4. Applications of Nuclear Physics
How do we use nuclear physics in medicine?
You may be thinking - “Medicine? And nuclear physics? They can’t be connected!” You actually probably aren’t thinking that but whatever. Nuclear physics is super duper important in modern medicine.
Radioactive tracers - So, remember radiation and all that jazz? Brilliant. Let’s take a radioisotope (e.g. Fluorine-18) and attach it to a biologically active molecule - molecules our bodies recognise or use naturally in important processes like respiration - (e.g. glucose). We now have a tracer e.g. Fluorodeoxyglucose (Fluorine and glucose said in a fancy way) or FDG. This tracer is now injected or inhaled. 🫢
But why? Why would you eat up some radioactive stuffs? Tracers are used to find where specific biological activity happens. The tracers move through the bloodstream and because they are connected to biologically active molecules, the body recognises them as normal. So for FDG, it behaves like glucose. Cancer cells love glucose so if a tumour is present, the FDG accumulates there. The Fluorine-18 in FDG emits a positron (after undergoing beta plus decay) which quickly meets an electron and the two annihilate* which releases two gamma rays. A PET scan** (Positron Emission Tomography) will then detect the gamma rays and build a 3D image of that area, which shows us that there’s an abnormal accumulation helping us to diagnose the patient.
Of course that’s only one type of tracer. There are many - Indium-111, Iodine-123 etc - and they are all used to look at different things. Indium is used to detect infections and inflammation, Iodine-123 for thyroid function and thyroid cancer and so on.
But wait a minute. It’s radioactive. Am I not going to like die if I ingest it? No. No you wont. Radioisotopes used in medicine often have short half-lives (they become stable quickly) and most emit gamma radiation (less ionising). It’s done in a controlled environment and the benefits outweigh the risks so don’t worry. You’ll be just fine. Probably. 👍
*annihilate - when a particle and its antiparticle meet e.g. an electron and a positron or a neutrino and a antineutrino, they can annihilate. This means they destroy each other and convert their mass into energy (remember E=mc^2).
**There is also something called a SPECT scan (a Single Photon Emission Computed Tomography - geez, these are some big words). When a tracer like technetium-99 is injected and it emits gamma rays directly (without the positron stuff), a gamma camera is rotated around the body to create 3D images. SPECT is cheaper but less detailed and is used for hearts scans, brain scans, bone imaging etc. PET scans are more expensive but more detailed and are used for cancer detection, brain function, heart disease etc. So, yeah, there’s a quick overview of the scans.
Ok, so radiation can help us diagnose. But, it can also help us to treat.
Radiotherapy - This is when high-energy radiation is used to kill or damage cancer cells, without too much healthy cell damage. There are two different ways we go about this.
Numero uno: The most common method of radiotherapy is External Beam Radiotherapy (EBRT). This is where an outside machine shoots radiation into the tumour. Most commonly, a linear accelerator (LINAC) is used to shoot x-ray radiation (not nuclear, but man-made electromagnetic radiation). This type of EBRT is the most common, and used for cancers all around the body. But then, for brain tumours and other head conditions, when you have to be especially precise and minimally damaging to healthy cells, a gamma knife is used (not an actual knife, it’s just very focused beams of gamma radiation - sharp, if you will). Cobalt-60 (a radioisotope) releases high energy gamma rays, and these are directed towards the tumour. This is a subtype of EBRT, known as Stereotactic radiosurgery (SRS) - it’s still of form of EBRT, just more specialised.
Numero dos: The second method is Internal radiotherapy (Brachytherapy). This is where a soldier is sent directly into the frontline, where all the action is. A radioactive source (like Iridium-192) is placed inside the tumour or super close to it. It releases mostly gamma radiation (sometimes beta) and it is great because it means healthy cells aren’t exposed to as much radiation. The thing is, it can only be used when the tumour is somewhere you can reach and is more invasive, making it less common. It’s mostly used for prostate cancer (Iodine-125 most commonly), cervical cancer (Iridium-192), breast cancer (again, Iridium-192) and a few others. Different isotopes are used, because they release gamma rays of different energies. If an isotope is more unstable and excited, it will release a higher energy gamma ray to get back to a zen state. For eye cancer (ocular melanoma) for example, lower energy gamma rays are required so the whole eye isn’t damaged.
Ok, so big words and stuff. But, how does this technology actually work? Cancer cells divide uncontrollably and have really bad repairing (healing) mechanisms, but healthy cells are more calculated and patient, and their repairing mechanism are much better. This means, after radiation enters the body, and causes damage to the DNA of cells, cancer cells are more likely to die out, whilst healthy cells are more likely to heal themselves and survive. Analogy time: let’s take two runners. C (cancer) and H (healthy). They both plan to run a race. A race to divide. Runner C already has an injury (poor repairing mechanisms) whilst runner H is in perfect shape. The race begins. But the thing is, it’s also a crazy hot day - the sun is blazing (radiation). Runner H takes time to stop, rehydrate, breathe, and is able to carry on through to the end. Runner C has already got an injury, but remains stubborn, no breaks, no hydrating, no chill time. Runner C faints. Too much damage, too little repair. Runner H finishes and wins, they’re calmer, and more fit.
So, radiation can damage and kill cancer cells, but cancer cells aren’t the only things that hate to see gamma rays coming.
Gamma Sterilisation - A radioactive source (usually Cobalt-60 - a fan-favourite) releases high-energy gamma rays. These gamma rays are directed at a product needing to be sterilised e.g syringes, surgical gloves, sutures etc. It then ionises molecules on the product, mostly water molecules inside microorganisms like bacteria. This forms ions and free radicals (ionised molecules which are highly reactive and unstable). These then start destroying stuff - like Godzilla in Tokyo or a bull in a china shop. DNA gets mutated, proteins degrade and cell membranes are damaged - this means that the microorganisms often die, which is the whole point of this. The product is now sterile. The great thing about gamma sterilisation is that it doesn’t require high temperatures so heat-sensitive items are fine and it can penetrate into solid products. So even if your syringes are fully sealed, they can be sterilised. So although gamma sterilisation is more expensive and it requires radioactive materials, it’s widely used today. And not even just in a medical setting: for food, cosmetics, other labware like petri dishes etc, and even spacecraft parts before launching (we don’t want to contaminate other planets with our Earth microbes).
Speaking of contamination (I’m going to talk about a different type)…
Irradiation vs Contamination: But wait. Won’t all of these products be radioactive after being exposed to the radiation? (You may not have thought that, but I needed a way to segue into an important point). No. No they won’t. Let’s talk a little about a key concept: Irradiation vs Contamination.
Irradiation is when you are exposed to radiation but you don’t come into contact with a actual radioactive material. You do not become radioactive. You may be damaged by the radiation (depending on the situation), but you do not, and I repeat do NOT become a glowing, radioactive zombie (you don’t if you’re contaminated either, but you get me).
Contamination is when a radioactive substance is actually on or in you. For example, you decide to eat some tasty uranium, because why not? In this case, depending on what has happened, you may be radioactive. Like the uranium will be giving off radiation from inside you, so people may want to stay away (don’t take it personally).
So that was a quick, but necessary, segue into irradiation vs contamination. To answer the question (that you may or may not have asked), gamma sterilisation is an example of irradiation - it does not make the products radioactive.
Ok, so that was medicine, a harder, more complicated section, but pretty interesting. Now, time to move onto dating (huh?).
Radiometric dating. No, not that kind of dating 🙄.
