Development of versatile liquid metal testing facility for lead-cooled fast reactor technology

液态金属冷却核反应堆是一种先进的核反应堆设计，其中主要冷却剂是液态金属，如钠、铅或铅-铋混合物。液态金属良好的传热性能，以及液态金属反应堆可以在常压和很高的温度下运行，是液态金属冷却反应堆相对于水冷反应堆设计的主要优势。这些优点导致反应堆设计更小、更安全，特别适合于小模块结构。最初为船舶推进而开发的液态金属冷却核反应堆目前正在研究用于发电。特别是，第四代国际论坛确定的六个核反应堆设计中，有两个是液态金属反应堆：钠冷却快堆和铅冷却快堆。目前的研究重点是铅冷却快堆技术。铅冷却核反应堆将部署在小型模块化单元中，其特点是寿命长、预制的堆芯可以运行数年，然后才能被替换，从而使这些反应堆也适用于不打算建设自己核基础设施的新兴国家和发展中国家。液态铅良好的热传递能力，加上其高沸点，确保了反应堆关闭后的衰变热可以通过完全被动的方式安全地消散，从而产生了特别安全的核反应堆设计。铅的密度也非常高，因此可以很好地屏蔽伽马辐射，这对保护操作员和环境是一个额外的好处。与钠不同，钠与空气接触时会燃烧，与水接触时会爆炸，铅与空气或水都不会发生明显的反应，从而使系统设计更简单、成本更低，并使核电站运行更安全。目前，铅冷却核反应堆技术的主要缺点是对暴露在代表核反应堆运行温度的液态铅中的材料的侵蚀和腐蚀的了解非常有限。这就是本研究旨在解决的知识鸿沟：在核反应堆运行条件下，将在液态铅中进行冲刷和腐蚀试验，以确定最有希望实现反应堆结构部件的材料。实验装置的高保真CFD模拟将首先协助实验装置的设计，然后提供关于局部流场和热场的缺失信息，这对于充分理解实验数据的含义并将实验结果更广泛地应用于铅冷却反应堆的腐蚀/侵蚀分析是必要的。此外，本研究还将开发基于超声波的成像技术来检测运行期间的反应堆内部部件。事实上，液态金属是不透明的，因此传统的成像技术不适用。定期检查反应堆内部部件的可能性对于安全和有利可图的运行是必不可少的。

Liquid-metal-cooled nuclear reactors are advanced nuclear reactor designs where the primary coolant is a liquid metal, such as sodium, lead or a lead-bismuth mixture. The excellent heat transfer properties of liquid metals, and the possibility to operate liquid metal reactors at ambient pressure and very high temperature, are the main advantages of liquid metal cooled reactors with respect to water-cooled reactor designs. These advantages result in smaller and much safer reactor designs, particularly suited for small-modular construction.Originally developed for marine propulsion, liquid-metal-cooled nuclear reactors are currently being investigated for power production. In particular, two out of the six nuclear reactor designs identified by the Generation IV International Forum and currently being researched for near-term commercial application are liquid metal reactors: the sodium-cooled fast reactor and the lead-cooled fast reactor.The present research study, in particular, is focused on the lead-cooled fast reactor technology. Lead-cooled nuclear reactors will be deployed in small and modular units featuring long-life, pre-manufactured cores that can run for several years before being replaced, thus making these reactors also suitable for emerging and developing countries that do not plan to build their own nuclear infrastructure. The excellent heat transfer capabilities of liquid lead, together with its high boiling point, assure that decay heat after reactor shutdown can be safely dissipated with entirely passive means, thus resulting in a particularly safe nuclear reactor design. Lead is also very dense and therefore a good shield against gamma radiations, which is a bonus for protecting the operators and the environment. Unlike sodium that burns in contact with air and that can explode in contact with water, lead does not react significantly with either air or water, allowing simpler and cheaper system design and a safer plant operation.Currently, the main drawback of the lead-cooled nuclear reactor technology is the very limited knowledge of erosion and corrosion of materials exposed to liquid lead at temperatures representative of nuclear reactor operation. This is the knowledge gap that the present research aims to address: erosion and corrosion tests will be carried out in liquid lead at nuclear reactor operating conditions to identify the most promising materials to realize the reactor structural components. High-fidelity CFD simulations of the experimental setup, will first assist with the design of the experimental facility and then provide the missing information on the local flow and thermal fields, necessary to fully understand the implications of the experimental data and apply the experimental findings more widely to corrosion/erosion analysis of lead-cooled reactors.Additionally, the present research will also develop an imaging technology based on ultrasounds to inspect the reactor internals during operation. Liquid metals, in fact, are opaque and conventional imaging techniques therefore not applicable. The possibility to periodically inspect the reactor internals is essential for safe and profitable operation.