Nuclear Fission and Fusion
Splitting heavy nuclei or joining light ones releases energy.
About this topic
Fission splits a heavy nucleus such as uranium-235 after neutron capture into smaller nuclei, releasing neutrons and about 200 MeV, which can trigger a chain reaction. Fusion combines light nuclei, like hydrogen isotopes into helium, releasing even more energy per kilogram.
Both release energy because the products have higher binding energy per nucleon, with the peak at iron. In a reactor, control rods absorb neutrons to keep the chain reaction steady and a moderator slows neutrons so they cause further fission. One kilogram of uranium releases about as much energy as several thousand tonnes of coal.
Fission powers reactors and bombs; fusion powers the Sun and requires temperatures of millions of degrees to overcome electric repulsion, so controlled fusion on Earth remains a research goal in devices such as tokamaks.
Fission waste stays radioactive for a long time, while fusion makes much less long-lived waste. A reactor cannot explode like a bomb, because the fuel is not concentrated enough, though it must be cooled.
Key ideas
- Fission powers reactors
- Fusion powers the Sun
- E = mc² accounts for the energy
Quick check
Use cases: where Nuclear Fission and Fusion helps
- Homework: review the key idea behind Nuclear Fission and Fusion before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Nuclear Fission and Fusion without notes.
- Visual learning: play with the interactive lab to see how Nuclear Fission and Fusion changes when you adjust its inputs.
- Teaching a friend: explain Nuclear Fission and Fusion in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Nuclear Fission and Fusion?
Splitting heavy nuclei or joining light ones releases energy.
What will I learn in Nuclear Fission and Fusion?
Fission powers reactors. Fusion powers the Sun. E = mc² accounts for the energy.
Is Nuclear Fission and Fusion part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Nuclear Fission and Fusion lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Nuclear Fission and Fusion?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.