Radiation comes in three main types: alpha particles, beta particles, and gamma rays. Alpha particles are large and positively charged, but do not penetrate far, stopped by skin or paper. Beta particles are electrons that can penetrate further, stopped by clothing or plastic. Gamma rays have no charge or mass and penetrate the deepest, requiring thick concrete or lead to stop them. Each type interacts differently with matter and can be sources of radiation both inside and outside the body from uses like medical imaging, smoke detectors, and environmental sources like radon.

1. Introduction to Radiation:
Radiation Types
©Health Physics Society

2. Introduction to Radiation
• Objectives
• To provide useful information about
radiation for interested individuals
• To introduce basic concepts of radiation
and radioactivity
• Improve understanding of radiation –
what it is and how it interacts

3. 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

4. • 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

5. • 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

6. • 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

7. • 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

8. • 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

9. • 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 - Photon

10. • 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 - Photon

11. 99mTc
Excited
Nucleus
Gamma ray
99Tc
Stable Nucleus
Photon Decay

12. Physical
Radionuclide Half-Life Activity Use
Cesium-137 30 yrs 1.5 x 106 Ci Food Irradiator
Cobalt-60 5 yrs 15,000 Ci Cancer Therapy
Plutonium-239 24,000 yrs 600 Ci Nuclear Weapon
Iridium-192 74 days 100 Ci Industrial Radiography
Hydrogen-3 12 yrs 12 Ci Exit Signs
Strontium-90 29 yrs 0.1 Ci Eye Therapy Device
Iodine-131 8 days 0.015 Ci Therapy
Technetium-99m 6 hrs 0.025 Ci Imaging
Americium-241 432 yrs 0.000005 Ci Smoke Detectors
Radon-222 4 days 1 pCi/l Environmental
Examples of Radioactive Materials