Nuclear
Radioactivity and Energy
09/13/2010
Planets, air, water, rocks, living organisms - everything in the universe is made up of atoms, nature's building blocks. Atoms all contain the same particles but in varying amounts, and this is what determines their properties and level of radioactivity. Presentation of a natural phenomenon.
Aoms, Nuclei, and Isotopes - One Big Family
Each atom is made up of:
• A nucleus, made up of protons and neutrons (protons are particles that carry a positive electrical charge, neutrons carry a neutral charge).
• Electrons moving at high speed around the nucleus.
It is the number of protons that gives the atom its chemical properties and determines to which chemical element it belongs. For example, atoms with 53 protons are all iodine atoms, while those with 92 protons are uranium atoms.
Two atoms with the same number of protons but different numbers of neutrons are called isotopes. Their chemical properties are identical but their physical properties are different.
To differentiate between isotopes, the sum of its protons and neutrons are attached to the name of the element. For example, uranium 235 contains 92 protons and 143 neutrons
(235 = 92 + 143) and uranium 238 contains 92 protons and 146 neutrons (238 = 92 + 146).
Some isotopes are stable, i.e. they remain identical indefinitely. However some isotopes are unstable and to achieve stability, they gradually disintegrate by emitting one or more particles and therefore energy in the form of radiation. This is what is known as radioactivity.
As the atoms disintegrate, the radioactivity of an element diminishes - this is what is known as radioactive decay. The time at which radioactivity has reduced by half is called its half-life. Each element has its own half-life, which varies from a few fractions of a second to billions of years.
Some examples:
• Oxygen 15: 2 minutes
• Iodine 131: 8 days
• Carbon 14: 5,730 years
• Uranium 238: 4.5 billion years
A natural phenomenon
We live and have always lived in a naturally radioactive environment - this is known as natural radioactivity. Everything in the universe is made up of a small proportion of radioactive atoms - even our bodies have low levels of radioactivity. Over two-thirds of the radioactivity to which we are exposed every year is of natural origin.
Natural radioactivity varies according to:
• The nature of the geological surroundings: radioactive material has been present on earth since it was formed. Granite regions naturally have higher radioactivity.
• Altitude: the higher the altitude, the greater the exposure to cosmic radiation.
A wide variety of different and well-established applications
Radioactivity has many applications in everyday life:
• To produce energy (in nuclear power plants)
• For medical purposes - to treat sick people (radiotherapy) or to carry out medical examinations (e.g. MRI scanning)
• In archaeology, to date ruins
• And for industrial purposes (for measuring, preserving food, etc.).
This is what is known as artificial radioactivity. 28% of all human exposure to ionizing radiation is due to medical examinations and treatments.
The effects of radioactivity on the human body depend on the dose of radiation received.
Our bodies, which themselves have low levels of radioactivity, can take in small quantities of additional radioactivity without any harmful effects - this is what happens every time we travel by plane or stay at high altitudes. Large doses can be harmful to health, cause sickness, and long-term, serious or even fatal illness depending on the intensity of the radiation absorbed, its area of impact and the length of exposure.
• Alpha radiation, formed from particles containing 2 protons and
2 neutrons with a range in the air of a few centimeters. These particles can be stopped using just a sheet of paper.
• Beta radiation, formed from electrons, which has a range in the air of a few meters. It can be stopped by aluminum foil, a pane of glass or a plank of wood.
• Gamma radiation, or electromagnetic radiation, which is highly penetrating (it can travel several hundred meters in the air). It is the same type as X-rays and can only be stopped by very thick walls of lead or concrete.
