A nuclear reactor head (12) comprising a vessel top head (14), a penetration (36) extending through the vessel top head (14) along a penetration axis (B) for allowing passage of a control shaft (34) of a control rod drive mechanism (32) through the vessel top head (14) and to a corresponding control guide tube (30) of the nuclear reactor (2), the penetration (36) comprising a penetration tube (38) extending through the vessel top head (14) and a thermal sleeve (40) extending inside the penetration tube (38) and coaxially with the penetration tube (38) with an axial play between the thermal sleeve (40) and the penetration tube (38), wherein the nuclear reactor head further comprises a spacer (60) attached to a lower end of the thermal sleeve (40) for maintaining minimal spacing with the upper end of the corresponding control rod guide tube (30).

A nuclear reactor head (12) comprising a vessel top head (14), a penetration (36) extending through the vessel top head (14) along a penetration axis (B) for allowing passage of a control shaft (34) of a control rod drive mechanism (32) through the vessel top head (14) and to a corresponding control guide tube (30) of the nuclear reactor (2), the penetration (36) comprising a penetration tube (38) extending through the vessel top head (14) and a thermal sleeve (40) extending inside the penetration tube (38) and coaxially with the penetration tube (38) with an axial play between the thermal sleeve (40) and the penetration tube (38), wherein the nuclear reactor head further comprises a spacer (60) attached to a lower end of the thermal sleeve (40) for maintaining minimal spacing with the upper end of the corresponding control rod guide tube (30).

A full-digital control rod position measurement device and a method thereof. The full-digital rod position measurement device transforms the core process of rod position measurement that is normally processed by an analog circuit or analog-to-digital mixed circuit into a digital processing. The full-digital rod position measurement device comprises an excitation power supply, an integrated interface board, and a universal signal processor. The universal signal processor processes output signals of detectors according to a preset numerical processing algorithm and outputs Gray code rod position signals. The full-digital rod position measurement device and method disclosed by the present disclosure may effectively reduce the complexity of the primary excitation circuit and the secondary measurement signal processing circuit of the detectors, and improve the operation reliability and measurement accuracy of the rod position processing equipment.

A full-digital control rod position measurement device and a method thereof. The full-digital rod position measurement device transforms the core process of rod position measurement that is normally processed by an analog circuit or analog-to-digital mixed circuit into a digital processing. The full-digital rod position measurement device comprises an excitation power supply, an integrated interface board, and a universal signal processor. The universal signal processor processes output signals of detectors according to a preset numerical processing algorithm and outputs Gray code rod position signals. The full-digital rod position measurement device and method disclosed by the present disclosure may effectively reduce the complexity of the primary excitation circuit and the secondary measurement signal processing circuit of the detectors, and improve the operation reliability and measurement accuracy of the rod position processing equipment.

Control rod drives include linearly-moveable control elements inside an isolation barrier. Control rod drives move the control element through a motor and rotor powering a linear screw internal to an isolation barrier. Induction coils may generate magnetic fields and be moveable across a full stroke length of the control element in the reactor. The magnetic fields hold closed a releasable latch to disconnect the control elements from the linear drives. A control rod assembly may join to the control element. The control rod assembly may lock with magnetic overtravel latches inside the isolation barrier to maintain an overtravel position. Overtravel release coils outside the isolation barrier may release the latches to leave the overtravel position. Operation includes moving the magnetic fields and releasable latch together on opposite sides of an isolation barrier to drive the control element to desired insertion points, including full insertion by gravity following de-energization.

Control rod drives include linearly-moveable control elements inside an isolation barrier. Control rod drives move the control element through a motor and rotor powering a linear screw internal to an isolation barrier. Induction coils may generate magnetic fields and be moveable across a full stroke length of the control element in the reactor. The magnetic fields hold closed a releasable latch to disconnect the control elements from the linear drives. A control rod assembly may join to the control element. The control rod assembly may lock with magnetic overtravel latches inside the isolation barrier to maintain an overtravel position. Overtravel release coils outside the isolation barrier may release the latches to leave the overtravel position. Operation includes moving the magnetic fields and releasable latch together on opposite sides of an isolation barrier to drive the control element to desired insertion points, including full insertion by gravity following de-energization.

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 mobile modular reactor, in particular, a graphite-moderated fission reactor, has an active core region and at least a portion of control region(s) that are located within an interior volume of a pressure vessel. Flow annulus features located in the flow annulus between an outer surface of the control rod/fuel rod and an inner surface of the cladding of the channel in which the rod is located stabilizes the flow annulus and maintains a reliable concentricity between the inner and outer claddings that envelope the flow annulus. Flow annulus features are equally circumferentially spaced at longitudinally separated locations and the flow annulus features at successive, longitudinally separated locations are rotationally offset relative to each other. For purposes of transportability, the pressure vessel is sized for mobile transport using a ship, train or truck, for example, by fitting within a shipping container.

A mobile modular reactor, in particular, a graphite-moderated fission reactor, has an active core region and at least a portion of control region(s) that are located within an interior volume of a pressure vessel. Flow annulus features located in the flow annulus between an outer surface of the control rod/fuel rod and an inner surface of the cladding of the channel in which the rod is located stabilizes the flow annulus and maintains a reliable concentricity between the inner and outer claddings that envelope the flow annulus. Flow annulus features are equally circumferentially spaced at longitudinally separated locations and the flow annulus features at successive, longitudinally separated locations are rotationally offset relative to each other. For purposes of transportability, the pressure vessel is sized for mobile transport using a ship, train or truck, for example, by fitting within a shipping container.

A control assembly for a nuclear reactor includes a first reactivity control assembly having a first neutron modifying material, a second reactivity control assembly having a second neutron modifying material, and at least one drive mechanism coupled to the first neutron modifying material and the second neutron modifying material. The first neutron modifying material and the second neutron modifying material are selectively repositionable relative to a fuel region of the nuclear reactor. The at least one drive mechanism is configured to provide the first neutron modifying material and the second neutron modifying material in different directions through the fuel region thereby shifting a flux distribution within the fuel region away from the second neutron modifying material.