Nuclear Energy: Fission vs. Fusion

1. FISSION vs. FUSION

2. Fission The splitting of a nucleus into smaller fragments when bombarded with neutrons. • One large nucleus of a particular isotope breaks into two smaller nuclei of about equal size

3. 91 36 FISSION Kr 236 92 U 235 92 U neutrons 142 56 Ba neutron

4. Fission • Enormous energy – 1 kg of uranium-235 releases an amount of energy equal to that generated in the explosion of 20,000 tons of dynamite • If uncontrolled chain reaction, the total energy release is nearly instantaneous – entire reaction takes only a fraction of a second

5. Fission • Atomic bombs are devices that start uncontrolled nuclear chain reactions • In controlled settings, like nuclear power plants, the energy is released more slowly – mostly in the form of heat which is absorbed into steam which turns turbines

6. Fission • Access to materials used in fission reactions is somewhat limited • Creates radioactive material (a.k.a. – nuclear waste)

7. 2 1 3 1 H H Fusion proton neutron deuteron ENERGY triton

8. Fusion The nuclei combine to produce a nucleus of greater mass • The sun uses nuclear fusion of hydrogen atoms into helium atoms • Gives off enormous heat and light (and other forms of radiation) • Actually more energy than a fission reaction

9. Fusion • Although scientists have been working on controlled fusion reactions, success has not been achieved to any great extent because the temperature required to start a fusion reaction has to be in excess of 40,000,000°C!

10. Fusion • At these temperatures, matter exists as a plasma (high-energy sate in which ions exist in a gas like form) – to contain plasma that has extreme temperatures, is not possible at this time because no known structural material can withstand the hot, corrosive plasma

11. Fusion • Access to materials for fusion is plentiful • Creates less radioactive material than fission – but creates some (nuclear waste)