The fight against nuclear proliferation primarily involves monitoring compliance with international treaties, namely the Non-Proliferation Treaty (NPT) and the Comprehensive nuclear Test-Ban Treaty (CTBT). The CTBT's verification system will particularly include an international monitoring network ultimately comprising 321 stations using different detection methods (see information below). The recordings from these stations will be transmitted in real time to an international center located in Vienna (Austria) for analysis. The aim of the international system is to detect, with certainty, any nuclear explosion of at least 1 kiloton (1,000 tons) TNT equivalent, regardless of geographic location (in the ground, the atmosphere or the oceans).

What is to be done to detect a nuclear test? Several methods can be used to detect a nuclear test. It all depends on the type of test: underground, open-air or underwater. Underground nuclear tests create seismic waves similar to those in an earthquake. They can therefore be detected by seismometers. Open-air nuclear tests have very little interaction with the ground, which means that seismic waves cannot be used. On the other hand, acoustic disturbances generated in the atmosphere can be measured using a microbarometer.   Radioactive materials dispersed in the atmosphere during the explosion can also be measured. Detection stations collect the particles suspended in the atmosphere and report the presence of certain radioactive elements which are characteristic of a nuclear explosion. Underwater nuclear tests generate acoustic waves which can propagate over long distances in water. To detect these tests we use hydrophones. When the waves are transmitted to land, seismic detection stations detect the acoustic waves that have been converted to seismic waves.

Environmental monitoring

The CEA's experienced teams are also responsible for detecting any seismic event, quickly locating it, calculating its magnitude and issuing an alert to the authorities. This is the role of the environmental assessment and monitoring Department (Département analyse, surveillance, environnement, DASE) of the DAM, a team of recognized operational detection experts.
Its activities are not limited to detection, but also include studies for determining seismic risk in given geographical areas.

The two types of alert given by the CEA: Notify the French civil security service within two hours for an earthquake of magnitude greater than 4 in France or border regions.   Help to alert the Council of Europe within one hour for an earthquake of magnitude greater than 5 in the Euro-Mediterranean area, as part of Euro-Mediterranean Seismological Centre activities.

The DASE's expertise in radionuclide detection is also used for environmental monitoring and protection purposes. This mainly involves:

		Studies of the impact of nuclear-related activities (liquid and gaseous effluent standards),
		Studies of ground pollution and migration of both radioactive and chemical pollutants, such as heavy metals.

Fundamental research and studies

To meet their operational duties and anticipate future requirements, the DASE teams conduct fundamental research in earth and environmental sciences and in the following related disciplines:

		Seismology (searching for forerunning events, active faults, seismic risk assessments),
		Fluid-rock interaction,
		Geology,
		Transport and migration of pollutants in the hydrogeological environment,
		Speciation of radionuclides,
		Electromagnetism,
		Signal processing (seismic, infrasound, hydroacoustic signals),
		Advanced information processing.