Nuclear reactions power our world in ways you might not... Show more
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
513
•
30 Nov 2025
•
Understanding Nuclear Fission and Fusion
Megleg
@megleg2007
Nuclear Fusion - The Sun's Secret
Ever wondered how the sun produces enough energy to power life on Earth? Nuclear fusion is the answer - it's when two small atomic nuclei smash together to create a larger nucleus, releasing massive amounts of energy in the process.
The sun runs on what's called the proton-proton cycle. Two protons fuse to make deuterium (with one proton changing into a neutron), then this deuterium fuses with another proton to create Helium-3. Finally, two Helium-3 nuclei join to form Helium-4 and release two protons that start the whole cycle again. This happens about 9 × 10³⁸ times per second in our sun!
Here's the brilliant part: fusion only needs hydrogen as fuel (the most abundant element in the universe) and produces helium - a completely harmless inert gas. The energy released is enormous, much more than fission. The catch? We need temperatures of millions of degrees to make it happen, which is why fusion power remains experimental rather than practical for now.
💡 Quick Fact: If we could master fusion, we'd have virtually unlimited clean energy using just hydrogen from seawater!
Nuclear Fission - Splitting Atoms for Power
Nuclear fission is the complete opposite of fusion - instead of joining nuclei together, we're splitting large, unstable nuclei apart. This is what happens inside nuclear power stations right now to generate electricity across the UK and worldwide.
Nuclear reactors use enriched uranium as fuel. Natural uranium is 99% U-238 (which can't undergo fission), so it's processed to contain 2-3% U-235 - the fissionable isotope that does all the work. When a slow neutron hits a U-235 nucleus, it splits into two smaller nuclei plus three fast neutrons, releasing loads of heat energy and dangerous gamma rays.
Those three neutrons can then hit other U-235 nuclei, causing them to split and release more neutrons. This creates a chain reaction that keeps the process going. Control rods can be lowered into the reactor to absorb neutrons and slow down or stop the reaction when needed.
The heat from fission turns water into steam, which spins turbines connected to generators - that's how nuclear fission becomes the electricity powering your home. It's the same basic principle as coal or gas power stations, just with a nuclear heat source instead.
⚡ Remember: Fission = splitting large nuclei, Fusion = joining small nuclei. Both release energy, but fusion releases much more!
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.9/5
App Store
4.8/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Understanding Nuclear Fission and Fusion
Megleg
@megleg2007
Nuclear reactions power our world in ways you might not expect - from the sun keeping us warm to nuclear power stations generating electricity. Understanding nuclear fission and fusion isn't just about passing your physics exam; these processes literally fuel... Show more
Nuclear Fusion - The Sun's Secret
Ever wondered how the sun produces enough energy to power life on Earth? Nuclear fusion is the answer - it's when two small atomic nuclei smash together to create a larger nucleus, releasing massive amounts of energy in the process.
The sun runs on what's called the proton-proton cycle. Two protons fuse to make deuterium (with one proton changing into a neutron), then this deuterium fuses with another proton to create Helium-3. Finally, two Helium-3 nuclei join to form Helium-4 and release two protons that start the whole cycle again. This happens about 9 × 10³⁸ times per second in our sun!
Here's the brilliant part: fusion only needs hydrogen as fuel (the most abundant element in the universe) and produces helium - a completely harmless inert gas. The energy released is enormous, much more than fission. The catch? We need temperatures of millions of degrees to make it happen, which is why fusion power remains experimental rather than practical for now.
💡 Quick Fact: If we could master fusion, we'd have virtually unlimited clean energy using just hydrogen from seawater!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Nuclear Fission - Splitting Atoms for Power
Nuclear fission is the complete opposite of fusion - instead of joining nuclei together, we're splitting large, unstable nuclei apart. This is what happens inside nuclear power stations right now to generate electricity across the UK and worldwide.
Nuclear reactors use enriched uranium as fuel. Natural uranium is 99% U-238 (which can't undergo fission), so it's processed to contain 2-3% U-235 - the fissionable isotope that does all the work. When a slow neutron hits a U-235 nucleus, it splits into two smaller nuclei plus three fast neutrons, releasing loads of heat energy and dangerous gamma rays.
Those three neutrons can then hit other U-235 nuclei, causing them to split and release more neutrons. This creates a chain reaction that keeps the process going. Control rods can be lowered into the reactor to absorb neutrons and slow down or stop the reaction when needed.
The heat from fission turns water into steam, which spins turbines connected to generators - that's how nuclear fission becomes the electricity powering your home. It's the same basic principle as coal or gas power stations, just with a nuclear heat source instead.
⚡ Remember: Fission = splitting large nuclei, Fusion = joining small nuclei. Both release energy, but fusion releases much more!
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
9
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Mock Exam
Quiz
Flashcards
Essay
Similar content
Properties of Matter Overview
Explore the essential concepts of matter, including specific heat capacity, temperature, and density. This summary covers the behavior of solids, liquids, and gases, their phase changes, and the relationship between temperature and pressure. Ideal for students seeking a comprehensive understanding of physical properties in thermodynamics.
Physics11
Nuclear Fission & Fusion Insights
Explore the key concepts of nuclear fission and fusion, including their advantages, disadvantages, and the processes involved in energy production. This summary covers critical aspects such as chain reactions, safety concerns, and environmental impacts, making it essential for understanding nuclear power dynamics.
PhysicsS4
Free Energy
Gibbs Free Energy-Definition, Explanation, Formulas, and Examples
AP Physics 1Fluid
Classification and Properties of fluid
PhysicsEnergy Transfer Mechanisms
Explore the key concepts of energy transfer by heating, including black body radiation, thermal conductivity, and insulation techniques. This summary covers essential terms and principles related to conduction, infrared radiation, and effective heating strategies for buildings. Ideal for students studying thermal energy transfers.
Physics11
FLUID MECHANICS
This includes the Manning's Equation as well as the different types of flow. It also have sample problems
PhysicsCan't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.9/5
App Store
4.8/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user