1. Radiation Concepts Target Audience: Middle and High School
Includes: Detailed speaker notes and several useful graphics
General Description: Discusses the types of radiation and potential health effects (30 slides)

2. Definitions Ionizing Radiation
energy in the form of particles or waves, given off by
unstable (radioactive) atoms or by accelerated
charged particles
Radioactive Material
any material which emits ionizing radiation
Radioactive Contamination
radioactive material in an unwanted place
101-04

3. Radiation Radioactive Atom Ionizing Radiation Alpha Particle
Neutron Particle
Beta Particle
Radiation is energy of two types: energetic particles and electromagnetic waves. Particles have mass, may have an electric charge, and transfer energy to matter by their motion. The particles of most interest when discussing ionizing radiation include: alpha, beta, and neutrons. Electromagnetic waves exhibit both a (1) particle nature with energy bundles called photons, but they do not have any mass, and (2) wave nature which is described by wavelength or frequency. Since the energy of the waves is proportional to their frequency only the shortest highest frequency waves like gamma and X-rays are energetic engough to be ionizing radiation.
Gamma Ray (X Ray)

4. Radioactive Material Radioactive Material - any material containing
Gamma Ray
Gamma Ray
Radioactive Material - any material containing
atoms that emit radiation.

5. Contamination
External Radiation
Contamination

6. Radioactive Contamination
Radioactive Contamination - is radioactive material
in an unwanted place.

7. Ionizing Radiation Ionizing Radiation - radiation with enough energy
Ionization Radiation
Ejected Electron
Neutrons
and Protons
Radioactivity is a natural and spontaneous process by which the unstable atoms of an element emit or radiate excess energy in the form of particles or waves. These emissions are collectively called ionizing radiation. Depending on how the nucleus loses this excess energy either a lower energy atom of the same form will result, or a completely different nucleus and atom can be formed.
Ionization is a particular characteristic of the radiation produced when radioactive elements decay. These radiations are of such high energy that when they interact with materials, they can remove electrons from the atoms in the material. This effect is the reason why ionizing radiation is hazardous to health, and provides the means by which radiation can be detected.
Ionizing Radiation - radiation with enough energy
to remove an electron from its atom.

8. Alpha Particle a Characteristics • +2 charge • 2 protons • 2 neutrons
• Large mass
Range
• Very short
range
• 1" -2" in air
Shielding
• Paper
• Outer layer
of skin
Hazards
• Internal
Sources
• Plutonium
• Uranium
• Radium
• Thorium
• Americium a a a a a
Alpha decay is a radioactive process in which a particle with two neutrons and two protons is ejected from the nucleus of a radioactive atom. The particle is identical to the nucleus of a helium atom.
Alpha decay only occurs in very heavy elements such as uranium, thorium and radium. The nuclei of these atoms are very “neutron rich” (i.e. have a lot more neutrons in their nucleus than they do protons) which makes emission of the alpha particle possible.
After an atom ejects an alpha particle, a new parent atom is formed which has two less neutrons and two less protons. Thus, when uranium-238 (which has a Z of 92) decays by alpha emission, thorium-234 is created (which has a Z of 90).
Because alpha particles contain two protons, they have a positive charge of two. Further, alpha particles are very heavy and very energetic compared to other common types of radiation. These characteristics allow alpha particles to interact readily with materials they encounter, including air, causing many ionizations in a very short distance. Typical alpha particles will travel no more than a few centimeters in air and are stopped by a sheet of paper.
Show decay on chart of nuclides,
Show smoke detector as application of alpha decay.

9. Beta Particle b Characteristics • -1 charge • Small mass Range
• Short range
• About 10'
in air
Shielding
• Plastic
safety
glasses
• Thin
metal
Hazards
• Skin and
eyes
• Can be
internal
Sources
• Radioisotopes
• Activation
Products
• Sealed
sources
Beta decay is a radioactive process in which an electron is emitted from the nucleus of a radioactive atom, along with an unusual particle called an antineutrino. The neutrino is an almost massless particle that carries away some of the energy from the decay process. Because this electron is from the nucleus of the atom, it is called a beta particle to distinguish it from the electrons which orbit the atom.
Like alpha decay, beta decay occurs in isotopes which are “neutron rich” (i.e. have alot more neutrons in their nucleus than they do protons). Atoms which undergo beta decay are located below the line of stable elements on the chart of the nuclides, and are typically produced in nuclear reactors.
When a nucleus ejects a beta particle, one of the neutrons in the nucleus is transformed into a proton. Since the number of protons in the nucleus has changed, a new daughter atom is formed which has one less neutron but one more proton than the parent. For example, when rhenium-187 decays (which has a Z of 75) by beta decay, osmium-187 is created (which has a Z of 76).
Beta particles have a single negative charge and weigh only a small fraction of a neutron or proton. As a result, beta particles interact less readily with material than alpha particles. Depending on the beta particles energy (which depends on the radioactive atom), beta particles will travel up to several meters in air, and are stopped by thin layers of metal or plastic.

