Question

Which of the following is NOT an advantage of using a fusion reaction instead of a fission reaction to produce energy?
A. Workers are not in as much danger from radiation.
B. Hydrogen is used, and hydrogen is easily obtained from water.
C. No harmful waste products are produced.
D. Fusion reactors require less energy than fission reactors do.

Answer 1

You're meant to answer D. But this answer is poorly written, because the question makes clear the reaction is being used to PRODUCE energy. How can reaction that produces energy be one that requires energy as well? Logic fail. What the answer is meant to say is that energy is required to get the reaction going in the first place -- and then you get back more energy than you put in. Chemists call this an "activation" energy. And it's certainly true fusion requires way more energy to get started than fission. In fact, fission doesn't require any activation energy at all. Put enough fissionable material together in one place, and it starts up by itself. On the other hand, fusion only happens at enormous temperatures and/or pressures, so you've got to heat your materials up and/or compress them to get things going -- which takes energy, and plent of it.