Fuel types and uses I
Nuclear power generation
- [Professor] Hey there, friends. Today, we're going to learn about nuclear power, and to do so, we're gonna visit my home state. Idaho? That's right. Land of the potatoes and also nuclear power? If you've driven through Idaho, there's a good chance that you passed by a quaint small town called Arco where you'll find the restaurant Pickle's Place, home to the Atomic Burger. Wait, a radioactive burger? Sounds a little disturbing. Actually, Arco became the first city in the world to be powered by nuclear energy. And of course, Arco became the first city to serve Atomic Burgers, grilled and seared to perfection using nuclear energy. But what's going on under that grill? Are they using glowing green rocks to make those delicious Atomic Burgers? Let's find out. Nuclear power plants often look ominous and a little bit scary, but they produce power the same way most other power plants do. Simply put, they boil water to create steam, which spins turbines to produce energy. Most nuclear power plants use light water reactors to generate electricity, which are made up of five basic parts. First off, we have the core of the reactor where fuel rods are inserted. Next up, we have the containment shell that encases the reactor and the spent fuel rods. Within there, we have supply of water, which is boiled to reduce steam. That steam then rotates a turbine attached to a generator which produces electricity. This act of turning an electric generator is actually the same process that's used for coal, gas, geothermal, hydro power, and wind power. No matter how complex the electricity generation system, that all boils down to the same idea, basically turning a wheel, one of the oldest agricultural-era human inventions, and that's what makes electricity. Finally, we have excess steam or water vapor, which is the only direct emission from nuclear power generation. Easy as pie, right? Well, it's actually pretty complex. So how is the water heated exactly? Nuclear energy isn't as easy as lighting up a grill, and it requires us to go down to the smallest unit of matter, the atom. Here, we get our energy at the atomic level, but it's not from the atom alone. No, to gain energy, we need to split the atom. This process is called fission, which occurs when neutrons are fired at an atom, causing it to split into separate atoms of other smaller elements. This split produces a huge amount of energy, which is largely converted to heat, which boils the water and produces steam. However, we need a special kind of atom for fission to happen, and most nuclear reactors use uranium-235. Wait, why uranium-235 though? Well, first, uranium-235 is big, not a triple 1/4 pounder big but big on the atomic scale. In the atomic world, this is known as being heavy. Secondly, uranium-235 is unstable because it's not only big, but it's also an isotope, meaning it has a different number of neutrons than the more common form of uranium, which is uranium-238, which has three more neutrons. This makes uranium-235 unstable or fissile like fission, which means it can be split by a neutron, thereby producing other elements, energy, and more neutrons. Those produced neutrons crash into other U-235 atoms, splitting them and causing a chain reaction, which is what makes nuclear energy work. This chain reaction is really important to note because it's what makes a nuclear power plant so different from its, well, more destructive cousin, the atomic bomb. In atomic bombs, the same process of nuclear fission is used except that it's a fast destructive, runaway, and uncontrolled reaction that results in massively powerful explosions, not something that we would want to happen in a nuclear power plant. Now a little goes a long way when it comes to nuclear fission. The fuel is actually composed of tiny pellets of uranium-235, each the size of a pencil eraser, but each also has the equivalent energy of a ton of coal. Yes, a literal ton. These pellets are packed together to form fuel rods, which are bunched into fuel assemblies and then placed in the nuclear reactor. Nuclear fusion is therefore really powerful and can generate a lot of heat from very little material. But to keep temperatures from getting too hot, which would cause a nuclear meltdown, and no, I'm not talking about melty cheese, unfortunately, the reactor is therefore cooled with water. When more heat is generated by the nuclear reactor than can be removed by the cooling system, or water in the case of nuclear reactors, the fuel rods can get so hot that they could start to melt and fall to the bottom of the reactor and potentially melt through and escape into the surrounding environment. That's called a nuclear meltdown, and that's also why in part, the reactor is surrounded by a containment shell of thick steel and concrete, which keeps radioactive materials from escaping. We don't wanna have any radioactive burgers. But fuel rods don't last forever. After three to six years in a reactor, fuel rods can't sustain the fission reaction effectively anymore and become highly radioactive. In turn, they need to be carefully removed and stored. But what to do with nuclear waste? The problem with spent nuclear fuel is that it's really radioactive. These leftover radioactive materials can persist in the air, soil, and water for thousands and thousands of years and damage the DNA of living organisms, causing cancer and other health conditions. For a while, actually quite a long time from 1946 to 1993, to be exact, many countries just dumped radioactive nuclear waste into the ocean. This was consequently banned, and you can imagine why. Instead, nuclear waste can be buried, but there's problems with that, too. Nuclear waste can still leak into soil and water if it isn't properly contained. So where do we safely bury it? Well, nowhere really. Radioactive spent fuel is stored all over the world in various containment systems, but none of them are truly longterm. Alternatively, spent fuel rods can also be recycled and reprocessed where unused uranium is separated from spent nuclear fuel. However, this reprocessing is quite expensive and dangerous. Reprocessing is often much more expensive than storing or disposing of spent nuclear fuel, and it still results in a substantial amount of leftover radioactive materials that still need to be disposed of. There's no perfect solution when it comes to energy production, though. Any kind of electricity production has its own benefits and drawbacks. But Pickle Place's Atomic Burger is quite perfect, and I think I'll eat one now.