Definition

A medium into which the transferred residual heat can always be accepted, even if all other means of removing the heat have been lost or are insufficient.

Scope notes

• This medium is normally a body of water or the atmosphere.

Definition

All operations associated with the production of nuclear energy.

Scope notes

• Operations in the nuclear fuel cycle associated with the production of nuclear energy include the following:
  • (a) Mining and processing of uranium ores or thorium ores;
  • (b) Enrichment of uranium;
  • (c) Manufacture of nuclear fuel;
  • (d) Operation of nuclear reactors (including research reactors);
  • (e) Reprocessing of spent fuel;
  • (f) All waste management activities (including decommissioning) relating to operations associated with the production of nuclear energy;
  • (g) Any related research and development activities.

Definition

Uncertainty inherent in a phenomenon.

Scope notes

• Aleatory uncertainty (or stochastic uncertainty) is taken into account by representing a phenomenon in terms of a probability distribution model.
• Aleatory uncertainty is of relevance for events or phenomena that occur in a random manner, such as random failures of items of equipment. [INTERNATIONAL ATOMIC ENERGY AGENCY, Safety Assessment for Facilities and Activities, IAEA Safety Standards Series No. GSR Part 4 (Rev. 1), IAEA, Vienna (2016).]

<h2>Definition</h2><p>1. A multiattribute quantity expressing <i>hazard</i>, danger or chance of harmful or injurious consequences associated with <i>exposures</i> or <i>potential exposures</i>. It relates to quantities such as the probability that specific deleterious consequences may arise and the magnitude and character of such consequences.</p><h2>Scope notes</h2><ul><li>In mathematical terms, this can be expressed generally as a set of triplets, <img src="/PoolParty/OpenConfigPathResourceProvider/frontendroot?fileName=custom/iaea-safety-glossary/images/docimg/formula-risk.jpg" style= "vertical-align: middle" style= "vertical-align: middle" alt="formula" height="30">, where Sis an identification or description of a <i>scenario</i> i, pis the probability of that <i>scenario</i> and Xis a measure of the consequence of the <i>scenario</i>. The concept of <i>risk</i> is sometimes also considered to include uncertainty in the probabilities pof the <i>scenarios</i>.</li></ul>

Definition

Uncertainty attributable to incomplete knowledge about a phenomenon, which affects the ability to model it.

Scope notes

• a. Epistemic uncertainty is reflected in a range of viable models, multiple expert interpretations and statistical confidence.
• b. Epistemic uncertainty is associated with the state of knowledge relating to a given problem under consideration. In any analysis or analytical model of a physical phenomenon, simplifications and assumptions are made. Even for relatively simple problems, a model may omit some aspects that are deemed unimportant to the solution.
• c. Additionally, the state of knowledge within the relevant scientific and engineering disciplines may be incomplete. Simplifications and incompleteness of knowledge give rise to uncertainties in the prediction of outcomes for a specified problem.

Definition

A geographical area that contains an authorized facility, authorized activity or source, and within which the management of the authorized facility or authorized activity or first responders may directly initiate emergency response actions.

Scope notes

• a. This is typically the area within the security perimeter fence or other designated property marker. It may also be the controlled area around industrial radiography work or an inner cordoned off area established by first responders around a suspected hazard.
• d. The term activity is used here in the sense of activity (2).
• c. This area is often identical to the operations area, except in situations (e.g. research reactors, irradiation installations) where the authorized facility is on a site where other activities are being carried out beyond the operations area, but where the management of the authorized facility can be given some degree of authority over the whole site area.
• b. The boundary of the site area is called the site boundary.

Definition

An assembly containing fissile material intended to sustain a controlled fission chain reaction at a low power level, used to investigate reactor core geometry and composition.

Scope notes

• A critical assembly — as a device that is designed and used to sustain nuclear reactions — may be subject to frequent changes to the configuration of the reactor core and the lattice, and may frequently be used as a mock-up of a configuration of a reactor core.

Definition

2. An application of safety requirements that is commensurate with the characteristics of the facilities and activities or the source and with the magnitude and likelihood of the exposures.

Scope notes

• See also exclusion, exemption, clearance and optimization.

Definition

1. The function or power or (usually as controls) means of directing, regulating or restraining.

Scope notes

• It should be noted that the usual meaning of the English word control in safety related contexts is somewhat ‘stronger’ (more active) than that of its usual translations and other similar words in some other languages. For example, control typically implies not only checking or monitoring something but also ensuring that corrective or enforcement measures are taken if the results of the checking or monitoring indicate such a need. This is in contrast, for example, to the more limited usage of the equivalent word in French and Spanish.

Definition

The first members of an emergency service to respond at the site of an emergency.

Definition

1. Any nuclear facility subject to authorization that is part of the nuclear fuel cycle, except facilities for the mining or processing of uranium ores or thorium ores and disposal facilities for radioactive waste.

Scope notes

• b. For safeguards purposes, see the definition of nuclear installations in the Safeguards Glossary [IAEA Safeguards Glossary (2022 Edition), IAEA, Vienna].
• a. This definition thus includes: nuclear power plants; research reactors (including subcritical and critical assemblies) and any adjoining radioisotope production facilities; storage facilities for spent fuel; facilities for the enrichment of uranium; nuclear fuel fabrication facilities; conversion facilities; facilities for the reprocessing of spent fuel; facilities for the predisposal management of radioactive waste arising from nuclear fuel cycle facilities; and nuclear fuel cycle related research and development facilities.

Definition

2. Any material that is either special fissionable material or source material as defined in Article XX of the IAEA Statute.

Scope notes

• a. Nuclear material is necessary for the production of nuclear weapons or other nuclear explosive devices. Under comprehensive safeguards agreements, the IAEA verifies that all nuclear material subject to safeguards has been declared and placed under safeguards.
• b. Certain non-nuclear materials are essential for the use or production of nuclear material and may also be subject to IAEA safeguards under certain agreements.
• d. The Statute of the IAEA [Statute of the International Atomic Energy Agency, IAEA, Vienna (1990).] uses the term special fissionable material, with the meaning essentially of nuclear material as defined here, but explicitly excluding source material.
• c. For safeguards purposes, see the definition of nuclear material in the Safeguards Glossary [INTERNATIONAL ATOMIC ENERGY AGENCY, IAEA Safeguards Glossary (2022 Edition), IAEA, Vienna].

Definition

1. The deliberate physical movement of radioactive material (other than that forming part of the means of propulsion) from one place to another.

Scope notes

• a. The term transportation is also used, in particular in US English or where there is a need to distinguish this meaning of transport from meaning (2).
• c. In some Nuclear Security Series publications addressing transport of nuclear material, transport has also been defined as “International or domestic carriage of nuclear material by any means of transport, beginning with the departure from a nuclear facility of the shipper and ending with the arrival at a nuclear facility of the receiver” [Nuclear Security Recommendations on Physical Protection of Nuclear Material and Nuclear Facilities, INFCIRC/225/Revision 5, IAEA Nuclear Security Series No. 13, IAEA, Vienna (2011)].
• b. In the context of the Transport Regulations, transport comprises all operations and conditions associated with, and involved in, the movement of radioactive material; these include the design, manufacture, maintenance and repair of packaging, and the preparation, consigning, loading, carriage including in-transit storage, shipment after storage, unloading and receipt at the final destination of loads of radioactive material and packages.

Definition

A set of interrelated or interacting elements (system) for establishing policies and objectives and enabling the objectives to be achieved in an efficient and effective manner.

Scope notes

• a. The component parts of the management system include the organizational structure, resources and organizational processes.
• b. Management is defined (in ISO 9000) [INTERNATIONAL ORGANIZATION FOR STANDARDIZATION, Quality Management Systems — Fundamentals and Vocabulary, ISO 9000:2015, ISO, Geneva (2015).] as coordinated activities to direct and control an organization.
• c. The management system integrates all elements of an organization into one coherent system to enable all of the organization’s objectives to be achieved. These elements include the organizational structure, resources and processes.
• d. Personnel, equipment and organizational culture as well as the documented policies and processes form parts of the management system.
• e. The organization’s processes have to address the totality of the requirements on the organization as established in, for example, IAEA safety standards and other international codes and standards.

Definition

A planar or gently curved fracture surface or zone of the Earth across which there has been relative displacement.

Definition

A single coherent management system for facilities and activities in which all the component parts of an organization are integrated to enable the organization’s objectives to be achieved.

Scope notes

• These component parts of an organization that are integrated include the organizational structure, resources and organizational processes.

Definition

A geological fault that has a significant potential for displacement at or near the ground surface.

