ASNT IRRSP flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Inverse square law

For a point source, dose rate or intensity changes inversely with the square of distance; doubling distance reduces the rate to one quarter of its original value.

Half-value layer

The thickness of a specified material that reduces the intensity of a radiation beam to half its original value; it equals 0.693 divided by the linear attenuation coefficient.

Roentgen definition

The roentgen is a unit of gamma or X-ray exposure in air; one roentgen equals 2.58 times ten to the minus four coulombs per kilogram of air.

Compton scattering

A photon interaction in which the photon transfers part of its energy to an outer-shell electron and is scattered at a longer wavelength; it dominates at industrial radiography energies in low atomic number materials.

Curie and becquerel

One curie equals 3.7 times ten to the tenth disintegrations per second, and one becquerel equals one disintegration per second; thus one curie equals 37 billion becquerels.

Photoelectric absorption

A photon interaction in which the photon is completely absorbed and ejects a bound electron; it is most important at low photon energies and in high atomic number shielding materials.

ALARA principle

ALARA means keeping radiation doses as low as reasonably achievable, considering economic and social factors, by using time, distance, shielding, and good work practices.

Stochastic radiation effect

A radiation effect whose probability increases with dose but whose severity does not depend on dose; cancer and heritable effects are considered stochastic, with no assumed threshold.

Deterministic radiation effect

A radiation effect that has a threshold dose and whose severity increases as dose increases; examples include skin burns, cataracts, and acute radiation syndrome.

Occupational dose limit

Under U.S. NRC rules, a radiation worker's total effective dose equivalent limit is 5 rem per year, with separate limits for lens, skin, and extremities.

Pregnant worker limit

A declared pregnant radiation worker may not receive more than 0.5 rem total effective dose equivalent to the embryo or fetus during the entire gestation period under NRC rules.

Acute radiation syndrome

A set of clinical effects occurring after a large acute whole-body dose, typically above about 100 rad; bone marrow, gastrointestinal, and cardiovascular syndromes appear as dose increases.

Geiger-Muller detector

A gas-filled detector that produces large pulses from ionizing events, making it very sensitive for low-level radiation; however, it can saturate in high radiation fields and has energy-dependent response.

Ionization chamber survey meter

An instrument that measures radiation dose rate by collecting charge produced in a gas-filled chamber; energy-compensated models are used for accurate gamma dose-rate surveys in radiography.

Thermoluminescent dosimeter

A personal dosimeter that stores radiation energy in a crystalline material and releases light when heated; the light output is proportional to the accumulated dose received.

Survey meter check source

A small radioactive source used to verify that a survey meter responds and is functioning before use; the reading should be compared with the expected value and battery check.

Pocket alarm dosimeter

A small electronic device worn by radiography personnel that sounds an alarm when a preset radiation dose or dose rate is exceeded, providing immediate warning of unexpected exposure.

Gamma radiography source

A sealed radioactive source, commonly iridium-192 or cobalt-60, used in a shielded exposure device; it emits gamma rays for radiographic imaging when driven into a guide tube.

Exposure device lock

A locking mechanism on a gamma radiography exposure device that secures the sealed source in its shielded position and must be locked when not in use.

Collimator function

A shielded device placed at the end of a guide tube that restricts the radiation beam to the area of interest, reducing scatter and unnecessary dose to surrounding personnel and areas.

Source decay formula

Activity after time t equals initial activity multiplied by e raised to the negative decay constant times t; the decay constant equals 0.693 divided by the isotope half-life.

Geometric unsharpness

Image blur caused by source size, object-to-film distance, and source-to-object distance; it increases with larger focal spot or greater object-to-film distance and decreases with larger source-to-object distance.

Industrial radiography license

A specific NRC or agreement-state license is required to possess and use radioactive sources for industrial radiography; it specifies authorized sources, personnel, equipment, and operating conditions.

Sealed source leak test

A wipe test of a sealed radiography source is performed at intervals not exceeding six months to detect removable radioactive contamination; results above the regulatory limit require removing the source from service.

Radiation area posting

A radiation area is an area where a person could receive 5 millirem in one hour at 30 centimeters from the source or surface; it must be posted with a caution sign.

High radiation area

An area where a person could receive 100 millirem in one hour at 30 centimeters from the source or surface; it requires posting and controls to prevent unauthorized entry.

DOT Type A package

A packaging designed to withstand normal transport conditions and used for limited quantities of radioactive material; shipping papers, labels, and marking must meet Department of Transportation requirements.

Source fails to retract

If a gamma source does not return to its shielded position, stop work, secure the area, survey dose rates, use remote handling tools if needed, and notify the radiation safety officer immediately.

Lost radioactive source

If a radiography source is lost or stolen, immediately secure the area, notify the licensee and radiation safety officer, and report to regulatory authorities as required; do not handle it bare-handed.

Emergency radiography kit

A kit should contain a calibrated survey meter, personal dosimeters, remote handling tools, lead shielding, warning signs, barrier tape, and communication equipment for source emergencies.

Dose reduction methods

Radiation dose can be reduced by limiting time near the source, increasing distance using the inverse square law, and placing appropriate shielding between the source and personnel.

Fire involving radiography source

Evacuate personnel, account for the source, inform firefighters of the radiation hazard, establish a perimeter, and survey the area after the fire is controlled before reentry.