If nuclear power plants boil water to turn a turbine to make energy then why do they make more energy than a coal power plant that does the same?
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Key term: *Energy density*. It’s the amount of energy per unit mass that you can get out of a given fuel.
The energy density of fuel-grade uranium undergoing fission is several orders of magnitude greater than a similar mass of coal, because nuclear fission gives off VASTLY more energy per reaction than regular old oxidative combustion (burning) of coal (or any other hydrocarbon for that matter).
>One uranium fuel pellet creates as much energy as one ton of coal, 149 gallons of oil or 17,000 cubic feet of natural gas.
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>-[https://www.nei.org/fundamentals/nuclear-fuel](https://www.nei.org/fundamentals/nuclear-fuel)
If that’s tl;dr – **You can boil a f- of a lot more water with a few grams of uranium fuel undergoing fission than you can with a literal TON of coal. Because nuclear fission.**
Nuclear reactors are using fissile fuel (uranium) that is able to be split into other elements. When this split happens, the mass of the resulting elements is slightly smaller than the mass of the original uranium.
The missing mass has actually been converted directly into energy by breaking the atomic bonds that were holding the original atoms of uranium together.
This works according to Einstein’s famous equation .. **E = M x C****^(2)**
In this equation, **C** is the speed of light .. which is a very big number. Squaring it gives you a very very big number.
So nuclear reactors can take a very small amount of uranium mass (**M**) and convert it into an extremely large amount of energy (**E**).
The turbines are scaled up because the energy output is way greater. I worked in power plants all over for 15 years. Everything in PWR (pressurized water reactor) is bigger than a coal or gas fired (even smaller) fired power plant.
energy density, same as why coal or oil could produce more than wood. 1KG of nuclear fuel has more potential (or capture-able) energy than 1KG of coal.
The amount of energy in uranium is not just more than coal, we are talking grams of uranium vs tons of coal for the same energy output.
Also, nuclear plant is a much bigger and more complicated investment than a coal plant, so the economics make more sense to be at a larger scale.
The size of a coal plant can vary by a lot, because they just need a furnace and turbines. You can have massive plants or smaller peaker plants that only spin up when needed during peak hours. So the avg nuclear will be larger than the avg coal plant. But the largest coal plants are similar size to Nuclear ones.
Because nuclear fuel has a lot of energy in it.
Let’s say you boil water using wood. Wood’s OK at burning, but it burns up quickly. You need a lot of wood to boil water.
If you had coal, coal’s better at burning. You need far less coal to boil the same amount of water.
And nuclear fuel has even more energy than coal. A Uranium rod doesn’t burn, it’s just a piece of metal that gets hot. And it stays hot for a very long time, relative to its size.
To go in depth, you’re comparing the energy stored in chemical bonds with the energy stored in nuclear bonds. When you burn coal you are breaking up chemical bonds. These are easy to form, easy to break, and don’t produce that much energy when broken.
But nuclear plants rely on nuclear fission. On breaking the much smaller bonds inside the atom itself. These bonds were formed inside dying stars. When they break, and with fission they slowly break apart naturally, they release a lot of energy.
A coal plant can easily be just as powerful as nuclear plant or more and if you are looking for most powerful then world top 6 largest power stations are actually all hydroelectric dams. Source of energy does not dictate how large a plant you can build.
The question of nuclear vs coal should instead be why does one use so little fuel and the other so much for same amount of energy. The energy densities are drastically different because they are driven by very different reactions. One is working on nuclear binding energy, the other is working off of chemical reactions powered by electron binding energy which is much less. To extend the comparison a hydro dam works off of gravitational potential energy which is by far the weakest and look how much mass that has to pass through to make same amount of energy.
Reactors are expensive. So to offset the construction cost, we started building bigger and bigger plants. The cost of a bigger reactor isn’t that much more than the cost of a small reactor. Most of the cost is in the paperwork and licensing.
Side note: the focus now is to make smaller reactors, where they are simple enough that the cost to build them drops, so we can build modules instead of giant behemoth plants.
Nuclear power plants are typically very large capacity because they have to be to be economical in the context of civil power generation, where they must compete against natural gas powered plants. If you look at the field of military nuclear reactors such as the ones found in aircraft carriers and submarines, they are much much smaller, which is possible because cost-efficiency isn’t their top priority. There is a huge upfront cost to build a nuclear power plant, but doubling the capacity of the plant does not double the construction cost. There is an economy of scale where by building a larger, higher capacity plant, they achieve a lower cost on a per-megawatt basis.
Hydroelectric power plant utilize gravitational potential energy to generate power.
Coal/Natural Gas plants utilize chemical potential energy to generate power. The chemical energy is stored in the binding energy of molecules due to the electro-magnetic force.
Nuclear plants make use of the binding energy of atomic nucleons which are based on the nuclear strong force.
In general, the stronger the force, the more energy you can extract per weight of fuel. The relative strength of the forces are:
Stong Force = 100 * Electro-magnetic force = 10^38 gravitational force.
While you can’t use these numbers without some modification, they show you the qualitatively the amount of fuel required to generate the same amount of energy.
Hydroelectric requires enormous amount of water (the “fuel) falling a good distance to generate the energy. Dams are huge!
Coal and gas fired plants require significantly smaller quantities of fuel to produce their energy.
Nuclear plants require very little actual fuel to generate their energy. Not easy or cheap to make that fuel however.
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