Transcript RAD GRAD COURSE

Radiation Concepts
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
Radiation
Radioactive Atom
Ionizing Radiation
Alpha Particle
Neutron Particle
Beta Particle
Gamma Ray (X Ray)
Radioactive Material
Gamma Ray
Gamma Ray
Radioactive Material - any material containing
atoms that emit radiation.
Contamination
External Radiation
Contamination
Radioactive Contamination
Radioactive Contamination - is radioactive material
in an unwanted place.
Ionizing Radiation
Neutrons
and Protons
Ejected Electron
Ionization Radiation
Ionizing Radiation - radiation with enough energy
to remove an electron from its atom.
Alpha Particle a
Characteristics
Range
Shielding
Hazards
Sources
• +2 charge
• 2 protons
• 2 neutrons
• Large mass
• Very short
range
• 1" -2" in air
• Paper
• Outer layer
of skin
• Internal
• Plutonium
• Uranium
• Radium
• Thorium
• Americium
a
a
a
a
a
Beta Particle b
Characteristics Range
Shielding
Hazards
Sources
• -1 charge
• Small mass
• Plastic
safety
glasses
• Thin
metal
• Skin and
eyes
• Can be
internal
• Radioisotopes
• Activation
Products
• Sealed
sources
• Short range
• About 10'
in air
Gamma Ray g
Characteristics Range
Shielding
Hazards
Sources
• No charge
• No mass
• Similar
to x-rays
• Lead
• Steel
• Concrete
• External
(whole body)
• Can be
internal
• X-ray
machines
• Electron
microscopes
• Sealed
sources
• Accelerators
• Nuclear
reactors
• Radioisotopes
• Long range
• About 1100'
in air
Paper Plastic Lead
Neutron Particle h
Characteristics Range
Shielding
Hazards
Sources
• No charge
• Found in
nucleus
• Water
• Plastic
• External
(whole body)
• Fission
• Reactor
operation
• Sealed
sources
• Accelerators
• Extended
range
Paper Lead
Water
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
Radioactivity Units
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)
2 of
Radioactive contamination measures an amount
activity over a unit of surface area.
e.g. 5000 dpm/100 cm2
Prefixes Used with Radiation Units
Prefix Symbol
Translation
Numerical Value
Scientific Notation
Tera
T
1 trillion
1,000,000,000,000
1012
Giga
G
1 billion
1,000,000,000
109
Mega
M
1 million
1,000,000
106
Kilo
k
1 thousand
1,000
103
Milli
m
1 thousandth
1/1,000
10-3
Micro
m
1 millionth
1/1,000,000
10-6
Nano
n
1 billionth
1/1,000,000,000
10-9
Pico
p
1 trillionth 1/1,000,000,000,000
10-12
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)
millirem
Abbreviation:
mrem
1000 mrem = 1 rem
millirem - is the basic unit of radiation dose
equivalent. It measures biological risk in humans.
Half-Life
The time required for the
amount of radioactive material
to decrease by one-half
1200
1000
800
Activity 600
400
200
0
New
1 HalfLife
2 Half- 3 HalfLives Lives
4 HalfLives
Acute Radiation Dose
Acute radiation dose refers
to persons who receive
large amounts of
radiation over a
short period of time.
Chronic Radiation Dose
Chronic radiation dose refers to
persons who receive small amounts
of radiation over a long period of time.
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.
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.
Four Ways Radioactive
Material Can Enter the Body
Inhalation
• Breathing
• Smoking
Absorption
Wound or Cut
Ingestion
• Eating
• Drinking
• Chewing
Biological Effects of Radiation
Cells are
undamaged.
Cells are damaged,
repair damage and operate normally.
Cells are damaged,
repair damage and operate abnormally.
Cells die as a
result of damage.
Health Effects
• Radiation effects on cell chromosomes:
Somatic Effects
observed in the exposed individual
Heritable (Genetic) Effects
observed in future generations of
exposed individual
RW I Affecting
Factors
Biological Damage
•
•
•
•
•
•
Total radiation dose
Dose rate
Type of radiation
Area of body exposed
Cell sensitivity
Individual sensitivity
102-13
The RW
fetus
is MORE
I
sensitive than an adult.
No Heritable Effects from Ionizing Radiation
Have Been Observed in Humans
Heritable effects have been observed in laboratory animals.
The average annual dose to the general
population from natural background
and man-made sources is 360 mrem.
Terrestrial Sources
Radon
Cosmic Radiation
Radon
Internal Sources
Other
Average Annual Dose
Cosmic
28 mrem
Terrestrial
28 mrem
Radon
200 mrem
Internal
40 mrem
Medical X-Rays
40 mrem
Nuclear Medicine
14 mrem
Natural Sources
Man-Made Sources
Other
3 mrem
Consumer Products
10 mrem
Comparison of Radiation Dose
1 10
Lethal Dose
Radiation
Worker Limit
Argonne
Control Limit
Natural
Background
Average ANL
Radiation W orker
General
Employee Limit
Chest X-Ray
100
1,000
10,000
100,000
1,000,000
Relative
risk of dying:
RW I
1 in a million odds.
• 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)
Risk – Loss of Life Expectancy
Days of Average Life Expectancy
Lost Due to Various Causes
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
3500
2250
1600
1100
777
365
227
207
60
10
6
Basic Protective Measures
Time
Distance
Shielding