Scope notes

• A geological fault is to be considered a capable fault if, on the basis of geological, geophysical, geodetic or seismological data (including paleoseismoloical and geomorphological data), one or more of the following conditions applies: (a) The geological fault shows evidence of past movement or movements (significant deformations and/or dislocations) of a recurring nature within such a period that it is reasonable to infer that further movements at or near the surface could occur. (b) A structural relationship with a known capable fault has been demonstrated such that movement of the one may cause movement of the other at or near the surface. (c) The maximum potential earthquake associated with a seismogenic structure is sufficiently large and at such a depth that it is reasonable to infer that, in the geodynamic setting of the site, movement at or near the surface could occur. [INTERNATIONAL ATOMIC ENERGY AGENCY, Seismic Hazards in Site Evaluation for Nuclear Installations, IAEA Safety Standards Series No. SSG-9, IAEA, Vienna (2010).]
• In highly active areas, where both earthquake data and geological data consistently reveal short earthquake recurrence intervals, periods of the order of tens of thousands of years may be appropriate for the assessment of capable faults. In less active areas, it is likely that much longer periods may be required.

Definition

Analysis of those factors at a site that could affect the safety of a facility or activity on that site.

Scope notes

• a. This includes site characterization, consideration of factors that could affect safety features of the facility or activity so as to result in a release of radioactive material and/or could affect the dispersion of such material in the environment, as well as population and access issues relevant to safety (e.g. feasibility of evacuation, location of people and resources).
• b. The analysis for a site of the origins of external events that could give rise to hazards with potential consequences for the safety of a nuclear power plant constructed on that site.
• c. For a nuclear power plant, site evaluation typically involves the following stages:
  • (a) Site selection stage. One or more preferred candidate sites are selected after the investigation of a large region, the rejection of unsuitable sites, and screening and comparison of the remaining sites.
  • (b) Site characterization stage. This stage is further subdivided into: - Site verification, in which the suitability of the site to host a nuclear power plant is verified mainly according to predefined site exclusion criteria; - Site confirmation, in which the characteristics of the site necessary for the purposes of analysis and detailed design are determined.
  • (c) Pre-operational stage. Studies and investigations begun in the previous stages are continued after the start of construction and before the start of operation of the plant, to complete and refine the assessment of site characteristics. The site data obtained allow a final assessment of the simulation models used in the final design.
  • (d) Operational stage. Appropriate safety related site evaluation activities are carried out throughout the lifetime of the facility, mainly by means of monitoring and periodic safety review.

Definition

An analysis to estimate the uncertainties and error bounds of the quantities involved in, and the results from, the solution of a problem.

Definition

A volcanic process or phenomenon that can have an adverse effect on people or infrastructure.

Scope notes

• In the more restricted context of risk assessment, it is the probability of occurrence, within a specific period of time in a given area, of a potentially damaging volcanic event of a given intensity value (e.g. thickness of tephra fallout).

Definition

The process of assessing the remaining sites by screening and comparing them on the basis of safety and other considerations to select one or more preferred candidate sites.

Scope notes

• b. The terms siting, design, construction, commissioning, operation and decommissioning are normally used to delineate the six major stages of the lifetime of an authorized facility and of the associated licensing process. In the special case of disposal facilities for radioactive waste, decommissioning is replaced in this sequence by closure.
• c. See also site evaluation.
• a. The siting process for a disposal facility is particularly crucial to its long term safety; it may therefore be a particularly extensive process, and is divided into the following stages:
  • - Concept and planning;
  • - Area survey;
  • - Site characterization;
  • - Site confirmation

Definition

A naturally occurring vent at the Earth’s surface through which lava, solid rock and associated gases and liquid water can erupt.

Scope notes

• The edifice that is built by the explosive or effusive accumulation of these products over time is also a volcano.

Definition

The process of identifying candidate sites for a nuclear installation after the investigation of a large region and the rejection of unsuitable sites.

Definition

A volcano that has a credible likelihood of undergoing future activity and producing hazardous phenomena, including non-eruptive phenomena, during the lifetime of a nuclear installation concerned, and which may potentially affect the site.

Scope notes

• Hierarchical criteria for determining whether a volcano or volcanic field is a capable volcano or a capable volcanic field are: (i) evidence of contemporary volcanic activity or active near surface processes associated with magmatism for any volcano in the geographical region; (ii) Holocene volcanic activity for any volcano within the geographical region; and (iii) some evidence of potential for activity, such as recurrence rates of volcanism greater than 10–7 per year, and the potential to produce hazardous phenomena that may affect the site vicinity [INTERNATIONAL ATOMIC ENERGY AGENCY, Volcanic Hazards in Site Evaluation for Nuclear Installations, IAEA Safety Standards Series No. SSG-21, IAEA, Vienna (2012).].

Definition

The process of selecting a suitable site for a facility, including appropriate assessment and definition of the related design bases.

Scope notes

• The siting process for a nuclear installation generally consists of site survey and site selection.
• The terms siting, design, construction, commissioning, operation and decommissioning are normally used to delineate the six major stages of the lifetime of an authorized facility and of the associated licensing process. In the special case of disposal facilities for radioactive waste, decommissioning is replaced in this sequence by closure.

Definition

1. The state or condition of being subject to irradiation.

Scope notes

• Caution: Exposure should not be used as a synonym for dose. Dose is a measure of the effects of exposure.
• Exposure to ionizing radiation can be broadly divided into categories of exposure (see categories of exposure) according to the status of the individual(s) exposed; into exposure situations according to the circumstances of the exposure; and according to the source of the exposure.

Definition

The process of manufacturing and assembling the components of a facility, the carrying out of civil works, the installation of components and equipment, and the performance of associated tests.

Scope notes

• The terms siting, design, construction, commissioning, operation and decommissioning are normally used to delineate the six major stages of the lifetime of an authorized facility and of the associated licensing process. In the special case of disposal facilities for radioactive waste, decommissioning is replaced in this sequence by closure.

Definition

These include: nuclear facilities; irradiation installations; some mining and raw material processing facilities such as uranium mines; radioactive waste management facilities; and any other places where radioactive material is 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.

Scope notes

• ‘Facilities’ includes:
  • (a) Nuclear power plants;
  • (b) Other reactors (such as research reactors and critical assemblies);
  • (c) Enrichment facilities and nuclear fuel fabrication facilities;
  • (d) Conversion facilities used to generate uranium hexafluoride (UF₆);
  • (e) Storage facilities and reprocessing plants for irradiated fuel;
  • (f) Facilities for radioactive waste management where radioactive waste is treated, conditioned, stored or disposed of;
  • (g) Any other places where radioactive materials are produced, processed, used, handled or stored;
  • (h) Irradiation installations for medical, industrial, research and other purposes, and any places where radiation generators are installed;
  • (i)Facilities where the mining and processing of radioactive ores (such as ores of uranium and thorium) are carried out

Definition

2. These include: the production, use, import and export of radiation sources for industrial, research and medical purposes; the transport of radioactive material; the decommissioning of facilities; radioactive waste management activities such as the discharge of effluents; and some aspects of the remediation of sites affected by residues from past activities.

Scope notes

• The intention is to include any human activity that introduces additional sources of radiation or additional exposure pathways, or that modifies the network of exposure pathways from existing sources, so as to increase the exposure or the likelihood of exposure of people or the number of people exposed.
• ‘Activities’ includes:
  • (a) The production, use, import and export of radiation sources for medical, industrial, research and other purposes;
  • (b) The transport of radioactive material;
  • (c) The decommissioning of facilities and the closure of repositories for radioactive waste;
  • (d) The close-out of facilities where the mining and processing of radioactive ores was carried out;
  • (e) Activities for radioactive waste management such as the discharge of effluents;
  • (f) The remediation of sites affected by residues from past activities

Definition

Loss of the ability of a structure, system or component to function within acceptance criteria.

Scope notes

• a. Caution: Note that the structure, system or component is considered to fail when it becomes incapable of functioning, whether or not this is needed at that time.
• b. Caution: 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.
• c. A failure may be the result of, for example, a hardware fault, a software fault, a system fault, an operator error or a maintenance error.

Definition

The holding of radioactive sources, radioactive material, spent fuel or radioactive waste in a facility that provides for their/its containment, with the intention of retrieval.

