加速器驱动的次临界系统散裂靶热工水力研究

散裂靶位于加速器驱动的次临界系统（ADS）的中心,为核嬗变提供所需的中子源。通过分析散裂靶的热工要求,选取铅铋合金（LBE）作为ADS的靶材料和冷却剂。使用MCNP程序计算质子束轰击靶区产生的能量沉积,并使用CFD程序FLUENT计算靶区热工特性。分析了不同设计参数及不同靶窗形状对ADS靶区温度分布和速度分布的影响,得到满足热工要求的可选方案。     

基于水工质的有窗散裂靶流场分析及实验测量

散裂靶是加速器驱动的次临界系统(ADS)的重要组成部分,有窗散裂靶是唯一经实验验证、测量的液态金属高功率散裂靶,研究有窗靶内工质的流动对散裂靶的设计优化有重要意义。本文以水为工质对有窗靶件进行了可视化实验及数值模拟研究,实验采用粒子图像测速法对靶件可视化部分进行速度场测量,同时利用计算流体力学软件FLUENT对靶件流场进行数值模拟。通过5种湍流模型（标准k-ε模型、RNG k-ε模型、Realk-ε模型、SST k-ω模型、RSM模型）在不同流速下的模拟结果与实验结果的对比分析,表明采用RNG k-ε模型并结合相应的壁面函数能较准确模拟有窗靶内的流动。     

加速器驱动的次临界系统散裂靶泄漏中子谱研究

为研究加速器驱动的次临界系统（ADS）散裂靶的散裂中子学特性,采用Geant4计算不同能量质子轰击铅铋靶产生的泄漏中子产额、能谱、轴向积分分布。模拟得到1 GeV质子对应的靶的优化尺寸及优化后泄漏中子谱,计算结果可为ADS散裂靶件和堆芯设计提供参考。     

周期法测量启明星Ⅱ号散裂靶材料的反应性价值

为验证理论计算程序及相关核数据，将固体散裂靶材料放入ADS启明星Ⅱ号零功率装置（启明星Ⅱ号）的靶区内，采用周期法测量靶区内有、无散裂靶材料的反应性，从而获得净散裂靶材料对应的反应性价值，并与理论计算结果进行比较。结果表明，反应性价值的实验测量结果与理论计算结果符合较好，验证了理论计算的正确性。经实验验证的理论计算程序和核数据可用于ADS次临界反应堆的设计。     

基于流场数值模拟的ADS靶件结构的设计优化

采用通用的计算流体力学（CFD）软件PHOENICS 3．3和BFC计算网格生产技术，对加速器驱动次临界系统（ADS）靶件的流场进行数值模拟计算。结果表明：束窗下方导流板起引导流体沿束窗表面流动的作用，消除了束窗两侧下方较大的旋涡，对于改善束窗附近流体的流动结构、提高束窗表面及散裂靶的换热，效果显著。     

颗粒流散裂靶缩比模型流态实验研究

散裂靶是加速器驱动次临界系统（ADS）的重要组成部分,颗粒流散裂靶是最新提出并经理论计算的一种高功率散裂靶,研究其颗粒流的流动特性对散裂靶的设计优化有重要意义。本文以螺旋提升机为颗粒流驱动装置,搭建一套颗粒流循环回路系统,研究了倾斜段管道的倾斜角度对三维颗粒流从堵塞流向密集流转变的影响。研究发现,随着螺旋提升机提升频率的增加（即颗粒流量的增加）,在散裂靶靶区存在颗粒稀疏流-密集流转变,在靶区附近能形成稳定的密集流。     

