Lesson Notes By Weeks and Term v4 - SHS 3
NUCLEAR PHYSICS
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NUCLEAR PHYSICS
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Subject: Physics
Class: SHS 3
Term: 2nd Term
Week: 20
Grade code: 3.4.2.LI.2
Strand code: 4
Sub-strand code: 2
Content standard code: 3.4.2.CS.1
Indicator code: 3.4.2.LI.2
Theme: ATOMIC AND NUCLEAR PHYSICS
Subtheme: NUCLEAR PHYSICS
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This lesson explores how the immense power locked within the atom's nucleus can be harnessed to generate electricity. In a country like Ghana, where a stable and affordable electricity supply is crucial for homes, schools, and industrial growth, understanding alternative energy sources is vital. We have all experienced "dumsor," and nuclear power is one of the long-term solutions being actively considered by the Government of Ghana through the Nuclear Power Ghana (NPG) programme. This lesson will demystify the process, explaining the science behind a nuclear reactor and connecting it to our national development goals.
This section breaks down the complex process of nuclear power generation into understandable parts. A. The Core Principle: Nuclear Fission
At the heart of a nuclear reactor is a process called nuclear fission. Definition: Nuclear fission is the splitting of a large, unstable atomic nucleus (like Uranium-235) into two or more smaller nuclei, releasing a huge amount of energy and several neutrons. The Key Player: Uranium-235 (U-235) Most nuclear reactors use Uranium-235 as fuel. When a slow-moving neutron hits a U-235 nucleus, the nucleus absorbs it, becomes highly unstable (U-236), and immediately splits. The Fission Reaction: A typical fission reaction can be represented as: `¹₀n + ²³⁵₉₂U → ²³⁶₉₂U (unstable) → ¹⁴¹₅₆Ba + ⁹²₃₆Kr + 3(¹₀n) + Energy` `¹₀n`: A neutron. `²³⁵₉₂U`: A Uranium-235 nucleus. `¹⁴¹₅₆Ba` and `⁹²₃₆Kr`: These are the smaller nuclei, called "fission fragments" or "daughter nuclei" (Barium and Krypton in this example). `3(¹₀n)`: Three new neutrons are released. Energy: This is the most important product for power generation. The energy released comes from the conversion of a small amount of mass into energy, according to Einstein's famous equation, E = mc². The energy is primarily in the form of kinetic energy of the fission fragments, which manifests as heat. B. The Engine: The Controlled Chain Reaction
The three neutrons released in the fission reaction can go on to strike other U-235 nuclei, causing them to split and release even more neutrons and energy. This process is called a chain reaction. Uncontrolled Chain Reaction: If every neutron released causes another fission, the reaction rate grows exponentially. This is the principle behind an atomic bomb – a massive, instantaneous release of energy. Controlled Chain Reaction: In a nuclear reactor, we need a steady, controlled release of energy. This is achieved by ensuring that, on average, only one of the neutrons from each fission event goes on to cause another fission. The other neutrons are either absorbed or escape the reactor core. This creates a stable, self-sustaining reaction that produces heat at a constant rate. C. The Machine: Parts of a Nuclear Reactor
Think of a nuclear reactor as a very sophisticated and powerful kettle. Its job is to generate a massive amount of heat to boil water. It has several key components working together to achieve this safely.