Considerations for Utilising Alternative Radioisotopes in Radioisotope Power Systems

The European radioisotope power systems (RPSs) for space, namely, radioisotope heater units (RHUs), radioisotope thermoelectric generators (RTGs) and Stirling generators are currently baselined to utilise americium-241 (
²⁴¹
Am) as their radioisotope heat source. The University of Leicester is leading the design and manufacture of the radioisotope heater unit (RHU), and of the heat source that will be common to the RTG and Stirling generators. Presently, all RPSs will incorporate a cladded Pt-Rh americium-based oxide fuel, insulation layer and outer carbon-carbon aeroshells. The current technology readiness level of European RPSs provides a greater opportunity for system adaptation. The European RTG development also enables power performance scalability. This paper hypothesises that these developing RPS designs could be adapted to incorporate shorter-lived radioisotopes compared to
²⁴¹
Am. With smaller adaptations to current RPSs designs, this could involve incorporating an additional quantity of a shorter-lived radioisotope to the present
²⁴¹
Am fuel in order to compliment the benefits of a long-lived radioisotope. With a future detailed design review, there is the potential for an RPS to solely use a shorter-lived radioisotope. This paper considers the analysis and testing campaigns that would have to be undertaken to appropriately modify the present designs.