ADS无窗靶件自由界面模拟实验和数值研究

冷却剂自由界面形态的形成和控制是加速器驱动的次临界系统(ADS)无窗靶件设计的关键技术之一。采用水介质对无窗靶件模型的自由界面特征进行了实验和数值研究。实验中采用激光诱导荧光的示踪方法实现了流场的可视化,得到Re=30000～50000范围内的自由界面和可视化流场。在高Re工况下,流场中出现大尺度的非稳定涡结构,随着Re的降低,流场中涡结构的紊乱程度增加。分别采用大涡模型（LES）和两方程动能-特征耗散率模型（kω-SST）对无窗靶件实验工况进行了数值分析,计算结果表明,LES能较好地模拟实验中所得的流场现象和界面特征。     

ADS无窗靶件流场结构和自由界面数值模拟研究

自由界面流动现象是加速器驱动次临界系统(ADS)无窗靶件研究的重要组成部分。采用计算流体动力学(CFD)方法,对上海交通大学设计的无窗靶件流道结构中的自由界面流动水力学行为进行数值模拟研究。数值模拟使用FlUENT软件平台,采用体积流体法(VOF)与界面追踪方法结合湍流大涡模型(LES),进行Re在35000⁸0000工况下的非稳态计算。模拟结果得到了自由界面稳定性、自由界面宽度、大尺度漩涡结构、漩涡滞止区长度和锥形段流道沿程压力随Re变化的规律。     

无窗散裂靶自由界面流动水力特性研究

自由界面形成和控制是加速器驱动的次临界系统(ADS)无窗靶研究的重要内容。本文通过水模拟实验,结合360°全尺度模拟计算,验证了自由界面的特征主要受入口速度和出口压力控制,得到了自由界面长度随入口速度增大而二次递减、随出口压力增大而线性递减的结论。对流场的结构和特征进行了研究,说明了漩涡区域对自由界面流动的影响。采用VOF界面追踪方法、大涡湍流模型(LES)以及PISO算法进行瞬态模拟计算,计算得到的自由界面流动和流场结果均与实验结果符合较好,表明计算模型和方法可用于液态重金属靶的流体力学计算。     

上旋式无窗散裂靶件自由界面数值研究

无窗散裂靶件是加速器驱动的次临界系统的重要组成部分。为了使靶件维持稳定的自由界面并具有良好的热移出功能,本文提出一种上旋式无窗靶件设计,以水为工质,采用ANSYS Fluent软件对该靶件设计进行数值模拟。结果表明,该结构散裂靶件能较好地维持稳定自由界面,不会出现漩涡滞止区,并得到不同入口流速对自由界面形状、流场特征及压降的影响。     

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。     

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。     

基于扩散界面法的ADS无窗散裂靶自由界面数值研究

采用水作为模拟工质,用扩散界面法和有限元法以及k-ε湍流模型对无窗靶件的自由界面非稳态特性进行数值模拟。结果和实验吻合较好,表明扩散界面法能准确地进行模拟,并且结果表明流场中存在一个回流区以及中心线沿程压力存在一个谷值和峰值。通过计算不同出口背压下的自由界面的形状和高度,获得出口压力对界面稳定性的影响,同时计算不同出口背压对回流区长度的影响以得到增大无窗靶的热移出能力的规律,结果表明:出口背压在900Pa以上,自由界面较稳定,不会产生明显的气泡,出口背压越大,自由界面越稳定,高度越高;同时,出口背压越大,回流区的高度越低,热移出能力越强。     

PDS-XADS散裂靶热工水力分析

本文对小型加速器驱动的次临界系统（ADS）--PDS-XADS散裂靶进行了热工水力分析。分析的XADS型实验堆基于欧洲PDS-XADS实验项目的设计,使用铅铋合金（LBE）作为冷却剂。散裂靶是ADS的核心部件之一,用以确保反应堆功率维持在指定水平。本文利用计算流体力学软件ANSYS CFX 11.0对散裂靶的下部区域进行热工水力分析。分析采用稳态计算、剪切应力输运（SST）湍流模型,在壁面边界条件处采用自动壁面函数法,针对不同的散裂靶设计进行计算流体力学（CFD）分析,最后根据散裂靶设计限值选择最优设计方案。     

加速器驱动系统靶区流场的数值模拟

在加速器驱动系统（ADS）中,真空质子束流管出口端为一半球面质子束窗,用于隔离束流管和散裂靶。质子束窗表面热负荷很高,有效冷却质子束窗,从而提高靶件寿命和系统安全性是靶件设计的关键。 采用PHOENICS 3.2程序对ADS靶件冷态下的流场进行数值模拟。在贴体坐标（BFC）下生成计算网格,对靶件束窗下方有无导流板时的靶区流场进行了计算。当体积流量为10m3/h时,流体向下流动进入中央流道（靶区）之前发生边界层脱离,并在质子束窗下方两侧形成一对对称的旋涡。两旋涡在靶区中央重叠,形成一股向上较强的回流。这股回流沿质子束窗     

