Glossary

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Access control: The process of restricting access into an affected zone to emergency workers and other authorized individuals only.

Activation: Usually the first phase of the response to a nuclear emergency, which consists of bringing together members of the National Support Structure.

Activity: See Radioactivity

Alpha (α) particle: A positively charged particle consisting of two protons and two neutrons, emitted by some radioactive elements. They are highly ionizing, but do not travel far: shielding against alpha particles requires only a thin layer of material, such as a piece of paper.

Atom: The smallest part of an element, comprising a nucleus of protons and neutrons surrounded by electrons orbiting the nucleus.

Becquerel (Bq): The Système Internationale unit used to measure the radioactivity of a radioactive source. 1 Bq = 1 nuclear disintegration per second. The unit is named after the French physicist A-H. Becquerel.

Beta (β) particle: A charged particle consisting of a positive or negative electron, emitted by a radioactive element. Beta particles can travel farther than alpha particles, and can penetrate about 2 cm. into human skin. Shielding from beta particles requires material of the thickness and density of a piece of plywood.

Chain reaction: A nuclear reaction set off by the fission of the nucleus of an atom, such as uranium, releasing neutrons which in turn causes fission of other nuclei, thus maintaining the fission reaction over time.

Contamination: The undesirable presence of a radioactive substance deposited on, or incorporated into, an organism, material or place, particularly where its presence may be harmful.

Curie: The unit formerly used to measure radioactivity, replaced in much of the world by the becquerel. However, the curie is still used in the United States.

Deactivation: The process of terminating the provisions under the Federal Nuclear Emergency Plan at the end of the emergency response phase, and transition to the recovery phase.

Decontamination: The removal of radioactive material from people, objects, animals or property. This procedure can be as simple as washing thoroughly with soap and water.

Designated officials: Federal personnel designated by their department or agency to either represent their organisation or to serve in a supporting role within the National Support Structure.

Dose, absorbed: The energy imparted by ionizing radiation to a unit mass of any material, living or non-living. Expressed in Grays (Gy). 1Gy = 1 joule per kilogram.

Dose assessment: The process of quantifying the biological effects of exposure to radiation, taking into account factors such as the type of radiation, the parts of the body which are exposed, the duration of exposure, and shielding.

Dose, effective: The absorbed dose multiplied by factors accounting for the specific sensitivities of different parts of the body to various types of radiation. Expressed in Sieverts (Sv). Also referred to as whole body dose.

Dose limits: Limits to exposure to radiation set by regulation, in Canada by the Canadian Nuclear Safety Commission. Dose limits are intended to protect workers and the public from over-exposure to radiation. Separate public and occupational dose limits are established. Also called exposure limits.

Dose, whole body: Synonym for effective dose (qv).

Dosimeter: An instrument used to measure the absorbed dose from external exposure to radiation.

Element: A substance that cannot be further broken down by chemical means. Matter is composed of elements. An element is characterized by the number of protons in its nucleus.

Emergency function: General subject area which groups actions that may be taken by a primary and a number of supporting departments or agencies in the preparedness or response phase of an emergency.

Emergency management organization: An organisation, activated when a nuclear plan or “all-hazards” emergency plan is implemented, which is responsible for coordinating the response to a nuclear emergency.

Emergency planning zone: A defined area around a nuclear facility for which detailed planning and preparations are made in advance to ensure that appropriate protective measures can be applied in a timely and accurate manner.

Emergency support function: General subject area which groups actions that may be taken by a primary department or agency and where the focus is exclusively on providing support to provinces in the response phase of an emergency.

Emergency worker: Persons performing emergency services who are required to remain in, or to enter, offsite areas affected, or likely to be affected by radiation from an accident, and for whom special safety arrangements are required. They may include police, firefighters, ambulance and emergency social services workers, and other essential services.

Entry control: A protective measure in which non-essential personnel are prevented from entering an affected area.

Evacuation: A protective measure in which individuals must leave their homes quickly, staying away for a limited period of time to avoid or reduce radiation exposure.

