Abstract: A nuclear reactor includes a passive reactivity control nuclear fuel device located in a nuclear reactor core. The passive reactivity control nuclear fuel device includes a multiple-walled fuel chamber having an outer wall chamber and an inner wall chamber contained within the outer wall chamber. The inner wall chamber is positioned within the outer wall chamber to hold nuclear fuel in a molten fuel state within a high neutron importance region. The inner wall chamber allows at least a portion of the nuclear fuel to move in a molten fuel state to a lower neutron importance region while the molten nuclear fuel remains within the inner wall chamber as the temperature of the nuclear fuel satisfies a negative reactivity feedback expansion temperature condition. A duct contains the multiple-walled fuel chamber and flows a heat conducting fluid through the duct and in thermal communication with the outer wall chamber.

Abstract: A nuclear reactor is configured with a primary coolant loop for transferring heat away from the nuclear reactor core. In a shutdown event, the primary coolant pump may stop pumping primary coolant through the reactor core, resulting in decay heat buildup within the reactor core. An inertial energy coast down system can store kinetic energy while the nuclear reactor is operating and then release the stored kinetic energy to cause the primary coolant to continue to flow through the nuclear reactor core to remove decay heat. The inertial energy coast down system may include an impeller and a flywheel having a mass. During normal reactor operation, the flowing primary coolant spins up the impeller and flywheel, and upon a shutdown event where the primary coolant pump stops pumping, the flywheel and impeller can cause the primary coolant to continue to flow during a coast down of the flywheel and impeller.

Abstract: An integrated energy system includes a nuclear thermal plant situated on a nuclear site. The nuclear thermal plant produces thermal energy that is transported to a thermal energy storage system located outside the nuclear site. The thermal storage system is thermally coupled to a power generation system which is also remote to the nuclear site. By this arrangement, the nuclear thermal plant is isolated and decoupled from the power generation system. The nuclear thermal plant may supply thermal energy upwards of 800° C. or more to be stored at the thermal energy storage system until needed such as for industrial heat, power generation, or other uses. The thermal storage system is source agnostic, and one or more additional thermal energy generators, such as additional nuclear reactors, solar thermal plants, or other thermal energy generators can be coupled to a common thermal storage system and power generation system.

Abstract: A curvilinear electromagnetic pump is configured to follow a curve, such as by coupling multiple linear pump segments together that are offset by an angle with respect to each other. The curvilinear electromagnetic pump can curve within two dimensions, or within three dimensions. The curvilinear electromagnetic pump allows for more efficient arrangement of components and systems within a nuclear reactor vessel and allows a significantly reduced reactor vessel height as compared to a linear pump arranged vertically. The curvilinear electromagnetic pump may follow the curvature of the reactor vessel wall and may be entirely disposed near the bottom of the reactor vessel.

Abstract: An anti-proliferation technique is disclosed to reduce the likelihood of nuclear proliferation due to the use fissionable fuel salts. The technique includes doping the fuel salt with one or more elements (referred to herein as activation dopants) that, upon exposure to neutrons such as would occur in the fuel salt when a reactor is in operation, undergo a nuclear reaction to, directly or indirectly, form highly active “protecting isotopes” (of the same element as the activation dopant or a different element). A sufficient mass of activation dopants is used so that the Figure of Merit (FOM) of the fuel salt is decreased to below 1.0 within some target number of days of fission. This allows the FOM of the fuel salt to be controlled so that the fuel becomes too dangerous to handle before to the creation of a significant amount of weaponizable isotopes.

Abstract: Embodiments of methods for improving mesophase pitch for carbon fiber production using supercritical carbon dioxide are described. The methods improve the relative amount and quality of mesophase pitch in feedstocks, such as coal tar, already having at least some mesophase pitch. One particular method includes performing a sCO2/toluene extraction on the coal tar to obtain a toluene insoluble fraction of the coal tar; mixing the toluene insoluble fraction with sCO2 to obtain a sCO2/toluene insoluble fraction mixture; and extruding the sCO2/toluene insoluble fraction mixture, thereby separating the sCO2 from the toluene insoluble fraction to obtain fibers of mesophase pitch.

