But I was trying to make a point and I can see now I didn't really communicate it very well.

98.93% of all Carbon is C12. 1.07% is C13. That adds up to 100%, at least when you round to two decimal places. The fraction of natural C14 is only a trace. There are other isotopes as well, but they are radioactive with half-lives so short they do not exist in nature. They decayed away a long time ago.

We are very good at measuring tiny quantities of these isotopes which allows us to do carbon dating, but it is very difficult to separate C14 from Carbon. Remember, all isotopes of an element are chemically identical, there is no easy way to extract one isotope from the rest. Yes, a 5g sample of C14 (in diamond form) might be a potent power source, generating electricity from the heat of radioactivity, but how do we go about isolating that much of it? We already know how difficult and expensive it is to enrich U235 to weapons or fuel grade.

The amount of C14 in the atmosphere is constant because it is continuously being replenished by cosmic ray bombardment of the CO2 in the air. The C14 is in equilibrium, that is, the amount newly created exactly equals the amount that decays away. The Carbon 14 in plants, animals, and rocks is not replenished cosmically, so it is constantly diminishing. If we need C14 in bulk, we must harvest it from the stratosphere where its concentrations are most elevated and then separate it from the other isotopes.

We CAN manufacture small quantities of C14, it can be done by using particle accelerators or nuclear fission reactors (and bombs!). It involves using great energies to add or subtract neutrons from other atomic nuclei. C14 is slightly heavier than C12, so maybe we can use centrifuges or membranes or ionization like we do with Uranium. But I suspect the amounts are tiny, and the costs enormous.

Perhaps we can harvest or make C14 and compress it into diamond so it can be used as a compact, long-lived thermoelectric battery. But there may be many other radionucleides that can do the job better.

C14 Buckyballs. What a concept.