Powering a house for 34 years with 1 kg of fuel ~ Nuclear Energy
If you’re reading this article, it’s probably because of either 2 reasons:
a) You’re actually curious about nuclear energy
OR
b) the nuclear jokes you crack with your friends are getting old and there’s no way to avoid the topic now.
To be honest, nuclear energy isn’t that complicated. And no, it’s not all about bombs and explosion. There is a brighter side — nuclear energy could be used for mass destruction but not all the time. It’s actually very efficient when it comes to producing electricity. In fact, nuclear energy meets around 10% of the world’s energy demand and it’s the world’s second largest source of low-carbon power with 445 nuclear power plants globally.
It’s an emerging technology that can be the future of sustainable energy. To back that up, in 2019 nuclear power alone generated 10.4% of global electricity. So trust me, it’s got potential. Unlike fossil fuels, nuclear power doesn’t really emit greenhouse gases — however they do have a slight disadvantage. But before we get to that, we’re gonna have to understand what happens behind the scenes.
So here’s a simplified guide on nuclear power 💣
In simple words, the term ‘nuclear energy’ is defined as the energy in the nucleus of an atom. To jog your memory — an atom is the smallest unit of matter and is made up of electrons (negative charged), protons (positive charged) and neutrons (no charge).
The nucleus consists of a protons and neutrons which are held together by an energy (aka strong/nuclear force). The protons and neutrons inside of the nucleus are held together by the strong nuclear force, which balances the repulsion of the Coulomb force between protons. Nuclear energy can power millions of homes and it’s super efficient.
However, to obtain that energy it’s not as simple as breaking a twig. There are 2 main ways to release that energy from an atom: Fusion & Fission
No matter the process, they both use a set of machines to produce and control the reaction called ‘nuclear reactors’. Most of the time, nuclear reactors are used for Nuclear Fission. Fission is much more common because it’s much more easier to control. Whereas in fusion, there’s a higher possibility of a city blowing up.
Let’s start of with fission
Fission is currently everyone’s favourite. It’s the new hot thing in the market, with 443 nuclear reactors operating in 30 countries around the world. In short, it’s popular because it’s safe, available and inexpensive (in some parts) — nuclear power plants are expensive to build but affordable to run).
Nuclear Fission is a superhero in everyone’s eyes for a reason. It’s a process in which the nucleus of an atom is split. When the nucleus is literally cut in half it releases all kinds of things, including energy in different forms such as — visible light, X-rays, and gamma radiation.
In short — Fission is one heavy nucleus splitting into two lighter ones. Inside of a nucleus is nucleons (protons & neutrons) accompanied with a massive amount of energy. To obtain that energy, neutrons are bombarded with neutrons, therefore splitting the nucleus, and releasing that energy.
However, a nuclear reactor doesn’t just work by snapping your finger (Trust me, I wish they could). Instead, they use a fuel to power it up — usually Uranium-235. Though this element is a non-renewable source, the atoms of the Uranium-235 split easily.
The uranium that you find in nature isn’t really fit for this process. Natural Uranium comes with an atomic weight of 238 → 92 protons & 146 neutrons. To put this element in a better shape, we enrich it.
This part of the process is called “Enrichment”. You see, 1 in every 140 uranium nucleus, there lacks 3 neutrons, making it U-235. Uranium Enrichment is dividing U-238 from U-235 which is a lighter isotope that’s tightly bound. This is often lead by forcing a gaseous uranium hexafluoride compound through centrifuges, a device used to separate particles according to certain features.
- Isotope: Atoms of the same element that have different number of neutrons
It all starts off with Uranium-235 absorbs a neutron. Pellets of the fuel uranium is bombarded with neutrons and only one is absorbed. As a result, it forms a highly unstable compound nucleus as Uranium-236. This triggers a reaction, and U-236 begins to split into 2 lighter nuclei (fission products).
But that’s not all! The 2 fission products have now transformed into different elements; Barium-141 and Krypton-92. And they say that there’s no such thing as magic! Just kidding, but the reason why these particular elements are the outcome is since Barium has 56 protons and Krypton has 36 protons. Now, let’s do a little math — 56 + 36 = 92. Oh hey, that’s the same number of protons as U-236 (92 protons).
Now, hang on. There’s more.
On top of that, 3 neutrons are released. Since the 2 fission products are Barium-141 and Krypton-92, that results in 233 neutrons. The compound nucleus U-236 and the sum of neutrons of the fission products have a difference of 3 → meaning 3 neutrons will be released to balance that equation.
As a quick summary — 4 things are released during a fission reaction
- Fission Product 1: Barium-141
- Fission Product 2: Krypton-92
- 3 Neutrons
- And a massive ton of energy (aka binding energy in the form of kinetic energy)
The neutrons that have been released by previous uranium fission reactions hold so much energy that it collides with other nuclei of the fuel. It’s almost like a domino effect. Only a fraction of the released fission energy goes into speeding up neutrons. 1 in every 3 neutrons that are released are absorbed by neighbouring nuclei. Then this process repeats.
This is called a chain reaction.
