Abstract: A method designs nuclear reactors using design variables and metric variables. A user specifies ranges for the design variables and threshold values for the metric variables and selects design parameter samples. For each sample, the method runs three processes, which compute metric variables for thermal-hydraulics, neutronics, and stress. The method applies a cost function to compute an aggregate residual of the metric variables compared to the threshold values. The method deploys optimization methods, either training a machine learning model using the samples and computed aggregate residuals, or using genetic algorithms, simulated annealing, or differential evolution. When using Bayesian optimization, the method shrinks the range for each design variable according to correlation between the respective design variable and estimated residuals using the machine learning model. These steps are repeated until a sample having a smallest residual is unchanged for multiple iterations.

Abstract: 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.

Abstract: Nuclear propulsion fission reactor structure has an active core region including fuel element structures, a reflector with rotatable neutron absorber structures (such as drum absorbers), and a core former conformal mating the outer surface of the fuel element structures to the reflector. Fuel element structures are arranged abutting nearest neighbor fuel element structures in a tri-pitch design. Cladding bodies defining coolant channels are inserted into and joined to lower and upper core plates to from a continuous structure that is a first portion of the containment structure. The body of the fuel element has a structure with a shape corresponding to a mathematically-based periodic solid, such as a triply periodic minimal surface (TPMS) in a gyroid structure. The nuclear propulsion fission reactor structure can be incorporated into a nuclear thermal propulsion engine for propulsion applications, such as space propulsion.

Abstract: A control rod assembly for a nuclear reactor having a reactor core and a pressurized fluid source, including a control rod disposed within a control rod sleeve, a lead screw that is selectively secured to the control rod, a trip latch that is secured to a bottom end of the lead screw, the trip latch being selectively securable to a top end of the control rod, a control rod drive motor that is operably connected to the lead screw, and a valve that is in fluid communication with the pressurized fluid source of the nuclear reactor and is movable between a first position and a second position, wherein in the second position of the gas valve the trip latch is in an open position.

Abstract: Nuclear propulsion fission reactor structure has an active core region including fuel element structures, a reflector with rotatable neutron absorber structures (such as drum absorbers), and a core former conformal mating the outer surface of the fuel element structures to the reflector. Fuel element structures are arranged abutting nearest neighbor fuel element structures in a tri-pitch design. Cladding bodies defining coolant channels are inserted into and joined to lower and upper core plates to from a continuous structure that is a first portion of the containment structure. The body of the fuel element has a structure with a shape corresponding to a mathematically-based periodic solid, such as a triply periodic minimal surface (TPMS) in a gyroid structure. The nuclear propulsion fission reactor structure can be incorporated into a nuclear thermal propulsion engine for propulsion applications, such as space propulsion.

Abstract: A control drum system for a nuclear reactor including a reactor core, including an ex-core reflector including a plurality of cylindrical apertures, a plurality of control drum assemblies, each control drum assembly including a drive shaft, a drum cylinder affixed to a bottom end of the drive shaft, and a planetary gear attached to a top end of the drive shaft, wherein each drum cylinder is rotatably received in a cylindrical aperture, a first control drum drive motor operably connected to a first control drum assembly, and an annular ring gear that is operably connected to the planetary gear of each of the control drum assemblies so that all the control drum assemblies rotate simultaneously.

Abstract: A method is provided for enhancing image resolution for sequences of 2-D images of additively manufactured products. For each of a plurality of additive manufacturing processes, the process obtains a respective plurality of sequenced low-resolution 2-D images of a respective product during the respective additive manufacturing process and obtains a respective high-resolution 3-D image of the respective product after completion of the respective additive manufacturing process. The process selects tiling maps that subdivide the low-resolution 2-D images and the high-resolution 3-D images into low-resolution tiles and high-resolution tiles, respectively. The process also builds an image enhancement generator iteratively in a generative adversarial network using training inputs that includes ordered pairs of low-resolution and high-resolution tiles.

Abstract: Additive manufacturing compositions include low-absorbing particles or non-absorbing particles that have an absorbance for wavelengths of 300 nm to 700 nm that is equal to or greater than 0 Au and is less 1.0 Au, such as 0.001 Au?absorbance?0.7 Au. Slurries including such particles and an uranium-containing particle and that are used in additive manufacturing processes have an increased penetration depth for curative radiation. Removal of low-absorbing particles or non-absorbing particles during post-processing of as-manufactured products results in pores that create porosity in the as-manufactured product that provide a volume accommodating fission gases and/or can enhance wicking of certain heat pipe coolant liquids.

