Design and performance analysis of a 500‐W heat source for radioisotope thermophotovoltaic converters

Summary A radioisotope thermophotovoltaic (RTPV) system effectively converts the decay heat of radioisotopes into electricity via thermally radiated photons. In this work, a 500‐W thermal heat source unit including 238PuO2 radioisotope fuel, shielding material, and selective emitter is designed from the viewpoint of radiation safety, thermal performance, and overall conversion efficiency by considering various shielding materials, fuel configurations, and packing factor (PF), defined as the ratio of fuel region volume to total heat source enclosure volume including fuel cladding and shield. The design study starts with a reference cubic configuration and extends to the more complicated configurations having separate cylindrical fuels. The results of the study showed that the heat source unit design suggested here can reduce the total radiation dose, peak neutron fluence, and maximum temperature using separate cylindrical fuel rods. For example, a design having a separated 3 × 3 cylindrical fuel rod array of 30% PF increases the overall efficiency by ~39% with similar maximum temperature and radiation doses in comparison with the reference heat source unit with a single cubic module and a 10% PF. This demonstrates the importance of the proper design of the RTPV heat source unit. The suggested 500‐W RTPV having 3 × 3 cylindrical fuels reduces total radiation dose, peak neutron flux, and peak temperature in comparison with the one having a single cubic fuel. This fact makes it possible to improve the power conversion efficiency by increasing packing factor.