RADIATION

Radiation is an energy in the form

of electro-magnetic waves or

particulate matter, traveling in the

air.”

• 1895 - Wilhem Conrad Roentgen discovered X-rays

and in 1901 he received the first Nobel Prize for

physics.

• 1903 - Marie Curie and Pierre Curie, along with

Henri Becquerel were awarded the Nobel Prize in

physics for their contributions to understanding

radioactivity, including the properties of uranium.

• 1942 - Enrico Fermi and others started the first

sustained nuclear chain reaction in a laboratory

beneath the University of Chicago football stadium.

• 1945 – Nuclear bombs dropped on Japan.

HISTORY

RADIATION SOURCES

Sources of radiation can be divided

into two categories:

Natural Background Radiation

Man-Made Radiation

NATURAL BACKGROUND RADIATION

Cosmic Radiation

Terrestrial Radiation

Internal Radiation

COSMIC RADIATION

The earth, and all living things on it, are

constantly bombarded by radiation from

outer space

Charged particles from the sun and stars interact with

the earth’s atmosphere and magnetic field to produce

a shower of radiation.

The amount of cosmic radiation varies in different

parts of the world due to differences in elevation and

to the effects of the earth’s magnetic field.

35 mrad / yr normal altitude

Jet pilots – 300 mrad / yr

ATMOSPHERIC RADIATION

Terrestrial

Radioactive material is also found throughout

nature in soil, water, and vegetation.

Important radioactive elements include uranium,

thorium, radium & isotopes of potassium(K40)

Some radioactive material is ingested with food and

water.

The amount of terrestrial radiation aprox. 50 mrad/yr

Atmospheric

Gases like Radon & thorum – 2 mrad/yr

INTERNAL RADIATION

People are exposed to radiation from radioactive

material inside their bodies. Besides radon, the most

important internal radioactive element is naturally

occurring potassium-40. Others - uranium, thorium,

strontium & carbon.

25 mrad / yr.

May go up to 70 or 80.

Total natural radiation - 0.1 rad / yr.

MAN-MADE RADIATION SOURCES

Examples of man-made sources of radiation to members of the public:

Lantern mantles

Medical diagnosis

Building materials

Nuclear power plants

Coal power plants

Tobacco

Phosphate fertilizers

T V sets

Radium watches

ANNUAL AVERAGE DOSE (MREM/YEAR)

MAN-MADE SOURCE

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20

30

40

50

60

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NUCLEAR FALL OUT

Fallout is the residual radioactive material

propelled into the upper atmosphere following

a nuclear blast

Carbon C14 , iodine I131, cescium Cs137 &

strontium Sc90

The Chernobyl disaster was a nuclear reactor

accident in the Chernobyl Nuclear Power Plant in

the Soviet Union on 26 April 1986.

RADIATION

Ionizing Radiation

Higher energy electromagnetic waves (gamma) or heavy

particles (beta and alpha).

High enough energy to pull electron from orbit.

Non-ionizing Radiation

Lower energy electromagnetic waves.

Not enough energy to pull electron from orbit, but can

excite the electron.

ELECTROMAGNETIC SPECTRUM

10-14

10-12

10-10

10-8

10-6

10-4

10-2

1 102

104

106

108

Wavelength in Meters

1010

108

106

104

102

1 10-2

10-4

10-6

10-8

10-10

10-12

10-14

Broadcast

Short waveTV

FM

RadarInfrared

Near Far

Visible

Ultraviolet

X Rays

Gamma Rays

Cosmic Rays Power

Transmission

Ionizing Radiation Nonionizing Radiation

Energy - Electron VoltsHigh Low

NON-IONIZING RADIATION

Definition:

“ They are electromagnetic waves incapable of

producing ions while passing through matter,

due to their lower energy.”

Sources• Ultraviolet light

• Visible light

• Infrared radiation

• Microwaves

• Radio & TV

• Power transmission

NONIONIZING EXAMPLES

• Ultraviolet – Black light – induce

fluorescence in some materials

• Vision – very small portion that animals

use to process visual information

• Heat – infrared – a little beyond the red

spectrum

• Radio waves – beyond infrared

• Micro waves

• Electrical power transmission – 60

cycles per second with a wave length of

1 to 2 million meters.

IONIZING RADIATION

IONIZING RADIATION

Definition

“ It is a type of radiation that is able to disrupt

atoms and molecules on which they pass

through, giving rise to ions and free radicals”.

Sources – x-rays, radioactive material

produce alpha, beta, and gamma

radiation, cosmic rays from the sun and

space.