Abstract: A vaporizer includes an outer tube configured to receive a flow of heated gas and an inner tube disposed at least partially within the outer tube. The inner tube is spaced apart from the outer tube such that the flow of heated gas is channeled through an annular space therebetween. The vaporizer also includes a crucible disposed at least partially within the inner tube. The crucible is extendable and retractable relative to the inner tube and within the outer tube. The crucible is configured to hold a molten metal such that a surface area of the molten metal exposed to the flow of heated gas is adjustable based on the position of the crucible relative to the inner tube. A heater is configured to vaporize the molten material and the vapor mixes with the flow of heated gas.

Abstract: This document describes a method for reducing the corrosivity of certain magnesium salts. The salt product resulting from the method exhibits reduced corrosion of steels that come into contact with the salt relative to salt compositions that are not so treated. This makes such treated salts more efficient coolant salts as they will require less equipment replacement over time. The method uses magnesium metal to reduce unwanted impurities in the salts the reduced impurities are then removed as either gas or precipitate from the now purified salt. Without being bound to one particular theory, it is believed that the reduction of the level of impurities in the salt results in a salt with substantially reduced corrosiveness to steel.

Abstract: A method, system, and apparatus for the thermal storage of nuclear reactor generated energy including diverting a selected portion of energy from a portion of a nuclear reactor system to an auxiliary thermal reservoir and, responsive to a shutdown event, supplying a portion of the diverted selected portion of energy to an energy conversion system of the nuclear reactor system.

Abstract: A fast neutron nuclear reactor contains a nuclear reactor core having an array of device locations. Some device locations in the nuclear reactor core contain fissile and fertile nuclear fuel assembly devices. One or more other device locations in the nuclear reactor core contain Doppler reactivity augmentation devices that amplify the negativity of the Doppler reactivity coefficient within the nuclear reactor core. In some implementations, a Doppler reactivity augmentation device can also reduce the coolant temperature coefficient within the nuclear reactor core. Accordingly, a Doppler reactivity augmentation device contributes to a more stable nuclear reactor core.

Abstract: Targetry coupled separation refers to enhancing the production of a predetermined radiation product through the selection of a target (including selection of the target material and the material's physical structure) and separation chemistry in order to optimize the recovery of the predetermined radiation product. This disclosure describes systems and methods for creating (through irradiation) and removing one or more desired radioisotopes from a target and further describes systems and methods that allow the same target to undergo multiple irradiations and separation operations without damage to the target. In contrast with the prior art that requires complete dissolution or destruction of a target before recovery of any irradiation products, the repeated reuse of the same physical target allowed by targetry coupled separation represents a significant increase in efficiency and decrease in cost over the prior art.

Abstract: A fuel element has a ratio of area of fissionable nuclear fuel in a cross-section of the tubular fuel element perpendicular to the longitudinal axis to total area of the interior volume in the cross-section of the tubular fuel element that varies with position along the longitudinal axis. The ratio can vary with position along the longitudinal axis between a minimum of 0.30 and a maximum of 1.0. Increasing the ratio above and below the peak burn-up location associated with conventional systems reduces the peak burn-up and flattens and shifts the burn-up distribution, which is preferably Gaussian. The longitudinal variation can be implemented in fuel assemblies using fuel bodies, such as pellets, rods or annuli, or fuel in the form of metal sponge and meaningfully increases efficiency of fuel utilization.

Abstract: A nuclear reactor includes a heat exchanger that transfers thermal energy from a primary reactor coolant to a secondary coolant. The heat exchanger is formed with a hot flow channel, a cold flow channel, and a porous layer between the hot flow channel and the cold flow channel. The porous layer may be thermally insulative to reduce the efficiency of thermal energy transfer from the hot flow channel to the cold flow channel. The porous layer may have a control gas passed therethrough that can be tailored to control the thermal energy transfer through the porous layer. The control gas can be tested for leakage within the heat exchanger. The control gas may also be used to sequester fission or activation products.

