A strategic step forward: NAAREA, its laboratory IMSLab and the JRC develop an innovative proliferation-resistant pyrochemical method of synthesizing NaCl-PuCl₃ salt

NAAREA, a French startup that is developing a fourth-generation molten salt fast neutron microreactor, has been working with the European Commission’s Joint Research Centre (JRC) since 2024 on the synthesis of NaCl-PuCl₃ salt to look at the safety along the development of liquid fuel for molten salt reactors. This research is paving the way for the development of a new energy sector capable of producing decarbonized, safe and decentralized electricity, while contributing to the reduction of final waste thanks to the advanced processing of spent fuel from pressurized water reactors.

NAAREA is developing a fourth-generation nuclear microreactor, the XAMR®, based on an innovative technology: the use of liquid fuel in the form of molten salts. More specifically, it uses sodium chloride (NaCl), in which actinides in the form of plutonium chloride and uranium chloride are dissolved. In the absence of an industrial sector to supply fuel for these innovative technologies, the synthesis of fuel salt is a key step for validating the project’s feasibility. This involves developing a reproducible synthesis method to produce a pure fuel salt containing fissile materials.

Since 2024, through its joint laboratory – the Innovation Molten Salt Lab (IMSLab) – with the CNRS (French National Centre for Scientific Research) and Paris-Saclay University, NAAREA has been working with the European Commission’s Joint Research Centre (JRC) on the synthesis of NaCl-PuCl3 salt. This research is key to the development of a liquid fuel that can be used in molten salt reactors, and more specifically NAAREA’s XAMR® nuclear microreactor. The JRC is the science and knowledge service of the European Commission. As such with its expertise and research infrastructures, the JRC provides independent, evidence-based knowledge and science, supporting EU policies to positively impact society.

The focus of this collaboration is on validating a proliferation-resistant method of synthesizing NaCl PuCl3 salt from plutonium oxide (PuO2), via a pyrochemical process, as well as experimentally determining fundamental data related to this fuel. This strategic method, proposed by NAAREA, is based on a process that involves bubbling gas through a mixture of NaCl and PuO2, brought to a high temperature. This process is implemented thanks to specific experimental equipment developed and operated by the JRC.

At laboratory scale, this work demonstrated that bubbling a gas through a mixture of NaCl and PuO2 made it possible to quantitatively dissolve the plutonium oxide and thus form a plutonium chloride-based salt. Additional characterization stages will follow to confirm the purity of the fuel salt and determine its fundamental properties, which is vital to the development of the molten salt reactor industry.

This experimental validation work with plutonium represents an initial step in the fuel cycle strategy developed by NAAREA, validating the synthesis method’s feasibility and potential. Process engineering and scale-up tests will be carried out, in particular in the short term on simulants of radioactive materials in the experimental facilities of the I-Lab, NAAREA’s 2,400 m2 test facility located in Cormeilles-en-Parisis.