Radiation Basics

Radiation

What is Radiation?

Radiation is the transfer of energy from one place to another by means of particles or waves.

Two Basic Types of radiation

(1) Ionizing
(2) Non-Ionizing

Ionizing radiation is radiation with enough kinetic energy so that during an interaction with an atom, it can remove tightly bound electrons from their orbits, causing the atom to become charged or Ionized. Some examples of ionizing radiation include alpha, beta, and gamma radiation.

Non-ionizing radiation, therefore, is radiation that does not ionize the atoms around it. Some examples of non-ionizing radiation include sunlight, microwaves, radio-waves, and visible light waves.

When most people talk about radiation, they are talking about ionizing radiation. This type of radiation is sometimes referred to as nuclear radiation. Atoms that are capable of giving off ionizing radiation are called radioactive.

The four most common forms of ionizing radiation are alpha, beta, gamma, and neutron radiation. The have the following characteristics:

consists of two neutrons and two protons (the equivalent of a helium nucleus)
has a +2 charge
largest and most massive of the four described
can be shielded by a few inches of air

emitted electron (with either a + or - charge)
smallest of the particles listed
moderate energy betas can be shielded by several inches of plastic

electromagnetic wave
has no mass
high energy gammas can penetrate several feet of lead

particle
no electrical charge
high energy neutrons can penetrate thick lead shields

Detecting ionizing radiation: Ionizing radiation cannot be detected by the human senses. Therefore, we detect Ionizing radiation by using special tools or instruments.

Geiger counters
film badges
thermo-luminescent detectors
electroscopes

Radioactivity:

The spontaneous emission of "fragments" or "bundles" of energy from unstable nuclei creating more stable nuclei.

Unstable atoms try to release energy to "fall" to a lower and more stable energy state. They give off energy by emitting electrons (beta particles), clusters of 2 protons and 2 neutrons (alpha particles), gamma and x-rays (electromagnetic waves), and neutrons.

Our environment is naturally radioactive:

There are many natural sources of radiation. Many common elements have naturally occurring radioactive isotopes ( an isotope is an element with the same number of protons, but different numbers of neutrons; e.g. carbon-12 [6 protons and 6 neutrons] and carbon-14 [6 protons and 8 neutrons]). Some of the most common sources of natural radiation are:

cosmic rays from outer space
materials in the earthÕs crust (radioactive elements in the rocks and soils)
radon gas (decays from natural uranium within the soil)
people (yes carbon-14 and potassium-40 are naturally present in human-beings)

Average U.S. citizen exposures The average U.S. citizen is exposed to the above forms of radiation as well as x-rays, technological sources, etc. Citizens are exposed to approximately 360 mrem per year.

ICRP Data on Health Effects of Ionizing Radiation

                                                mSv             mREM
Typical Annual Background Dose                   1               100
Dose in Areas of High natural Background        10              1000
Lowest Single Dose for Health Effects          200             20000
Approx. Single Dose for Radiation Sickness    1000            100000
Single Dose for Which Survival is Unlikely   10000           1000000

ICRP Recommended Dose Limit per year for Exposures above natural background:

Public                           Occupational
1mSv                             5mSv
100mREM                          500mREM