This definitions covers Key Definitions within Nuclear Fission & Fusion for GCSE Physics. Revise Nuclear Fission & Fusion in Atomic Structure for GCSE Physics with 13 exam-style questions and 25 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 12 of 18 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
📖 Key Definitions
Nuclear fission: The splitting of a large, unstable nucleus (such as uranium-235) into two smaller nuclei, releasing energy and 2–3 neutrons.
Nuclear fusion: The joining of two small, light nuclei to form a larger nucleus, releasing energy. This process powers stars.
Chain reaction: A self-sustaining sequence of fission reactions, where neutrons from each fission trigger further fissions.
Moderator: A material (graphite or water) that slows neutrons down so they can trigger further fission in a nuclear reactor.
Control rods: Rods of boron or cadmium inserted into a reactor to absorb neutrons and control the rate of the chain reaction.
Practice questions for Nuclear Fission & Fusion
What is nuclear fission?
Explain what is meant by a chain reaction in nuclear fission.