Radiation Safety Course Heath de la Giroday Dispensing Chemist Radiation Safety Officer.
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Transcript of Radiation Safety Course Heath de la Giroday Dispensing Chemist Radiation Safety Officer.
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Radiation Safety Course
Heath de la GirodayDispensing Chemist
Radiation Safety Officer
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Radiation and Radioactivity
Developed and Produced by:
Radiation Safety Institute of Canada
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Course ObjectivesTo provide you with an introduction to UNBC’s Radiation Safety Program and to understand:
1. Radioactivity and Radiation2. Biological Effects of Radiation3. Radiation Safety Regulations & Requirements4. Radiation Protection5. Radiation Monitoring
The First 3 sections will be reviewed by the students before the training class begins
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In This Session…• Structure of matter• Radiation• Ionizing and non-ionizing radiation• Radioactive decay• Common types of ionizing radiation
– Alpha– Beta– Gamma
• Activity and half-life
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The AtomThe atom is composed of:
Nucleusprotons,
neutrons,
and
electrons.
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The Atom
ParticleMass
(amu)Charge
Proton 1 +1
Electron 1/1836 -1
Neutron 1 0
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NomenclatureAtoms are often written with the notation:
SymbolAZ
Atomic Number
Mass Number
Chemical symbol(H for Hydrogen, C for Carbon, Pb for Lead, etc.)
Another common notation is: Symbol-A
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RadioactivityMost atoms in nature are stable.
If an atom is not stable,it is said to be unstable.
Stable implies that the forces acting on the nucleus of the atom are strong enough to hold it together indefinitely.
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Radioactivity
Unstable atoms want to become stable!
While becoming stable, unstable atoms emit radiation. This process is known as radioactive decay.
In an unstable atom, the nuclear forces are not strong enough to hold the nucleus of the atom together.
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RadioisotopesAtoms that are unstable are called radioactive.
Radioactive atoms can emit various types of radiation with different amounts of energy.
Radioactive atom, also known as:
radioisotope radionuclideor
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Isotopes of Hydrogen
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Sources of Radiation
Radioactive atoms Man-made devices
Where does radiation come from?
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Man-made1%
Medicinal18%
Radon62%
Cosmic6%
Terrestrial7%
Internal6%
Radiation Sources
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Radiation and Energy
• Radiation can be interpreted as a form of energy.
• Radiation will interact differently with matter depending upon how much energy it has.
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Interaction with MatterWhen radiation strikes matter, it interacts with the atoms of the matter.
RadiationAtom
Electron
Radiation with enough energy can knock electrons out of orbit from the atoms it strikes.
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Ionizing Radiation
Ion PairNeutral Atom
Electron
The process of creating ions is called ionization.
Radiation which can cause ionization is known as ionizing radiation.
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Types of Ionizing Radiation
Ionizing
Radiation
Alpha
Beta
Gamma
Proton Neutron
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Non-Ionizing RadiationRadiation which does not have enough energy to ionize atoms is called non-ionizing radiation.
Visible Light
Microwaves
Radio Waves
Infrared Light
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The Electromagnetic Spectrum
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Radiation
• Non-ionizing radiation– thermal– radio– microwave– infrared– visible light– ultraviolet
• Ionizing radiation– alpha particles– beta particles– gamma photons– x-rays– neutrons
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Radioactive Decay
• The process of radioactive decay may continue until the resulting atom is stable
• Some decay series, such as that of uranium, are quite long
• While others, such as that of iodine, are short
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Uranium Decay Series
In total,14 radioactive decays occur before the original radionuclide transforms into the stable isotope of lead.
U-238
Th-234Pa-234mU-234
Th-230
Ra-226
Rn-222
Po-218
Pb-214Bi-214Po-214
Pb-210Bi-210Po-210
Pb-206
4.5 billion years
3.8 days
3 minutes
Stable!