基于DEM的重金属颗粒流靶区输运过程研究

基于固体和液体散裂靶,近期国内外研究学者提出了一种新概念重金属颗粒流散裂靶。加速器驱动次临界系统(ADS)中重金属散裂靶在高能质子轰击作用下,出现能量沉积现象,而这些热量必须进行有效冷却以保证ADS的安全性。本文针对这种新概念颗粒流靶对靶区产生的高额热量的导出效果进行了模拟分析。首先采用蒙特卡罗程序计算450 Me V质子束轰击钨靶后能量沉积的空间分布,并将此作为颗粒流的体热源输入,基于计算流体力学-离散单元法(CFD-DEM)耦合方法对ADS靶区两种不同直径颗粒流的输运过程进行了模拟研究。结果表明,随颗粒直径的减小,靶区内温度分布更为均匀,颗粒流的流动特性更接近流体,颗粒导热性能增强;颗粒流靶中热应力可局限在单个颗粒内部而承受更高的能量沉积,具有更高的安全限值以及更广阔的应用前景。     

ADS熔盐散裂靶中子学性能研究

与传统加速器驱动次临界系统（ADS）采用金属靶作为散裂中子靶的设计不同，加速器驱动次临界熔盐堆（AD-MSRs）采用靶堆一体的设计，直接使用燃料熔盐作为散裂中子靶。由于熔盐靶的中子学性能直接影响AD MSRs的能量放大系数、核废物的嬗变和核燃料增殖的效率，所以本研究基于MCNPX程序，详细计算了高能质子轰击氟盐和氯盐两种熔盐靶产生的散裂中子产额、散裂中子能谱、能量沉积分布以及散裂产物等中子学性能，并与液态Pb和铅铋共熔体（LBE）两种液态金属靶进行了对比。计算结果表明，熔盐靶在散裂中子产额上与液态金属靶有一定的差距，但熔盐靶内能量沉积分布的梯度较小，更有利于靶区的热量导出。与液态Pb和LBE靶相比，熔盐靶的散裂产物中包含更多的气体以及高质量数的α发射体核素。     

铅散裂中子靶物理特性研究

利用蒙卡程序DCM/CEM对ADS标准散裂中子靶进行了计算。计算了长0.6 m,直径0.2 m的圆柱形208Pb靶,在0.1～1.6 GeV的质子轰击下,Pb靶发生散裂反应产生的中子产额及表面的中子注量、能谱分布以及靶内能量沉积分布,解释了以前的实验结果。计算结果与文献数据、实验数据进行了比较,符合良好,对进一步进行ADS堆芯设计具有较好的理论指导意义。     

ADS加速器束流瞬变分析程序开发

加速器驱动的反应堆系统(ADS)中次临界堆芯的功率水平依靠强流质子轰击散裂靶产生的中子源来维持,质子束流的不稳定性将对次临界堆的功率水平产生影响,进而对ADS的安全性产生影响.本文研究了ADS系统束流瞬变事故特性,建立了相应的物理数学模型,设计开发出具有较强针对性的用于ADS系统束流瞬变事故仿真软件--SIMULINK-ADS.并选取了典型的束流瞬变工况进行分析,通过与OECD/NEA和FZK Karlsruhe研究成果进行比较,验证了SIMULINK-ADS程序能够有效地计算和分析ADS束流瞬变次临界反应堆堆芯物理及热工响应.     

Numerical design of a 20 MW lead–bismuth spallation target for an accelerator-driven system

A spallation target system is a key component to be developed for an accelerator-driven system (ADS). It is known that a 15–25 MW spallation target is required for the practical size of an ADS. Although there have been some design studies for small power spallation targets, that is, less than 10 MW, designs of high power target systems for ADS are relatively rare. The design of a 20 MW spallation target is very challenging because more than 60% of the beam power is deposited as heat in a small volume of the target system. In the present work, a numerical design study was performed to get optimal design parameters for a 20 MW spallation target for a 1000 MW ADS. The cylindrical beam tube and the hemispherical beam window were adopted in the basic target design concept with 1 GeV proton energy, and the thermal-hydraulic and the structural analyses were performed with the CFX and ANSYS codes. The beam window diameter and thickness were varied to find the optimal parameter set based on the design criteria: maximum lead–bismuth eutectic (LBE) temperature <500 °C, maximum beam window temperature <600 °C, maximum LBE velocity <2 m/s, and the maximum beam window stress <160 MPa. The results of the present study show that a 40 cm wide proton beam with a uniform beam profile should be adopted for the spallation target of 20 MW power. It was found that a 2.5 mm thick beam window is needed to sustain the mechanical load.     

