Liquid metal-cooled fast reactor instrumentation technology development - CFD model development and validation

英国政府认为核能在国家能源结构中发挥着重要作用，以建立一个安全、环保和多样化的能源组合，满足未来的能源需求。目前，英国西南部有两座反应堆正在建设中，还有一些正在开发中。为了确保核能的安全性和经济竞争力，第四代国际论坛（Generation IV International Forum， GIF）已经成立，该论坛选择了六种先进的核反应堆设计作为其成员国发展的重点。其中两种采用液态金属作为主回路冷却剂，即钠冷快堆（SFR）和铅冷快堆（LFR）。在英国，BEIS最近支持了8个先进模块化反应堆（amr）的可行性研究，其中3个是液态金属冷却快堆（LMFRs）。广义上讲，LMFR中的知识缺口和建模挑战与两个事实有关。首先，由于金属液态的普朗特数极低，金属液态的换热特性与传统流体（空气和水）的换热特性明显不同，这使得传统的湍流模型在大多数情况下都是无效的。其次，特殊的池型设计产生了此类反应器所特有的自然循环、分层等热水力现象。此外，由于测量液态金属中的流场和热场存在困难，因此缺乏基准数据。该提案是为了响应EPSRC对“英国/美国NEUP 2019”的合作研究呼吁而制定的，旨在解决上述挑战。该联合研究项目将侧重于开发液态金属冷却快堆的仪器技术和相关建模。美国合作伙伴将进行实验调查，而英国合作伙伴将开发用于高保真建模和共轭传热分析的计算工具。对液态金属的停滞和分层流动进行高保真大涡模拟（LES），是对物理实验的补充，为湍流和工程模型的开发提供有价值的详细数据，有助于推进对这类复杂流动现象的认识。接下来将使用实验和数值数据对“传统”CFD模型进行改进和验证，以开发对湍流模型和模拟液态金属流动的数值方法的新理解。最后，基于新近发展的新型粗网格CFD和浸入边界法，建立了具有创新意义的钠-超临界- co2紧凑型印刷电路换热器（PCHE）的共轭传热模型。如果成功，它们代表了具有高度复杂几何和物理的热交换器建模的重大进步，并可用于有效地协助此类系统的设计和优化。

The UK government considers nuclear energy to play an important role in the country's energy mix to establish a secure, environmentally friendly and diverse energy portfolio and meet the future energy demand. There are currently two reactors being built in the southwest of the UK and a number of others currently under development. In order to ensure nuclear energy safer and economically competitive, the Generation IV International Forum (GIF) has been formed, which has selected six advanced nuclear reactor designs to be the focus of the development by its member countries. Two of them use liquid metal as primary-circuit coolant, i.e., the sodium-cooled fast reactor (SFR) and the lead-cooled fast reactor (LFR). In the UK, BEIS has recently supported feasibility studies for eight advanced modular reactors (AMRs), three of which are Liquid Metal-cooled Fast Reactor (LMFRs). The knowledge gaps and modelling challenges in LMFR are broadly speaking related to two facts. Firstly, the heat transfer characteristic of liquid metal is markedly different from that of the conventional fluids (air and water) due to the extremely low Prandtl number, which makes the conventional turbulence models invalid under most conditions. Secondly, the special pool-type design gives rise to thermal hydraulic phenomena including natural circulation and stratification, which are unique for such reactors. Additionally, there is a lack of benchmarking data due to the difficulties associated with the measure of the flow and thermal fields in liquid metal. This proposal, developed in response to the EPSRC's collaborative research call on 'UK/US NEUP 2019', is aimed at addressing the above challenges. This joint research project will focus on developing instrumentation technology and associated modelling for liquid metal cooled fast reactor. The US partners will carry out experimental investigations, while the UK partners will develop computational tools for high fidelity modelling and conjugate heat transfer analysis. High fidelity large eddy simulation (LES) of stagnation and stratification flow of liquid metal will be carried out to complement physical experiment to provide valuable detailed data for turbulence and engineering model development, as well as to help in advancing the knowledge in such complex flow phenomena. This will be followed by refinement and validation of the 'conventional' CFD models using experimental and numerical data to develop new understanding of turbulent models and numerical methods for the simulation of liquid metal flows. Finally, a highly innovative conjugate heat transfer model of the sodium-to-supercritical-CO2 compact printed circuit heat exchanger (PCHE) will be developed based on the novel coarse-grid CFD recently developed and the immerse boundary method. If successful, they represent a major advancement in modelling of heat exchangers with highly complex geometry and physics and can be used to assist the design and optimisation of such systems effectively.