随机填充球床通道内氦气流动特性实验研究

在聚变堆氦冷固态包层氚增殖区,球床通道内氦气流动压降特性对泵功率的设计具有重要意义。以氦冷固态包层氚增殖区为背景,研究了氦气流速、球床颗粒直径及球床通道长度对球床通道内氦气流动压降特性的影响。实验段采用20 mm×20 mm×500 mm的矩形通道,实验中氦气流速为0.1～0.6 m/s,球床颗粒直径为0.5、0.8、1.0、1.5、2.0 mm。实验结果表明,压降与氦气流速以及球床通道长度呈正相关,与球床颗粒直径呈负相关。对比Ergun关系式发现,在球床颗粒直径较小时,Ergun关系式预测值低于实验值,这主要是由于氦气可压缩性的影响。通过动量方程,理论推导出经可压缩性修正的Ergun关系式,结果发现修正后的Ergun关系式预测值与实验值符合良好。本研究为氦冷固态包层氚增殖区设计提供了数据支撑,为球床通道内流动特性的数值模拟提供了验证手段。     

氚增殖剂球床组件堆内辐照物理热工计算分析

为验证在中国先进研究堆(CARR)内进行国际热核聚变实验堆(ITER)氚增殖包层模块(TBM)辐照实验的可行性和安全性,进行了氚增殖剂球床组件堆内辐照物理及热工计算分析。氚增殖剂包层模块主要是固态氚增殖剂陶瓷球床。本文采用Monte Carlo粒子输运模拟程序对氚增殖剂球床进行堆内建模,计算球床的中子注量率、能量沉积和产额,得到不同功率下球床的中子注量率、发热功率和产氚速率以及球床组件引入反应堆的反应性。根据物理计算得到的组件各部件发热情况建立热工计算一维模型,通过更改反应堆功率得到满足实验要求的工况并采用三维程序进行验证。物理与热工计算分析的结果表明,在反应堆运行功率为20 MW的工况下球床组件各部件的温度均不超过限值。     

高温气冷堆堆芯实时热工水力模型

为建立适用于球床式高温气冷堆核电厂的模拟机,采用一体化仿真支撑平台vPower建立高温气冷堆堆芯的实时热工水力模型,利用流体网络求解氦气流道的流量与压力分布及传热网络求解球床燃料区、石墨反射层区与碳砖区的温度分布,实现整个氦气流场与固相温度场的实时、耦合计算。模拟100%额定负荷和50%额定负荷2个稳态工况和入口温度阶跃和流量阶跃2个动态过程。稳态工况与设计参数的定量对比以及动态过程的定性分析表明,该模型具有较好的适用性。     

球床模块堆停堆后自然对流传热特性数值研究

对冷却流体在球床模块堆内燃料颗粒填充区域中的流动和传热过程进行了研究.数值模拟突然停堆后燃料颗粒区在温差作用下的自然对流过程,分析了瑞利数Ra对燃料填充区域内流场、温度场和局部努塞尔数Nu以及壁面摩擦阻力系数的影响.计算结果表明:当球床模块堆突然停堆时燃料填充区域可形成加热壁面流体上升流动、冷却壁面下降流动的自然循环流动;随着Ra数增大,回流中心向上移动;沿轴向壁面局部Nusselt数和摩擦阻力系数存在极值,并且极值点随Ra数增大而向上移动;与氮气相比,氦气作为冷却介质停堆后具有更均匀的堆芯轴向温度分布.     

中国氦冷固态增殖剂实验包层模块材料研究进展

在未来核聚变反应堆中,为补充氚的消耗,需要在核聚变堆的包层中进行氚的在线增殖,以维持核聚变反应的持续进行。为验证这一关键技术,在国际热核聚变实验堆(ITER)上开展了ITER TBM计划(实验包层项目)。作为ITER计划成员方之一,中方以中国氦冷固态增殖剂实验包层模块(HCCB TBM)概念参与ITER TBM计划。HCCB TBM现今进入初步设计阶段,而材料的制备技术和性能数据是支撑其结构设计、安全分析和服役工况评估的基础。本文综述和分析了HCCB TBM结构材料低活化铁素体/马氏体钢(RAFM钢)与功能材料氚增殖剂和中子倍增剂的研究现状,并对这些材料下一步的研究方向进行了展望。     

