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

hypothetical accident conditions

For a radionuclide, the time required for the activity to decrease, by a radioactive decay process, by half. Note: Half‑lives vary from a fraction of a second to billions of years. For example, the half‑lives of cobalt‑60 and of iridium‑192 are 5.3 years and 74.2 days, respectively.

The thickness of a shield or absorber (such as uranium, tungsten or lead) that reduces the amount of radiation to one half of its initial intensity. Also called half‑value thickness.

See half‑value layer.

A portable tool. Some handheld tools, in the context of nuclear security, may be used by an adversary to penetrate a security system or barrier. Some examples of handheld tools are bolt cutters, pliers or hacksaw blades, power tools, burn bars and cutting torches.

The process used to systematically identify and assess hazards to evaluate the potential internal, external, human-made and natural events that can cause the identified hazards to initiate faults that develop into accidents.

A substance, other than a nuclear substance, that is used or produced in the course of carrying on a licensed activity and that may pose a risk to the environment or the health and safety of persons. (Sources:  Class II Nuclear Facilities and Prescribed Equipment Regulations ; Uranium Mines and Mills Regulations )

hazardous substance or hazardous waste (substance dangereuse ou déchet dangereux)

A substance or waste, other than a nuclear substance, that is used or produced in the course of carrying on a licensed activity and that may pose a risk to the environment or the health and safety of persons. (Sources: General Nuclear Safety and Control Regulations ; Class I Nuclear Facilities Regulations )

high confidence of low probability of failure

See high dose rate (HDR) brachytherapy remote afterloader.

All radiation coming from within teletherapy source housing or accelerator target housing, other than the primary beam.

A system or component that provides a path for heat transfer from a source, such as heat generated in the fuel, to a large heat-absorbing medium, such as water. See also ultimate heat sink.

See primary heat transport system.

The rate at which the temperature of an object increases when heated.

See high-enriched uranium.

See highly enriched uranyl nitrate liquid.

See human factors.

human factors engineering; see human factors in design

A brachytherapy machine that uses a sealed source activity that, if exposed, will produce a dose rate in air of 10 milligrays per hour or greater at a distance of 1 metre from the source(s).

Uranium containing 20 percent or more by weight of isotope uranium‑235, isotope uranium‑233, or combined uranium‑233 and uranium‑235. Also called highly enriched uranium.

Liquid containing high‑enriched uranium.

Power production and research reactors greater than 10 MWt.

A commissioning activity that requires approval of the designated authority in order for commissioning to proceed.

A nuclear power plant or a nuclear facility where Category I or II nuclear material is processed, used or stored. (Source: Nuclear Security Regulations )

An activity that requires approval of the Commission or designated authority before the activity may proceed.

A holding area at an identified foreign facility to which unallocated Canadian-origin nuclear material can be exported and temporarily held pending the conclusion of a commercial arrangement for nuclear material held in the account.

human and organizational performance

Operation of a nuclear facility that is isolated from the grid and is supplying power only to its own auxiliary electric loads. Also called island load; island operation.

See equivalent dose.

hydrogenated tritium oxide; also called tritiated water

See primary heat transport system.

Inappropriate or inadequate human action, including failure to take action when required, which can arise from problems in sequencing, timing, knowledge, interfaces, procedures and other sources.

Factors that influence human performance as it relates to the safety of a nuclear facility or activities over all phases, including design, construction, commissioning, operation, maintenance and decommissioning. Some examples are organizational and management structures; policies and programs; allocation of functions to humans and machines; the design of user interfaces; staffing provisions; job-design features; work schedules; design of procedures; training; and the physical work environment.

See human factors in design.

The application of knowledge about human capabilities and limitations to a plant, facility, system or equipment design. Human factors in design ensure that the plant, facility, system or equipment design, human tasks and work environment, are compatible with the sensory, perceptual, cognitive and physical attributes of the personnel who operate, maintain and support it. Also called human factors engineering.

The outcomes of human behaviours, functions and actions, in a specified environment, that reflect the ability of workers and management to meet a system’s defined performance under the conditions in which the system will be employed.

A safety and control area (SCA) that covers activities that enable effective human performance through the development and implementation of processes that ensure a sufficient number of licensee personnel are in all relevant job areas and have the necessary knowledge, skills, procedures and tools in place to safely carry out their duties. This SCA is one of the 14 within the CNSC SCA Framework.

The administration of unsealed sources (nuclear substances) to, or external irradiation of, humans for purposes not related to their personal healthcare; includes processing of radiopharmaceuticals and laboratory studies that are part of the human research study.

See half‑value layer.

half‑value thickness; see half‑value layer

hydrogen-to-fissile atomic ratio