Computational fluid dynamics analysis of spallation target for experimental accelerator-driven transmutation system

One of the key milestones in the roadmap of the European accelerator-driven transmutation system (ADS) is the design and construction of the European experimental ADS (XADS). The window spallation target unit in the lead–bismuth eutectic (LBE) cooled reactor system is one of the basic options considered in the preliminary design study of XADS (PDS-XADS). This paper presents the computational fluid dynamics (CFD) analysis and the main results achieved for this option focusing on the coolability of the window. Steady-state as well as transient behavior, including beam interrupts and three major accident scenarios, has been analyzed using the CFD code CFX 5.6 with an advanced turbulence model. The required boundary conditions were provided by a one-dimensional system code. Based on the CFD analysis, the window geometry was modified in order to achieve sufficient cooling capability of the window under normal operating conditions. The transient behavior of the window temperature under beam trip conditions shows the importance of the beam interrupt duration to the thermal stress load of the window structural material. Further transient analysis of three major accidental scenarios, i.e., beam focusing, loss of heat sink, and beam intensity jump, indicates that the beam focusing accident gives the most serious safety concern. In this case, window failure occurs in less than 1 s after the start of the beam focusing.     

Numerical design of a 20 MW lead–bismuth spallation target with an injection tube

A spallation target system is a key component to be developed for an accelerator driven system (ADS). It is known that a 15–25 MW spallation target is required for a practical 1000 MW_th ADS. The design of a 20 MW spallation target is very challenging because more than 60% of the beam power is deposited as heat in a small volume of the target system. In the present work, a numerical design study was performed to obtain the optimal design parameters for a 20 MW spallation target for a 1000 MW_th ADS. A dual injection tube was proposed for a reduction of the lead–bismuth eutectic (LBE) flow rate at the target channel. The results of the present study show that a 30 cm wide proton beam with a uniform beam distribution should be adopted for a spallation target of a 20 MW power. When the dual LBE injection tube is employed, the LBE flow rate could be reduced by a factor of 7 without reducing the allowable beam current.     

Research and Development Program on Accelerator Driven Subcritical System in JAEA

For a dedicated transmutation system, Japan Atomic Energy Agency (JAEA) has been proceeding with the research and development on an accelerator-driven subcritical system (ADS). The ADS proposed by JAEA is a lead-bismuth eutectic (LBE) cooled fast subcritical core with 800 MWth. JAEA has started a comprehensive research and development (R&D) program since the fiscal year of 2002 to acquire knowledge and elemental technology that are necessary for the validation of engineering feasibility of the ADS. In this paper, the outline and the results in the first three-year stage of the program are reported. Items of R&D were concentrated on three technical areas peculiar to the ADS: (1) a superconducting linear accelerator (SC-LINAC), (2) the LBE as spallation target and core coolant, and (3) a subcritical core design and reactor physics of the ADS. For R&D on the accelerator, a prototype cryomodule was built and its good performance in electric field was examined. For R&D on the LBE, various technical data for material corrosion, thermal-hydraulics and radioactive impurity were obtained by loop tests and reactor irradiation. For R&D on the subcritical core, engineering feasibility for the LBE cooled tank-type ADS was discussed using thermal-hydraulic and structural analysis not only in normal operation but also in transient situations. Reactor physics experiments for subcritical monitoring and physics parameters of the ADS were also performed at critical assemblies.     

