Radiation Physicist

Absorbed dose (Animation) the amount of energy deposited by ionizing radiation in a unit mass of tissue. It is expressed in units of joule per kilogram (J/kg), and called “Gray” (Gy).

Air kerma the initial kinetic energy of the primary ionizing particles (photoelectrons, Compton electrons, positron/negatron pairs from photon radiation, and scattered nuclei from fast neutrons) produced by the interaction of the incident uncharged radiation in a small volume of air, when it is irradiated by an x-ray beam. Unit of measure is Gray.

Shows interpersonal skills and the ability to work and collaborate with others.

Beta particles (Animation) (Image) electrons ejected from the nucleus of a decaying atom. Although they can be stopped by a thin sheet of aluminum, beta particles can penetrate the dead skin layer, potentially causing burns. They can pose a serious direct or external radiation threat and can be lethal depending on the amount received. They also pose a serious internal radiation threat if beta-emitting atoms are ingested or inhaled.

External irradiation occurs when all or part of the body is exposed to penetrating radiation from an external source. During exposure, this radiation can be absorbed by the body or it can pass completely through. A similar thing occurs during an ordinary chest x-ray. Following external exposure, an individual is not radioactive and can be treated like any other patient. Gamma or photon radiation exposure from a terrorist nuclear event or radiation dispersal device would make the victim at risk for Acute Radiation Syndrome, depending on the dose received.

Contamination, Fixed skin contamination is that which remains after bathing or attempted decontamination. Contamination is assumed to be removed by natural processes within 336 hours (14 days) after deposition on the skin.

The new international system (SI) unit of radiation dose, expressed as absorbed energy per unit mass of tissue. The SI unit "Gray" has replaced the older "rad" designation. (1 Gy = 1 joule/kilogram = 100 rad). Gray can be used for any type of radiation (e.g., alpha, beta, neutron, gamma), but it does not describe the biological effects of different radiations. Biological effects of radiation are measured in units of "Sievert" (or the older designation "rem"). Sievert is calculated as follows: Gray multiplied by the "radiation weighting factor" (also known as the "quality factor") associated with a specific type of radiation.

Low-level waste (LLW) radioactively contaminated industrial or research waste, such as paper, rags, plastic bags, medical waste, and water-treatment residues. It is waste that does not meet the criteria for any of three other categories of radioactive waste: spent nuclear fuel and high-level radioactive waste; transuranic radioactive waste; or uranium mill tailings. Its categorization does not depend on the level of radioactivity it contains.

Deterministic effect an effect that can be related directly to the radiation dose received. The severity increases as the dose increases. A deterministic effect typically has a threshold below which the effect will not occur.

Fallout, nuclear minute particles of radioactive debris that descend slowly from the atmosphere after a nuclear explosion. For more information

Dirty bomb is a device designed to spread radioactive material by conventional explosives when the bomb explodes. A dirty bomb kills or injures people through the initial blast of the conventional explosive and spreads radioactive contamination over possibly a large area—hence the term “dirty.” Such bombs could be miniature devices or large truck bombs. A dirty bomb is much simpler to make than a true nuclear weapon.

Coulomb the international system (SI) unit of electric charge. A coulomb is the quantity of charge passing a cross section of conductor in one second when the current is one ampere.

Chain reaction a process that initiates its own repetition. In a fission chain reaction, a fissile nucleus absorbs a neutron and fissions (splits) spontaneously, releasing additional neutrons. These, in turn, can be absorbed by other fissile nuclei, releasing still more neutrons. A fission chain reaction is self-sustaining when the number of neutrons released in a given time equals or exceeds the number of neutrons lost by absorption in non-fissile material or by escape from the system.

Becquerel (Bq) (Animation) the amount of a radioactive material that will undergo one decay (disintegration) per second. For more information

Acute exposure an exposure to radiation that occurred in a matter of minutes rather than in longer, continuing exposure over a period of time.

Absolute risk the proportion of a population expected to get a disease over a specified time period.

Air burst a nuclear weapon explosion that is high enough in the air to keep the fireball from touching the ground. Because the fireball does not reach the ground and does not pick up any surface material, the radioactivity in the fallout from an air burst is relatively insignificant compared with a surface burst.

Cobalt (Co) a gray, hard, magnetic, and somewhat malleable metal. Cobalt is relatively rare and generally obtained as a byproduct of the production of other metals, such as copper. Its most common radioisotope, cobalt-60 (Co-60), is used in radiography and medical applications. Co-60 emits beta particles and gamma rays during radioactive decay.

Decay products (or daughter products) are the isotopes or elements formed and the particles and high-energy electromagnetic radiation emitted by the nuclei of radionuclides during radioactive decay. Also known as "decay chain products" or "progeny" (the isotopes and elements). A decay product may be either radioactive or stable.