10. Gamma Ray g Characteristics • No charge • No mass • Similar to x-rays
Range
• Long range
• About 1100'
in air
Shielding
• Lead
• Steel
• Concrete
Hazards
• External
(whole body)
• Can be
internal
Sources
• X-ray
machines
• Electron
microscopes
• Sealed
sources
• Accelerators
• Nuclear
reactors
• Radioisotopes
After a decay reaction, the nucleus is often in an “excited” state. This means that the decay has resulted in producing a nucleus which still has excess energy to get rid of. Rather than emitting another beta or alpha particle, this energy is lost by emitting a pulse of electromagnetic radiation called a gamma ray. The gamma ray is identical in nature to light or microwaves, but of very high energy.
Like all forms of electromagnetic radiation, the gamma ray has no mass and no charge. Gamma rays interact with material by colliding with the electrons in the shells of atoms. They lose their energy slowly in material, being able to travel significant distances before stopping. Depending on their initial energy, gamma rays can travel from 1 to hundreds of meters in air and can easily go right through people.
It is important to note that most alpha and beta emitters also emit gamma rays as part of their decay process. However, their is no such thing as a “pure” gamma emitter. Important gamma emitters including technetium-99m which is used in nuclear medicine, and cesium-137 which is used for calibration of nuclear instruments.
Paper
Plastic
Lead

11. Neutron Particle h Characteristics • No charge • Found in nucleus
Range
• Extended
range
Shielding
• Water
• Plastic
Hazards
• External
(whole body)
Sources
• Fission
• Reactor
operation
• Sealed
sources
• Accelerators
Paper
Lead
Water

12. rad (radiation absorbed dose)
Radiation Units
roentgen (R)
• measures exposure (ionization) of air by X-rays
& gamma-rays
rad (radiation absorbed dose)
• measures energy deposited in any material by
any type of ionizing radiation
rem (Roentgen Equivalent to Man)
• estimates biological damage or health risk due
to absorption of ionizing radiation
• unit of dose equivalent
One of the most biologically important considerations related to ionizing radiation is the amount of energy deposited in living matter. This is referred to as dose. The three commonly used dose measurements are the roentgen, rad, and rem.
1 R = 2.58 x 10-4 coulombs per kg of dry air
1 rad = 100 ergs per gram of material
1 rem = 1 rad x Q (quality factor) Q = 1 for x-rays and ranges up to 20 for neutrons or alpha particles
The Quality Factor (Q) accounts for the penetrating and ionizing characteristics of various types of radiation. It seems obvious that the massive alpha particle with it’s +2 charge would be the most damaging. However, it is exactly these two characteristics that also make it the least penetrating particle. FYI – the quality factor is sometimes called the relative biological effect (RBE). Neutrons carry no charge, have about the same mass as a proton, and are relatively penetrating. Beta particles have a single negative charge, are much less massive a neutron, and are not very penetrating.

13. Radioactivity Units Curie (abbreviated, Ci)
Measure the number of nuclear transformations
(disintegrations) which occur in a certain time period
Curie (abbreviated, Ci)
= 37,000,000,000 disintegrations per second (dps)
= 2,200,000,000,000 disintegrations per minute (dpm)
Radioactive contamination measures an amount of activity over a unit of surface area.
e.g dpm/100 cm2
When given a certain amount of radioactive material, it is customary to refer to the quantity based on its activity rather than its mass. The activity is simply the number of disintegrations or transformations the quantity of material undergoes in a given period of time.
The two most common units of activity are the Curie and the Becquerel. The Curie is named after Pierre Currie for his and his wife Marie’s discovery of radium. One Curie is equal to 3.7x1010 disintegrations per second. A newer unit of activity if the Becquerel named for Henry Becquerel who is credited with the discovery of radioactivity. One Becquerel is equal to one disintegration per second.
It is obvious that the Curie is a very large amount of activity and the Bequerel is a very small amount. To make discussion of common amounts of radioactivity more convenient, we often talk in terms of milli and microCuries or kilo and MegaBecquerels.
When dealing with large amounts of material, either solids, liquids or gases, it is often convenient to talk about the activity in a given mass or volume of the material. This is called the specific activity of the material. 2

