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: A nuclear power plant includes a nuclear structure, a frontline support equipment, and a support structure. The nuclear structure includes, and is configured to protect from incurring damage due to a damaging event, at least one of a nuclear reactor or a nuclear fuel storage. The frontline support equipment is configured to perform a fundamental safety function. The support structure is spatially separate from the nuclear structure and includes an initiating support equipment configured to trigger the frontline support equipment to perform the fundamental safety function such that the fundamental safety function is performed independently of the initiating support equipment subsequent to the triggering. The support structure may be a non-protected structure that is not configured to protect the initiating support equipment from incurring damage due to the damaging event.

Abstract: A pressurized water reactor (PWR) includes a vertical cylindrical pressure vessel having a lower portion containing a nuclear reactor core and a vessel head defining an integral pressurizer. A reactor coolant pump (RCP) mounted on the vessel head includes an impeller inside the pressure vessel, a pump motor outside the pressure vessel, and a vertical drive shaft connecting the motor and impeller. The drive shaft does not pass through the integral pressurizer. The drive shaft passes through a vessel penetration of the pressure vessel that is at least large enough for the impeller to pass through.

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: The invention relates to methods for protecting a nuclear reactor core, such as a boiling water reactor core, from fuel and cladding damage due to thermal hydraulic instability in extended operating power flow conditions and, in particular, when an extended power uprate is implemented. The methods employ existing licensed stability methodologies and incorporated minor changes, e.g., to the Average Power Range Monitor (APRM)-based trip system to preclude operation inside the stability vulnerable region of the power/flow map. The APRM-based trip system is modified to set down the APRM flow-biased scram line when core flow is less than a predetermined core flow to prevent the core from entering an unstable region of operation.

Abstract: A steam generator accident mitigation system is disclosed. A steam generator accident mitigation system to mitigate an accident if the accident occurs in a steam generator installed inside a containment building of a nuclear power plant according to an exemplary embodiment of the present system, the system including: a pressurizing tank which is installed inside the containment building and includes a first cooling water and a non-condensable gas for pressurizing the first cooling water therein; at least one connecting pipe connecting the steam generator and the pressurizing tank; and at least one connecting pipe valve which is installed in the at least one connecting pipe, respectively, and is able to control the amount of opening of the connecting pipe; wherein opening of the at least one connecting pipe valve permits fluid communication between the steam generator and the pressurizing tank.

Abstract: A nuclear reactor dismantlement system according to an embodiment includes bio-protective concrete including a first space into which a reactor is inserted and a second space that is connected to the first space and is expanded in the first space, a moving device that is positioned in the second space and moves the reactor, and a cutting device that is positioned in the second space and cuts the reactor.

Abstract: The present disclosure is directed to systems and methods useful for the construction and operation of a Modular Integrated Gas High-Temperature Reactor (MIGHTR). The MIGHTR includes a reactor core assembly disposed at least partially within a core baffle within a first high-pressure shell portion, a thermal transfer assembly disposed at least partially within a flow separation barrel within a second high-pressure shell portion. The longitudinal axes of the first high-pressure shell portion and the second high-pressure shell portion may be collinear. The reactor core assembly may be accessed horizontally for service, maintenance, and refueling. The core baffle may be flexibly displaceably coupled to the flow separation barrel. Coolant gas flows through the reactor core assembly and into the thermal transfer assembly where the temperature of the coolant gas is reduced. A plurality of coolant gas circulators circulate the cooled coolant gas from the thermal transfer assembly to the reactor core assembly.

Abstract: A vessel electrical penetration assembly for a feed-through of nuclear reactor vessel, the assembly including: a docking tube to form an extension of the secondary containment barrier of the reactor, the docking tube including: a first end to be positioned in the interior of the vessel and to be mechanically and sealably connected to an actuator in the interior of the vessel, and a second end to be mechanically and sealably secured to the vessel; a seal-tight electrical bar that passes through the docking tube and having on either side seal-tight connectors ensuring an electrical link between the actuator and the exterior of the reactor; the seal-tight electrical bar including a system for limiting a leakage of primary liquid to the exterior of the vessel if the secondary containment barrier extension fails; and a mechanical maintaining system for securing, under the required pressure conditions, the electrical bar to the vessel.

Abstract: An apparatus for generating neutrons may include: a hollow casing configured to rotate about a central axis, the casing including a wall having a central region substantially at the central axis and a peripheral region, wherein the wall defines a cavity, and wherein the cavity is configured to contain a first coolant fluid; an active layer at least partially on the peripheral region external to the cavity, wherein the active layer is configured to realize a neutron-generating reaction; at least one particle accelerator configured to direct an ion beam on the active layer to activate the neutron-generating reaction; movement means configured to rotate the casing about the central axis and to force the first coolant fluid to contact the wall at the active layer for cooling the casing; and external cooling including a second coolant fluid contacting at least an external portion of the wall.

