A nuclear fuel assembly comprising a plurality of control rod guide assemblies. At least one of the control rod guide assemblies includes a guide tube having an axial dimension, the guide tube being supported by the plurality of grids and extending axially between the top nozzle and the bottom nozzle, the guide tube having an upper portion having a first radius and a lower portion having a second radius less than the first radius, and an external dashpot tube disposed around a portion of the lower portion in an area beginning at the bottom grid and extending toward the top nozzle.

A nuclear fuel assembly comprising a plurality of control rod guide assemblies. At least one of the control rod guide assemblies includes a guide tube having an axial dimension, the guide tube being supported by the plurality of grids and extending axially between the top nozzle and the bottom nozzle, the guide tube having an upper portion having a first radius and a lower portion having a second radius less than the first radius, and an external dashpot tube disposed around a portion of the lower portion in an area beginning at the bottom grid and extending toward the top nozzle.

A nuclear fuel assembly comprising a plurality of control rod guide assemblies. At least one of the control rod guide assemblies includes a guide tube having an axial dimension, the guide tube being supported by the plurality of grids and extending axially between the top nozzle and the bottom nozzle, the guide tube having an upper portion having a first radius and a lower portion having a second radius less than the first radius, and an external dashpot tube disposed around a portion of the lower portion in an area beginning at the bottom grid and extending toward the top nozzle.

A nuclear fuel assembly comprising a plurality of control rod guide assemblies. At least one of the control rod guide assemblies includes a guide tube having an axial dimension, the guide tube being supported by the plurality of grids and extending axially between the top nozzle and the bottom nozzle, the guide tube having an upper portion having a first radius and a lower portion having a second radius less than the first radius, and an external dashpot tube disposed around a portion of the lower portion in an area beginning at the bottom grid and extending toward the top nozzle.

A control assembly for a nuclear reactor having a pump includes a duct having an inner volume and defining a coolant flow path, a plug fixed to the duct, a rod disposed within the inner volume and having a rod end that is configured to engage a neutron modifying material, a first piston disposed within the inner volume, slidably coupled to the duct, and coupled to the rod, and a biasing member coupled to the rod and the first piston. The biasing member is positioned to apply a biasing force that repositions the first piston, the rod, and the neutron modifying material in response to a loss of pump flow without scram condition.

A reactor lateral reflection layer telescoped control rod capable of separately achieving cold shutdown includes an inner rod, an outer rod and a guide cylinder assembly which are vertically and coaxially arranged, wherein the outer rod and the guide cylinder assembly are hollow cylindrical bodies; the top end of the inner rod can move up and down inside the outer rod and the other end of the inner rod moves up and down, along with the top end, inside a control rod passage which is positioned below the guide cylinder assembly and is coaxial with the guide cylinder assembly; and the top end of the outer rod can move up and down in the guide cylinder assembly and the other end of the outer rod moves up and down, along with the top end, inside the control rod passage.

A control rod assembly including at least one movable control rod including a neutron absorbing material, a control rod drive mechanism (CRDM) for controlling movement of the at least one control rod, and a coupling operatively connecting the at least one control rod and the CRDM. The coupling includes a terminal element engaged with a connecting rod of the CRDM and the at least one moveable control rod, and a kinetic energy absorbing element supported by the terminal element for absorbing kinetic energy during a SCRAM event, the kinetic energy absorbing element configured to act between the terminal element and an upper plate of an associated fuel assembly.

A control rod assembly including at least one movable control rod including a neutron absorbing material, a control rod drive mechanism (CRDM) for controlling movement of the at least one control rod, and a coupling operatively connecting the at least one control rod and the CRDM. The coupling includes a terminal element engaged with a connecting rod of the CRDM and the at least one moveable control rod, and a kinetic energy absorbing element supported by the terminal element for absorbing kinetic energy during a SCRAM event, the kinetic energy absorbing element configured to act between the terminal element and an upper plate of an associated fuel assembly.

A nuclear fuel assembly comprising a plurality of control rod guide assemblies. At least one of the control rod guide assemblies includes a guide tube having an axial dimension, the guide tube being supported by the plurality of grids and extending axially between the top nozzle and the bottom nozzle, the guide tube having an upper portion having a first radius and a lower portion having a second radius less than the first radius, and an external dashpot tube disposed around a portion of the lower portion in an area beginning at the bottom grid and extending toward the top nozzle.

A nuclear fuel assembly comprising a plurality of control rod guide assemblies. At least one of the control rod guide assemblies includes a guide tube having an axial dimension, the guide tube being supported by the plurality of grids and extending axially between the top nozzle and the bottom nozzle, the guide tube having an upper portion having a first radius and a lower portion having a second radius less than the first radius, and an external dashpot tube disposed around a portion of the lower portion in an area beginning at the bottom grid and extending toward the top nozzle.