Place mercury in the reactor. After a large amount of work, only a tiny portion of gold is created.
Decontaminate the resulting gold. This is harder than it sounds because you can't separate out non-radioactive gold from radioactive gold using purely chemical methods.
It should be obvious from this process that it currently costs much more money to create non-radioactive gold than you could ever earn by selling the gold. Creating gold from other elements is currently an expensive laboratory experiment and not a viable commercial activity. Perhaps technology will improve enough in the future to make creation of gold in nuclear reactors a profitable economic enterprise.