Exposure: External or internal irradiation.

Exposure, external: Irradiation from a nearby source of radiation. The radiation emitted by the source travels through the air and irradiates the person.

Exposure, internal: Irradiation from a radioactive substance inside the body. A radioactive substance may be inhaled, as a radioactive gas or particles suspended in air, or ingested in radioactive dust, or water contaminated with radioactive substances. It may also enter the body through a cut in the skin. Some of these substances will decay in a very short time, or the body may excrete them. Others may lodge in body tissue, where they will continue to emit radiation.

Exposure pathways: Routes by which radioactive material can reach and/or irradiate a person. Examples are an exposure from a radioactive plume, deposition on the soil, or ingestion of contaminated food and water.

Exposure, surface: Irradiation from a source of radiation on a person's skin. The radiation source is in tiny particles which expose the skin and the underlying tissue, until they are washed away.

Federal Coordination Officer: The senior official designated by Health Canada or the Lead Federal Minister for the response to provide liaison and coordinate support between the provincial emergency operations center and the National Support Centre.

Federal Liaison Officers: The federal officials who are responsible for ensuring liaison between a provincial group (eg. Coordination group, information group, technical group), the corresponding group in the National Support Centre, and federal regional resources.

Federal Nuclear Emergency Plan (FNEP): The Canadian federal plan that describes the organisation and concept of operation for the federal response to a civil nuclear emergency in Canada, or one that occurs in another country and affects Canada or Canadians abroad.

Federal Regional Organisation: The component of the National Support Structure composed of all federal regional representatives located in the affected province(s) and directly involved in providing support to the province or carrying out response actions in a province.

Fission: Splitting of the nucleus of a heavy atom into two lighter nuclei, accompanied by the release of neutrons and other types of energy of the fission products.

Food control: Measures taken to prevent the consumption of foodstuffs that have been radioactively contaminated above acceptable levels as a result of a nuclear emergency, including the supply of uncontaminated foodstuffs.

Gamma rays: High-energy electromagnetic radiation producing ionisation of exposed matter. Gamma rays are very penetrating: they can travel hundreds of metres in air and can pass through the human body. Shielding against gamma rays requires thick layers of dense materials, such as lead.

Gray (Gy): The Système Internationale unit used to measure the absorbed dose (q.v.). 1 gray = 1 joule of energy transferred to 1 kilogram of matter. The gray, named after English radiobiologist Louis Gray, replaced the rad.

Half-life: The time required for the disintegration of half the atoms of a radioactive substance, through radioactive decay.

Hand-held contamination monitor: A portable instrument used to monitor surface radioactive contamination of people, clothing, or objects.

Implementation of the FNEP: Bringing into force the provisions of the Federal Nuclear Emergency Plan as the basis for coordination of actions and related expenditures at the federal level in response to a nuclear emergency.

Ingestion exposure emergency planning zone: A defined zone around a nuclear facility for which detailed planning and preparations are made in advance to ensure that appropriate measures against exposure from ingestion of radioactive material can be applies in a timely and accurate manner.

International Nuclear Event Scale (INES): A scale to promptly and consistently communicate to the public the safety significance of reported events at nuclear installations. Developed jointly by the International Atomic Energy Agency and the Nuclear Energy Agency of the Organisation for Economic Cooperation and Development.

Intervention: Any action of provision beyond normal procedures undertaken to manage the emergency and mitigate its impacts, including all emergency organisation structures, response actions, communications, and public information and directives

Ionisation: Removal of an electron from a neutral atom or molecule, creating a positively charged ion. These atoms recombine very quickly and can cause biological effects in cells. One cause of ionisation is exposure to radioactive particles or rays.

Irradiation: Exposure of material or the human body to radiation.

Isotopes: Forms of an element whose atoms have the same number of protons, but a different number of neutrons. All the isotopes of an element have the same chemical properties, but their physical properties, such as atomic mass, vary.

KI: See Potassium iodide.

