From “The Trouble with Fusion”: The goal of the fusion program is to produce a reactor fueled by hydrogen isotopes, deuterium and tritium containing one and two additional neutrons. This choice of fuel eases the problem of achieving an energy-producing reaction, but it also has features that make it more difficult to convert that energy source into a useful power plant. The most serious difficulty concerns the high-energy neutrons released into the deuterium-tritium reaction. These particles damage the structure of the reactor and make it radioactive. The chain of unwanted effects ensures that any reactor using DT Fusion will be a large, expensive and unreliable source of power.
When these shortcomings become more widely understood, the illusion of a fusion program will undermine the prospects of other fusion programs, no matter how sensibly redirected to them for decades to come.