For the SCOR, transients leading to an extension of design basis conditions are either eliminated by design or managed using the following passive provisions:

• H1 (total loss of the heat sink): the SCOR concept is based on several independent decay heat removal (RRP) loops ready to operate in a passive mode with a heat sink either in the pools with a limited autonomy of several hours or in an air cooling tower in which autonomy is infinite;

• H2 (total loss of feedwater supply to the steam generator): decay heat is removed by systems of the primary circuit with a redundancy of 16 x 25%. There is no need for a safety grade auxiliary feedwater system;

• H3 (total loss of all power supplies): natural convection is possible in all decay heat removal systems with integrated exchangers, from the primary circuit to the heat sink;

• H4 (loss of the containment spray or the low pressure safety injection): the SCOR has no containment spray system, because it uses a pressure suppression type containment. The low pressure safety injection plays a less significant role than in standard PWRs because of large thermal inertia of the primary circuit; large break LOCAs are eliminated by design; the decay heat removal systems are sufficiently effective and redundant;

• ATWS (anticipated transient without scram): the SCOR has two independent shutdown systems so that the overlapping transients will be treated individually as in standard PWRs. Accident management would be simplified due to the permanently negative and higher moderator temperature reactivity coefficient, as compared to standard PWRs. In the case of a LOFA, power is removed by 4 RRP and the primary temperature is stabilized at a value below the saturation temperature, corresponding to the opening of the pressure safety valve;

• Multiple rupture of steam generator tubes and loss of containment isolation: steam from the steam generator is discharged to a dedicated pool;

• Failure of HPSI: no HPSI is provided for in the SCOR.

The hypothetical case of a core meltdown is managed through the following measures:

• In-vessel retention: corium cooling can be ensured by natural convection of water in the flooded reactor cavity, because power density in the core is relatively low and the grace period before a hypothetical core meltdown is long, which altogether reduces decay heat by the time the corium enters the lower plenum;

• Hydrogen risk: the atmosphere of the reactor vessel compartment is inerted to prevent hydrogen combustion (similar to boiling water reactors).