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。     

WEBEXPIR: Windowless target electron beam experimental irradiation

The windowless target electron beam experimental irradiation (WEBEXPIR) program was set-up as part of the MYRRHA/XT-ADS R&D effort on the spallation target design to investigate the interaction of a proton beam with a liquid lead-bismuth eutectic (LBE) free surface. In particular, possible free surface distortion or shockwave effects in nominal conditions and during sudden beam on/off transient situations, as well as possible enhanced evaporation were assessed. An experiment was conceived at the IBA TT-1000 Rhodotron, where a 7 MeV electron beam was used to simulate the high power deposition at the MYRRHA/XT-ADS LBE free surface. The geometry and the LBE flow characteristics in the WEBEXPIR set-up were made as representative as possible of the actual situation in the MYRRHA/XT-ADS spallation target. Irradiation experiments were carried out at beam currents of up to 10 mA, corresponding to 40 times the nominal beam current necessary to reproduce the MYRRHA/XT-ADS conditions. Preliminary analyses show that the WEBEXPIR free surface flow was not disturbed by the interaction with the electron beam and that vacuum conditions stayed well within the design specifications.     

液态金属镓回路搭建及无窗靶实验研究

液态金属回路是开展液态金属散裂靶关键技术与实验验证的必备实验平台。镓具有较低的熔点、非常高的沸点,且无毒性,可在液态金属回路实验中作为模拟介质使用。本文介绍了一套小型液态金属镓回路的设计思路、结构组件、基本功能及使用流程,给出了液态镓在变频离心泵驱动下强制对流的流量、压力、压差及无窗靶自由液面位置和形态的实验测量结果,并分析了压力、压差及自由液面位置随流量的变化关系。结果表明,无窗靶自由液面位置主要由流体压力和流速决定。     

CFD analysis of the HYPER spallation target

KAERI (Korea Atomic Energy Research Institute) is developing an accelerator driven system (ADS) named HYPER (HYbrid Power Extraction Reactor) for a transmutation of long-lived nuclear wastes. One of the challenging tasks for the HYPER system is to design a large spallation target with a beam power of 15–25 MW. The paper focuses on a thermal–hydraulic analysis of the active part of the HYPER target. Computational fluid dynamics (CFD) analysis was performed by using a commercial code CFX 5.7.1. Several advanced turbulence models with different grid structures were applied. The CFX results reveal a significant impact of the turbulence model on the window temperature. Particularly, the k–ε model predicts the lowest window temperature among the five investigated turbulence models.     

XT-ADS Windowless spallation target thermohydraulic design & experimental setup

The objective of the European 6th framework Integrated Project (IP) EUROTRANS (EUROpean Research Programme for the TRANSmutation of High Level Nuclear Waste in an Accelerator Driven System) is to demonstrate the feasibility of transmutation of high level nuclear waste using subcritical Accelerator Driven Systems (ADS). The spallation target represents the most challenging new component in an ADS since it is the component coupling the accelerator and the nuclear core and is subjected to very high thermal load in a high radiation field. In this document the thermal hydraulic activities which led to reliable design rules for a windowless target are presented and the status of the heavy liquid metal target mock-up experiment at the KArlsruhe Liquid metal LAboratory (KALLA) are reported.     

Characterisation in water experiments of a “detached flow” free surface spallation target

In the development of accelerator driven systems, ADS, free surface lead-bismuth spallation targets are considered as promising solutions due to their possibility for compactness, their lifetime, and their ability to transport the heat deposited by the proton beam away from the spallation zone. Experiments to characterise the hydraulics of the targets are needed to allow the validation of numerical models and to improve the design. Such experiments have been performed in water on a new concept labelled “detached flow” geometry. This name was chosen because the liquid undergoes a free fall between the nozzle exit where the main free surface (that separating the void of the beam line from the liquid) is created and a second free surface downstream. The void surrounding the liquid jet plays the role of a buffer. The experiments show that a very stable main free surface with a small recirculation is obtained using this geometry thanks to the presence of the second free surface and the nozzle geometry. The experiments confirm that the level of the second free surface has no influence on the characteristics of the main free surface, improving the main free surface control. The influences of the mass flow rate and of the inlet velocity are evaluated. The free surface level rises linearly with an increase in mass flow rate. The recirculation zone is also stronger in this case. The opposite is found when the mass flow rate is decreased. For all mass flow rates studied, a stable free surface is obtained. Moreover, the outer shape of the liquid jet is similar at all mass flow rates. It is only dictated by the nozzle exit angle. Increasing slightly the inlet velocity for a given mass flow rate has a positive effect on the recirculation stability. The “detached flow” target is a promising design for ADS.     

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.