Scope notes

• a. Generalized from the Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management [Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management, INFCIRC/546, IAEA, Vienna (1997).], the Code of Conduct on the Safety and Security of Radioactive Sources [Code of Conduct on the Safety and Security of Radioactive Sources, IAEA, Vienna (2004).] and [INTERNATIONAL ATOMIC ENERGY AGENCY, Predisposal Management of Radioactive Waste, IAEA Safety Standards Series No. GSR Part 5, IAEA, Vienna (2009).].
• b. Caution: Storage is by definition an interim measure, and the term interim storage would therefore be appropriate only to refer to short term temporary storage when contrasting this with the longer term fate of the waste.
• c. Caution: Storage as defined above should not be described as interim storage.
• d. Caution: In many cases, the only element of this definition that is important is the distinction between disposal (with no intent to retrieve) and storage (with intent to retrieve).
• f. For storage in a combined storage and disposal facility, for which a decision may be made at the time of its closure whether to remove the waste stored during the operation of the storage facility or to dispose of it by encasing it in concrete, the question of intention of retrieval may be left open until the time of closure of the facility.
• g. Contrasted with disposal.
• e. In such cases, a definition is not necessary; the distinction can be made in the form of a footnote at the first use of the term disposal or storage (e.g. “Use of the term disposal indicates that there is no intention to retrieve the waste. If retrieval of the waste at any time in the future is intended, the term storage is used.”).

Definition

Strictly: relating to a nucleus; relating to or using energy released in nuclear fission or fusion. (adjective)

Scope notes

• a. Caution: The adjective ‘nuclear’ is used in many phrases to modify a noun that it cannot logically modify. It must be borne in mind that the meaning of such phrases may be unclear (as opposed to nuclear).
• b. Caution: The phrases may therefore need to be explained, and their usage may be open to misunderstanding, misrepresentation or mistranslation.
• c. Caution: Such phrases include: nuclear accident; nuclear community; nuclear emergency; nuclear facility; nuclear fuel; nuclearincident; nuclear installation; nuclear material; nuclear medicine; (a) nuclear power; nuclear safety; and nuclear security.

Definition

Fissionable nuclear material in the form of fabricated elements for loading into the reactor core of a civil nuclear power plant or research reactor.

Definition

Events unconnected with the operation of a facility or the conduct of an activity that could have an effect on the safety of the facility or activity.

Scope notes

• a. Typical examples of external events for nuclear facilities include earthquakes, tornadoes, tsunamis and aircraft crashes.
• b. In the case of safety assessment for long term safety in waste management, a relevant external event is one that could have an effect on the functioning of multiple barriers.

Definition

A general term encompassing all of the elements (items) of a facility or activity that contribute to protection and safety, except human factors.

Scope notes

• Human factors may be reflected in structures, systems and components in so far as ergonomics — the study of people’s efficiency in their work setting — is an element in their design.

Definition

The area immediately surrounding a proposed site area in which population distribution and density, and land and water uses, are considered with respect to their impact on planning effective emergency response actions.

Scope notes

• a. Used in the context of siting of facilities.
• b. This is the area that would be the emergency planning zones if the facility were in place.

Definition

A general term encompassing nuclear facilities, uses of all sources of ionizing radiation, all radioactive waste management activities, transport of radioactive material and other practices or circumstances in which people may be subject to exposure to radiation from naturally occurring or artificial sources.

Scope notes

• a. The term facilities and activities is intended to provide an alternative to the terminology of sources and practices (or interventions) to refer to general categories of situations.
• b. 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.
• c. The term facilities and activities is very general, and includes those for which little or no 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.
• d. In the Fundamental Safety Principles (IAEA Safety Fundamentals), the term ‘facilities and activities — existing and new — utilized for peaceful purposes’ is abbreviated for convenience to facilities and activities as a general term encompassing any human activity that may cause people to be exposed to radiation risks arising from naturally occurring or artificial sources (see EUROPEAN ATOMIC ENERGY COMMUNITY, INTERNATIONAL ATOMIC ENERGY AGENCY, FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, INTERNATIONAL LABOUR ORGANIZATION, INTERNATIONAL MARITIME ORGANIZATION, OECD NUCLEAR ENERGY AGENCY, PAN AMERICAN HEALTH ORGANIZATION, UNITED NATIONS ENVIRONMENT PROGRAMME, WORLD HEALTH ORGANIZATION, Fundamental Safety Principles, IAEA Safety Standards Series No. SF-1, IAEA, Vienna (2006), para. 1.9).
• f. Facilities and activities are listed as follows in [INTERNATIONAL ATOMIC ENERGY AGENCY, Safety Assessment for Facilities and Activities, IAEA Safety Standards Series No. GSR Part 4 (Rev. 1), IAEA, Vienna (2015)]:

  ‘Facilities’ includes:

  • (a) Nuclear power plants;
  • (b) Other reactors (such as research reactors and critical assemblies);
  • (c) Enrichment facilities and nuclear fuel fabrication facilities;
  • (d) Conversion facilities used to generate uranium hexafluoride (UF₆);
  • (e) Storage facilities and reprocessing plants for irradiated fuel;
  • (f) Facilities for radioactive waste management where radioactive waste is treated, conditioned, stored or disposed of;
  • (g) Any other places where radioactive materials are produced, processed, used, handled or stored;
  • (h) Irradiation installations for medical, industrial, research and other purposes, and any places where radiation generators are installed;
  • (i)Facilities where the mining and processing of radioactive ores (such as ores of uranium and thorium) are carried out

  ‘Activities’ includes:

  • (a) The production, use, import and export of radiation sources for medical, industrial, research and other purposes;
  • (b) The transport of radioactive material;
  • (c) The decommissioning of facilities and the closure of repositories for radioactive waste;
  • (d) The close-out of facilities where the mining and processing of radioactive ores was carried out;
  • (e) Activities for radioactive waste management such as the discharge of effluents;
  • (f) The remediation of sites affected by residues from past activities
• e. For safeguards purposes, see the definition of facility in the Safeguards Glossary [IAEA Safeguards Glossary (2022 Edition), IAEA, Vienna].

Definition

A passive elements (e.g. buildings, vessels, shielding).

Definition

1. Assessment of all aspects of a practice that are relevant to protection and safety; for an authorized facility, this includes siting, design and operation of the facility.

Scope notes

• b. See also probabilistic safety assessment (PSA)
• a. This will normally include risk assessment (1).

Definition

All activities performed to achieve the purpose for which an authorized facility was constructed.

Scope notes

• c. See also abnormal operation and normal operation.
• a. For a nuclear power plant, this includes maintenance, refuelling, in-service inspection and other associated activities.
• b. The terms siting, design, construction, commissioning, operation and decommissioning are normally used to delineate the six major stages of the lifetime of an authorized facility and of the associated licensing process. In the special case of disposal facilities for radioactive waste, decommissioning is replaced in this sequence by closure.

Definition

Item that is designed to perform a safety function for or that has a safety function for design extension conditions.

Scope notes

• The concept of safety features for design extension conditions also applies for research reactors and nuclear fuel cycle facilities.

Definition

Any person or organization applying for authorization or authorized and/or responsible for safety when undertaking activities or in relation to any nuclear facilities or sources of ionizing radiation.

Scope notes

• a. In some publications in the Nuclear Security Series, this term has been also defined as “Any person, organization, or government entity licensed or authorized to undertake the operation of an associated facility or to perform an associated activity” [Nuclear Security Recommendations on Physical Protection of Nuclear Material and Nuclear Facilities, INFCIRC/225/Revision 5, IAEA Nuclear Security Series No. 13, IAEA, Vienna (2011)].
• e. Synonymous with operating organization.
• d. Operator includes either those who are directly in control of a facility or an activity during use or transport of a source (such as radiographers or carriers) or, in the case of a source not under control (such as a lost or illicitly removed source or a re-entering satellite), those who were responsible for the source before control over it was lost.
• c. Caution: Operator is sometimes used to refer to operating personnel (e.g. control room operators). If used in this way, particular care should be taken to ensure that there is no possibility of confusion.
• b. Operator includes, inter alia, private individuals, governmental bodies, consignors or carriers, licensees, hospitals, self-employed persons.

Definition

1. Exhibiting radioactivity; emitting or relating to the emission of ionizing radiation or particles. (adjective)

Scope notes

• Caution: This is the ‘scientific’ definition, and should not be confused with the ‘regulatory’ definition (2).

Definition

A systematic reassessment of the safety of an existing facility (or activity) carried out at regular intervals to deal with the cumulative effects of ageing, modifications, operating experience, technical developments and siting aspects, and aimed at ensuring a high level of safety throughout the service life of the facility (or activity).

Definition

An analytical or physical representation or quantification of a real system and the ways in which phenomena occur within that system, used to predict or assess the behaviour of the real system under specified (often hypothetical) conditions.

Definition

This term encompasses sub-terms such as depleted uranium, enriched uranium, high enriched uranium, low enriched uranium and natural uranium

Definition

1. The process, and the result, of analysing systematically and evaluating the hazards associated with sources and practices, and associated protection and safety measures.

