Radiation ConceptsRadiation Concepts

DefinitionsDefinitions

101-04

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

Ionizing Radiation

RadiationRadiation

Alpha Particle

Neutron Particle

Beta Particle

Radioactive Atom

Gamma Ray (X Ray)

Radioactive Material - any material containing atoms that emit radiation.

Radioactive MaterialRadioactive Material

Gamma Ray

Gamma Ray

ContaminationContamination

Contamination

External Radiation

Radioactive Contamination - is radioactive material in an unwanted place.

Radioactive ContaminationRadioactive Contamination

Ionizing Radiation - radiation with enough energy to remove an electron from its atom.

Ionizing RadiationIonizing Radiation

Ionization Radiation

Ejected ElectronNeutrons

and Protons

Characteristics

• +2 charge• 2 protons• 2 neutrons• Large mass

Alpha Particle Alpha Particle

Range

• Very short range• 1" -2" in air

Shielding

• Paper• Outer layer of skin

Hazards

• Internal

Sources

• Plutonium• Uranium• Radium• Thorium• Americium

Characteristics

• -1 charge• Small mass

Beta Particle Beta Particle

Range

• Short range• About 10' in air

Shielding

• Plastic safety glasses• Thin metal

Hazards

• Skin and eyes• Can be internal

Sources

• Radioisotopes• Activation Products• Sealed sources

Characteristics

• No charge• No mass• Similar to x-rays

Gamma Ray Gamma Ray

Range

• Long range• About 1100' in air

Hazards

• External (whole body)• Can be internal

Sources

• X-ray machines• Electron microscopes• Sealed sources• Accelerators• Nuclear reactors• Radioisotopes

Shielding

• Lead• Steel• Concrete

Paper Plastic Lead

Characteristics

• No charge• Found in nucleus

Neutron Particle Neutron Particle

Range

• Extended range

Shielding

• Water• Plastic

Hazards

• External (whole body)

Sources

• Fission• Reactor operation• Sealed sources• Accelerators

Paper Lead Water

Radiation UnitsRadiation 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 UnitsRadioactivity 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)

Radioactive contamination measures an amount of activity over a unit of surface area. e.g. 5000 dpm/100 cm2

2

Prefixes Used with Radiation UnitsPrefixes 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 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 – ExamplesPrefixes – 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 (Ci) source

10 nCi/100 cm2 = low level radioactive contamination

Natural radium content of soil = 1 picoCi/gram (pCi/g)

millirem - is the basic unit of radiation dose equivalent. It measures biological risk in humans.

Abbreviation:mrem

1000 mrem = 1 rem

milliremmillirem

Half-LifeHalf-Life

0

200

400

600

800

1000

1200

New 1 Half-Life

2 Half-Lives

3 Half-Lives

4 Half-Lives

Activity

The time required for theamount of radioactive materialto decrease by one-half

Acute Radiation DoseAcute Radiation Dose

Acute radiation dose refers to persons who receive large amounts of radiation over a short period of time.

Chronic Radiation DoseChronic 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.

Chronic radiation dose refers to persons who receive small amounts of radiation over a long period of time.

Chronic Radiation DoseChronic Radiation Dose

The previous statements assume a Linear,No-Threshold (LNT) response to radiation.

There is a growing body of scientific evidencethat this assumption is incorrect, and that lowlevels of radiation exposure are not harmful.

There is also evidence that low levels of radiation exposure can have a beneficial(i.e., hormesis) effect.

LNT AssumptionLNT Assumption

Inhalation• Breathing• Smoking

Four Ways Radioactive Material Can Enter the Body

Four Ways Radioactive Material Can Enter the Body

Wound or Cut

Absorption

Ingestion• Eating• Drinking• Chewing

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.

Biological Effects of RadiationBiological Effects of Radiation

Health EffectsHealth Effects

• Radiation effects on cell chromosomes:

Somatic Effects observed in the exposed individual

Heritable (Genetic) Effects observed in future generations of exposed individual

RW IFactors Affecting Biological DamageFactors Affecting Biological Damage

102-13

• Total radiation dose• Dose rate• Type of radiation• Area of body exposed• Cell sensitivity• Individual sensitivity

RW IThe fetus is MORE sensitive than an adult.

The fetus is MORE sensitive than an adult.

No Heritable Effects from Ionizing RadiationHave Been Observed in Humans

No Heritable Effects from Ionizing RadiationHave 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.

The average annual dose to the general population from natural background and man-made sources is 360 mrem.

Terrestrial Sources Cosmic Radiation

Internal Sources

Other

Radon

Radon

Average Annual DoseAverage Annual Dose

Cosmic28 mrem

Terrestrial28 mrem

Internal40 mrem

Medical X-Rays40 mrem

Nuclear Medicine14 mrem

Consumer Products10 mrem

Other3 mrem

Radon200 mrem

Natural SourcesMan-Made Sources

Comparison of Radiation DoseComparison of Radiation Dose

Lethal Dose

RadiationWorker Limit

ArgonneControl Limit

NaturalBackground

Average ANLRadiation Worker

GeneralEmployee Limit

Chest X-Ray

110 100 1,000 10,000 100,000 1,000,000

RW IRelative risk of dying:1 in a million odds.

Relative risk of dying: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 ExpectancyRisk – Loss of Life Expectancy

Days of Average Life Expectancy Lost Due to Various Causes

350022501600110077736522720760106

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 workerDriving a motor vehicle All industries Radiation: 100 mrem/yr x 70 years Coffee

Time

Basic Protective MeasuresBasic Protective Measures

Distance

Shielding