Abstract: A system for detecting the presence of explosives contained in an object under observation, including a cavity structure for receiving the object and a radiation source for producing thermal neutrons directed to the object under observation. Gamma rays are produced to represent the presence of explosives and as an example the concentration of nitrogen contained in the object. Inorganic scintillators are located within the cavity structure to detect the gamma rays and produce an output signal representative of the presence and concentration of the nitrogen and/or other elements contained in the object. The inorganic scintillators are formed as a ring around the cavity structure to detect the nitrogen and/or other elements within at least one particular plane passing through the object. The object under observation is moved through the cavity structure to detect the nitrogen in successive planes to build up a three dimensional profile of explosives concentration.

Abstract: This invention relates to a power source for a nuclear fusion reactor for flowing a current to a load coil (e.g., a toroidal coil) provided in the nuclear fusion reactor such as a reversed field pinch apparatus comprising a bias power supply for supplying a current of a first direction to the load coil, and a reversed magnetic field power supply for supplying a current of a second direction reverse to the first direction to the load coil and having a circuit for holding the reverse current for a predetermined period of time, said bias power supply including a series circuit of a capacitor, a unidirectional element having a switching function and an inductor and connected in parallel with the load coil, thereby removing a clover element from the bias power supply.More particularly, according to this invention, when a current is flowed from the reversed magnetic power supply to the load coil, a current from the reversed magnetic power supply to the inductor in the bias power supply is stopped.

Abstract: Both gadolinia nuclear fuel rods and urania fuel rods are non-destructively tested to determine the enrichment concentration of the fuel pellets therein by serially conveying the gadolinia rods and the urania rod along separate test channels through an active scanner where they are irradiated from a common neutron souce, and the neutron-induced gamma ray emissions are counted as a measure of the enrichment concentrations at a multiplicity of points distributed along the rod length. The enrichment counts are corrected for background radiation, variations in fuel density, and, in the case of gadolinia rods, for gadolinia content by passing these rods through a magnetometer.

Abstract: In-core nuclear instrumentation for a fast breeder reactor includes a neutron flux measuring unit disposed in a control rod assembly, whereby it is possible to measure a change in in-core neutron flux reliably and highly accurately without requiring a major modification in core design.

Abstract: A nuclear fuel assembly with a debris filter. The lower end fitting of the fuel assembly has a stamped plate attached thereto that serves as a debris filter immediately upstream of the fuel rods. The stamped plate is provided with a plurality of flow holes in a size and pattern that provides filtration of debris damaging to the fuel rods while maintaining adequate coolant flow through the fuel assembly.

Abstract: Upper internals for a pressurized nuclear reactor include an assembly for collecting the coolant leaving the core and a separating device. The device has guides for the control clusters and their drive shafts, a lower plate formed with passages for the coolant leaving the core and an upper plate formed with holes for passage of the same coolant into the collection assembly or plenum. A peripheral shroud may connect the plates together. Each cluster guide of the flow separation device has an internal casing devoid of openings, having a practically coolant-tight connection with the plates, whereby the control clusters and their drive shafts are protected against the high speed coolant flow from the core to the outlet nozzle.

Abstract: According to the invention, the object (34) is brought to a first inspection station (I to IV) in which the object is irradiated by thermal neutrons, the capture gamma radiation then liable to be emitted by the object and characterizing a chemical element of the substance to be detected is detected, if the intensity of said radiation exceeds a predetermined threshold, the object is brought to a second inspection station (V,VI), in which the object is irradiated by fast neutrons and the prompt gamma radiation then liable to be emitted by the object and characterizing the chemical element is detected, the energy of the fast neutrons being at least equal to that of prompt gamma radiation, in order to confirm or disprove the information obtained in the first station.

Abstract: A natural circulation boiling-water reactor system using free-surface steam separation incorporates a steam separator near the inner wall of its reaction vessel and extending into a downcomer. Steam so collected supplements the main steam flow from the reactor vessel to drive a turbine, which in turn drives a generator. A flow controller opens and closes a valve to adjust the flow of steam from the steam collector to the turbine. The flow controller can be programmed to implement a predetermined power output level or to adjust power output as a function of load or time. When this level is exceeded, as indicated by feedback from the generator, the flow controller valve is constricted. The auxiliary steam flow to the turbine is directly decreased, reducing power output. Concomitantly, less steam is removed from the steam collector, and thus from the downcomer. As a result there is more carryunder steam, which reduces the power generated at the reactor core.

Abstract: A device for damping the fall of a neutron absorbing bar on the upper end piece of a nuclear fuel assembly, typically a PWR, comprises at least one pair of cylinder-piston sets which are located symmetrically with respect to the vertical axis of the fuel assembly. One of the cylinder and piston in each set is carried by a fixed plate secured to the upper end piece. The other of the cylinder and piston is fixed to a movable plate arranged to receive the bar upon fall thereof and to move vertically toward the fixed plate, damping being achieved by the head loss impressed to the fluid forced out of the cylinders.

Abstract: A high temperature nuclear control rod assembly comprises a plurality of substantially cylindrical segments flexibly joined together in succession by ball joints. The segments are made of a high temperature graphite or carbon-carbon composite. The segment includes a hollow cylindrical sleeve which has an opening for receiving neutron-absorbing material in the form of pellets or compacted rings. The sleeve has a threaded sleeve bore and outer threaded surface. A cylindrical support post has a threaded shaft at one end which is threadably engaged with the sleeve bore to rigidly couple the support post to the sleeve. The other end of the post is formed with a ball portion. A hollow cylindrical collar has an inner threaded surface engageable with the outer threaded surface of the sleeve to rigidly couple the collar to the sleeve. the collar also has a socket portion which cooperates with the ball portion to flexibly connect segments together to form a ball and socket-type joint.

