7. In-service testing and monitoring of the enclosure

7.1 Mechanical strength test

Before the unit is commissioned, the PWR 900 enclosure and the inner wall of the PWR 1,450 enclosure are subjected to a test by pressurizing the interior atmosphere with dry air at ambient temperature. The effective pressure is equal to the design pressure p for PWR 1,300-1,450, and 1.15 p for PWR 900, to account for the action of the metal skin in the event of a LOCA, as its expansion is counteracted by the concrete, which remains cold.

In operation, no resistance tests are planned. However, a complete survey of the monitoring devices is carried out during the periodic overall watertightness tests.

In addition, measurements are taken at intervals of around 3 months to monitor the evolution of the structure...