Transcript Radiation Safety Training Basic Radiation Physics (Materials)

Radiation Safety Training
Basic Radiation Physics
Washington State University
Radiation Safety Office
Radiation
Fundamentals
Objectives:




Identify the three basic particles of an atom
Define radioactive material, radioactivity, radioactive half-life
Define ionization and ionizing radiation
Distinguish 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.
Notations
A
Z
X
A = 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:
3
T or H-3 or H
1
Uranium (238) is designated as:
238
U-238 or
U
92
What are Isotopes ?
 They are not just a sports
team on the Simpsons.
The Isotopes
 Atoms which have the same number of protons
but different numbers of neutrons are called
isotopes.
Isotopes of Carbon.
The Isotopes.
ISOTOPES of hydrogen
Protium H
Deuterium D
n
No neutrons
H
1 neutron
D
Tritium T
n
n
2 neutrons
T
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-life
 The 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.
(DT 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
Example:
Decay of 32P in time
 Known:
1. Ao = 10 mCi
2. T1/2 = 14.3 days
3. Time after initial activity (t) = 28 days
 Using
A (t) = Ao e-lt
= 10 e –(0.693/14.3)(28)
= 2.57 mCi
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.
Ionization
 Ionization 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:
PHOTONS
PARTICLES
alpha
X-ray
neutron
beta
gamma ray
Radiation
Fundamentals
 The Four Basic Types of Ionizing Radiation
alpha particles,
 beta particles,
 gamma or X rays,
 neutrons.

Alpha Particles
 Physical Characteristics: Large mass, highly
charged, helium nuclei (2 protons, 2 neutrons)
 Range: 1-2 inches in air
 Shielding: Dead layer of skin, paper.
 Biological Hazards: Internal, it can deposit large
amounts of energy in a small amount of body
tissue.
Alpha Particles
Alpha particles are highly
energetic helium nuclei
cannot get
through skin
p+
p+
internal
hazard
stopped
by paper
soil, radon, and heavy
man-made elements
Beta Particles
 Physical Characteristics: Small mass, electron
size,
 Range: Short distance (one inch to 20 feet).
 Shielding: Plastic
 Biological Hazard: Internal hazard. Externally,
may be hazardous to skin and eyes.
Beta Particles
Beta particle: an energetic electron
from an unstable nucleus
skin, eye, and
internal hazard
stopped
by plastic
natural food, water, air
Gamma Rays/X-Rays
 Physical 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
Neutrons
 Physical 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
Less severe than
Alpha, Beta
Not considered
X-ray and Severe
Gamma
Neutron
Severe
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 tab
 Find the basic radiation physics course, in the OR
section, click on it and take the test.