NUCLEAR (FISSION) ENERGY—TAKE IT OR LEAVE IT?
Using nuclear reactions to produce electricity is a weighty endeavor. On one hand, there is a lot of around-the-clock energy that can be utilized. On the other hand, there are grievous risks associated with radioactive materials, and the recent catastrophe in Japan has brought these risks back into the public eye. Controversy has plagued the nuclear power industry since its beginning, and it shows no sign of being resolved.
At the heart of a typical nuclear power plant is the reactor which contains radioactive metal, such as uranium-235 (U-235). On the atomic scale, U-235 atoms break apart to form atoms of lighter elements. At the same time, gamma rays and free neutrons are expelled. That is the process of radioactivity. The neutrons can bump into other U-235 atoms and cause them to break apart, forming a chain reaction. On a human scale, metal rods glow and give off a lot of heat. Water is exposed to the radioactive metal to absorb the heat. Once the water is brought to its boiling point, it is passed through turbines which produce electricity. But the same radiation that boils water can kill humans or cause disease. Extensive containment structures and strict safety protocols are used to protect people and the environment from exposure to hazardous radiation. These measures also make nuclear power tremendously expensive.Just one nuclear power plant can cost several billion dollars to build and requires billions of dollars every year for operating and fuel costs. Once built, however, a plant can produce electricity at the rate of less than three cents per kilowatt-hour. The energy is so plentiful that a profit can be made. Even so, it may take more than a decade to pay off the initial cost. While building a nuclear power plant is more expensive than hydrocarbon-burning power plants, nuclear fuel is cheaper than fossil fuel in the long-run. Fuel rod provisions need to be renewed about every other year, whereas coal or natural gas supplies must be replenished continuously. What happens to spent fuel rods?
Over time a fuel rod gradually becomes impure with fission products that hinder the nuclear chain reaction. When the fuel rod cannot profitably heat water it is removed from the reactor. Since it is still dangerous to living things, it must be stored until radiation levels have diminished—that can take a long time. Take, for example, a given amount (say 100 kg) of plutonium-239 (Pu-239) which is very hazardous. Pu-239 has a half-life of about 24,000 years. That means after so many years you will have half as much (50 kg) Pu-239 as when you first measured it. The rest has become fission products, like free neutrons and uranium-235. But U-235 is also radioactive, and it has a half life of over 700,000,000 years! Some countries recycle their fuel rods by separating the fission products from the still-useful elements. This is very expensive and dangerous, but it reduces the amount of nuclear waste. Anything that cannot be reused has to be stored which worries many people. There is the ever-present possibility that terrorists might steal the radioactive waste or some radioactivity might leak into the environment. If radioactive material got into the wrong hands, then it could be used to make a “dirty bomb”. A dirty bomb is a way of intentionally exposing people and the environment to radiation without the need for a mushroom cloud. The only way around this would be to launch the waste into space, but there is a big risk of rocket malfunction. Then you might have an accidental dirty bomb. No matter what you do, there are risks, fears, and costs tied to nuclear waste.
People have good sense to fear radioactivity, and Japan's current situation is a clear example of the danger of nuclear power. Nuclear power plants in Fukushima Prefecture have suffered major problems since the earthquake and tsunami on March 11th. Some radioactive material has been released, and right now Tokyo's tap water is considered unsafe for babies. If not for their diligent efforts, the Japanese people would be in much more danger. They are returning electricity and water to the plants and gradually cooling the reactors, but their work is far from finished. Had a full-blown nuclear meltdown occurred, much more radiation could have escaped. The fuel rods would have become hot enough to melt themselves and the vessel around them, releasing large amounts of radiation and heat. But if Japanese workers continue to gain control over the situation, then radioactive contamination should be quite limited. Still, the cost of cleaning up, decommissioning the plants, treating people for sickness, and other necessary acts will be huge. We should not forget the psychological consequences. People can be frightened by this event, and that will affect the future of the nuclear power industry. Also, the demand for products such as iodine pills and Geiger counters is increasing. Hopefully Japan will fully recover, and perhaps people the world over will engage in conversations about atomic energy. Do you think we should be using nuclear power? Please leave a comment.
SOLID OXIDE FUEL CELLS
“We are like tenant farmers chopping down the fence around our house for fuel when we should be using Nature's inexhaustible sources of energy — sun, wind and tide. ... I'd put my money on the sun and solar energy. What a source of power! I hope we don't have to wait until oil and coal run out before we tackle that.” -Thomas Edison
Nowadays it seems there are two popular approaches to solving nationwide energy needs. One is to greatly expand our use of “green” energy sources, such as wind and solar power. The aim here is to decrease pollution and use more sustainable sources of energy. The other approach is to increase our use of domestic fossil fuels. This way people who have invested their lives in an industry do not lose their jobs. Proponents of both approaches want one thing: energy independence. Rising oil prices are teaching us that global economic interdependence is not always a good thing. Is there any way to please both sides? Maybe solid oxide fuel cells (SOFCs) are an answer.
SOFCs are devices that harvest energy from the high-temperature reactions between oxygen and various fuels. Instead of using heat from the chemical reactions (as in traditional power plants) to drive turbines, a SOFC takes electrical energy directly from the chemical reactions. This means greater efficiency—more electricity for a given amount of fuel. Also, it is supposedly cleaner to put fuel through a fuel cell than to simply burn it. Even so, no one can disobey the laws of physics and chemistry. If fuel and oxygen go into a chemical process, then something has to be produced. You guessed right—carbon dioxide. Some people are very optimistic about this technology as a solution to our energy needs. Perhaps the most well-known example of a SOFC would be the Bloom Box, a mysterious project revealed to the world last year. Bloom Energy, the company that produces Bloom Boxes, has had hundreds of millions of dollars invested and boasts companies like eBay and Google for customers.
Green technology supporters can appreciate the efficiency of this technology. It produces less carbon dioxide per kilowatt-hour of electricity than a gas fired power plant. And because SOFCs can use fossil fuels, workers in the oil industry can keep their jobs. It sounds like an easy choice, but not when you consider the price tag on a SOFC. The high temperatures required for chemical reactions in a SOFC limit its functional lifetime. Exotic materials, such as Lanthanum strontium manganite and the metal scandium, are also needed for the reactions. Expensive metals and durable construction make for high cost of production. 100-kilowatt units that would be sold to businesses like Google cost over half a million dollars each. Smaller units that are suited for household energy consumption would be unaffordable to many homeowners. That is the main reason SOFCs are not yet revolutionizing how we get our electricity. Is it possible to make affordable fuel cells? Should we use SOFCs at all?
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