硅酸锂球床传热传质特性与吹扫气体流动的DEM-CFD耦合模拟

氦冷固态增殖包层是中国聚变工程实验堆（CFETR）的3种候选包层概念之一,氚增殖球床是包层的核心部件,采用硅酸锂颗粒作为氚增殖材料。球床结构对氚在球床内的输运行为及流动和传热均有重要影响。本文基于离散单元法（DEM）生成了满足氚增殖球床填充率要求的随机堆积结构,通过CFD计算获取了球床结构下氚在吹扫气体内的等效扩散系数及吹扫气体的流动特性,包括速度分布、压力分布及进出口压降;开展了外加热流及有内热源两种工况下球床等效导热系数的模拟。计算结果表明,球床结构下氚在吹扫气体内的等效扩散系数为二元气体扩散系数的40%;受球床结构影响,球床内存在流动迟滞区,壁面出现流动加速;拟合得到Ergun方程的黏性阻力系数C1=87;有内热源工况下的球床等效导热系数低于外加热流工况下的球床等效导热系数。     

聚变堆交叉冷却固态包层中子学设计优化

针对聚变堆固态包层设计路线,提出了一个交叉排列氦冷固态包层概念。设计采用Be、Li₂TiO₃分层球床。两种尺寸的氦气冷却管道交叉排列,分两个回路同时冷却,以增加系统安全可靠性。分析比较了4种⁶Li富集度布置方案。结果表明：径向远离第一壁降低⁶Li富集度较为合理,靠近第一壁的增殖层⁶Li富集度不能过低,以减少长期运行中Li的消耗对氚增殖性能的影响。借助蒙特卡罗程序MCNP建立11.25°对称模型,全堆包层氚增殖率为1.176,包层寿期内产氚性能稳定,在包层寿命运行时间内的燃耗分布相对均匀。     

聚变堆混和球床包层中子学和热工水力特性研究

在聚变堆初步概念设计的基础上，针对固态包层设计路线，提出了一个先进的氦冷固态包层概念。设计采用Be₁₂Ti和Li₂TiO₃陶瓷小球混和球床，物理和化学相容性好；采用SiC作为结构材料，提高耐高温性能及氦气出口温度。计算结果表明：选择Be₁₂Ti和Li^₂TiO₃球体积比在2和4之间较合理；在Be₁₂Ti和Li₂TiO₃球体积比为3时，⁶Li富集度取30％~80％较适宜；球床的最高温度低于材料的温度限值，温度分布合理均匀。该方案可较大程度提高热效率和改善中子学以及氚增殖性能。     

ITER中国液态锂铅实验包层模块氦气冷却系统初步设计研究

氦气冷却系统是ITER中国液态锂铅实验包层模块(DFLL-TBM)在ITER装置内进行实验的重要辅助系统.根据ITER运行时的热工条件、安全要求、空间要求,分析了DFLL-TBM氦气冷却系统的功能,确定氦气冷却系统的设计原则和要求,在此基础上给出氦气冷却系统的初步设计方案和设备布置.该氦气系统的特点体现在:双功能,即有宽的裕量满足SLL-TBM和DLL-TBM实验;两条氦气回路共享压力控制单元和氦气净化子系统;旁路设计调节TBM和热交换器氦气的出口温度.     

基于单元体理论的球床堆积结构与传热算法研究

以球床堆积结构为分析对象,利用离散单元法(DEM)进行数值模拟,实现球床的堆积并取得良好结果。随机堆积的球床中极少有颗粒达到最密集堆积状态,在靠近球床壁面处孔隙率迅速增加。对整个球床进行Voronoi单元体划分以分析球床局部结构,在大空间区域处堆积具有随机特点,在靠近壁面处呈现有序堆积特征。对每个单元体建立热平衡方程,实现对球床局部温度场的仿真,温度场计算结果与实验结果符合得很好。     

Conceptual design of Tritium Extraction System for the European HCPB Test Blanket Module

The HCPB (Helium Cooled Pebble Bed) Test Blanket Module (TBM), developed in EU to be tested in ITER, adopts a ceramic containing lithium as breeder material, beryllium as neutron multiplier and helium at 80 bar as primary coolant.In HCPB-TBM the main function of Tritium Extraction System (TES) is to extract tritium from the breeder by gas purging, to remove it from the purge gas and to route it to the ITER Tritium Plant for the final tritium processing.In this paper, starting from a revision of the so far reference process considered for HCPB-TES and considering a new modeling activity aimed to evaluate tritium concentration in purge gas, an updated conceptual design of TES is reported.     

