Abstract: This invention is directed to a fuel assembly for boiling water reactors incorporating an advanced type of "water rod.

Abstract: Vertical and axial movement of fuel rods relative to grid spacers in a fuel bundle of a BWR or PWR nuclear reactor is prevented by use of sleeves welded to various vertical positions upon a fuel rod, whereby the sleeves have horizontally and vertically oriented windows and slots for engaging protrusions and corner springs, respectively, located in the openings for receiving fuel rods of the grid spacers.

Abstract: A mechanism for testing fuel tubes in nuclear fuel bundles includes a carriage, carrying an elongated probe, and a grooved plate. The grooves are parallel to the probe and are spaced by the same distances as rows of tubes in the fuel bundle. They are connected at at least one end. A pin on the carriage fits in the grooves. A hydraulic cylinder reciprocates the carriage longitudinally of the grooves and a pneumatic cylinder urges it laterally, so that the pin moves from groove to groove at the end of each stroke.

Abstract: In accordance with the present invention, use is made of the adjacent vertically arranged fuel bundles which surround the empty core position to be filled with the fuel bundle to be inserted. Such use of the adjacent bundles involves the placement upon the top tie plate of each bundle of a separate and individual centering device, each centering device being of a generally box-like cap configuration and engaging the upper tie plate of each fuel bundle. Preferably, each such centering device includes a pair of tapered dowel pins which engage apertures formed in the upper surface of the fuel assembly tie plate so that lateral forces imposed upon the centering device will be transmitted to the upper end of the fuel bundle assembly that may be bowed into the empty core position.

Abstract: A feeding apparatus for the loading of the spherical nuclear fuel into a fuel rod. The apparatus feeds fuel of three different diameters into a fuel rod so that the three different sized spheres are appropriately packed to achieve sufficient density of fuel to be used in a nuclear reactor.

Abstract: A system and method for the loading of spherical nuclear fuel in vertical fuel rods. The system includes a fuel rod support, a glovebox, a weighing station system, a means for feeding spherical fuel to the fuel rod and transportation means for moving the fuel between parts of the system.

Abstract: An apparatus for continuously providing countercurrent liquid-solid contact. The preferred embodiment of the apparatus includes an Archimedes' screw in the form of a spiral and a distribution system which includes a central tube disposed along the axis of the spiral. The central tube includes a plurality of weirs and is in open communication with the spiral through a plurality of hollow spokes fixed at one end to the spiral and at the other end to the central tube.Dissolving solution is distributed by the distribution system to the spiral where it encounters nuclear material moving upward due to the pumping action of the spiral. The dissolved material moves counter current to the nuclear material and removed near the bottom of the apparatus.

Abstract: A system including a sensor and electronic instrumentation for measuring fission gas pressures inside a pressurized system or device or the like, such as a nuclear fuel rod. The system is based primarily on what is commonly known as the Villari effect which is the dependence of the magnetic permeability of certain magnetic materials upon applied stress, and permits pressure measurements to be made without any mechanical or physical penetration of the fuel cladding or end cap of the fuel rod. In a preferred embodiment pressure sensing is implemented by locating a sensor made from Villari sensitive material inside the pressurized system. The pressure places a stress loading on the sensor which in turn produces electrical output signals proportional to the applied stress.

Abstract: The process for oxidizing irradiated fuel pellets using as the oxidant NO.sub.2 or a mixture of NO.sub.2 with its dissociation products, O.sub.2 and NO, in order to release the Volatile Fission Products (iodine, zenon, krypton and tritium) from the pellets.

Abstract: A locking mechanism for securing an upper tie plate to the tie rods of a nuclear fuel bundle. The mechanism includes an upper tie plate assembly and locking sleeves fixed to the ends of the tie rods. The tie plate is part of the upper tie plate assembly and is secured to the fuel bundle by securing the entire upper tie plate assembly to the locking sleeves fixed to the tie rods. The assembly includes, in addition to the tie plate, locking nuts for engaging the locking sleeves, retaining sleeves to operably connect the locking nuts to the assembly, a spring biased reaction plate to restrain the locking nuts in the locked position and a means to facilitate the removal of the entire assembly as a unit from the fuel bundle.

Abstract: An actinide dioxide, e.g. uranium dioxide, plutonium dioxide, neptunium dioxide, etc., is prepared by reacting the actinide nitrate hexahydrate with sodium dithionite as a first step; the reaction product from this first step is a novel composition of matter comprising the actinide sulfite tetrahydrate. The reaction product resulting from this first step is then converted to the actinide dioxide by heating it in the absence of an oxygen-containing atmosphere (e.g. nitrogen) to a temperature of about 500.degree. to about 950.degree. C. for about 15 to about 135 minutes. If the reaction product resulting from the first step is, prior to carrying out the second heating step, exposed to an oxygen-containing atmosphere such as air, the resultant product is a novel composition of matter comprising the actinide oxysulfite tetrahydrate which can also be readily converted to the actinide dioxide by heating it in the absence of an oxygen-containing atmosphere (e.g. nitrogen) at a temperature of about 400.degree.