Radiometric dating is a method that uses knowledge of half-lives and radioactive atoms to figure out how old stuff it - like fossils and rocks. Here’s how it works.
Carbon dating - Carbon-14 is a rare isotope of Carbon (woah, really?). Cosmic rays from space (more on that later) hit nitrogen atoms, and they then turn into carbon-14 atoms. The carbon-14 atoms react with the oxygen in the atmosphere to form carbon dioxide. All living things take in carbon dioxide, and therefore carbon-14. When they die, they stop taking in new carbon and the remaining carbon atoms just stay there, decaying into nitrogen, partying, doing their thing. It is important to know that the ratio of Carbon-14 to Carbon-12 (the most common kind) in the atmosphere, is 1 to 1 trillion, and that the ratio remains the same (or about the same) inside all living things.
Now, the half-life of carbon is 5730 years, or around that area. Let’s take a fossil (has to have been living to take in the carbon) with 1 carbon-14 atom and 2 trillion carbon-12 atoms (carbon-12 is stable and doesn’t decay). By the way, these numbers are not at all accurate, but it’s easy to use them so…yeah. Ok, now the ratio here is 1:2 trillion. The original ratio was 1:1 trillion (in this case, 2 carbon-14 atoms and 2 trillion carbon-12 atoms) as it is in all living organisms, remember? This means the number of carbon-14 atoms halved (from 2 to 1, ridiculously). This means 1 half life has passed. So, the fossil is about 5730 years old (it’s getting up there, isn’t it?).
That’s how carbon dating works - an unrealistic, simplified version of it, but you get the concept. The less carbon-14 there is compared to carbon-12, the older the fossil is.
What about very dead rocks that have always been dead? Or super old stuff, like, I don’t know, the Earth?
Other dating - Radioisotopes with way longer half-lives are used, like potassium and uranium. Let’s take a molten rock. It’s not solid (as suggested by the word molten). All the gases escape from it, this includes argon. When the rock solidifies, potassium-40 atoms are trapped inside the rock. So to begin with, there is pretty much no argon, but some potassium. Let’s fast forward 1.3 billion years (1 half-life of Potassium-40). Half of the potassium has decayed into Argon-40. The ratio is 1:1. From this, we can tell that 1 half-life has passed. If the ratio was 1:3 (75 percent argon, 25 percent potassium), we would know 2 half-lives have passed, making it around 2.6 billion years old, and so on.
And it’s the same with uranium and lead, and other radioisotopes with super long half-lives. The oldest rock we’ve found using this method, is about 4 billion years old. And there’s a meteorite specimen that has an age of about 4.54 billion years old. And that is how we got the age of the Earth. How cool is that? Nuclear physics is literally the reason we know how old the world is. Gosh, it’s just brilliant.
A little extra - How do we know how many atoms are in stuff? We use something called a mass spectrometer. And what it does is it ionises the carbon atoms and whooshes them through a magnetic field. Lighter atoms like carbon-12 curve more, whilst heavier atoms like carbon-14 will curve less (because it’s the bigger, stronger one that doesn’t want to get pushed around). And so, the machine measures the curves, finds out which atom is which and counts the number of each in the sample.
What are nuclear-powered batteries?
Nuclear-powered batteries (or Radioisotope Thermoelectric Generators - RTGs - to be fancy) rely on radioactive decay. When a radioisotope decays, often, a high-energy particle is released e.g. an alpha particle. The particle particle hits surrounding atoms, causing them to vibrate. This produces heat. This heat is converted into electricity.
Yeah, that’s basically how a nuclear-powered battery works. It converts the heat produced from radioactive decay into electricity.
But (yes, another but), I’m confused. Let’s ask another one of the questions that make my teachers hate me: how?
How is the heat converted into electricity? I’ll try to keep this simple, because after all, this is nuclear physics for beginners. Not Sahara goes on tangent about other physics and hard stuff that makes everyone’s brains hurt.
Anyway, the heat is converted into electricity because of the Seebeck effect. What the huhu (a word created by my then-3 year old nephew) is that?
Basically, a core part of a nuclear battery is a thermocouple. Awwww. Sounds so romantic. Ok, let’s take 2 different conductive materials (conductive = ones that can carry electricity), which are often metals or alloys (which are mixtures of 2 or more elements where at least 1 is a metal). We’ll call them A and B. A and B are wires and are connected at one end. This is called the hot junction. At the other ends, A and B are connected to a circuit. This is called the cold junction (what a shocker). The hot junction is placed near the heat source (radioisotope decaying). Now, the electrons in the hot junction gain energy because of the heat. The cold junction is kept cooler using different scientific methods - this is to create a temperature difference. At the hot junction, the electrons are energised and feeling a bit claustrophobic. The guys at the cold junction are more chill and have less energy. This causes a push (a voltage) as the electrons at the hotter side move to the cooler one for a bit of space and to calm down. This process carries on in the thermocouple as the decay continues. The electrons keep pushing each other along the circuit. Boom. A current is born. #electricity #physicsissick #alrightI’llstopnow
This is called the Seebeck effect - named after the German physicist Thomas Johann Seebeck. What a guy!
Ok, we can move on now.
P.S. Please do look into this more, as it is quite interesting.
How is nuclear technology and knowledge used in space?
RTGs (again) - Remember RTGs from like, the last paragraph? They are used to power spacecraft such as the Mars rovers Curiosity and Perseverance, the Saturn explorer Cassini and even Voyager 1 and 2 - the first 2 spacecrafts to enter interstellar space (the space between stars, which starts where the Sun’s influence fades out - the heliopause). Basically, they’ve travelled pretty far. All of these have. And they are powered by nuclear batteries.
So, why are they used? Well, RTGs last for ages because of radioactive sources such as plutonium-238 having a half life of around 87 years. Voyager 1 and 2 were actually both first launched in 1977, they’ve been out here for almost 50 years!
Also, it’s a bit chilly in space. Well, maybe a bit more than chilly. The baseline is around -270 degrees celsius. I guess we could use the word “freezing”. Anyway, RTGs are great because they work in these less-than-tropical conditions. They can work in deep space, underwater, underground - they aren’t bothered. I can’t imagine solar or chemical batteries would feel the same.
RTGs are very reliable because they don’t have moving parts - they’re low maintenance (like me 🤭) and dependable. Oh, and they provide lots of energy in a compact size. Some advanced, new RTGs could even reuse nuclear waste.
I’m sure we can see why RTGs are leading the journey to space and beyond. They’re just super cool.
Nuclear spectroscopy instruments - I’m not gonna lie to you, I took one look at “spectroscopy”, got scared, and shut my laptop. But I‘m back, so let’s conquer it together. First, let’s address the big, terrifying elephant in the room. “Nuclear spectroscopy” in the context of space stuff, means using nuclear techniques to learn about what planets are made of (the elements, isotopes etc). There are a few different instruments we can use, but I’ll focus on 2 main ones: gamma-ray spectrometers, and neutron spectrometers.
Neutron spectroscopy: Depending on the size of the star, when it dies, it may go boom (explode). This is called a supernova. This releases high-energy particles (mostly protons, sometimes alpha particles and heavier nuclei) that just zoom through space, nearly at the speed of light. Other celestial bodies can give these off too, but supernovae are considered a main source.
