by Max Beeson
Nuclear energy has become one of the most important energy sources in the world. It is a clean energy, producing less CO2 emissions than coal, natural gas, and petroleum. It is safer to produce nuclear energy than any other source, due to rigorous training and safety regulations.
However, there is still resistance to its use. The memory of Chernobyl, and most recently, the nuclear problems caused by the 2011 earthquake in Japan, scare people. Combined with visions of toxic green nuclear sludge from the Simpsons, and mushroom clouds from weapons, the nuclear industry has a pretty bad image. However, we shouldn't let these fears hold us from harnessing one the most promising energy sources of today. By understanding the nuclear fuel cycle and comparing nuclear energy to other energy sources, we’ll begin to understand how important nuclear energy is to our future.
To understand nuclear energy, we first must examine its fuel - uranium. Uranium is a naturally occurring metal that is almost as abundant as tin. Uranium mines don't pose any threat to those living nearby it. The amount of radiation one would receive by living near uranium mine is extremely low. It is mined, and then taken to a mill where the uranium is separated from waste rock. It is crushed, and set in an alkaline solution. The remaining uranium is then heated until dry, and packed into barrels. This is called “yellowcake” uranium.
And new mining methods using leaching solutions don’t even require mining or crushing of the rock anymore, making it even less harmful.
Unfortunately, when some hear the word “nuclear” the thought of nuclear explosions and mushroom clouds are envisioned like in a 1950’s cartoon (www.weirdwildrealm.com).
After it is milled, the yellowcake is then taken to an enrichment center. The enrichment process separates uranium-235 from uranium-238, the two important isotopes or forms of this element. Natural uranium does not have enough U-235 in it to maintain the controlled nuclear fission, or splitting, reactions needed to produce heat. U-235 has to be in about five times the concentration of natural uranium in order to achieve these reactions.
There are two commercial ways to enrich uranium - the centrifuge process and the gaseous diffusion process.
Centrifuge enrichment method turns the uranium into a gas, and spins the uranium at high speeds to take advantage of the one percent difference in the masses of U-235 and U-238. Gaseous diffusion relies on Graham's Law, which states the rate that gases effuse (how many molecules per second pass through a tiny hole) is based on their molecular weight.
New methods, such as laser processes, are being developed but there has not been a way to make them commercially usable yet. In this process, a laser ionizes the U-235, giving it a positive charge. A negatively charged plate is then used to attract and enrich the amount of U-235 in the sample.
After whatever process is used to enrich the uranium, the product is turned into what will become the usable fuel. It is baked into small ceramic pellets. These pellets will be inserted into a fuel rod, which will go into a nuclear reactor. Every aspect of both the pellets and the fuel rods are carefully measured and inspected to ensure that they will work safely.
Next the fuel rods are placed into a nuclear reactor. The nuclear reactor takes advantage of U-235's ability to fission and set off a chain reaction. Think of the uranium burning in a wave. The uranium does not burn up all at once, it burns in a wave through the fuel rod. This chain reaction creates heat which is then used to turn water into steam. The steam turns a turbine that gives us, finally, electricity.
So what are we left with? The spent fuel rods and radioactive waste. These fuel rods are hot and radioactive. They are taken out and placed into cooling ponds for at least 4 years. The spent rods are then transferred to a dry storage facility. Now this process does sound dangerous. There is no denying that hot radioactive material could be harmful.
However nuclear refueling takes place just once every 12-18 months. These refueling periods are treated with extreme caution by highly trained professionals. No one has ever been harmed, let alone killed, during this process.
The rest of the waste? It is categorized by its radioactivity into three levels - low, medium and high. Strict regulations state how waste from each of these levels must be treated and disposed.
This process sounds fairly safe. Compared to the coal and oil energy processes, it is. Nuclear energy has the lowest deaths per trillion kilowatt/hours in the industry. In fact, no one has ever been killed at a nuclear power plant in the United States. No other energy source has as safe a record as nuclear. A big part of this safety is the training and regulations that occur throughout the process. The nuclear fuel cycle is more modern than most, with both its technology and training.
There are those that would say that nuclear plants are not cost effective. They say that developing countries need energy, and the only reasonable way to supply energy is with coal. It is true that they are more expensive than a coal or other fossil fuel burning plant. However, nuclear plants are getting cheaper. The current models of nuclear plants, which are being called Generation III plants, are huge improvements over the older Generation II plants. The Generation III plants are more simple, cheaper, more efficient, and have a 60 year operating life.
These new plants are safer, too. The plants are built in pieces, in a factory. This creates a standardization for the plants, making them cheaper and faster to build. The plants are also designed to manage accidents with no active controls, and instead rely on natural forces like gravity and heat resistance of certain materials.
Also, cost cannot be the only consideration as we move forward. The CO2 and other environmental impacts of fossil fuel plants are devastating. We don’t let companies dump their waste into rivers, even if it is cheaper. Why should our energy companies be any different? As we continue to let these fossil plants “dump” their waste into our atmosphere, we will ultimately pay the price.
So this is nuclear energy. A modern, clean, and increasingly less expensive energy that a lot of Americans are afraid to use. Why? If you look at the fuel cycle, there is nothing to be afraid of. Of course, I’m not saying we should just tear down our coal plants, and rely completely on nuclear. Developing countries do need power – fine, let them have coal plants. There is no excuse, however, for countries like the United States not to take full advantage of this safe form of energy.
Diagram of a generation III nuclear power plants. Improvements in the cooling system, and overall design have made these dramatically safer and more efficient (courses.engr.illinois.edu).