Are accidents as in Chernobyl and Fukushima possible in fusion power plants?
No. This is because a fusion power plant affords an important naturally given property in that it can be so designed that it has no energy sources which, in case of an accident, could destroy a safety shield from inside.
Nor can a fusion power plant get out of control. The burn chamber always contains just as much fuel as is being burned, i.e. about one gramme of deuterium and tritium distributed in a volume of about a thousand cubic metres. The fuel of extremely low density, despite its high temperature, therefore has an extremely low power density, comparable to that of an ordinary light bulb. The radioactive tritium component can thus be safely confined.
The radioactive emission of the power plant to which the most exposed person is subjected is in normal operation about one per cent of the naturally present effective radioactive dose. Even after a major accident one is still well below the limit values for initiating evacuation measures.