These are cosmic rays (I told you we’d come back to them), and when these rays hit the surface of a planet (like Mars), stuff happens. More specifically, the high-energy particles cause something called spallation (WHY BIG WORDS WHY 😫). When they smash into the nuclei of atoms (on planetary surfaces), the nuclei can break apart, and release neutrons. Neutron Spectrometers measure the kinetic energy (speed) of the neutrons that are released (there’s thermal neutrons which are slow, epithermal neutrons which are a little faster and fast neutrons which are well…fast). And these different energies tell us about what the neutrons are travelling through, and therefore what the planet has got in it.
For example, hydrogen slows down neutrons down quite a bit (because they’re similar sizes so can transfer energy well), so if we detect a bunch of slow neutrons…hmm 🤔. What could there be? Hydrogen. And that usually means water or ice. That’s one of the main things we want to find (because it’s a sign of potential life), and neutron spectroscopy helps us do that. Basically, nuclear physics helps us alien hunt.
An example of a neutron spectrometer is the High Energy Neutron Detector (HEND) on Mars Odyssey (a spacecraft orbiting Mars).
Gamma ray spectroscopy: The word “spectroscopy” is starting to get on my nerves. Anyway, gamma radiation isn’t just an Earth thing. It’s an everywhere thing. Even Martian elements get angry and excited (literally) and emit radiation. The gamma ray spectrometers detect these gamma rays (you wouldn’t have guessed that, would you?) and figure out what element is having a mini tantrum. Like we said earlier, different isotopes and elements release different energy gamma rays, so each translate to different electrical signals, meaning we can differentiate between them.
An example of gamma spectrometers are the ones on the Mars Odyssey (there’s a whole lot of spectroscopy (😡) happening on that spacecraft).
So that’s nuclear the “s” word. It helps us figure out what element or on other planets and moons and is again, just very very cool.
Radiation knowledge - The radiation levels in space are high. You’ve got cosmic rays and solar particle events (when the sun gets dramatic and bursts out radiation and accelerates particles and stuff). There’s all sorts of radiation in space. And astronauts don’t have the Earth’s magnetic field to deflect particles or the earth’s atmosphere to absorb stuff (this is why Pilots ✈️ are exposed to higher levels of radiation than others - it’s because they’re up high where cosmic radiation is more, you know, there).
Knowledge of radiation and the nucleus’ outbursts help us to shield spacecraft and astronauts so that everyone is safe. See? Nuclear physics is literally saving lives.
Nuclear Propulsion (for the future) - Something that we’re currently working on (by we I mean NASA and other organisations that I have no part in) in nuclear tech in space is nuclear propulsion. And they’re two types: Nuclear Thermal Propulsion (NTP) and Nuclear Electric Propulsion (NEP).
Nuclear Thermal Propulsion: We’ve got a compact nuclear reactor in our spaceship’s engine, and it’s doing its thing - fissioning (we’ll talk about this in a bit). Fission releases lots of energy and heat. In this case, we use that heat to warm up some fuel - liquid hydrogen -until it’s not-so-liquidy anymore. It becomes a super hot gas (I’m talking thousands of degrees celsius). This gas is pushed through a nozzle and thrust is created (rocket goes up).
Nuclear Electrical Propulsion - This is when we’ve got a reactor somewhere on the spacecraft (not engine) and it’s generating heat. This heat is converted into electricity like in any nuclear power plant: heat up a fluid (here helium, sodium or liquid metals), and then this spins turbines which generates power. So we’ve got electricity. But we’ve got to use it to make the rocket, you know, move and stuff.
The electricity powers an electric engine. In this case, an ion thruster. That sounds like a cool weapon name in a action-packed movie. Alright, so, what an ion thruster actually does is it gets a gas (normally xenon because it’s heavy and stable) and uses the electricity to rip electrons away from their atom (maybe it is a weapon) - this creates ions. Then, we’ve got some electromagnetic fields, and we use them to throw the ions out the back of the engine at slow, slow speeds (I’m kidding) of 40,000 m/s. So basically, my running speed. And this stream of zooming ions creates…THRUST!!! Brilliant.
These are still in progress but once out there, they will have some amazing advantages.
Why do we like them? -
Nuclear Thermal Propulsion is way faster than regular, ol’ chemical rockets, and so they can cut trips down e.g. around 7-10 months to Mars goes down to about 4-6 months - this means less radiation exposure for astronauts and you know, less time taken. The design is also simple and the physics is proven - so it’s chill.
Nuclear Electrical Propulsion is really fuel efficient - it uses less fuel over time - which makes it perfect for longer missions to like the other side of the galaxy and stuff like that. NTP is just fast, NEP is actually slow to start with, but as time passes, thrust builds up, and the spacecraft gets faster and faster. To speedy speeds.
So, that’s nuclear physics doing some out-of-this-world stuff (see what I did there 😉). There’s so many more uses in space alone, which shows how useful and versatile the field is.
What is nuclear energy?
My favourite topic. Energy. Nuclear energy. Nuclear physics is a massive part of energy production and our plans for a more sustainable future. Now, nuclear energy is quite a controversial topic. I’m not going to go into too much detail about it now (see section 5), but I’ll give a little overview…
Nuclear power plants that we use today are powered by nuclear fission (I’ve mentioned this briefly) - this is the energy released from splitting a nucleus. However, scientists are working on making something called nuclear fusion more efficient. Nuclear fusion is producing energy from colliding nuclei. Nuclear energy - both types - produce lots of energy from little fuel, but both come with problems of their own. Ok, I’ll save the rest for section 5 - get excited fellow energy enthusiasts (aka nerds like me).
How do nuclear submarines work?
I honestly didn’t know these were a thing until ChatGPT suggested it as a topic to write about. So, let’s learn together!
Ok, nuclear submarines are powered by nuclear reactors. A reactor is where nuclear fission happens. As I said before, a detailed explanation on fission (and it’s hotter sibling, fusion 🤣 - you’ll get that joke later on, but it’s brilliant) can be found in section 5, so we’ll keep this quick and simple. Uranium-235 is hit by neutrons and it decays. Neutrons are released from the decays which causes a chain reaction (splits other atoms and so on). This generates heat and that heat is used to heat water into steam. This steam powers the turbine which turns the propeller shaft (for movement) and spins electric generators (basically powers the lights, computers and other submarine stuff).
So that’s really it.
But what’s so special about nuclear submarines in comparison to regular old diesel submarines? Well, a single load of uranium can last for 10-30 years which means that the submarine people (that’s what they’re called, right?) don’t have to keep going back up to get the sub refuelled and stuff. Also, fission produces a lot of energy continuously meaning the sub is more powerful and faster. Fission sounds perfect! For now…
5. Nuclear Fission and Fusion
Alright, we talked about some of the stuff that nuclear physics allows us to do. But, we need to go into a bit more detail about one thing: nuclear energy. Are you excited? (yes, yes you are)
What is nuclear fission?
It’s getting good folks. Nuclear fission. Let’s talk about it.
Nuclear fission is what our nuclear power plants are based on. So, it’s one of our sources for electricity - and it’s up there near the top in my opinion (🫢 shoot me). Fission is splitting a large, unstable nucleus (generally uranium-235) into 2 smaller daughter nuclei (products such as krypton, barium, iodine etc). It releases a lot of energy, and also free neutrons.
How do we split the nucleus? - A slow-moving neutron is shot at the the nucleus and it becomes uranium-236. Now, this guy, this guy is very unstable and angry. It needs to calm down. How does it do that? You guessed it. It splits.
