1.   The process of determining whether a practice is, overall, beneficial, as required by ICRP’s System of Radiological Protection, i.e. whether the benefits to individuals and to society from introducing or continuing the practice outweigh the harm (including radiation detriment) resulting from the practice.
2.   The process of determining whether a proposed intervention is likely, overall, to be beneficial, as required by ICRP’s System of Radiological Protection, i.e. whether the benefits to individuals and to society (including the reduction in radiation detriment) from introducing or continuing the intervention outweigh the cost of the intervention and any harm or damage caused by the intervention.


kerma, K:
The quantity K, defined as:

where dEtr is the sum of the initial kinetic energies of all charged ionizing particles liberated by uncharged ionizing particles in a material of mass dm. [40]
Unit: gray (Gy).
Originally an acronym for kinetic energy released in matter, but now accepted as a word.

  • air kerma: The kerma value for air.
    Under charged particle equilibrium conditions, the air kerma (in gray) is numerically approximately equal to the absorbed dose in air (in gray).
  • reference air kerma rate: The kerma rate to air, in air, at a reference distance of one metre, corrected for air attenuation and scattering. [40]
    This quantity is expressed in µGy/h at 1 m.


legal person:
Any organization, corporation, partnership, firm, association, trust, estate, public or private institution, group, political or administrative entity or other persons designated in accordance with national legislation, who or which has responsibility and authority for any action having implications for protection or safety.
Contrasted in legal texts with natural person, meaning an individual.


1.   A legal document issued by the regulatory body granting authorization to perform specified activities related to a facility or activity.
The holder of a current licence is termed a licensee.  Other derivative terms should not be needed; a licence is a product of the authorization process (although the term licensing process is sometimes used), and a practice with a current licence is an authorized practice.
Authorization may take other forms, such as registration.
2.   [Any authorization granted by the regulatory body to the applicant to have the responsibility for the siting, design, construction, commissioning, operation or decommissioning of a nuclear installation.] [6]
3.   [Any authorization, permission or certification granted by a regulatory body to carry out any activity related to management of spent fuel or of radioactive waste.] [7]

! The definitions (2) and (3) from the Conventions are somewhat more general in scope than the normal Agency usage in definition (1).  In Agency usage, a licence is a particular type of authorization, normally representing the primary authorization for the operation of a whole facility or activity.  The conditions attached to the licence may require that further, more specific, authorization or approval be obtained by the licensee before carrying out particular activities.

See licence (1).

licensing process:
See licence (1).


The value of a quantity used in certain specified activities or circumstances that must not be exceeded. [40]

!        The term limit should only be used for a criterion that must not be exceeded, e.g. where exceeding the limit would cause some form of legal sanction to be invoked.  Criteria used for other purposes — e.g. to indicate a need for closer investigation or a review of procedures, or as a threshold for reporting to a regulatory body — should be described using other terms, such as reference level.

linear energy transfer (LET), LD:
Defined generally as:

where dE is the energy lost in traversing distance dl and D is an upper bound on the energy transferred in any single collision.
A measure of how, as a function of distance, energy is transferred from radiation to the exposed matter.  A high value of LET indicates that energy is deposited within a small distance.
LY (i.e. with D = Y) is termed the unrestricted linear energy transfer, in defining quality factor.
LD is also known as the restricted linear collision stopping power.

The generation of a required binary output signal from a number of binary input signals according to predetermined rules, or the equipment used for generating this signal.

low dispersible radioactive material:
Either a solid radioactive material or a solid radioactive material in a sealed capsule, that has limited dispersibility and is not in powder form. [41]
A slightly less restrictive category than special form radioactive material.

low toxicity alpha emitters:
Natural uranium; depleted uranium; natural thorium; uranium-235 or uranium-238; thorium-232; thorium-228 and thorium-230 when contained in ores or physical and chemical concentrates; or alpha emitters with a half-life of less than 10 days. [41]