Module 1 - Review of Basic Radiation Concepts

Radiation

- It is energy that is emitted or transferred in the

form of electromagnetic waves or energetic,

high-speed particles

- It is a propagation of energy through matter or

space

- It is produced by releasing energy of unstable

atoms to become stable or accelerators at

high voltage

- Particulate Radiation

- Electromagnetic Radiation

Forms of Radiation

Particulate Radiation

- It consists of fast-moving subatomic particles with mass and energy

- It is produced by the disintegration of an unstable atom

Alpha particles

-Consists of two protons and two neutrons

(nuclei of Helium atoms) in close

association

-Possess net positive charge

-Emitted during decay of heavy, naturally

occurring radionuclides

Beta Particles

-Small and fast-moving, and more

penetrating than an alpha particle

-Produced only in or near the nucleus of

the atom

Negatron

a negatively charged electron, produced by nuclear disintegration

Positron

A positively charged electron, produced by pair production

Electrons

-Small, negatively charged particles that

can be accelerated to high energy to a

speed close to that of light

Protons

-Positively charged particles and are

relatively massive (2,000 times greater

than an electron)

Neutrons

-Produced if a charged particle is

accelerated to high energy and then

made to impinge on a suitable target

material

-Emitted as a by-product if heavy

radioactive atoms undergo fission

Electromagnetic Radiation

- It is produced by electric and magnetic

disturbances in space that travel in vacuum

with the velocity of light, resulting in a wave-

like motion

- It is known to be massless, and behaves

both as a wave or as a particle (wave-particle

duality)

- Non-ionizing Radiation

- Ionizing Radiation

2 types of Electromagnetic Radiation:

Non-ionizing Radiation

-Found at the long wavelength end of the

electromagnetic spectrum, and may have

enough energy to excite molecules and

atoms

-Cannot ionize matter because its energy

is lower than the ionization potential of

matter

Ionizing Radiation

-Has more energy than non-ionizing

radiation, enough to cause chemical

changes by breaking chemical bonds

-Can ionize matter directly or indirectly

because its energy exceeds the

ionization potential of matter

- Natural-occurring (background) radiation

- Man-made (artificial) radiation

Sources of Radiation

Natural-occurring (background) radiation

- Low levels of ionizing radiation that naturally occur from the surroundings

- As per the United Nations Scientific

Committee on the Effects of Atomic

Radiation (UNSCEAR), terrestrial radiation,

inhalation, ingestion, and cosmic radiation

are the four foremost sources of public

exposure to natural radiation

Man-made (artificial) radiation

- Levels of radiation as a product of human

innovation and activities

- These include nuclear power plants,

accelerators, radionuclide production

facilities, nuclear bombs, medical radiation,

and consumer items

Terrestrial radiation, Inhalation, Ingestion, and Cosmic radiation

Four foremost sources of public exposure to natural radiation acc. to UNSCEAR:

Nuclear power plants, accelerators, radionuclide production facilities, nuclear bombs, medical radiation, and consumer items

Man-made (artificial) radiation examples (6):

- Occupational Exposure

- Medical Exposure

- Public Exposure

Classification of Human Exposure to Radiation:

Occupational Exposure

Obtained as a result of the nature of their work

Medical Exposure

Intentional radiation exposure for diagnostic and therapeutic purposes

Public Exposure

- exposure which might be received from neither work or a medical procedure

- Irradiation

- Contamination

Modes of Human Exposure to Radiation:

Irradiation

A general term that may be used to describe exposure to radiation from any sources

1. External Exposure

2. Internal Exposure

Types of Irradiation:

External Exposure

Indicates that the exposure is due from an external source

Internal Exposure

It may result from inhalation, ingestion or, in some cases, from direct absorption through skin

Contamination

- Undesired presence of radioactive materials

or sources on any substance in

concentrations greater than those which

occur naturally

Activity

- It is the number of radionuclides

disintegrating per second

- It accounts for the "amount of radiation" in a

container

1.Conventional = Curie (Ci)

2.SI = Becquerel (Bq)

Activity (units)

Absorbed Dose

It accounts for the amount of energy deposited in a mass

1.Conventional = rad

2.SI = J/kg

3.Special name = Gray (Gy)

Absorbed Dose (units)

Equivalent Dose

It accounts for the biological effects for different types of radiation

1.Conventional = rem

2.SI = Sievert (Sv)

Equivalent Dose (units)

Radiation Weighting Factor

- It is a dimensionless variable, providing an estimate of relative human hazard from different types of radiation energies

Effective Dose

It measures the biological effects of a particular type of radiation on organs or tissues

1.Conventional = rem

2.SI = Sievert (Sv)

Effective Dose (units)

Tissue Weighting Factor

- It is a dimensionless variable used to

account for the different sensitivities of

different organs and tissues