Liquid metal or molten salt(s) reactor incorporating a decay heat removal (dhr) system that removes heat through the primary reactor vessel, comprising a module of passively or actively triggered pivoting fins located in the guard gap

A nuclear reactor of the liquid metal or molten salt fast neutron reactor type, comprising:

• a vessel referred to as primary, vessel, filled with a liquid metal or with a molten salt by way of primary coolant for the reactor primary coolant circuit;
• a vessel referred to as secondary vessel, arranged around the primary vessel defining a guard vessel gap (E) between the primary vessel and the secondary vessel;
• a reactor pit, arranged around the secondary vessel;
• a reactor closure to enclose the coolant inside the primary vessel;
• a heat removal system for removing at least some of both the nominal heat and the decay heat of the reactor, the system comprising:
• a closed circuit filled with a coolant and configured so that the coolant circulates therein by natural or forced convection and remains in the liquid state both in nominal operation of the nuclear reactor and in reactor shutdown situations, the closed circuit comprising a serpentine coil arranged between the reactor pit and the secondary vessel, and wound in a helix around the latter;
• a module fixed to the reactor closure and comprising:
• at least a shell arranged inside the guard gap (E) and in contact with the secondary vessel,
• a plurality of heat-conducting fins arranged inside the guard gap (E) and angularly distributed around the primary vessel in columns, each column comprising several fins spaced away from one another over at least part of the height of the secondary vessel and mounted with the ability to pivot along the secondary vessel between a retracted position in which they are distant from the primary vessel and a deployed position in which they are in contact with the primary vessel,
• one or more Seebeck-effect thermoelectric element(s) arranged inside the shell and extending along the secondary vessel with their hot side in the lower part of the shell and their cold side in the upper part of the shell, the Seebeck-effect thermoelectric element(s) being designed so that during nominal operation of the nuclear reactor, the current that they generate leaves the fins in their retracted position, whereas in an accident situation in which decay heat needs to be removed, the current that they generate causes the fins to pivot into their deployed position.