for further research and development selected by Generation IV International Forum(GIF),which is distinguished by its core in which the fuel is dissolved in molten fluoride salt.Because fuel flow in the primary loop,the depletion of MSR is different from that of solid-fuel reactors.In this paper,an MCNP5 and ORIGEN2 Coupled Burnup(MOCBurn) code for MSR is developed under the MATLAB platform.Some new methods and novel arrangements are used to make it suitable for fuel flow in the MSR.To consider the fuel convection and diffusion in the primary loop of MSR,fuel mixing calculation is carried out after each burnup time step.Modeling function for geometry with repeat structures is implicated for reactor analysis with complex structures.Calculation for a high-burnup reactor pin cell benchmark is performed using the MOCBurn code.Results of depletion study show that the MOCBurn code is suitable for the traditional solid-fuel reactors.A preliminary study of the fuel mixture effect in MSR is also carried out.     

熔盐堆物理热工耦合程序开发及验证分析

熔盐堆(Molten Salt Reactor,MSR)是第四代反应堆6种堆型中唯一的液态燃料反应堆,与固态燃料-液体冷却剂反应堆相比,原理上有较大不同。在熔盐堆中,流动的熔盐既是燃料又是冷却剂与慢化剂,中子物理学与热工水力学相互耦合;由于熔盐的流动性,缓发中子先驱核会随燃料流至堆芯外衰变,造成缓发中子的丢失,导致堆芯反应性降低。正是由于熔盐堆的这些新特性,造成熔盐堆内缓发中子先驱核、温度等参数变化与固态燃料反应堆有所不同,需要研究熔盐堆在各种工况下的相关物理参数变化。本文主要工作是考虑缓发中子先驱核的流动性对熔盐堆的影响,研究适用于熔盐堆的二维圆柱几何时空中子动力学程序及与之耦合的热工水力学程序;利用该程序对熔盐堆中子物理学和热工水力学进行耦合计算,验证熔盐堆相关实验数据;并且计算了熔盐堆无保护启停泵及堆芯入口温度过冷过热工况,用于分析熔盐堆的安全特性。计算结果表明,程序能够对熔盐反应堆实验(Molten Salt Reactor Experiment,MSRE)的相关实验数据进行较好的模拟计算,并且验证了熔盐堆的固有安全性。     

石墨慢化通道式熔盐堆的稳态热工水力计算模型

针对石墨慢化通道式熔盐堆的堆芯结构,基于COMSOL Multiphysics程序和MATLAB程序建立了堆芯稳态热工水力学计算模型。该模型对堆芯内固体区域的温度分布采用三维热传导方程进行模拟,对通道内熔盐温度采用一维单相流体模型进行计算。固体区域与熔盐通过熔盐通道壁面的对流换热边界建立热耦合。该模型基于平行通道压力损失相等的原则,分配堆芯内各熔盐通道的流量。通过对比RELAP5程序的计算结果,验证了模型对温度和流量分配计算的正确性。针对2 MWt 液态燃料熔盐堆的一种概念设计,分析了堆芯内三维温度分布和通道间流量分配。该模型可精确计算通道式熔盐堆堆芯内稳态温度分布和流量分配,对堆芯的热工水力学设计具有重要意义。     

Development of a steady state analysis code for a molten salt reactor

The molten salt reactor (MSR), which is one of the ‘Generation IV’ concepts, can be used for transmutation, and production of electricity, hydrogen and fissile fuels. In this study, a single-liquid-fueled MSR is designed for conceptual research, in which no solid material is present in the core as moderator, except for the external reflector. The fuel salt flow makes the MSR neutronics different from that of conventional reactors using solid fuels, and couples the flow and heat transfer strongly. Therefore, it is necessary to study the core characteristics with due attention to the coupling among flow, heat transfer and neutronics. The standard turbulent model is adopted to establish the flow and heat transfer model, while the diffusion theory is used for the neutronics model, which consists of two-group neutron diffusion equations for fast and thermal neutron fluxes, and balance equations for six groups of delayed neutron precursors. These two models which are coupled through the temperature and heat source are coded in a microcomputer program. The distributions of the velocity, temperature, neutron fluxes, and delayed neutron precursors under the rated condition are obtained. In addition, the effects of the inflow temperature, inflow velocity, and the fuel salt residence time out of the core are discussed in detail. The results provide some valuable information for the research and design of the new generation molten salt reactors.     

