Nuclear Waste and Breeder Reactors - Myth and Promise
In my earlier articles on nuclear power, I reviewed how fissile Uranium-235 drives a nuclear reactor, and how Uranium-238 participates in the process by transforming into Plutonium-239, which is fissile like Uranium-235. This phenomenon of nuclear physics lies at the heart of a conceptual blueprint by which the United States once and for all can end its energy dependence on fossil fuels and the unstable Third World nations who export petroleum.
Two significant obstacles stand in the way of an energy-independent United States: (1) Finding a solution to the immense amounts of dangerous and highly-radioactive spent reactor fuel already on hand, and (2) Implementing reactor designs that generate electricity while creating more useful nuclear fuel.
In order to see how this can be done, it's first necessary to review some basic physics: Plutonium-239 produces significantly more energy than Uranium-235. And the process continues to produce the additional isotopes Plutonium-240 and 241 and 242. 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. Why is this not being done?
Plutonium is used in atomic bombs - the fact that it's pure Plutonium-239 that makes an atomic bomb work, and not the other three isotopes, apparently didn't matter, because in 1977 President Jimmy Carter signed an executive order that banned the reprocessing of nuclear fuel in the United States. The rationale 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 essentially impossible to separate out the Plutonium-239 from the other isotopes in sufficient purity to use it for bomb making. The British tried it, the Russians tried it, the French tried it, and we tried it, but nobody did it very well, even though we had the best scientists and all the money in the world to throw at it.
If you try to make a bomb with such a mixture of Plutonium isotopes, forget about it - it won't work, ever. We're talking about the laws of physics, 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 won't work anyway is just plain dumb.
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.
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 commonly known as "fast" neutrons.
In order to regulate the internal neutron flux, the primary coolant typically 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.
At its best, the Breeder Reactor system produces no nuclear waste whatever - 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 radioactivity to dissipate - is on the order of thirty to forty years. By contrast, the half-life for the stuff we presently consider nuclear waste is over 25,000 years!
Imagine a transformed energy landscape, where there is no nuclear waste problem, no power shortages, a safe and inexhaustible supply of inexpensive electricity. France has constructed and used Breeder Reactors like this for many years. So have the British and the Japanese. So why not the United States?
We invented the technology but then made a political decision back in 1977 that has accomplished nothing but to create immense piles of long-lived, highly radioactive material that we cannot use for anything, and worse - we must safely store for more than its half-life of 25,000 years.
The first thing we need is to identify the location and related technology that can safely isolate thousands of tons of spent nuclear fuel for 25,000 years - which is a longer time than all of recorded human history. Will our descendents 25,000 years from now even be able to read a sign that says: "Keep Out!"
The scientists - not the ones who made the stupid 1977 decision - but the ones who have to carry it out, have solved part of the problem. Researchers have developed a glass strengthened with a boron complex that appears able to withstand at least 10,000 years of abrasion with little erosion. For now, they encase the nuclear "waste" in borated glass beads, and then embed these in hardened concrete inside steel drums, and store them in pools of water.
The United States has several thousand of these drums just waiting for the politicians to decide into which hole in the ground they will eventually be moved.
It is tempting to believe that our society will progress sufficiently that one day it will finally decide to make practical use of this valuable resource. Unfortunately, our scientists did a pretty good job with the borated glass and concrete encapsulation. It may turn out to be cheaper to refine new nuclear fuel than to undo what we have created.
The final irony is that there is a much better way to dispose of spent nuclear fuel if we really don't want to keep it around. We tend to think of the solid earth as just that, although anybody San Francisco or Los Angeles can tell you that it just isn't so.
Our planet's crust consists of a multitude of individual large pieces called tectonic plates. These plates are constantly moving around the surface of the planet, jostling and rubbing one another, and sliding over and under each other. For example, when the plate upon which the Indian sub-continent rests bumped into the Asian plate, the resultant crumpling formed the Himalayan mountain chain. The Western Pacific plate slides under the Asian plate, forming the Marianas Trench, the deepest spot in the ocean. These forces are enormous, surpassing by orders of magnitude anything else on this planet.
As one plate subducts under another, the entire plate edge is forced deep into the bowels of the Earth where it, and everything on and in it, is totally transformed into the stuff that makes up the Earth's mantle. This transformation results from tremendous pressure and from heat, caused in part by the pressure and by radioactive substances contained within the Earth. The Challenger Deep in the Marianas Trench in the Pacific is nearly 36,000 feet deep, over seven miles of water.
If we were to drop the thousands of borated glass encased drums of so-called nuclear waste into the Challenger Deep or some other fast-moving subduction zone, within a few hundreds or thousands of years the material would be pulled deep within the Earth's interior where it would be completely and utterly dissipated and destroyed.
If there is one long-term "lesson learned" from the recent span of history that includes the 1973 OPEC oil embargo, the 1990 Iraqi invasion of Kuwait and Operation Desert Storm, and our current war against terrorists, it is that the United States must become energy independent.
We have a staggering nuclear waste problem created by a political decision that we could solve simply by reversing that original decision. We also have a perfectly viable way or resurrecting clean and safe nuclear power simply by making the political decision to develop it.
There is no compelling reason to delay shifting our dependence from fossil to nuclear fuel, and redirecting our nuclear focus to Breeder Reactors. We have the ability to control our own energy destiny if we only have the courage to renounce past executive errors and to embrace viable new technologies.