Arrangements and devices for reducing and/or preventing wear of a thermal sleeve in a nuclear reactor are disclosed. Arrangements include a first structure provided on or in one the thermal sleeve and a second structure provided on or in the head penetration adapter. At least a portion of the first structure and at least another portion of the second structure interact to resist, reduce, and/or prevent rotation of the thermal sleeve about its central axis relative to the head penetration adapter. Devices include a base for coupling to a guide tube of the reactor and a plurality of protruding members extending upward from the base. Each member having a portion for engaging a corresponding portion of a guide funnel of the thermal sleeve.

Arrangements and devices for reducing and/or preventing wear of a thermal sleeve in a nuclear reactor are disclosed. Arrangements include a first structure provided on or in one the thermal sleeve and a second structure provided on or in the head penetration adapter. At least a portion of the first structure and at least another portion of the second structure interact to resist, reduce, and/or prevent rotation of the thermal sleeve about its central axis relative to the head penetration adapter. Devices include a base for coupling to a guide tube of the reactor and a plurality of protruding members extending upward from the base. Each member having a portion for engaging a corresponding portion of a guide funnel of the thermal sleeve.

A nuclear reactor vessel includes a shell (5) having a wall (9) traversed by at least one passage (11) having a central axis (C) and a valve (21) mounted in the passage (11), the valve (21) having a determined outer cross-section. The passage (11) has an inner end segment (23) that opens into the inner volume (7) and an outer end segment (25) that opens into an outer piping (13), the valve (21) being housed in the inner end segment (23). The valve (21) is capable of being extracted from the passage (11) through the inside of the vessel (1). The outer end segment (25) has at least one portion having an inner cross-section, perpendicular to the central axis (C), that is smaller than the outer cross-section of the valve (21), such that the valve (21) cannot be ejected out of the vessel (1).

A nuclear reactor vessel includes a shell (5) having a wall (9) traversed by at least one passage (11) having a central axis (C) and a valve (21) mounted in the passage (11), the valve (21) having a determined outer cross-section. The passage (11) has an inner end segment (23) that opens into the inner volume (7) and an outer end segment (25) that opens into an outer piping (13), the valve (21) being housed in the inner end segment (23). The valve (21) is capable of being extracted from the passage (11) through the inside of the vessel (1). The outer end segment (25) has at least one portion having an inner cross-section, perpendicular to the central axis (C), that is smaller than the outer cross-section of the valve (21), such that the valve (21) cannot be ejected out of the vessel (1).

A method of replacing a damaged thermal sleeve in a reactor vessel head adapter that connects a control rod drive mechanism to a reactor vessel head includes the steps of accessing the damaged thermal sleeve, removing the damaged thermal sleeve, and obtaining a replacement thermal sleeve having an elongated tubular body, a flanged region, and a plurality of slots defined in the elongated tubular body, each slot having a width which is sufficient to narrow a maximum outside diameter of the flanged region from a first diameter to a second diameter. The method further includes altering the maximum outside diameter of the flanged region on the replacement thermal sleeve, inserting the replacement thermal sleeve into an opening of a tubular member from an underside of the reactor vessel head, and expanding the maximum outside diameter of the flanged region into a recess of the reactor vessel head adapter.

A nuclear reactor includes guide tubes (12); and vessel head penetrations (22) each comprising a tubular adapter (24) fixed in one of the openings (2a) and defining an inner passage (34). Each vessel head penetration (22) also includes a tubular sleeve (36) engaged in the inner passage (34) and axially extending in line with one of the guide tubes (12). Each sleeve (36) is suspended by an upper axial sleeve end (38) lying on an upper range (40) on the corresponding adapter (24). A lower axial end (48) of the sleeve (36) projects axially into the vessel (1) beyond the adapter (24) and is separated from an upper axial end (54) of the corresponding guide tube (12) by an axial gap having an axial height of less than 50 millimeters.

A nuclear reactor includes guide tubes (12); and vessel head penetrations (22) each comprising a tubular adapter (24) fixed in one of the openings (2a) and defining an inner passage (34). Each vessel head penetration (22) also includes a tubular sleeve (36) engaged in the inner passage (34) and axially extending in line with one of the guide tubes (12). Each sleeve (36) is suspended by an upper axial sleeve end (38) lying on an upper range (40) on the corresponding adapter (24). A lower axial end (48) of the sleeve (36) projects axially into the vessel (1) beyond the adapter (24) and is separated from an upper axial end (54) of the corresponding guide tube (12) by an axial gap having an axial height of less than 50 millimeters.

Arrangements and devices for reducing and/or preventing wear of a thermal sleeve in a nuclear reactor are disclosed. Arrangements include a first structure provided on or in one the thermal sleeve and a second structure provided on or in the head penetration adapter. At least a portion of the first structure and at least another portion of the second structure interact to resist, reduce, and/or prevent rotation of the thermal sleeve about its central axis relative to the head penetration adapter. Devices include a base for coupling to a guide tube of the reactor and a plurality of protruding members extending upward from the base. Each member having a portion for engaging a corresponding portion of a guide funnel of the thermal sleeve.

A replacement thermal sleeve with a flange for a reactor vessel closure head penetration adapter housing. By altering a diameter of the flange, a replacement thermal sleeve can be installed through the narrow diameter of the penetration adapter housing opening from under the reactor vessel head. The flange can be compressible or expandable or the tubular wall of the thermal sleeve can be inserted in longitudinal sections, one at a time, into an opening in the underside of the penetration head adapter and reformed within the opening when fully inserted.

A replacement thermal sleeve with a flange for a reactor vessel closure head penetration adapter housing. By altering a diameter of the flange, a replacement thermal sleeve can be installed through the narrow diameter of the penetration adapter housing opening from under the reactor vessel head. The flange can be compressible or expandable or the tubular wall of the thermal sleeve can be inserted in longitudinal sections, one at a time, into an opening in the underside of the penetration head adapter and reformed within the opening when fully inserted.