How does the reaction continue? - The free neutrons released hit other nuclei causing more fission. This is called a chain reaction. Now, measures are taken to control the chain reaction, because if not controlled, there’s kind of an explosion. It turns from a nuclear reactor to a nuclear bomb. I don’t think we want that.
How do we like not explode into a billion pieces? - What a beautifully worded question. So, first of all, fissile (fission) material - like uranium-235 - is kept in rods. Now, when fission occurs, neutrons are released. Surrounding the fuel rods, is a moderator (generally water) which slows down neutrons to ensure that they don’t just zoom by fuel rods. We need it to actually hit one so the reaction continues. But, we don’t want the chain reaction rate to increase uncontrollably. This is where control rods come in (very fitting name in my opinion). They are made from materials such as boron or silver which absorb neutrons to prevent them from causing any more fission reactions. They are placed between fuel rods (obviously). When the chain reaction needs to be slowed down, they are partially inserted, but when it gets a tad more serious (emergency-level if you will), they are fully inserted to stop the reaction. And if the reaction is being too slow, we withdraw the control rods so the reaction can pick up the pace.
How do we control heat? - Fission releases a lot of heat. The energy released is mostly kinetic (moving) energy, which becomes heat. We don’t want it to get too hot and overheat, because again, that doesn’t end well. It can cause meltdowns (radiation can escape into the environment) if not controlled. But don’t worry. We’ve got coolant. It’s a liquid or gas that flows around the core (where the fission happens) and what it does is carry heat far, far away. To a steam generator or directly to turbines (where we turn the nuclear energy into usable electricity) to be exact.
Safety - If I’ve scared you with the meltdown talk and the explosion yap, I do apologise. Do not fear. Nuclear reactors have many safety measures. We talked about coolant and control rods, but there’s so many more. Containment structures, radiation shielding, emergency/backup systems etc. Modern nuclear reactors are carefully engineered and heavily regulated to ensure smooth sailing. And if we compare it to other sources of energy, like coal and oil, nuclear power is safe.
So that’s good old nuclear fission.
What is nuclear fusion?
Meet fission’s sister: fusion. She’s safer. She’s cleaner. She’s super hot (let me explain). She’s…not exactly the easiest to handle.
Fission is the splitting of nuclei. Let’s use our knowledge of fission and the name “fusion” to make an educated guess on what fusion actually is. It’s the fusing of two light nuclei to form a heavier nuclei, which releases energy. Who would’ve thought fusion involved fusing? The most common fusion reaction involves fusing two hydrogen isotopes to form helium and release neutrons. These isotopes are tritium (hydrogen with 2 neutrons in the nucleus) and deuterium (hydrogen with 1 neutron in the nucleus) - good, ol’ regular hydrogen doesn’t have any neutrons just to clarify. Why are these used? Good question. It’s because they have a relatively high probability of undergoing fusion (called a high cross-section), less repulsion due to both only having one proton in their nucleus (called a low coulomb barrier), AND their reaction releases a whole lot of energy. So basically, they’re just some chill, solid dudes. Well, maybe not chill. Fusion isn’t very chill.
Magnetic Confinement Fusion (MCF) - WAIT. Don’t run away because of the scary big words. Don’t worry. I was terrified too at first, but we’re going to understand it together. MCF (I am not writing out that whole thing 10 times) is the most common type of fusion. Ok, so tritium and deuterium gas are heated up. Like quite (a lot) a bit. Up to temperatures of about 100 million degrees celsius. Now, it’s so hot here that being a gas becomes impossible. We need the 4th state of matter (if you didn’t know there was another one, um, surprise!): Plasma.
The temperature is so high that electrons gain enough energy to overcome the attraction to their nucleus. They fly away and basically it’s a crazy hot soup of charged particles. See why I keep calling fusion hot? At these temperatures, the nuclei have a lot of kinetic energy and can collide hard enough so that they overcome the electrostatic repulsion (because they’re both positively charged) and they fuse. This releases energy.
Oh, and neutrons. These neutrons hit a blanket of (usually) lithium. This gets hot and then heats up a coolant (remember that from when talking about fission?). This is normally water. Steam is produced and that steam spin turbines and voila: electricity. When the neutrons hit the lithium, a reaction takes place and tritium is formed (so more fuel, which is great because tritium is less abundant than deuterium). This reaction is not self sustaining though. You need to keep up these temperatures and conditions otherwise it kind of just stops. This is difficult.
Hold on a minute. 100 million degrees is quite hot in my opinion. How are we building stuff that can handle that kind of heat? Here is where the magnetic bit comes in. MCFs use devices called tokamaks. Plasma is a soup of electrically charged particles and magnetic fields affect charged particles. Tokamaks take advantage of this. They’re shaped like donuts (mmm, yummy), or a torus to be more fancy, and use magnetic fields to control the plasma and keep it away from everything so it’s stable and everything doesn’t melt and stuff. They’re are two types of magnetic fields used: toroidal, which is like a guide leading the plasma around in circles and then there’s poloidal, which twists the toroidal field to ensure the plasma doesn’t drift out. Basically, in my kind of terms, the two magnetic field work together as pals to make sure that crazy hot plasma doesn’t freak out and stays in place.
Many MCF reactors are currently being worked on or experimented with such as ITER (International Thermonuclear Experimental Reactor) in France or JET (Joint European Torus) here in the UK. Check these out, they’re seriously cool!
Inertial Confinement Fusion (ICF) - Seriously, these big words are going to kill me. This is another type of fusion. It’s less common than MCF, still just as cool. I mean, it uses bloody lasers. Here, we take a teeny, tiny capsule which contains deuterium and tritium. And then the fun part. Super high powered laser beams all team up and are focused of the tiny pellet.
Hold on a second. Before we carry on, let’s talk about my guy, Newton. Isaac Newton, the guy who like discovered gravity and stuff, came up with a law. Shockingly, it was named Newton’s 3rd law. It states that for every action, there’s an equal and opposite reaction. Let’s have an example, shall we? Let’s take a cute, little rocket (like the ones from the nuclear propulsion section in nuclear space tech). It wants to escape off into space and so hot gases shoot downwards out of its engine (action). It then is pushed upward (equal but opposite reaction).
Ok, fusion and that. So, the lasers cause the outer layer of the pellet to explode outward. This causes an equal but opposite reaction (respect to Newton). The inner fuel is compressed inward. Now, it’s gets hot 🔥. All that pressure and energy pile up in the centre, which leads to high, high, temperatures. And then…fusion. If the perfect conditions are met, the energy from the first reaction triggers a bit more fusion (so it’s self-sustaining, but only very briefly). Anyway, the fusion releases energy and yeah, that’s ICF.
An example of a facility that uses this technology is the NIF (National Ignition Facility) in California.
Ok, so that’s fusion. She’s really quite warm. She’s great. She’s just really difficult to actually sustain.
Why is nuclear fusion hard to achieve?
Magnetic Confinement Fusion - We talked briefly about coulomb barrier - the electrostatic repulsion between protons. To overcome this repulsion, we somehow have to get nuclei close enough so that the strong force does it’s thing and they decide to join up and be besties instead of enemies. How about smashing them together? Sure. That requires them to be moving really quite fast in a small space. How do we give the particles more kinetic (moving) energy? We increase the temperature. The temperatures required for fusion are like 100 million degrees celsius or more. That’s hot. 🔥 And we need super high pressure and density. Basically, we need lots of particles in little space to increase chances of collisions. We have to replicate conditions found at the core of the sun - but hotter. I feel like you can guess that that’s not easy on chill Earth. We’re dealing with crazy, unpredictable plasma here. At insane pressures. We need super stable, strong, and reliable magnetic fields to control all this madness. And don’t forget, we not only need to control the plasma, but also make sure it doesn’t cool down (we need constant heating using electromagnetic waves or high-speed particle firing) or become unstable. Fusion isn’t self-sustaining and it’s difficult. It needs a lot of energy input. So much that even if fusion is achieved, the energy output is often less than the energy input. Not useful for electricity production, it’s crazy high in demand and needed almost everywhere. This is actually what scientists are currently working on, reaching ignition - when fusion output is greater than energy input. But more on that a little later.