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Iodine Decay
• Iodine-131 decays to xenon-131 which is a stable nuclide
e)stable(XeI 01
13154
13153
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Alpha RadiationNucleus of a helium
atom (4He)Composed of two protons
and two neutrons
Carries two units of positive charge (+2)
Emitted from the nuclei of radioactive atoms
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Alpha Particles ()
• Highly energetic• 2 neutrons, 2 protons• Double charge• Limited penetrating
ability• Low external hazard• High internal hazard
42
22286
22688
42
42
RnRa
YX AZ
AZ
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Alpha Ionization• Alpha particles are highly ionizing.
• They can easily strip loosely bound electrons from atoms.
• Because of its size, the alpha particle does not travel far in matter:– Approximately 7 cm of air– Stopped by a piece of paper– Will not penetrate the dead outer layer of your skin
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Beta Particles (-) • Electron emitted from the
nucleus• Faster than • Smaller size• Single charge• External hazard to skin
and eyes– except H-3
• Internal hazard
SP
YX AZ
AZ
3216
3215
1
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Beta Radiation Penetration
• Maximum energy values for beta particles vary from 18 keV for 3H to 4.81 MeV for 38Cl
• Beta particles are less ionizing than alpha particles and can travel farther in matter:– Approximately 200 cm in air– They can penetrate the skin– Approximately 0.2 cm in tissue
• A thin layer of plastic is an effective shield.
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Typical Beta Emitters
P-32 I-131 Na-22
C-14 H-3 Sr-90
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Examples of Beta DecayPhosphorus-32
Sulfur-32
Beta particle (electron)
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Beta Radiation• When beta particles pass through
matter, x-rays can be produced.
X-ray machine
• The higher the atomic number, the more bremsstrahlung will be produced.
– This is called bremsstrahlung, meaning “braking radiation”
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Negative Beta Decay
• Like alpha decay, negative beta decay also results in the creation of a new atom which may itself be radioactive.
• For example, iodine undergoes beta decay and transforms into xenon
e)stable(XeI 01
13154
13153
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Positive Beta Decay
• Another example of beta decay is positron decay, which also results in the creation of a new atom
eNeNa 01
2210
2211
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Gamma Photons ()
• Electromagnetic radiation• Originate inside nucleus• No charge or mass• Travel at the speed of light• External hazard to whole body• Internal hazard
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Gamma Radiation
• Gamma radiation is not made up of physical particles like alpha or beta radiation.
• Gamma radiation is made up of photons.
– Photons are packets of energy with no mass.
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Gamma Radiation
• In other words, gamma radiation is electromagnetic radiation just like ordinary light.
• The energy of gamma radiation is much greater than that of ordinary light.
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Electromagnetic Spectrum
Courtesy NASA/JPL-Caltech
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Gamma Emission
• Gamma rays are emitted from the nuclei of radioactive atoms.– Unlike x-rays which are produced through
electron interactions.
• The emission of a gamma ray is always preceded by either a beta decay or an alpha decay.
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X-rays are emitted when high speed electrons are slowed down or change direction as a result of interactions with atoms in a target material.
X-Rays
X-ray
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Gamma Rays and X-Rays
• Both gamma rays and x-rays are ionising radiation.
• Gamma rays and x-rays do not have a range. – They can theoretically travel forever.
• However, as gamma rays and x-rays pass through matter, their intensity is reduced.
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Penetrating Power
Paper Aluminium Lead
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Radiation Units
• 1 becquerel (Bq) = 1 dps = 60 dpm– kBq, MBq, GBq, etc.
• 1 curie (Ci) = 3.7 1010 Bq– mCi, Ci, nCi, etc.
• Knowledge of both unit systems is necessary– 1 Ci = 37 GBq 1 Ci = 37 kBq– 1 mCi = 37 MBq 1 nCi = 37 Bq
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Activity
• The rate of radioactive decay is referred to as the activity.– The number of decays per unit of time.
• The SI unit of activity is the becquerel (Bq).– One becquerel is one decay per second.
