Abstract: A reactor core having tandem arranged fuel regions for use in a water moderated nuclear reactor. An upper core region is fueled with enriched uranium oxide; while, a lower core region is fueled with a plutonium oxide. An intermediate core region contains natural uranium oxide.

Abstract: A modular in-core flow filter for capturing potentially harmful debris during cold hydrostatic and hot functional testing of a nuclear reactor. Since testing is carried out before fuel assemblies are placed in the reactor, multiple filters, each being of the same size and configuration, are temporarily installed on the reactor lower core plate. They fill the space which later is occupied by fuel assemblies when the assemblies are installed in an operating position. Each filter includes a square metal base having a single axial opening which desirably covers four holes in the core plate. Fine mesh and coarse mesh screens are secured in the axial opening and the unit is removably attached to the core plate by brackets which extend through the metal base and engage the underside of the core plate but are actuated into position from the upper side of the core plate. When functional flow testing of the primary coolant system has been completed, the filters are removed for subsequent use in other reactors.

Abstract: A method and apparatus for preheating filler material to a temperature approaching its melting point prior to deposit within a weld zone. The weld zone and deposited filler material are then heated sufficiently to form an integral weldment. The power imparted to preheat the filler material is automatically, programmably, controlled as a predetermined function of the filler material deposition rate to obtain smooth melting of the filler material within the weld zone at any given filler material feed speed.In an application to welding an extended seam along a workpiece wherein the weld zone is moved along the seam, the power employed to heat the weld zone and the filler material feed speed are additionally controlled as a function of the speed of movement of the weld zone along the seam.

Abstract: An improved nuclear fuel composition characterized as a mixture of the dioxide of uranium and plutonium with pores of specified sizes and volumes of each size. The volume of pores of each size are adjusted so that as each group of pores of each size is removed by the nuclear fission induced process of densification, the volume removed is balanced by the volume added by the nuclear fission induced process of solid state swelling. This fuel composition is dimensionally stable in-pile to high burnups because the rate of pore removal is matched to the rate of swelling.

Abstract: An extremely sensitive metallic vapor detection method primarily for use in a sodium cooled nuclear reactor containment. Sodium vapor, or a compound derived from it, is allowed to react with a radioactively tagged substance so as to produce a radioactive gas. The released gas is monitored by a nuclear counter, which provides a direct indication of the presence of metallic vapor. The method is sensitive to the presence of metallic vapor in a gaseous environment in the range of 10.sup.-16 grams per cubic centimeter.

Abstract: A method for separating isotopes in which a selected isotope is first ionized in a partially bounded region and then driven toward the boundary by space charge electric fields. Radial electric fields, which accelerate movement of the charged particles towards the walls of the boundary, are generated by charge separation associated with ambipolar diffusion of the particles in the plasma column. Selective photoexcitation leads to the preferential ionization of the isotopic component to be separated from the gas mixture. The resulting altered gas mixture component concentrations in the central region and periphery of the bounded area flow from the system through different output channels.

Abstract: A transducer for identifying and quantitatively measuring the presence and location of ferromagnetic material, which is specifically suitable for remotely mapping ferromagnetic deposits on pressurized water reactor steam generator tubing. The transducer employs a first source of a magnetic field which is positionable in magnetic communication with and is mounted to be movable over the surface area of the workpiece. Perturbations produced in the magnetic field as a result of ferromagnetic discontinuities associated with the workpiece are sensed by a Hall element fixedly positioned with respect to the source in magnetic communication with the workpiece. Means are provided for altering the magnetic field of the source in communication with the Hall element to substantially null the output of the Hall element in the absence of magnetic material within or on the workpiece within proximity of the Hall element.

Abstract: A containment vessel for use in mobile nuclear reactor installations. The containment vessel completely surrounds the entire primary system, and is located as close to the reactor primary system components as is possible in order to minimize weight. In addition to being designed to withstand a specified internal pressure, the containment vessel is also designed to maintain integrity as a containment vessel in case of a possible collision accident.

Abstract: An improved thermal power plant and method of power generation which minimizes thermal stress and chemical impurity buildup in the vaporizing component, particularly beneficial under loss of normal feed fluid and startup conditions. The invention is particularly applicable to a liquid metal fast breeder reactor plant.

Abstract: A combined fuel assembly and thimble plug gripper for raising and lowering a fuel assembly into a nuclear reactor core, and for lifting and lowering a thimble plug assembly into the fuel assembly, including a vertically movable mast housing a mechanism which causes pivotally mounted fingers on the bottom of the mast to be moved into and out of latching engagement with the nozzle of a fuel assembly when the mast is resting on said assembly. The mast includes a second mechanism which supports second fingers pivotally mounted thereon and actuable by a third mechanism into and out of engagement with a thimble plug assembly suporting plugs adapted to be inserted in control rod guide thimbles in the fuel assembly. The second mechanism further includes an arrangement for lowering or raising the plug assembly respectively into or out of the guide thimbles in the fuel assembly. The apparatus includes control and interlock systems which preclude operation of the mechanisms under certain prescribed conditions.

