Liquid metal cooled nuclear reactor

Under this invention, in a nuclear reactor cooled by a liquid metal comprising a primary vessel suspended to the roof of a concrete containment pit, said reactor vessel containing the coolant mass includes an upper open end and is suspended from the roof by ties, this reactor vessel and ties being enveloped in a leak proof jacket sealed to the roof of the pit along its edge and in which there is an inert gas to cover the coolant mass. In the construction under the invention, no circumferential retainment is prescribed on the fixing of the primary vessel to the roof structure, so that the tangential stresses are suppressed on the edge. The leak tight jacket is not in contact with the coolant and, as it is cooled by a blanket gas virtually in contact with all its internal area, it is not subjected to the high temperature difference between the surface of the mass and the pit roof. Should the need be felt, an upper circumferential area of the leak tight jacket could be internally lined with a lagging to reduce the heat transmission by radiation from the coolant mass and could be cooled from the outside. In a preferred construction, the ties include rods or straps articulated or welded to an upturned skirt secured inside the primary vessel at a height situated under the level of coolant mass surface