• The historic unit for activity is the curie (Ci).1 Ci = 3.7 × 1010 Bq
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Activity
• Activity of 1 mg of U-238 is 10 Bq
• Activity of 1 mg of Am-241 is 1x108 Bq
• The drastic difference in activity between uranium-238 and americium-241 is related to a unique property of all radionuclides called the half-life
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Radiation Quantities
Exposure
Absorbed Dose
Equivalent Dose
Air Matter (Tissue)
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Exposure• Exposure is a means of measuring intensity of
ionizing radiation IN AIR• Coulomb/kilogram (C/kg)
– Amount of radiation-induced ionizations in a unit mass - not generally used
• Roentgen (R)– Quantity of radiation that produces 1 statcoulomb of
charge of either sign per cm3 of air at 0C and 760 mm Hg - this is not important
– It is found that 1 R = 0.00877 J/kg 0.01 J/kg – Most radiation meters at UNBC read in mR
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Activity vs. Exposure
• Activity: measured in Bq relates to nuclear disintegrations per second while Exposure: measured in Sievert relates quantitatively how much damage (biological effectiveness) is done to tissue, or air
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• The amount of energy deposited by radiation per unit mass IN TISSUE MATTER
• Gray (Gy)– 1 Gy = 1 J/kg
• Rad (radiation absorbed dose)– 1 rad = 0.01 J/kg
• Therefore:– 1 Gy = 100 rad
Absorbed Dose
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• As different types of radiation produce different amounts of damage
• Equivalent dose is the measure of the biological effect of radiation weighted for the type of radiation
• H = absorbed dose (Gy) weighting factor• Weighting factors (wR)
– Beta particles wR = 1– Gamma photons wR = 1– Alpha particles wR = 20
Equivalent Dose
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Radiation Quantities
2. Exposure
3. Absorbed Dose
4.Equivalent Dose
Air Matter (Tissue)
It is important to know the difference between the four term!
1. Activity
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Half-Life
• The half-life of a radionuclide is the time required for it to lose 50% of its activity by radioactive decay.
• Each radionuclide has its own unique half-life, regardless of the quantity or form:– Solid
– Liquid
– Gas
– Element or compound
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Half-Life
00.10.20.30.40.50.60.70.80.9
1
0 5 10 15
Elapsed Time (days)
Rela
tive A
ctiv
ity
Rn-222Half-life = 3.82 days
3.82
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Half-Life
• The half-life of a radioisotope is an unalterable property of the radioisotope.
• Half-lives range from microseconds to billions of years.
– Uranium-238 4.5 x 109 years
– Cesium-137 30.07 years
– Radon-222 3.8 days
– Polonium-212 3.04 x 10-7 seconds
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Half-Life Example• Assume we have 1000 Bq of P-32.
– P-32 has a half-life of 14.3 days.
# of half-lives elapsed Activity remaining
One half-life (14.3 days)
500 Bq
Two half-lives (28.6 days)
250 Bq
Three half-lives (42.9 days)
125 Bq
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Half-Life
• A good rule of thumb to remember is that after 7 half-lives the activity decreases to about 1% of the original value.
• After 10 half-lives the activity reduces to about 0.1% of the original value.
