CATHARE2 transient calculations have been performed for ASTRID with a gas PCS.

The behavior of the reactor is close for gas and for water PCS in case of LOOP.

The gas PCS enables to cool the core for at least 10 h for pressurized transients.

The depressurization of the PCS induces an over-cooling for breaches on low pressure pipes.

The spurious opening of a by-pass line of the turbomachine can be controlled without scram.