1Throughout this publication, the term ‘regulatory body’ is used to mean 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 nuclear, radiation, radioactive waste and transport safety. Earlier safety standards used the term ‘Regulatory Authority’

2This Safety Guide does not address the design measures that are necessary to reduce the probability of the occurrence and to prevent the development of accidents. These aspects are considered in the Safety Requirements for Design [1] and in other Safety Guides.

3For internal exposures, such as those that result from the inhalation and ingestion of radioactive substances, the dose limits apply to the committed dose.

4An authorized dose limit or dose constraint is one that has been established or formally accepted by a regulatory body.

5It should be recognized that design targets are not limits. They are useful design tools in the optimization process. However, provided that any excess can be justified, they may be exceeded. Also, achieving a design target does not, in it self, demonstrate that a design satisfies the optimization principle. A dose should be reduced below a target if this can be done at a cost that is justifiable.

6There are various ways of ensuring that the design team is fully aware of the radiological protection measures that should be incorporated into the design, such as by having experts in radiological protection document the requirements and provide training. It may be appropriate to include an experienced operator in the design team.

7An optimization culture may be explained as a system of shared knowledge, common objectives and attitudes that ensures that the management of occupational exposure and the exposure of members of the public benefit from the cooperation of all personnel involved in a project.

8The IAEA is revising the requirements and guidance in the area of quality assurance as established in Safety Series No. 50-C/SG-Q (1996) in new safety standards on management systems for the safety of nuclear facilities and activities involving the use of ionizing radiation. The term ‘management system’ has been adopted in the revised standards instead of the terms ‘quality assurance’ and ‘quality assurance programme’. The new standards will integrate all aspects of managing a nuclear facility, including the safety, health, environmental and quality requirements, into one coherent system.

9The term ‘safety train’ refers to a set of plant components that perform a safety function, such as an emergency core cooling pump and its associated equipment and source of water.

10Requirements and recommendations on the management of radioactive waste before it is sent to a repository are established in IAEA Safety Requirements and Safety Guides [4–6].

11This Safety Guide does not give guidance on the calculational methods or the values of the parameters to be used to evaluate the radiation dose rates that are expected to occur during operation and decommissioning.

12This applies for reactors for which a nickel based alloy is used for steam generator tubing.

13In PWRs that have been subject to the ‘baffle jetting’ phenomenon, the amount of irradiated fuel may reach a few hundred grams.

14Essential equipment here means equipment that must continue to be operable to prevent the escalation of an accident or further radioactive releases (e.g. pumps in water cooled reactors or gas circulators in GCRs, which are required to maintain core cooling), and equipment that is required for monitoring the state of the plant after an accident.

15In the event of an emergency, radiation dose limits for normal operation may be exceeded. Use should then be made of dose levels given in para. 6.13 of Ref. [7] and other conditions as established in Section 6 of Ref. [7] for interventions in emergencies.

16In the case of spray systems, care should be taken with regard to the control of tritium in the containment.

1In reactors with on-load refuelling and a detection capability for failed fuel, the release of fission products to the coolant can be kept low.

1In such plants, gases are usually removed by the purification system.

1The term ‘fresh fuel’ means new or unirradiated fuel, even though the fuel may have been fabricated from fissionable materials recovered by reprocessing previously irradiated fuel.

1This fraction is the inverse of the ‘decontamination factor’ which is also sometimes used.

1This section deals with the design philosophy in the United Kingdom, where such reactors are in operation.

1‘Free’ here means released from the fuel (UO₂) matrix.

1This applies for reactors in which a nickel based alloy is used for steam generator tubing.

1Examples are the ORIGEN, FISPIN and APOLLO codes in the USA, in the United Kingdom and in France, respectively.