The objective of the activity is to further advance the Am241 radioisotope fuel pellet manufacturing capability, building on the success of the previous European isotope production activities. In particular, the aim is to produce the preliminary engineering design of a medium-scale (~500 grams per year) Am241 production facility, capable to provide radioisotope fuel in quantities suitable for a RHU (Radioisotope Heat Unit) flight capability.

 

Over the past decade, a new and innovative European radioisotope power technology based on americium-241 has been successfully developed. Radioisotope heater units and generators rely on the provision of americium-241 radioisotope material to provide energy. A GSTP Element 1 activity with the UK has advanced the manufacturing capability of 241AM radioisotopes. This sets up an independent European capability in radioisotope power sources that will enable a range of deep space and planetary/lunar missions that are currently impossible without outside nuclear technologies.

 

Over the past decade, a new and innovative European radioisotope power technology based on americium-241 has been successfully developed to approximately TRL4 level. The programme includes radioisotope heater units (RHU), radioisotope thermoelectric generators (RTG) and radioisotope Stirling generators (RSG). All of these devices rely on the provision of americium-241 radioisotope material to provide the thermal energy input.

 

In a previous MREP2 activity "European Isotope Production Phase 2", the first ever European space radioisotope fuel pellets were produced, using ~3 grams of Am241 manufactured at Sellafield, England. This material was used optimally in order to produce eight sub-scale Am oxide pellets, using various pressing and sintering conditions. This work established that sub-stoichiometric AmO2 was an unachievable form under practical sintering conditions and the optimum stoichiometry for Am oxide pelleting is Am2O3, but it identified the need for urgent work to develop the conditions necessary for production of full integrity (crack-free) pellets.

 

The current programme/mission focus for the radioisotope production work is Cornerstone 4 of the European Exploration Envelope Programme, specifically the HERACLES robotic mission. This requires the provision of European RHUs for launch in 2026, which will require a medium-scale (~500 grams per year) Am241 production facility to be created.

 

The proposed activity covers aspects focussed on the design of the medium-scale production facility, and technical tasks important to inform and underpin this design. The pellet manufacturing work, requiring multi-gram Am production is deferred to a follow on activity (estimated budget 2,3M?).

 

In particular in the frame of this activity the following task will be done:

 

• Produce the preliminary engineering design of a medium-scale (~500 grams per year) Am241 production facility.

• Manufacture of a small (sub-gram) quantity of americium (241) oxide primarily to enable investigation of process improvements for the flowsheet, in particular the possibility for Am-catalysed dissolution of PuO2.

• Perform a radiation dose assessment based on neutron and gamma measurement of Am241 oxide material, extrapolating by calculation/modelling to estimate the dose rates arising from RHUs and RTGs.

• Further develop stakeholder relationships towards securing access to feedstock materials and key facilities. Including also engagement of new or emerging stakeholders w.r.t. non-space applications of Am241.

• Engage in technical collaboration with other European and international partners especially in the fields of Am-oxide crystal phase stabilisation and launch safety authorisation.