According to papers filed with the Blue Ribbon Commission, the current research involves faster and simpler processes for separating uranium and plutonium from other fission products in spent fuel and from minor elements like americium and curium.
They seemed unaware that they were mixing highly enriched uranium, more susceptible to spontaneous fission than normal power plant fuel, and they put in 16 kg instead of 2.
Thermoelectric coupling uses heat from the decay of a radioactive fuel (as opposed to the full-scale nuclear fission which powers a reactor on Earth) as its energy source.
Reactors that exploit nuclear fission (in which energy is generated by splitting uranium atoms) have produced thousands of tonnes of spent fuel and other radioactive by-products.