Ionizing Radiation

What is ionizing radiation?

Ionizing radiation is high-energy radiation capable of producing ionization in substances through which it passes.

What are the types of ionizing radiation?

Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus. They are a highly ionizing form of particle radiation, and have low penetration depth so they can be blocked with a single sheet of paper. Alpha particles pose a serious threat when ingested, but not when encountered externally.

Beta particles are high-energy, high-speed electrons or positrons. When passing through matter, a beta particle is decelerated by electromagnetic interactions and may give off bremsstrahlung x-rays. Because of this, beta particles are best shielded with low-density materials like acrylic plastic.

Gamma rays are electromagnetic radiation of high frequency and therefore high energy. They have no mass, and no charge. Gamma rays are identical to x-rays, except that an x-ray originates from orbital electron rearrangements, while gamma rays originate from the nucleus of an atom during decay. Gamma and x-rays are best shielded with lead, or other dense materials.

Neutron particles are slightly larger than protons. Due to the high kinetic energy of neutrons, this radiation is considered to be the most severe and dangerous radiation to the whole body when exposed to external radiation sources. Neutrons readily pass through most material, but interact enough to cause biological damage. The most effective shielding materials when dealing with Neutron radiation are water, polyethylene, or paraffin wax.

Where is ionizing radiation encountered?

Ionizing radiation is both naturally occurring as well as man-made. The primary source of natural background radiation is radon. Radon is an odorless, colorless, tasteless gas that is the product of the decay of uranium and thorium. Exposure to high concentrations of radon has been linked to lung cancer. Ionizing radiation can also be found naturally in rocks, soil, and in cosmic rays from our solar system.

Man-made forms of ionizing radiation come from medical sources such as diagnostic x-rays and nuclear medicine treatments. It also comes from consumer product sources such as building materials, televisions, smoke detectors, combustible fuels, and tobacco. The nuclear fuel cycle, nuclear weapons testing, and nuclear reactor accidents also cause a level of exposure.


How is ionizing radiation dangerous?

Ionizing radiation has enough energy to damage the DNA in a cell. Exposure to this type of radiation can be very destructive to living tissue, and can result in mutation, radiation sickness, cancer, and death.

How is ionizing radiation measured?

Ionizing radiation can be monitored using film, thermoluminescent dosimeters, or electronic devices.

Radiation Detection Company measures radiation exposure using thermoluminescent dosimeters. These dosimeters contain four separate phosphors. The badges are read with control values that are subtracted from the personnel badges. An algorithm then selects the correct energy the badge was exposed to in order to apply the appropriate dose.

What is a Leak Test?

Licensees who use sealed sources must have the source tested periodically for leakage. The wipe of a sealed source must be performed using a leak test kit. The sample must be analyzed for radioactive contamination. The analysis must be performed by a person approved by the NRC or an Agreement State.

What is Occupational Dose?

The internal and external dose of ionizing radiation received by workers in the course of employment. 

What is a Radiation Source Sheet and why is it important that I complete one?

RDC’s customers are best served when we understand the sources around which you work.  A completed Radiation Source Sheet helps us determine the accurate response of our dosimeters.  An improperly exposed badge can be more easily identified and errors can corrected by making minor adjustments that ensure the most accurate dose readings possible.


Radiation Source Sheets are also used to calculate dose from our ring dosimeters.  A ring dosimeter contains one phosphor, unlike our typical TLD badge, which contains four separate phosphors and filtration that can discriminate different energies.  This makes it impossible to automatically determine what type of radiation a ring has been exposed and this discrimination of energies is what determines the type of radiation to which the badge has been exposed.   


During the setup of your account, a review of your sources allows us to set the type of radiation the ring will be exposed to. This insures the proper correction values are applied during the calculation process. While we can report dose from our ring dosimeters without the proper correction factors, the readings may not be as accurate.