5.2.4 Requirements of containments

The containment (safety container or enclosure) in the reactor building of a nuclear power plant is the essential structural barrier involved in containing radioactive

substances safely (cf. Sections 2.5 and 4.2). The verifications required for this barrier are:

— bearing capacity

— serviceability in the sense of functional ability

— integrity (gas-tightness).

Bearing capacity and serviceability for use can be combined as a single overall concept, structural integrity. The structural integrity of a containment is tested once it has been made, while gas-tightness is tested regularly every three to five years.

The verifications must take account of the actions when operated as intended (normal and abnormal operation) and those of incidents (cf. Section 2.5). Containment design is governed in particular by the possibility of a loss of coolant accident, with its high pressure of the order of 0.5 MPa accompanied by temperatures of approx. 150 °C.