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F

facilities and activities [13]:
A general term encompassing nuclear facilities, uses of all sources of ionizing radiation, all radioactive waste management activities, transport of radioactive material and any other practice or circumstances in which people may be exposed to radiation from naturally occurring or artificial sources.
Facilities include nuclear facilities, irradiation installations, mining and milling facilities, waste management facilities and any other place where radioactive materials are produced, processed, used, handled, stored or disposed of or where radiation generators are installed on such a scale that consideration of protection and safety is required.  Activities include the production, use, import and export of radiation sources for industrial, research and medical purposes, the transport of radioactive material, the mining and processing of radioactive ores and closeout of associated facilities, cleanup of sites affected by residues from past activities and radioactive waste management activities such as the discharge of effluents.
This term is intended to provide an alternative to the terminology of sources and practices (or intervention) to refer to general categories of situations.  For example, a practice may involve many different facilities and/or activities, whereas the general definition (1) of source is too broad in some cases: a facility or activity might constitute a source, or might involve the use of many sources, depending upon the interpretation used.
The term facilities and activities is very general, and includes those for which no or little regulatory control may be necessary or achievable: the more specific terms authorized facility and authorized activity should be used to distinguish those facilities and activities for which any form of authorization has been given.

facility:
See facilities and activities.

failure:
Inability of a structure, system or component to function within acceptance criteria.

! Note that the structure, system, or component is considered to fail when it becomes incapable of functioning, whether or not it is needed at that time.  A failure in, for example, a backup system may not be manifest until the system is called upon to function, either during testing or on failure of the system it is backing up.

failure mode:
The manner or state in which a structure, system or component fails.

far field:
The geosphere outside a repository, including the surrounding strata, at a distance from the repository such that, for modelling purposes, the repository may be considered as a single entity, and the effects of individual waste packages are not distinguished.
For practical purposes, often interpreted simply as the geosphere beyond the near field.

fissile (adj.):
Capable of undergoing fission by interaction with slow neutrons.
More restrictive than fissionable.

fissile material:
Uranium-233, uranium-235, plutonium-239, plutonium-241, or any combination of these radionuclides.  Excepted from this definition is:

  • natural uranium or depleted uranium which is unirradiated, and
  • natural uranium or depleted uranium which has been irradiated in thermal reactors only. [41]
    As with radioactive material, this is not a scientific definition, but one designed to serve a specific regulatory purpose.

fission product:
A radionuclide produced by nuclear fission.
Used in contexts where the radiation emitted by the radionuclide is the potential hazard.

fissionable (adj.):
Capable of undergoing fission.
c.f. fissile.

fluence:
A measure of the strength of a radiation field.  Commonly used without qualification to mean particle fluence.

  • energy fluence, Y: A measure of the energy density of a radiation field, defined as:
    <
    where dR is the radiation energy incident on a sphere of cross-sectional area da.
    The energy fluence rateis denoted by a lower case y.
    See ICRP Publication 51.[51]
  • particle fluence, F: A measure of the density of particles in a radiation field, defined as:

    where dN is the number of particles incident on a sphere of cross-sectional area da.
    The particle fluence rate is denoted by a lower case f.
    See ICRP Publication 51.[51]

freight container:
An article of transport equipment designed to facilitate the transport of goods, either packaged or unpackaged, by one or more modes of transport without intermediate reloading.  It shall be of a permanent enclosed character, rigid and strong enough for repeated use, and must be fitted with devices facilitating its handling, particularly in transfer between conveyances and from one mode of transport to another.  A small freight container is that which has either any overall outer dimension less than 1.5 m, or an internal volume of not more than 3 m3.  Any other freight container is considered to be a large freight container. [41]

fuel assembly:
A set of fuel elements and associated components which are loaded into and subsequently removed from a reactor core as a single unit.

fuel cycle:
See nuclear fuel cycle.

fuel element:
A rod of nuclear fuel, its cladding and any associated components necessary to form a structural entity.