INTRODUCTION TO RADIATION: RADIATION TYPES

TYPES OF IONIZING RADIATION Alpha Particles Stopped by a sheet of paper Beta Particles Stopped by a layer of clothing or less than an inch of a substance (e.g. plastic) Gamma Rays Stopped by inches to feet of concrete or less than an inch of lead Radiation Source

An alpha particle consists of two protons and two neutrons  Very large on an atomic scale  Positively charged Penetration in materials  Outside the body, an alpha emitter is not a hazard unless it is on the skin  Inside the body, an alpha emitter is a bigger hazard if it deposits its energy in sensitive tissue Radiation Types - Alpha

Common alpha-particle emitters  Radon-222 gas in the environment  Uranium-234 and -238 in the environment  Polonium-210 in tobacco Common alpha-particle emitter uses  Smoke detectors  Cigarettes/cigars  Static eliminators Radiation Types - Alpha

A beta particle is a charged electron  Has the size and weight of an electron  Can be positively or negatively charged Penetration in materials  At low energies, a beta particle is not very penetrating – stopped by the outer layer of skin or a piece of paper  At higher energies, a beta particle may penetrate to the live layer of skin and may need 0.5” of plexiglass to be stopped Radiation Types - Beta

Penetration in materials, continued  Inside the body, a beta particle is not as hazardous as an alpha particle because it is not as big  Because it is not as big, it travels farther, interacting with more tissue (but each small piece of tissue gets less energy deposited) Radiation Types - Beta

Common beta-particle emitters  Tritium (hydrogen-3) in the environment  Carbon (14) in the environment  Phosphorus (32) used in research and medicine Common beta-particle emitter uses  Carbon dating  Basic research  Cancer treatment Radiation Types - Beta

A photon is an x or gamma ray  Has no weight  Has no charge Penetration in materials  At low energies, a photon can be stopped by a very thin (almost flexible) layer of lead or several centimeters of tissue  At higher energies, inches of lead might be necessary to stop a photon and they can pass right through a human Radiation Types - Gamma

Common photon emitters  Cesium (137)  Technetium (99m) used in medicine  Iodine (131) used in medicine Common photon emitter uses  Determining the density of soil  Diagnosing disease  Cancer treatment Radiation Types - Gamma

Gamma Decay

Physical Radioactive Half-Life Use Cesium yrs Food Irradiator Cobalt-60 5 yrs Cancer Therapy Plutonium-23924,000 yrs Nuclear Weapon Iridium days Industrial Radiography Hydrogen-3 12 yrs Exit Signs Strontium-9029 yrs Eye Therapy Device Iodine days Therapy Technetium-99m 6 hrs Imaging Americium yrs Smoke Detectors Radon days Environmental EXAMPLES OF RADIOACTIVE MATERIALS

RATES OF RADIOACTIVE DECAY 1.All things do not decay at the same rate some decay faster than others do. 2.We use this time to gauge how old something is. 3.Based on how much of a parent element is present compared to the daughter element we can make a guess at how the object was when it started decaying

HALF-LIFE 1.Half-Life is the amount of time it takes for one half of a sample of a radioactive element to decay into its daughter element. 2.Nuclear decay rates are constant and do not change. 3.After one half life how much of the substance would you have? 4.After 2 half lifes? 5.After 3 half lifes? 6.Increments of half life for what remains of the original amount is 1. 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128, 1/256

Half lives and radiation of selected radioisotopes IsotopeHalf-LifeNuclear Radiation Emitted Radon daysAlpha Iodine daysBeta Thorium daysBeta, Gamma Radium yearsAlpha, Gamma Carbon yearsBeta Thorium-23075,200 yearsAlpha, Gamma Uranium ,000,000 yearsAlpha, Gamma Potassium- 40 1,280,000,000 years Beta, Gamma Uranium-2384,470,000,000 years Alpha

FISSION 1.Splitting an atomic nucleus into two smaller atoms. 2.Nuclear Bombs 3.Lots of energy from Fission 4.Energy released from one kg of uranium-235 is equivalent to burning 17,000 kg of coal!

FISSION

FUSION 1.Process in which the nuclei of 2 atoms combine to form a larger nucleus. 2.Happens in all stars 3.Two hydrogens combine to form a helium but part of the mass turns into pure energy. 4.If we could harness that energy there is enough energy to fuel new york city for about a month in a tiny piece of chalk.