In an emergency situation, the ASN, with IRSN assistance and the co-operation of the Regional Directorate for Industry, Research and the Environment (DRIRE) concerned, has a four-fold function:
1) ensure that judicious provisions are made by the licensee;
2) advise the Prefect;
3) contribute to the circulation of information;
4) act as competent authority within the framework of the international conventions.

a) Supervision of licensee actions

In the same way as in normal operating conditions, licensee actions are supervised by the ASN in an emergency situation. In this particular context, the ASN must ensure that the licensee fully carries out its duty to control the accident, minimise the consequences and rapidly and regularly inform the authorities, but it will not attempt to replace the licensee in implementing the technical measures to deal with the accident. In particular, when several action strategies are available to the licensee to control the accident, some may have significant environmental consequences. It is therefore important for the ASN to monitor the conditions in which the corresponding choice is made by the licensee.

b) Advising the prefect

The decision by the Prefect concerning the population protection measures to be taken depends on the actual or possible consequences of the accident around the site and it is the ASN which advises the Prefect in this respect, on the basis of the analysis performed by the IRSN. This analysis combines diagnosis (understanding of the situation at the plant concerned) and prognosis (assessment of possible short-term developments, notably radioactive release). This advice also concerns the steps to be taken to protect the health of the public.

c) Circulation of information

The ASN is involved in information circulation in a number of ways:
- information of the media and the general public: the ASN contributes to informing both the media and the general public in different ways (press releases, website, press conference). It is important that this should be done in close collaboration with the other organisations who are themselves involved in communication (Prefect, local and national licensee, etc.);
- information of the authorities: the ASN keeps the supervisory Ministers informed, together with the SGDN (General Secretariat for National Defence), which in turn informs the President of the Republic and the Prime Minister. The ASN also ensures that the DGEMP (General Directorate for Energy and Raw Materials) at the Ministry for Industry is kept informed;
- information of foreign safety authorities: without prejudice to application of the international conventions signed by France concerning information exchanges in the event of an incident or accident liable to have radiological consequences, the ASN informs foreign safety authorities, especially those with which it has mutual safety information agreements (Belgium, Switzerland, United Kingdom, etc.).

d) Function of competent authority as defined by international conventions

Since the publication of decree 2003-865 of 8 September 2003, the ASN has been the competent authority under the terms of the above-mentioned international conventions. In this capacity, it collects and summarises the information needed for the notifications, information and requests provided for in these conventions. This information is forwarded to the international organisations (IAEA and European Union).

In 2005, France in particular took part in the international exercises organised by the European Community and the IAEA (Convex 3 and Ecurie 3). These exercises in particular test the alert, information transmission and exchange procedures between the national alert contact point (Ministry of foreign affairs), the national competent authority (ASN) and the emergency centres of the European Community and the IAEA.