Sources of RadiationSources of Radiation
• Natural background radiation is everywhere
• There are terrestrial and cosmic sources as
well as those all over our planet.
• The level is variable by location.
• The largest single source is radon. Radon is
a radioactive gas that can accumulate in
homes and in the workplace. The levels vary
by location but the national average is 200
Typical natural background levels areTypical natural background levels are
60 mrem in NE, E, W, and Central60 mrem in NE, E, W, and Central
United States.United States.
45 mrem in Atlantic and Gulf Coastal45 mrem in Atlantic and Gulf Coastal
states and 120 mrem in the Coloradostates and 120 mrem in the Colorado
The amount of radiation the typicalThe amount of radiation the typical
radiation worker is exposed to is aboutradiation worker is exposed to is about
the same order of magnitude as anthe same order of magnitude as an
average abdominal radiograph or aaverage abdominal radiograph or a
year’s background exposure.year’s background exposure.
Units of Activity in U.S.Units of Activity in U.S.
• In the United States, exposure is commonly
measured in units of mrem, or 1/1000 of a Rem.
In other countries the unit of measure is typically
the “millisievert”. This is defined later.
• In this exercise we are only concerned with
ionizing radiation because it contains sufficient
energy to break chemical bonds by removing an
electron from an atom or molecular substance.
• Breaking of bonds in biological systems can
cause the system to malfunction.
Kinds of Radiation at UnionKinds of Radiation at Union
• At Union College the radiation sources are
sources of Alpha particle, Beta particle,
gamma radiation, X-rays, and in some
• Alpha particles lose their energy in short
distances, as within 2 inches of air or the surface
of skin thus generally it is not dangerous. Its
danger is if it enters the body internally where its
lifetime and energy can be very harmful.
• i.e., Alpha emitters mostly come from long lived
isotopes like uranium so emit for a long time.
Most Common Radiation atMost Common Radiation at
Union CollegeUnion College
• Beta emitters are the most common isotopes
dealt with at Union College.
• They can typically penetrate into the skin
one/half inch, through a few feet of air but might
be blocked by a plastic shield. A problem with a
shield made from dense material is that the Beta
particle can generate other radiation which is
detected beyond the expected penetration
depth. Often this radiation is gamma.
• Beta emitting isotopes life times vary over a
Non-particulate RadiationNon-particulate Radiation
• Gamma radiation is not a particle like first
two. It penetrates many shields and
normally requires several inches of lead to
stop it. Its source might be from isotopes
undergoing decay and can come from
beta particles striking certain materials.
Their energy levels vary considerably and
so exposure to them is not recommended.
They find use in medical imaging.
The Third ParticleThe Third Particle
• Neutrons are particles and being neutral
in charge typically penetrate most
materials without interaction. Their danger
depends on the energy of the neutron.
Typically Union College’s only
“connection” with them is their use for
activating materials for analysis by the
Geologists via neutron activation done at
Oregon State University.
Quantity of RadiationQuantity of Radiation
• Dose: This is a generic term for the
quantity of absorbed radiation per unit
mass. “Dose equivalent” is the term for
quantity of absorbed dose in tissue
modified by certain risk factors dependent
upon the type of radiation to which one is
• Dose rate: Is the absorbed dose delivered
per unit of time
More Radiation TerminologyMore Radiation Terminology
• Rad: Is the “absorbed radiation dose”, the
unit of dose (or energy absorbed) per unit
mass in materials, including tissue. The
international unit is the Gray ( 1 Gy = 100
What is a Roentgen?What is a Roentgen?
• It is the unit to measure ionization in air as a
result of exposure to X-Rays or gamma-
radiation; there is no international equivalent
• Curie: A unit of activity of radioactive substances
(decaying at the rate of 3.7 E10 disintegrations
per second per curie); The international unit for
activity is the becquerel ( 1 disintegration per
second). It is abbreviated “Bq”. 3.7E10 Bq is one
Even More RadiationEven More Radiation
• Rem: This is most commonly the term
used by the Radiation Safety Officer. It is
“the Roentgen Equivalent in Man” versus
air, i.e., it is unit of effective dose that
corrects absorbed dose for the risk for
high energy particle radiation which do
more damage to tissue than an equivalent
absorbed dose of X- or Gamma-rays.
International unit is sievert (1 Sv = 100
An Important term relating theAn Important term relating the
strength of your samplestrength of your sample
• Curie: The unit of activity of radioactive
substances (decaying at the rate of 3.3
E10 disintegrations per second is a curie.
The number comes from the activity of
uranium. At Union College we deal mostly
with mCi or uCi. The international unit of
activity is the becqueral (1 disintegration
per second) abbreviated Bq.
How do we describe or discussHow do we describe or discuss
the life or stability of an isotope?the life or stability of an isotope?
• This is measured by a term called “half-life”. The
larger this number the more stable and longer
lived is that isotope. It represents the amount of
time for half of the quantity of the isotope to
undergo decay, i.e., changed into a different
isotope or isotopes.
• The t1/2 for tritium is small compared to that of
uranium; U-238 is about 4E9 years while tritium
is about 12 years. Any given quantity of H3
disappears in about 120 years, about ten half-
Less commonly used termLess commonly used term
• Sometimes we are concerned with the radiation
near the surface.
