Screwed safety assembly

Claim 1

A screwed safety assembly for an easily dismountable assembly of a nuclear reactor, comprising a screw (12) the head (13) of which engages in a smooth seating (4) in a first part to be assembled (1), and the threaded shank of which engages a mating threaded portion of a second part to be assembled (2), said head of said screw comprising a deformable portion consisting of a thin external cylindrical ferrule (15), and said seating (4) of said screw head comprising, over a portion only of its periphery, at least one widened portion (6) of larger diameter into which a corresponding portion of said deformable ferrule (15) penetrates upon being deformed by expansion, said seating (4) of said screw head also comprising a circular groove (10) formed at the level of the upper edge of said deformable ferrule (15) between said at least one widened portion (6) and leading thereinto, in such manner that, when said ferrule is deformed by expansion, at least a portion of said upper edge penetrates into said groove (10) between said at least one widened portion (6), whereby said head (13) of said screw (12) is retained in said seating (4) in the event of fracture of said screw (12), the deformability of said ferrule (15) being sufficient to permit disengagement of said assembly merely by unscrewing, the portions of said ferrule (15) which were expanded then being deformed in the opposite direction.