Abstract: A control rod for a pressurized-water nuclear reactor contains an absorber rod which is arranged in a casing tube. At least in a lower section, the absorber rod is provided with at least one recess which takes up at most a portion of the circumferential surface of this section. This reduces problems associated with an expansion in the volume of the absorber rod.

Abstract: A method of and a system for evaluating constraint functions for improving nuclear reactor performance involve generating an operational solution for a nuclear reactor using a constraint to account for a problem with the operation of the nuclear reactor. The problem is based at least in part on channel deformation criteria.

Abstract: A fast reactor including a reactivity control assembly including a reactor shutdown rod and neutron absorbers, a reactor shutdown rod drive mechanism, and units of neutron absorber drive mechanism. The reactor shutdown rod drive mechanism causes an inner extension tube to fall and release the reactor shutdown rod by a gripper section by turning off the power supply to a holding magnet at the time of scram. When grasping the neutron absorbers, an outer extension shaft is pulled up to allow both of the extension shafts to be inserted. After the outer extension tube gets to a handling head section of the neutron absorber, the outer extension shaft is pushed down to grasp the neutron absorber externally by latch fingers of the gripper section so that the neutron absorber can be moved up and down.

Abstract: A neutron flux control component for a nuclear reactor. Thin, overlapping segments of highly neutron absorbing material are positioned in the core of a reactor. The self-shielding overlapping segments are moved relative to each other to vary the amount of exposed surface area of poison to control core reactivity and to provide power shaping within the reactor core. The poison segments are mounted to carriers in the form of close-fitting concentric cylinders or rods of V-shaped cross section.

Abstract: A control rod for use in a nuclear reactor core to provide xenon compensation includes an elongated inner cylindrical member and an elongated outer cylindrical member surrounding the inner member. Each of the members is composed of axially-extending, alternating black poison and nonpoison regions. Also, the inner member is axially movable relative to the outer member to adjust the degree to which the poison regions of the members overlap with the nonpoison regions thereof and thereby change the overall worth of the rod in an axially uniform manner. The inner cylindrical member has a solid cross-sectional configuration, whereas the outer cylindrical member has an annular cross-sectional configuration and concentrically surrounds the inner member. Each of the poison regions in the members is about the same axial height, while each of the nonpoison regions is about the same axial height.

Abstract: Improvements in high temperature gas cooled nuclear reactors is effected by an arrangement of paired absorber elements, each pair comprising a rod shaped absorber element and a tubular absorber element generally surrounding the rod shaped element. With this paired combination in a reactor employing spherical fuel elements, the effective life of the absorber rods is significantly extended by protection of the rod shaped absorber element from excessive amounts of irradiation from thermal neutrons.