At the same time, the radiation (energy) that’s obtained from fission, helps heat up a cooling agent, usually water. When a large amount of heat is combined with water, it becomes steam. This steam is then passed through turbines, generating electricity and powering cities.
But that’s not all, there’s a catch! Nuclear power has the potential to produce ALOT of electricity. The only difference between a nuclear weapon and nuclear power plants is that nuclear power plants can control the chain reaction. If a chain reaction is not tamed, it can potentially melt the uranium. That’s is called “meltdown”. (and let’s hope that it never occurs!)
To avoid a meltdown, most reactors consists of a cooling agent, and we normally use water. But that’s not enough! So, we use control rods. It’s exactly how it sounds — they’re basically rods made of materials that absorb neutrons. Along with control rods, there’s also a fuel rod of uranium which provides fuels. This way, the reaction is balanced.
The fission process generally occurs when a large heavy nucleus is on the brick of stability. Meaning that there is a level of imbalance in the nucleus between the Coulomb force and a strong nuclear force. To split the nucleus, it’s struck by a low energy thermal neutron, transforming into a much more stable product.
There are different types of Fission Reactors, and one of the most commonly used is the Light Water Reactor (LWRs). The one that has been described all this time is actually a LWR — which is a reactor that are cooled and moderated with water. There are several different resources that can be used as a cooling agent, but water seems to just be the most efficient, and produces electricity in a controlled process. But here’s the main difference, light water reactors heats up water using an artificial chain reaction.
Fun fact: Normally, the moderator is the same thing as the coolant, which is water.
Fission is not the only option. In the complete opposite direction lies another method, called fusion.
To understand Fusion, let’s look into an example. That big yellow thing in the sky (the sun) has been burning for billions of years only because of one main reason, fusion.
Fusion is a thermonuclear process — this means that the atoms have the be VERY hot or at a high temperature, that electrons are basically ripped apart from the nucleus. This creates a plasma where electrons are not glued to their nucleus, and roam around freely.
As I said, it needs to be at a very high temperature which results in particles moving at a high speed. Just like how particles repel same charge particles, nuclei (filled with protons and neutrons) repel each other. However, since the pressure is so high, two nuclei tend to collide against each other.
For stars like our Sun, it’s a bit of a different story. Due to their massive size, the pressure core causes the heat to squeeze the nuclei together.
Unfortunately, in a fission reaction, you don’t get everything you think you see. By that, I mean the mass of nucleus is different from the sum of mass of protons and neutrons. If you were to add up all individual masses of nucleons and then compare that to the total mass of the nucleus, there is a difference. That difference in mass is known as a “mass defect” which is actually in the form of energy that holds the nucleons together.
- Mass defect: the difference between the total mass of nucleons and the entire nucleus
In a fusion process, lots of energy is released because the total mass of the newly created nucleus is less than the mass of the 2 lighter ones. That missing mass becomes energy.
Here’s a quick masterclass of how the sun works:
There are two main forces that are involved in the sun’s nuclear fusion → electromagnetic force and strong nuclear force
- Electromagnetic force: the flow of a force produced by a magnet
- Strong Nuclear Force: The force between protons and neutrons
91% of the sun is made up of hydrogen, and when heated, it changes its form of state. Hydrogen is converted from a gas to a plasma in which electrons are separated from its nuclei. In an atom, an electron always surrounds around a nuclei, however the temperatures in a sun are so hot that electrons are basically pulled off.
One of the main reasons for why fusion could be difficult to induce, is because strong repulsive electrostatic forces located between a nuclei prevent other nuclei to collide. Just like how particles with the same charge don’t emerge, 2 nuclei (that are positively charged) tend to repel each other.
As I said before, the temperatures at the core of the sun are extremely hot that a nuclei is forced to fuse together. The higher the temperature, the faster the ions move — reaching a speed at which fusion occurs, and energy is released.
When 2 hydrogen nuclei emerge, they form a helium isotope. As a result, 0.645% of the mass is released in the form of kinetic energy and carried away with an alpha particle. It can also be transported in other forms of energy, such as electromagnetic radiation (which the sun does).
Well, that’s all! That’s what happens up here in the sun. But what about the earth? By understanding how the sun works, certain techniques have been developed to basically create a small sun down on earth, and attain energy from it. I mean, is it true that we can literally bottle a sun?
To produce a fusion reaction, industries currently use different types of fusion reactors. The 2 main reactors being used are: Magnetic Confinement & inertial Confinement.
1. Magnetic Confinement
This specific type of fusion reactor uses magnetic field to compress the plasma (specifically to confine the movement of deuterium-tritium plasma) in a doughnut shaped chamber where the reaction occur. These devices use superconducting electromagnets which are cooled and controlled with the element, helium.
The magnetic field that’s induced prevents the particles from colliding against the walls of the reactors — this also helps maintain the speed of the nuclei.
2. Inertial Confinement
The second type is a bit different from Magnetic Confinement, since it uses pulses from super-powered lasers to heat the surface of the fuel. This rises temperatures for the pellets (fuel), making the nuclei so hot enough to fuse.