Abstract: A plasma focus apparatus has a field distortion element in the interelectrode gap at the breech end displaced from the sleeve of insulating material between the electrodes. As a result the neutron yield of the accelerator (which should be considered as representative of the good performance of a plasma focus device in all applications) is at least 5 times the yield in the absence of the field distortion element. A knife blade is the preferred embodiment of the field distortion element.

Abstract: A nuclear reactor core has a first group of fuel rods containing fissionable material and no burnable absorber, and a second group of fuel rods containing fissionable material and two burnable absorber materials. The groups of fuel rods are arranged in the core for controlling power peaking and moderator temperature coefficient. The number of fuel rods in the first group are greater than the number in the second group. The two burnable absorber materials can be provided as separate coatings or a mixture. One burnable absorber material is an erbium-bearing material such as erbium oxide and the other is a boron-bearing material such as zirconium diboride. Alternatively, the erbium-bearing material can be interspersed or mixed with the fissionable material.

Abstract: A self-actuated nuclear reactor shutdown system includes a control rod, a temperature sensitive electromagnet disposed above the control rod for causing the control rod to latch thereto and unlatch therefrom, and a control rod insertion portion around which a plurality of wrapper tubes each accommodating a fuel assembly are arranged. The present invention is characterized in that the upper part of the wrapper tube or an extension tube connected to the upper end of the wrapper tube is made of a temperature-sensitive magnetic material having a characteristic by which the saturation flux density thereof will be reduced at the time of an extraordinary rise in the temperature of a coolant flowing through the fuel assembly. The temperature sensitive magnetic material constitutes a part of a magnetic circuit of the electromagnet.

Abstract: An apparatus for controlling the flow of coolant through a nuclear fuel assembly, in which a coolant flow restrictor 26 having longitudinal ducts 30 is provided with plug members 48, 49, 50 of different lengths. The plug members 48, 49, 50 are moved longitudinally by the effect of neutron induced growth on an actuating member 60. A connecting member 53 converts the growth of the actuating member 60 into a longitudinal movement of the plug members 48, 49, 50 so that they are progressively withdrawn from the flow restrictor 26 to increase the flow of coolant through the flow restrictor 26.

Abstract: A control element for reactivity control of a fission source provides an atomic density of .sup.3 He in a control volume which is effective to control criticality as the .sup.3 He is spin-polarized. Spin-polarization of the .sup.3 He affects the cross section of the control volume for fission neutrons and hence, the reactivity. An irradiation source is directed within the .sup.3 He for spin-polarizing the .sup.3 He. An alkali-metal vapor may be included with the .sup.3 He where a laser spin-polarizes the alkali-metal atoms which in turn, spin-couple with .sup.3 He to spin-polarize the .sup.3 He atoms.

Abstract: A mechanism for automatically releasing the control bars in a nuclear reactor following an increase of the temperature in the nuclear boiler includes a thermal sensor suitable for producing a mechanical force or a torque as a function of the temperature and such as to operate a mechanical actuator which provides to unlock the device that holds said control bars causing in this way their fall under the force of gravity.

Abstract: A thermally responsive trigger device comprises a closed bellows (14) having a filling of liquid metal and acting on a trigger (19) responsive to the free end of the bellows. The bellows and trigger are located at a temperature measuring location which is the coolant flow outlet (15) from a demountable sub-assembly vehicle (10) having a fuel unit (11) and a triggerable absorber unit (12). The outlet flowing coolant sweeps over the bellows (14) and once the expansion of the bellows exceeds a threshold a pin (26) and cam (28) at the free end of the bellows causes a plate (21) to move to release the absorber unit (12).

Abstract: A fusion power generating device is disclosed having a relatively small and inexpensive core region which may be contained within an energy absorbing blanket region. The fusion power core region contains apparatus of the toroidal type for confining a high density plasma. The fusion power core is removable from the blanket region and may be disposed and/or recycled for subsequent use within the same blanket region. Thermonuclear ignition of the plasma is obtained by feeding neutral fusible gas into the plasma in a controlled manner such that charged particle heating produced by the fusion reaction is utilized to bootstrap the device to a region of high temperatures and high densities wherein charged particle heating is sufficient to overcome radiation and thermal conductivity losses. The high density plasma produces a large radiation and particle flux on the first wall of the plasma core region thereby necessitating replacement of the core from the blanket region from time to time.

Abstract: A method of igniting a deuterium-tritium ICF fuel target to obtain fuel burn in which the fuel target initially includes a hollow spherical shell having a frozen layer of DT material at substantially uniform thickness and cryogenic temperature around the interior surface of the shell. The target is permitted to free-fall through a target chamber having walls heated by successive target ignitions, so that the target is uniformly heated during free-fall to at least partially melt the frozen fuel layer and form a liquid single-phase layer or a mixed liquid/solid bi-phase layer of substantially uniform thickness around the interior shell surface. The falling target is then illuminated from exteriorly of the chamber while the fuel layer is at substantially uniformly single or bi-phase so as to ignite the fuel layer and release energy therefrom.

Abstract: Apparatus for removing the helium ash from a fusion reactor having a D-T plasma comprises a helium trapping site within the reactor plasma confinement device, said trapping site being formed of a trapping material having negligible helium solubility and relatively high hydrogen solubility; and means for depositing said trapping material on said site at a rate sufficient to prevent saturation of helium trapping.