1. Nuclear Reactions Chemistry Mrs. Coyle

2. Part I Fission and Fusion

3. Transmutations When a nucleus of an element is transformed to a nucleus of another element.

4. Transmutations Can occur through: –Decay (Spontaneously) –Nuclear Reactions (Fusion and Fission)

5. Nuclear Reactions Fission Fusion

6. Nuclear Fission Enrico Fermi (USA) 1930’s Lise Meitner, Strassman, Hahn (Germany) Bombarding neutrons at 235 U or 239 Pu causes fission (splitting) of the nucleus producing new neutrons that then cause more fission in a chain reaction. Huge amounts of energy (mostly kinetic energy of fragments) is released

7. Nuclear Fission n + 235 U  236 U  X+Y +n + energy Chain Reaction Neutron bombardment

8. Nuclear Fission 235 U is a rather rare isotope(0.7%) of the more abundant 238 U which does not undergo fission. Nuclear Bomb Nuclear Power Plants

9. Nuclear Fusion Sun’s energy comes from fusing of hydrogen to form helium Product has higher mass number than reactant

10. H + H  He +n + energy

11. Part II Nuclear Energy

12. Mass – Energy Equivalence Special Relativity

13. Nuclear Energy used to make Electricity 16% of the world's electricity is produced from nuclear energy. In the US 20% of electricity is made by about 130 nuclear reactor sites.

14. Nuclear Reactor at Indian Point, NY

15. Main Parts of a Nuclear Reactor Fuel Rods Neutron Moderator Control rods Coolant Containment

16. Fuel Rods Pellets of uranium oxide arranged in tubes in the reactor core. (Plutonium is also sometimes used as fuel). About 260 fuel rods form an assembly.

17. Neutron Moderator Slows down the neutrons released from fission so that they are captured by the fuel to continue the chain reaction. Water or graphite.

18. Control Rods Neutron-absorbing material such as cadmium, hafnium or boron, and are inserted or withdrawn from the core to control the rate of reaction, or to halt it.

19. Coolant A liquid or gas circulating through the core so as to transfer the heat from it.

20. Steam Generator The heat from the reactor is used to make steam to run the turbine to generate electricity.

21. Containment A one meter thick concrete and steel structure around the reactor core. Protects the core. Protects the environment from radiation in case of malfunction.

22. Refueling Every 1-2 years fuel rods are replaced. Spent fuel rods are still radioactive (nuclear waste).

23. Nuclear Reactors

24. Part III Detecting radiation

25. The Geiger Counter Radiation detector Hans Geiger

27. Operation of Geiger Counter The radiation ionizes a gas (argon) and frees electrons. The electrons are attracted to the positive electrode, that ionize gas again etc, producing a current pulse. This is amplified and heard as a sound.

28. Units of Radiation measured in rads (radiation absorbed dose), a unit of absorbed energy 1 rad = 0.01 joule of radiant energy absorbed/kilogram of tissue 1 rem (roentgen equivalent man) is the radiation dosage based on potential damage

32. Cosmic Rays Cosmic rays are of two types: high-energy particles. high-frequency electromagnetic radiation (gamma rays). They affect us indirectly by transforming nitrogen atoms in the air to radioactive carbon-14, which ends up in plants we consume.