Abstract: In a system, such as a water-cooled nuclear reactor, water level sensors provide signals to a control channel for control of feedwater flow and hence the water level in the pressure vessel. Rapid and fine level control is provided by comparing fluid outflow and inflow. Means are provided to block automatically the flow comparison signal from the control circuit in response to a signal characteristic of a faulted flow comparison signal. At least one redundant control channel is provided and level control is transferred thereto automatically upon excusion of the water level beyond predetermined normal upper and lower limits or in response to a rapid change in the water level control signal to avoid unnecessary shutdown in the event of a faulted channel.

Abstract: A pulse conversion circuit which converts input voltage pulses to current pulses, compares the resulting current pulses to a threshold current and produces an output voltage proportional to the integrated difference between the current pulses and the threshold current.

Abstract: A storage module or rack is disclosed for storage of nuclear fuel assemblies in a water-filled pool comprising an array of storage tubes arranged in a checkerboard pattern and attached to one another along their corners. Each tube thus forms a storage cell for a fuel assembly and the spaces between each four adjacent tubes form intermediate fuel assembly storage cells. The storage tubes are formed with spaced double walls between which is contained a layer of neutron absorbing material to assure that the array of stored fuel assemblies remains subcritical. Provision is made for free circulation of water through the storage cells to extract heat from the stored assemblies. The storage module maximizes the number of fuel assemblies that can be stored in a given space while minimizing the material used in its construction.

Abstract: A process for treating a particulate uranium oxide composition containing ammonium diuranate precursors such as uranyl fluoride and uranyl nitrate, along with possible impurities, is disclosed. The process comprises the steps of (a) contacting the composition with a sufficient amount of an ammonium hydroxide solution to convert the ammonium diuranate precursors to ammonium diuranate, and (b) heating the composition under a controlled atmosphere at a temperature sufficient to dry the composition, sublime any ammonium fluoride present, and convert the ammonium diuranate to uranium dioxide. In a first modification of the invention, there is practiced the additional step of moving the composition, preferably by mechanically agitating the composition, prior to the heating step, or during the heating step, or both prior to and during the heating step, for a sufficient time to produce rounded agglomerates in the form of a readily flowable powder.

Abstract: Process for recovering compounds of enriched nuclear fuel from scrap materials is disclosed. The process yields an acid solution with the nuclear fuel dissolved therein. Except for spent filter media, the scrap materials are calcined to produce an oxidized material, which is reduced to a particulate material and leached in an acid bath that contains some recycled acid to yield an acid solution of the nuclear fuel material. The scrap materials comprised of spent filter media are mulched and contacted with the acid solution. The insoluble materials are separated from the acid solution, and at least a portion of the acid solution is recycled to the leaching step, while the remainder of the acid solution is collected for subsequent treatment to recover the dissolved nuclear fuel material. Apparatus for performing the foregoing process is also disclosed.

Abstract: The amount of fissile material such as U-235 in each portion of a fuel element, some of which portions may also contain burnable poison such as gadolinium, is determined by detecting the gamma ray emission due to the natural radioactive decay of the fuel material, analyzing the gamma ray signals from each portion to provide a first count of gamma rays primarily due to the U-235 and a second count of gamma rays primarily due to the U-238 daughter products. These first and second counts are corrected for the cladding wall thickness, the density of the fuel material and the burnable poison content in each portion. The first (U-235) count is then corrected by the second (U-238 daughter) count and the thus corrected U-235 count is converted to an indication of the fuel enrichment in each portion. From the enrichment, the burnable poison content, the density of the fuel material and the volumes of each portion, the weight of U-235 in each portion can be determined.

Abstract: An electromagnetic pump for molten metals wherein a rotating magnetic field causes rotation of the molten metal about the axis of the pump structure. A swirl inducer at the inlet end of the pump has inlet passageways radially spaced from the axis of the pump so as to induce rotational flow in the molten metal passing therethrough.A dual-conical shaped inductor supported within and axially aligned with a molten metal passageway forms in combination with said passageway a conically tapered flow path for the molten metal.Angularly oriented flutes are provided in the region of the inductor periphery within the vicinity of the largest diameter portion thereof in order to convert the rotational flow of the molten metal back into axial flow for discharge from the pump.

