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Radiation Fundamentals
Objectives: Identify the three basic particles of an atomDefine radioactive material, radioactivity,
radioactive half-lifeDefine ionization and ionizing radiationDistinguish between ionizing radiation and non-
ionizing radiation Identify the four basic types of ionizing radiation
Physical characteristics Range Shielding Biological hazards
What is an Atom
Atomic Structure
The basic unit of matter is the atom. The three basic particles of the atom are:
protons, neutrons, and electrons.
The central portion of the atom is the nucleus. The nucleus consists of protons and neutrons.
Electrons orbit the nucleus.
NotationsA
Z XA = Atomic Mass (number of protons or electrons
plus number of neutrons)
Z= Atomic Number (number of Protons) or (number of Electrons in an electrically neutral atom)
Number of Neutrons = A - Z
Notations
Tritium is designated as:
T or H-3 or H
23892
Uranium (238) is designated as:
U-238 or U
3
1
What are Isotopes ?
They are not just a sports team on the Simpsons.
The IsotopesAtoms which have the same number of protons
but different numbers of neutrons are called isotopes.
Isotopes of Carbon.
The Isotopes.
ISOTOPES of hydrogenProtium H Deuterium D Tritium T
No neutrons 1 neutron 2 neutrons
H D T
n nn
The different isotopes of an atom are chemically identical. The above isotopes of hydrogen all act chemically the same.
What is Radioactivity ?
If there are too many or too few neutrons for a given number of protons, the nucleus will not be stable.
The unstable atom will try to become stable by giving off excess energy. This energy is in the form of particles or rays (radiation). These unstable atoms are known as radioactive atoms, or radioactive materials.
How do unstable Isotopes become stable?
By Radioactive decay
Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting ionizing particles and radiation. This decay, or loss of energy, results in an atom of one type, called the parent nuclide transforming to an atom of a different type, called the daughter nuclide.
How long does Radioactive decay take?
Half life it’s more than just a game.
Radioactive half-lifeThe radioactive half-life for a given
radioisotope is the time for half the radioactive nuclei in any sample to undergo radioactive decay.
After one half-life, there will be one half the activity of the original sample. After two half-lives, there will be one fourth the activity of the original sample, after three half-lives one eighth the activity of the original sample, and so forth.
Radioactive Decay is an Exponential Process
The activity at time (t) is related to the initial activity at time (0)
To determine the activity present after time (t)
You need to know
1. The initial activity of the isotope involved. (Activity at time “0” or Ao)
2. The half life of the radioactive isotope.(T1/2)
3. The time after the initial activity was determined.
(T after the determination at time “0”)
Example
You have 10 mCi of P-32 on January 1, 2008.
How much activity will you have on January 29, 2008?
Given: The half life of P-32 is 14.3 days.
Solution
Known: 1. Ao = 10 mCi
2. T1/2 = 14.3 days3. Time after initial activity (t) =
28 days
Using A (t) = Ao e-t
= 10 e –(0.693/14.3)(28)
= 2.57 mCi
Example: Decay of 32P in time
Radioactivity may be defined as:
Spontaneous nuclear transformation
Non-ionizing vs. Ionizing radiation
Non-ionizing radiation refers to any type of electromagnetic radiation that does not carry enough energy per quantum to ionize atoms or molecules — that is, to completely remove an electron from an atom or molecule.
Examples of non-ionizing radiation: microwaves, ultraviolet light, lasers, radio waves, infrared light, and radar.
Ionizing radiation consists of subatomic particles or electromagnetic waves that are energetic enough to detach electrons from atoms or molecules, ionizing them.
Examples of ionizing radiation: alpha particles, beta particles, neutrons, gamma rays, and x-rays.
IonizationIonization is the process of removing
electrons from neutral atoms. It is important to note that exposure to
ionizing radiation, without exposure to radioactive material, will not result in contamination of the worker.
Two general categories of ionizing radiation:
PARTICLES
alpha
neutron
beta
PHOTONS
X-ray
gamma ray
Radiation Fundamentals
The Four Basic Types of Ionizing Radiation
alpha particles, beta particles,
gamma or X rays, neutrons.
Alpha ParticlesPhysical Characteristics: Large mass,
highly charged, helium nuclei (2 protons, 2 neutrons)
Range: 1-2 inches in airShielding: Dead layer of skin, paper.Biological Hazards: Internal, it can
deposit large amounts of energy in a small amount of body tissue.
Alpha ParticlesAlpha particles are highly energetic helium nuclei p+
p+
cannot get through skin
stopped by paper
internal hazard
soil, radon, and heavy man-made elements
Beta ParticlesPhysical Characteristics: Small mass,
electron size, Range: Short distance (one inch to 20
feet).Shielding: PlasticBiological Hazard: Internal hazard.
Externally, may be hazardous to skin and eyes.
Beta ParticlesBeta particle: an energetic electron
from an unstable nucleus
skin, eye, and internal hazard
stopped by plastic
natural food, water, air
Gamma Rays/X-RaysPhysical Characteristics: No mass. No charge.
Electromagnetic wave or photon.Range: Very far. It will easily go several
hundred feet. Very high penetrating power.Shielding: Concrete. Water. Lead.Biological Hazard: Whole body exposure. The
hazard may be external and/or internal. This depends on whether the source is inside or outside the body.
Gamma Rays/X-Rays
Gamma and X-rays are photons (massless electromagnetic energy)
stopped by dense shielding
naturally present in soil and in
cosmic radiation
medical, radioactive materials
NeutronsPhysical Characteristics: Fairly large. No
charge. Has mass.Range: Range in air is very far. Easily can go
several hundred feet. High penetrating power due to lack of charge (difficult to stop).
Shielding: Water. Concrete. Plastic (high hydrogen content).
Biological Hazard: External whole body exposure.
SUMMARY of External and Internal Hazards
External Internal
Alpha Minimum Severe
Beta Higher than Alpha Less severe than Alpha
X-ray and Gamma
Severe Less severe than Alpha, Beta
Neutron Severe Not considered
Review.The three basic particles of an atom are,
protons, neutrons, and electrons.
Radiation is energy in the form of particles or rays given off by unstable atoms.
The half-life for a given radioisotope is the time for half the radioactive nuclei in any sample to undergo radioactive decay.
Review cont.Ionizing radiation consists of radiation
energetic enough to detach electrons from atoms or molecules, ionizing them.
Non-ionizing radiation refers to any type of electromagnetic radiation that does not carry enough energy to completely remove an electron from an atom or molecule.
Review cont.The four basic types of ionizing
radiation are: alpha particles, beta particles, gamma or X rays, neutrons.
Alpha particles, Large mass, highly charged, Range: 1-2 inches in air, Shielding: Dead layer of skin, paper. Biological Hazards: Internal
Beta particles, Small mass, Range: one inch to 20 feet. Shielding: Plastic. Biological Hazard: Internal hazard. Externally, may be
hazardous to skin and eyes.
Review cont.The four basic types of ionizing radiation
cont:
Gamma or X rays, No mass. No charge. Range: It will easily go several hundred feet. Very high
penetrating power. Shielding: Concrete. Water. Lead. Biological Hazard: External whole body exposure.
Neutrons, Fairly large. No charge. Has mass. Range: Easily can go several hundred feet. High
penetrating power due to lack of charge. Shielding: Water. Concrete. Plastic (high hydrogen
content). Biological Hazard: External whole body exposure.
Test Time!
Follow this link to the test. https://myresearch.wsu.edu
Use your WSU user name and password to sign in.
Click on the training tab.Then click on the available training tabFind the basic radiation physics course, in
the OR section, click on it and take the test.