Classification of areas

Containment zones

The containment is a cylindrical structure made of concrete or steel. Concrete structures can have their inner surface covered by a steel lining to reduce the leakage rate. This type is called simple containment.

To enhance the safety function of the containment, a steel structure containing the reactor and all The RCS system can be installed inside an exterior concrete containment, and the gases that accumulate in the space between the two containments are filtered and released through a ventilation chimney.

The internal steel structure, which can be spherical or cylindrical, is the next called primary containment, while the external concrete structure is called secondary containment.

  • Double type of containment. Double containment with primary containment containing only part of the RCS is called partially double.


Some older types of reactors may have only the RCS installed within a structure designed to maintain coolant pressure after a loss of coolant accident, while the reactor is housed only in the structure of a conventional reactor building.


  • “Partial” containment is called confinement. For this feature, data providers must choose the appropriate option from the multiple-choice menu: single, double, partially double, confinement, N / A.
  • Containment form – the geometricshape of the hermetic internal structure containing the reactor and primary circuit. For nuclear power plants with confinement or without any type of confinement, containment spray. Other reactors can use vacuum buildings designed to suck up leaks.