Nuclear activities are carried out with the two-fold aim of preventing accidents, but also of mitigating any consequences should they occur. To achieve this, in accordance with the principle of defence in depth, provision must be made to deal with a radiological emergency, however improbable. A "radiological emergency" is one resulting from an incident or accident likely to lead to the release of radioactive materials or to a level of radioactivity likely to harm public health, as defined in article R. 1333-76 of the Public Health Code. The term "nuclear emergency" is reserved for events which could lead to a radiological emergency in a basic nuclear installation or a transport of radioactive materials.

For activities with a high level of risk, such as BNIs, the emergency provisions, which can be considered the "ultimate" lines of defence, comprise special organisational arrangements and emergency plans, involving both the licensee and the authorities. These plans in particular specify the nature of the responses to be provided for to protect the population, given the scale of the exposure. This regularly tested and appraised emergency arrangement is regularly revised to take account of experience feedback from exercises, and the management of real situations such as those which occurred in the nuclear power plants at Civaux on 12 May 1998, le Blayais on 27 December 1999, Cruas and Tricastin on 2 and 3 December 2003 and, more recently, at Nogent-sur-Seine and le Blayais on 30 September and 28 October 2005.

Radiological accidents can also occur outside BNIs, either in an institution carrying out nuclear activities (hospital, research laboratory, etc.), or owing to the loss of a radioactive source, or by inadvertent or intentional dispersal of radioactive substances into the environment. For certain sites, this type of situation could be managed through an on-site emergency plan. It is up to the authorities to ensure protection of the population when necessary. The ASN is involved in this for questions relating to radiation protection.

Other situations can also trigger a response, for example situations arising from nuclear activities or industrial activities which handled materials containing natural radioelements (uranium or thorium) in the recent or more distant past. Although generally less important than accident situations in terms of exposure, these situations, in which exposure is liable to last for a long time if nothing is done ("long-term" exposure), do nonetheless present a human health risk in the medium to long term. They are mentioned in Chapter 15.

In the light of the experience acquired in recent years through regular emergency exercises and through application of France's international commitments, the texts concerning the organisation of the various parties involved in managing radiological emergencies were updated in 2005. The ASN was closely involved in preparing four interministerial directives adopted during the course of the last year:

– interministerial directive of 7 April 2005 concerning the action of the public authorities in response to an event leading to a radiological emergency;

– interministerial directive of 30 May 2005 concerning application of the International Convention on Early Notification of a Nuclear Accident (signed by France on 26 September 1986) and the 14 December 1987 decision by the Council of European Communities concerning community procedures for a rapid exchange of information in the event of a radiological emergency;

– interministerial directive of 29 November 2005 concerning the collection and processing of environmental radioactivity measurements in response to an event leading to a radiological emergency;

– interministerial directive of 30 November 2005 concerning application of the International Convention on Assistance in the Case of a Nuclear Accident or Radiological Emergency (signed by France on 26 September 1986).

Radiological emergencies can arise:
- during performance of a nuclear activity, whether for medical, research or industrial purposes. For example: a fire in a radioactive source storage area, an accident with an industrial irradiator, and so on;
- in the case of intentional or inadvertent dispersal of radioactive substances into the environment. For example: inadvertent incineration of a radioactive source;
- if radioactive sources are discovered in places where they are not supposed to be.

It is then necessary to respond, to put an end to any risk of human exposure to ionising radiation.

Owing to the diversity of the situations and locations in which these events can occur, it would be unfeasible to create a specific emergency plan for each one. This is why, in order to deal with these situations and in addition to the nuclear emergency management system described in point 2, the ASN together with the ministers and stakeholders concerned, drafted interministerial circular 2005/1390 of 23 December 2005. This circular defines how the State's services are organised in the case of an event leading to a radiological emergency other than those situations covered by an existing emergency plan. It also comprises a specimen local agreement for the technical support that EDF or AREVA could provide to the public authorities in the event of a radiological or nuclear (non-BNI) situation.