What is Radiation?

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What is Radiation?

• Radioactivity is a natural and spontaneous process by which

the unstable atoms of an element emit or radiate excess

energy

• Radiation is the result

• Alpha Decay - Alpha decay occurs when the nucleus spontaneously ejects an ά particle. An ά particle is really 2 protons and 2 neutrons, or an Helium nucleus.

Alpha Decay of a Uranium-238 Nucleus

Parent Nucleus

U23892

DecayEvent Daughter

Nucleus

Emitted Particle

Th23490

He42

KeyProtonNeutron

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Decay Products

• Beta Decay - An excess of neutrons in an atom's nucleus will make it unstable, and a neutron is converted into a proton to change this ratio. During this process, a ß particle is released,

• Gamma ray emission usually occurs with ά and ß emission. Gamma rays have no charge or mass, so their emission doesn't change the chemical composition of the atom. Instead, it results in a loss of radiant energy. Gamma ray emission occurs because the nucleus is often unstable after ά and ß decay.

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Decay Product Penetration

Ionizing radiation Energy in the form of waves or particles that has enough force to remove electrons from atoms.

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Energy Spectrum

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Sources of Radiation

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Cosmic8% Terrestrial

8%

Internal11%

Radon55%

Other1%

Medical14%

ConsumerProducts

3%

Man Made Radiation Sources – 18%• Medical X Rays• Nuclear Medicine• Consumer Products• Other

Natural Radiation Sources – 82%• Radon• Internal• Terrestrial• Cosmic

Data is U.S. Based

National Council on Radiation Protection and Measurements (NCRP) Report No. 93, “Ionizing Radiation Exposure of the Population of the United States, “ 1987

•Geiger counter–Senses extremely

tiny electrical impulses caused

by radiation

How to Detect Radiation

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We Protect Ourselves from Radiation Exposure by:

Reducing Exposure

TIME

Increasing

DISTANCE

SHIELDING

Beneficial Uses of Radiation

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IonizingX-RayCT Scan – Computer

TomographyNuclear Medicine

Non-IonizingUltrasoundMRI – Magnetic Resonance

Imaging

Medical Procedures

Museums and archeologists rely on radiation detection to verify the authenticity or age of art objects or archeological finds.

Beneficial Uses of Radiation

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•Smoke detectors – rely on a tiny radioactive source to sound an alarm when smoke is present

•Food sterilization and preservation

Beneficial Uses of Radiation

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• Living cells and tissue are made of molecules composed of atoms united by chemical bonds• Composition of these atoms and how they bond determines the physical structure (shape) of molecules.• It is the shape of these large molecules (proteins, nucleic acids, lipids, and carbohydrates) which determines how the molecules function• Ionizing energy is powerful enough to alter the structure of atoms or molecules, the bonds involved, and greatly affect the function of the molecules in the cell and living tissue.• Altering the shape of molecules in a somatic cell can change the behavior of that cell.•Altering the shape of molecules (especially DNA) in germ cells (egg or sperm) can greatly effect the offspring of the organism.

Structure and Function of Living Cells

Molecules of living cells:

Proteins: Large molecule• Structural Component of the cell.• Function as Enzymes to controlMetabolic reactions.• Important component of the cellmembrane• How the atoms are connected to each causes folding of proteins into 3-D molecule.• This folding of proteins enhances and supports their function within the cell.

Nucleic Acids: Also a large molecule

• Double Helix shape with hydrogen

bonding of the nitrogen bases in the

center.• Contains the genetic material of

the cell -- the cells’ instructional sheet.• Responsible for the production

of proteins at the ribosomes -- by

being blueprint of how to build them.

Effect Of Radiation on Structure of DNA

Direct Or Indirect Action

• Direct Action - when ionized energy strikes a molecule, DNA directly• Indirect Action - strikes another molecule such as water -- a “free radical” is produced• Free Radicals react strongly to restore their stable configuration which could create other free radicals within the cell.

Living Cells Options after Irradiation