Assessment of alternative radionuclides for use in a radioisotope thermoelectric generator

Abstract

238Pu is the current fuel source for MMRTGs. This is due to favorable properties, such as high decay heat and low gamma emissions. 238Pu supplies are dwindling rapidly, necessitating the review of potential replacement isotopes for deep space missions. This work considers nine potential replacements, Ac-227, Am-241, Cf-252, Cm-244, Cs-137, Po-210, Sr-90, Th-228, and Th-170. We have assessed performance of alternatives to 238Pu by modeling the specific decay-heat and gamma spectra of several potential radioisotopes in SCALE-ORIGEN, and comparing these with 238Pu. An analysis of heat output, heat stability, safety, availability and required mass, baselined against 238Pu demonstrates that of those radioisotopes studied, 241Am has properties that make it most conducive for 238Pu replacement.