Physical Science Lecture 106

1. Physical ScienceLecture 106 Instructor: John H. Hamilton

2. Lecture Review • Radioactivity • Radiation • Beta • Alpha • Gamma • neutron • Radiation dose

3. Radioactivity • Some elements are unstable. They are unable to maintain their nucleus.And tend to turn into something stable • In the process of turning stable they go through what is called radioactive decay. • These unstable isotopes are called radioactive • In the process of decay they can emit nuclear particles and/or high energy EM radiation

4. Types of radiation common to decay • When atoms decay, or change form to another atom, they emit one or more of the following that we classify as radiation • Alpha particles • Beta particles • Gamma rays

5. Alpha particles • Alpha particles are comprised of 2 protons and 2 neutrons that are emitted from an atom as it decays (YES, this is a helium nucleus!!) • Alpha particles are high energy but cant penetrate much of anything, a simple piece of paper or cloth is an effective shield • Alpha particles can do damage to the surface of a material though because of their high kinetic energies • After travelling just a few centimeters in air, the alpha particle will pick up electrons and become nothing more than harmless helium

6. Beta particles • Beta particles are actually electrons ejected from the nucleus of an atom (that should make you think) • Beta particles are not as easy to stop as alpha particles and can penetrate light materials such as clothing and paper. • They can penetrate deeper into skin and harm cells • They cannot penetrate deeply into denser materials such as aluminum • Once within a material they just become an electron and part of an atom no different from any other electron

7. Gamma rays • Gamma rays are high frequency, high energy (higher than X-rays) radiation emitted from a radioactive atom • Because they have no mass and no charge they can penetrate most materials • Although they cannot penetrate unusually dense materials such as lead • Gamma rays can cause structural damage to living cells and can damage DNA leading to mutations • Gamma rays are generaly more damaging to us than alpha of beta particles (unless those particles are injested)

8. Neutrons • Neutrons are considered the fourth radiation health hazard • They are ejected from a nucleus • Can penetrate deeply into materials • Slowed by hydrogen and hydrocarbons • They can make materials radioactive

9. Radiation dose equivelant • As mentioned some radiation is more damaging than others and therefore we report dosage in rems. • While 1 rad of beta radiation results in 1 rem. 1 rad of alpha radiation results in 10 rems! • This is body exposure • Neutrons and gamma rays are more complex

10. Sources of radiation • Natural • Cosmic radiation • Ground • Air • Human tissue • Man made • Medical procedures • TV tubes, electronics • Weapons fall out • Coal fired power plants

11. Determining annual dosage • NRC personal annual radiation dose calculator

12. Lecture Review • Radioactivity • Radiation • Beta • Alpha • Gamma • neutron • Radiation dose

13. Recommended exercises • Using the NRC calculator, calculate what your annual dosage of radiation is. • Teach someone the 4 types of radiation covered explaining where they come from, whether it is a particle or energy, and what kind of shielding is needed