What is Radiation?

Radiation is in every part of our lives. It occurs naturally in the earth and can reach us through cosmic rays from outer space. Radiation may also occur naturally in the water we drink or the soils in our backyard. It even exists in food, building materials, and in our own human bodies.

Radiation is used for scientific purposes, medical reasons, and to power some submarines. We can also come into contact with radiation through sources such as X-rays, nuclear power plants, and smoke detectors.

This page covers three aspects of radiation:

2. Sources of Radiation and How It is Measured

3. Radiation Protection Concepts

RadiationTerms

Radiation can be defined as:

energy given off by the nucleus of an atom in the form of particles or rays.

Radiation is the same whether it happens in atoms that are made by nature or in atoms that scientists make.

The atom is the smallest unit that shows the chemical behavior characteristics of an element. The center of each atom has a nucleus that contains protons and neutrons. Protons are positively charged particles. Neutrons, which have no electrical charge, hold the protons together. Electrons are negatively charged particles. The electrons surround the nucleus and travel in orbits.

There is a theory called The Rutherford-Bohr Theory of atomic structure. It compares the atom to our solar system. At the center of every atom is the positively charged nucleus, which could be compared to the sun in our solar system. The electrons move around the nucleus as if in orbit. Just like the earth orbits around the sun.

Repelling forces exist between the nuclear particles. Any change in the number, position, or energy of the nucleons can upset their balance. If this happens, the nucleus becomes unstable or radioactive.

Remember the Periodic Table of the Elements?

An element is a member of a category of atoms that all have the same number of protons. Each element is represented by an atomic number on the Periodic Table. The atomic mass of an element is generally the combined mass of protons and neutrons.

Sources of Radiation

There are different types of radiation; some are more energetic than others. For example, non-ionizing radiation, has enough energy to move atoms around, but not enough to change them chemically. The most energetic form of radiation is called ionizing radiation. EPA's Radiation Protection Programs are concerned with protecting people and the environment from potentially harmful exposures to ionizing radiation.

We measure radiation dose in units called rem. Scientists estimate that the average person in the United States receives a dose of about 360 millirem of radiation per year. But what are the sources of that exposure: where does it come from?

Eighty percent of human exposure comes from natural sources: radon gas, the human body, outer space, and rocks and soil. The remaining twenty percent comes from man-made radiation sources, primarily medical X-rays.

Radiation Protection Concepts

So, now that you have a basic understanding of radiation sources how do you protect yourself? There are three concepts in basic radiation protection. They are

time	distance	shielding

time

If you decrease the amount of time you spend near the source of radiation, you will decrease the amount of radiation exposure you receive. To imagine this, think of a trip to the beach as a comparison. For instance, if you spend a lot of time on the beach, you will be exposed to the sun, and, ultimately, get a sunburn. If you spend less time in the sun and more time in the shade, your sunburn will be much less severe. This is similar to the way radiation exposure works.

The farther away you are from a radiation source, the less exposure you will receive. Compare this to an outdoor concert. You can sit directly in front of a speaker, 50 yards from the stage, or on the grass in the park across the street. If you sit in front of the speaker, you will probably suffer some damage to your hearing. If you sit 50 yards from the stage, you will be exposed to an average amount of music. If you sit in the park across the street, the noise is even further reduced and you might not even hear the concert, or even know what song they are playing.

Radiation exposure is similar. The closer you are to the source, the greater your chances for developing some damage to your body. If you are far from the source, your exposure would be much lower.

If you increase the shielding around a radiation source, it will decrease your exposure. For example, if you stand out in the rain without an umbrella, you will get wet. But, if you use an umbrella to shield you from the rain, you will remain dry and protected. This is similar to the idea of shielding in radiation protection.