Scope notes

• Assessment is often aimed at quantifying performance measures for comparison with criteria.
• In IAEA publications, assessment should be distinguished from analysis. Assessment is aimed at providing information that forms the basis of a decision on whether or not something is satisfactory. Various kinds of analysis may be used as tools in doing this. Hence an assessment may include a number of analyses.

Definition

Outside the site area.

Definition

1. The process and the result of developing a concept, detailed plans, supporting calculations and specifications for a facility and its parts.

Scope notes

• The terms siting, design, construction, commissioning, operation and decommissioning are normally used to delineate the six major stages of the lifetime of an authorized facility and of the associated licensing process. In the special case of disposal facilities for radioactive waste, decommissioning is replaced in this sequence by closure.

Definition

[A radiation generator, or a radioactive source or other radioactive material outside the nuclear fuel cycles of research and power reactors.]

Scope notes

• Caution: Defined in the 2001 edition of the Code of Conduct on the Safety and Security of Radioactive Sources, but not included in the 2004 edition (see Code of Conduct on the Safety and Security of Radioactive Sources, IAEA, Vienna (2004).).

Definition

The process by means of which systems and components of facilities and activities, having been constructed, are made operational and verified to be in accordance with the design and to have met the required performance criteria.

Scope notes

• Commissioning may include both non-nuclear and/or non-radioactive and nuclear and/or radioactive testing.
• The terms siting, design, construction, commissioning, operation and decommissioning are normally used to delineate the six major stages of the lifetime of an authorized facility and of the associated licensing process. In the special case of disposal facilities for radioactive waste, decommissioning is replaced in this sequence by closure.

Definition

Within the site area.

Definition

1. Administrative and technical actions directed at a disposal facility at the end of its operating lifetime — for example, covering of the disposed waste (for a near surface disposal facility) or backfilling and/or sealing (for a geological disposal facility and the passages leading to it) — and the termination and completion of activities in any associated structures.

Scope notes

• For other types of facilities, the term decommissioning is used.
• The terms siting, design, construction, commissioning, operation and decommissioning are normally used to delineate the six major stages of the lifetime of an authorized facility and of the associated licensing process. In the special case of disposal facilities for radioactive waste, decommissioning is replaced in this sequence by closure.

Definition

An instance of severely abnormal conditions caused by an abrupt transition from one status of a facility to another following a small deviation in a parameter or a small variation in an input value.

Scope notes

• In a nuclear power plant or nuclear fuel cycle facility, a cliff edge effect is an instance of severely abnormal facility behaviour caused by an abrupt transition from one facility status to another following a small deviation in a facility parameter, and thus a sudden large variation in facility conditions in response to a small variation in an input.

Definition

The potential for harm or other detriment, especially for radiation risks; a factor or condition that might operate against safety.

Definition

Any substance, whether processed, semi-processed or raw, that is intended for human consumption.

Scope notes

• This includes foodstuffs and drink (other than fresh water), chewing gum and substances used in the preparation or processing of food; it does not include cosmetics, tobacco or drugs. Consumption in this context refers to ingestion.

Definition

Caution: When used in IAEA publications, the term radiation usually refers to ionizing radiation only. The IAEA has no statutory responsibilities in relation to non-ionizing radiation.

Scope notes

• Ionizing radiation can be divided into low linear energy transfer radiation and high linear energy transfer radiation (as a guide to its relative biological effectiveness), or into strongly penetrating radiation and weakly penetrating radiation (as an indication of its ability to penetrate shielding or the human body).

Definition

1. For legal and regulatory purposes, waste that contains, or is contaminated with, radionuclides at activity concentrations greater than clearance levels as established by the regulatory body.

Scope notes

• a. In effect, radioactive material in gaseous, liquid or solid form for which no further use is foreseen.
• b. Caution: It should be recognized that this definition is purely for regulatory purposes, and that material with activity concentrations equal to or less than clearance levels is radioactive from a physical viewpoint, although the associated radiological hazards are considered negligible. See radioactive, radioactive material, radioactive substance.
• c. Waste should be used in the singular unless reference is expressly being made to the presence of various types of waste.

Definition

Assessment of the expected radiological impacts of facilities and activities on the environment for the purposes of protection of the public and protection of the environment against radiation risks.

Definition

For the purposes of radiation protection, radiation capable of producing ion pairs in biological material(s).

Definition

The achievement of proper operating conditions, prevention of accidents and mitigation of accident consequences, resulting in protection of workers, the public and the environment from undue radiation risks.

Scope notes

• a. Often abbreviated to safety in IAEA publications on nuclear safety. Safety means nuclear safety unless otherwise stated, in particular when other types of safety (e.g. fire safety, conventional industrial safety) are also being discussed. See protection and safety for a discussion of the relationship between nuclear safety and radiation protection.
• b. There is not an exact distinction between the general terms safety and security. In general, security is concerned with intentional actions by people that could cause or threaten harm to other people; safety is concerned with the broader issue of harmful consequences to people (and to the environment) arising from exposure to radiation, whatever the cause.
• c. The interaction between arrangements for security and arrangements for safety depends on the context. Areas in which arrangements for safety and arrangements for security interact include, for example: the regulatory infrastructure; engineering provisions in the design and construction of nuclear installations and other facilities; controls on access to nuclear installations and other facilities; the categorization of radioactive sources; source design; the security of the management of radioactive sources and radioactive material; the recovery of sources that are not under regulatory control; emergency response plans; and radioactive waste management.
• d. See protection and safety for a discussion of the relationship between nuclear safety and radiation protection.

Definition

The movement of radionuclides in the environment as a result of natural processes.

Scope notes

• Most commonly, movement of radionuclides in association with groundwater flow.

Definition

A postulated or assumed set of conditions and/or events.

Scope notes

• See event.
• Most commonly used in analysis or assessment to represent possible future conditions and/or events to be modelled, such as possible accidents at a nuclear facility, or the possible future evolution of a disposal facility and its surroundings. A scenario may represent the conditions at a single point in time or a single event, or a time history of conditions and/or events (including processes)

Definition

A type of analysis aimed at eliminating from further consideration factors that are less significant for protection or safety in order to concentrate on the more significant factors.

Scope notes

• a. This is typically achieved by consideration of very pessimistic hypothetical scenarios.
• b. Screening is usually conducted at an early stage in order to narrow the range of factors needing detailed consideration in an analysis or assessment.

Definition

3. Determination of the character of something.

Scope notes

• This is the standard dictionary definition and would not need to be included in an individual glossary. It is included here only to distinguish the usual usage from the more restricted usage indicated in (1) and (2).

Definition

1. Planned and controlled release of (usually gaseous or liquid) radioactive substances to the environment.

Scope notes

• Strictly, the act or process of releasing the radioactive substances, but also used to describe the radioactive substances released.

Definition

The presence of two or more independent (redundant) systems or components to perform an identified function, where the different systems or components have different attributes so as to reduce the possibility of common cause failure, including common mode failure.

Scope notes

• Examples of such attributes are: different operating conditions different working principles or different design teams (which provide functional diversity), and different sizes of equipment, different manufacturers, and types of equipment (which provide diversity of equipment) that use different physical methods (which provide physical diversity).
• When the term diversity is used with an additional attribute, the term diversity indicates the general meaning ‘existence of two or more different ways or means of achieving a specified objective’, while the attribute indicates the characteristics of the different ways applied, e.g. functional diversity, equipment diversity, signal diversity, functional diversity. Application of diversity at the level of functions in applications in process engineering (e.g. for the actuation of a trip on both a pressure limit and a temperature limit).

Definition

Process of determining whether a system or component is suitable for operational use.

Scope notes

• a. Qualification is generally performed in the context of a specific set of qualification requirements for the specific facility and class of system and for the specific application.
• c. Qualification may rely on activities performed outside the framework of a specific facility design (this is called ‘generic qualification’ or ‘prequalification’).
• d. Prequalification may significantly reduce the necessary effort in facility specific qualification; however, the application specific qualification requirements must still be met and be shown to be met.
• b. Qualification may be accomplished in stages: for example, first, by the qualification of pre-existing equipment (usually early in the system realization process), then, in a second step, by the qualification of the integrated system (i.e. in the final realized design).
• e. See also harsh environment, mild environment.

Definition

The spreading of radionuclides in air (aerodynamic dispersion) or water (hydrodynamic dispersion) resulting mainly from physical processes affecting the velocity of different molecules in the medium.

Scope notes

• a. Often used in a more general sense combining all processes (including molecular diffusion) that result in the spreading of a plume. The terms atmospheric dispersion and hydrodynamic dispersion are used in this more general sense for plumes in air and water, respectively.
• b. In usual language synonymous with dispersal, but dispersion is mostly used more specifically as defined above, whereas dispersal is typically (though not universally) used as a more general expression.

