Alongside the primary and secondary planning zones, the Crisis Cell can also designate an emergency action and intervention sphere.
This is the area covering the territories in which emergency preventive or protective measures are put in place immediately following a nuclear accident.
Its boundaries are not necessarily those of the primary planning zone, and can therefore exceed its limits.
Such a sphere is defined on the basis of the reference levels measured, taking into account the principles of proportionality and effectiveness.
Each sphere can include one or several entire communes and/or one or several areas of one or several communes.