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To support the development of a Radioisotope Power Source (RPS) for exploration missions into deep space based on 241Am, the European Commission’s Joint Research Centre (JRC) has recently launched an exploratory research project, scheduled for a period of two years. It aims at finding innovative solutions for higher performance, safety and reliability of such a device. In addition, it will serve as a start-up platform for this field of research and enable identification of research areas, where JRC can significantly complement and support the already existing activities in Europe. The project is divided into several subtasks and will investigate –safety related properties of americium (oxide) as a heat source, – compatibility of americium compounds with cladding and structural materials, –properties of alternative americium compounds, –properties of advanced thermoelectric materials. The new exploratory research project will be introduced together with an overview on the available facilities and capabilities of JRC in this domain. Alternative americium forms with potential improved stability versus the oxides are discussed and innovative thermoelectric materials based on actinides are introduced.

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.