There is no mention of nuclear reactors or cyclotrons in this article as a mechanism of uranium synthesis out in space:
However, “it is a longstanding puzzle where the heavy elements such as gold, platinum and uranium are made,” said study co-author Alexander Kusenko, a theoretical physicist at the University of California, Los Angeles. “All we know is that the process involves many neutrons.”
The extreme conditions needed to make the heaviest elements could be found in supernovas, but only in rare instances. Current models for nucleosynthesis face challenges explaining the observed abundance of some of the heaviest elements, especially when it comes to the nearby dwarf galaxy Reticulum II, whose stars are unusually rich in such material.
Now researchers suggest the universe’s heaviest elements could be forged with the help of black holes born in the early cosmos.
It’s premature to say uranium nucleosynthesis has been sovled by supernova, and the above authors are looking at black holes for that very reason. The only place where it was demonstrated experimentally from lighter elements was with electricity at the proton-21 and other z-pinch labs and much lower energies!