A molten salt community framework for predictive modelling of critical characteristics

用于包括美国和英国在内的许多国家目前正在考虑的现有和先进核燃料循环的用过的核燃料（UNF）通常在熔融盐中处理（例如，LiCl-KCl），并且比铀更活跃的裂变产物和（活化的）腐蚀产物元素作为溶解的离子（例如，Co2+、Nd 3+、Pr 3+和Cs+）。这些元素需要定期去除，以确保工艺安全，回收盐，并最大限度地减少核废料的产生。然而，存在与这些盐的热力学、物理和化学性质以及作为其在服务中的演变的函数的服务行为相关的关键知识差距-例如，裂变产物和锕系元素含量，结合蒸发/腐蚀行为，可以实时动态地改变这些熔融盐的组成，从而改变这些熔融盐的关键性质。事实上，即使是简单的相关系，在裂变产物/锕系元素的盐了解甚少。为了充分处理、回收和处置这些核废料流，以及回收铀和超铀金属等有价值的元素，需要熔盐的热化学和物理知识。然而，这种知识是有限的，特别是对于复杂的盐，例如涉及镧系元素和锕系元素的LiCl-KCl盐，氧化物污染，以及碱金属离子。（Na，Rb，Cs）和碱土（Sr，Ba）元素。在拟议的项目中，扩展了LiCl-NaCl-KCl-RbCl-CsCl-SrCl 2-BaCl 2-LnCl 3（Ln = La，Ce，Pr，Nd，Sm和Y）系统已被选为主要模型系统，以展示使用我们的开源平台（包括ML模型）加速探索结构，热力学和物理性质，基于DFT的高通量第一原理计算、MD和AIMD模拟以及使用UNIQUC和MQM模型的高通量CALPHAD建模。英国合作伙伴还将进一步研究LiCl-Li 2 O-（RbCl、CsCl、SrCl 2和BaCl 2），代表电还原剂高温处理盐，和（LiF-NaF-KF和LiF-BeF 2），美国和英国候选熔盐反应堆（MSR）燃料/冷却剂盐的代表。我们提出的美国/英国合作研究将通过实施先进的热力学模型来开发计算框架，以系统地探索临界熔融盐特性，解决与未来快核反应堆和先进的未来核燃料循环有关的熔盐方面的关键全球知识差距。拟议的研究不仅与美国NEUP Call Workscope FC-1.2直接相关，而且与相应的英国EPSRC Call和更广泛的英国民用核计划直接相关。该项目将通过提供各种开源，高吞吐量的计算方法和工具以及基础数据集，对全球熔盐社区具有真正的重要意义，以建模和设计先进的熔盐。

Used nuclear fuel (UNF) for both existing and advanced nuclear fuel cycles currently under consideration in many countries, including the US and UK, is usually processed in molten salt (e.g., LiCl-KCl), and fission product and (activated) corrosion product elements that are more active than uranium accumulate in the molten salt as dissolved ions (e.g., Co2+, Nd3+, Pr3+, and Cs+). These elements need to be periodically removed to ensure process safety, recycle the salt, and minimize nuclear waste generation. However, there is a critical knowledge gap associated with the thermodynamics, physical and chemical properties, and in-service behaviour of these salts as a function of their evolution in-service - for example, fission product and actinide content, combined with evaporation / corrosion behaviour, can dynamically alter, in real-time, the composition and therefore critical properties of these molten salts. Indeed, even simple phase relations are poorly understood in fission product / actinide containing salts. For adequate treatment, recycle, and disposal of this nuclear waste stream plus recovering valuable elements such as uranium and transuranic metals, thermochemical and physical knowledge of molten salts is required. However, this knowledge is limited, especially for complex salts, such as LiCl-KCl salts involving lanthanide and actinide elements, oxide contamination, and alkali (Na, Rb, Cs) and alkaline earth (Sr, Ba) elements.In the proposed project, the extended LiCl-NaCl-KCl-RbCl-CsCl-SrCl2-BaCl2-LnCl3 (Ln = La, Ce, Pr, Nd, Sm, and Y) system has been selected as the primary model system to demonstrate accelerated exploration of structural, thermodynamic, and physical properties using our open-source platform including ML models, high throughput DFT-based first-principles calculations, MD and AIMD simulations, and high throughput CALPHAD modeling using UNIQUC and MQM models. The UK partners will also aim to further study LiCl-Li2O-(RbCl, CsCl, SrCl2, and BaCl2), representative of electroreducer pyro-processing salts, and (LiF-NaF-KF and LiF-BeF2), representative of the US and UK candidate molten salt reactor (MSR) fuel / coolant salts.Our proposed US/UK collaborative research will develop a computational framework by implementing advanced thermodynamic models to systematically explore critical molten salt characteristics, addressing a critical global knowledge gap in molten salts relevant to future fast nuclear reactors and advanced future nuclear fuel cycles. The proposed research is not only directly relevant to the US NEUP Call Workscope FC-1.2, but also to the corresponding UK EPSRC Call and the wider UK civil nuclear programme. This project will be truly significant for the global molten salt community by providing various open source, high throughput computational approaches and tools, and underpinning datasets, to model and design advanced molten salts.