The Fermi Chronicles - Part 10: Utilizing Nuclear Reactions To "Breed" More Fuel

This one is pretty cool. Last time, I wrote about nuclear fission, and that an important class of material called fissile material is necessary for sustained nuclear reactions. Fissile material is much more rare than general fissionable material. Examples of fissile material are uranium-235 and uranium-233 as well as plutonium-239. Now the astute reader of the prior 9 posts might have noticed that uranium-238 is the heaviest naturally-occurring element in nature, and anything heavier than that is synthetic. That includes plutonium. Interestingly, plutonium-239, a fissile material, can be manufactured from uranium-238, the most common form of uranium in nature (greater than 99%). How can this be done? Amazingly, it can be produced right in the nuclear core of an operational nuclear reactor if designed correctly. These type of reactors are called "breeder" reactors. None are in use in the U.S. anymore, but it may come to that some day. Fermi 1, by the way, was a breeder reactor.

All nuclides that absorb neutrons but do not fission, or split, are called 'fertile' materials. Fertile materials can be changed into fissile materials by a process called 'transmutation.' And yes, transmutation is what the members of G-Force used to become superheroes in one of my favorite childhood adventure cartoons Battle of the Planets. Transmutation is also used in the excellent sci-fi movie Dune when a candidate Reverend Mother drinks the 'water of life.' Plus other sci-fi shows and movies but I'll spare you every instance since my geekiness is more than apparent at this time already.

Anyway, the more common U-238 is fertile material for manufacturing Pu-239 via transmutation. Here's how that chain of events would go. U-238 already present in nuclear fuel rods absorbs a neutron and becomes U-239. That U-239 then through beta radiation becomes Np-239 (neptunium) and then Pu-239 by giving off another beta particle another beta particle. And viola! Fissile material almost out of thin air! Many countries such as Japan (and Spain) have a great interest in breeding their own fuel as they don't have much in the way of their own nuclear material and must import it. Breeding more fuel is making the most of what you got, no? In fact, by what may seem like a quirk of nature (or a blessing?), more fissile material can be made by transmutation, than is used to do it! Even though the half-life of the intermediate products is small, the half-life of Pu-239 is about 24,000 years. So it is relatively stable for an unstable atom, which makes it ideal for nuclear reactors and weapons.

In WWII, two atom bombs were dropped on Japan that ended the war and ironically saved many lives on both sides. The bomb termed "fat man" was plutonium-based using Pu-239 as the fuel for the explosion, while "little boy" was uranium-based utilizing the fissile material U-235. Fat man was dropped on Nagasaki, while Little Boy was dropped on Hiroshima. The first nuclear weapon ever detonated in the Trinity test was plutonium-based.

Previously:
The Fermi Chronicles - Part 9: Nuclear Fission
The Fermi Chronicles - Part 8: Neutron Interaction
The Fermi Chronicles - Part 7: Radioactive Decay and Half-Life
The Fermi Chronicles - Part 6: Atomic Structures
The Fermi Chronicles - Part 5: Nuclear Waste Storage
The Fermi Chronicles - Part 4: Radiation Types and Radiation "Dose"
The Fermi Chronicles - Part 3: Radiation Types
The Fermi Chronicles - Part 2: A week of training
The Fermi Chronicles - Part 1: The alpha post