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 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.

Abstract: Alternative designs for a modular test reactor are presented. In one aspect, a molten fuel salt nuclear reactor includes a vessel defining a reactor volume, the vessel being open-topped and otherwise having no penetrations. A neutron reflector is provided within the vessel and displacing at least some of the reactor volume, the neutron reflector defining a reactor core volume. A plurality of heat exchangers are contained within the vessel above the neutron reflector. A flow guide assembly is provided within the neutron reflector that includes a draft tube draft tube separating a central portion of the reactor core volume from an annular downcomer duct. Fuel salt circulates from the reactor core volume, through the heat exchangers, into the downcomer duct and then back into the reactor core volume.

Abstract: A simple nuclear reactor in which most of the reflector material is outside of the reactor vessel is described. The reactor vessel is a cylinder that contains all of the fuel salt and a displacement component, which may be a reflector, in the upper section of the reactor vessel. Other than the displacement component, the reflector elements including a radial reflector and a bottom reflector are located outside the vessel. The salt flows around the outside surface of the displacement component through a downcomer heat exchange duct defined by the exterior of the displacement component and the interior surface of the reactor vessel. This design reduces the overall size of the reactor vessel for a given volume of salt relative to designs with internal radial or bottom reflectors.

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: 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: 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 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: 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: Alternative designs for a modular test reactor are presented. In one aspect, a molten fuel salt nuclear reactor includes a vessel defining a reactor volume, the vessel being open-topped and otherwise having no penetrations. A neutron reflector is provided within the vessel and displacing at least some of the reactor volume, the neutron reflector defining a reactor core volume. A plurality of heat exchangers are contained within the vessel above the neutron reflector. A flow guide assembly is provided within the neutron reflector that includes a draft tube draft tube separating a central portion of the reactor core volume from an annular downcomer duct. Fuel salt circulates from the reactor core volume, through the heat exchangers, into the downcomer duct and then back into the reactor core volume.

Abstract: A simple nuclear reactor in which most of the reflector material is outside of the reactor vessel is described. The reactor vessel is a cylinder that contains all of the fuel salt and a displacement component, which may be a reflector, in the upper section of the reactor vessel. Other than the displacement component, the reflector elements including a radial reflector and a bottom reflector are located outside the vessel. The salt flows around the outside surface of the displacement component through a downcomer heat exchange duct defined by the exterior of the displacement component and the interior surface of the reactor vessel. This design reduces the overall size of the reactor vessel for a given volume of salt relative to designs with internal radial or bottom reflectors.

Abstract: A molten salt reactor includes a nuclear reactor core for sustaining a nuclear fission reaction fueled by a molten fuel salt. A molten fuel salt control system removes a volume of the molten fuel salt from the nuclear reactor core to maintain a reactivity parameter within a range of nominal reactivity. The molten fuel salt control system includes a molten fuel salt exchange system that fluidically couples to the nuclear reactor core and exchanges a volume of the molten fuel salt with a volume of a feed material containing a mixture of a selected fertile material and a carrier salt. The molten fuel salt control system can include a volumetric displacement control system having one or more volumetric displacement bodies insertable into the nuclear reactor core. Each volumetric displacement body can remove a volume of molten fuel salt from the nuclear reactor core, such as via a spill-over system.

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.

Abstract: A molten chloride fast reactor (MCFR) includes a plurality of reflectors defining a central core having a core geometric center. A flow channel fluidically connected to the central core. The flow channel includes an outlet flow channel downstream of the central core and an inlet flow channel upstream from the central core. A primary heat exchanger (PHX) disposed outside the central core and between the outlet flow channel and the inlet flow channel. The MCFR also includes a decay heat heat exchanger (DHHX). At least a portion of the DHHX is disposed above the core geometric center, and a fuel salt is configured to circulate at least partially through the outlet flow channel, the DHHX, the PHX, the inlet flow channel, and the central core.

Abstract: Designs for a low power, fast spectrum molten fuel nuclear reactor that can be used to advance the understanding of molten salt reactors, their design and their operation are described. Furthermore, the designs described may be adapted to extra-terrestrial use as described herein for use as a low-gravity, moon-, Mars-, or space-based power generator. These low power reactors include a reactor core volume defined by a radial neutron reflector enclosed in a reactor vessel, in which heated fuel salt flows from the reactor core through a duct between the radial neutron reflector and the reactor vessel and back into the reactor core. Heat generated from the fission in the reactor core is transferred from the molten fuel through the reactor vessel to a coolant, in the case of an experimental design, or directly to an extra-terrestrial environment, in the case of an extra-terrestrial design.

Abstract: This disclosure describes various configurations and components of a molten fuel fast or thermal nuclear reactor in which one or more primary heat exchangers are located above the reactor core of the nuclear reactor.

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.

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: Configurations of molten fuel salt reactors are described that utilize neutron-reflecting coolants or a combination of primary salt coolants and secondary neutron-reflecting coolants. Further configurations are described that circulate liquid neutron-reflecting material around a reactor core to control the neutronics of the reactor. Furthermore, configurations which use the circulating neutron-reflecting material to actively cool the containment vessel are also described. A further configuration is described that utilizes a core barrel between a reactor core volume of molten fuel salt and a reflector volume, in which the reflector volume contains a plurality of individual reflector elements separated by an interstitial space filled with molten fuel salt.

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.