Definition

Protection and conservation of: non-human species, both animal and plant, and their biodiversity; environmental goods and services such as the production of food and feed; resources used in agriculture, forestry, fisheries and tourism; amenities used in spiritual, cultural and recreational activities; media such as soil, water and air; and natural processes such as carbon, nitrogen and water cycles.

Scope notes

• See also environment.

Definition

That which is established or required by the Fundamental Safety Principles (IAEA Safety Fundamentals) [EUROPEAN ATOMIC ENERGY COMMUNITY, INTERNATIONAL ATOMIC ENERGY AGENCY, FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, INTERNATIONAL LABOUR ORGANIZATION, INTERNATIONAL MARITIME ORGANIZATION, OECD NUCLEAR ENERGY AGENCY, PAN AMERICAN HEALTH ORGANIZATION, UNITED NATIONS ENVIRONMENT PROGRAMME, WORLD HEALTH ORGANIZATION, Fundamental Safety Principles, IAEA Safety Standards Series No. SF-1, IAEA, Vienna (2006).] or IAEA Safety Requirements publications or by (national or international) laws or regulations.

Scope notes

• Caution: In IAEA publications, requirement (and ‘required’ and other words deriving from the verb ‘to require’) should be used in this sense only. Care should be taken to avoid confusion: the use of ‘requirement’ in the more general sense of something that is necessary should be avoided.
• Requirements, including numbered ‘overarching’ requirements, are expressed as ‘shall’ statements. Reported (quoted) requirements, e.g. in a Safety Guide, are reported using a formulation such as ‘it is required to…’.

Definition

States defined under normal operation and anticipated operational occurrences.

Scope notes

• Some States and organizations use the term operating conditions (in contrast to accident conditions) for this concept.

Definition

The integrated set of infrastructural elements, put in place at the preparedness stage that are necessary to provide the capability for performing a specified function or task required in response to a nuclear or radiological emergency.

Scope notes

• These elements may include: authorities and responsibilities, organization, coordination, personnel, plans, procedures, facilities, equipment or training.

Definition

Any person who works, whether full time, part time or temporarily, for an employer and who has recognized rights and duties in relation to occupational radiation protection.

Scope notes

• A self-employed person is regarded as having the duties of both an employer and a worker.

Definition

[A nuclear reactor used mainly for the generation and utilization of neutron flux and ionizing radiation for research and other purposes, including experimental facilities associated with the reactor and storage, handling and treatment facilities for radioactive material on the same site that are directly related to safe operation of the research reactor. Facilities commonly known as critical assemblies are included.]

Scope notes

• Caution: This definition is particular to the Code of Conduct on the Safety of Research Reactors [Code of Conduct on the Safety of Research Reactors, IAEA, Vienna (2006). ].

Definition

1. An action for the purposes of avoiding or reducing doses that might otherwise be received in an emergency exposure situation or an existing exposure situation.

Scope notes

• This is related to radiation protection (see protection (1), and protection and safety).

Definition

Any unintended event, including operating errors, equipment failures, initiating events, accident precursors, near misses or other mishaps, or unauthorized act, malicious or non-malicious, the consequences or potential consequences of which are not negligible from the point of view of protection and safety.

Scope notes

• b. Caution: The word incident is sometimes used, in INES 2008 Manual [INTERNATIONAL ATOMIC ENERGY AGENCY, INES: The International Nuclear and Radiological Event Scale User’s Manual, 2008 Edition, IAEA, Vienna (2013).], to describe events that are, in effect, minor accidents, i.e. that are distinguished from accidents only in terms of being less severe.
• c. Caution: This is a distinction with little basis in general usage, in which an incident can be minor or major, just as an accident can; however, unlike an accident, an incident can be caused intentionally.
• d. The definition of incident given was derived on the basis of the entries for accident and event and the explanation of the term incident given in SF-1 [EUROPEAN ATOMIC ENERGY COMMUNITY, INTERNATIONAL ATOMIC ENERGY AGENCY, FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, INTERNATIONAL LABOUR ORGANIZATION, INTERNATIONAL MARITIME ORGANIZATION, OECD NUCLEAR ENERGY AGENCY, PAN AMERICAN HEALTH ORGANIZATION, UNITED NATIONS ENVIRONMENT PROGRAMME, WORLD HEALTH ORGANIZATION, Fundamental Safety Principles, IAEA Safety Standards Series No. SF-1, IAEA, Vienna (2006).].
• a. See also event and International Nuclear and Radiological Event Scale.

Definition

These include: the production, use, import and export of radiation sources for industrial, research and medical purposes; the transport of radioactive material; the decommissioning of facilities; radioactive waste management activities such as the discharge of effluents; the remediation of sites affected by residues from past activities.

Scope notes

• The term facilities and activities is very general, and includes those for which little or no 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.

Definition

These include: nuclear facilities; irradiation installations; some mining and raw material processing facilities such as uranium mines; radioactive waste management facilities; and any other places where radioactive material is 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.

Scope notes

• The term facilities and activities is very general, and includes those for which little or no 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.

Definition

1. Material designated in national law or by a regulatory body as being subject to regulatory control because of its radioactivity.

Scope notes

• a. Some publications in the Nuclear Security Series extend the definition, for the avoidance of doubt, to indicate that “In the absence of such a designation by a State, any material for which protection is required by the current version of the International Basic Safety Standards” [Objective and Essential Elements of a State’s Nuclear Security Regime, IAEA Nuclear Security Series No. 20, IAEA, Vienna (2013)].
• b. Caution: This is the ‘regulatory’ meaning of radioactive (2), and should not be confused with the ‘scientific’ meaning of radioactive (1): ‘exhibiting radioactivity; emitting or relating to the emission of ionizing radiation or particles’.
• c. Caution: The ‘scientific’ meaning of radioactive (1) — as in radioactive substance — refers only to the presence of radioactivity, and gives no indication of the magnitude of the hazard involved.
• d. Caution: The term radioactive substance is also used to indicate that the ‘scientific’ meaning of radioactive (see radioactive (1)) is intended, rather than the ‘regulatory’ meaning of radioactive (see radioactive (2)) suggested by the term radioactive material.
• e. Caution: However, in some States the term radioactive substance is used for the ‘regulatory’ purpose. It is therefore essential that any such distinctions in meaning are clarified.
• f.Caution: In some Nuclear Security Series publications (e.g. Refs [Nuclear Security Recommendations on Physical Protection of Nuclear Material and Nuclear Facilities, INFCIRC/225/Revision 5, IAEA Nuclear Security Series No. 13, IAEA, Vienna (2011), Nuclear Security Recommendations on Radioactive Material and Associated Facilities, IAEA Nuclear Security Series No. 14, IAEA, Vienna (2011)]) it is stated or implied that radioactive substance is synonymous with radioactive material, in order to confirm consistency with the 2005 CPPNM Amendment [Amendment to the Convention on the Physical Protection of Nuclear Material, INFCIRC/274/Rev. 1/Mod. 1 (Corrected), IAEA, Vienna (2021).]. In contexts related to the CPPNM Amendment, the terms are synonymous, but in general they may have different meanings.
• g. In regulatory terminology in some States, radioactive material ceases to be radioactive material when it becomes radioactive waste; the term radioactive substance is used to cover both, that is radioactive substance includes radioactive material and radioactive waste.
• h. Caution:Radioactive material should be used in the singular unless reference is expressly being made to the presence of various types of radioactive material.

<h2>Definition</h2><p>1. All administrative and operational <i>activities</i> involved in the handling, <i>pretreatment</i>, <i>treatment</i>, <i>conditioning</i>, <i>transport</i>, <i>storage</i> and <i>disposal</i> of <i>radioactive waste</i><br/> <img src="https://vocabulary.iaea.org/https://nucleus.iaea.org/sites/nss-oui/Figures/i_8960bfd7-fd63-4f8f-a6b1-ee89e5ede97b.JPG" style="width: 480px;"></p>

Definition

2. Continuous or periodic measurement of radiological or other parameters or determination of the status of a structure, system or component.

Scope notes

• a. Sampling may be involved as a preliminary step to measurement.
• b. Although the concept is not fundamentally different from definition (1), this definition is more suited to the types of monitoring concerned primarily with safety (i.e. keeping sources under control) rather than with protection (i.e. controlling exposure).
• c. This definition is particularly relevant to monitoring the status of a nuclear installation by tracking plant variables, or monitoring the long term performance of a waste disposal facility by tracking variables such as water fluxes.
• d. These examples differ from definition (1) in that the routine measurements are themselves of no particular interest; the monitoring is only intended to detect unexpected deviations if they occur.

