Basics of Radiation Topics Types of Radiation How

Basics of Radiation

Topics • • • Types of Radiation How Radiation Interacts With You Radiation Safety Why Measure Radiation Today Summary Radiation Equivalents 2

Two Types of Radiation • Radiation can be non-ionizing or ionizing • Non-ionizing radiation is generally a low energy electromagnetic wave – Sunlight – Radio waves – Microwaves – Infrared waves • Mostly harmless 3

Ionizing (Nuclear) Radiation • Has enough energy to ionize (alter) atoms and molecules • Because it can ionize, it can cause biological damage 4

Ionizing Radiation Ionizing radiation is all around us • Outer space, the earth, and medical treatments • Low levels of naturally occurring radioactive material are in our environment, the food we eat, and in many consumer products • Some consumer products also contain small amounts of man-made radioactive material • Most of your annual dose of radiation comes from Radon gas in your house 5

Types of Ionizing Radiation 6

Topics • • • Types of Radiation How Radiation Interacts With You Radiation Safety Why Measure Radiation Today Summary Radiation Equivalents 7

What is a Dose of Radiation? • When radiation hits your body, and its energy is transferred to your tissue, you have received a dose of radiation. • The more energy deposited, the higher your dose. • Measured in rem (R). 8

What is the Dose Rate of Radiation? • The amount of radiation given off by a source over time • Measured in rem per hour (R/h) 9

Gatling Gun Analogy • The number of bullets released per hour is the dose rate • The number of bullets that hit you is the dose 10

Irradiated or Contaminated? Irradiated • You are irradiated when radiation hits you • You do not become radioactive when you are irradiated • Many foods are irradiated to kill molds and bacteria 11

Irradiated or Contaminated? Contaminated • Contamination is radioactive dirt • You can become contaminated by touching radioactive dirt • Contamination can be washed off like any dirt 12

Radioactive Contamination Radiation cannot make you radioactive* * Understanding Radiation: Bjorn Wahlstrom (overrides copyright below) 13

Radioactive Contamination Radioactive contamination can stick to clothes and skin. It can be washed away like any dirt*. * Understanding Radiation: Bjorn Wahlstrom 14

Common Doses in Everyday Life 1 R = 1, 000 μR 15

Acute Radiation Doses 16

Topics • • • Types of Radiation How Radiation Interacts With You Radiation Safety Why Measure Radiation Today Summary Radiation Equivalents 17

Radiation Safety • The fundamental principle of radiation safety is that radiation exposure should be As Low As Reasonably Achievable (ALARA). • The three factors influencing radiation dose are: – Time – Distance – Shielding 18

ALARA - Time • The less time you’re exposed, the less exposure you get • Dose = Dose Rate x Time • Limit your time near the radiation source! 19

ALARA - Distance • The farther away from the source you are, the weaker the source is to you • Exposure levels are based upon the inverse square law • Increase the distance between you and the source! 20

ALARA - Shielding • Shielding can reduce or stop radiation from hitting you – α can be absorbed by a piece of paper – β can be absorbed by 1” of aluminum or glass – γ can be absorbed by thick lead shields – n can be absorbed by paraffin, water, polyethylene • Increase the amount of shielding material between you and the source! 21

Shielding/Attenuating Radiation b Water, Polyethylene Lead, Concrete g h Paper Glass, thin metal a 22

Topics • • • Types of Radiation How Radiation Interacts With You Radiation Safety Why Measure Radiation Today Summary Radiation Equivalents 23

Radiological Terrorism is a real and possible threat • High psychological/emotional impact • High economic impact • Many devices are easy to build • Al Qaeda has threatened radiological terrorism • It’s already being done 24

Threat Comparison Severity of incident Stolen nuclear weapon Improvised nuclear device RDD Probability of incident 25

Radiological Terrorism • Nuclear warheads use special nuclear materials – Plutonium – Uranium • Medical and industrial radioactive materials cannot produce a nuclear warhead – they can only be used to contaminate 26

Radiological Dispersion Devices RDDs take two main forms • A dirty bomb – Radiological material wrapped in conventional explosives • A simple radioactive source left discretely in a public place 27

Making an RDD • All you need is radiological material • Orphan sources – Radiological materials are used everyday in a variety of applications – Some sources are lost, forgotten, or disposed of improperly – orphan sources – Over 200, 000 available today 28

Example of an RDD • 1 pound of HE, two patient doses of liquid Technetium 99 m (Tc-99 m) near the HE • Weather: 30 degrees F, sunny, light winds with gusts of 20 mph 29

Example of an RDD Contamination measured at 4 times background 30

Commonly Available Isotopes Suitable For RDDs *Can be detected with a gamma sensor because daughter isotope emits gamma. 31

Innocent Sources • Radioactive sources seen in typical day to day operations – Cause innocent alarms – Could be used to disguise a real source • Containers of tile & bricks containing uranium & thorium • Containers of bananas & fertilizer containing potassium • Patients who have received nuclear medicine treatments 32

Topics • • • Types of Radiation How Radiation Interacts With You Radiation Safety Why Measure Radiation Today Summary Radiation Equivalents 33

Summary • Dose is measured in R – Cumulative effect on the body • Dose rate is measured R/h – Amount of radiation in your vicinity • Contamination is radioactive particles in or on the body • Irradiation is exposure to a radioactive source 34

Summary Three factors influence radiation dose • Time • Distance • Shielding 35

Questions? RAE Systems 3775 North First Street San Jose, CA 5134 Voice: 408 -952 -8200 Fax: 408 -952 -8480 www. raesystems. com 36

Topics • • • Types of Radiation How Radiation Interacts With You Radiation Safety Why Measure Radiation Today Summary Radiation Equivalents 37

Radiation Equivalents Rem Millirem (mrem) Microrem (µrem) 1 1, 000, 000 0. 1 100, 000 0. 01 10 10, 000 0. 001 1 1, 000 0. 0001 0. 1 100 0. 00001 0. 01 10 0. 000001 0. 001 1 38

Radiation Equivalents Unit Rad, Grey (Gy) Measured Quantity Absorbed Dose Rem, Sievert (Sv) Biologically Equivalent Dose Unit Equivalents 100 Rem 1 Sv 1 Rem 10 m. Sv (millisievert) 1 mrem (millirem) 10 m. Sv (microsievert) 1 mrem (microrem) 0. 01 m. Sv 39