Physical Science Lecture 106 Instructor: John H. Hamilton

Lecture Review Radioactivity Radiation – Beta – Alpha – Gamma – neutron Radiation dose

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

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

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

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

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)

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

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

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

Determining annual dosage NRC personal annual radiation dose calculator

Lecture Review Radioactivity Radiation – Beta – Alpha – Gamma – neutron Radiation dose

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