Abstract: This disclosure describes various configurations and components of a molten fuel fast or thermal nuclear reactor for managing the operating temperature in the reactor core. The disclosure includes various configurations of direct reactor auxiliary cooling system (DRACS) heat exchangers and primary heat exchangers as well as descriptions of improved flow paths for nuclear fuel, primary coolant and DRACS coolant through the reactor components.

Abstract: Disclosed embodiments include nuclear fission reactor cores, nuclear fission reactors, methods of operating a nuclear fission reactor, and methods of managing excess reactivity in a nuclear fission reactor.

Abstract: A method for depositing zinc on the surfaces of a coolant loop of a nuclear power plant includes: providing within a portion of the coolant loop a treatment solution comprising zinc and optionally one or more noble metals and/or reducing agent(s); allowing the treatment solution to remain in the portion for a treatment period; and removing the treatment solution from the portion. According to various embodiments, an average temperature of the treatment solution over the course of the treatment period is less than 150° C. or 100° C. According to various embodiments, an instantaneous temperature of the treatment solution remains below 150° C. or 100° C. throughout the treatment period. The zinc deposition treatment may be applied (1) before the plant is first put into power-generating operation or (2) during an outage following power-generating operation and optionally following a chemical decontamination to remove any oxides formed on surfaces of a coolant loop during prior power operation period(s).

Abstract: A nuclear reactor comprises a pressure vessel containing a nuclear reactor core. A reactor core cooling system comprises a standpipe including a plurality of orifices in fluid communication with a refueling water storage tank (RWST) to drain water from the RWST into the standpipe, and an injection line configured to drain water from the standpipe to the pressure vessel. In some embodiments the standpipe is disposed in the RWST, while in other embodiments the standpipe is disposed outside of the RWST and cross-connection pipes connect the plurality of orifices with the RWST. The reactor core cooling system may further comprise a valve configured to control flow through one orifice of the plurality of orifices in fluid communication with the RWST based on water level in the standpipe. The valve may comprise a float valve having its float disposed in the standpipe.

Abstract: A rotation apparatus is usable with a control drum in a nuclear environment. The control drum is situated on a shaft that is rotatable about a horizontal axis of rotation, and the control drum includes an absorber portion and a reflector portion. The rotation apparatus includes a rotation mechanism that is structured to apply to the shaft in an operational position a force that biases the shaft to rotate toward a shutdown position, with the force being resisted by a motor to retain the shaft in the operational position when the motor is powered. The force is not resisted when the motor is unpowered. The rotation apparatus further includes a rotation management system that controls the rotation of the shaft.

Abstract: A fuel assembly for a nuclear reactor having an upstream minor portion defining an upstream end, a main portion, and a downstream minor portion defining a downstream end. Fuel rods extend in a flow interspace permitting a flow of coolant through the fuel assembly in contact with the fuel rods. Two elongated tubes form a respective internal passage extending in parallel with the fuel rods and enclosing a stream of the coolant. Each elongated tube having a bottom, an inlet at the upstream minor portion and an outlet at the downstream minor portion. Each elongated tube having an inlet pipe having an inlet end and an outlet end in the internal passage at a distance from the bottom, thereby forming a space in the internal passage between the outlet end and the bottom.

Abstract: Configurations of molten fuel salt reactors are described that allow for active cooling of the containment vessel of the reactor by the primary coolant. Furthermore, naturally circulating reactor configurations are described in which the reactor cores are substantially frustum-shaped so that the thermal center of the reactor core is below the outlet of the primary heat exchangers. Heat exchanger configurations are described in which welded components are distanced from the reactor core to reduce the damage caused by neutron flux from the reactor. Radial loop reactor configurations are also described.

Abstract: An irradiation target for the production of radioisotopes, comprising at least one plate defining a central opening and an elongated central member passing through the central opening of the at least one plate so that the at least one plate is retained thereon, wherein the at least one plate and the elongated central member are both formed of materials that produce molybdenum-99 (Mo-99) by way of neutron capture.

Abstract: An aqueous assembly has a negative coefficient of reactivity with a magnitude. The aqueous assembly includes a vessel and an aqueous solution, with a fissile solute, supported in the vessel. A reactivity stabilizer is disposed within the aqueous solution to reduce the magnitude of the negative coefficient of reactivity of the aqueous assembly during operation of the aqueous assembly.

Abstract: A nuclear reactor decommissioning system according to an embodiment includes a cutting device to cut a reactor, a lifting device inserted inside the reactor to lift the reactor, and a shielding device that is positioned between the reactor and the lifting device and blocks radioactive dust generated by the cutting device from spreading.

Abstract: An integrated passive cooling containment structure for a nuclear reactor includes a concentric arrangement of an inner steel cylindrical shell and an outer steel cylindrical shell that define both a lateral boundary of a containment environment of the nuclear reactor that is configured to accommodate a nuclear reactor and an annular gap space between the inner and outer steel cylindrical shells, a concrete donut structure at a bottom of the annular gap space, and a plurality of concrete columns spaced apart azimuthally around a circumference of the annular gap and extending in parallel from a top surface of the concrete donut structure to a top of the annular gap space. The outer and inner steel cylindrical shells and the concrete donut structure at least partially define one or more coolant channels extending through the annular gap space.

