Device for demountable fastening of a guide tube into an end fitting of a fuel assembly of a nuclear reactor

Claim 1

Device for demountable fastening of a guide tube into an end fitting of a fuel assembly of a nuclear reactor cooled by light water comprising a bundle of parallel fuel rods held in a framework (9) consisting of guide tubes (4), spacers (3) and end fittings (5, 6) fastened to ends of said guide tubes (4), at least one of said end fittings (5, 10) being fastened demountably to one of said ends of each of said guide tubes (4) by means of a radially distortable end part (4a) of said guide tube (4), said end part having a radially outwardly projecting interlocking part (17) engaged inside and over a part of the length of an opening (11) passing through a said end fitting (5, 10), said opening (11) comprising, in said part receiving a said guide tube (4), an annular bulge (16) intended to receive said interlocking part (17) of said guide tube, radial expansion of said end of said guide tube and retention of said interlocking part (17) in said annular bulge (16) of said opening (11) of said end fitting (5, 10) being provided by a locking sleeve (20) comprising a ring (24) for expanding said guide tube (4) and a shell (25) for fastening in said end fitting, projecting at said end of said guide tube in the locking position of said sleeve (20), inside a part of said opening (11) of said end fitting (5, 10) which does not receive said guide tubes (4), said part of said opening (11) of said end fitting (10) comprising at least one radial cavity (22) inside which a part (32) of the fastening shell (25) is distorted radially to ensure fastening of said locking sleeve (20), wherein: (a) the outer surface of said locking sleeve (20) has, successively in an axial direction of said sleeve, a cylindrical upper part and a frusto-conical lower part, said sleeve being free of any radially outwardly protruding part; (b) said fastening shell (25) constituting said cylindrical upper part of said sleeve is integral with said frusto-conical lower part constituting said ring (24) for expanding said tube and said fastening shell has a thickness substantially smaller than the thickness of the upper part of the frusto-conical ring for expanding said tube; and (c) an interlocking annular groove (29) is machined in the upper part of an internal surface of said ring (24) for expanding said tube.