the basic idea is a reactor that takes spent fuel rods and makes full ones at a loss with some power gained, it would need to be kept running(start up would take power and full fuel rods) and would be station only, it could either take a lot of a tier of spent rods and return less of them full(probably not for 3s) or a lower tier( or some combination) this would give a cheap market for spent rods and give stations another business