The present invention relates to a top nozzle and a nuclear reactor in which an in-core instrument, which is supposed to be inserted through a top head of a nuclear reactor, is inserted through a guide pin for an upper core plate. In a nuclear reactor including guide pins for aligning a top nozzle for a nuclear fuel assembly with an upper core plate of a nuclear reactor, a guide hole (210) is axially formed through the guide pins (200) and in-core instruments (10) are inserted through the guide holes (210).

An enclosure for non-organic electronic components is provided which includes an inner cavity for housing non-organic electronic components and a neutron shielding barrier surrounding the inner cavity and the electronic components housed within the cavity. The barrier is formed from a neutron reflecting material in solid or powdered form and a neutron absorbing material in solid or powdered form. An optional structural support is provided in certain aspects of the enclosure design.

A fuel ball detecting method and system with a self-diagnosis function are provided. The method includes: exciting a first detecting coil and a second detecting coil of a fuel ball sensor disposed outside a pipeline; obtaining a first voltage signal U.sub.1 from the first detecting coil and a second voltage signal U.sub.2 from the second detecting coil; processing U.sub.1 and U.sub.2 by differential amplification, band pass filtering, phase sensitive detection and low pass filtering by a signal processor to obtain a fuel ball waveform signal U.sub.0; determining whether the fuel ball passes the pipeline according to U.sub.0 by a single chip microcomputer; determining whether the first and the second detecting coils, the signal processor and the single chip microcomputer work normally; outputting a result showing whether the fuel ball passes the pipeline, when the first and the second detecting coils, the signal processor and the single chip microcomputer work normally.

A detection apparatus includes a resonant electrical circuit supported within an interior of a nuclear fuel rod generates a response pulse in response to an excitation pulse and transmits the response pulse through a cladding of the fuel rod to another location within a reactor in which the fuel rod is housed and without any breach in the cladding. A characteristic of the response pulse is indicative of a condition of the fuel rod. The detection apparatus also includes a transmitter positioned outside the cladding, in the reactor, in the vicinity of the fuel rod and configured to generate the excitation pulse and transmit the excitation pulse through the cladding to the resonant electrical circuit. A receiver is supported within the reactor outside of the cladding and, in response to the response pulse, communicates a signal to an electronic processing apparatus outside of the reactor.

A detection apparatus includes a resonant electrical circuit supported within an interior of a nuclear fuel rod generates a response pulse in response to an excitation pulse and transmits the response pulse through a cladding of the fuel rod to another location within a reactor in which the fuel rod is housed and without any breach in the cladding. A characteristic of the response pulse is indicative of a condition of the fuel rod. The detection apparatus also includes a transmitter positioned outside the cladding, in the reactor, in the vicinity of the fuel rod and configured to generate the excitation pulse and transmit the excitation pulse through the cladding to the resonant electrical circuit. A receiver is supported within the reactor outside of the cladding and, in response to the response pulse, communicates a signal to an electronic processing apparatus outside of the reactor.

A self-powered integral in-core instrument thimble assembly for monitoring the temperature and radiation levels surrounding a nuclear fuel assembly, that transmits output signals wirelessly to a remote location. The in-core instrument thimble assembly is activated by a short exposure within a reactor core and remains active after the fuel assembly is removed from the reactor core to continuously provide a remote monitoring capability for the fuel assembly as it is transported or stored at a remote location, without an external power source.

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.

A detection apparatus includes a resonant electrical circuit supported within an interior of a nuclear fuel rod generates a response pulse in response to an excitation pulse and transmits the response pulse through a cladding of the fuel rod to another location within a reactor in which the fuel rod is housed and without any breach in the cladding. A characteristic of the response pulse is indicative of a condition of the fuel rod. The detection apparatus also includes a transmitter positioned outside the cladding, in the reactor, in the vicinity of the fuel rod and configured to generate the excitation pulse and transmit the excitation pulse through the cladding to the resonant electrical circuit. A receiver is supported within the reactor outside of the cladding and, in response to the response pulse, communicates a signal to an electronic processing apparatus outside of the reactor.

A nuclear thermoacoustic device includes a housing defining an interior chamber and a portion of nuclear fuel disposed in the interior chamber. A stack is disposed in the interior chamber and has a hot end and a cold end. The stack is spaced from the portion of nuclear fuel with the hot end directed toward the portion of nuclear fuel. The stack and portion of nuclear fuel are positioned such that an acoustic standing wave is produced in the interior chamber. A frequency of the acoustic standing wave depends on a temperature in the interior chamber.

An apparatus for performing an inspection on the beams of the top guide of a BWR includes a housing, an alignment assembly, and an inspection system. The housing is receivable atop the upper edges of a first pair of beams adjacent a receptacle of the top guide. The reception of the housing atop the upper edges of the first pair of beams is facilitated by the alignment assembly which includes a plurality of legs that are simultaneously moved between a retracted position wherein one or more of the legs is disengaged from the beams within the receptacle and an extended position wherein all of the legs are engaged with the beams of the top guide within the receptacle. The inspection system includes a pair of inspection elements that are translated above a second pair of beams that are adjacent the receptacle and that do not have the housing received thereon.