Fusion reactors turn themselves into radioactive waste. Neutron radiation is inherent to nuclear fusion and when previously stable non-radioactive substances are subjected to neutron radiation, they may absorb some of those neutrons and become radioactive. (This is called neutron activation.) Some materials are less prone to this than others and that would be considered during the construction of a production fusion reactor, but even so components of the reactor would likely become so radioactive that the only way to perform maintenance on the reactor would be robotics. And when the reactor eventually needs to be decommissioned, it needs to be treated accordingly.