Abstract: The disclosure relates to a high temperature gas-cooled reactor core including a plurality of elongate fuel elements arranged in the form of a multi-lobed prism. Each prismatic fuel element includes an elongate prismatic body and a plurality of elongate fuel channels located within the prismatic body, wherein the cross-sectional area of each prismatic fuel element in a plane parallel to the bases of the prismatic fuel element is no more than 800 cm2 and wherein a ratio of the height of the prismatic body to its greatest width is greater than or equal to 3.0.

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: Systems and methods of transferring nuclear fuel from fuel pools having size and/or weight limitations to a storage or transport cask are disclosed. A canister containing spent nuclear fuel is inserted into a transfer cask. A shielding sleeve is then placed around the transfer cask. A lifting device simultaneously lifts the transfer cask and the shielding sleeve over a storage cask and the spent fuel is transferred from the transfer cask to the storage or transport cask.

Abstract: A fuel assembly includes full length fuel rods which contain a plutonium fissile (Puf) but do not contain a burnable poison, full length fuel rods which contain the fissile uranium and the burnable poison, and partial length fuel rods which contain Puf but do not contain the burnable poison in a channel box. The plutonium enrichment is decreased in an order of the full length fuel rods. The concentration of the burnable poison of the full length fuel rod is higher than the concentration of the full length fuel rod. In each side of a rectangular outermost periphery adjacent to the inner surface of the channel box in a horizontal cross-sectional view of the fuel assembly, two partial length fuel rods are adjacently disposed, and the full length fuel rod containing the burnable poison is disposed to be adjacent to each partial length fuel rod.

Abstract: A nuclear fuel assembly is constructed with fuel assembly components that are wire wrapped and positioned in hexagonal rings within a fuel assembly duct. The fuel assembly components positioned in an outermost ring of the fuel assembly are wire wrapped with a pitch that is shorter than fuel assembly components positioned at an interior ring of the fuel assembly. The shorter pitch at the outer ring of the fuel assembly increases pressure drop of a coolant fluid at the edge and corner subchannels and thereby reduces the temperature gradient across the fuel assembly, which provides a higher output temperature of the nuclear reactor without substantially increasing peak temperature of the fuel cladding.

Abstract: A decommissioning method of biological shielding concrete of a nuclear power plant according to an exemplary embodiment includes: decommissioning a neutron detector positioning device installed to biological shielding concrete surrounding a nuclear reactor to form a plurality of penetrated parts in the biological shielding concrete; inserting a part of a cutting device into the plurality of penetrated parts; and decomposing the biological shielding concrete into a plurality of sub-concrete parts by using the cutting device.

Abstract: System for confining and cooling melt from the core of a water-moderated nuclear reactor comprising a melt trap. The melt trap is installed in the reactor vessel bottom and provided with a cooled containment, consisting of outer and inner housings between which there is a sealant, and the filler for the melt dilution placed in the melt trap inner body. The melt trap inner body has a damper consisting of a central mantle, bearing ribs connected with the central mantle, titled plates, placed between the bearing ribs, the stops providing fastening of the damper to the melt trap body.

Abstract: A nuclear reactor includes a vessel having an outer wall and vessel bottom, and an enclosure delimited by a cylindrical inner wall disposed inside the vessel such that the inner wall and outer wall define a circuit with an annular cross-section. A support element is located adjacent the bottom of the enclosure to hold control elements of the core. A flow diffusion element is positioned between the support element and the vessel bottom and has a circular flat surface portion including disc shaped orifices of the same diameter. The space between the flat portion and the vessel bottom forms an unobstructed mixing zone to allow uniform distribution of flow rates of fluid circulated through the enclosure.

Abstract: Disclosed is a method of measuring a number of environmental conditions with a transmitter device, said transmitter device comprising a neutron detector structured to generate electrical current from neutron flux, an oscillator circuit comprising an electrostatic switch electrically connected to said neutron detector, and an antenna electrically connected with said electrostatic switch, wherein said electrostatic switch is moveable based on said neutron detector, wherein said oscillator circuit is structured to pulse said antenna based on said neutron detector, wherein a period between pulses is related to the neutron flux, the method comprising the steps of: generating the electrical current with said neutron detector, storing energy in said oscillator circuit until a trigger voltage of said electrostatic switch is reached, and emitting a signal with said antenna corresponding to a number of characteristic values of said oscillator circuit.

Abstract: A damping area or “dash pot” on the upper ends of control rods absorb energy from dropped control rod assemblies without narrowing the diameter of guide tubes. As a result, coolant can freely flow through the guide tubes reducing boiling water issues. The dampening area reduces a separation distance between an outside surface of the control rod and an inside surface of the guide tubes decelerating the control rods when entering a top end of the guide tubes. In another example, the dampening area may be located on a drive shaft. The dampening area may have a larger diameter than an opening in a drive shaft support member that decelerates the drive shaft when dropped by a drive mechanism.

Abstract: Microsized devices operable to emit neutrons in a selective manner are provided. The devices are configured so that the rate of neutron emission can be varied, either actively or passively. The devices comprise an a-particle emitting material and a neutron producing target material that when aligned and/or positioned a predetermined distance apart emit neutrons. The rate of neutron emission can be slowed or stopped by taking the materials out of alignment and/or attenuating the ?-particles being directed toward the neutron producing target material.