DYN1D-MSR dynamics code for molten salt reactors

This paper reports about the DYN1D-MSR code development and dynamics studies of the molten salt reactors (MSR) – one of the ‘Generation IV International Forum’ concepts. In this forum the graphite-moderated channel type MSR based on the previous Oak Ridge National Laboratory research is considered.The liquid molten salt serves as a fuel and coolant, simultaneously and causes two physical peculiarities: the fission energy is released predominantly directly into the coolant and the delayed neutrons precursors are drifted by the fuel flow. The drift causes the spread of delayed neutrons distribution to the non-core parts of primary circuit and it can lead to a reactivity loss or gain in the case of fuel flow acceleration or deceleration, respectively. Therefore, specific 3D tool based on in house code DYN3D was developed in FZR. The code DYN3D-MSR is based on the solution of two-group neutron diffusion equation by the help of a nodal expansion method and it includes models of delayed neutrons drift and specific MSR heat release distribution.In this paper the development and verification of 1D version DYN1D-MSR of the code is described. The code has been validated with the experimental data gained from the molten salt reactor experiment performed in the Oak Ridge and after the validation it was applied to several typical transients (overcooling of fuel at the core inlet, reactivity insertion, and the fuel pump trip).     

一种液态燃料熔盐堆堆芯流量分配设计

在液态燃料熔盐堆(Molten salt reactor,MSR)热工水力设计中,为实现堆芯径向功率展平需对堆芯流量分配进行设计,使得堆芯进口流量分布正比于释热量分布,而下腔室结构和流场分布对堆芯流量分配起决定性作用。利用FLUENT软件对堆芯三维流场进行模拟,通过调节下腔室结构和流量分配装置,对下腔室流场分布进行优化,最终实现堆芯流量合理分配。数值模拟结果表明,喇叭状下腔室比椭球形下腔室熔盐通道流量标准差降低4.2%,设置流量分配板熔盐通道流量标准差降低29.2%;改变下腔室结构和设置流量分配装置能够较好调节流量分配和功率分布匹配性,该结果可为液态熔盐堆堆芯优化设计提供依据。     

石墨慢化通道式熔盐堆有效缓发中子份额计算方法研究

有效缓发中子份额(βeff)是研究反应堆动力学特性的关键参数。在液态燃料熔盐堆(MSR)中,燃料流动引起缓发中子先驱核(DNP)在堆内的再分布,并使部分DNP在堆外回路衰变,从而导致βeff的计算方法与固态燃料反应堆不同。为评估石墨慢化通道式熔盐堆内燃料流动引起的反应性损失,研究缓发中子随燃料的流动行为,同时为堆设计和安全分析提供依据,分别基于解析方法和数值方法推导了计算βeff的数学模型,计算了熔盐实验堆(MSRE)在额定工况下的DNP损失份额和堆内DNP浓度分布,并分析了燃料在堆外流动时间和入口流量对βeff的影响。结果表明：两种方法均可对DNP行为提供合理描述;固定燃料在堆外流动时间,βeff随入口流量的增加而减小;固定入口流量,βeff随燃料在堆外流动时间的增加而减小,80 s后趋于稳定。     

熔盐反应堆——放射化学创新发展的新源泉

本文从放射化学视角简略介绍了熔盐堆及其在钍铀燃料循环应用中的优势,然后叙述了与熔盐堆相关的放射化学研究的三个方向:即燃料供给、辐照后燃料的再处理以及熔盐堆运行的工艺监测和核素诊断。在燃料的再处理中推荐了一种类似文献报道的AIROX流程的干法后处理的新技术路线,指出其在熔盐堆在线燃料处理中的优点和重要价值。由于熔盐堆的运行中存在大量的化学与放射化学问题,因此熔盐堆堪比"化学堆",放射化学监测和诊断对于熔盐堆的运行有极其重要的意义。由此可见,熔盐堆研发促使形成了放射化学的一门新的分支学科——以监测和诊断为目标的熔盐反应堆化学。最后给出了放射化学工作者在熔盐堆发展过程中应该注意的若干建议。     