Abstract: Plurality of layers form a nuclear fission reactor structure, each layer having an inner segment body, an intermediate segment body, and an outer segment body (each segment body separated by an interface). The layers include a plurality of cladding arms having involute curve shapes that spirally radiate outward from a radially inner end to a radially outer end. Chambers in the involute curve shaped cladding arm contain fuel compositions (and/or other materials such as moderators and poisons). The design of the involute curve shaped cladding arms and the composition of the materials conform to neutronic and thermal management requirements for the nuclear fission reactor and are of sufficiently common design and/or have sufficiently few variations as to reduce manufacturing complexity and manufacturing variability.

Abstract: A control rod drive mechanism for use in a nuclear reactor including a reactor core disposed in a pressure vessel, including a control rod configured for insertion into the reactor core, a lead screw, the control rod being secured to the bottom end of the lead screw, a drive mechanism including a torque tube having a top end and a bottom end, a pair of segment arms that are pivotably mounted to the torque tube, a pair of roller nuts, each roller nut being rotatably secured to the bottom end of a respective segment arm, and a drive motor including a stator and a rotor secured to the top end of the torque tube that includes a plurality of permanent magnets embedded therein, wherein the stator defines a central bore in which the rotor is disposed, and a latch coil assembly including a latch coil, wherein the latch coil assembly defines a central bore in which the top ends of the segment arms are disposed radially-inwardly of the latch coil.

Abstract: CERMET fuel element includes a fuel meat of consolidated ceramic fuel particles (preferably refractory-metal coated HALEU fuel kernels) and an array of axially-oriented coolant flow channels. Formation and lateral positions of coolant flow channels in the fuel meat are controlled during manufacturing by spacer structures that include ceramic fuel particles. In one embodiment, a coating on a sacrificial rod (the rod being subsequently removed) forms the coolant channel and the spacer structures are affixed to the coating; in a second embodiment, a metal tube forms the coolant channel and the spacer structures are affixed to the metal tube. The spacer structures laterally position the coolant channels in spaced-apart relation and are consolidated with the ceramic fuel particles to form CERMET fuel meat of a fuel element, which are subsequently incorporated into fuel assemblies that are distributively arranged in a moderator block within a nuclear fission reactor, in particular for propulsion.

Abstract: Carbide-based fuel assembly includes outer structural member of ceramic matrix composite material (e.g., SiC—SiC composite), insulation layer of porous refractory ceramic material (e.g., zirconium carbide with open-cell foam structure or fibrous zirconium carbide), and interior structural member of refractory ceramic-graphite composite material (e.g., zirconium carbide-graphite or niobium carbide-graphite). Spacer structures between various layers provide a defined and controlled spacing relationship. A fuel element bundle positioned between support meshes includes a plurality of distributively arranged fuel elements or a solid, unitary fuel element with coolant channels, each having a fuel composition including high assay, low enriched uranium (HALEU).

Abstract: Carbide-based fuel assembly includes outer structural member of ceramic matrix composite material, the interior surface of which is lined in higher temperature regions with an insulation layer of porous refractory ceramic material. A continuous insulation layer extends the length of the fuel assembly or separate insulation layer sections have a thickness increasing step-wise along the length of the fuel assembly from upper (inlet) section towards bottom (outlet) section. A fuel element positioned inward of the insulation layer and between support meshes has a fuel composition including HALEU and has the form of a plurality of individual elongated fuel bodies or one or more fuel monolith bodies containing coolant flow channels. Fuel assemblies are distributively arranged in a moderator block, with upper end of the outer structural member attached to an inlet for propellant and lower end of the outer structural member operatively interfaced with a nozzle forming a NTP reactor.

Abstract: Plurality of layers form a nuclear fission reactor structure, each layer having an inner segment body, an intermediate segment body, and an outer segment body (each segment body separated by an interface). The layers include a plurality of cladding arms having involute curve shapes that spirally radiate outward from a radially inner end to a radially outer end. Chambers in the involute curve shaped cladding arm contain fuel compositions (and/or other materials such as moderators and poisons). The design of the involute curve shaped cladding arms and the composition of the materials conform to neutronic and thermal management requirements for the nuclear fission reactor and are of sufficiently common design and/or have sufficiently few variations as to reduce manufacturing complexity and manufacturing variability.

