Abstract: A method for measuring drop time of a control rod cluster integrated with a rod position measurement device is provided, wherein the method is used to measure the drop time of the control rod cluster, and includes following steps. A voltage Ua of coils in Group A is monitored to capture a rod cluster drop signal. A point (tmax, Vmax) with a maximum drop speed is searched. An end of a time period when the control rod cluster starts to drop is retroactively calculated from tmax. A start of the time period when the drop reference signal DROPref drops from a maximum value to 33% thereof is retroactively searched from a minimum value point of a drop reference signal DROPref. A time point t6 when a drop speed of the control rod cluster is lower than 0 is determined from tmax forward.

Abstract: A method of repairing a divertor or first wall surface in a tokamak plasma vessel. The divertor or first wall surface comprises a refractory metal having a melting point of at least 2000° C. A pressure of less than 25 mbar is maintained within the plasma vessel following the end of operation of the plasma vessel. The refractory metal is deposited onto the divertor or first wall surface within the plasma vessel via a deposition process which is one of: additive manufacturing; physical vapour deposition; thermal spray; arc ion plating; diode laser cladding; and chemical vapour deposition.

Abstract: A reactor unit cell is disclosed including a graphite moderator structure, a heat pipe positioned in the graphite moderator structure, and a fuel assembly positioned in the graphite moderator structure. The fuel assembly comprises a beryllium-oxide sleeve and nuclear fuel positioned in the beryllium-oxide sleeve.

Abstract: A nuclear fuel rod comprises nuclear fuel contained in a cladding, the cladding comprising a tube and two plugs, the tube extending along a central axis and having two ends, each plug being attached to a corresponding end of the tube by sealing the end of the tube. The tube is covered by a tube coating extending over the entire length of the tube from one end of the tube to the other.

Abstract: A system for mitigating and/or preventing potential fire hazards in a nuclear reactor including a heat pipe reactor core is provided. The system further comprises a plurality of heat pipes, the heat pipe reactor core engaging the plurality of heat pipes between first and second ends of each respective heat pipe. A heat exchanger device defining an enclosed gas chamber annularly surrounds at least a portion of at least one heat pipe. The system further comprises a first valve and a second valve positioned proximate the first end of the at least one heat pipe, the first valve fluidly coupling the at least one heat pipe to a first suppressant chamber and the second valve fluidly coupling the enclosed gas chamber to a second suppressant chamber. Each of the first and second valves is movable between open and closed positions to regulate the flow of fire suppressant material from the first and second suppressant chambers, respectively.

Abstract: Disclosed herein is a nuclear reactor system comprising a vessel encompassing a reactor core. An external loop line is connected to top and bottom portions of the vessel. A pump can circulate molten fuel through the reactor core and the external loop line. An external neutron reflector encompasses the vessel. External heaters heat the loop line and the reflector. The loop line, the reactor, or both, may be covered with insulation.

Abstract: An integrated control logic device and an operating method thereof adjust a position of a main control valve and a position of an auxiliary control valve. In particular, the position of the auxiliary control valve is adjusted by determining whether a change in the position of the main control valve is in a preset deadband range, thereby preventing a periodic water level fluctuation of a steam generator of a nuclear power plant.

Abstract: A method for determining real-time thermal power of a nuclear reactor based on number of gamma rays counted comprising measuring a number of gamma-ray counts by a gamma-ray detector that is placed outside a biological shield at a primary cooling circuit of a fission nuclear power plant so that maintenance of the detector is possible during normal operation of the fission nuclear power plant, and determining, by a computing device in real-time, a thermal power of the fission nuclear power plant based on the number of gamma-ray counts measured by the gamma-ray detector.

Abstract: A BWR channel box comprises a substrate, a first layer, and a second layer. The substrate comprises silicon carbide fibers. The first layer is deposited on a first surface of the substrate. The second layer is deposited on an opposite second surface of the substrate. Each layer comprises a corrosion resistant metallic composition. The combined weight of both layers is in a range from greater than 0% to 10% of the total weight of the channel box.

Abstract: A method of synthesizing reactor core power distribution is disclosed. According to the method, the power of all fuel assemblies in a reactor core is calculated from powers of fuel assemblies in which in-core instruments are located using the ordinary kriging methodology. Also, a hot-pin power distribution of each fuel assembly is synthesized from the power of all fuel assemblies calculated, whereby more accurate hot-pin axial power distribution, rather than pseudo hot-pin axial power distribution, may be synthesized.

Abstract: A fuel assembly includes a plurality of elongated fuel elements. Each of the plurality of fuel elements has a spirally twisted, multi-lobed profile that defines a plurality of spiral ribs. Each of the plurality of fuel elements has a fuel kernel that includes fuel material disposed in a matrix of metal non-fuel material. The fuel material includes fissile material. A cladding surrounds the fuel kernel. A moderator: fuel ratio in a region of the fuel elements is 2.4 or less. The moderator: fuel ratio is an area ratio within a cross-section that is perpendicular to longitudinal axes of the plurality of fuel elements and extends through the plurality of fuel elements. The area ratio is a ratio of: (1) a total area available for moderator flow for the plurality of fuel elements to (2) a total area of the fuel kernels of the plurality of fuel elements.