Abstract: A dry cask storage system for spent nuclear fuel includes a detection apparatus having a resonant electrical circuit, with resonant electrical circuit being situated within an interior region of a metallic vessel wherein the SNF is situated. The detection apparatus includes a transmitter that generates an excitation pulse that causes the resonant circuit to resonate and to generate a response pulse. The resonant circuit includes an inductor that is formed with a core whose magnetic permeability varies with temperature such that the frequency of the resonant circuit varies as a function of temperature. The response pulse is then used to determine the temperature within the interior of the vessel where the SNF is situated. Pressure detection is also provided.

Abstract: According to some embodiments, a system for widening and densifying a scrape-off layer (SOL) in a field reversed configuration (FRC) fusion reactor is disclosed. The system includes a gas box at one end of the reactor including a gas inlet system and walls of suitable heat bearing materials. The system further includes an exit orifice adjoining the gas box, wherein the exit orifice has a controllable radius and length to allow plasma to flow out from the gas box to populate the SOL with the plasma. The system may also include fusion products, which decrease in speed in the plasma in the SOL, allowing energy to be extracted and converted into thrust or electrical power and further allowing ash to be extracted to reduce neutron emissions and maintain high, steady-state fusion power.

Abstract: A coolant having a set temperature is fed into the nuclear reactor core of a medical neutron source, which is in a subcritical state. The nuclear reactor core is transitioned from the subcritical state to a critical state until the nominal power of the nuclear reactor is achieved. A neutron output channel is opened in order to conduct a neutron therapy session, and the operation of the reactor is maintained at nominal power while the neutron therapy session is conducted. At the end of the session, the neutron output channel is closed at the same time as the reactor core is transitioned to a subcritical state. The temperature of the coolant entering the core is maintained unchanged and equal to a set temperature, both when the core is transitioned to a critical state and during the operation of the nuclear reactor at nominal power.

Abstract: A nuclear reactor has a core installed on a lower core plate and formed from multiple fuel assemblies, each fuel assembly including a structural cage assembly. The structural cage assembly has an upper end fitting, mid grids, and a lower end fitting (LEF). The LEF positions the fuel assembly using four locating pins located at each corner of the LEF. The pins position the fuel assembly laterally by mating with receiving holes in the lower core plate. The locating pins have a chamfered tip with a flat end. The chamfered tip allows for a greater positioning margin when installing the fuel assembly in the core by guiding the pins into holes in the lower core plate, and the flat tip provides strength and stability in case the assembly is inadvertently rested on the tip of the pin instead of the LEF pads.

Abstract: In a panel that uses the gamma radiation emitted by fission to produce electrical power, a source of an electrical current is connected to a layer of the panel made of a metal with a relatively high atomic number (Z) that forms an electron emitter. The emitter layer is surrounded by an insulation layer which in turn is surrounded by a relatively low Z value layer for collecting electrons from the emitter. Another layer of insulation and an outer sheath surround the collector. The improved panel may be used for reactor power level and power distribution measurements, and for initiating, maintaining or returning molten salt or metal coolants in the liquid state.

Abstract: A nuclear reactor in one embodiment includes a cylindrical body having an internal cavity, a nuclear fuel core, and a shroud disposed in the cavity. The shroud comprises an inner shell, an outer shell, and a plurality of intermediate shells disposed between the inner and outer shells. Pluralities of annular cavities are formed between the inner and outer shells which are filled with primary coolant such as demineralized water. The coolant-filled annular cavities may be sealed at the top and bottom and provide an insulating effect to the shroud. In one embodiment, the shroud may comprise a plurality of vertically-stacked self-supported shroud segments which are coupled together.

Abstract: Provided is a statistical overpower penalty calculation system for a generic thermal margin analysis model, the system including: a random number generating unit generating a plurality of random numbers; an power distribution generating unit generating power information of an axial direction and a radial direction for a core burnup; an operating condition generating unit extracting an arbitrary value for a plurality of operating conditions from the random number generated above; a POL calculating unit calculating a POL of a reload core thermal margin analysis model and a POL of a generic thermal margin analysis model and calculating a plurality of the overpower penalties through the POLs; and a statistics processing unit calculating tolerance limit values according to the core burnup by statistically analyzing a distribution formed of the plurality of the overpower penalties and selecting a smallest tolerance limit value as a representative value of the overpower penalties.

Abstract: Control rod drives include all-digital monitoring, powering, and controlling systems for operating the drives. Each controlling system includes distinct microprocessor-driven channels that independently monitor and handle control rod drive position information reported from multiple position sensors per drive. Controlling systems function as rod control and information systems with top-level hardware interfaced with nuclear plant operators other plant systems. The top-level hardware can receive operator instructions and report control rod position, as well as report errors detected using redundant data from the multiple sensors. Positional data received from each drive is multiplexed across plural, redundant channels to allow verification of the system using independent position data as well as operation of the system should a single channel or detector fail.

Abstract: A radionuclide generation system including a tube system configured to permit insertion and removal of irradiation targets into an instrumentation finger of a nuclear reactor, and an irradiation target drive system configured to insert the irradiation targets into the instrumentation finger and to remove the irradiation targets from the instrumentation finger. The radionuclide generation system further includes an instrumentation and control unit which is linked to an online core monitoring system and being configured to calculate optimal irradiation locations for the irradiation targets based on the actual state of the reactor as provided by the online core monitoring system.