Abstract: Reactor core and thermal neutron fission reactor has fuel rods with a composite fuel composition (each having the same uniform cross-section along their axial length), end plates at first and second ends, and intermediate support plates located along a longitudinal length of the reactor core. In a radial cross-section, the fuel rods are arranged at nodes of a hexagonal pitch arrangement, in which the nodes are in a spaced-apart arrangement and interconnected by ligaments. Openings between the nodes form part of a coolant flow path through the thermal neutron reactor core. At least two of the nodes of the hexagonal pitch arrangement are sized to allow insertion, translation, removal, or a combination thereof of auxiliary equipment, such as a target delivery system (TDS) for isotopes. Thermal neutron flux (neutrons 0.06 eV) is maximized for maximum neutron activation potential, which is applied to produce both commercial and research isotopes.

Abstract: A method inspects weld quality in-situ. The method obtains a plurality of sequenced images of an in-progress welding process and generates a multi-dimensional data input based on the plurality of sequenced images and/or one or more weld process control parameters. The parameters may include: (i) shield gas flow rate, temperature, and pressure; (ii) voltage, amperage, wire feed rate and temperature (if applicable); (iii) part preheat/inter-pass temperature; and (iv) part and weld torch relative velocity). The method generates defect probability and analytics information by applying one or more computer vision techniques on the multi-dimensional data input. The analytics information includes predictive insights on quality features of the in-progress welding process. The method then generates a 3-D visualization of one or more as-welded regions, based on the analytics information, and the plurality of sequenced images.

Abstract: Nuclear propulsion fission reactor structure has an active core region including fuel element structures, a reflector with rotatable neutron absorber structures (such as drum absorbers), and a core former conformal mating the outer surface of the fuel element structures to the reflector. Fuel element structures are arranged abutting nearest neighbor fuel element structures in a tri-pitch design. Cladding bodies defining coolant channels are inserted into and joined to upper and lower core plates to from a continuous structure that is a first portion of the containment structure. The nuclear propulsion fission reactor structure can be incorporated into a nuclear thermal propulsion engine for propulsion applications, such as space propulsion.

Abstract: A method is used to design nuclear reactors using design variables and metric variables. A user specifies ranges for the design variables and target values for the metric variables. A set of design parameter samples are selected. For each sample, the method runs three processes, which compute metric variables to thermal-hydraulics, neutronics, and stress. The method applies a cost function to each sample to compute an aggregate residual of the metric variables compared to the target values. The method trains a machine learning model using the samples and the computed aggregate residuals. The method shrinks the range for each design variable according to correlation between the respective design variable and estimated residuals using the machine learning model. These steps are repeated until a sample having a smallest residual is unchanged for multiple iterations. The method then uses the final machine learning model to assess relative importance of each design variable.

Abstract: Plurality of layers form a nuclear fission reactor structure, each layer having an inner segment body, an intermediate segment body, and an outer segment body (each segment body separated by an interface). The layers include a plurality of cladding arms having involute curve shapes that spirally radiate outward from a radially inner end to a radially outer end. Chambers in the involute curve shaped cladding arm contain fuel compositions (and/or other materials such as moderators and poisons). The design of the involute curve shaped cladding arms and the composition of the materials conform to neutronic and thermal management requirements for the nuclear fission reactor and are of sufficiently common design and/or have sufficiently few variations as to reduce manufacturing complexity and manufacturing variability.

Abstract: Methods to in-situ monitor production of additive manufacturing products collects images from the deposition process on a layer-by-layer basis, including a void image of the pattern left in a slurry layer after deposition of a layer and a displacement image formed by immersing the just-deposited layer in a renewed slurry layer. Image properties of the void image and displacement image are corrected and then compared to a binary expected image from a computer generated model to identify defects in the just-deposited layer on a layer-by-layer basis. Additional methods use the output from the comparison to form a 3D model corresponding to at least a portion of the additive manufacturing product. Components to control the additive manufacturing operation based on digital model data and to in-situ monitor successive layers for manufacturing defects can be embodied in a computer system or computer-aided machine, such as a computer controlled additive manufacturing machine.