1. NIS – PHYSICAL SCIENCE Lecture 68 – Lecture 69 Nuclear Energy Ozgur Unal 1

2. Nuclear Reactions 2  Some elements can undergo nuclear reactions, which results in different elements.  Nuclear Fission and Nuclear Fusion Nuclear Fission:  In nuclear fission reactions, the nucleus of a heavy element splits into smaller nuclei, releasing energy.  Example: U-235 Nuclear Fusion:  In nuclear fusion reactions, the nuclei of small elements fuse to form a heavier nucleus.  Example: 4H  He + Energy

3. Nuclear Reactions 3  The amount of energy released can be calculated by Einstein’s famous formula: E = m*c 2  Calculate the amount of energy released by converting 1 kg of U-235 into energy.  The energy released in nuclear reactions is in the form of light.  This energy can be converted into thermal energy to generate electricity.

4. Nuclear Power Plants 4  A nuclear reactor uses the energy from controlled nuclear reactions (nuclear fission) to generate electricity.  Why not nuclear fusion?  Nuclear reactors use U-235 as nuclear fuel.  The reactor core contains uranium dioxide fuel in the form of tiny pellets placed in rods  fuel rod bundle  Check out Figure 12 and Figure 13!!  Why are there control rods in the reactor core?

5. Nuclear Power Plants 5

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7. 7  What are the advantages of using nuclear energy compared to fossil fuels?  Although nuclear power plants do not pollute the environment as much as the fossil fuels, there are some risks of using nuclear energy:  Environmental damage due to hot water  The release of radioactivity (Chernobyl)  The disposal of nuclear waste  Nuclear waste is any radioactive by-product that results when radioactive materials are used.  Nuclear wastes are classified as low-level waste and high-level waste.