Irradiation principles Flashcards
Various applications of irradiation:
What is the main purpose?
medical supplies foods cosmetics, sanitary products pharmaceuticals lab supplies waste
main purpose: STERILIZATION
Advantage of radiation sterilization vs conventional methods:
more energy efficient (don't need heating/cooling) faster don't need to be heat stable no added chemicals produce remains in "fresh" state
Canada is the largest supplier of ______, but the process is not approved in Canada so there are no commercial facilities.
irradiation equipment
True/False: there is no irradiated food or products available in Canada
False; imported goods (some approved)
industrial, government, university facilities exist
2 types of irradiation technologies:
man-made radio isotopes
electron accelerators
advantages of electron accelerators:
lower cost
easier to operate
What are labelling requirements for irradiated food?
if >10% ingredients have been irradiated, must display international irradiated symbol
1 Gray = ___ rad
100
What ranged of radiation dose is lethal to humans?
10^2 - 10^3 rad
True/False: the level of radiation needed to inhibit sprouting, kill insects, and sterilize is not high enough to harm humans
False!
Purposes of irradiation in food:
sterilize
kill insects/eggs
inhibit sprouting
overall increase shelf life
If the level of irradiation is below _____, it is not necessary to declare it. Is this lower radiation level still useful?
below 1 kGy
Can kill some microbes (pathogens)
but not enough to kill insects, or sterilize
Instrument used for measuring amount of radiation:
What is it based on?
dosimeter
radiation based on a aqueous chemical
Gamma rays interact mainly with: _____ to produce:_____. What is the consequence of this?
water molecules; make hydroxyl + free radicals
react with O2 to make more free radicals
cause chain reaction (react with proteins, carbs, fats)
Types of radiation:
microwaves gamma rays infrared solar x-rays nuclear
the visible spectrum is what range?
400-700nm
large wavelength means (high/low) frequency
low
high energy rays will have ___ wavelengths and ___ frequencies. What are examples of high energy waves?
short; high
gamma rays, x rays
gamma rays and x rays are classified as:
Why?
ionizing rays
can knock off electron upon contact, makes an ion
units for frequency, wavelength, and energy?
frequency: v (cycles/s)
wavelength: lambda (cm)
energy: E (eV)
Which types of radiation are used for irradiating food?
gamma rays, x rays (ionizing)
What are the forms of radiation waves and how are they produced?
alpha rays, beta rays, gamma rays
come from radioactive source + strong magnetic field
How do the types of radiation waves differ?
alpha: weak penetration, low energy, +
beta: medium penetration, medium energy, -
gamma: high penetration, high energy, neutral
What types of material are sufficient to stop the different radiation wave types?
alpha: sheet of paper
beta: aluminum
gamma: thick lead
Beta rays are essentially a stream of: ____. Do they have practical use in irradiation?
high velocity electrons
yes; but need to accelerate (cyclotron or linear accelerator) to acquire enough energy to be useful
radiation applications in the 1920s-1940s:
medical, treat cancer, x-ray tube
radiation applications in 1940s-50s:
medical research, radiology equipment, diagnosis
radiation applications in 1950s-60s:
Cobalt 60, Cesium 138, medical/dental applications, non-food sterilization
radiation applications in 1960s-70s:
food research applications, industrial irradiators, other industrial applications (ex: polymer cross-linking)
Radiation applications in 70s-80s-current:
small + large scale, wide applications, approved for food
When was radiation first used for sterilization?
1950s-60s (non-food)
When was radiation first used for food?
1960s-70s (research began)
the primary source for gamma rays is: ____, which is an isotope of ____.
cobalt 60
cobalt 59
a secondary source for gamma rays is: _____. Where is it sourced from?
Cesium 137
spent fuel from nuclear reactors (from uranium)
What is a CANDU reactor?
Canada Deuterium Uranium reactor
pressurized heavy water reactor for generating power
Cobalt 60 is formed by:
adding neutron to Cobalt 59
what is the principle behind how ionization through radiation occurs?
The Compton effect: high energy gamma ray -> hits electron -> leaves as low energy ray
electron is rebounded, leaves atom -> creates ion
What happens after all the radioactive energy is spent?
Return to ground state (no longer radioactive)
Co60 becomes Ni60
Cs137 becomes Ba137
Co60 has a greater ____ than Cs137.
Cs137 has a greater ____ than Co60.
activity
lifespan (half-life)
The parts of a CANDU process:
slug element pencil module source rack
describe a radiation facility:
heavily insulated room with radiation source
automatic controls bring food in -> irradiated -> out
when personnel need to enter, radiation source is lowered below ground in insulated, water-filled chamber
Why is a conveyor system essential to food irradiation?
prevent humans from entering radioactive zone
Radiation is described in terms of:
Dose: amount of radiation given/absorbed
intensity: rate at which dose is given
Units for dose and intensity:
Dose: Rad or Gray (1Gy = 1J/kg)
Intensity: Curie (3.7*10^10 disintegration/s)
How do radioisotopes differ from conventional energy sources?
constant; can’t turn off
radioactive decay - intensity decreases with time
Rate of decay is proportional to
intensity
what is the half-life?
time needed for intensity to be decreased by 50%