Definition

2. The movement of something as a result of being carried by a medium.

Scope notes

• A general term used when a number of different processes are involved. The most common examples are heat transport — a combination of advection, convection, etc., in a cooling medium — and radionuclide transport in the environment — which could include processes such as advection, diffusion, sorption and uptake.

Definition

1. Nuclear fuel removed from a reactor following irradiation that is no longer usable in its present form because of depletion of fissile material, poison buildup or radiation damage.

Scope notes

• The participle ‘spent’ suggests that spent fuel cannot be used as fuel in its present form (e.g. as in spent source). In practice, however (as in (2) below), spent fuel is commonly used to refer to fuel that has been used as fuel but will no longer be used, whether or not it could be used (and that might more accurately be termed ‘disused fuel’).

Definition

The range of conditions and events taken explicitly into account in the design of structures, systems and components and equipment of a facility, according to established criteria, such that the facility can withstand them without exceeding authorized limits.

Scope notes

• Used as a noun, with the definition above. Also often used as an adjective, applied to specific categories of conditions or events to mean ‘included in the design basis’; as, for example, in design basis accident, design basis external events and design basis earthquake.

Definition

A process or operation, the purpose of which is to extract radioactive isotopes from spent fuel for further use.

Definition

The conditions under which people, animals and plants live or develop and which sustain all life and development; especially such conditions as affected by human activities.

Scope notes

• See also protection of the environment

Definition

A comprehensive, structured approach to identifying failure scenarios, constituting a conceptual and mathematical tool for deriving numerical estimates of risk.

Scope notes

• Three levels of probabilistic safety assessment are generally recognized:
  • - Level 1 comprises the assessment of failures leading to determination of the frequency of fuel damage.
  • - Level 2 includes the assessment of containment response, leading, together with Level 1 results, to the determination of frequencies of failure of the containment and release to the environment of a given percentage of the reactor core’s inventory of radionuclides.
  • - Level 3 includes the assessment of off-site consequences, leading, together with the results of Level 2 analysis, to estimates of public risks
  (See, for example, [INTERNATIONAL NUCLEAR SAFETY ADVISORY GROUP, Probabilistic Safety Assessment, Safety Series No. 75-INSAG-6, IAEA, Vienna (1994).].)

Definition

The phenomenon whereby atoms undergo spontaneous random disintegration, usually accompanied by the emission of radiation.

Scope notes

• Caution: In IAEA publications, radioactivity should be used only to refer to the phenomenon.
• Caution: To refer to the physical quantity or to an amount of a radioactive substance, use activity.

Definition

Standards issued pursuant to Article III(A)(6)⁸ of the Statute of the IAEA [Statute of the International Atomic Energy Agency, IAEA, Vienna (1990).].

⁸ “[The Agency is authorized…] To establish or adopt, in consultation and, where appropriate, in collaboration with the competent organs of the United Nations and with the specialized agencies concerned, standards of safety for protection of health and minimization of danger to life and property (including such standards for labour conditions)…”

Scope notes

• a. Requirements, regulations, standards, rules, codes of practice or recommendations established to protect people and the environment against ionizing radiation and to minimize danger to life and property.
• b. Safety standards issued since 1997 in the IAEA Safety Standards Series are designated as Safety Fundamentals, Safety Requirements or Safety Guides.
• c. Some safety standards issued prior to 1997 in the (defunct) Safety Series were designated Safety Standards, Codes, Regulations or Rules.
• d. Furthermore, some publications issued in the (defunct) Safety Series were not safety standards, notably those designated Safety Practices or Procedures and Data.
• e. Other IAEA publications, such as Safety Reports and TECDOCs (most of which are issued pursuant to Article VIII of the Statute), are not safety standards.

Definition

That part of the environment normally inhabited by living organisms.

Scope notes

• In practice, the biosphere is not usually defined with great precision, but is generally taken to include the atmosphere and the Earth’s surface, including the soil and surface water bodies, seas and oceans, and their sediments. There is no generally accepted definition of the depth below the surface at which soil or sediment ceases to be part of the biosphere, but this might typically be taken to be the depth affected by basic human activities, in particular, farming.
• In the safety of radioactive waste management, in particular, the biosphere is normally distinguished from the geosphere.

Definition

The protection of people from harmful effects of exposure to ionizing radiation, and the means for achieving this.

Scope notes

• a. The International Commission on Radiological Protection and others use the term radiological protection, which is synonymous.
• b. The accepted understanding of the term radiation protection is restricted to protection of people. Suggestions to extend the definition to include the protection of non-human species or the protection of the environment are controversial.

Definition

1. An authority or a system of authorities designated by the government of a State as having legal authority for conducting the regulatory process, including issuing authorizations, and thereby regulating the nuclear, radiation, radioactive waste and transportsafety.

Scope notes

• a. The regulatory body is generally a national entity, established and empowered by law, whose organization, management, functions, processes, responsibilities and competences are subject to the requirements of IAEA safety standards.
• b. The national competent authority for the regulation of radioactive materialtransport (see INTERNATIONAL ATOMIC ENERGY AGENCY, Regulations for the Safe Transport of Radioactive Material — 2018 Edition, IAEA Safety Standards Series No. SSR-6 (Rev. 1), IAEA, Vienna (2018)) is included in this description, as is the regulatory body for protection and safety.
• c. Caution: Supersedes the term regulatory authority, which should not be used.

Definition

1. The process of determining whether the quality or performance of a product or service is as stated, as intended or as required.

Scope notes

• Verification is closely related to quality management and quality control.

Definition

The performance of actions to mitigate the consequences of an emergency for human life and health, property and the environment.

Scope notes

• The emergency response also provides a basis for the resumption of normal social and economic activity.

Definition

1. An examination, observation, surveillance, measurement or test undertaken to assess structures, systems and components and materials, as well as operational activities, technical processes, organizational processes, procedures and personnel competence.

Definition

An action to be taken in response to a nuclear or radiological emergency to mitigate the consequences of an emergency for human life and health, property and the environment.

Scope notes

• Also called emergency action.
• Emergency response actions comprise protective actions and other response actions.

Definition

The action or process of setting free or being set free, or of allowing or being allowed to move or flow freely.

Scope notes

• Caution: Release is used in both a physical ‘scientific’ sense (see discharge (1)) and a ‘regulatory’ sense (see clearance), as well as in the usual sense of, for example, a release of energy.