Non-linear failure analysis of HCPB Test Blanket Module

For the European Helium Cooled Pebble Bed Test Blanket Module (HCPB-TBM) the reduced activation ferritic martensitic (RAFM) steel EUROFER 97 is selected as a structural material. During operation the TBM will be subjected to complex thermo-mechanical loadings which yield at certain positions of the structure to stresses beyond the design limits of the structural material. Preliminary structural analyses of the TBM have shown critical behavior in several key points of the structure. An improved design has been proposed and in order to identify and assess the problematic positions in the improved version of the TBM a non-linear failure analysis is performed, for which a coupled deformation damage model developed at KIT for RAFM steels and recently implemented in the finite element code ABAQUS is used. The thermal loads in the form of non-homogeneous temperature fields distributions are obtained from a thermal analysis performed using the finite element code ANSYS on the same structure. Importing the temperature fields into the finite element code ABAQUS and applying the remaining loads – coolant internal pressure and structural boundary conditions – non-linear simulations are conducted taking into account the ITER-typical cyclic nature of the loading. The simulation results are evaluated and discussed considering ratcheting and damage at most critical highly loaded areas of the structure.     

Three-dimensional dual-flow fields analysis of the DFLL TBM for ITER

This paper concerns the design calculations and performance evaluation of the Dual Function Lithium Lead Test Blanket Module (DFLL TBM) for ITER. Detailed three-dimensional dual-flow field calculations of helium gas and lithium lead (LiPb) have been performed for the DFLL TBM. The commercial Computational Fluid Dynamics (CFD) code FLUENT based finite volume method Navier–Stokes solver capable of solving conjugate flow and heat transfer between dual-flow field and structure is used. The CFD calculations are conducted directly in the CAD model using the CATIA code that allows preserving the geometrical details. The computational results show that the current TBM design is reasonable under the ITER normal condition. The detailed dual-flow fields, which include temperature, velocity, pressure and heat transfer of liquid LiPb and helium gas, are presented to optimize and improve the design of DFLL TBM system for ITER, and to supply more robust database and make a significant joint contribution to the future TBM testing in EAST and ITER.     

The fundamental role of fluid dynamic analyses in the design of the solid EU Test Blanket Module

In the frame of the activities of the European Test Blanket Module Consortium of Associates, the Helium Cooled Pebble Bed Test Blanket Module (HCPB TBM), the so-called solid TBM, is developed in Karlsruhe Institute of Technology (KIT). In the EU experimental strategy, a series of 4 different HCPB TBMs will be connected to the dedicated equatorial port n.16 during the ITER lifetime. The ITER TBM program has to provide DEMO relevant experimental data for the main functions of the blanket modules of a future fusion reactor.The preliminary thermo-mechanical design assessment of the TBM box (based on transient, steady state and accidental analyses) has been presented. All along the design assessment phase the fluid dynamic analyses play a fundamental role for the TBM sub-components, the Breeder Units (BUs) and the manifolds (MF) stages. This paper highlights the methodology implemented for the Computational Fluid Dynamic (CFD) analyses in the TBM design life cycle, and presents the results and the impact on the overall performance evaluation of the HCPB TBM. The following models are presented in detail: the CFD model of the TBM First Wall and its application to a reduced scale First Wall, the 3D CFD model of the BUs, and the thermo fluid dynamic modelling of the manifold systems.     

Preliminary safety analysis of ex-vessel LOCA for the European HCPB TBM system

Ex-vessel loss of coolant accident caused by a double-ended pipe break of the helium coolant system inside port cell is considered as one of the most critical accident for the European Helium Cooled Pebble Beds Test Blanket Module (HCPB TBM) system. The resulting rapid helium blow-down causes an immediate block of the TBM cooling, which requires a prompt plasma shutdown. Even after the plasma shutdown the temperature can increase over the design limit and the accident sequence can lead up to a break of the TBM box protection after the failure of different protection systems. Thus air ingresses in the vacuum vessel from the damaged TBM system and steam from the surrounding ITER blanket and divertor structures. The evaluation of this sequence is very important for the definition of the correct protection strategy of the system. To consider all these different events a methodology has been developed in KIT combining different codes for a complete analysis of the accident. In particular, this paper shows an application of MELCOR code to model beryllium–steam reaction in a particular accidental sequence for the long term cooling.     

Design update,thermal and fluid dynamic analyses of the EU-HCPB TBM in vertical arrangement

In the frame of the activities of the EU Breeder Blanket Programme and of the Test Blanket Working Group of ITER, the Helium Cooled Pebble Bed Test Blanket Module (HCPB TBM) is developed in Forschungszentrum Karlsruhe (FZK) to investigate DEMO relevant concepts for blanket modules.The three main functions of a blanket module (removing heat, breeding tritium and shielding sensitive components from radiation) will be tested in ITER using a series of four TBMs, which are irradiated successively during different test campaigns. Each HCPB TBM will be installed, with a vertical orientation, into the vacuum vessel connected to one equatorial port. As the studies performed up to 2006 in FZK concerned a horizontal orientation of the HCPB TBM, a global review of the design is necessary to match with the new ITER specifications.A preliminary version of the new vertical design is proposed extrapolating the neutronic analysis performed for the horizontal HCPB TBM. An overview of the new HCPB TBM vertical designs, as well as the preliminary thermal and fluid dynamic analyses performed for the validation of the design, are presented in this paper. A critical review of the results obtained allows us, in the conclusion, to prepare a plan for the future detailed analyses of the vertical HCPB TBM.     

