The energy content in fissile material means that it is worth six times its weight in gold. But its monetary magic doesn’t end there: fissile material has the Midas touch. In other words, fissile material can not only generate revenue, but can keep generating that golden revenue time after time after time.
When a neutron (either fast or slow) strikes a fissile nucleus, one of two things will happen. Either the nucleus will absorb the neutron and spit out a gamma ray, or the nucleus will absorb the neutron and split into two large pieces. The second outcome, fission, is the one we’re interested in if we want to generate energy.
There’s only one naturally occuring fissile material in the world, uranium-235.
In 10000 atoms of natural uranium, only 72 of them will be uranium-235. If the red marbles represented uranium-235 and the white marbles represented uranium-238, then the picture above (taken with my wife’s cake pan) would be a pretty good depiction of how rare uranium-235 is in natural uranium.
As I mentioned, uranium-235 is the only naturally-occuring fissile material in the world. It’s really too bad that there isn’t some way to release all of that energy from the rest of the uranium, right? Well, it turns out that there is.
Uranium-238 will transmute into plutonium-239 over the course of a few days if it absorbs a neutron. Plutonium-239 is fissile, uranium-238 isn’t. But uranium-238 is cheap and abundant, accounting for 9927 of 10000 atoms of natural uranium. So there’s a way to make uranium-238 into fissile material, but it takes a neutron.
If fission only caused a nucleus to split and that was the end of it, then generating nuclear energy wouldn’t be possible, because we would have no neutrons to continue the reaction. Wherever you got that first neutron from, it would cause just one fission and that would be end of things. We wouldn’t even notice the energy release from a single fission.
But that isn’t how things really work in fission. Not only does fission split the nucleus, releasing energy, but it also releases additional neutrons.
If fission only released one additional neutron, then it would be possible to continue the fission process, at least in theory. So long as there was additional fissile material around, one fission could cause another fission, and so on and so forth. But the reality is even better.
Most fissions release two or even three neutrons and that opens up an exciting possibility. Like the Midas touch, these neutrons can turn worthless uranium-238 nuclei which aren’t fissile into plutonium-239 nuclei which are fissile. And this new fissile material that has been made is even better than turning lead to gold–made from something cheaper than lead into something worth six times more than gold.
There’s another way to exercise this Midas touch, using natural thorium. If thorium is struck by a neutron it will turn into uranium-233 over a period of about 40 days. Uranium-233 is fissile and will release energy too.
So unlike gold that can only be sold for money once, fissile material if properly used has the Midas touch–it can keep turning worthless uranium-238 or thorium into fissile material indefinitely.
The bad news is that we are not using fissile material properly in today’s nuclear reactors. We’re wasting its Midas touch. The good news is that we can build new reactors that will be able to exercise this amazing ability. They will change the world. They will be the future of energy.
(this post was originally published on Forbes)