Definition

1. A source containing radioactive material that is used as a source of radiation.

<h2>Definition</h2><p>1. A hierarchical deployment of different levels of diverse equipment and <i>procedures</i> to prevent the escalation of <i>anticipated operational occurrences</i> and to maintain the effectiveness of physical <i>barriers</i> placed between a <i>radiation source</i> or <i>radioactive material</i> and <i>workers</i>, <i>members of the public</i> or the <i>environment</i>, in <i>operational states</i> and, for some <i>barriers</i>, in <i>accident conditions</i>.</p><h2>Scope notes</h2><ul><li>a. The objectives of <i>defence in depth</i> are: <ul><li>(a) To compensate for human induced <i>events</i> and <i>component</i> <i>failure</i>s; </li><li>(b) To maintain the effectiveness of the <i>barriers</i> by averting damage to the <i>facility</i> and to the <i>barriers</i> themselves; </li><li>(c) To protect <i>workers</i>, <i>members of the public</i> and the <i>environment</i> from harm in <i>accident conditions</i> in the <i>event</i> that these <i>barriers</i> are not fully effective</li></ul></li><li>c. Five levels of <i>defence in depth</i> are discussed in SSR-2/1 (Rev. 1) (See [INTERNATIONAL ATOMIC ENERGY AGENCY, Safety of Nuclear Power Plants: Design, IAEA Safety Standards Series No. SSR 2/1 (Rev. 1), IAEA, Vienna (2016).] for further information): <ul><li>(a) The purpose of the first level of defence is to prevent deviations from <i>normal operation</i> and the <i>failure</i> of <i>items important to safety</i>. </li><li>(b) The purpose of the second level of defence is to detect and control deviations from <i>normal operation</i> in order to prevent <i>anticipated operational occurrences</i> from escalating to <i>accident conditions</i>. </li><li>(c) The purpose of the third level of defence is to prevent damage to the reactor core and <i>releases</i> of <i>radioactive material</i> requiring <i>off-site</i> <i>protective actions</i> and to return the plant to a <i>safe state</i> by means of inherent and/or engineered <i>safety</i> features, <i>safety systems</i> and procedures. </li><li>(d) The purpose of the fourth level of defence is to prevent the progress of, and to mitigate the consequences of, <i>accidents</i> that result from <i>failure</i> of the third level of defence by preventing accident sequences that lead to <i>large release of radioactive material</i> or <i>early release of radioactive material</i> from occurring. </li><li>(e) The purpose of the fifth and final level of defence is to mitigate radiological consequences of a <i>large release of radioactive material</i> or an <i>early release of radioactive material</i> that could potentially result from an accident</li></ul></li><li>d. The International Nuclear Safety Group (INSAG) defined five levels of <i>defence in depth</i> (See [INTERNATIONAL NUCLEAR SAFETY ADVISORY GROUP, Defence in Depth in Nuclear Safety, INSAG Series No. 10, IAEA, Vienna (1996).] for further information): <ul><li>(a) Level 1: Prevention of <i>abnormal operation</i> and <i>failure</i>s. </li><li>(b) Level 2: <i>Control</i> of <i>abnormal operation</i> and detection of <i>failure</i>s. </li><li>(c) Level 3: <i>Control</i> of <i>accidents</i> within the <i>design basis</i>. </li><li>(d) Level 4: <i>Control</i> of severe plant conditions, including prevention of <i>accident</i> progression and mitigation of the consequences of <i>severe accidents</i>. </li><li>(e) Level 5: Mitigation of radiological consequences of significant <i>releases</i> of <i>radioactive material</i>.</li><li>e. The levels of defence are sometimes grouped into three <i>safety layers</i>: hardware, software and management <i>control</i>.</li><li>f. In the context of <i>waste disposal</i>, the term <i>multiple barriers</i> is used to describe a similar concept.</li><li>g. Note that <i>defence in depth</i> is used with a different meaning in the IAEA Nuclear Security Series in the context of <i>nuclear security</i>.</li><li>b. The Fundamental Safety Principles (IAEA Safety Fundamentals) [EUROPEAN ATOMIC ENERGY COMMUNITY, INTERNATIONAL ATOMIC ENERGY AGENCY, FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, INTERNATIONAL LABOUR ORGANIZATION, INTERNATIONAL MARITIME ORGANIZATION, OECD NUCLEAR ENERGY AGENCY, PAN AMERICAN HEALTH ORGANIZATION, UNITED NATIONS ENVIRONMENT PROGRAMME, WORLD HEALTH ORGANIZATION, Fundamental Safety Principles, IAEA Safety Standards Series No. SF-1, IAEA, Vienna (2006).] (para. 3.31) states that: “<i>Defence in depth</i> is implemented primarily through the combination of a number of consecutive and independent levels of protection that would have to fail before harmful effects could be caused to people or to the <i>environment</i>. If one level of protection or <i>barrier</i> were to fail, the subsequent level or <i>barrier</i> would be available. When properly implemented, <i>defence in depth</i> ensures that no single technical, human or organizational <i>failure</i> could lead to harmful effects, and that the combinations of <i>failure</i>s that could give rise to significant harmful effects are of very low probability. The independent effectiveness of the different levels of defence is a necessary element of <i>defence in depth</i>”.</li></ul>

Definition

1. The prevention and detection of, and response to, criminal or intentional unauthorized acts involving nuclear material, other radioactive material, associated facilities or associated activities.

Scope notes

• a. Often abbreviated to security in IAEA publications on nuclear security.
• b. Security of nuclear material for reasons relating to non-proliferation of nuclear weapons is outside the scope of the IAEA safety standards and of the IAEA Nuclear Security Series.
• e. The interaction between arrangements for security and arrangements for safety depends on the context. Areas in which arrangements for safety and arrangements for security interact include, for example: the regulatory infrastructure; engineering provisions in the design and construction of nuclear installations and other facilities; controls on access to nuclear installations and other facilities; the categorization of radioactive sources; source design; the security of the management of radioactive sources and radioactive material; the recovery of sources that are not under regulatory control; emergency response plans; and radioactive waste management.
• d. There is not an exact distinction between the general terms safety and security. In general, security is concerned with intentional actions by people that could cause or threaten harm to other people; safety is concerned with the broader issue of harmful consequences to people (and to the environment) arising from exposure to radiation, whatever the cause.
• c. Security of nuclear material for reasons relating to non-proliferation of nuclear weapons is outside the scope of the IAEA safety standards and of the IAEA Nuclear Security Series.

Definition

1. Any organization or person applying for authorization or authorized to operate an authorized facility or to conduct an authorized activity and responsible for its safety.

Scope notes

• a. Caution: Note that such an organization may be the operating organization before operation starts.
• c. Operating organization includes either those who are directly in control of a facility or an activity during use of a source (such as radiographers or carriers) or, in the case of a source not under control (such as a lost or illicitly removed source or a re-entering satellite), those who were responsible for the source before control over it was lost.
• b. This includes, inter alia, private individuals, governmental bodies, consignors or carriers, licensees, hospitals and self-employed persons.
• d. In practice, for an authorized facility, the operating organization is normally also the registrant or licensee. However, the separate terms are retained to refer to the two different capacities. See also operator

Definition

A route by which radiation or radionuclides can reach humans and cause exposure.

Scope notes

• An exposure pathway may be very simple, for example the external exposurepathway from airborne radionuclides, or a more complex chain, for example the internal exposurepathway from drinking milk from cows that ate grass contaminated with deposited radionuclides.

Definition

2. Any material containing radionuclides where both the activity concentration and the total activity in the consignment exceed the values specified in [paras 402-407 of the Transport Regulations]. (See INTERNATIONAL ATOMIC ENERGY AGENCY, Regulations for the Safe Transport of Radioactive Material — 2018 Edition, IAEA Safety Standards Series No. SSR-6 (Rev. 1), IAEA, Vienna (2018).)

Scope notes

• Caution: This usage is specific to the Transport Regulations, and should otherwise be avoided.

Definition

2. Designated in national law or by a regulatory body as being subject to regulatory control because of its radioactivity. (adjective)

Scope notes

• Caution: This is the ‘regulatory’ definition, and should not be confused with the ‘scientific’ definition (1).

Definition

The probability that a system or component or an item will meet its minimum performance requirements when called upon to do so, for a specified period of time and under stated operating conditions.

Scope notes

• See also availability.
• The reliability of a computer based system, for example, includes the reliability of hardware, which is usually quantified, and the reliability of software, which is usually a qualitative measure as there are no generally recognized means of quantifying the reliability of software.

Definition

Specified bounds on the value of a functional indicator or condition indicator used to assess the ability of a structure, system or component to perform its design function.

Definition

A feature or process on a volcano or within a volcanic field that is linked to the presence of magma and heat gases emanating from the Earth and their interaction with nearby crustal rocks or groundwater.

Scope notes

• Volcanic activity includes seismicity, fumarolic activity, high rates of heat flow, emission of ground gases, thermal springs, deformation, ground cracks, pressurization of aquifers and ash venting. The term includes volcanic unrest and volcanic eruption.

Definition

Evaluation of the potential hazards associated with the operation of a facility or the conduct of an activity.

Scope notes

• b. Safety analysis is often used interchangeably with safety assessment. However, when the distinction is important, safety analysis should be used as a documented process for the study of safety, and safety assessment should be used as a documented process for the evaluation of safety — for example, evaluation of the magnitude of hazards, evaluation of the performance of safety measures and judgement of their adequacy, or quantification of the overall radiological impact or safety of a facility or activity.
• a. The formal safety analysis is part of the overall safety assessment; that is, it is part of the systematic process that is carried out throughout the design process (and throughout the lifetime of the facility or the activity) to ensure that all the relevant safety requirements are met by the proposed (or actual) design.

Definition

A person, company, etc., with a concern or interest in the activities and performance of an organization, business, system, etc.

Scope notes

• a. The term interested party is used in a broad sense to mean a person or group having an interest in the performance of an organization.
• b. Those who can influence events may effectively become interested parties — whether their ‘interest’ is regarded as ‘genuine’ or not — in the sense that their views need to be considered.
• c. Interested parties would need to be specified as relevant.
• e. Caution: The term [stakeholder] is used in the same broad sense as interested party and the same provisos are necessary.
• f. Caution: The term [stakeholder] has disputed usage, and it is misleading and too all-encompassing for clear use. In view of the potential for misunderstanding and misrepresentation, use of the term is discouraged in favour of interested party.
• g. The Handbook on Nuclear Law [INTERNATIONAL ATOMIC ENERGY AGENCY, Handbook on Nuclear Law, IAEA, Vienna (2003).] states that: “Owing to the differing views on who has a genuine interest in a particular nuclear related activity, no authoritative definition of [stakeholder] has yet been offered, and no definition is likely to be accepted by all parties.”
• d. Interested parties have typically included the following: customers, owners, operators, employees, suppliers, partners and trade unions; the regulated industry or professionals; scientific bodies; governmental agencies or regulatory bodies (national, regional and local) whose responsibilities may cover nuclear energy; the media; the public (individuals, community groups and interest groups); and other States, especially neighbouring States that have entered into agreements providing for an exchange of information concerning possible transboundary impacts, or States involved in the export or import of certain technologies or materials. [INTERNATIONAL ATOMIC ENERGY AGENCY, Handbook on Nuclear Law, IAEA, Vienna (2003).]