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Half-Life
• Activity and half-life are related mathematically by the following equation:
• A is the activity remaining after n half-lives– A0 is the original activity present
n0 2
1
A
A
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BIOLOGICAL EFFECTS
• Health Effects of Exposure to Radiation
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In This Session…
• Radiation dose
• Indirect effects of radiation
Direct effects of radiation– Hereditary effects– Somatic effects
• Stochastic effects• Deterministic effects
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Radiation Dose
• Radiation dose, in the simplest terms, can be thought of as the amount of radiation an individual is exposed to either from:
– Work activities with radioactive materials
– Medical tests such as from a diagnostic x-ray
– Background radiation
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Radiation Dose Measurement
• The measurement of an individual’s radiation dose is very complicated and depends on many factors:– Type of radiation– Type of exposure
• External• Internal
– Duration of exposure
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Radiation Dose
• When radiation passes through matter, it interacts with molecules and atoms giving up some or all of its energy
• The amount of energy transferred to the matter is referred to as the radiation dose
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Radiation Dose
• In living tissue, this energy transfer or radiation dose can result in damage to molecules and cells
• In radiation safety, there are three categories of radiation dose:– Absorbed dose
– Equivalent dose
– Effective dose
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Radiation Quantities
Exposure
Absorbed Dose
Equivalent Dose
Effective Dose
Air Matter (Tissue)
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Review- Absorbed Dose
• Absorbed dose is a measure of the amount of radiation energy transferred to matter per unit mass
• The unit of absorbed dose is the gray (Gy)
1 Gy = 1 J/kg
– Where J (joule) is a unit of energy
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Review- Equivalent Dose• The equivalent dose is simply the absorbed dose
multiplied by a radiation weighting factor• The radiation weighting factor helps to account for the
different levels of biological damage caused by different types of radiation
• Different types of radiation (alpha, beta, neutrons, gamma, x-rays) will, by their nature, cause different amounts of damage in living tissue
• The unit of equivalent dose is the millisievert (mSv)
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Radiation Weighting Factors
Radiation Energy wR
Gamma / x-ray All 1
Beta All 1
Alpha particles (internal) All 20
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Radiation Dose to Tissues
• We now know that different types of radiation cause different levels of damage in living tissue
• In addition, some tissues in the body are more sensitive to radiation than others
– Reproductive organs are more sensitive to radiation than the skin or the lungs
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Radiation Dose to Tissues
• The equivalent dose does not account for the varying sensitivities to radiation exposure of different organs or tissues in the body
• There is a need for a common scale with which to measure the overall risk to a person’s health, regardless of which tissue or organ is exposed
• This takes us to the effective dose
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Effective Dose
• The effective dose is the equivalent dose multiplied by a tissue weighting factor
• The tissue weighting factor helps to account for the varying sensitivities to radiation exposure of the different tissues and organs
• The unit of effective dose is the millisievert (mSv)
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Effective Dose
• Effective dose accounts for the type of radiation and the tissue or organ irradiated
• 1 mSv of effective dose is just 1 mSv, regardless of whether the dose was delivered to the lungs, thyroid, bone marrow, or any other tissue.– Unfortunately, mSv is the unit equivalent dose as
well as effective dose though they are not equal
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Equivalent v. Effective Doses
• Equivalent dose is the unit used to assess doses to individual tissues or extremities– Tissues are treated separately– There are equivalent dose limits for skin, hands and
feet
• Effective dose is the unit used to assess doses on the scale of the whole body– Tissue doses are weighted to indicate effect on the
body as a whole
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Molecular Effects of Irradiation
• In living systems, biological damage can occur as a result radiation-induced damage to molecules and cells
• Radiation may cause damage to molecules or cells either directly or indirectly
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• About 60% of human body weight is water.
• Water is a simple molecule consisting of one oxygen (O) and two hydrogen (H) atoms.
• Its chemical representation is: H2O.
H
O
H
Indirect Damage
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• Ionizing radiation can break apart water molecules to create free radicals.
• H2O H· + OH·
• Both hydrogen and oxygen normally exist as H2 and O2 molecules, respectively.
• Free radicals are chemically reactive atoms or molecules
Indirect Damage
H2O
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Indirect Damage• Indirect damage involves the effects of
reactive free radicals created by the interaction of radiation with water (H2O).
H2O
Ionization
Toxic H2O2
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Indirect Damage
• The fractured water molecule components, H and OH, can undergo a variety of reactions:
• H· + OH· H2O (Water)
– H· + H· H2 (Hydrogen gas)
– OH· + OH· H2O2 (Hydrogen peroxide)
– Hydrogen peroxide is a chemical poison. – Its effects resemble radiation sickness (nausea,
vomiting, diarrhoea, malaise).
H2O2
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Direct Damage• When radiation interacts directly with vital
biological molecules such as DNA (deoxyribonucleic acid), RNA (ribonucleic acid), proteins and enzymes, damage to these molecules can occur through ionization interactions and the absorption of energy
• These ionization and excitation interactions can literally break chemical bonds resulting in impaired molecular function
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Radiation Effect Categories
– Hereditary (genetic) effects
– Somatic (body) effects
• The effects of exposure to radiation can be divided into two categories:
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Hereditary Effects
• Hereditary effects are those which do not become apparent until future generations are born
• Possible result of radiation induced damage to the DNA molecule in the germ cells (sperm, ova).
