natural background:
See background.

naturally occurring radioactive material (NORM):
Material containing no significant amounts of radionuclides other than naturally occurring radionuclides.
The exact definition of ‘significant amounts’ would be a regulatory decision.
This includes materials in which the activity concentrations of the naturally occurring radionuclides have been changed by man-made processes.  These are sometimes referred to as technically enhanced NORM or TENORM and, as a result, the term NORM is sometimes used in contrast with TENORM, i.e. to refer only to materials in which the activity concentrations have not been technologically enhanced.

near field:
The excavated area of a repository near or in contact with the waste packages, including filling or sealing materials, and those parts of the host medium whose characteristics have been or could be altered by the repository or its contents.

near miss:
A potentially significant event that could have occurred as the consequence of a sequence of actual occurrences but did not occur owing to the plant conditions prevailing at the time.

near surface repository:
See repository.

See naturally occurring radioactive material.

normal exposure:
See exposure situations.

1.   A document submitted to the regulatory body by a legal person to notify an intention to carry out a practice or other use of a source.
This includes the notification of appropriate competent authorities by a consignor that a shipment will pass through or into their countries, as required under paras 557-560 of the 1996 Edition of the IAEA Transport Regulations [41].
2.   A report submitted to a national or international authority providing details of an event, particularly an accident, e.g. as required by the Convention on Early Notification of a Nuclear Accident [12].

nuclear damage:

  • Loss of life or personal injury;
  • loss of or damage to property;
    and each of the following to the extent determined by the law of the competent court:
  • economic loss arising from loss or damage referred to in sub-paragraph (i) or (ii), insofar as not included in those sub-paragraphs, if incurred by a person entitled to claim in respect of such loss or damage;
  • the costs of measures of reinstatement of impaired environment, unless such impairment is insignificant, if such measures are actually taken or to be taken, and insofar as not included in sub-paragraph (ii);
  • loss of income deriving from an economic interest in any use or enjoyment of the environment, incurred as a result of a significant impairment of that environment, and insofar as not included in sub-paragraph (ii);
  • the costs of preventive measures, and further loss or damage caused by such measures;
  • any other economic loss, other than any caused by the impairment of the environment, if permitted by the general law on civil liability of the competent court,

in the case of sub-paragraphs (i) to (v) and (vii) above, to the extent that the loss or damage arises out of or results from ionizing radiation emitted by any source of radiation inside a nuclear installation, or emitted from nuclear fuel or radioactive products or waste in, or of nuclear material coming from, originating in, or sent to, a nuclear installation, whether so arising from the radioactive properties of such matter, or from a combination of radioactive properties with toxic, explosive or other hazardous properties of such matter. [53]
In this context, preventive measures are defined as any reasonable measures taken by any person after a nuclear incident has occurred to prevent or minimize damage referred to in sub-paragraphs (i) to (v) or (vii), subject to any approval of the competent authorities required by the law of the State where the measures were taken.

nuclear facility:
A facility and its associated land, buildings and equipment in which radioactive materials are produced, processed, used, handled, stored or disposed of on such a scale that consideration of safety is required.
The Joint Convention definition is identical, except that it begins: "A civilian facility…".
Essentially synonymous with authorized facility, and hence more general than nuclear installation.

nuclear fuel cycle:
All operations associated with the production of nuclear energy, including:

nuclear installation:
1.   A nuclear fuel fabrication plant, nuclear reactor (including subcritical and critical assemblies), research reactor, nuclear power plant, spent fuel storage facility, enrichment plant or reprocessing facility. [40]<
This is essentially any authorized facility that is part of the nuclear fuel cycle except radioactive waste management facilities.
2.   For each Contracting Party, any land-based civil nuclear power plant under its jurisdiction including such storage, handling and treatment facilities for radioactive materials as are on the same site and are directly related to the operation of the nuclear power plant.  Such a plant ceases to be a nuclear installation when all nuclear fuel elements have been removed permanently from the reactor core and have been stored safely in accordance with approved procedures, and a decommissioning programme has been agreed to by the regulatory body. [11]

nuclear material:
Plutonium except that with isotopic concentration exceeding 80% in plutonium-238; uranium-233; uranium enriched in the isotope 235 or 233; uranium containing the mixture of isotopes as occurring in nature other than in the form of ore or ore-residue; any material containing one or more of the foregoing. [56]
The Statute of the IAEA [57] uses the term special fissionable material, with essentially the same meaning, but explicitly excluding source material.

nuclear safety:

The achievement of proper operating conditions, prevention of accidents or mitigation of accident consequences, resulting in protection of workers, the public and the environment from undue radiation hazards.
Often abbreviated to safety in Agency publications on nuclear safety, particularly when other types of safety (e.g. fire safety, conventional industrial safety) are being discussed.
See protection and safety for a discussion of the relationship between nuclear safety and radiation protection.