Abstract: A nuclear reactor includes a reactor vessel containing an alkali metal thermoelectric converter. The bottom part of the vessel contains liquid alkali metal. A reactor core is arranged in the vessel and includes fuel rods. The surface of each fuel rod is provided with a first liquid absorption core. The bottom part of the reactor core is provided with second liquid absorption cores which are connected to the first liquid absorption cores. The cores are together configured to use capillary action to pump liquid alkali metal to an upper portion of an outer surface of the fuel rods, where the liquid alkali metal is vaporized into alkali metal vapor. The converter divides the inside of the reactor vessel into a high-pressure vapor chamber and a low-pressure vapor chamber. The converter is configured to receive alkali metal vapor from the high-pressure vapor chamber for use in electric power generation.

Abstract: A nuclear reactor system includes a drillhole that extends from a terranean surface through one or more subterranean formations. The nuclear reactor system includes a reactor core positioned in the drillhole, the reactor core comprising at least one nuclear fuel element. The nuclear reactor system includes a primary coolant system configured to transport a primary fluid coolant between the reactor core and a heat exchanger. The nuclear reactor system includes a secondary coolant system thermally coupled to the primary coolant system via the heat exchanger and configured to transport a secondary fluid coolant between the heat exchanger and the terranean surface.

Abstract: A core of a fast nuclear reactor has at least one gas expansion module, at least one neutron absorber, and at least one neutron moderator. The gas expansion module has a hollow tubular structure with one end closed and the other end opened. The at least one neutron absorber adjoins an outer face, in a radial direction of the core, of each gas expansion module. The at least one neutron moderator adjoins an outer face, in a radial direction of the core, of each gas expansion module. The at least one neutron absorber also adjoins the at least one neutron moderator.

Abstract: A molten fuel salt reactor system includes a fluid level control system configured to circulate a molten salt through a molten salt loop including an experimental tank, a sump tank, and a drain tank. The fluid level control system further includes a plurality of level sensors, pressure transducers, and electronic pressure regulators fluidically coupled with the fuel salt reactor system. The fluid level control system is configured to receive cover gas pressures in the headspaces of the tanks and calculate target fluid height setpoints for each of the tanks. The fluid level control system further invokes the electronic pressure regulator to iteratively adjust the cover gas pressures of the tanks to achieve and maintain a target fluid level in the experimental tank.

Abstract: A method for plasma magneto-inertial fusion. A trigger breakdown time is determined for each of a plurality of solid-state switch arrays by measuring a duration time from initiation of a control signal to plasma formation for each of a plurality of pulsed power driven electromagnetic particle accelerators. The particle accelerators are positioned to converge corresponding plasma discharges towards a parametrically defined volume. A timing profile is generated for each of the particle accelerators based on the trigger breakdown times. Timing offsets are determined for each of the switch arrays based on their trigger breakdown time to compensate for timing variations among the particle accelerators. The switch arrays are triggered in accordance with their timing offsets to converge the corresponding plasma discharges towards the defined volume.

Abstract: A liquid metal cooled nuclear reactor includes a passive decay heat removal system having thermal insulation attached to a wall of a cold source reservoir that holds a phase change material, where the insulation is arranged to automatically fall by gravity from the wall in response to the wall reaching a predetermined temperature. The nuclear reactor may be a fast neutron reactor that incorporates an integral system having a final cold source with a reservoir incorporating an integral exchanger divided into a plurality of parallel tubes between which a phase change material is inserted, the reservoir being surrounded by a thermal insulating layer that can be detached in a passive manner in the event of reaching a predetermined threshold temperature.

Abstract: A micro nuclear reactor includes a core filled with nuclear fuel particles mixed with moderator particles. A heat pipe extends into the core and transfers heat generated by the core. A power converter receives heat from the heat pipe and converts thermal energy into electrical energy. A valve is configured to open and close an outlet located at a lower portion of the core. When the valve is open the nuclear fuel and the moderator are discharged by gravity from the core through the outlet.

Abstract: A maintenance method is applied to a nuclear reactor having a drive assembly for a control rod assembly. The drive assembly includes a casing for receiving a drive rod lifting mechanism and a sheath for receiving the drive rod. A first lip is at an upper end of the casing, and a second lip is at a lower end of the sheath. The lips are welded together forming a seal between the casing and said sheath. The method includes removing the lips via material removal; carrying out a maintenance operation on the control rod assembly; creating a welding surface by machining the upper end of the casing; and creating a leak-tight connection between the casing and the sheath by welding the created welding surface to a matching welding surface provided at the lower end of the sheath. A replacement sheath may be used instead of the original sheath.

Abstract: In a system and method for controlling energy deposition on a surface of an Inertial Confinement Fusion (ICF) target when imploding. Providing one or more volume absorber/radiators to absorb the incident beam and reradiate x-ray radiation within the hohlraum containing the ICF target. Varying the reflectivity of the inner wall of the hohlraum wall or outer surface of the ICF target. Further suppressing non-uniformities in the x-ray radiation emitted from the one or more volume absorber/radiators upon one or more materials located on an outer surface of the ICF target or inner surface of said hohlraum.