Basic Overview of Fusion

The most common question that I get when I tell people I am trying to build a nuclear reactor is, "Gee isn't that dangerous?!? What if it blows up?" Well, yeah, it is kind of dangerous, but this reactor will never explode, much less produce a mushroom-cloud-worthy blast. It is definitely possible to electrocute oneself, but the "nuclear" part of the reaction is actually pretty safe.

There are many types of nuclear reactions, the most notable being fission and fusion. When people refer to "nuclear energy," they are most likely talking about a fission reactor. In a fission reaction, a nucleus of a heavy element (such as uranium) absorbs a neutron, becomes unstable, and breaks up into two or more smaller elements in addition to shooting off free neutrons. If there is enough of the heavy element in close proximity, the free neutrons from the first reaction will cause more reactions and so on and so forth. If this chain reaction is controlled and moderated, you have the makings of a power plant.

In fusion, the opposite occurs. Instead of a really big element breaking down, two or more small element nuclei combine (i.e. "fuse") into a nucleus of a larger element, also giving off free neutrons in the process. Unlike fission, it is not the free neutrons that sustain the reaction, but the force that is causing the small nuclei to collide and combine.

In a fission reactor, the nuclear reactions are moderated so that the chain reaction cannot spiral out of control. The Chernobyl disaster was an instance where the moderation failed and there was a catastrophic chain reaction. However, in a fusion reactor, this would never happen because an outside force is required to keep the reaction going, and once this outside force was "shut off" the reactions would cease almost instantly.

As far as radiation goes, fusion deals with light elements, such as hydrogen and helium, which in general are not radioactive. Some reactor designs use a radioactive isotope of hydrogen (called tritium) but my reactor will run on a stable hydrogen isotope (called deuterium). The product of the fusion reactions will be a mixture of helium and the aforementioned tritium. The helium is stable, and while tritium is radioactive, it has a very short half-life and low energy decay. Thus, the reactants and products have low, if any, radiation.

While the reactor is running, radiation in the form of fast neutrons will be produced. Although neutron radiation is dangerous, my reactor will not pose a significant nuclear threat anytime soon. First off, I will be lucky to produce enough neutron radiation to notice with measurement devices, let alone be damaging to a person. Secondly, the danger of the radiation drops off exponentially the further away one is from the reactor. In an article by Tom Ligon on the fusor.net website, he says that if one were to stand one meter away from a typical amateur fusion reactor, it would take 12 days of continuous bombardment before the person would even have to start worrying. Finally, as aforementioned, the reactor only produces the fast neutrons while it is on, and because of the finicky nature of the fusion reactions, I will be lucky to be able to contain my reactions for longer than a minute at a time.

To sum it up, as a fusor utilizes fusion instead of fission, my reactor will not be producing radioactive goo or exploding in a giant mushroom cloud anytime soon.