ICF - We talked about 2 different types of fusion, MCF and ICF. The first paragraph talks about magnetic fields and stuff. That’s not part of ICF. But with ICF, difficulty remains high. We need the perfect conditions for laser fusion to work - exact timing and symmetry. What does this mean? Well, symmetry in this context is applying energy evenly. When we explained ICF, we talked about the centre of a pellet of fuel getting hot. This hot spot in essential for fusion to take place. So, pressure or energy from the lasers has to be perfectly even and it can’t have any favourite sides of the pellet. And then time comes in. There are 192 lasers involved in laser fusion (🫢 I know). For symmetry and perfect conditions, we need all lasers to compress the pellet at the same time. And I mean the same time. Even a delay of a billionth of a second can mess up the balance. That’s tough. And those 192 high-power lasers - that’s a lot of energy input. Again, we want ignition. But, fusion is hard to sustain so energy output is likely to be less than input.
Fuel - We talked about deuterium and tritium. The cleverly named isotopes of hydrogen (truly though, come on physicists, be a bit more creative - for example, we actually couldn’t think of anything better than strange quark?). Sorry, I had to rant a little. Anyhoo, deuterium is relatively easy to get from water sources so that’s fine. Tritium however, it’s rare. And to get more, we need to make more during fusion (MCF). But, you see, that actually requires fusion to work for us. Not the most ideal situation.
The Lawson Criterion - There’s specific conditions for fusion to be met, as we now know. Enter the Lawson Criterion. For fusion, we need the right temperature, density, and confinement time (how long we can keep the fuel hot, dense and cool to work with - maybe not “cool” per se, but you get the gist). The Lawson Criterion says that each of these factors needs to be at or above a specific value, otherwise fusion = not gonna comply. So, yeah, the Lawson Criterion is the list that must be followed if you want to fuse nuclei (just in case, you never know).
In conclusion, fusion is the picky, high-maintainance sibling. But, we still love her. She’s clean, powerful, and just downright cool. One day, when fusion is figured out and stuff is chill, I truly believe it’s going to change the world. So, let’s keep on working on it. 🤞
Why does fission and fusion release energy?
You can already answer this one. Remember nuclear binding energy, that key concept we talked about earlier? We explained how when fusing nucleons/nuclei, energy is released, due to the mass defect. That’s the explanation for fusion sorted.
We also however, explained nuclear binding energy in terms of the energy required to split nuclei. If you’ve forgotten what I yapped about, it’s section 3!
Hold on. Fission releases energy. But I said that it requires energy to split an nuclei. Both of these are true. I’m not going crazy I promise. It does require energy to split a nucleus. But fission releases a lot of energy.
Why? - Uranium-235 is an unstable mess (in the nicest way possible - we still love you uranium-235). It’s big and heavy so easier to split (we talked about this in section 2). When you split it during fission, as we previously learnt, we get daughter nuclei (products such as kypton and barium). These are smaller, and more tightly huddled together - their binding energies per nucleon is higher.
How? - Some of the original mass was converted into energy. The daughter nuclei are lighter than the original nucleus (mass defect). So, mass lost = higher binding energy. That energy? That’s what’s released. Remember even a little difference in mass = a lot of energy (E=mc^2).
If you are a bit confused, don’t worry - same. If the mass is converted into binding energy, how is any energy released. Let’s use an analogy. You’re building a fort. You put a lot of effort into ensuring the fort is built perfectly. Seriously, a lot of effort. You sweat, you carry stuff about, you go back and forth - you need the perfect fort. That effort is energy being released. You’ve finished with a more stable, strong fort. The effort you used? It’s gone now. It was released during the formation of the fort. Just like how binding energy is released during the formation of the daughter nuclei. But that’s what made the fort so strong. Binding energy is what makes the nuclei more stable and tight but it is released, not stored.
If it’s not explicit enough, here, effort = binding energy.
So yeah, that’s that. Interesting, right?
I’m going to guess that you’re nodding your head enthusiastically right now, with no sarcasm or disagreement in sight.
Lets move on!
Which is better: fission or fusion?
In case you wanted the short answer: fusion. In theory. Hope that helps.
But…our favourite question is coming up…why?
Let’s break it down.
Radioactive waste - Fission is overall quite clean and safe, but there are a few downsides. The by-products produced from fission, like krypton and iodine etc, are radioactive. Despite being more calm than the original nucleus, they are still unstable due to their high neutron-to-proton ratios. Some of them have short half-lives, so they decay pretty fast and so after the initial angry burst of energy, they become safe e.g. Iodine-131 with a half-life of 8 day. Just to clarify - they are super dangerous whilst decaying, but they have short lifespans. Other products have a longer half-lives (much longer) e.g. Technetium-99 with a half-life of around 211,000 years. Which isn’t great. They decay slower, so aren’t as aggressive. BUT, they stay radioactive for a very long time and if not contained properly, they can pollute the environment e.g. groundwater etc. Fusion however produces more calm radioisotopes with less danger and lower half-lives e.g. tritium (half-life of 12 years and emits low-energy beta particles). So that’s a win for fusion. 1-0.
Carbon emissions - Both are carbon neutral. They don’t emit carbon dioxide into the atmosphere, which as you may know is a greenhouse gas. Too much greenhouse gases traps radiation from the sun and the earth starts getting a bit warm and then BOOM!: climate change. So not good. Unlike fossil fuels, fission and fusion are carbon clean. Points for both! 2-1
Accidents - Fission works using a chain reaction. In order to stay safe, we need to control that. We also need to control temperature and radiation leaks. If we don’t, there’s a small chance for accidents like Chernobyl or Fukushima. Of course, this is unlikely due to the heavy safety procedures in place, but the risk is there. Fusion, however, is not powered by a chain reaction. There’s no risk of an uncontrollable domino effect. If the power suddenly shuts down, the plasma cools, the reaction stops, everything calms down. Fusion is safer. 3-1 it is.
Energy production - Fusion produces more energy per kilogram of fuel. Why? Because the mass difference (the mass defect) is larger in fusion than in fission (around 0.1% of the mass is lost in fission compared to about 0.7% of the mass in fusion). That means more mass is converted into energy.* And even a little more mass makes a lot of difference (because of the fact that the speed of light squared is kind of a big number). So, a kilogram of uranium fission fuel can produce around 8.2 x 10^13 Joules of energy. That’s a lot. But a kilogram of fusion fuel (deuterium and tritium), can produce around 3.3 x 10^14 Joules of energy. That’s just over 4 times more energy than fission. 4-1 to fusion (it’s not looking good, is it fission?).
