Abstract: A method of collecting 3He from a nuclear reactor may include the steps of a) providing heavy water at least part of which is exposed to a neutron flux of the reactor, b) providing a cover gas in fluid communication with the heavy water, c) operating the nuclear reactor whereby thermal neutron activation of deuterium in the heavy water produces tritium (3H) and at least some of the tritium produces 3He gas by ?? decay and at least a portion of the 3He gas escapes from the heavy water and mixes with the cover gas, d) extracting an outlet gas stream, the outlet gas stream comprising a mixture of the cover gas and the 3He gas and e) separating the 3He gas from the outlet gas stream.

Abstract: A fixture for rectifying one of several different types of repairable and irreparable damage to the upper end portions, or insert sleeves, of the guide thimbles of a fuel assembly held in a work station includes a base having a plurality of tool positioning openings defined therein in a pattern matched with that of the guide thimbles and several aligning holes for mounting the base on guide members of the work station such that the tool positioning openings are disposed in alignment with the guide thimbles. Also, a plurality of different tools are selectively mountable in the openings of the base. Each tool is adapted to operate to rectify a different one of the types of repairable and irreparable damage to the insert sleeves of the guide thimbles.

Abstract: An improved apparatus for applying an end plug to an end of a fuel rod tube includes a housing having spaced inlet and outlet ends adapted to receive the end plug and tube end, respectively, one of three alternative embodiments of a guide arrangement which defines an internal guide channel aligned in tandem with the inlet and outlet ends of the housing along a common axis, and cylindrical ram movable along the axis for engaging and moving the end plug from the inlet end through the guide channel to the outlet end where the plug is applied to the tube end.

Abstract: A method of straightening an irradiated fuel assembly having a plurality of control rod guide thimbles in which some of the guide thimbles are bowed and thus greater in length than other of the guide thimbles comprises the steps of determining the length adjustments required for shortening the respective bowed guide thimbles in order to make their respective lengths generally the same as the other guide thimbles, and then forming expansions in the bowed guide thimbles so as to shorten their respective lengths by the amounts of the length adjustments. Usually, a plurality of expansions are made in most of the bowed guide thimbles at spaced locations between opposite ends thereof. Some of the expansions differ in the amount of shortening from other of the expansions. Also, the total amount of shortening of the bowed guide thimbles is controlled by the number of the expansions and the amount of shortening which results from each expansion.

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: An improved apparatus for applying an end plug to an end of a fuel rod tube includes a housing having spaced inlet and outlet ends adapted to receive the end plug and tube end, respectively, one of three alternative embodiments of a guide arrangement which defines an internal guide channel aligned in tandem with the inlet and outlet ends of the housing along a common axis, and a cylindrical ram movable along the axis for engaging and moving the end plug from the inlet end through the guide channel to the outlet end where the plug is applied to the tube end.

Abstract: Method intended to form a more or less compact bundle of flexible and oblong objects of reduced cross-section dimensions, such as fuel rods of a nuclear reactor, said objects forming, prior to compacting, an assembly wherein they occupy transversally spaced, parallel positions. According to the invention, this method is characterized in that there is arranged, in a generally vertical direction, a plurality of guiding tubes (2) of which the upper ends (2a) are arranged according to the initial disposition of said object assembly, and of which the lower ends (2b) are arranged according to the desired disposition, the dimension of said guiding tubes (2) being such that in each of them one of said objects may slide by means of gravity, and in that said assembly of objects is brought vertically on top of the plurality of guiding tubes, whereafter each object is introduced by its lower end in the upper end of one of said guiding tubes (2), allowing the assembly of said objects to slide downwardly.

Abstract: A fastener locking device for attaching the lower end of a guide thimble to the upper adapter plate of a fuel assembly bottom nozzle includes a connecting fastener and an annular locking sleeve. The fastener has an elongated body portion and an enlarged head portion, and is insertable from the bottom through a passageway of the bottom nozzle. The fastener body portion is externally-threaded for forming a threaded connection with an internally-threaded plug on the lower end of the guide thimble. Also, the fastener head portion has a cross-sectional size larger than that of the fastener body portion and of a small diameter upper passageway portion but smaller than that of a large diameter lower passageway portion for defining an annular gap therebetween and bottoming against an annular ledge which divides the upper and lower passageway portions. The fastener head portion also has a annular outwardly-opening groove defined therein. The annular locking sleeve has opposite upper and lower end segments.

