By Robert Hazen, Ph.D., George Mason University
The realization that nuclear reactions produce heat and radiation through the conversion of mass into energy has been one of the transforming discoveries of the 20th century. With humans attempting to harness this energy, there are both benefits and risks associated with our growing command over nuclear energy.
Nuclear Technologies and Their Leftovers
One of the dangers of nuclear technologies is the problem of disposing of nuclear waste. Nuclear waste comes primarily from used reactor-control rods—when the uranium-235 is depleted, it has split apart into highly radioactive elements and also is a byproduct of nuclear weapons production. The largest site in the U.S. is at the Hanford Facility in central Washington State, where most of the weapons-grade uranium and plutonium was produced.
In this process, the uranium and plutonium were concentrated by dissolving all sorts of radioactive materials into nitric acid, then the uranium and plutonium were extracted, and what’s leftover is literally millions of gallons of concentrated nitric acid chock-full of all sorts of radioactive isotopes.
This is a transcript from the video series The Joy of Science. Watch it now, on Wondrium.
The Difficult Problem of Nuclear Waste
The waste products of these nuclear-fission reactions include many different radioactive isotopes, many different chemicals. There are strontium-90, with a half-life of 28 years; cesium-137, a half-life of 30 years; krypton-85, with a half-life of 11 years; and iodine-129, with a half-life of 16 years.
However, these aren’t the big problem because all of these are going to decay to safe levels in about 300 years; you just need to store these isotopes for 300 years or so. The problem is with things like cesium-135, with a half-life of two million years and technetium-99, with a half-life of 210,000 years; these are going to remain dangerous for thousands upon thousands of years.
The problem of confining this waste for many thousands of years is compounded by decay chains because the mix of elements under storage keeps changing as one element decays to another. Some of those combinations of elements are fine, but some of them become explosive, while some of them become very reactive or very corrosive.
The Department of Energy is zeroing in on a steel alloy that’s supposed to last for 10,000 years and hold this radioactive waste, but how can anyone be sure? No material ever created by humans has lasted for 10,000 years, especially when it’s holding nitric acid that’s concentrated with a brew of other corrosive elements. It’s a very difficult problem.
Learn more about properties of materials.
Acceptable Solution for Nuclear Technologies Waste
By far, the most widely accepted solution is the burial of canisters made of this steel alloy in a dry, geologically inert environment. The problem here is where to put them, what kind of container should be used?
The site that people are talking about now is Yucca Mountain, in Nevada. There’s already a test burial site there, and they’re talking about adding more and more canisters to this site because there doesn’t seem to be anyplace else to put it, but there are lots of questions about Yucca Mountain in Nevada.
Yucca Mountain is certainly remote and far away from any population center, but nobody knows how the water table of this mountain varies. The groundwater now is very, very far below the level of the waste disposal site. But maybe over thousands of years or tens of thousands of years, the water level rises and falls, and if so, one certainly doesn’t want the burial site to be underwater. That would be very dangerous because it could contaminate water supplies.
Also, Nevada’s a very geologically active area; there are lots of earthquakes in that region. Yucca Mountain itself looks like a fairly young geological feature, and nobody knows how active it is.
Learn more about chemical reactions.
Benefits of Nuclear Technologies
Nuclear science has also brought humanity many, many benefits, and one has to focus on those. In addition to its importance as an energy source, we can use radioactive tracers to monitor all kinds of environmental situations. For example, the flow of streams, the flow of atmospheric gases, the flow of chemicals in our own body can be traced by radioactive tracers.
In medicine, specific radioactive tracers highlight the workings of the body. Radioactive glucose, for example, reveals brain function, radioactive iodine reveals the thyroid gland and how it’s working, and radioactive phosphorus compounds can concentrate in areas of active bone growth and tell doctors whether bones are healing properly. Indeed, radioactive materials are also often used to destroy cancerous tissues and save people’s lives.
Common Questions about Benefits and Dangers of Nuclear Technologies
One major danger of nuclear technology is the problem of nuclear waste disposal. Some isotopes, such as cesium-137, have a half-life of 30 years. But other isotopes, such as cesium-135, have a half-life of two million years.
The solution to reducing the dangers of nuclear waste is to bury it in a completely secluded location away from biological centers. One of the nuclear waste disposal sites is located in Mount Yucca, Nevada.
Nuclear technology has many advantages. Nuclear technology is not only a very important energy source, but it’s also utilized to trace environmental conditions. Nuclear technology also has multiple medical applications.
