Irradiation principles

Question 1

Various applications of irradiation:

What is the main purpose?

Answer 1

medical supplies
foods
cosmetics, sanitary products
pharmaceuticals
lab supplies
waste

main purpose: STERILIZATION

Question 2

Advantage of radiation sterilization vs conventional methods:

Answer 2

more energy efficient (don't need heating/cooling)
faster
don't need to be heat stable
no added chemicals
produce remains in "fresh" state

Question 3

Canada is the largest supplier of ______, but the process is not approved in Canada so there are no commercial facilities.

Answer 3

irradiation equipment

Question 4

True/False: there is no irradiated food or products available in Canada

Answer 4

False; imported goods (some approved)

industrial, government, university facilities exist

Question 5

2 types of irradiation technologies:

Answer 5

man-made radio isotopes

electron accelerators

Question 6

advantages of electron accelerators:

Answer 6

lower cost

easier to operate

Question 7

What are labelling requirements for irradiated food?

Answer 7

if >10% ingredients have been irradiated, must display international irradiated symbol

Question 8

1 Gray = ___ rad

Answer 8

100

Question 9

What ranged of radiation dose is lethal to humans?

Answer 9

10^2 - 10^3 rad

Question 10

True/False: the level of radiation needed to inhibit sprouting, kill insects, and sterilize is not high enough to harm humans

Answer 10

False!

Question 11

Purposes of irradiation in food:

Answer 11

sterilize
kill insects/eggs
inhibit sprouting
overall increase shelf life

Question 12

If the level of irradiation is below _____, it is not necessary to declare it. Is this lower radiation level still useful?

Answer 12

below 1 kGy
Can kill some microbes (pathogens)
but not enough to kill insects, or sterilize

Question 13

Instrument used for measuring amount of radiation:

What is it based on?

Answer 13

dosimeter

radiation based on a aqueous chemical

Question 14

Gamma rays interact mainly with: _____ to produce:_____. What is the consequence of this?

Answer 14

water molecules; make hydroxyl + free radicals

react with O2 to make more free radicals
cause chain reaction (react with proteins, carbs, fats)

Question 15

Types of radiation:

Answer 15

microwaves
gamma rays
infrared
solar
x-rays 
nuclear

Question 16

the visible spectrum is what range?

Answer 16

400-700nm

Question 17

large wavelength means (high/low) frequency

Answer 17

low

Question 18

high energy rays will have ___ wavelengths and ___ frequencies. What are examples of high energy waves?

Answer 18

short; high

gamma rays, x rays

Question 19

gamma rays and x rays are classified as:

Why?

Answer 19

ionizing rays

can knock off electron upon contact, makes an ion

Question 20

units for frequency, wavelength, and energy?

Answer 20

frequency: v (cycles/s)
wavelength: lambda (cm)
energy: E (eV)

Question 21

Which types of radiation are used for irradiating food?

Answer 21

gamma rays, x rays (ionizing)

Question 22

What are the forms of radiation waves and how are they produced?

Answer 22

alpha rays, beta rays, gamma rays

come from radioactive source + strong magnetic field

Question 23

How do the types of radiation waves differ?

Answer 23

alpha: weak penetration, low energy, +
beta: medium penetration, medium energy, -
gamma: high penetration, high energy, neutral

Question 24

What types of material are sufficient to stop the different radiation wave types?

Answer 24

alpha: sheet of paper
beta: aluminum
gamma: thick lead

Question 25

Beta rays are essentially a stream of: ____. Do they have practical use in irradiation?

Answer 25

high velocity electrons | yes; but need to accelerate (cyclotron or linear accelerator) to acquire enough energy to be useful

Question 26

radiation applications in the 1920s-1940s:

Answer 26

medical, treat cancer, x-ray tube

Question 27

radiation applications in 1940s-50s:

Answer 27

medical research, radiology equipment, diagnosis

Question 28

radiation applications in 1950s-60s:

Answer 28

Cobalt 60, Cesium 138, medical/dental applications, non-food sterilization

Question 29

radiation applications in 1960s-70s:

Answer 29

food research applications, industrial irradiators, other industrial applications (ex: polymer cross-linking)

Question 30

Radiation applications in 70s-80s-current:

Answer 30

small + large scale, wide applications, approved for food

Question 31

When was radiation first used for sterilization?

Answer 31

1950s-60s (non-food)

Question 32

When was radiation first used for food?

Answer 32

1960s-70s (research began)

Question 33

the primary source for gamma rays is: ____, which is an isotope of ____.

Answer 33

cobalt 60 | cobalt 59

Question 34

a secondary source for gamma rays is: _____. Where is it sourced from?

Answer 34

Cesium 137 | spent fuel from nuclear reactors (from uranium)

Question 35

What is a CANDU reactor?

Answer 35

Canada Deuterium Uranium reactor | pressurized heavy water reactor for generating power

Question 36

Cobalt 60 is formed by:

Answer 36

adding neutron to Cobalt 59

Question 37

what is the principle behind how ionization through radiation occurs?

Answer 37

The Compton effect: high energy gamma ray -> hits electron -> leaves as low energy ray electron is rebounded, leaves atom -> creates ion

Question 38

What happens after all the radioactive energy is spent?

Answer 38

Return to ground state (no longer radioactive) Co60 becomes Ni60 Cs137 becomes Ba137

Question 39

Co60 has a greater ____ than Cs137. | Cs137 has a greater ____ than Co60.

Answer 39

activity | lifespan (half-life)

Question 40

The parts of a CANDU process:

Answer 40

``` slug element pencil module source rack ```

Question 41

describe a radiation facility:

Answer 41

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

Question 42

Why is a conveyor system essential to food irradiation?

Answer 42

prevent humans from entering radioactive zone

Question 43

Radiation is described in terms of:

Answer 43

Dose: amount of radiation given/absorbed intensity: rate at which dose is given

Question 44

Units for dose and intensity:

Answer 44

Dose: Rad or Gray (1Gy = 1J/kg) Intensity: Curie (3.7*10^10 disintegration/s)

Question 45

How do radioisotopes differ from conventional energy sources?

Answer 45

constant; can't turn off | radioactive decay - intensity decreases with time

Question 46

Rate of decay is proportional to

Answer 46

intensity

Question 47

what is the half-life?

Answer 47

time needed for intensity to be decreased by 50%