Lead Federal Minister/ Department: The federal Minister and Department designated by the Prime Minister of Canada, or as indicated in the Federal Policy for Emergencies, to arrange and coordinate national activities to provide support to a province, and to coordinate the activities of the federal departments and agencies involved. For nuclear emergencies, the designated lead federal department is Health Canada.

Moderator: The substance, often liquid, in the core of a nuclear reactor that slows neutrons to promote the fission chain reaction. In CANDU reactors, the moderator is heavy water, a form of water with an isotope of hydrogen that has two neutrons.

National Coordinator: A senior federal official designated by Health Canada responsible for implementing the Federal Nuclear Emergency Plan and overseeing activities of the National Support Structure during the response phase of a nuclear emergency.

National Support Centre: The location of the federal emergency operating groups established to coordinate actions between the federal departments and agencies, and other jurisdictions, involved in the response to a nuclear emergency.

National Support Structure: The structure manifested for coordinating the federal response to a nuclear emergency, activated either prior to or following implementation of the Federal Nuclear Emergency Plan.

Neutron: A subatomic particle in the nucleus of an atom, without an electrical charge. Neutrons may be produced in nuclear fission reactors, or rarely, in spontaneous fission reactions in uranium.

Notification: A punctual action by which a specific individual or an organisation is formally informed of a critical decision or action. It should not be confused with reporting, which has a specific and separate meaning.

Nuclear disintegration: Synonym for radioactive decay (q.v.).

Nuclear emergency: An emergency which has led, or could lead, to a radiological threat to public health and safety, property, or the environment.

Nuclear emergency function: Subject area which groups actions specifically related to a nuclear emergency that may be taken by primary and/or supporting departments or agencies in the response phase of a nuclear emergency.

Nuclear facility: A nuclear reactor, sub-critical nuclear reactor, research reactor, or plant for the separation, processing, reprocessing, or fabrication of fissionable substances from irradiated fuel. It also includes all land, buildings and equipment that are connected or associated with these reactor or plants.

Nuclear Liability Act: The federal Act that establishes guidelines for insurance for damages resulting from a nuclear emergency.

Nuclear powered vessel: A marine vessel whose main propulsion system is driven by a nuclear reactor.

Off-site: The area outside the boundary of a nuclear facility. The municipal, provincial, and federal levels of government are responsible for off-site emergency planning, preparedness and response.

On-site: The area inside the boundary of a nuclear facility, also called the exclusion area. The operators of nuclear facilities are responsible for on-site emergency planning, preparedness and response.

Plume: A cloud of airborne radioactive material that is transported from a nuclear or radiological source in the direction of the prevailing wind.

Plume exposure emergency planning zone: A defined zone around a nuclear facility for which detailed planning and preparations are made in advance to ensure that appropriate measures against exposure to a radioactive plume (such as sheltering or evacuation) can be applied in a timely and accurate manner.

Portal monitor: A radiation monitor built like a door frame, inside which a person stands while the monitor scans for radioactive contamination of skin, hair, and clothing.

Potassium iodide (KI): A compound prescribed in tablet form to limit the absorption by the human thyroid gland of radioactive iodine-131, which may be present in the atmosphere as a result of a radioactive release. Potassium iodide may be used by emergency workers and people living in the vicinity of the release. Potassium iodide is also called stable iodide, and the process of taking it to prevent absorption of radioactive iodine is termed “thyroid blocking”.

Protective measures: Measures taken to reduce radiation doses which could be incurred by the population or emergency workers during a nuclear emergency. Also referred to as a countermeasure or protective action.

Provincial Emergency Measures Organisation: The organisation which is responsible for off-site emergency planning, preparedness, and response in a specific province.

Provincial emergency operations centre: In the province directly affected by the emergency, a centre operated by a provincial emergency management organisation that coordinates the emergency operations at a provincial level.

Provincial information centre: In the province directly affected by the emergency, a centre operated by a provincial emergency management organisation which handles the provision of emergency information to the media and the public.