Implementation of an LBE spallation target in an accelerator-driven molten salt subcritical reactor

An accelerator-driven system (ADS) combined with a subcritical molten salt reactor (MSR) is a type of hybrid reactor originally designed to use Th/U (or U/Pu ) fuel cycles. In most accelerator-driven molten salt reactor (AD-MSR) concepts, the salt material is also used as a target for inducing spallation neutrons. Although a neutron source is an important component in the design of ADS, only a few studies have addressed the effects of the neutron spallation source in the AD-MSR. Incidentally, there is no quantitative study on how much the beam power can be reduced by installing a spallation target in a sodium chloride-based fast reactor. We studied the proton and the neutron source efficiencies of an AD-MSR with chloride fuels by considering an Lead Bismuth Eutectic (LBE) spallation target. This LBE target is found to increase the proton source efficiency significantly. The required beam power for an AD-MSR can be reduced by 33 % and 16 % for NaCl-Th/²³³U and NaCl-U/Pu fuels, respectively, relative to the AD-MSR without the LBE spallation target by keeping the same k_eff. The energy gain can be increased up to 1.5 times and 1.2 times for NaCl-Th/²³³U and NaCl-U/Pu fuels, respectively. Thus, incorporating a spallation target module in an AD-MSR can significantly reduce the burden on the accelerator.     

Preliminary physics study of the Lead–Bismuth Eutectic spallation target for China Initiative Accelerator-Driven System

The Lead-Bismuth Eutectic(LBE) spallation target has been considered as one of the two alternatives for the spallation target for China Initiative Accelerator-Driven System.This paper reports the preliminary study on physical feasibility of a U-type LBE target with window.The simulation results based on Monte Carlo transport code MCNPX indicate that the spallation neutron yield is about 2.5 per proton.The maximum spallation neutron flux is observed at about 3 cm below the lowest part of the window.When the LBE target is coupled with the reactor,the reactor neutrons from the fission reaction increased the neutron field significantly.The energy deposition of highenergy protons is the main heat source;the spallation neutrons and reactor neutrons contribute only a small fraction.The maximum energy deposition in the LBE is about 590 W/cm~3 and that in the target window is about319 W/cm~3.To estimate the lifetime of the target window,we have calculated the radiation damages.The maximum displacement production rate in the target window is about10 dpa/FPY.The hydrogen and helium production rates generated during normal operation were also evaluated.By analyzing the residual nucleus in the target during the steady operation,we estimated the accumulated quantities of the extreme radioactivity toxicant ~(210)Po in the LBE target loop.The results would be helpful for the evaluation of the target behavior and will be beneficial to the optimization of the target design work of the experimental facilities.     

Preliminary design of inner radius of spallation target of an accelerator driven subcritical reactor for waste transmutation (ADS-NWT)

This paper presented preliminary design studies of inner radius of spallation target for lead-bismuth cooled accelerator driven sub-critical reactor, aimed at reducing proton beam current while simultaneously maintaining high Minor Actinides transmutation performance. Lead-bismuth eutectic (LBE) and uranium-free metallic dispersion fuel were used as the coolant and the fuel for this 1000 MWt reactor. By taking Proton Transmutation Support Ratio (PTSR) as an evaluation index, the inner radius of the spallation target was designed for this reference reactor and the optimized design proposal could obtain the higher transmutation performance. The preliminary study found that when the inner radius of the spallation target ran up to a certain value, the spallation neutron yield would have greater influence on the transmutation performance.     

Thermal–hydraulic studies related to the design of LBE neutron spallation target for accelerator driven systems

Recently, studies have been taken up in world's leading nuclear research institutes to develop accelerator driven systems (ADS). Our department has earlier proposed a one-way coupled fast-thermal reactor of 750 MW (thermal). This reactor requires current in the range of 1–2 mA for proton beam of 1 GeV. A suitable liquid metal lead bismuth-eutectic (LBE) target based on buoyancy as well as gas driven method has been designed for this reactor earlier. In this paper, detailed thermal analysis in the spallation and window region has been carried out to study the operability of the target from thermo-mechanical point of view. FLUKA and computational fluid dynamics (CFD) codes have been used for this analysis. The results indicate that, the temperatures, thermo-mechanical stresses are within the required values. The detailed analysis of this work is presented in this paper.