Definition

aleatory uncertainty. Uncertainty inherent in a phenomenon.

epistemic uncertainty. Uncertainty attributable to incomplete knowledge about a phenomenon, which affects the ability to model it.

Definition

1. Any unintended event, including operating errors, equipment failures and other mishaps, the consequences or potential consequences of which are not negligible from the point of view of protection and safety.

Scope notes

• Caution: In the 2008 INES Manual (INTERNATIONAL ATOMIC ENERGY AGENCY, INES: The International Nuclear and Radiological Event Scale User’s Manual, 2008 Edition, IAEA, Vienna (2013)), there was a fundamental mismatch between the terminology used in safety standards and the designations used in INES. In short, events that would be considered accidents according to the safety standards definition may be accidents or incidents (i.e. not accidents) in INES terminology. This was not a serious day to day problem because the two areas are quite separate and have quite different purposes. However, it was a potential cause of confusion in communication with the news media and the public.

Definition

A facility (including associated buildings and equipment) in which nuclear material is produced, processed, used, handled, stored or disposed of.

Scope notes

• Also called a nuclear facility.

Definition

Provision of alternative (identical or diverse) structures, systems and components, so that any single structure, system or component can perform the required function regardless of the state of operation or failure of any other.

Definition

1. The process of determining whether a product or service is adequate to perform its intended function satisfactorily.

Scope notes

• Validation (typically of a system) concerns checking against the specification of requirements, whereas verification (typically of a design specification, a test specification or a test report) relates to the outcome of a process.
• Validation may involve a greater element of judgement than verification.

Definition

A structure that displays earthquake activity or that manifests historical surface rupture or the effects of palaeoseismicity, and is likely to generate macro-earthquakes within a time period of concern.

Definition

1. Anything that may cause radiation exposure — such as by emitting ionizing radiation or by releasing radioactive substances or radioactive material — and can be treated as a single entity for purposes of protection and safety.

Scope notes

• b. A complex or multiple installation situated at one location or site may, as appropriate, be considered a single source for the purposes of application of safety standards.
• a. For example, materials emitting radon are sources in the environment; a sterilization gamma irradiation unit is a source for the practice of irradiation preservation of food and sterilization of other products; an X ray unit may be a source for the practice of radiodiagnosis; a nuclear power plant is part of the practice of generating electricity by nuclear fission, and may be regarded as a source (e.g. with respect to discharges to the environment) or as a collection of sources (e.g. for purposes of occupational radiation protection purposes).

Definition

Detrimental health effects of exposure to radiation (including the likelihood of such effects occurring), and any other safety related risks (including those to the environment) that might arise as a direct consequence of:

• - (a) Exposure to radiation;
• - (b) The presence of radioactive material (including radioactive waste) or its release to the environment;
• - (c) A loss of control over a nuclear reactor core, nuclear chain reaction, radioactive source or any other source of radiation. (From [EUROPEAN ATOMIC ENERGY COMMUNITY, INTERNATIONAL ATOMIC ENERGY AGENCY, FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, INTERNATIONAL LABOUR ORGANIZATION, INTERNATIONAL MARITIME ORGANIZATION, OECD NUCLEAR ENERGY AGENCY, PAN AMERICAN HEALTH ORGANIZATION, UNITED NATIONS ENVIRONMENT PROGRAMME, WORLD HEALTH ORGANIZATION, Fundamental Safety Principles, IAEA Safety Standards Series No. SF-1, IAEA, Vienna (2006).].)

Scope notes

• For the purposes of the IAEA safety standards, it is assumed that there is no threshold level of radiation dose below which there are no associated radiation risks.
• Safety Requirements and Safety Guides specify the radiation exposures and other radiation risks to which they refer.

Definition

1. Administrative and technical actions taken to allow the removal of some or all of the regulatory controls from a facility.

Scope notes

• Note: The terms siting, design, construction, commissioning, operation and decommissioning are normally used to delineate the six major stages of the lifetime of an authorized facility and of the associated licensing process. In the special case of disposal facilities for radioactive waste, decommissioning is replaced in this sequence by closure.
• a. Caution: This does not apply for that part of a disposal facility in which radioactive waste is emplaced, or for certain facilities used for the disposal of naturally occurring radioactive material (NORM) or of residues from the mining and processing of radioactive ores. For all of these the term closure is used instead of decommissioning.
• b. Caution: Decommissioning typically includes dismantling of the facility (or part thereof) to reduce the associated radiation risks, but in the IAEA’s usage this need not be the case. A facility could, for example, be decommissioned without dismantling and the existing structures subsequently put to another use (after decontamination).
• c. The use of the term decommissioning implies that no further use of the facility (or part thereof) for its existing purpose is foreseen.
• d. Actions for decommissioning are taken at the end of the operating lifetime of a facility to retire it from service with due regard for the health and safety of workers and members of the public and protection of the environment.
• e. Subject to national legal and regulatory requirements, a facility (or its remaining parts) may also be considered decommissioned if it is incorporated into a new or existing facility, even if the site on which it is located is still under regulatory control or institutional control.
• f. The actions will need to be such as to ensure the long term protection of the public and protection of the environment, and typically include reducing the levels of residual radionuclides in the materials and on the site of the facility so that the materials can be safely recycled, reused or disposed of as exempt waste or as radioactive waste and the site can be released for unrestricted use or otherwise reused.
• g. Decommissioning can entail activities that are similar to remediation (also an authorized process), such as removal of contaminated soil from an area within the authorized boundary of a facility, but in this case, such removals are normally referred to as cleanup activities and are typically performed under the authorization for decommissioning.

Definition

1. The period during which an authorized facility is used for its intended purpose, until decommissioning or closure.

Scope notes

• The synonyms operating period and operational period are also used.

Definition

1. A legal document issued by the regulatory body granting authorization to perform specified activities relating to a facility or activity.

Scope notes

• b. Authorization may take other forms, such as registration or certification.
• a. 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.

Definition

The precautionary action zone and the urgent protective action planning zone.

Definition

The capability to take actions that will effectively mitigate the consequences of an emergency for human life, health, property and the environment.

Definition

The amount and isotopic composition of radioactive material released (or postulated to be released) from a facility.

Scope notes

• Used in modelling releases of radionuclides to the environment, in particular in the context of accidents at nuclear installations or releases from radioactive waste in repositories.

<h2>Definition</h2><p>In the context of the reporting and <i>analysis</i> of <i>events</i>, an <i>event</i> is any occurrence unintended by the <i>operator</i>, including operating error, equipment <i>failure</i> or other mishap, and deliberate action on the part of others, the consequences or potential consequences of which are not negligible from the point of view of <i>protection and safety</i>.</p><h2>Scope notes</h2><ul><li>c. This difference derives from the fact that <i>event</i> reporting and <i>analysis</i> is concerned directly with the question of whether an <i>event</i> that could develop into an <i>accident</i> with significant consequences actually does so; terms such as <i>accident</i> are used only to describe the end result and therefore other terms are needed to describe the earlier stages. See also <i>initiating event</i> and <i>initiating event</i>: <i>postulated initiating event</i>.</li><li>a. <b>Caution: </b>As with <i>INES</i>, the terminology related to the reporting and <i>analysis</i> of <i>events</i> is not consistent with the terminology used in <i>safety standards</i>, and great care should be taken to avoid confusion.</li><li>b. <b>Caution: </b>In particular, the definition of <i>event</i> given above is identical in essence to the <i>safety standards</i> definition (1) of <i>accident</i>.</li><li>d. <i>Event</i> is also used in the phrase ‘features, <i>events</i> and processes’ associated with the site and the <i>facility</i> in the context of <i>site characterization</i> for a <i>disposal facility</i> for <i>radioactive waste</i>.</li><li>e. Relevant features, <i>events</i> and processes relating to the site are those that might influence the long term performance of the <i>disposal facility</i> and thus could affect <i>safety</i>. These are addressed in a <i>safety case</i> and in a supporting <i>safety assessment</i>. <p>Types of events and circumstances </p> <img src="https://nucleus.iaea.org/sites/nss-oui/Figures/i_8c833feb-4169-44c2-969e-a4337573ef03.JPG " style="width: 480px;"></li></ul>