Conspicuously not mentioned: what kind of design the reactor uses. Thanks engadget, 10/10 reporting.
Based on the wikipedia article, it looks like a passive decay heater attached to a bunch of sterling engines. Pretty much a souped up RTG that trades more energy output for having moving parts. Neat.
It is not based on radioactive decay but on fission, the usage of Sterling engines is correct. [1]
[...] the core of the reactor will be of solid, cast uranium-235 surrounded by a beryllium oxide reflector. This reflector focuses neutron emissions and returns their energy back into the core to minimize nuclear gamma radiation [...].
Nuclear reaction control is provided by a single rod of boron carbide which is a neutron moderator that is initially fully inserted, [...]. Once the moderator is extracted the nuclear chain reaction will start but can not be stopped completely, although the depth of insertion provides a mechanism to adjust the heat output [...].
Passive heat pipes filled with liquid sodium then transfer the reactor core heat to one or more Stirling engines, which converts heat into rotary motion that drives a conventional electric generator.
It is self-regulating (load following) to some extent so it doesn't have many moving parts. It has two main control mechanisms: a neutron absorbing control rod and a Beryllium neutron reflector.
Passive decay is still fission, it's just not artificially sped up fission :)
it's probably more complex than that. Is high speed natural decay of an artificially created or enriched heavy element natural or artificial? I'm not sure how that gets classified.
Decay is not fission. Some time fraction of decays may be spontaneous fissions but as a rule generally nobody calls decays fission reactions unless they are specifically mentioning spontaneous fission reactions.
Artificial and natural is probably not the best terminology to use [0]. What is true is that this will almost certainly contain enrichment of one or more isotopes (NASA uses Pu-238 for some of their missions).
My bad, I had assumed fission was splitting atoms by adding neutrons, but actually fission is just the "splitting" part, so both cases are indeed fission....
The fission process releases neutrons, so you effectively "add neutrons" by concentrating self-fissioning material in a small space.
To put another way:
If you increase the size of a sphere of fissionable material, its rate of "natural" decay stays the same, but more of these decays lead to neutrons triggering additional fission reactions. So doubling the size of the sphere leads to >>2x fission events due to neutrons having more fissile material to hit on the way out.
A large fission reactor is just a scaled up version of this with control rods to adsorb extra neutrons to control secondary "induced" fission.
Based on the wikipedia article, it looks like a passive decay heater attached to a bunch of sterling engines. Pretty much a souped up RTG that trades more energy output for having moving parts. Neat.