Abstract: Alloys reacting with water, water vapor and reactive gases at temperatures in the range of about 200.degree. to about 650.degree. C. have the essential components of nickel, titanium and zirconium. The alloys can be made by arc melting zirconium, nickel and titanium and can be formed into sheet or foil by inert-atmosphere hot rolling. The alloys can also be made by plating nickel on a sheet of zirconium-titanium alloy and then conducting a diffusion process by heating the plated alloy in vacuum.

Abstract: A nuclear fuel element for use in the core of a nuclear reactor is disclosed and has an improved composite cladding comprised of a moderate purity metal barrier of zirconium metallurgically bonded on the inside surface of a zirconium alloy tube. The metal barrier forms a shield between the alloy tube and a core of nuclear fuel material enclosed in the composite cladding. There is a gap between the cladding and the core. The metal barrier forms about 1 to about 30 percent of the thickness of the composite cladding and has low neutron absorption characteristics. The metal barrier serves as a preferential reaction site for gaseous impurities and fission products and protects the alloy tube from contact and reaction with such impurities and fission products. Methods of manufacturing the composite cladding are also disclosed.

Abstract: The invention is directed to a supervisory circuit for a control system of the type having a plurality of redundant input channels and a single output channel. More specifically, the invention is directed to a supervisory circuit for a two-channel redundant control system that provides reliability approaching that of a three-channel system. The supervisory circuit operates on the assumption that the majority of control circuit failures are catastrophic. The supervisory circuit includes a channel select circuit that receives the outputs of both of the identical control circuits and determines the faulted channel. Determination of the faulted channel is accomplished by a two-step comparison. In the first step, the outputs of both channels are compared with a previously stored output, or average of previous outputs. In the second step, signals representative of the absolute difference between each channel output and the stored output are compared.

Abstract: A method for monitoring and controlling the operation of a dual platen press used in the manufacture of nuclear fuel pellets is disclosed. The method comprises the steps of indicating the displacements of both platens and imposing the displacements of the platens on orthogonal axes such that the displacements jointly control the motion of a point which traces a lissajous figure representative of the displacement and relative velocity of the press platens. A second lissajous figure representing the desired platen movements and relative velocity may be superimposed on the first lissajous figure, differences between the first and second lissajous figures indicating deviations from the desired operation of the press. Alternately, a press operator may simply use the first lissajous figure constructed from the actual platen displacements to analyze the operation of the press. The completion of preselected portions of the first lissajous figure may be detected and used to trigger subsequent press operations.

Abstract: Remotely manipulatable probe and apparatus for positioning a corrosion thickness sensing transducer over selected areas of the internal surface of a tubular radioactive component submerged in a pool of water for radiation shielding.

Abstract: Apparatus for monitoring and controlling the operation of a dual platen press used in the manufacture of nuclear fuel pellets is disclosed. The apparatus includes means for indicating the displacements of both platens and imposing the displacements of the platens on orthogonal axes such that the displacements jointly control the motion of a point which traces a lissajous figure representative of the displacement and relative velocity of the press platens. A second lissajous figure representing the desired platen movements and relative velocity may be superimposed on the first lissajous figure, differences between the first and second lissajous figures indicating deviations from the desired operation of the press. Alternately, a press operator may simply use the first lissajous figure constructed from the actual platen displacements to analyze the operation of the press. The completion of preselected portions of the first lissajous figure may be detected and used to trigger subsequent press operations.