Abstract: A pit gate includes a gate body which is inserted between a pool portion storing water and a canal portion connected to the pool portion and is configured to change a flow state of the water, and a seal portion (6) which is accommodated in a groove-shaped accommodation recess formed in the gate body and seals between the pool portion and the gate body. The seal portion (6) includes a low-rigidity portion (10) which is relatively easily deformed by a load according to a water pressure from the pool portion side, and a high-rigidity portion (11) which is provided on the pool portion side of the low-rigidity portion and is not easily deformed relatively by the load.

Abstract: A method of decommissioning a nuclear facility including a plurality of sandboxes that cover a plurality of upper penetration holes, includes: exposing the plurality of pipes through the plurality of upper penetration holes by removing the plurality of sandboxes; and cutting the plurality of pipes through the plurality of upper penetration holes.

Abstract: Combined cleanup and heat sink systems work with nuclear reactor coolant loops. Combined systems may join hotter and colder sections of the coolant loops in parallel with any steam generator or other extractor and provide optional heat removal between the same. Combined systems also remove impurities or debris from a fluid coolant without significant heat loss from the coolant. A cooler in the combined system may increase in capacity or be augmented in number to move between purifying cooling and major heat removal from the coolant, potentially as an emergency cooler. The cooler may be joined to the hotter and colder sections through valved flow paths depending on desired functionality. Sections of the coolant loops may be fully above the cooler, which may be above the reactor, to drive flow by gravity and enhance isolation of sections of the coolant loop.

Abstract: A nuclear reactor cooled by liquid metal or by molten salts, provided with a heat exchanger, having inlet of the primary fluid in the lower part and circumferential outlet window in the vicinity of the free surface of the primary fluid in the cold collector. The outlet window is located in an intermediate position with respect to the tube bundle partially raised with respect to the free surface in the cold collector and supplied with primary fluid throughout its height by means of an ancillary device for creating an underpressure in the cover gas of the exchanger with respect to the cover gas in the vessel. The raising of the exchanger and the positioning of the outlet window in the vicinity of the free surface of the primary coolant help to minimize the displacement of primary fluid in the event of accidental release of secondary fluid inside the heat exchanger.

Abstract: A reactor pressure vessel includes a reactor pressure vessel body, a nozzle structure connected to the reactor pressure vessel body, a conduit structure connected to the nozzle structure, and a restraint device attached around a portion of the conduit structure. The restraint device includes collar parts that have cross sections corresponding to respective segments of a periphery of the portion of the conduit structure, brackets attached to the nozzle structure, and rods connecting the brackets to the collar parts. The collar parts are connected end-to-end to each other such that a cross section of the collar parts connected to each other corresponds to the periphery of the portion of the conduit structure. The collar parts are pinned to each other. The brackets spaced apart from each other around a periphery of the nozzle structure.

Abstract: A heat dissipation structure includes a housing. The housing has a bottom surface, a liquid inlet channel, a liquid outlet channel and a protruding portion. The liquid inlet channel and the liquid outlet channel are located at two opposite ends of the housing and above the bottom surface. The liquid inlet channel and the liquid outlet channel extend along a first direction. The protruding portion is located between the liquid inlet channel and the liquid outlet channel and above the bottom surface. The protruding portion protrudes towards a direction away from the bottom surface. The protruding portion has a protruding surface facing away from the bottom surface. A distance between the protruding surface and the bottom surface is increased first and then decreased along the first direction.

Abstract: A method of decommissioning a nuclear facility, including: exposing the plurality of upper penetration holes by removing the plurality of sandboxes; enlarging an upper space of the cavity by cutting an upper portion of the biological shield concrete that is disposed between the plurality of upper penetration holes and between the plurality of upper penetration holes and the cavity; and separating the nuclear reactor pressure vessel from the biological shield concrete.

Abstract: The present relates to the integration of the primary functional elements of graphite moderator and reactor vessel and/or primary heat exchangers and/or control rods into an integral molten salt nuclear reactor (IMSR). Once the design life of the IMSR is reached, for example, in the range of 3 to 10 years, it is disconnected, removed and replaced as a unit. The spent IMSR functions as the medium or long term storage of the radioactive graphite and/or heat exchangers and/or control rods and/or fuel salt contained in the vessel of the IMSR. The present also relates to a nuclear reactor that has a buffer salt surrounding the nuclear vessel. During normal operation of the nuclear reactor, the nuclear reactor operates at a temperature that is lower than the melting point of the buffer salt and the buffer salt acts as a thermal insulator.

Abstract: The invention relates to safe operation support systems of nuclear power plants (NPPs) at severe accidents, including methods and systems for cooling and cooling control of the reactors molten core. The invention increases safety of NPP and cooling efficiency of the molten core of a reactor. The invention increases the efficiency of cooling the molten core of a reactor by safely removing the heat load from the molten metal mirror, ensuring the elimination of vapor explosions. The invention changes the principle of cooling the reactor molten core, in that after the molten core destroys the reactor vessel, the conditions for subsequent cooling of the molten metal are determined by the characteristics of the trap casing, but not of the reactor.