• The Half Value Layer is the thickness of a given
substance required to cut exposure from a beam
of radiation in half. Such a layer might be 20 to
80 percent of total radiation being emitted.
• Leak Test: Is a test of the surface of a sealed
source to determine whether the seal is still in
Man-made sources of exposureMan-made sources of exposure
• Typically an individual might encounter
sources of radiation in
• diagnostic radiology
• Nuclear medicine
• Radiation therapy
• During medical X-ray analysis
• In a Laboratory
Most Common SourcesMost Common Sources
• But the most common sources of radiation
are in water (even bottled water), soil, and
the air. Radiation received from the sun
and natural radioactive material (ores) are
often a greater source of radiation
exposure than the radiation found in the
workplace. In the United States, Colorado
has about the highest level in soil.
What are the undesirable effectsWhat are the undesirable effects
from higher exposuresfrom higher exposures
• Although low when adhering to safe
radiation standards undesirable effects
from higher exposures are
• Genetic mutations
• Effects on an embryo/fetus
Effects from various exposureEffects from various exposure
• Even though radiation can be of great
benefit, too much exposure, like from the
sun can be dangerous. Two types of
• 1. Effects that will occur when given a
certain minimum exposure (or threshold
• 2. Effects that have a higher chance of
occurring with higher levels of exposure.
Effects from Threshold Levels ofEffects from Threshold Levels of
radiation exposureradiation exposure
• Cataracts in the eyes
• Skin erythema (skin reddening)
• Hair loss
• Precancerous skin conditions
Given these effects what areGiven these effects what are
normal levels of radiation in anormal levels of radiation in a
• Radiation Oncology 5K rad (tumor
• CT of Pelvis 1 rad. or CT of Head 3 rad
• Chest X-ray 15 mrad
• Dental exam 300 mrad
• Mammogram 150 mrad glandular dose
Chances of Getting CancerChances of Getting Cancer
• However, the reality is that risks from
natural and most medical levels of
radiation are quite low. The chance of
getting cancer from 10 mrem of radiation
is equivalent to the change of winning the
lottery when you bought only one lottery
What are the Occupational DoseWhat are the Occupational Dose
• Effective dose: 2E3 mRem per year
• To the lens of the eye: 15E3 mRem
• To the skin: 50E3 mRem
• To the hands, feet, knees, elbows: 50E3
• Those expected to receive 10% of the limit
level must wear dosimeters.
How do we minimize exposure?How do we minimize exposure?
What are Safe PracticesWhat are Safe Practices
• The ALARA (as low as reasonably
achievable) philosophy and its guidelines
are what help to keep the risk or radiation
down. The ALARA guidelines are limits
established to ensure that safety is
maintained. We know the lower doses
carry lower risk, and this concept helps to
maintain cost effective safety.
• Time: Less exposure time means lower
• Distance: The radiation level falls off at a
rate of inverse square of the distance. So
stay as far from the sample as possible
• Shielding: As indicated earlier, various
shields can diminish or block the radiation
Key Safety TipsKey Safety Tips
• Be able to recognize radiation signage and
which packages might contain radioactive
materials. Apply the ALARA practice to them.
• Do not consume anything or put items like
cosmetics on your face where there are
radioactive material or might have been from
contamination. Wear gloves, wash hands.
• If radioactive materials are spilled, restrict
access to the area and contact the Radiation
Who should be speciallyWho should be specially
• Individuals close to their exposure limits
• Females who are pregnant or might become
• Young children or infants
• Old frail individuals
• Those who have cancer or similar diseases
• Women might want to declare they are pregnant
because exposure limits are lower for them thus
protecting the fetus.
So what do you do in a RadiationSo what do you do in a Radiation
• Follow the letters in the word RACE
• R rescue or evacuate anyone in the area
of a spill or condition of high exposure
• A alarm, sound one if appropriate
C call the Radiation Safety Officer (RSO)
E exit the area but be close enough to
communicate with the RSO information
Contact NumbersContact Numbers
• Campus Safety 388-6911 This is a good
first number as they can contact the RSO
via radio or by using one of several phone
• RSO 388-6911 (office number) or (518)
788-1181 (cell phone which is normally
carried at all times by the RSO)
• Please complete the following Quiz and
submit to the RSO
• Quiz questions for Radiation Program
• Where besides a laboratory with radioactive materials might you find ionizing radiation? Give three examples
• Which state in the United States has the highest natural background levels of radiation?
• What ionizing radiation material are you using or will be using in your research?
• Which ionizing radiation particle could be most harmful to you but also has a short distance of travel in air?
• What is one potential problem with assuming that beta particle radiation can be stopped with a high density
material and there would be no other radiation in the area.
• Which generic term applies to the quantity of absorbed radiation per unit mass?
• What is described as a unit of activity of radioactive substance whose international unit is the becquerel?
• REM ?
• What term might be used to describe the stability of an isotope?
• Name a two potentially undesirable effects of high exposures to radiation.
• What is ALARA a mnemonic of ?
• What are the three terms most associated with the philosophy ALARA?
• Is it reasonable to put anything in your mouth which might have been exposed to radioactive material?
• In case of a spill, who always must be contacted (not necessarily the first person though)?
• Why are young children more susceptible to radiation damage than very old people?
• When an emergency arises, what do the letters “RACE” stand for?
• Should a spill of radioactive material or some other emergency related to radiation, what is the most sure fire
phone number to call?