There are various approaches to creating a fusion reaction. There is laser fusion, microwave fusion, and fission/fusion which combines charged particles, particle beams, and compression fields to produce a controlled fusion reaction. And not all fusion reactions produce helium and energy. There will also be heavier elements that will be fused into even heavier elements with energy being liberated.
Laser fusion relies on lasers to hit a target of deuterium and tritium to heat them up to a temperature hotter than just below the surface of the sun. If the reaction can produce a self-sustaining mass of plasma that can power the lasers to superheat more heavy hydrogen, such a reactor may produce more energy than it consumes.
Microwave fusion is similar to laser fusion except microwaves are used instead of lasers to heat up the heavy hydrogen and force it to fuse into helium plus liberate energy. The plasma in both reactors will be circulated past steam generators that will generate electricity. So far, the reactor consumes more energy than it creates. But there is no long-term nuclear waste produced in either reactor.
The fission/fusion reactor would use a fission reactor to supply the charged particles that would turn hydrogen or some other light element into an isotope of the element. Particle beam units would superheat the gaseous element in the reaction chamber and when the mass has reached the highest possible temperature, compression fields would be generate to fuse the element into a heavier element and liberate energy. The plasma produced would be circulated past steam generators to produce electricity. When the plasma is too cool to be efficient, it will be vented so that more plasma can be produced during the fusion process.
If the element used can be handled at room temperature, it will make the injection of the element easier. The heavier element will be easier to handle too. If an injection reator is used to supply the charged particles, it will be a high-energy reactor with a lower yield than a bomb but greater than that of a standard reactor.
If water were used in the fusion portion of the reactor, a plasma would break apart the water into hydrogen and oxygen and after the elements are superheated by the particle beams and the compression fields collapse around the mass, the hydrogen fused with the oxygen should produce fluorine gas plasma and energy will also be liberated.
In the movie "Back To the Future: Part Two," a fusion reactor provided the power needed by the car/time machine to travel both through the air and through time. Any type of material could be fed into the reactor as fuel. Since a plasma is produced in a fusion reactor, the material would be incinerated with little waste. With magnetic containment generated by the reactor, the plasma shouldn't come in contact with solid material otherwise it would melt the material. The plasma would be vented if it becomes too cool to be efficient.
If the reactor is a fission/fusion reactor, it will work on the same principle as a hydrogen bomb in that it needs a fission reaction to initiate the fusion reaction. With the nuclear fuel being broken down into particles and the neutrons being absorbed in the moderating target of the injection reactor, the only waste might be neutrons. If the fusion reaction can be self-sustaining, more energy will be produced than what is consumed. As long as the plasmas and particle beams and fields can be contained, the reactor should be very safe and produce almost no pollution. The neutrons might be used in the fusion process to fuse heavier elements into even heavier elements since they will need all three types of basic nuclear particles; electrons, protons, and neutrons. The energy yield might be less if heavier elements are fused or if hydrogen and oxygen is fused into fluorine.