A top to bottom look at green energy

That nugget produces tiny amounts electricity and has a half life in the hundreds to thousand years

Let me clear up your understanding of radioactive half life. Did you know that bananas contain a good amount of radioactive potassium 40? But you can safely eat bananas. If you ate the same amount of Cobalt 60 in your hand it would kill you. Both radioactive so what is the difference. K-40 has a half life of 1,250,000,000 years, Co-60 has a half life of 5.6 years (IIRC). One is death, the other not. The shorter the half life the more dangerous a material is, generally.
This is why the radioactive waste will kill people a hundred thousand years from now is mostly BS. Reactor waste is a mix of elements. Some with a very short half life and thus very dangerous. For example Ba-139 is present in that waste and it has a half life of 83 minutes. A speck od Ba-139 would kill you right there. But you can generally assume that almost all of an isotope is gone in 5 half life's. Meaning that in 8 hours that Ba 139 is gone. The dangerous short half live stuff is gone in 100 years. !000 years from now you half long half life material that isn't that hazardous and 10,000 years from now you can figure what is left. Stuff with a half life longer than 2000 years.No as to your carbon enclosed hot stuff, it would not do a thing for a gram of Ba 139, it would still kill you right there. For a gram of Th-230 you would be fine, it has a HA of 75000 years. But you's get very little energy from it.