We’ve established fusion is great. It does win. In theory. But it’s not actually used. It’s a dream for the future, it’s a goal we’re working towards. And yeah, fission has downsides - like everything. But, it is one of the most efficient, safe methods for generating electricity. A lot of the time, people focus on the possible negatives instead of the actual positives. And modern reactor designs are much safer than older ones. It has improved so much and it will continue to do so. So yes, I still think fission is the best because for now, it’s doing all the work - it deserves a bit more credit I think. Alright, I’m going to stop before my passionate, angry, argumentative side comes out. 😌
Next section!
*Ok, just a quick little extra. Why? Why is the mass defect greater in fusion? It’s because in fusion, we take two lightly bound nuclei and fuse them into a super tightly bonded nucleus - so more mass is converted into binding energy. It might not seem like it, but it’s a big jump from deuterium and tritium to helium because the helium nucleus is bigger, has an even ratio of protons to neutrons - 2 of each (one neutron is released) and the strong force has more nucleons to work with - so there’s more interactions. All of this makes the nucleus significantly more tightly bound. In fission, we take uranium. Now, it’s binding energy per nucleon isn’t high, but it’s higher than deuterium and tritium - so it’s more tightly bound. This means that when it splits into two daughter nuclei, which aren’t that much more tightly bound, less mass is converted into binding energy. Therefore, fission has a smaller mass defect.
What is the Sun doing that makes it a giant fusion reactor?
The Sun does fusion. It’s the OG fusion reactor. Well, maybe not original. But it started fusing long before we started trying to.
The Sun’s core is about 15 million degrees celsius. So, it’s relatively warm. That, of course, was sarcasm. It’s really freaking hot. Like crazy hot. 🔥 And because it’s so massive, the core is home to incredible pressure - pressure over 200 billion times the Earth’s atmospheric pressure. This creates the perfect setting for fusion. Protons slam together even though they hate each other - they have no choice. Helium is created, and basically it’s an insane soup of particle bumper cars. Or something like that.
What does all this fusion do? Well, we know it releases energy (you remember E=mc^2). Why does that matter though? So what? Without fusion, the Sun wouldn’t even be the Sun and we wouldn’t be here and everybody is dead. Sorry, that took a bit of a dark turn. But yeah, fusion powers the Sun.
The energy produced from fusion is what we receive as the Sun’s heat and light. It’s what gives the Sun the ability to be bright and warm us up so that we’re not just a floating ball of rock and ice. All that energy also creates an outward pressure. See, the Sun is pretty damn massive and so gravity really wants to crush it. This is because gravity’s job is to pull mass towards each other. The Sun’s mass is about 330,000 times greater than the Earth’s. That means its gravitational pull is quite a bit stronger (like, a lot). So, it’s really tempted to collapse in on itself. But, have no fear: fusion is here! Like I said, the fusion creates an outward pressure (called radiation pressure). That pressure is fighting against the gravitational pull that is trying to kill the Sun. 🤺 Unfortunately, this fight is quite boring. Both are just strong enough so that the Sun is stable and doesn’t collapse in on itself (this balance is called hydrostatic equilibrium which sounds a bit too fancy to me). I guess that’s fortunate actually. Cause then we’d all be dead otherwise.
So yeah. The Sun’s fuel is fusion. The Sun works because of fusion. We have life because of fusion. In conclusion, good job fusion. Thanks a bunch! 😄
Fun fact: The energy released from fusion takes thousands of years to escape the sun and reach the Earth. So the energy we receive is actually super old. Like, it’s got a lot of wrinkles. Well, it would do… if it had a face. But it doesn’t. So… I’ll stop now. I won’t go into the why here, because I’ve done enough sidetracking, but search it up - it’s awesome!
Bombs.
Unfortunately, often when people hear the word “nuclear”, their minds immediately jump to weapons and destruction. And who can blame them? Nuclear bombs are crazy powerful, damaging, and sadly, in topics of conversations today. The science behind them however, I think it may be the most interesting part of this whole blog. Let’s talk about them.
Fusion bombs (Hydrogen bombs /Thermonuclear bombs /H-bombs) - Fusion bombs actually also use fission. The first stage is to detonate a fission bomb. Fission bombs release a lot of heat and radiation, which is what we need to get fusion going (fusion only works at insane temperatures remember?). So, this heat and radiation is channeled inside a special casing (called a radiation case/”hohlraum”) towards the fusion fuel. The fuel is quickly compressed like crazy from this, and this is what we call radiation implosion. All this pressure from being squished, and the heat, allow for fusion. But wait. This fusion releases neutrons which hit a uranium outer casing - more fission. Triple threat. All of this is uncontrolled. And…💥. An explosion. More powerful than any regular fission bomb or any bomb ever for that matter. The explosion can have a blast yield (energy release) of 1 megaton (standard) - 50+ megatons (Tsar Bomba test, USSR 1961) of TNT. That’s 3000x as much as the bomb that hit Hiroshima in 1945. And then, the bomb also releases a lot of radioactive particles. The damage is therefore wide-spread. Up to 20km away from the explosion, radiation sickness can occur, up to 10km is where there are serious radiation burns and a high fatality rate, up to 5km is intense heat, radiation and most perish, and up to 1.5km away is instant vaporisation - death. All of this, from tiny nuclei interacting. Isn’t that crazy? And kind of terrifying.
The fuel used for fusion in bombs is generally lithium deuteride. A compound made of lithium and deuterium. When bombarded by neutrons (from the fission bomb reaction), it creates tritium, which then reacts with the deuterium from the original compound. This is better than storing regular tritium because tritium is radioactive and unstable. Also, it keeps the bomb more tight, compact, light and powerful.
Fission bombs (Atomic bombs/A-bombs) - There are two types of fission bombs. The gun-type design (nicknamed the Little Boy for some bizarre reason) and the implosion design (nicknamed the Fat Man 🤨). When I say be more creative with physics names, I don’t mean this.
Gun-type (I refuse to call the bombs their other names): This bomb uses uranium-235 as fuel (the other uses plutonium). To start, one piece of uranium is fired into another using a cannon mechanism and when they collide, they form something called a supercritical mass. That means that enough fuel is packed closely enough to start a chain reaction. We heard about chain reactions in fission energy production. The difference is, in a bomb, as I mentioned previously, it’s not controlled. What does that lead to? A massive explosion. In this case, a blast yield of around 15 kilotons of TNT (this is the number from the bomb that hit Hiroshima). That’s deadly. And that’s not all. The explosion causes radioactive particles to be blasted into the surroundings. They fall to the ground and severely contaminate the air, water, food, everything in a 1-2km radius of the explosion.
Implosion type: This one uses plutonium-239 as fuel. I talked about uranium as fissile material, but plutonium also works. It’s not really used in energy production because it’s not found in nature (it’s produced during fission reactions that use uranium-238 as the starting nuclei) and it’s more dangerous, but still - it’s unstable and has a super heavy nucleus so it works. So, the bombs work using regular explosives first. The explosives are around a plutonium core and once they’ve gone off, the plutonium is compressed inward to create a supercritical mass. Feeling familiar? This triggers a chain reaction and then? About a millionth of a second later (a microsecond): BOOM! This time a blast yield of around 21 kilotons of TNT (numbers from the Nagasaki bomb).
Why is it more powerful than the uranium bomb? Because the implosion design means the fuel is compressed better, leading to a more efficient chain reaction. Plutonium is faster at releasing neutrons spontaneously and that also adds speed to the reaction. And because the implosion happens so fast, the plutonium reaches supercritical mass much faster so more fuel is actually used compared to the uranium bomb. All of these lead to a more violent explosion.
