Heat-generating nuclear reactor with liquid metal coolant and core comprising coolant-sealed tubes each housing "triso" nuclear fuel particles

A nuclear reactor cooled by liquid metal including a vessel, called the primary vessel, that is axisymmetrical about a central axis (X), filled with a heat transfer fluid containing at least one liquid metal as the heat transfer fluid of the primary circuit of the reactor, the vessel including a core including a plurality of hollow, sealed and fixed tubes arranged parallel to the axis X so that when the reactor is operating the liquid metal circulates in contact with the exterior periphery thereof, each hollow tube housing a stack of fuel assemblies housing so-called TRISO nuclear fuel particles mixed with a matrix, wherein each seated and fixed tube includes a blind tubular part forming an immersion sleeve in which the fuel assemblies are stacked before the reactor begins to operate.