熔盐堆的安全性介绍

介绍了四代反应堆的分类与特点,简述了第四代反应堆中唯一使用液态燃料的熔盐堆工作原理。基于与其他使用固体芯块燃料反应堆的比较,主要简述了熔盐堆更高的固有安全性特点,以及熔盐堆在燃料供应、废料最小化、防止核扩散诸方面的安全性优点以及熔盐堆发展面临的问题和挑战。说明了由于熔盐堆较高的工作温度使用布雷顿循环,提高热效率的优点。...     

液态熔盐堆运行安全特性初步研究

液态燃料反应堆与固态燃料反应堆相比,原理上有较大不同。液态熔盐堆中由于燃料流动带走缓发中子先驱核在堆外衰变导致堆芯反应性降低,且裂变产物在堆外回路中衰变也会引起一回路发热。本文使用熔盐堆中子动力学程序Cinsf1D探讨2 MW熔盐堆的临界动力学特性和安全特性,研究零功率临界下不同熔盐流速启泵和停泵导致的缓发中子先驱核流失所需改变的控制棒棒位。同时还计算了2 MW恒定功率情况下稳态运行及降低流速时一回路温度分布,并模拟了2 MW额定功率下停泵事件。停泵后由于缓发中子损失减少反应堆功率先缓慢增加,然后迅速降低到接近余热水平。停泵后堆芯温度缓慢增加后稳定在安全值以内,说明熔盐堆具有本征安全性。     

基于SCALE的熔盐堆添料与后处理系统分析程序开发及验证

在线添料及在线去除中子毒物是熔盐堆区别于其他固体燃料反应堆的主要特征之一,能够实现较高的燃耗深度和燃料利用率。然而,现有的反应堆物理计算分析软件SCALE不能直接模拟熔盐堆的燃耗计算。因此,本文耦合SCALE中的截面处理模块、临界计算模块以及燃耗计算模块,开发了一套适用于多流体熔盐堆的添料与后处理系统分析程序MSR-RRS,实现熔盐堆的在线添料、裂变产物在线处理或离线批次处理等模拟功能。基于MSR-RRS对现有的单流熔盐增殖堆和双流熔盐快堆的燃耗性能进行了验证。结果表明,MSR-RRS计算结果与基准模型结果符合较好。MSR-RRS适用于多种堆型、多种燃料循环运行模式。     

Transient behavior of the sodium–potassium alloy heat pipe in passive residual heat removal system of molten salt reactor

High temperature heat pipes, as highly-effective heat transfer elements, have been extensively employed in thermal management for their remarkable advantages in conductivity, isothermality and self-actuating. It is of significance to apply heat pipes to new concept passive residual heat removal system (PRHRS) of molten salt reactor (MSR). In this paper, the new concept PRHRS of MSR using sodium–potassium alloy (NaK) heat pipes is proposed in detail, and then the transient behavior of high temperature NaK heat pipe is numerically investigated using the Finite Element Method (FEM) in the case of MSR accident. The two-dimensional transient conduction model for the heat pipe wall and wick structure is coupled with the one-dimensional quasi-steady model for the vapor flow when vaporization and condensation occur at the liquid–vapor interface. The governing equations coupled with boundary conditions are solved by FORTRAN code to obtain the distributions of the temperature, velocity and pressure for the heat pipe transient operation. Numerical results indicated that high temperature NaK heat pipe had a good operating performance and removed the residual heat of fuel salt significantly for the accident of MSR.     

