The present disclosure relates to a method for monitoring failure of coated particles in fuel elements in a core of a pebble-bed high-temperature gas-cooled reactor, which is related to the technical field of nuclear reactor engineering and includes the following steps: S11, calculating an inventory of a short-lived noble gas fission nuclide; S12, obtaining a ratio of a release rate to a birth rate of the short-lived noble gas fission nuclide based on a temperature of the fuel elements using a Booth diffusion and release model; S13, deriving a theoretical expression for an activity concentration of the short-lived noble gas fission nuclide in a primary circuit using a migration model of the nuclide in the primary circuit; S14, obtaining an experimental measurement value of the activity concentration of the short-lived noble gas fission nuclide in the primary circuit at a sampling moment by gas sampling; S15, optimally calculating a failure fraction of the coated particles in the fuel elements and a share of uranium contamination in the matrix graphite in the core based on the theoretical expression and the experimental measurement value. The present disclosure can provide key parameters for the performance and status of the fuel elements in the core, which are required for radiation safety studies, source term calculations and accident analysis of the pebble-bed high-temperature gas-cooled reactor.

A system for transferring heat from a nuclear reactor comprises a nuclear reactor comprising a nuclear fuel and a reactor vessel surrounding the nuclear reactor and a heat transfer system surrounding the nuclear reactor. The heat transfer system comprises an inner wall surrounding the nuclear reactor vessel, first fins coupled to an outer surface of inner wall, an outer wall between the inner wall and a surrounding environment, and second fins coupled to an inner surface of the outer wall and extending in a volume between the outer surface of the inner wall and the inner surface of the outer wall, the outer surface of the inner wall and the first fins configured to transfer heat from the nuclear reactor core to the second fins and the inner surface of the outer wall by thermal radiation. The heat transfer system may be directly coupled to the nuclear reactor vessel, or may be coupled to an external reflector surrounding the nuclear reactor vessel. Related heat transfer systems and systems for selectively removing heat from a nuclear reactor are disclosed.

The present application relates to a spherical object falling buffer device including a flow-limiting pipe assembly and a central column assembly; wherein the flow-limiting pipe assembly includes a flow-limiting pipe, a redirecting joint and a sphere outlet pipe; a diameter of the flow-limiting pipe is greater than that of the sphere outlet pipe, and an inner surface of the redirecting joint is a conical surface; the central column assembly includes at least a central column arranged in the flow-limiting pipe; a flow-guiding region is provided between the flow-limiting pipe and the central column, and a plurality of gravity flow guide grooves are provided on an outer peripheral surface of the central column. The spherical object falling buffer device may restrict, guide and buffer spherical objects during falling, and avoids collision damage of the spherical objects or the stock bin due to the excessive falling speed of the spherical objects.

The present disclosure relates to the field of reactor engineering technologies, and particularly to a spherical element detecting and positioning device. The spherical element detecting and positioning device includes a pressure-bearing casing, an internal member and an execution part; the pressure-bearing casing includes a tank body, one sphere inlet adapter pipe and two sphere outlet adapter pipe respectively arranged on the tank body; the internal member is arranged in the rotor counter-bored hole and includes a lining ring and a limit ring; and the execution part includes a turntable and two support lugs. The spherical element detecting and positioning device provided by the present disclosure can achieve triple functions of performing automatic material separation, precise positioning and directional conveyance of spherical elements, has compact structure and simple control, and can meet the operation reliability and maintainability requirements for long-term and intermittent operation under the strong radioactive environment.

Nuclear fuel elements may include: a fuel zone including fuel particles disposed in parallel layers in a matrix including graphite powder; and a shell comprising graphite and surrounding the fuel zone. The fuel particles may include fissile particles, burnable poison particles, breeder particles, or a combination thereof. The fuel zone may include a central region and a peripheral region surrounding the central region, and a fuel particle density of the peripheral region may be greater than a fuel particle density of the central region.

A nuclear fuel element is provided. The nuclear fuel element includes a porous support. The porous support includes a ligament and defines a pore adjacent to the ligament. The ligament has an interior surface spaced from the pore. The interior surface defines a void. The porous support includes silicon carbide. The nuclear fuel element includes a nuclear fuel material disposed in the pore. The nuclear fuel material includes a moderator and tri-structural isotropic (TRISO) particles. Another nuclear fuel element is provided. The nuclear fuel element includes a porous support. The porous support includes a ligament and defines a pore adjacent to the ligament. The ligament has an interior surface spaced from the pore. The interior surface defines a void. The ligament includes the nuclear fuel material. The nuclear fuel element includes a facesheet overlying the porous support and defines a hole. The hole is in fluid communication with the void. The nuclear fuel material includes a nuclear fuel.

The present disclosure provides a sample holder assembly for a laser flash apparatus for measuring a thermal conductivity of a pebble-bed, the assembly comprising: a tubular sample container configured to be mounted on a sample carrier tube for the laser flash apparatus, wherein the sample container has open top and bottom; a bottom disc disposed in the sample container to block the open bottom of the sample container and configured for delivering a laser from a laser flash unit of the apparatus to a pebble-bed; the pebble-bed packed on the bottom disc to a predetermined thickness; and a top disc disposed on the pebble-bed and in the sample container to block the open top of the sample container and configured for receiving heat from the pebble-bed to transfer the heat upward.

The present disclosure provides a sample holder assembly for a laser flash apparatus for measuring a thermal conductivity of a pebble-bed, the assembly comprising: a tubular sample container configured to be mounted on a sample carrier tube for the laser flash apparatus, wherein the sample container has open top and bottom; a bottom disc disposed in the sample container to block the open bottom of the sample container and configured for delivering a laser from a laser flash unit of the apparatus to a pebble-bed; the pebble-bed packed on the bottom disc to a predetermined thickness; and a top disc disposed on the pebble-bed and in the sample container to block the open top of the sample container and configured for receiving heat from the pebble-bed to transfer the heat upward.

A method of manufacturing nuclear fuel elements may include: forming a base portion of the fuel element by depositing a powdered matrix material including a mixture of a graphite material and a fibrous material; depositing particles on the base portion in a predetermined pattern to form a first particle layer, by controlling the position of each particle in the first particle layer; depositing the matrix material on the first particle layer to form a first matrix layer; depositing particles on the first matrix layer in a predetermined pattern to form a second particle layer by controlling positions of each particle in the second particle layer; depositing the matrix material on the second particle layer to form a second matrix layer; and forming a cap portion of the fuel pebble by depositing the matrix material. The particles in the first particle layer and the second particle layer include nuclear fuel particles.

A nuclear power plant spent fuel negative pressure unloading system comprises a fuel element transport pipe and a gas transport pipe. The fuel element transport pipe comprises a fuel element output pipe, a fuel element lifting pipe, and a fuel element unloading pipe connected in series. The fuel element unloading pipe is arranged obliquely downward in the direction of fuel element movement. The distal end of the fuel element unloading pipe is connected sequentially to fuel loading apparatus and a transfer apparatus. Two nozzles of the gas transport pipe are connected to set positions on the fuel element output pipe and the fuel element unloading pipe respectively. A gas driving mechanism is connected to the gas transport pipe. An inlet of the gas driving mechanism is arranged at one end in proximity to the fuel element unloading pipe.