Absorbed dose: The quantity of ionizing radiation deposited into a material, including an organ or tissue, expressed in the terms of the energy absorbed per unit mass of material. The basic unit of absorbed dose is the rad or its SI equivalent, the gray (Gy).
Activity (Radioactivity): The rate of decay of a radionuclide, more formally, the number of decays per time. Its SI unit is the Becquerel (Bq) corresponding to one radioactive decay (disintegration) per second; its old unit, the curie (Ci), was originally defined as the activity of 1 gram of radium-226 or 3.7 x 10/10 disintegrations per second.
Acute dose: An acute dose means a person received a radiation dose over a short period of time. Example: 5,000mrem per hour.
Acute effect: Effects in organisms manifest themselves soon after exposure to radiation and are characterized by inflammation, edema, denudation and depletion of tissue, and hemorrhage.
Acute radiation exposure: A radiation exposure that occurs over a relatively short period of time ( less than 24 hours ).
Acute Radiation Syndrome-“ARS” (Radiation Sickness): A person exposed to radiation will develop ARS only if the radiation dose was very high, penetrating (gamma rays), encompassing the whole body and received in a short period of time.
Agreement State: States that assumed authority under Section 274b of the Atomic Energy Act to license and regulate by-product materials (radioisotopes), source materials (uranium and thorium), and certain quantities of special nuclear materials.
Air Cargo Only label: Two labels on opposite sides of the gauge case and next to the Yellow ll labels that instruct that gauge scan only be shipped on cargo aircraft – no passenger aircraft.
ALARA: “As Low As Reasonably Achievable” – Taking every reasonable safeguard to protect person and public against ionizing radiation exposure.
Alpha particle: A heavy particle emitted form the nucleus of an atom. It consists of two protons and two neutrons, which is identical to the nucleus of a helium atom without electrons. These heavy charged particles lose their energy very quickly in matter. They are easily shielded by clothing, a sheet of paper or the top layer of skin. Alpha particles are only hazardous when ingested. Alpha particles emitted by the radioactive materials in the gauge are permanently shielded and therefore not used in the operation of the gauge.
Americium-241 (Am241): Portable nuclear gauges use a radioactive isotope of Americium, Am241, coupled with beryllium to produce neutron radiation for measuring hydrogen/moisture content.
Atom: The smallest particle of an element that can enter into a chemical reaction.
Atomic Mass: The weight of an atom measured in atomic mass units, typically protons and neutrons.
Atomic Number: The number of protons in the nucleus of an atom and the number of electrons in a neutral atom. This number determines the atom’s chemical element.
Atomic Weight: The mass of an atom. Mass is roughly determined by counting the number of protons and neutrons in the nucleus.