Como Funcionam as USINAS NUCLEARES? Gerar ENERGIA com ÁTOMOS

With the high demand for energy that we are seeing and the future with the electrification of vehicles, we realize that our energy generation may not be enough to guarantee energy for everyone. But a small method with a high power generation could be a solution to this problem. Today I will tell you what a nuclear power plant does and how it works.

What's up engineering lovers, my name is Igor Felipe and today's subject is perhaps controversial in many ways, so let's talk about nuclear energy. Once the studies of radioactivity and the energy it could provide became more relevant, this knowledge was being used in several areas and devices. A great example that you all must know are the famous Little Boy and Fat Man.

If you don't know what I'm talking about, these were the names of the two bombs that were used in the attacks on Hiroshima and Nagasaki in WWII. And the first idea that we have when talking about radioactivity, are tragedies and accidents and this does not collaborate with nuclear energy, but the truth is that using radioactive materials can have its good side. In 1942, the first nuclear reactor with a self-sustaining chair reaction went into operation in the city of Chicago.

It was developed by Italian physicist Enrico Fermi using the nuclear fission method. But what is this nuclear fission? To talk about it, we have to understand how we can generate energy using radioactive materials.

Atoms are small basic units that make up the matter of the universe. Basically, if we are splitting an element, the atom is the smallest part into which an element can be split without losing its chemical properties. Inside the dense nucleus of an atom, we have two particles, the protons and the neutrons.

What keeps this nucleus stable and interconnected is the nuclear force between these protons and neutrons, and this nucleus has a lot of accumulated energy and that's exactly the energy we want to use. To get this energy, we take it from inside the nucleus of the atom, which is why we call this energy nuclear. For that, we have two types of atomic reactions which are nuclear fusion and nuclear fission.

In nuclear fusion, atomic nuclei fuse and release a lot of energy. This release of energy follows the famous formula elaborated by Einstein, which correlates energy and mass. And this energy release occurs because during the process, a small portion of mass is consumed, thus releasing a giant amount of energy.

Want an example of where nuclear fusion occurs? Our sun is the greatest example of nuclear fusion that we know of. It is composed of 73% hydrogen, 26% helium and 1% other elements.

What happens in our sun is the fusion of hydrogen atoms, thus giving rise to helium atoms. This releases a lot of energy, but the problem with using this method in a nuclear power plant is controlling all that energy released, because it's no use generating a lot of energy if the reaction is uncontrolled. We have projects to build a nuclear fusion reactor and we have a video talking about testing this type of reactor, and I'll leave him a card at the end of this video.

But we have another method of atomic reaction that produces a little less energy compared to nuclear fusion, but still produces a lot of energy, which is nuclear fission. Unlike fusion, nuclear fission splits an atomic nucleus into smaller atomic nuclei. And when we do this division of this atomic nucleus, that also releases energy.

In this method, we bombard the nucleus of the atom with neutrons, generating an instability and it fragments into smaller nuclei. But something interesting happens there. If we add the masses of the atoms after the division, we will notice that it is less than the mass of the original atom.

And this “lost” mass is actually released in the form of energy. Again, Einstein's famous formula. And nuclear fission is the method we use today in nuclear power plants.

To better understand what happens inside nuclear power plants, let's use uranium 235 as an example. Once we place uranium 235 inside the reactor of a power plant, we bombard the atom of this uranium with a neutron. In this way, uranium 235 captures this neutron and becomes unstable.

With this instability, the uranium atom undergoes nuclear fission fragmenting into 1 barium atom, 1 krypton atom, 3 neutrons and a lot of energy. And the whole point is that since we launch only 1 neutron against the atom and that reaction releases 3 neutrons, this generates a chain reaction in other neighboring uranium atoms. If we think about it, this reaction generating several neutrals ends up being a runaway reaction as long as we have uranium atoms.

In order to control this reaction, we need a moderator material and for that, some chemical elements such as boric acid or cadmium metal are used. What these chemical elements do is absorb the neutrons from the uranium nuclear reaction controlling the reaction. This makes these elements serve as an accelerator or brake of the reaction.

