Hi phil

The news is fascinating from the deep space angle, especially if the thermal management issues aren't too onerous. If the thing glows red-hot then it might get tricky, but from the description it seems much more efficient than the 20% of Carnot Limit efficiency that current thermoelectrics struggle to achieve. I've always wanted a nuclear battery I can wear on my belt ;-)

As for the Lonnie Johnson Converter that has huge potential in current thermal powerplants - coal or nuclear. Getting the heat-sink down in output temperature to maximise efficiency will be quite a trick - WOW Energies ethane Closed Cycle turbines might help extract more energy out of the coolant stream, if the Converters aren't economical to use.

In space the situation is a lot trickier. To maintain huge temperature differentials requires massive radiators, so a compromise might be needed on efficiency ~ say radiators putting out at 600 K, while the heat source is at ~ 1400 K. Still 48.6% efficiency, which is at least double what current space reactors are dreaming of doing - the old TOPAZ designs got just ~ 8% AFAIK.

Good news in many ways. I hope both designs pan out, though only Lonnie Johnson's has experimental systems actually producing data presently. Combined they might just make deep space ion-drives easy to make.