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REGDOC-3.6, Glossary of CNSC Terminology - Glossary - B

background radiation (rayonnement de fond)

The dose or dose rate (or an observed measure related to the dose or dose rate) attributable to all sources other than the one specified.

back‑out dose limit (limite de dose de marche arrière)

The predetermined dose limit that should prompt emergency responders to physically retreat from an area and then assess the situation.

backup trip parameter (paramètre de déclenchement secondaire)

See primary and backup (secondary) trip parameter.

balance of the pregnancy (reste de la grossesse)

The period from the moment a licensee is informed, in writing, of the pregnancy to the end of the pregnancy. (Source: Radiation Protection Regulations)

baseline criteria (critères de base)

A set of measurements (or metrics) representing the starting level of performance for a structure, system or component. Baseline criteria are derived from design requirements and are usually established during commissioning and after replacement, overhaul or refurbishment.

basic radionuclide value (valeur de base pour un radionucléide)

Either an A1 in TBq, an A2 in TBq, an activity concentration limit for an exempt material in Bq/g or an activity limit for an exempt consignment in Bq, as set out in the IAEA Regulations. (Source: Packaging and Transport of Nuclear Substances Regulations, 2015)

Note: Bq/g means becquerels/gram; TBq means terabecquerels.

batch (lot)

A portion of nuclear material handled as a unit for nuclear material accounting purposes at a key measurement point. The composition and quantity are defined by a single set of specifications (material description code) or measurements (concentration, enrichment). Note: The nuclear material may be in bulk form or contained in a number of separate items. Items included in a batch must contain nuclear material of the same element concentration and enrichment. Items of different material description codes must be reported as separate batches.

batch data (données concernant le lot)

The total weight of each element of nuclear material and its isotopic composition as applicable. See also source data.


See best available technology and techniques economically achievable.


See beyond-design-basis accident.


beyond-design-basis earthquake


See beyond-design-basis threat.


See by-difference correction principle.


below expectations; see safety performance rating methodology

beam limiter (obturateur de faisceau)

A radiation-shielding device, located at the working position of an exposure device, which is designed to reduce the radiation dose rate in directions other than the direction intended for use. The beam limiter may be designed to be used in conjunction with an exposure head or may incorporate an exposure head as an integral part of the device. Also called collimator.


See best estimate and uncertainty (BEAU) method.

becquerel (Bq) (becquerel [Bq])

The International System of Units (SI) unit of radioactivity. One becquerel (Bq) is the activity of a quantity of radioactive material in which one nucleus decays per second. In Canada, the Bq is used instead of the non‑SI unit curie (Ci).

Note 1: 1 Bq = 27 pCi (2.7 x 10-11 Ci) and 1 Ci = 3.7 x 1010 Bq.

Note 2:

1 megabecquerel (MBq) = 106 Bq

1 gigabecquerel (GBq) = 109 Bq

1 terabecquerel (TBq) = 1012 Bq

below expectations (BE) (inférieur aux attentes [IA])

See safety performance rating methodology.

benchmark experiment (valeur repère)

With respect to nuclear criticality safety, a well-characterized experiment at the critical state that may be used to establish the reliability of calculational methods.

best available technology and techniques economically achievable (BATEA) (meilleures techniques existantes d’application rentable [MTEAR])

Minimum pollution prevention performance standards for controlling releases (effluents and/or emissions) to the environment that have been demonstrated as achievable within a given industrial sector and are therefore economically achievable across that sector. BATEA takes into account both treatment technologies and techniques used to achieve the desired control. The way in which the installation is designed, built, maintained, operated and decommissioned is also considered as part of these technologies and techniques. Note: BATEA may change over time as technologies and techniques are improved. As a best practice, BATEA should be regularly reviewed.

best estimate (meilleure estimation)

With respect to safety analysis, an unbiased estimate obtained by using a mathematical model, calculation method or data to realistically predict behaviour and important parameters.

best estimate and uncertainty (BEAU) method (méthode de la meilleure estimation et des incertitudes [BEAU])

An analysis that assumes more realistic initial and boundary conditions with all uncertainties (those associated with assumptions, models and computer codes) defined to a high level of confidence.

best estimate method (méthode de la meilleure estimation)

A method designed to give realistic results.

best practice (pratique exemplaire)

An industry-accepted approach (for example, toward a design, process or procedure) that is acknowledged as consistently producing superior results.

beta backscatter gauging (jaugeage de rétrodiffusion bêta [Beta Backscatter])

The use of beta-emitting nuclear substances incorporated in a radiation device to measure the thickness of material. The term is used as a licence use type.

beta particle (particule bêta)

A charged particle that is emitted from the nucleus of a radioactive element during radioactive decay of an unstable atom. Large amounts of beta radiation may cause skin burns, and beta emitters are harmful if they enter the body. Beta particles may be stopped by thin sheets of metal or plastic.

beta radiation(rayonnement bêta)

See beta particle.

beyond-design-basis accident (BDBA) (accident hors dimensionnement [AHD])

An accident less frequent and potentially more severe than a design-basis accident. Note: For a reactor facility, a beyond-design-basis accident may or may not involve fuel degradation.

beyond-design-basis initiating event (événement déclencheur hors dimensionnement)

Any initiating event that is not considered in the design of the facility including external hazards that are beyond the design basis such as large seismic loads, tsunamis, flooding by extreme high water level, damage by extreme weather conditions (e.g., hurricanes, ice-rains, sandstorms, etc.), or man-made actions or structures, such as airplane crashes, transport accidents, nearby chemical plants, gas pipes or river dams.