Abstract: Apparatus employing ultrasonic energy for detecting and measuring the quantity of gas bubbles present in liquids being transported through pipes. An ultrasonic transducer is positioned along the longitudinal axis of a fluid duct, oriented to transmit acoustic energy radially of the duct around the circumference of the enclosure walls. The back-reflected energy is received centrally of the duct and interpreted as a measure of gas entrainment.One specific embodiment employs a conical reflector to direct the transmitted acoustic energy radially of the duct and redirect the reflected energy back to the transducer for reception. A modified embodiment employs a cylindrical ultrasonic transducer for this purpose.

Abstract: Apparatus is disclosed for handling radioactive fuel assembly during transfer operations. The radioactive fuel assembly is drawn up into a shielding sleeve which substantially reduces the level of radioactivity immediately surrounding the sleeve thereby permitting direct acess by operating personnel. The lifting assembly which draws the fuel assembly up within the shielding sleeve is mounted to and forms an integral part of the handling apparatus. The shielding sleeve accompanies the fuel assembly during all of the transfer operations.

Abstract: A nuclear fuel rod and a device for use within the rod cladding to maintain the axial position of the fuel pellets stacked one atop another within the cladding. The device is initially of a smaller external cross-section than the fuel rod cladding internal cross-section so as to accommodate loading into the rod at preselected locations. During power operation the device responds to a rise in temperature, so as to permanently maintain its position and restrain any axial motion of the fuel pellets.

Abstract: A core cooling system for a nuclear reactor having a plurality of primary fluid flow systems. The reactor coolant flow from the primary systems is joined upon entering the pressure vessel. Jointure is accomplished in a common chamber causing high coolant flow velocities at low static pressures. If a pipe ruptures in one of the primary fluid flow systems, the low pressure in the common chamber minimizes leakage from the intact flow systems. This allows continuation of coolant flow through the nuclear core for a sufficient length of time to effectively eliminate the possibility of thermal damage.

Abstract: The reactor and its containment, instead of being supported on a solid concrete pad, are supported on a truss formed of upper and lower reinforced horizontal plates and vertical walls integrated into a rigid structure. The plates and walls from chambers within which the auxiliary components of the reactor, such as valves, pumping equipment and various tanks, are disposed. Certain of the chambers are also access passages for personnel, pipe chases, valve chambers and the like. In particular the truss includes an annular chamber. This chamber is lined and sealed by a corrosion-resistant liner and contains coolant and serves as a refueling cooling storage tank. This tank is directly below the primary-coolant conductor loops which extend from the reactor above the upper plate. The upper plate includes a sump connected to the tank through which coolant flows into the tank in the event of the occurrence of a loss-of-coolant accident.

Abstract: A horizontal baffle disposed in the annulus defined between the core barrel and the thermal liner of a nuclear reactor thereby physically separating the outlet region of the core from the annular area below the horizontal baffle. The horizontal baffle prevents hot coolant that has passed through the reactor core from thermally damaging apparatus located in the annulus below the horizontal baffle by utilizing the thermally induced bowing of the horizontal baffle to enhance sealing while accommodating lateral motion of the baffle base plate.

Abstract: A system for removing sludge that may be deposited on a tube sheet of a steam generator. Headers are arranged at the elevation of the sludge to be removed establishing a circumferential fluid stream at that elevation. A fluid lance is moved along the line between the headers emitting a fluid jet perpendicular to the line of movement of the fluid lance at an elevation substantially corresponding to the level of sludge deposits. The fluid jet forces the sludge to the periphery of the tube sheet where the sludge is entrained in and carried away by the circumferential fluid stream.

Abstract: A baffle-former arrangement for the reactor vessel internals of a nuclear reactor. The arrangement includes positioning of formers at the same elevations as the fuel assembly grids, and positioning flow holes in the baffle plates directly beneath selected former grid elevations. The arrangement reduces detrimental cross flows, maintains proper core barrel and baffle temperatures, and alleviates the potential of overpressurization within the baffle-former assembly under assumed major accident conditions.

Abstract: A system for conducting a fluid from one component to another component of a nuclear reactor wherein at least one such component is a rotatable closure head plug capable of movement relative to the other component. The conducting system utilizes the annulus located between the components as a connecting passageway for the fluid.

Abstract: An apparatus for sealing the annulus defined between a substantially cylindrical rotatable first riser assembly and plug combination disposed in a substantially cylindrical second riser assembly and plug combination of a nuclear reactor system. The apparatus comprises a flexible metal member having a first side attached to one of the riser components and a second side extending toward the other riser component and an actuating mechanism attached to the flexible metal member while extending to an accessible location. When the actuating mechanism is not activated, the flexible metal member does not contact the other riser component thus allowing the free rotation of the riser assembly and plug combination. When desired, the actuating mechanism causes the second side of the flexible metal member to contact the other riser component thereby sealing the annulus between the components.