Abstract: A method of freezing a liquid is disclosed comprising the steps of establishing a freezing zone, delivering the liquid to the freezing zone so that the liquid runs across the freezing zone, and collecting the unfrozen liquid running off the freezing zone for return to the freezing zone. The delivery of liquid is stopped when a sheet of frozen liquid of desired thickness is established on the freezing zone, and the freezing step is continued to harden the sheet of frozen liquid. The freezing zone is heated to harvest the sheet of frozen liquid by thawing the bond between the freezing zone and the sheet initially at the periphery of the freezing zone and thereafter throughout the freezing zone. The harvested sheet of frozen liquid is gravity dropped from the freezing zone into a fragmenting zone where the sheet is broken into fragments.

Abstract: A process for recovering compounds of enriched nuclear fuel from scrap materials is disclosed. The process yields an acid solution with the nuclear fuel dissolved therein. Except for spent filter media, the scrap materials are calcined to produce an oxidized material, which is reduced to a particulate material and leached in an acid bath that contains some recycled acid to yield an acid solution of the nuclear fuel material. The scrap materials comprised of spent filter media are mulched and contacted with the acid solution. The insoluble materials are separated from the acid solution, and at least a portion of the acid solution is recycled to the leaching step, while the remainder of the acid solution is collected for subsequent treatment to recover the dissolved nuclear fuel material. Apparatus for performing the foregoing process is also disclosed.

Abstract: Apparatus for remotely testing radioactive components, for example, the components of a nuclear reactor, by determining and recording the neutron transmission characteristics of the component.

Abstract: An evaporator assembly for a freezing apparatus comprises freezing faces in the form of large planiform surfaces connected to an outer annulus having a contained volume, and the annulus runs along a substantial portion of the periphery of the freezing faces, the freezing faces and the annulus forming a central chamber. One portion of the annulus is attached to a segment having a narrowing cross section forming a contained volume, and a protruding liquid guide is attached to and runs substantially along the length of said segment.

Abstract: A mixture of powders, preferably UO.sub.2 powders, is blended to complete homogeneity in a nuclear-safe, bubbling-bed fluidized bed blender. The blender includes a generally vertically-oriented, slab-shaped, nuclear-safe mixing vessel having a fluidizing grid disposed on the bottom of the vessel. The fluidizing grid comprises a linear array of generally downwardly-directed pyramidal-shaped hoppers each having walls converging into a conically-shaped closable opening. A plurality of gas orifices is provided for directing a flow of fluidizing gas downwardly into the bottom of each of the hoppers and fluidizing gas is supplied to the orifices at a velocity sufficient to cause bubbles of fluidizing gas to rise through and emerge from the mixture of UO.sub.2 powders until a homogeneous blend of solid UO.sub.2 powders is achieved. The apparatus eliminates dead-zones normally present near the bottom of prior art fluidized bed blenders.

Abstract: A mixture of fine and cohesive powders is blended to complete homogeneity in a nuclear-safe bubbling-bed fluidized bed blender having an improved fluidizing grid. The blender includes a generally vertically-oriented slab-shaped, nuclear-safe mixing vessel having a fluidizing grid disposed at one end of the vessel. The fluidizing grid comprises a linear array of generally downwardly-directed, pyramidal-shaped hoppers each having walls converging into a conically-shaped opening. A plurality of ball valves are employed, one such valve being disposed at the bottom of each hopper. The rotary closure member of each of the ball valves includes a first set of gas orifices for directing a flow of fluidizing gas upwardly in a divergent swirl-shaped pattern along the walls of each of the hoppers. In one embodiment a second set of fluidizing gas orifices for directing a flow of fluidizing gas downwardly into the apex of each of the hoppers is also provided.

Abstract: In an arrangement for feeding a fluid at a given temperature into a vessel containing fluid at a different temperature from an inlet pipe through an inlet nozzle to feedfluid distribution means in the vessel, a removable thermal isolator arrangement is provided. Spaced concentric sleeves form a series of fluid spaces which thermally insulate the inner surface of the nozzle from the feedfluid and leakage feedfluid is directed away from the nozzle whereby thermal cycling of the inner surface of the nozzle is minimized to eliminate cracking thereof.