Ch. 04 – Breeder Reactors (Part 2)

In our earlier discussion about how fissile Uranium-235 drives a reactor, we also learned that Uranium-238 participates in the process by transforming into Plutonium-239 which is fissile like Uranium-235. In fact, this isotope of plutonium produces significantly more energy than Uranium-235. And the process continues to produce Plutonium-240 and 241. This raises an interesting question. 

Can we take these fuel rods that contain all this plutonium, separate out the plutonium and whatever uranium was not used, and make more fuel rods? You bet. In fact, we actually end up with more fuel after the process than what we started with. 

So do we do this? No–at least not in the United States.

So why not, since it seems like a pretty good way to get more fuel? 

The answer is pretty dumb. A substantial part of the new fuel is lutonium, as a mixture of the four isotopes 239, 240, 241, and 242. But collectively it is plutonium. Plutonium is used in atomic bombs. The fact that pure Plutonium-239 is what makes an atomic bomb work apparently doesn’t matter, because in 1977 President Carter signed a policy that banned the reprocessing of nuclear fuel in the United States. The explanation was that the plutonium could possibly be stolen, and terrorists might be able to use it to make atomic bombs. Never mind that in the real world, it is virtually impossible to separate out the Plutonium-239 from the other isotopes in sufficient purity to use it for bomb making. The process involves using high-precision centrifuges to separate out the various isotopes by weight. The Brits tried it; the Russians tried it; the French tried it; we tried it; but nobody did it very efficiently, even though we had the best scientists and all the money in the world to throw at it. This is why we use an entirely different method for generating the plutonium we use in our nuclear weapons. And if you try to make a bomb with a mixture of plutonium isotopes–forget about it; it won’t work, ever. We’re talking about the laws of physics here again, folks. 

Chicken Little and Greenpeace notwithstanding, unless you have pure Plutonium-239, your bomb will fizzle. So throwing away all that valuable nuclear fuel to prevent terrorists from making a bomb that they can’t make anyway is just plain dumb.

So how do we get the Plutonium-239 for our atomic bombs? We built reactors fueled with Uranium-238, whose only job is to create Plutonium-239. These systems are some of the best-guarded plants in the world. Our weapons-grade plutonium is safe. And we use the stuff over and over and over, as necessary, to keep our supply of weapons-grade plutonium up to date and available.

So can we do the same thing to produce nuclear fuel? 

The answer is a resounding yes! 

This type of reactor, called a Breeder Reactor, actually produces more fuel than it consumes. A reactor designed to use a mixed plutonium fuel is basically the same as the uranium reactor we have already discussed. However, the neutrons that sustain the reaction contain more energy–they are fast neutrons. In order to regulate the internal neutron flux, the primary coolant typically used is one of the light metals, like sodium. Since Uranium-238 is one of the more abundant elements in the Earth’s crust, Breeder Reactors make it possible to have an essentially unlimited source of fuel for nuclear reactors–which means an unlimited supply of electricity. 

If I don’t have your undivided attention yet, try this on for size. At its best, the Breeder system produces no nuclear waste whatsoever; literally everything eventually gets used. In the real world, there actually may be some residual material that could be considered waste, but its half-life–the period of time it takes for half the substance to change into something else–is on the order of thirty to forty years. By contrast, the half-life for the stuff we currently consider nuclear waste is over twenty-five thousand years!

Imagine, no nuclear waste problem. No power shortages. Inexpensive, safe electricity that never runs low. France has constructed and used Breeder Reactors like this for many years. The British use Breeders; so do the Japanese. We invented the technology. It was in our grasp . . . so what happened?

I hesitate to bring up acorns again, but you get the idea.

© 2006 – Robert G. Williscroft