 The radioactive inventory at shut-down may be comparable to that of a fission reactor, but there are important differences.The half-life of the radioisotopes produced by fusion tends to be less than those from fission, so that the inventory decreases more rapidly.Unlike fission reactors, whose waste remains radioactive for thousands of years, most of the radioactive material in a fusion reactor would be the reactor core itself, which would be dangerous for about 50 years, and low-level waste for another 100.