Progress in the KIT approach for development of the HCPB TBM stiffening plate feasibility mock up fabrication

Sub-component manufacturing and assembly concepts for the fabrication of the Helium Cooled Pebble Bed Test Blanket Module have been developed since more than one decade in the KIT. In the present design the structure of the HCPB TBM can be sub-divided into three key components: (i) TBM box, (ii) stiffening plates and (iii) the breeder zone. The present fabrication and assembly routines is based on the assumption that each of the aforementioned sub-components can be assembled in parallel and independently before assembling the TBM. Therefore the procedures to fabricate these sub-components can be addressed in independent tasks. This paper shows the results of the KIT/industry collaboration with the final goal to develop a set of preliminary welding procedure specifications (pWPS) for the assembly of the HCPB TBM stiffening plate. Recently a promising set of draft pWPS could be identified in medium scale fabrication experiments. This paper recalls the results of qualification routines according to ISO 15614-11 (RCC-MR Edition 2007, RS 3570) in order to verify the parameters.     

球床包层聚变—裂变混合堆热工安全分析

球床包层混合堆与板状元件包层混合堆相比较，前者在核燃料生产和安全方面可能具有更多的优越性。本应用ＴＨＥＲＭＩＸ程序和辅助程序对我国开发的托卡马克堆芯氮气冷却球床包层聚变－裂变合堆的包层进行了热工计算。计算中考虑了不同的燃料球材料及稳态，卸压和断流事故工况。计算结果表明，只要选用合适的燃料球材料和设置适当的控制保护系统，具有快速卸料罐的托卡马克堆芯氦气包层聚变－裂变混合堆的概念设计在安全上的可行的。     

Experimental investigation on the possible techniques of pebbles packing for the HCPB Test Blanket Module

The Helium Cooled Pebble Bed Test Blanket Module (TBM) features a structural box that consists of the first wall, two caps and a stiffening grid. Inside the stiffening grid the breeding units (BUs), consisting of the beryllium and lithium ceramic pebble beds and cooling plates, are accommodated. The BUs are closed by the BU back plates and several structural plates of the manifold system as well as the TBM back plate consequently the BUs may not be accessed directly after the assembly of the TBM box; however, access is possible through dedicated penetrations in the TBM caps. According to the current manufacturing strategy, the assembly of the TBM structural sub-components is based on several welding processes which require post-welding heat treatments (PWHT) at temperatures which exceed the temperature limit of the beryllium pebbles. For that reason the beryllium pebble beds will be packed after the TBM box is assembled and heat treated. The packing of the BUs will be performed using a small-diameter (5 mm) tube that will be inserted into some penetrations in the TBM caps. It is expected that the lithium ceramic pebbles can withstand the high temperatures of the PWHT (this assumption needs to be verified) therefore the current strategy is to pack the ceramic pebble beds during the TBM box assembly. This study experimentally demonstrates the packing procedures for the beryllium beds using a full-scale Plexiglas mock-up as well as the optimization of the packing process by dedicated measures such as vibrating and tilting of the mock-up. In addition the impacts of the experimental results on the TBM design are summarized and the paper is concluded by proposing a packing strategy that can be used to achieve a packing factor of 63.6%.     

Numerical analysis of dual-flow fields in Mini-TBM for Chinese LiPb experimental loop Dragon-IV

It is difficult to measure the detailed dual-flow fields of liquid metal lithium lead (LiPb) and helium gas in Mini-Test Blanket Module (TBM). Three dimensions numerical analysis of the LiPb and helium gas flow and heat transfer in Mini-TBM therefore has been curried out using the Computational Fluid Dynamics (CFD) code FLUENT. The detailed dual-flow fields, which include temperature, velocity, pressure and heat transfer of liquid LiPb and helium gas, are presented to support for the test of Mini-TBM, and to supply more robust database and make a significant joint contribution to the future TBM testing in EAST and ITER, and also optimize and improve the design of Dual Function Lithium Lead TBM (DFLL-TBM) system for ITER.