Abstract: A nuclear reactor is designed to couple the load path of control elements with the reactor core, thus reducing opportunity for differential movement between the control elements and the reactor core. A core barrel can be fabricated in a manufacturing facility to include the reactor core, control element supports, and control element drive system. The core barrel can be mounted to a reactor vessel head. Movement, such as through seismic forces, transmits an equal direction and magnitude to the control elements and the reactor core, thus inhibiting the opportunity for differential movement.

Abstract: A molten fuel reactor includes a reactor core having substantially a right-circular cylinder shape with a longitudinal axis. At least one inlet is configured to channel fuel salt into the reactor core. At least one outlet is configured to channel fuel salt out of the reactor core, and the inlet and outlet at least partially define a flow loop of fuel salt with respect to the reactor core. An orifice ring plate is disposed within the reactor core and proximate the at least one inlet. The orifice ring plate is configured to condition a flow of fuel salt entering the reactor core from the at least one inlet. The orifice ring plate extends circumferentially about the longitudinal axis and has a height defined in a direction along the longitudinal axis. The orifice ring plate includes a plurality of apertures configured to allow the flow of fuel salt therethrough.

Abstract: A method for replacing a cesium trap includes freezing the cesium trap which partially contains cesium and is located within a shielded cell and. The cesium trap is then decoupled and removed from the shielded cell. A second cesium trap is inserted into the shielded cell and attached to the shielded cell.

Abstract: Methods and systems for stabilizing spent fuel assemblies from sodium-cooled nuclear reactors using Zamak are described herein. It has been determined that there is a synergism between Zamak and sodium that allows Zamak to form thermally-conductive interface with the sodium-wetted surfaces of the fuel assemblies. In the method, one or more spent fuel assemblies are removed from the sodium coolant pool and placed in a protective sheath. The remaining volume of the sheath is then filled with liquid Zamak. To a certain extent Zamak will dissolve and alloy with sodium remaining on the fuel assemblies. Excess sodium that remains undissolved is displaced from the sheath by the Zamak fill. The Zamak is then cooled until solid and the sheath sealed. The resulting Zamak-stabilized spent fuel assembly is calculated to have sufficient internal thermal conductivity to allow it to be stored and transported without the need for liquid cooling.

Abstract: A molten fuel salt nuclear reactor core assembly including a fluid neutron reflecting material defining a fast spectrum fuel volume configured to breed fissile fuel from fertile fuel, a first inlet channel, and a first outlet channel through which cooled molten fuel salt can enter and heated molten fuel salt can exit the fast spectrum fuel volume. The core assembly also includes a set of neutron absorbing members sized to fit within the fast spectrum fuel volume. The set of neutron absorbing members define a thermal spectrum fuel volume for a fission reaction of the fissile fuel, a second inlet channel, and a second outlet channel through which cooled molten fuel salt can enter and heated molten fuel salt can exit the thermal spectrum fuel volume.

Abstract: A nuclear reactor is configured with an intermediate coolant loop for transferring thermal energy from the reactor core for a useful purpose. The intermediate coolant loop includes a bypass flowpath with an air heat exchanger for dumping reactor heat during startup and/or shutdown. A fluidic diode along the bypass flowpath asymmetrically restricts flow across the bypass flowpath, inhibiting flow in a first flow direction during a full power operating condition and allowing a relatively uninhibited flow in a second direction during a startup and/or shut down low power operating condition.

Abstract: A reflector assembly for a molten chloride fast reactor (MCFR) includes a support structure with a substantially cylindrical base plate, a substantially cylindrical top plate, and a plurality of circumferentially spaced ribs extending between the base plate and the top plate. The support structure is configured to encapsulate a reactor core for containing nuclear fuel. The MCFR also includes a plurality of tube members disposed within the support structure and extending axially between the top plate and the bottom plate. The plurality of tube members are configured to hold at least one reflector material to reflect fission born neutrons back to a center of the reactor core.