How does a nuclear power plant generate electricity? Where does the radiation come from when there are failures?


How does a nuclear power plant generate electricity? Where does the radiation come from when there are failures?

In: Chemistry

Nuclear power plants create a controlled nuclear reaction to generate heat. The reactor is cooled by water which creates steam. The steam powers a turbine which generates electricity. Basically nuclear power plants are just steam powered generators where the heat source is a nuclear reactor as opposed to fossil fuels such as coal, oil, etc. The radiation is associated the materials used to create the reaction. (Perhaps someone else can better explain the radiation).

The nuclear plant heats water to make steam, which drives a turbine (like a coal plant) to make electricity.

Failures that leak radiation are super rare, like only two worldwide. Most radiation comes from chain-reaction byproducts. These are the pieces of split Uranium atoms.

Current nuclear power plants operate by maintaining a controlled nuclear fission reaction in its core. The breakdown of Uranium produces heat, which heats water to steam, and that steam turns a turbine and generator to produce electricity.

The radiation from a failure comes from contaminated cooling water (containing radioactive material) and materials from the core.

At Chernobyl the reactor exploded due to a design flaw and inadequate safety precautions. This explosion spread nuclear material over much of Europe.

A meltdown occurs when the core cannot be cooled down adequately enough and melts the surrounding core. Modern nuclear facilities have numerous safety features to prevent this from allowing nuclear material in the core from escaping into the atmosphere.

A nuclear reactor uses a chunk of stuff that wants to explode. They jam pencils through it to stop it from exploding. It still gets super hot (but not not enough to melt the pencil lead), and they use that heat to make steam. They use the steam to spin big motors that make electricity.

Electricity can be generated by having metal move inside of a magnetic field. This is how a turbine works, just spinning a metal rotor inside of a magnetic stator field.

Nuclear plant fuel is generally Uranium 235. This isotope is a little unstable, so neutrons are occasionally released from its atomic nucleus. The moderator of a reactor will slow these neutrons down enough by causing them to bounce around, losing energy and transferring it to the water coolant in the form of heat which causes the coolant to boil into steam which pushes the turbine to create electricity before it condenses back into water. When the neutron slows down enough from all its bouncing around, it can then smack into the Uranium 235 nucleus just right to cause it to split apart, releasing a lot more neutrons to help fuel the reactor, other types of radiation, and fission fragments which are also unstable and release radiation.

Normally, all the Uranium and fission fragments are contained in fuel cells and cannot escape. If the plant had a bad enough accident, the fuel cell walls could melt, releasing the radiation into the coolant. If the pressure builds enough in the coolant, the pipes could rupture and release that radioactive material into the containment building. If that pressure builds up enough, it would finally release into the public.

There are two nuclear reactions that release energy: fission and fusion. The former means splitting of the atom and the latter means the opposite. Fission releases much less energy but fusion takes a lot of effort to do and control.

The way nuclear power plants generate electricity is actually pretty simple: energy released is used to heat up water, which in turn turns to steam and turns a generator turbine.

If there is a failure, radiation could come from the radioactive (unstable) materials used in the process. Or the waste materials which we end up with after the atom is split. There is always radiation coming out of them but they are always under control if everything goes to plan.

– Nuclear reaction emit a lot of heat and so we can use that heat to generate steam, which can pass through a turbine that spin and generate electricity. It’s the same way we generate electricity from fossil fuel.

– Nuclear plant use Uranium, which we find in natural in two form U238 and U235. They respectively have an half life of 4.5 billion years and 700 million years. So they take a really long time to decay and are not really dangerous. But if you emit fast neutron near them they can absorb that neutron. If a neutron hit some of that Uranium with enough energy it will split it. This emit radiation, which we absorb as heat, but it also create two smaller atoms that are a lot more unstable than natural uranium and emit more dangerous radiation. Most of our nuclear power plant use pressurise water, to control the reaction. The reason is that water is really good at that job but at high temperature it become a gas, so we need to pressurize it to keep using it in the hot reactor. The thing is that if there is a problem with the water, the reaction isn’t keep under control, the temperature rise and can melt the core which can spread the radioactive material since it melt the containement.

Okay, so…imagine a big fire.

Now, imagine that we put a big tank of water above that fire so that the water heats up.

The water heats up enough for it to turn from water into steam. The steam flows up some pipes and spins some fans that we call turbines. The turbines spin really fast that generates electricity.

Once the steam passes through the turbines, it collects up in some higher pipes that pass through cooling areas, that drain off the heat and allow the steam to turn back into regular water. At which point, the water flows back down other pipes to rejoin the big tank at the bottom.

Now, this would be a terrible way of generating electricity, because you have to keep feeding fuel to the fire to keep the water hot enough to turn into steam. It’s incredibly inefficient in that it takes way too much effort to keep the fire hot. Too much fuel, too much work, too much smoke, etc etc etc.

But, what if you had a natural element that stays hot on its own? In fact, it’s so hot that you have to work to keep it cool by inserting really dense lead and other elements in there to soak up the heat.

You wouldn’t have to feed the fire to keep it hot. It stays hot on its own.

That’s basically what a nuclear reactor is. The fuel is incredibly hot because it’s slowly changing from one element into another and the changing process produces a whole lot of heat.

There’s a few different kinds of fuels that are used, some are better than others, but it’s basically a big ol’ nuclear fire heating water into steam that’s used to spin turbines that generate electricity.