In an I.C reactor, the fuel is stored in a Hohlraum which has walls that are in radioactive equilibrium. The lasers that are targeted towards this small storage, stores that heat reaching 100,000,000 degrees celsius causing nuclei to collide against each other.
Magnetic Confinement uses magnetic/electric fields to heat hydrogen plasma. Meanwhile, inertial Confinement uses laser/ion beans to the plasma. Both Inertial and Magnetic Confinement do they same thing, but it’s about the method used.
The main fuels that are used in nuclear fusion are deuterium and tritium, which are both isotopes of hydrogen. Deuterium is extracted from seawater, meanwhile tritium can be transmuted by lithium which is commonly found in nature. However in fission reaction, the fuel is uranium — and a typical nuclear reactor uses 200 tons of uranium every year
But, how do people even chose a fuel? More importantly, how do they know it’s the right fuel?
There’s a very simple rule that determines the element that should/should not be used for such reactions. For fission reactions, the nucleus is heavier than iron-56, it will tend to break into 2 or more smaller nuclei. However, if it’s lighter than iron-56, it will be used for a fusion reaction.
The reason nuclear power plants use uranium is because it is on the brink of stability, making it a perfect material for a fission reaction.
Although Uranium, Deuterium and Tritium are widely used sources, they aren’t the only options. Several nuclear power plants have traded modern reactors for a thorium-based reactor. Yes, that’s right — thorium is a potential source that could be used as a fuel and dethrone uranium for many reasons.
First of all, thorium is much more concentrated, and there’s 3 times more thorium available in the Earth’s crust than uranium.
- Thorium is the 41st most abundant element in the Earth’s Crust
Second, liquid Fluoride Thorium Reactors (LFTRs) don’t use water for cooling so there’s no possibility of an hydrogen explosion. Lastly, thorium is a radioactive element which emits alpha particles which is less harmful than uranium’s gamma particles. So, why is that a good thing?
Well, the only disadvantage of nuclear fission is that it creates radioactive waste. Radioactive waste is known as element or substances that have unstable nuclei. For radioactive waste to become stable (and safe), it takes hundreds of thousands years and it does this through radioactive decay.
- Radioactive decay: a process in which unstable nuclei loses energy by emitting particle and radiation.
For example, Uranium decays by emitting gamma particles (this is known as gamma emission), and thorium decays through alpha emission. But thorium is picked over uranium since the radioactive waste is only toxic for 300 years (which is much better than a thousand years!).
On top of that, thorium can provide much more energy than uranium in a fission reaction.
**1 ton of Thorium = 35 Tonnes of Uranium = 4 million Tonnes of Coal**
A thorium reactor (LFTR) is a bit different from usual fission reactors. Thorium-233 is combined with fluoride salts in the reactor core.
The element is originally Thorium-232, and by absorbing a neutron it becomes Thorium-233. Along with Thorium, salt tends to absorb some of the heat and neutrons.
Due to the temperature, the salt melts into a molten state which runs a heat exchanger. This heats an inert gas such as helium, and generates electricity by a turbine. Next, the radiated salt flows into a processing plant, which separates the uranium from the salt. The uranium that is separated is then sent to the reactor’s core for the fission reaction.
Within the core, Thorium-233 beta decays (emits a beta particle) and transforms into protactinium-233, and after an addition of 27 days of beta decay, it becomes Uranium-233.
Then, it splits into 1 fission product, and neutrons.
Though it’s a longer process, thorium don’t have meltdowns and produce higher amounts of energy than uranium. As a bonus, cost of fuel is significantly lower than a modern fuel reactor. The salt normally costs $150/kg and thorium costs $30/kg. The main reason why people lean more against thorium, is because it’s available, cheap and efficient. You see, the more popular thorium becomes, the cheaper it will be. It’s a real deal!
Unlike solar or wind power, nuclear energy is promising however the radioactive waste really puts a second guess. Although nuclear energy doesn’t produce greenhouse gases, it creates radioactive waste which can cause serious damage to the environment. Radioactive waste in normally stored in a concrete and steel pools, and used fuel is stored in dry casks.
On the bright side, nuclear fission is 8,000 times more efficient at producing energy than fossil fuels — now that’s a big win. A modern nuclear reactor generates enough electricity from 1 kg of fuel to power an average American household for about 34 years. Though it comes with a lot of flaws, it has the ability to produce electricity in an inexpensive method using resources such as uranium. The point is, with billions of people polluting the world everyday it’s time to change to a much more effective solution. And that’s nuclear power! It has the potential to provide a massive amount of energy to be divided against several people. Imagine that, in just a split of an atom we can power an entire city! Solar, Wind or Hydro are great ways to generate electricity, but the most reliable is nuclear, it can just be the best chance in saving the planet!
Hey, you made it to the end! I’m Sanvi, and I’ve been working on hydrogen as a fuel for automobiles in order to adapt to a sustainable environment. You know what’s a great idea (other than solving climate change) — connecting!
Let’s Connect!
Email: Sanviiraoo@gmail.com
Linkedin: https://www.linkedin.com/in/sanvi-rao/
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