A.6. Leakage of fluids such as compressed air, nitrogen or water may be the cause of pressure increases. To detect leaks, measurements of the ambient pressure in the appropriate compartments in the containment building should be obtained. These measurements should account for variations in other parameters such as temperature, humidity, or levels of ionizing or electromag­netic radiation. The pressure measurements should be recorded to show trends.

Humidity in the containment building

A.7. Humidity is a highly significant factor for the detection of leaks from the primary circuit. Parameters that indicate changes in humidity include:

— The dew point temperature of the containment atmosphere,

— Electrical parameters (such as impedance or resistance) of sensors,

— The amount of condensate in the air coolers of the containment building.

A.8. Humidity levels should be monitored in appropriate compartments in the containment buildings (in the primary containment, and in the secondary

containment if applicable), and the measured values should be recorded to show trends.