beyond-design-basis threat (BDBT) (menace hors dimensionnement [MHD])

Threat conditions, more severe than a design-basis threat, that may result in structural degradation and may involve confinement degradation.

bias (biais)

A measure of the systematic differences between calculational method results and experimental data. Uncertainty arises from a systematic error that is known to cause deviation in a fixed direction.

bioassay (essai biologique)

The study of all living organisms to measure the effect of a substance, factor or condition by comparing before-and-after exposure or other data. Note: Specific to radiation exposure in humans, bioassay is any procedure used to determine the nature, activity, location or retention of radionuclides in a body by direct (in vivo) measurement or by indirect (in vitro) analysis of material excreted or otherwise removed from a body.In vivo bioassay may be referred to as direct bioassay; in vitro bioassay may be referred to as indirect bioassay.

biokinetic model (modèle de biocinétique)

A mathematical description of the behaviour of radionuclides in the metabolic processes of cells, tissues, organs and organisms. The term is most frequently used to describe distribution of radionuclides among tissues and excretion.

biota (biote)

All living organisms, including humans.

biotic (biotique)

Relating to the living parts of the environment: plants, animals and microorganisms. Biotic components include any part of the environment considered important by the licensee, the general public, the scientific community, the Government of Canada, and any environmentally sensitive habitat.

blinding (« en aveugle »)

Conditions for which an actuation or conditioning signal is approached but not reached, either because of the small magnitude of the initiating event or the actions of any other process or safety system.

block of consecutive shifts (bloc de quarts consécutifs)

Set of consecutive shifts with the same start and end times followed by a minimum recovery period and a subsequent set of consecutive shifts.

boiler (générateur de vapeur)

See steam generator.

boiling water reactor (BWR) (réacteur à eau bouillante [REB])

A common type of light-water reactor, where water is allowed to boil in the core, generating steam directly in the reactor vessel to generate electrical power.

book-adjusted ending (stock comptable final)

The algebraic sum of the beginning physical inventory and of the inventory changes of a material balance area over a given period, adjusted to take account of shipper–receiver differences. Also called adjusted book ending.

book inventory (stock comptable)

The algebraic sum for a given point in time of the most recent physical inventory of a material balance area and all inventory changes that have occurred since that physical inventory was taken.

borehole tube tagging (marquage de tuyaux de sondage)

The use of nuclear substances placed subsurface or in equipment intended for subsurface use for determining borehole depth or direction. This term is used as a licence use type.

borescope (endoscope)

An inspection tool with a rigid or flexible optical tube designed for insertion into bores and cavities. The borescope consists of a lens positioned in front of a long tube containing image and illumination relays.

boundary conditions (conditions aux frontières)

The values of variables in a mathematical model that are assumed at the spatial bounds of the model.

bounding assessment (évaluation de délimitation)

An assessment designed to provide limiting or worst-case predictions, based on simplification of the processes being simulated or the use of data limits (such as maximum possible precipitation or thermodynamic solubility limits).

bounding envelope (enveloppe limitative)

A combination of facility design parameters and site characteristics that establishes a set of limiting values for any facility design that could be proposed for the site and that allows for the assessment of environmental effects and site evaluation. Note: The design eventually selected must fit within the bounding envelope.

bounding event (événement limitatif)

The event with the smallest predicted margin to a specific acceptance criterion.

Bq (Bq)

See becquerel.

brachytherapy machine (appareil de curiethérapie)

See brachytherapy remote afterloader.

brachytherapy remote afterloader (appareil de curiethérapie à projecteur de source télécommandé)

A device that is designed to place, by remote control, a sealed source inside or in contact with a person for therapeutic purposes and to remove, by remote control, the sealed source once a preset dose of radiation has been delivered or after a preset time has elapsed. (Source: Class II Nuclear Facilities and Prescribed Equipment Regulations)

breath alcohol technician (éthylométriste)

With respect to breath samples, a person who is qualified to operate an approved instrument. Also called qualified technician. See also approved instrument.

Bremsstrahlung (rayonnement de freinage [Bremsstrahlung])

Electromagnetic radiation produced by the deceleration of a charged particle, such as an electron, when deflected by another charged particle, such as an atomic nucleus.

buckling (flambage)

In engineering, a failure mode characterized by the sudden failure of a structural member (for example, a containment shell) that is subjected to high compressive stresses, where the actual compressive stresses at failure are smaller than the ones that the material is capable of withstanding. Also called failure due to elastic instability.

bulk form (matière en vrac)

Material such as a liquid, gas, powder, pellets or pebbles which, due to its containment, is not individually identified for accounting purposes. Bulk form material may be contained in a tank, drum, tote or box.

bulk quantity (quantité en vrac)

Means, in respect of the terms “exemption quantity” and “unconditional clearance level”,

  1. when referred to in section 5, a quantity of material greater than one tonne; and
  2. when referred to in section 5.1, a quantity of material greater than one tonne per year per nuclear facility.

(Source: Nuclear Substances and Radiation Devices Regulations)

burnup (combustion nucléaire)

See fuel burnup.


See boiling water reactor.

by‑difference correction principle (BDCP) (principe de correction selon l’écart [PCSE])

The principle by which a correction to an inventory change data element in a report is applied within the material balance period in which the change is dated. The weight difference between the original record and the correcting record is recorded in the accounts (that is, general ledger) on the date the correction to the inventory change is realized and recorded.

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