Investigation on the use of Americium Oxide for Space Power Sources: Radiation Damage Studies

¹ European Commission, Joint Research Centre, Directorate G – Nuclear Safety & Security, P.O. box 2340, 76125 Karlsruhe, Germany
² European Commission, Joint Research Centre, Directorate G – Nuclear Safety & Security, P.O. Box 2, NL-1755 ZG Petten, The Netherlands

Email: thierry.wiss@ec.europa.eu
Email: elio.dagata@ec.europa.eu

Abstract

Within Europe ²⁴¹Am is a feasible alternative to ²³⁸Pu that can provide a heat source for radioisotope thermoelectric generators (RTGs) and radioisotope heating units (RHUs) to be used in Electrical power sources used in outer planet missions. In the EPSO-SPACE* project developed as an exploratory research at JRC, a new type of nuclear power source, to provide heat and electricity for deep space missions is considered. It will consist of a ²⁴¹Am based compound with aerogel thermal insulation and thermocouples in close contact with the heat source. The assembly is inside an iridium encapsulation to withstand all relevant accident scenarios. The design will be modular and combinable for required electrical output.

Several candidate Americium compounds will be investigated for chemical stability at high temperature and for self-irradiation damage. New thermo-electric converter materials containing actinides will be assessed, and a robust encapsulation designed. Safety analyses will be performed including launch explosion and re-entry accidents. The research will conclude in a conceptual design of a prototype power source. In the first part of this study, americium dioxide will be considered from the point of view of its chemical durability and of its behavior against radiation damage and helium formation, two aspects to be carefully investigated due to the high alpha-activity of the americium. Transmission electron Microscopy (TEM) and helium thermal desorption spectrometry (TDS) experiments will be described and results on aged (more than 30 years) AmO₂ reported. Some comparison with ²³⁸PuO₂ based RTG’s will be discussed.