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Hereditary Effects in Humans
• Effects from the nuclear bomb explosions in Japan:– Hereditary effects such as leukemia and
developmental delays have only been seen in those children who were heavily irradiated while still in their mother’s womb
– Children conceived after the explosion have shown no change in the natural mutation rate
• The findings are not statistically sound
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Somatic Effects
• Somatic effects are those which are experienced directly by the people exposed to the radiation
• There are two types of somatic effects:– Stochastic effects– Deterministic effects
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Stochastic Effects
• All we can say is that radiation exposure increases the likelihood of developing a disease such as cancer
• The greater the exposure, the greater the likelihood
• We can never be certain that an effect will occur
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DNA Damage
• When radiation interacts with living tissue, molecular bonds can be broken and cell function altered
• If a DNA molecule is damaged:– The body may be able repair the DNA,– The cell may die,
or– The DNA is not repaired properly resulting in a
mutated cell with altered function
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Mutation Effects
• A radiation dose has a certain probability of causing a mutation in a cell.
• A mutation might bring about cell destruction.• A mutation could affect cell behaviour and increase
the rate of cell divisions.– The new cells will have the mutation causing them
to also divide before reaching their mature state.– They will provide no beneficial function to the
body.
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Tumors
• These cells form a tissue called a tumour. – If the cells do not invade surrounding tissues,
the tumour is benign.– If the tumour invades neighbouring tissues it
is malignant.
• A malignant tumour is cancer which may or may not be fatal.
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Radiation-Induced Cancers• Early radiation scientists
– Many died from skin, bone, and blood cancers.• Radium watch dial painters
– Many died of bone cancer 8 to 40 years later.• UK X-ray patients
– 6,500 patients were treated with 3 Gy x-rays. – 30 developed leukemia (7 expected without x-rays).
• Japanese bomb survivors (80,000 people)– 350 cancer deaths, double the expected figure.
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Latency Period
• There is a delay between exposure to the radiation and the onset of cancer.
• This delay is known as the latency period. – For leukemia, it is about 8 years.– For other cancers, it can be much longer.
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Risk: Cancer from Radiation• The risk of developing a fatal cancer as a result of
exposure to radiation is thought to be approximately 4% per 1000 mSv
• Consider a person who worked for 50 years and received 20 mSv per year– This person’s total lifetime radiation dose would be
1000 mSv– This person could have an extra 4% chance of
developing a fatal cancer
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Risk: Cancer in General
• Note that 25% of all people develop a fatal cancer in their life
• So, this person’s risk of developing cancer becomes 29%, instead of 25%
• No profession is risk free
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Deterministic Effects
• A deterministic effect is one which will certainly result from exposure
• There will be a minimum exposure (threshold) above which the effect will occur
• The severity of the effect will depend on the exposure– Example: cataract formation, radiation sickness
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Chronic Exposure
• Exposure to low doses of radiation over months or years
• Deterministic effects– Cataracts– Nonspecific life shortening
• Stochastic effects– Cancer– Genetic effects
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Acute Exposure
• Exposure to a high dose delivered within seconds, minutes or days
• Possible deterministic effects– Blood changes– Nausea– Diarrhea– Hair-loss– Malaise– Death
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Acute EffectsAcute Dose (mSv) Probable Effects
100 None detectable. 250 Only detectable by
chromosome analysis. 500 Minor changes to blood cells.
1000 Possible radiation sickness and skin reddening. Very slight chance of death.
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Acute EffectsAcute Dose (mSv) Probable Effects
2500 Radiation sickness. Some
risk of death without medical treatment; recovery very likely with treatment.
4500 50% will die without medical treatment; some risk of death with treatment.
10,000 100% will die without medical treatment; high risk of death with treatment.
