This section describes the types of advanced reactor passive safety systems for removing the decay heat from the core after a reactor scram. The types of passive safety systems considered for this function are:

• Pre-pressurized core flooding tanks (accumulators)

• Elevated tank natural circulation loops (core make-up tanks)

• Gravity drain tanks

• Passively cooled steam generator natural circulation

• Passive residual heat removal heat exchangers

• Passively cooled core isolation condensers

• Sump natural circulation

A brief description of each is provided in the following sections. Combinations of these systems are incorporated into the designs described in Annexes I to XX.