Liquid metal cooled nuclear reactor

Claim 1

A liquid metal cooled reactor comprising a cylindrical primary vessel, a reactor core within said primary vessel, fuel assemblies in said core, a concrete slab roof closing said cylindrical primary vessel, a horizontal inner wall for said roof, a liquid metal coolant in said primary vessel, a hot gaseous medium above said liquid metal coolant, pumps and heat exchangers, a system of rotating shield plugs in said slab roof, a central opening in said roof for said system of rotating shield plugs, a first vertical wall for said roof delimitating said central opening, a plurality of passages in said roof for said heat exchangers and pumps, second vertical walls for said roof delimitating said passages, a third vertical wall for said roof located opposite to said primary vessel, a sheet metal plate covering said horizontal inner wall and said first, second and third vertical walls of said roof, a thermal protection device for said slab roof comprising an annular metallic planar plate of thickness smaller than and also equal to 25 mm extending beneath said slab roof parallel to said horizontal inner wall of said roof, an internal edge for said annular plate defined by said central opening, an external edge for said annular plate defined by said third vertical wall, openings in said annular plate located opposite to said passages for said heat exchangers and pumps, edges for said openings in said annular plate, a first vertical sealing shell surrounded by said first vertical wall of said roof, said first vertical sealing shell being fixely connected at one end to the inner edge of said metallic annular plate and at the other end to the sheet metal plate covering said first vertical wall of said roof at the upper part of said first vertical wall, second vertical sealing shells surrounded by said second vertical walls of said roof, each of said second vertical shells being fixely connected at one end to the edge of one of said openings in said metallic annular plate and at the other end to the sheet metal plate covering one of said second vertical walls of said roof at the upper part of said second vertical walls, said external edge of said annular metallic plate being connected to the sheet metal plate covering said third vertical wall of said roof by a connecting member, the radius of curvature of said connecting members being at least equal to 0.60 m, an inert gas trapped in closed spaces delimitated between said annular plate and said horizontal wall of said roof and between said first and second vertical walls of said roof and said first and second shells and means disposed in said roof along its horizontal inner wall and its vertical walls for evacuation of calories accumulated by said inert gas trapped in said closed spaces in contact with said annular plate.