14. Prefixes Used with Radiation Units
Prefix Symbol Translation Numerical Value Scientific Notation
Tera T 1 trillion 1,000,000,000,
Giga G 1 billion 1,000,000,
Mega M 1 million 1,000,
Kilo k 1 thousand 1,
Milli m 1 thousandth 1/1,
Micro m 1 millionth 1/1,000,
Nano n 1 billionth 1/1,000,000,
Pico p 1 trillionth 1/1,000,000,000,

15. Prefixes – Examples Nuclear plant - 1000 megawatts (MW) electric power
1 kilogram (kg) weighs 2.2 pounds
Chest X-Ray dose = 5 millirem (mrem)
Biochemist might use a 10 microCurie (mCi) source
10 nCi/100 cm2 = low level radioactive contamination
Natural radium content of soil = 1 picoCi/gram (pCi/g)

16. millirem Abbreviation: mrem 1000 mrem = 1 rem
millirem - is the basic unit of radiation dose
equivalent. It measures biological risk in humans.

17. Half-Life The time required for the amount of radioactive material
200
400
600
800
1000
1200
New
1 Half-
Life
2 Half-
Lives
3 Half-
4 Half-
Activity
The time required for the
amount of radioactive material
to decrease by one-half
Half-life is the time required for the quantity of a radioactive material to be reduced to one-half its original value.
All radionuclides have a particular half-life, some of which a very long, while other are extremely short. For example, uranium-238 has such a long half life, 4.5e109 years, that only a small fraction has decayed since the earth was formed. In contrast, carbon-11 has a half-life of only 20 minutes. Since this nuclide has medical applications, it has to be created where it is being used so that enough will be present to conduct medical studies.

18. Acute Radiation Dose Acute radiation dose refers
to persons who receive
large amounts of
radiation over a
short period of time.

19. Chronic Radiation Dose
Chronic radiation dose refers to
persons who receive small amounts
of radiation over a long period of time.

20. Chronic Radiation Dose
Chronic radiation dose refers to persons who
receive small amounts of radiation over a
long period of time.
There is a slight risk that
cancer may be caused by
chronic radiation doses.
This risk level is very small compared
to the natural occurrence rate of cancer.

21. LNT Assumption The previous statements assume a Linear,
No-Threshold (LNT) response to radiation.
There is a growing body of scientific evidence
that this assumption is incorrect, and that low
levels of radiation exposure are not harmful.
There is also evidence that low levels of
radiation exposure can have a beneficial
(i.e., hormesis) effect.

22. Material Can Enter the Body
Four Ways Radioactive
Material Can Enter the Body
Inhalation
• Breathing
• Smoking
Wound or Cut
Ingestion
• Eating
• Drinking
• Chewing
Absorption

23. Biological Effects of Radiation
Cells are
undamaged.
Cells are damaged,
repair damage and operate normally.
repair damage and operate abnormally.
Cells die as a
result of damage.
Whatever the source and amount of ionizing radiation, it will have some biological effect on living organisms. Atoms become ionized when the radiation displaces electrons. These altered atoms will affect the molecules to which they belong and therefore the biological cells to which the molecules belong.
The biological effect on the cell may be direct or indirect. If the radiation interacts with the cell DNA, the cell is considered to be directly affected. If the radiation interacts with the water within the cell to create radicals, which have the capability to form toxic substances such as hydrogen peroxide the cell is said to be indirectly affected. The results of these interactions depend on the sensitivity of the cell type and on the amount and type of radiation the cell receives.
Living cells are not equally sensitive to radiation. Rapidly reproducing cells, such as those of a fetus, are more sensitive than those cells which have a longer time to repair damage before reproducing. Cells damaged by radiation respond one of four ways:
The cells are not damaged
Less active cells that receive small amounts of radiation are able to complete the normal repair of damage
Incomplete or incorrect repair of damage may cause the cell to operate abnormally or causes future generations of cells to have mutations
Large amounts of damage cause the cell to die

24. Health Effects • Radiation effects on cell chromosomes:
Somatic Effects
observed in the exposed individual
Heritable (Genetic) Effects
observed in future generations of
exposed individual
Low dose exposures are not clinically detectable. That means that long term effects can only be estimated in statistical studies of whole populations. There are two main categories of health effects due to radiation exposure: somatic and genetic effects.

25. Factors Affecting Biological Damage
RW I
Factors Affecting
Biological Damage
• Total radiation dose
• Dose rate
• Type of radiation
• Area of body exposed
• Cell sensitivity
• Individual sensitivity
102-13

26. sensitive than an adult.
The fetus is MORE
sensitive than an adult.
RW I
As a result of cellular sensitivity differences, organs with rapid cell growth tend to be more radio-sensitive to damage. Actively dividing white blood cells are thus more likely to be damaged than cells in muscles, nerves, the brain, or the skin. A developing fetus is very sensitive to radiation damage due to its rapidly reproducing cells and is most sensitive during the first three months, when cell reproduction is largest.