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 method for generating electricity includes generating electricity at a first reactor with a nuclear fuel element and removing the nuclear fuel element from the first reactor. The method also includes providing the nuclear fuel element at a second reactor and generating electricity at the second reactor with the nuclear fuel element.

Abstract: The method includes configuring a nuclear reactor to at least partially mitigate liquid metal coolant backflow in the nuclear reactor in response to an at least partial failure of a primary electromagnetic pump (EMP) within a reactor pressure vessel of the nuclear reactor, the nuclear reactor being liquid metal-cooled, the primary EMP configured to circulate liquid metal coolant through at least a reactor core of the nuclear reactor, the configuring including, installing a backflow EMP within the reactor pressure vessel, such that when selectively activated, the backflow EMP at least partially mitigates liquid metal coolant backflow through the primary EMP.

Abstract: A power-generation system for a nuclear reactor includes a power unit, a heat exchanger, and a temperature control system. The power unit produces compressed air that is heated by the nuclear reactor via the heat exchanger. The temperature control system includes a heat transfer fluid and a heat exchanger fluidly connected with the compressed air to transfer heat between the compressed air and heat transfer fluid to control the power level of the power unit.

Abstract: A nuclear reactor vessel includes a shell (5) having a wall (9) traversed by at least one passage (11) having a central axis (C) and a valve (21) mounted in the passage (11), the valve (21) having a determined outer cross-section. The passage (11) has an inner end segment (23) that opens into the inner volume (7) and an outer end segment (25) that opens into an outer piping (13), the valve (21) being housed in the inner end segment (23). The valve (21) is capable of being extracted from the passage (11) through the inside of the vessel (1). The outer end segment (25) has at least one portion having an inner cross-section, perpendicular to the central axis (C), that is smaller than the outer cross-section of the valve (21), such that the valve (21) cannot be ejected out of the vessel (1).

Abstract: Embodiments of a laser system having an extremely large number of small pulsed lasers for irradiating small targets in inertial confinement fusion experiments, high energy density physics experiments, and inertial fusion power plants is more flexible than existing laser systems. Embodiments facilitate finer control of critical features of laser pulses for inertial fusion, as well as significant reduction in development costs and expansion of the community involved in the research relative to existing laser systems. Embodiments produce smooth intensity profiles at the target, large bandwidth that is over two orders of magnitude greater than existing laser systems, and fine control over laser wavelengths, focal properties, temporal pulse shape, and illumination geometry. Properties of each of the small pulsed lasers are individually selectable.

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 power module assembly may include a reactor vessel containing a primary coolant and one or more inlets configured to draw a secondary coolant from the containment cooling pool in response to a loss of power and/or a loss of coolant. One or more outlets may be submerged in the containment cooling pool and may be configured to vent the secondary coolant into the containment cooling pool. A heat exchanger may be configured to remove heat from the primary coolant, wherein the heat may be removed by circulating the secondary coolant from the containment cooling pool through the heat exchanger via natural circulation.

Abstract: The power plant system includes a molten salt reactor assembly, a thermocline unit, phase change heat exchangers, and process heat systems. The thermocline unit includes an insulated tank, an initial inlet, a plurality of zone outlets, and a plurality of gradient zones corresponding to each zone outlet and being stacked in the tank. Each gradient zone has a molten salt portion at a portion temperature corresponding to the molten salt supply from the molten salt reactor being stored in the tank and stratified. The molten salt portions at higher portion temperatures generate thermal energy for process heat systems that require higher temperatures, and molten salt portions at lower portion temperatures generate thermal energy for process heat systems that require lower temperatures. The system continuously pumps the molten salt supply in controlled rates to deliver the heat exchange fluid supply to perform work in the corresponding particular process heat system.

Abstract: Nuclear reactors have very few systems for significantly reduced failure possibilities. Nuclear reactors may be boiling water reactors with natural circulation-enabling heights and smaller, flexible energy outputs in the 0-350 megawatt-electric range. Reactors are fully surrounded by an impermeable, high-pressure containment. No coolant pools, heat sinks, active pumps, or other emergency fluid sources may be present inside containment; emergency cooling, like isolation condenser systems, are outside containment. Isolation valves integral with the reactor pressure vessel provide working and emergency fluid through containment to the reactor. Isolation valves are one-piece, welded, or otherwise integral with reactors and fluid conduits having ASME-compliance to eliminate risk of shear failure. Containment may be completely underground and seismically insulated to minimize footprint and above-ground target area.