Why don’t we use plutonium for the other bomb then, instead of uranium, if it’s more powerful? Because we can’t. Plutonium is way more spontaneous and unstable in terms of neutron release, and so the chain reaction may start too soon. It’s too risky.
So these bombs, they can cause a lot of damage and loss. And they did.
Hiroshima and Nagasaki: The gun-type design was used in Hiroshima, Japan, August 6th 1945. 70,000 - 80,000 people died instantly. Tens of thousands later passed from burns and radiation. In total, the death toll was over 140,000. Cancer, radiation and trauma haunted the survivors.
The implosion design was used in Nagasaki, Japan, August 9th 1945. 40,000 died instantly. The total death toll rose to 70,000 - 80,000 by the end of 1945. Both bombs were dropped by the US.
Let’s think about this for a minute. Hundreds of thousands of innocent people dead. Because science was used to destroy, instead of grow. Imagine if instead of investing time, money and brain power on weapons and destruction, we all came together to solve the world’s problems with science, tech, and more. I know, it’s unrealistic, but just think about it for a second. Where do you think we’d be? What would the world look like? Science is incredibly powerful and it itself, is good. That’s what it should be used for. For good.
6. Disaster, Controversies and Safety (yes, more)
What happened in Chernobyl and Fukushima?
Two major nuclear disasters. Two different causes. Let’s get into it.
Chernobyl - It’s the 26th April 1986. We’re in Chernobyl (then USSR, now Ukraine for you history enthusiasts). A safety test was being run at the Chernobyl power plant (pretty ironic, no?). They were testing to see if the cooling systems still ran if there was a power outage. Fair. So, what would happen after a power outage? Well, the control rods would automatically be fully inserted and they would stop the reaction from continuing. This is called the SCRAM system. Now, as we learned previously, the fuel rods absorb the neutrons, so that the chain reaction takes a chill pill. The thing is the reaction doesn’t stop completely. The fuel is still super hot and the radioactive waste products continue to decay, releasing even more energy and therefore heat. Immediately after the fuel rods do their thing, decay heat (the radioactive stuff being radioactive and releasing energy and that) is about 6-7 percent. After a minute, it’s about 1 percent. The thing is, in nuclear fission energy terms, 1 percent is still a lot of energy. And so we still need the cooling systems. Before the backup diesel generators start their work, we have a good 40-60 seconds to wait. Too long. They had to test whether they could make the cooling systems work for that little interval. So, that’s what they set out to do.
To test this, they lowered the power (to simulate what would actually happen). The problem? They dropped the levels to less than 1 percent of full power. Too low. As it normally does in a fission reaction, Xenon - 135 is formed. Now, Xenon - 135 is a neutron sponge, it absorbs them like crazy, and then it decays. But because the power is so low, there aren’t enough neutrons from reactions to be absorbed by the Xenon. It therefore, doesn’t decay as fast and builds up. The few neutrons left get eaten and the reactor is struggling, the chain reaction is not getting enough fuel. This is called Xenon poisoning.
What do they do now? They decide to fully pull out the control rods. Big mistake. Xenon starts clearing up after getting hit by the little remaining neutrons. Once that happens, the neutrons aren’t getting absorbed as much. The reaction speeds up. It’s get hotter. Water starts boiling.
Now, first we need to talk about the kind of reactor we’re dealing with here. It’s a RBMK Soviet reactor - Reaktor Bolshoy Moshchnosti Kanalniy or high-power channel reactor. They are very old and very flawed. Most reactors in the West today are PWRs (Pressurised Water Reactors) or BWRs (Boiling Water Reactors). The key difference between these are the moderators. We talked about moderators. You know, the substances used to ensure the neutrons travel at the right speed, so the reaction actually happens. The moderator in PWRs and BWRs is water. So, when water boils and turns into steam, the reaction slows down because less water means less moderation meaning less neutrons travelling at the right speed. This is known as a negative void coefficient. RBMKs use graphite as moderators. So, when water boils, the reaction speeds up. Water is also a neutron absorber. Less water means less absorption. And we still have graphite to moderate the neutrons, so the reaction keeps going. In fact, the reaction speeds up. Fast. (This is called positive void coefficient).
Right, the water is boiling. We explained that this led to more reactions. Which then leads to more boiling. Remember, there aren’t control rods to calm this down.
The reaction sped up to fast. Fuel rods overheated. BOOM. The reactor exploded. Twice. The 1000-ton lid got blown off of the reactor. Catastrophe. Radioactive material everywhere. And there was no containment structure like in modern reactors. Graphite from the reactor caught fire and radioactive atoms were spread across Europe.
30 workers and firefighters died just after the explosion, 1000s got cancer, the environment was heavily damaged, and Chernobyl remains uninhabitable today.
It was a shocking, world-shifting disaster. This made engineers and physicists aware of potential outcomes, and design flaws. Today, safety is taken incredibly seriously, and designs have improved massively.
Decades after Chernobyl however, nature, not human error triggered another nuclear meltdown. Let’s move forward to March 11th 2011, in Fukushima, Japan.
Fukushima - It’s 2:46pm. A magnitude 9.0-9.1 earthquake strikes the coast of Japan (a massive, devastating earthquake). The nuclear reactor immediately shut down (the control rods were automatically fully inserted as they should have been). Decay heat still remains, but we’ve got diesel backup generators powering the cooldown systems, so all is going ok so far.
A tsunami with waves of a maximum 15-metres hits the site. The entire nuclear power plant site is flooded, including the generators. They are destroyed. The cooling pumps lost power, and after a few hours, the batteries completely ran out. There was no cooling.
The fuel rods melted. These fuel rods are made of uranium fuel (obviously), and then an outer casing of zirconium. The zirconium reacts with the steam (from boiling water) around it, and a lot of heat is produced. As well as a whole lot of hydrogen gas. Some hydrogen escapes outside of the reactor vessel (where the coolant and core are in a reactor) and unfortunately the outer containment buildings of Fukushima don’t let it out fast enough. It therefore keeps on building up. Why is that bad? Because hydrogen is crazy flammable. If it’s concentration in air reaches anywhere from 4-75 percent, then it doesn’t take a lot for a chemical explosion. We don’t know exactly what caused the explosions. It only required something little - like static electricity (the build-up of charge on a surface) or a hot surface from the damage. But multiple explosions took place: Reactor 1 on March 12th, Reactor 3 on March 14th, Reactor 4 also exploded, despite being inactive, due to a hydrogen leak. All of these explosions took place in the outer building. Reactor 2 didn’t explode, but it did leak radioactive particles.
What was the damage? The natural disasters themselves caused thousands of deaths, however the meltdown did not have any direct deaths. Over 150,000 people were forced to be evacuated due to contamination leading to mental health struggles and financial problems. After what happened, Japan shut down all nuclear reactors. Since then, nuclear power has been reintroduced, however many are still against it.
Parts of Fukushima closest to the reactor do remain uninhabitable.
We obviously can see where nuclear energy has its controversies. Why is it still used? Because those 2 accidents taught us a lot, and we have improved our technology and safety measures since. For example, after Fukushima, new reactors include cooling systems that don’t rely on electricity and pumps, and laws on safety have become way stricter. Nuclear power is now seen as safe. Disasters are very unlikely. And they are a substitute for fossil fuels - a much more deadly source of electricity. Air pollution from coal, oil and gas kills an estimated 7 million people a year. Per terawatt-hour (TWh) - a unit to measure electricity - coal causes around 24.6 deaths, oil is around 18.4 deaths and natural gas is about 2.8 deaths. Nuclear? 0.03 deaths. Even wind is higher than this with 0.04 deaths.