For example, if we insert cadmium metal into the reaction, it absorbs the neutrons from the uranium fission reaction and brakes the entire process. Now if we want to speed up the process, we strip out the cadmium, and let the chain reaction take over. And this whole process is used to produce energy from nuclear reactions, but this energy is not quite what comes to our homes.

Remember when I said that the fission reaction generates energy? Yeah, all the energy generated by the nuclear reaction produces a lot of heat, and that's where nuclear power plants come in. We think that this energy is already converted into the electrical energy we use, but the truth is that a nuclear power plant works like a thermoelectric power plant.

Yes, a nuclear power plant is still a thermoelectric plant, but instead of burning fossil fuels to produce heat, they use the heat of the nuclear reaction. A nuclear power plant is normally composed of three phases: primary, secondary and cooling. The primary phase, we have a reactor inside a shielded pressure vessel, where exactly that chain reaction that I have already explained takes place.

In this process, chemical elements such as cadmium are used to control the acceleration and deceleration of nuclear fission. In this case, if we insert metallic cadmium rods inside the reactor, we decrease the nuclear reactions and the reactor cools down. Now if we remove the cadmium rods, the nuclear reactions increase and the reactor heats up.

As a result, the heat from this reactor can heat up liquids such as water, as if it were a pressure cooker in a shielded system. In the secondary phase, this water that has been heated by the heat of the reactor turns into water vapour. This high pressure steam is then channeled into a turbine.

This turbine is then connected to an electrical generator, and it is through this generator that the electrical energy that we can use is produced. After the water vapor has passed through the turbine, it enters the cooling phase. In this phase, we want to transform the water vapor into liquid water to be reused again in the process.

So, a cooling system works like a giant car radiator, which normally also uses water as a coolant. This cooling water can come from rivers, lakes and even the oceans. When we look at those smokestacks at nuclear power plants, it's exactly that water from the cooling system that's being evaporated.

We call these giant chimneys cooling towers, which serve both to store water and to evaporate the cooling water. But Igor, isn't this water radioactive? The water that is used to drive the turbine and has contact with the reactor is in a shielded process, that is, it is re-circulated inside and has no contact with the external environment.

The steam we see from the cooling towers is simply water that was used to condense and cool the secondary system. That is, the steam we see from a nuclear power plant is not radioactive and is simply water. And the point is that this model produces clean energy, as it does not release any smoke from fossil fuels into the environment.

The result of this process basically produces water vapor in the environment. However, we cannot forget about the radiation reject either. The material that is discarded from nuclear reactors and even the materials used by the plant's staff such as aprons, gloves and masks form what we call nuclear waste.

This nuclear waste is not thrown into the environment, and in the case of the tailings from the reaction of the reactors, they are stored in concrete bunkers and the teams' disposable materials are buried in deep ditches. There is a great fear of using nuclear power plants, mainly because of the famous disasters that we know as Chernobyl in Ukraine and the most recent one in Fukushima in Japan. But the point is that if we have control over the safety systems of these plants, they can represent an interesting way of generating energy worldwide.

But there is another problem which is the cost. Nuclear power plants have the highest power generation values ​​per megawatt-hour (MWh) compared to other power generation models. That is, when using nuclear energy, be sure that the value of your electricity bill will be very expensive.

The whole question is about investment, time, resource and especially the installation area. A hydroelectric plant, which today is the cheapest method of energy production we have in Brazil, requires a huge area to form its reservoir. Solar parks and wind farms also require a large area to install the panels and wind turbines.

A nuclear power plant, on the other hand, needs a very small area to be installed. That is, the idea is to produce a large amount of energy in a small space. And who knows, we will see new nuclear plants appear here in Brazil with the increase in demand for electricity.

Here on the side there are two videos, one about the nuclear fusion reactor that I mentioned, and another explaining how a hydroelectric plant works, so take the opportunity to check one of them. This is your time to like the video, share it on your social networks and consider subscribing to the channel to follow our work. And that's it my friends, a big hug and see you in the next video.