Abstract: An invention involving a process and apparatus for isotope-separation applications such as uranium-isotope enrichment is disclosed which employs cascades of gas centrifuges. A preferred apparatus relates to an isotope-enrichment unit which includes a first group of cascades of gas centrifuges and an auxiliary cascade. Each cascade has an input, a light-fraction output, and a heavy-fraction output for separating a gaseous-mixture feed including a compound of a light nuclear isotope and a compound of a heavy nuclear isotope into light and heavy fractions respectively enriched and depleted in the light isotope. The cascades of the first group have at least one enriching stage and at least one stripping stage. An example of such a gaseous mixture is uranium hexafluoride incorporating uranium-235 and uranium-238.

Abstract: This invention relates to a method for the preparation of radioactive wastes in a low leachability form by calcining the radioactive waste on a fluidized bed of glass frit, removing the calcined waste to melter to form a homogeneous melt of the glass and the calcined waste, and then solidifying the melt to encapsulate the radioactive calcine in a glass matrix.

Abstract: An actinide dioxide, e.g. uranium dioxide, is prepared by reacting an actinide nitrate or hydrate or tetrahydrofuranate thereof, e.g. uranyl nitrate, a hydrate of uranyl nitrate or a tetrahydrofuranate of uranyl nitrate with an alkali or alkaline earth metal adduct of a monocyclic or polycyclic hydrocarbon in the presence of an inert organic solvent. Typically, the starting material may be uranyl nitrate dihydrate or uranyl nitrate ditetrahydrofuranate (the latter material is a novel composition of matter) with a reactant such as the sodium adduct of naphthalene in the presence of a solvent such as tetrahydrofuran. The resultant uranium dioxide may be further purified by heating it in the presence of hydrogen.

Abstract: The initial step for conventionally reprocessing spent nuclear fuel is to treat the nuclear fuel rods with concentrated nitric acid at elevated temperatures to dissolve out the contents of the fuel rods. The resultant solution contains ruthenium values present in an oxidation state of at least +4 and the presence of such ruthenium values causes intolerably high corrosion of stainless steel equipment which may come in contact with the hot concentrated nitric acid solution. The corrosion of stainless steel from such ruthenium-containing nitric acid solutions may be inhibited by treating the solutions with a reducing agent comprising nitrogen oxide. It is especially convenient to generate the reducing agent in situ by adding a sugar (e.g. sucrose) to the nitric acid solution so as to reduce substantially all of the dissolved ruthenium values having an oxidation state of at least +4 to an oxidation state of less than +4.

Abstract: A system for capturing a grid spacer in a nuclear fuel bundle which comprises a split sleeve fixed to a capture rod. The sleeve is used in conjunction with a grid spacer having openings formed by intersecting walls which include protrusions and coacting springs extending from the walls. The sleeve includes pairs of longitudinally spaced bosses and a standoff boss extending radially outward from the surface of the rod. The pairs of bosses are positioned astride the protrusions from the walls to prevent longitudinal movement of the grid spacer. The split serves as a guide slot to orient the capture rod so that it may pass through the grid spacer openings unencumbered by the protrusions from the grid space walls. The standoff boss is in surface contact with a wall of the grid spacer.

Abstract: A bimetallic grid spacer comprising a grid structure of zircaloy formed by intersecting striplike members which define fuel element openings for receiving fuel elements and spring strips made of Inconel positioned within the grid structure for cooperating with the fuel elements to maintain them in their desired position. A plurality of these spring strips extend longitudinally between sides of the grid structure, being locked in position by the grid retaining strips. The fuel rods, which are disposed in the fuel openings formed in the grid structure, are positioned by means of the springs associated with the spring strips and a plurality of dimples which extend from the zircaloy grid structure into the openings. In one embodiment the strips are disposed in a plurality of arrays with those spring strip arrays situated in opposing diagonal quadrants of the grid structure extending in the same direction and adjacent spring strip arrays in each half of the spacer extending in relatively perpendicular directions.

Abstract: In a nuclear power reactor fuel bundle having tie rods fastened to a lower tie plate and passing through openings in the upper tie plate, the assembled bundle is secured by locking lugs fixed to rotatable locking sleeves which engage the upper tie plate. Pressure exerted by helical springs mounted around each of the tie rods urge retaining lugs fixed to a retaining sleeve associated with respective tie rods into a position with respect to the locking sleeve to prevent accidental disengagement of the upper plate from the locking lugs. The bundle may be disassembled by depressing the retaining sleeves and rotating the locking lugs to the disengaged position, and then removing the upper tie plate.

Abstract: A hybrid fuel assembly for use in nuclear fuel reactors, such as a large pressurized water reactor, including a fuel assembly having a matrix of fuel rods of different sizes, wherein fuel rods of a first large size are disposed in island arrays which are located within the matrix of fuel rods of the second small size in the vicinity of the control rod guide tubes of the assembly, such that retention of the control rods normally associated with a reactor fuel assembly employing fuel rods only of the first size is possible while still allowing for the maximum linear heat generation rate (LHGR) for the larger first size rods to be reduced to the LHGR normal for the second smaller size fuel rods or lower.

Abstract: Nuclear reactor fuel rod leakage is determined by measurement of vibrational characteristics of a resilient, flexible means sealed within the upper end caps of the fuel elements. The flexible means, which is preferably a metallic diaphragm, is set into motion by the impact of an internal metal rod which is operated by an external magnetic field, thereby permitting an indication of the pressure inside a fuel element without disturbing the welded assembly. The metal rod is activated and the vibration measurements are made through the use of a special tool which fits near the end cap of the fuel element to be tested.