In nanogram amounts.
The amount of energy required to make economic quantities of gold would be enormous.
No one has yet made a fusion reactor that can produce even a few kilowatts of electric power as anything but short pulses, and that technology is still a long way away.
The capital cost of a 1GW nuclear plant is around $6B, in theory (the costs of meeting regulations and time uncertainties are almost incalculable).
The value of five tons of gold is around $106M, so the payback time for the $6B capital investment is close to 60 years. That’s just doing back-of-the-envelope calculations, and not counting overhead and operating costs, just capital.
About 25 ounces of gold per kilogram of gold, at 12 troy ounces per pound.
3K dollars per ounce = 75k dollars per kilogram of gold.
5K kilograms x 75K dollars =375 million dollars per year at 2.5 Gigawatthours per year.
The article says gold would be a byproduct, not a cost of operation.
All theoretical, of course
It’s *not* a fusion reactor. It’s a fission reactor. Hot neutrons that are a product of the fission reaction fuse with Hg nuclei - that’s the fusion part.