Radiation Physicist Interview Questions And Answers

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

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.

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.

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.

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.

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.

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.

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

Effective dose is a calculated quantity developed by the ICRP (1991) for purposes of radiation protection. The effective dose is assumed to be related to the risk of a radiation-induced cancer or a severe hereditary effect. It takes into account: the absorbed doses that will be delivered to the separate organs or tissues of the body during the lifetime of an individual due to intakes of radioactive materials; the absorbed doses due to irradiation by external sources; the relative effectiveness of different radiation types in inducing cancers or severe hereditary effects; the susceptibility of individual organs to develop a radiation-related cancer or severe hereditary effect; considerations of the relative importance of fatal and non-fatal effects; and, the average years of life lost from a fatal health effect. (HPS 005-3) Thus, the effective dose is a quantity calculated by multiplying the equivalent dose received by every significantly irradiated tissue in the body by a respective tissue weighting factor (this factor reflects the risk of radiation-induced cancer to that tissue) and summing together the individual tissue results to obtain the effective dose. Such a dose, in theory, carries with it the same risk of cancer as would an equal equivalent dose delivered uniformly to the whole body.

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.

Emergency Planning Zone (EPZ) is the area surrounding a nuclear power plant for which plans required by the NRC have been made in advance to ensure that prompt and effective actions are taken to protect the health and safety of the public in case of an incident. There is a plume exposure pathway EPZ which extends about 10 miles in radius around a plant. Its primary concern is the exposure of the public to, and the inhalation of, airborne radioactive contamination. The ingestion pathway EPZ extends about 50 miles in radius around a plant. Its primary concern is the ingestion of food and liquid that is contaminated by radioactivity.

High-level radioactive waste: the radioactive material resulting from spent nuclear fuel reprocessing. This can include liquid waste directly produced in reprocessing or any solid material derived from the liquid waste having a sufficient concentration of fission . Other radioactive materials can be designated as high-level waste if they require permanent isolation. This determination is made by the U.S. Nuclear Regulatory Commission on the basis of criteria established in U.S. law.

Demonstrates a patient-centered approach to developing treatment plans.

Alpha particle (Animation) the nucleus of a helium atom, made up of two neutrons and two protons with a charge of +2. Certain radioactive nuclei emit alpha particles. Alpha particles generally carry more energy than gamma rays or beta particles, and deposit that energy very quickly while passing through tissue. Alpha particles can be stopped by a thin layer of light material, such as a sheet of paper, and cannot penetrate the outer, dead layer of skin (Illustration). Therefore, they do not damage living tissue when outside the body. When alpha-emitting atoms are inhaled or swallowed, however, they are especially damaging because they transfer relatively large amounts of ionizing energy to living cells.

Cesium-137 (Cs-137) has a half-life of 30.17 years and decays by beta and gamma radiation. Cs-137 is produced by nuclear fission for use in medical devices and gauges and is one of the byproducts of nuclear fission processes in nuclear reactors and nuclear weapons testing. Small quantities of Cs-137 can be found in the environment from nuclear weapons tests that occurred in the 1950s and 1960s and from nuclear reactor accidents, such as the Chernobyl power plant accident in 1986, which distributed Cs-137 to many countries in Europe. (HHS/CDC)