Actinide nitrides for Gen IV systems, remaining chemical issues and recyclability

Research Project, 2019 – 2022

Using plutonium and minor actinide fuels is a requirement for a Gen IV system to perform according to the promised advantagues. These include higher utilisation of the energy in the fuel, as well as the more proliferation safe and less radiotoxic ultimate wastes. Several such types of fuels exist. In this project, we will focus on nitride fuels due to their increased safety during operation and enhanced economy, due to the increased fissile density, compared to oxides. We will focus on nitrides containing thorium (for scientific reasons), uranium, plutonium and americium in various ratios. Since the minor actinides are highly radiotoxic, there are few production routes to select from and a promising one is the sol-gel process. We will investigate this route for fabrication of low carbide containing nitrides, as well as in detail investigate the observed preference for carbide formation in e.g. zirconium as opposed to the pure plutonium nitride. Materials investigation will comprise e.g. EXAFS as well as XRD and SEM of the produced fuels. Once produced the detailed mechanism as well as potential optimisation of the dissolution routes for the fuels will be investigated. This dissolution liquor will be used as feed to the already developed CHALMEX separation process. A difficulty is the use of inert matrix fuels such as (Pu,Zr)N where the high amount of Zr will affect the recycling process. The performance in the CHALMEX process will be investigated to show a proof or concept.