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Acute Exposure
• The rapidly reproducing cells are most affected by acute radiation:– The skin– The blood-forming tissues– The gonads– The digestive system lining (the
gastrointestinal tract or GI tract)
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• Acute Effects= deterministic effects– clear relationship between dose and effect
once threshold is crossed
• Delayed Effects= stochastic effects– dose increases probability of an effect,
rather than its magnitude or severity
Biological Effects
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Delayed Effects• The increased risk of a fatal cancer due to
exposure to radiation is 0.004% per mSv.• This is in addition to the 25% risk that all people
have of contracting a fatal cancer.• Thus, an exposure of 1 mSv increases a
person’s risk of dying of cancer from 25% to 25.004%.
• Note: The occupational exposure limit at UNBC is 1 mSv.
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Biological Effects – Summary
• Although the risk associated with working with radioisotopes and radiation is low, it is not zero.
• Each individual must decide for themselves if they are willing to accept this risk.
• If someone decides to accept this risk, they should practice ALARA– As Low As Reasonably Achievable
• Radiation safety depends primarily on the user.
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REGULATIONS
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Federal Regulations
• Canadian Nuclear Safety Commission (CNSC)– Nuclear Safety and Control Act
• Radiation Protection Regulations• General Nuclear Safety and Control Regulations• Nuclear Substances and Radiation Devices
Regulations• Packaging and Transport of Nuclear Substances
Regulations
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Federal Regulations
• Canadian Nuclear Safety Commission (CNSC)– Issues licenses to users that permit work with
radioactive materials– License conditions– Penalties for violation
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CNSC Dose Limits
Type of Dose
Members of the Public
(mSv/y)
Nuclear Energy Workers (mSv/y)
Effective Dose 1 20
Dose to the Lens of an Eye
15 150
Dose to the Skin 50 500 Dose to the Hands
and Feet 50 500
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UNBC Radiation Safety Program
• Radiation Safety Policy
• Committee on Radioisotopes and Radiation Safety
• Radiation Safety Officer
• Individual Users
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UNBC Radiation Safety Program
• Radiation Safety Policy– Applies to all teaching and research activities– Outlines responsibilities of:
• Committee on Radionuclides and Radiation Safety• Radiation Safety Officer• Deans, Directors and Department Chairs
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UNBC Radiation Safety Program
• Committee on Radioisotopes and Radiation Safety– Develop policies and procedures– Provide advice and make recommendations– Issue Internal Radioisotope Permits to faculty
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Internal Radioisotope Permits
• Allow specified radioisotopes to be used for particular purposes in certain locations
• Restrictions ensure (in part) compliance with CNSC licenses
• Each faculty member working with radioisotopes or radiation requires an IRP
• Non-compliance may result in IRP being revoked
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UNBC Radiation Safety Program
• Radiation Safety Officer– Reports to CRRS and VP Admin & Finance– Reviews IRP applications– Approve radioisotope orders– Maintain documents– Deliver radiation safety training– Conduct inspections
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UNBC Dose limit
The occupational exposure limit at UNBC is 1 mSv.
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UNBC Radiation Safety Program
• Individual users– Comply with safety policies and procedures– Seek guidance from immediate supervisor– Attend safety training or meetings– Immediately report accidents or hazardous conditions
to immediate supervisor
• Supervisors are also responsible for ensuring that students are adequately supervised and instructed in laboratory safety
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UNBC Policy for Pregnant Women
• The UNBC Committee on Radioisotopes and Radiation Safety recommends that the dose to the abdomen of a pregnant woman not exceed that of the general population
• Women are encouraged to disclose their pregnancy to their Department Head, in confidence, as early as possible
• Department Head will notify the worker’s Supervisor and the Radiation Safety Officer
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UNBC Policy for Pregnant Women
• The woman’s radiation work will be reviewed to determine if the dose rate can be reduced to near background levels
• If the dose rate cannot be reduced to about background, cessation of the work will likely be recommended
• Lab entry will be denied to any pregnant worker approaching her dose limit
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UNBC Policy for Pregnant Women
• A pregnant woman may indicate that she wants to continue with her radiation work by signing a form indicating she is aware of the potential risks but wishes to continue– this form is available from the RSO
• All actions regarding pregnant worker’s will be reviewed by the UNBC Committee on Radioisotopes and Radiation Hazards