27. No Heritable Effects from Ionizing Radiation
Have Been Observed in Humans
Heritable effects have been observed in laboratory animals.

28. The average annual dose to the general
population from natural background
and man-made sources is 360 mrem.
Terrestrial Sources
Cosmic Radiation
Internal Sources
Other
Radon
Radiation can be found all around you. It is in the air, the soil, and the water. We transport it on our highways and it is used in many consumer products to sustain or enhance their operability. Many medical techniques would not be possible without the aid of radionuclides.
Radionuclides are found naturally in air, water and soil. They are even in found us, being that we are products of our environment. Every day, we ingest and inhale radionuclides in our air and food and the water. Natural radioactivity is common in the rocks and soil that makes up our planet, in water and oceans, and in our building materials and homes. There is no where on Earth that you can not find natural radioactivity.
Cosmic radiation is really divided into two types, primary and secondary. Primary cosmic radiation is made up of extremely high energy particles (up to 1018 eV), and are mostly protons, with some larger particles. A large percentage of it comes from outside of our solar system and is found throughout space. Some of the primary cosmic radiation is from our sun, produced during solar flares.
Little of the primary cosmic radiation penetrates to the Earth's surface, the vast majority of it interacts with the atmosphere. When it does interact, it produces the secondary cosmic radiation, or what we actually see here on Earth. These reactions produce other lower energy
radiations in the form of photons, electrons, neutrons and muons that make it to the surface.
The atmosphere and the Earth's magnetic fields also act as shields against cosmic radiation, reducing the amount that reaches the Earth's surface. With that in mind, it is easy to see that the annual dose you get from cosmic radiation depends on what altitude you are at. From cosmic radiation the U.S., the average person will receive a dose of 27 mrem per year and this roughly doubles every 6,000 foot increase in elevation.
Primordial radionuclides are left over from when the world and the universe was created and are primarily found in the earth’s crust. These radionucles are typically long lived, with half-lives often on the order of hundreds of millions of years. The three main components are potassium 40, Uranium 238 decay series and the Th-232 decay series. The amount of radioactivity found in your soil is dependent upon the type of underlying rock.
Radon is a noble gas that is produced by the decay of uranium, which occurs naturally in the soil. Radon itself is relatively harmless. As an inert gas, it is simply breathed into the lungs and then exhaled. Radon however decays into radioactive elements which are solids. These products if inhaled, can be retained within the lungs and can contribute significant doses to the lungs. They are often referred to as “radon daughters or “radon progeny”.

29. Average Annual Dose Cosmic 28 mrem Terrestrial Radon 200 mrem Internal
Medical X-Rays
Nuclear Medicine
14 mrem
Consumer Products
10 mrem
Other
3 mrem
Radon
200 mrem
Natural Sources
Man-Made Sources

30. Comparison of Radiation Dose

31. Relative risk of dying:
1 in a million odds.
RW I
• Smoking 1.4 cigarettes (lung cancer)
• Eating 40 tablespoons of peanut butter
• Eating 100 charcoal broiled steaks
• 2 days in New York City (air pollution)
• Driving 40 miles in a car (accident)
• Flying 2500 miles in a jet (accident)
• Canoeing for 6 miles
• Receiving 10 mrem radiation dose (cancer)

32. Risk – Loss of Life Expectancy
Days of Average Life Expectancy
Lost Due to Various Causes
3500
2250
1600
1100
777
365
227
207 60 10 6
Being an unmarried male
Smoking (1 pack/day)
Being an unmarried female
Being a coal miner
25% overweight
Alcohol abuse (U.S. average)
Being a construction worker
Driving a motor vehicle
All industries
Radiation: 100 mrem/yr x 70 years
Coffee
"Another way to look at risk is to ask
how many days of average life span
would be lost among persons who
partake in a certain activity. Be aware
that not everyone actually gives up
these many days of life. The table is
based on averaging the days lost by
the victim over the lives of all survivors."

33. Basic Protective Measures
Time
Distance
Radioactive materials produce a dose rate per time. There are some relatively simple methods to reduce the total dose received.
Minimizing the time can be an easy one to control. By planning ahead, the time to perform a job can be reduced. Also, knowing where the exposure rates are for a given work area can assist in identifying where to stand when performing work.
Shielding is extensively used throughout the industry. By shielding an area to be worked, the exposure rates can be reduced significantly. However, it is counterproductive if the person hanging the shielding receives more dose than the worker would have had he performed the work without the shielding.
The dose rate drops as the square of the distance. Therefore, by using an extension on a tool, the dose may be able to be cut significantly.
Shielding