I used to work as a propagandist for the Atomic Energy Commission/Nuclear Power Industry. I've got a rap on nuclear waste that would make you want to buy stock in it, every sentence in isolation perfectly truthful, but the whole thing assembled is a beautifully crafted lie. If you're really interested I'll lay it on you. I'm sure a lot has happened in that industry since I worked there in the 70s, but the technology of power generation and nuclear physics has changed little.

The meat of this article is that the neutron source, a fusion reaction, is supposed to promote fission in fissionable nucleides. This is perfectly reasonable. What is never mentioned is that these "transuranics" (elements heavier than uranium, like plutonium) are only a small, and not very dangerous proportion of the waste. It's the fission products (cobalt, iodine, hafnium, barium, cesium, and a host of others) that are the most dangerous.

These fission products I mention are radioactive isotopes of common elements, and are created when a uranium (or thorium or plutonium) nucleus breaks up when struck by a neutron. They can also form when the fission products absorb stray neutrons, or when they lose protons or neutrons or beta particles due to their own radioactivity. (The decay products of radioisotopes are often radioactive themselves.) Spraying these with neutrons will not create energy, it will just create more waste.