Primary department or agency: A federal institution assigned primary responsibility to manage and coordinate one or more emergency functions.

Rad: Former unit of measurement of absorbed dose (q.v.), replaced by the gray (q.v.). The rad is still used in the United States. 1 rad = 0.01 gray.

Radiation, background: The radiation arising from natural radiation sources such as terrestrial radiation from radioactive substances in the soil, and cosmic radiation from space.

Radiation, ionizing: Radiation that causes ionisation of atoms by loss of electrons.

Radioactive decay: The breakdown of the atomic nucleus leading to the emission of particle radiation (alpha or beta), or electromagnetic radiation (gamma rays), or a combination of these. A decay process is characterised by a radioactive half-life (q.v.), which is distinctive for each radioisotope.

Radioactivity: The ability of some elements to transform themselves by nuclear decay as a result of changes in the atomic nucleus, by particle radiation (alpha or beta) or electromagnetic radiation (gamma rays).

Radioisotope: A radioactive isotope of a chemical element. An element may have several isotopes, of which some may be radioactive and some stable.

Recovery phase: The phase during which activities focus on restoration of quality of life, social systems, economies, community infrastructures, and the environment. This phase may last up to several years after the emergency.

Release: The controlled or accidental discharge of radioactive substances into the atmosphere or water, which may occur during the operation of nuclear facilities. Also called emission.

Relocation: A non-urgent removal or continued expulsion of people from contaminated areas to avoid chronic radiation exposure.

Rem: A former unit of measurement of equivalent dose, replaced by the sievert. The rem is still used in the United States. 1 rem = 0.01 sievert.

Reporting: Term referring to the act of informing a specific authority of a given event or situation in accordance with specific regulatory requirements or equivalent criteria.

Resettlement: A long-term protective action in which people are kept out of a contaminated area permanently. Also called permanent relocation.

Response phase: The phase during an emergency in which activities focus on saving lives, on treating the injured, contaminated, and overexposed persons, and on preventing and minimising further health effects and other forms of impacts. This phase may last from a few hours to several weeks after the commencement of the emergency and would be followed by a recovery phase, as necessary.

Sheltering: A protective measure that consists of staying indoors, with closed doors and windows, to limit the inhalation of radioactive products that may be present following a release of radiation, or to protect against direct gamma radiation from a radioactive cloud, or from radioactive material deposited on the ground.

Shielding: Material placed between a radiation source and human beings, equipment or other objects in order to prevent or reduce ionizing radiation from reaching the person or object.

Sievert (Sv): The Système Internationale unit of measurement of the equivalent dose (q.v.) or radiation received by a tissue, an organ, or an organism. The sievert expresses the biological effect of a particular absorbed dose (q.v.) expressed in grays (q.v.). The sievert replaced the rem.

Supporting department or agency: A federal institution designated to assist a specific primary department or agency in the delivery of one or more emergency functions.

Survey meter: An instrument that measures external radiation dose.

Système Internationale (SI): The international system of units of measurement based on the metric system. The old system terminology of the curie, rad, and the rem has been replaced in the SI by the becquerel, the gray, and the sievert. The United States continues to use the old system.

Task team: A group of specialists from more than one department or agency who work closely together during the response phase of a nuclear emergency in order to carry out a specific task (e.g. dose prediction). A task team reports to a specific group of the National Support Centre; i.e. the Coordination and Operations Group, the Public Affairs Group, or the Technical Advisory Group.

Temporary relocation: A protective measure in which a population in a contaminated area would be evacuated for a period of several weeks or months

Thyroid blocking: See Potassium iodide.

Thyroid blocking agent: A substance which prevents or reduces the uptake of radioactive iodine by the thyroid. Usually stable potassium iodide (KI) is taken orally for this purpose.

Urgent protective actions: Actions that must be taken promptly in order to be effective, and the effectiveness of which will be markedly reduced if delayed. They include evacuation, sheltering, and administration of a thyroid blocking agent.