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.