UK Development of Deployable Nuclear Space Power Systems

This paper will present an update on the UK's dual track approach to deployable space-based nuclear power systems, seeking to develop both European Radioisotope Power Systems (RPS) and miniaturized fission Space Reactors. The UK policy landscape has rapidly evolved as the importance of the UK space sector has grown. Since 2020, the UK has seen the formation of dedicated Space Directorates in both the Ministry of Defence and the Department for Business, Energy & Industrial Strategy, and the publication of the Space Defence Strategy and Space Strategy government papers. The reliance on plutonium-238 (or 238 Pu) powered RPS systems sourced from the US and Russia prompted the European Space Agency in 2009 to instigate work to identify alternative materials, selecting americium-241 (or 241 Am) as a suitable candidate. 241 Am has a 432.2-year half-life and a thermal power density of 0.11 Wth/g. It is created in civil plutonium stockpiles as a decay product. The UK's stockpile is estimated to contain thousands of kilograms of 241 Am, more than enough to support future space exploration. The UK's National Nuclear Laboratory (NNL) has already developed an 241 Am extraction process and is currently progressing plans for a larger scale extraction facility, the PuMA-2 Laboratory, which is expected to produce up to 1000g of 241 Am per year, with a target completion date of 2026. The University of Leicester has developed designs and engineering test units of RPS. Further work is planned in ceramic pellet production and performance, electricity generation and overall system design, ready for first use by the ESA ENDURE missions in 2029, The UK has a strong heritage of reactor development for terrestrial use, especially for gas cooled reactors. The UK also has a programme to develop Advanced Modular Reactors, likely to be based on high-temperature gas reactors using Coated Particle Fuels. A parallel programme for the development of micro space reactors would benefit from this development programme. The UK Government has funded an initial programme to examine the opportunity for micro space reactor development within the UK and is currently developing a strategy for initiating a compact reactor design that would target high-power space applications including in-situ resource utilization and lunar habitats. These programmes of work are contained within an overall programme called “VULCANS”, which aims to bring together the expertise and capabilities within the UK for advanced nuclear systems. VULCANS aims to provide outline objectives for a future programme targeting the development of a range of different deployable space-based nuclear power systems.