SUPPRESSION

This section describes the types of advanced reactor passive safety systems for removing the heat from the containment and reducing pressure inside containment subsequent to a loss of coolant accident. The types of passive safety systems being incorporated for this function are:

• Containment pressure suppression pools

• Containment passive heat removal/pressure suppression systems

• Passive containment spray

A brief description of each passive safety system for pressure suppression and containment cooling is provided in the following sections. Combinations of these systems are incorporated into the designs described in the Annexes I to XX.

3.1. Containment pressure suppression pools

Containment pressure suppression pools have been used in BWR designs for many years. Figure 9 presents a generic concept of a suppression pool. Following a LOCA, steam is generated into the drywell (the primary containment) following vaporization of liquid and/or steam expansion, both of these coming from the primary system typically due to a break. From drywell the steam-non condensable mixture is subsequently forced through large vent lines submerged in the water in the suppression pools. The steam condenses, thus mitigating a pressure increase in the containment. This is a Category B and C passive safety system.