In conclusion, it’s more than fair to be skeptical about nuclear power considering the damage it’s done and the accidents that have happened, which led to trauma and environmental pollution. However, if we look at the bigger picture, and we see the improvements that have been made, one can argue that nuclear power is a reasonable alternative for fossil fuels. It’s safer, more powerful, and overall cleaner.
Shall we look into this debate a bit more?
What are the arguments for and against using fission energy?
We know fission and how it works. We also know it’s controversial. Let’s deep dive into the for and against sides, so that maybe, you can pick a side of your own (I feel as though I’ve made mine pretty clear).
Against:
Radioactive waste - As I said previously, nuclear fission products are radioactive, and some remain that way for quite a while. This, obviously, is not ideal. This can lead to pollution of the environment, and potential danger of radiation contact. However, scientists do have ways of dealing with radioactive waste and the risks associated with it (see next section).
Nuclear accidents - The worse case scenarios, for nuclear power plants, are very bad. Like really not good. You’ve heard about Chernobyl and Fukushima. From them, we know what could go really wrong. These risks can honestly be quite scary. It’s totally understandable why some might see this as a reason to be against nuclear fission. However (I’m trying to be balanced, I promise), we’ve talked about safety measures that are in place to prevent these accidents. Because of these, the risk of disaster is very low. Nuclear power reactors today are seen as safe and reliable.
High initial cost - Building nuclear fission reactors takes complex engineering, special materials, and around 8-15 years (not ideal for countries that need energy, like right now). This is expensive. Compared to other energy sources, fission is one of the highest in terms of upfront cost. We generally like cheaper stuff, so this isn’t the best. However (you saw that coming didn’t you?), after becoming operational, the nuclear plant works without needing a ton of money being poured into it. It lasts for a super long time and produces a lot of power. Fossil fuels are destroying our planet, so I think it’s about time we started investing in cleaner, more fierce sources of electricity.
For:
I realise I gave arguments for in my against section (I couldn’t help myself, ok?), but here’s a better, more comprehensive list of benefits of nuclear fission.
Gives us a super-duper amount of energy - You remember our pal E=mc^2 and what that has to do with energy released in fission? Basically, a whole lot of energy can be produced from a reaction. Even though uranium supply is finite (it is relatively abundant now though), we can use a small amount to power whole cities. This makes it longer lasting, and just really cool.
Low greenhouse gas (bad stuff) emissions - The world is getting sick of fossil fuels (coal, oil, gas). Why? The biggest reason is the amount of greenhouse gases emitted from them. These gases e.g. carbon dioxide contribute to climate change which = not good. Once nuclear plants start running, they emit virtually no carbon dioxide. They are what we call carbon-neutral. We love that. A lot.
Reliable - Solar panels aren’t very useful when it’s not sunny. Wind power isn’t very useful in a place with no wind. For many sources of energy that are renewable (from natural sources, can be replenished), reliability is a weaker point (hydropower is great I will admit). Fission is non-renewable - it will eventually run out (after MANY, MANY years), but it is reliable. You don’t need a specific setting or environment or weather condition or whatever for it to do it’s thing. It’s not picky. It can run 24/7. Who wouldn’t love that?
Space-efficient - Solar and wind farms require more land for the same energy output compared to fission. (Also, I just want to clarify, I think wind and solar power are great, but I am focussed on making fission look fabulous, so forgive me for insulting the other two a bit more). What this means is solar panels and wind turbines take up space. In order to get the same amount of power from them that we get from a nuclear plant, we’d have a take up more space than we would with the plant. I don’t know about you, but I like space. And we have more if we use fission. Just saying.
So there we go, a relatively(ish) balanced argument debating the positives and negatives of fission - the controversial source of electricity. Hopefully, that has helped you cultivate your own view on this subject, or maybe it’s helped you to understand the opposite view a little more.
We’ve talked about the benefits and drawbacks, but what does this actually mean? What can fission do for us? Can nuclear energy solve the climate crisis?
The answer is no. Not on its own. Climate change is a big thing, so there isn’t one source of energy that’s going to save the planet. We need multiple clean energy sources to work together to chill the Earth out (literally). All have their benefits and drawbacks. I do, however, believe that nuclear energy is a good option to invest in. It can have a significant impact (in the best way) on our environment. It outperforms many of the more favoured, less controversial options in reliability, energy density, space, and more. And it’s carbon neutral. It’s clearly (to me anyway) a strong player in the game of climate change combat. So, let’s think about building more nuclear power plants. And let’s honestly assess the arguments for and against, with a little more open-mindedness. Because come on, nuclear energy deserves a bit more love.
Ok, I’m done with my motivational speech now, next section!
How do scientists deal with nuclear waste?
Fabulous question. We need to know how we deal with the most controversial part of anything nuclear: the radioactive waste. Nuclear waste is split into 3 main categories. These are low-level waste (LLW), intermediate-level waste (ILW) and shockingly, high-level waste (HLW) - you didn’t see that one coming, did you?
Low-level waste - Examples of LLW include tools or gloves used in medicine (radio). This waste is the chill kind. Well, relatively speaking. One not often found in electricity production, but medical or factory settings. Stuff that falls into this category is the least dangerous - less radioactive, less harmful, and less angry. All we do here is seal the waste in a container (to stop any sort of radiation leak), and then, they are buried. Not in any regular ol’ back garden. In a specially designed near-surface landfill. Coolio. Next one.
Intermediate-level waste - For this one, we kind of just do a more serious version of the last one, because the stuff here is more radioactive e.g. reactor parts and stuff. We encase the waste. This time in a super strong, shielding and safe material, like concrete. Then, near-surface burying isn’t quite good enough. ILW is stored either in a secure storage facility or deeep underground until we find a more permanent home for it (more on that in a sec). So yeah, that’s it. Encase, store + shield.
High-level waste - This is the highest level of waste so I’m sure you can guess that this one is the most serious - and therefore, needs the most protection. All this stuff is the incredibly radioactive stuff - that stays radioactive for a looong time. An example of HLW would be used fuel rods. Right, the fuel rods are done with their jobs and ready to retire. Where to first?
A pool party. Used fuel rods are hot, like very, and radioactive, like very. They’re put in deep water pools where they can cool down and chill after all that hard work. They stay here for several years (don’t worry, fuel rods can breathe underwater). Next, they are placed in dry casks. What are they again? Dry casks are massive container made of steel and concrete (materials used to shield - protect from radiation leakage). Now, remember that permanent home we were talking about earlier? The retirement home paradise, if you will. The plan is deep geological repositories (DGRs). These are places hundreds and hundreds of metres underground, where stable stuff lives, like granite and clay. Scientists are working on these to store nuclear waste, so that we can leave it, undisturbed and stable. Just chilling. The one that is furthest along and that is nearly completed as of now (June 2025) is Onkalo, in Finland. It’s meant to have a depth of around 430 metres and is getting ready to store HLW for thousands of years. Pretty cool, I think. Other countries are also currently working on this, like Sweden, France and Canada.
So yeah, that’s the storage plans and stuff. Safe, not too disruptive to the environment, and extra points for being impressive. Maybe this has changed you’re mind about nuclear stuff, or maybe it’s the same. Either way, it was fun learning!
Fun fact: “Onkalo” actually means “hiding place” in Finnish. I’ve got my nuclear nerd grin on now.