ABSNM RP key terms

The amount of radiation energy deposited per unit mass of material, measured in gray (joule per kilogram). It describes energy uptake at a point, not the biological harm caused.

A dose quantity that weights absorbed dose by the radiation type's relative biological effectiveness, giving a common scale for different radiations. Measured in sievert; used for individual tissue doses.

A whole-body dose quantity combining equivalent doses to all tissues using tissue weighting factors, expressing overall stochastic risk. Measured in sievert and used for dose limits and comparisons.

The SI unit of absorbed dose, equal to one joule of radiation energy deposited per kilogram of material. Replaces the older unit rad, where one gray equals 100 rad.

The SI unit of equivalent and effective dose, reflecting biological effect rather than raw energy deposition. One sievert equals 100 rem; typical occupational doses are a small fraction of it.

A dimensionless multiplier applied to absorbed dose to account for how damaging a given radiation type is. Photons and electrons are 1; alpha particles and neutrons are much higher.

A multiplier reflecting a tissue's relative contribution to overall stochastic radiation risk when irradiated. Values sum to about one across the body and are used to compute effective dose.

The sum of effective doses received by all members of an exposed population, expressed in person-sievert. Used to compare overall societal impact of practices, not to predict individual harm.

The total dose expected to accrue in a person over 50 years following an intake of radioactive material. Integrates ongoing irradiation from retained radionuclides after inhalation or ingestion.

An older operational quantity combining absorbed dose with quality factors at a point in tissue, often measured by personal dosimeters. Largely superseded by modern protection quantities but still appears in practice.

The principle of keeping radiation doses as low as reasonably achievable, economic and social factors considered. Requires optimization of protection rather than merely meeting limits.

The protection principle requiring that any practice producing radiation exposure yield more benefit than harm. New practices or uses should not be adopted unless they produce a net positive outcome.

The protection principle of adjusting protection measures to achieve the best balance of dose reduction and cost. Implemented through ALARA programmes and dose constraints rather than fixed limits.

A prospective restriction on individual dose from a single source, set below the regulatory limit to guide optimization. It is not a legal limit but a planning value for protection.

The maximum legally permitted effective or equivalent dose to a defined group, such as workers or the public. Limits apply to the sum of relevant exposures and are not a target to approach.

Radiation exposure incurred by workers as a result of their work, subject to specific dose limits and monitoring requirements. Excludes exposures excluded or exempted by regulation.

Exposure of members of the public to radiation from regulated practices, excluding occupational and medical exposures. Subject to stricter dose limits than workers.

Radiation exposure of patients as part of diagnosis or treatment, plus voluntary carers and research subjects. Governed by justification and optimization rather than fixed dose limits.

A worker designated by the employer as liable to receive doses above a set fraction of a dose limit, requiring formal monitoring and health surveillance. Status triggers stricter recordkeeping and controls.

A device worn by an individual to measure accumulated radiation dose over a wearing period. Common types include film badges, thermoluminescent and optically stimulated luminescent dosimeters.

A passive dosimeter using a crystalline material that stores energy from radiation and releases it as light when heated. The light output is proportional to absorbed dose.

A gas-filled detector operating at high voltage in which each ionizing event triggers a large avalanche, producing a uniform pulse. Excellent for detecting low-level radiation but not for measuring dose rate accurately.

A gas-filled detector operated at voltage where ion pairs are collected without avalanche multiplication, giving a current proportional to dose rate. Widely used for accurate radiation survey and calibration.

A gas-filled detector in the voltage region where avalanche multiplication occurs, producing pulse heights proportional to initial ionization. Can discriminate radiation types and measure energy.

A detector in which radiation produces light flashes in a crystal or plastic, converted to electrical pulses by a photomultiplier or photodiode. Offers high sensitivity and energy discrimination.

A vacuum device that converts faint light pulses from a scintillator into amplified electrical signals. Its gain and stability strongly affect detector performance and energy resolution.

The measurement and analysis of gamma-ray energy spectra to identify and quantify radionuclides. Uses detectors with good energy resolution and calibrated energy and efficiency response.

The time required for half the atoms of a given radionuclide to decay. It determines how long a source remains hazardous and is fundamental to decay correction and waste management.

The spontaneous transformation of unstable atomic nuclei into more stable configurations, emitting particles or photons. Each radionuclide has characteristic decay modes and rates.

A helium nucleus emitted in certain radioactive decays, with high mass and charge but very short range in matter. Hazardous mainly when inhaled or ingested due to high local energy deposition.

A fast electron or positron emitted during radioactive decay, with moderate range in matter. Can cause skin dose and is shielded by plastic or low-atomic-number materials.

Secondary X-rays produced when fast electrons are decelerated by interaction with atomic nuclei. Significant when beta emitters are shielded with high-atomic-number materials.

The rule that radiation intensity from a point source decreases with the square of distance from it. Doubling distance reduces dose rate to one quarter, a key protective strategy.

Material placed between a radiation source and people to attenuate the beam and reduce dose. Effective material and thickness depend on radiation type and energy.

A biological effect whose probability increases with dose but whose severity does not, such as cancer induction. Generally treated as having no threshold in radiation protection.

A tissue reaction that occurs only above a threshold dose and whose severity increases with dose, such as skin burns or cataracts. Prevented by keeping doses below thresholds.

The assumption that cancer risk rises linearly with dose with no safe threshold, used for radiation protection planning. It is a conservative regulatory model, not a proven biological mechanism at low doses.

Assessment of dose from radionuclides taken into the body by inhalation, ingestion, or wound. Uses biokinetic models, intake measurements, and committed dose calculations.

The activity of a radionuclide that, if taken in over a year, would result in a committed dose equal to the relevant limit. Used to set controls on airborne and ingested radioactivity.

The unwanted presence of radioactive material on surfaces, in the body, or in the environment. Distinguished from exposure to an external source and controlled by monitoring and decontamination.

The process of removing radioactive contamination from people, equipment, or surfaces to reduce dose and prevent spread. Priorities are protecting skin, limiting uptake, and controlling contaminated waste.

A portable instrument used to measure radiation dose rate or contamination in the field. Selection depends on radiation type, energy range, and sensitivity required.

A regulatory provision removing practices or sources from full control because their associated dose is trivial. Exempt sources still may carry labeling or disposal conditions.

Categorization of radioactive waste by activity level and half-life, such as exempt, low-level, intermediate-level, and high-level. Classification determines handling, storage, and disposal routes.

The regulatory release of material or waste from nuclear control once radioactivity is below defined levels. Cleared material may be recycled or disposed of as ordinary waste.

A defined area around a facility within which pre-planned protective actions are prepared for a radiological emergency. Zones guide sheltering, evacuation, and iodine distribution decisions.

A protective action in which people stay indoors with windows and ventilation closed to reduce exposure to airborne radioactivity. Used when evacuation would cause greater risk than staying put.

The planned movement of people away from an area to avoid or reduce radiation exposure during an emergency. Timing and routes are chosen to minimize dose and disruption.