熔盐堆单参数扰动瞬态特性分析

熔盐堆（MSR）作为一种新型的反应堆,其热工水力特性与其他堆型有很大差异,扰动瞬态分析有助于从根本上了解其安全特性和运行状态。为了研究MSR的运行瞬态特性,本研究以液态燃料MSR为研究对象,利用经过修改的RELAP5/ MOD4.0程序进行了稳态运行工况下的扰动瞬态分析。干扰变量包括反应性引入、一回路熔盐质量流量、二回路质量流量、空气散热器质量流量、空气散热器入口空气温度。分析了主要运行参数,如功率、堆芯进出口温度、二回路进出口温度、特征时间等。结果表明MSR在各种扰动瞬态下的最终状态都趋于稳定,而不存在严重的瞬态变化,这是对其固有稳定性特性的直观表征。根据功率和温度等变量在扰动下的变化,提出了功率和不同回路温度的控制方法。      

DRAGON&DONJON程序在MSR中堆芯燃耗计算的适用性

DRAGONDONJON组件-堆芯"两步法"程序通过合理简化,理论可适用于任何堆芯与工况。使用蒙特卡罗方法 RMC(Reactor Monte Carlo code)、MCNP(Monte Carlo Neutron Particle transport code)程序验证DRADON程序是否能够承担快/热谱型熔盐堆(Molten Salt Reactor,MSR)焚烧TRU、Th U燃料燃耗计算。选出熔盐增殖堆(Molten Salt Breeder Reactor,MSBR)与熔盐锕系元素再循环和嬗变堆(Molten Salt Advanced Reactor Transmuter,MOSART)堆型进行比较,同时分别利用RMC程序验证DRAGON程序组件燃耗计算的准确性,利用MCNP程序验证DRAGON程序组件均匀化方法以及DONJON程序截面调用和程序全堆扩散的准确性。结果表明,组件燃耗计算中,TRU和Th U燃料满足燃耗计算要求;堆芯临界计算中,快/热谱堆芯计算误差均小于0.001。证明DRADON程序可以胜任快、热谱型MSR焚烧TRU、Th U燃料的物理计算任务。     

Analysis on reactivity initiated transient from control rod failure events of a molten salt reactor

In a molten salt reactor （MSR）, the fuel is dissolved in fluoride salt. In this paper, the reactivity worth and reactivity initiated transient of Molten-Salt Reactor Experiment （MSRE） in the control rod failure events are analyzed, The point kinetic coupling heat-transfer model with decay character of six-group delayed neutron precursors due to the fuel motion is applied. The relative power and temperature transient under reactivity step and ramp initiated at different power levels are studied. The results show that the reactor power and temperature increase to a maximum, where they begin to decrease to stable values. Comparing with full power level, the transient result at low power level is more serious. The results are of help in our study on safety characteristics of an MSR system.     

TRU燃料热谱MSR定期换料及嬗变特性数值研究

熔盐反应堆（MSR）燃料制备方便、中子经济性好、燃料管理灵活,具有直接利用轻水堆乏燃料中超铀核素（TRU）的潜力。本文通过优化燃料选取、栅格参数及燃料/石墨体积分数和去除裂变气体和惰性金属等方法,对TRU燃料热谱MSR堆芯寿期、TRU核素积存量、次锕系核素MA嬗变支持比和TRU焚毁率等进行计算分析,证明TRU燃料热谱MSR可实现长周期定期换料,减少在线换料的难度,同时对MA和TRU核素具有一定的嬗变能力,可降低乏燃料放射性毒性。      

钍基熔盐堆核能系统中熔盐的蒸馏纯化与分离

氟盐具有化学与辐射稳定性高、热容量大、传热性能好、运行温度高和蒸汽压低等优点,被用作熔盐堆的燃料载体和冷却剂。随着熔盐堆技术的发展,开发熔盐的净化、回收工艺非常必要。熔盐减压蒸馏技术基于物质挥发性差异进行组分分离,由于过程操作简单、不引入新的物质等特点,在燃料处理过程中有广泛应用。利用减压蒸馏技术对钍基熔盐堆核能系统的载体盐回收、电解产物纯化、模拟燃料球去除浸渗熔盐等方面进行了研究。研究结果表明,含CsF、SrF_2、LaF_3和ThF_4的FLiNaK盐经减压蒸馏处理,可从FLiNaK中除去SrF_2和LaF_3,去污因子分别为4.4×10~3和1.9×10~3,Th的去污因子为94;通过蒸馏可去除电解产物表面夹带的氟盐,纯化电解产物;燃料球中浸渗熔盐在1 085℃下处理37h可去除石墨球中94%的浸渗熔盐。