IONIZING RADIATION

Paper Wood Concrete

Alpha

Beta

Gamma

Energy

Low

Medium

High

RADIOACTIVE MATERIAL

Either natural or created in nuclear

reactor or accelerator

Radioactive material is unstable and

emits energy in order to return to a more

stable state (particles or gamma-rays)

Half-life – time for radioactive material to

decay by one-half

ALPHA PARTICLES

Two neutrons and two protons

Charge of +2

Emitted from nucleus of radioactive atoms

Transfer energy in very short distances (10

cm in air)

Shielded by paper or layer of skin

Primary hazard from internal exposure

Alpha emitters can accumulate in tissue

(bone, kidney, liver, lung, spleen) causing

local damage

BETA PARTICLES

Small electrically charged particles

similar to electrons

Charge of -1

Ejected from nuclei of radioactive atoms

Emitted with various kinetic energies

Shielded by wood, body penetration 0.2

to 1.3 cm depending on energy

Can cause skin burns or be an internal

hazard of ingested

GAMMA-RAYS

Electromagnetic photons or radiation

(identical to x-rays except for source)

Emitted from nucleus of radioactive

atoms – spontaneous emission

Emitted with kinetic energy related to

radioactive source

Highly penetrating – extensive shielding

required

Serious external radiation hazard

X-RAYS

Overlap with gamma-rays

Electromagnetic photons or radiation

Produced when electrons strike a target material inside and x-ray tube

Emitted with various energies & wavelengths

Highly penetrating – extensive shielding required

External radiation hazard

RADIATION UNITS

Exposure: Roentgen 1 Roentgen (R) = amount of X or gamma radiation that produces ionization resulting in 1 electrostatic unit of charge in 1 cm3 of dry air.

Absorbed Dose: rad (Roentgen absorbed dose) = absorption of 100 ergs of energy from any radiation in 1 gram of any material; 1 Gray (Gy) = 100 rads = 1 Joule/kg; Exposure to 1 Roentgen approximates 0.9 rad in air.

Biologically Equivalent Dose: Rem (Roentgen equivalent man) = dose in rads x QF, where QF = quality factor. 1 Sievert (Sv) = 100 rems.

SI Unit for radiation exposure

Coulombs/kilogram (C/Kg)

1 Roentgen = 2.58 X 10^-4 C/Kg

SI unit for absorbed dose

Gray (Gy)

1 Gy =100 Rad

SI Unit for activity

Becquerel (Bq) = 1 disintegration/ second

Curie (Ci) = 3.7 X 10^10 disintegrations/ second

BIOLOGICAL EFFECTS

ACUTE EFFECTS

0-25 No observable effect.

25-50 Minor temporary blood changes.

50-100 Possible nausea and vomiting and

reduced WBC.

150-300 Increased severity of above and

diarrhea, malaise, loss of appetite.

300-500 Increased severity of above and

hemorrhaging, depilation. Death may

occur

> 500 Symptoms appear immediately, then

death has to occur.

Delayed Somatic Effects: Delayed effects to exposed person include: Cancer, leukemia, cataracts, life shortening from organ failure, and abortion. Probability of an effect is proportional to dose (no threshold). Severity is independent of dose. Doubling dose for cancer is approximately 10-100 rems.

Genetic Effects: Genetic effects to off-spring of exposed persons are irreversible and nearly always harmful. Doubling dose for mutation rate is approximately 50-80 rems. (Spontaneous mutation rate is approx. 10-100 mutations per million population per generation.)

DOSE RESPONSE TISSUE

Examples of tissue Sensitivity

Very High White blood cells (bone marrow)

Intestinal epithelium

Reproductive cells

High Optic lens epithelium

Esophageal epithelium

Mucous membranes

Medium Brain – Glial cells

Lung, kidney, liver, thyroid,

pancreatic epithelium

Low Mature red blood cells

Muscle cells

Mature bone and cartilage

ORGAN SPECIFIC

Skin

Erythema – desquamation (reversible)

Hair loss

Mucous Membranes

Fibrin Plaquing

Urinary and Bladder Changes

Visceral Changes (secretory)

Reproductive Organs

Irreversible damage to gametes

Sterility

Bone

Suppress osteoblast activity

Decrease number of osteocytes

• Permissible dose from man made < 5 rad/yr

• X- ray greatest hazard – 4 rad in one minute

STANDARDS

RADIATION PROTECTION

TimeReduce the spent near the source of radiation.

DistanceIncrease the distance from the source of radiation.

ShieldingPlace shielding material between you and the

source of radiation.

REDUCING EXPOSURE

MONITORING

Personal Dosimeters: Provide a record of

accumulated exposure for an individual worker

over extended periods of time and are small

enough for measuring localized exposures

Common types: Film badges; pocket dosimeters, &

Thermoluminescence detectors (TLD);

Direct Reading Survey Meters and Counters: Useful in identifying source of exposures and in evaluating potential sources, such as surface or sample contamination, source leakage, inadequate decontamination procedures, background radiation.

Common types:

Alpha Proportional or Scintillation counters Beta, gamma Geiger-Mueller or

Proportional countersX-ray, Gamma Ionization chambers Neutrons Proportional counters

Continuous Monitors: Continuous direct reading

ionization detectors (same detectors as above) can

provide read-out and/or alarm to monitor

hazardous locations and alert workers to leakage,

thereby preventing exposures.

Long-Term Samplers: Used to measure average

exposures over a longer time period. For example,

charcoal canisters or electrets are set out for days

to months to measure radon in basements (should

be <4 pCi/L).