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

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

A control rod assembly for a nuclear reactor having a reactor core and a pressurized fluid source, including a control rod disposed within a control rod sleeve, a lead screw that is selectively secured to the control rod, a trip latch that is secured to a bottom end of the lead screw, the trip latch being selectively securable to a top end of the control rod, a control rod drive motor that is operably connected to the lead screw, and a valve that is in fluid communication with the pressurized fluid source of the nuclear reactor and is movable between a first position and a second position, wherein in the second position of the gas valve the trip latch is in an open position.

A control rod assembly for a nuclear reactor having a reactor core and a pressurized fluid source, including a control rod disposed within a control rod sleeve, a lead screw that is selectively secured to the control rod, a trip latch that is secured to a bottom end of the lead screw, the trip latch being selectively securable to a top end of the control rod, a control rod drive motor that is operably connected to the lead screw, and a valve that is in fluid communication with the pressurized fluid source of the nuclear reactor and is movable between a first position and a second position, wherein in the second position of the gas valve the trip latch is in an open position.

A standoff supporting a control rod drive mechanism (CRDM) in a nuclear reactor is connected to a distribution plate which provides electrical power and hydraulics. The standoff has connectors that require no action to effectuate the electrical connection to the distribution plate other than placement of the standoff onto the distribution plate. This facilitates replacement of the CRDM. In addition to the connectors, the standoff has alignment features to ensure the CRDM is connected in the correct orientation. After placement, the standoff may be secured to the distribution plate by bolts or other fasteners. The distribution plate may be a single plate that contains the electrical and hydraulic lines and also is strong enough to provide support to the CRDMs or may comprise a stack of two or more plates.

A standoff supporting a control rod drive mechanism (CRDM) in a nuclear reactor is connected to a distribution plate which provides electrical power and hydraulics. The standoff has connectors that require no action to effectuate the electrical connection to the distribution plate other than placement of the standoff onto the distribution plate. This facilitates replacement of the CRDM. In addition to the connectors, the standoff has alignment features to ensure the CRDM is connected in the correct orientation. After placement, the standoff may be secured to the distribution plate by bolts or other fasteners. The distribution plate may be a single plate that contains the electrical and hydraulic lines and also is strong enough to provide support to the CRDMs or may comprise a stack of two or more plates.

A standoff supporting a control rod drive mechanism (CRDM) in a nuclear reactor is connected to a distribution plate which provides electrical power and hydraulics. The standoff has connectors that require no action to effectuate the electrical connection to the distribution plate other than placement of the standoff onto the distribution plate. This facilitates replacement of the CRDM. In addition to the connectors, the standoff has alignment features to ensure the CRDM is connected in the correct orientation. After placement, the standoff may be secured to the distribution plate by bolts or other fasteners. The distribution plate may be a single plate that contains the electrical and hydraulic lines and also is strong enough to provide support to the CRDMs or may comprise a stack of two or more plates.

A standoff supporting a control rod drive mechanism (CRDM) in a nuclear reactor is connected to a distribution plate which provides electrical power and hydraulics. The standoff has connectors that require no action to effectuate the electrical connection to the distribution plate other than placement of the standoff onto the distribution plate. This facilitates replacement of the CRDM. In addition to the connectors, the standoff has alignment features to ensure the CRDM is connected in the correct orientation. After placement, the standoff may be secured to the distribution plate by bolts or other fasteners. The distribution plate may be a single plate that contains the electrical and hydraulic lines and also is strong enough to provide support to the CRDMs or may comprise a stack of two or more plates.

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.