Abstract: In a nuclear fuel assembly having a plurality of separate fuel bundles secured therein in separate compartments, coolant flow paths are provided to enable the flow of coolant between the separate compartments, thereby equalizing the hydraulic pressure between the separate compartments and minimizing the possibility of thermal-hydrodynamic instability between the separate fuel bundles in the nuclear fuel assembly. A plurality of coolant flow paths are formed through solid structural ribs secured to an outer flow channel of the nuclear fuel assembly to permit coolant flow between the separate compartments.

Abstract: Submerged canisters containing compacted spent nuclear fuel rods are connected to buoyant spacer boxes to reduce the apparent weight of the canisters whereby additional canisters may be introduced into existing water pools without exceeding the load-carrying capacity of the water pool floors. The spacer boxes may be integral with the canisters or may be distinct. The spacer boxes may be rigidly or flaccidly connected to the spacer boxes. Buoyancy in the spacer boxes is preferably achieved by filling them with gas, preferably air.

Abstract: A fixture for removing a top nozzle of a reconstitutable fuel assembly held in a fixed position within a work station includes a pair of guide openings in two diagonally opposed corners of its base to movably mount the base on a pair of upstanding guide members of the work station and on the top nozzle in alignment therewith. Also, the fixture includes a pair of hollow expandable split sleeves with wedge pins inserted therein which are operable to lock the fixture to the top nozzle. An arrangement of drive and driven gears connected with a plurality of reaction pins mounted on the base of the fixture are operable to move the fixture base with the top nozzle thereto away from the guide thimbles of the fuel assembly and thereby cause the top nozzle adapter plate to release its connection with the guide thimbles.

Abstract: Device for disposing of elongated core instrumentation probes from nuclear reactors, the device having a guide for the probes to be disposed of, shears for cutting the elongated probes into sections and a shroud for receiving the sections, including a shielded storage container, the guide including a switch for bypassing the shroud, and means for controlling the switch together with the shears for directing relatively long probe sections having a relatively low radiation level into the shroud, and for cutting probe parts having a relatively high radiation level into manifold shorter sections and guiding the manifold shorter sections of the probes having the relatively high radiation level into the storage container.

Abstract: A fixture for inserting and removing locking tubes into and from locking positions in a top nozzle includes a lower traveling plate and an upper traveling plate disposed above the lower plate. The lower plate has hollow flexure tubes attached to and projecting downwardly therefrom. Each flexure tube has an axially segmented sleeve portion which terminates in a lower segmented rim, with the rim being expandable to a first outside diameter greater than an inside diameter of the locking tube and collapsible to a second outside diameter less than the inside diameter of the locking tube. The upper plate has actuating rods attached to and projecting downwardly therefrom through the flexure tubes.

Abstract: The invention relates to an apparatus for handling nuclear fuel assemblies, as well as to an assembly for use with such an apparatus.The apparatus comprises a vertically axed guide tube in which is displaced a grapnel, suspended on a flexible connection such as a chain, under the action of a reduction gear. As the grapnel is immobilized in rotation in the guide tube, an assembly is gripped by means of a bayonet system by controlling the rotation of the guide tube-grapnel assembly by a reduction gear. The apparatus can in particular be suspended on the small and/or large rotary plug of a fast neutron nuclear reactor. It can also be used in a handling hod under gas.

Abstract: A nuclear reactor, particularly a light water reactor or a helium-cooled high-temperature reactor, is provided with a pressure relief system for relieving pressure resulting under fault conditions from coolant in the reactor pressure vessel and/or the protective vessel of the reactor, wherein the coolant is conducted from the vessel or vessels to a pressure relief station downstream thereof. At the pressure relief station the coolant is fed into a liquid reservoir 4 from which the coolant in gaseous or vapor form is fed sequentially through a washing cyclone 13 and a drying cyclone 25. Most of the radioactive fission products carried by the coolant will have been removed by the liquid reservoir 4 and the washing cyclone 13, and the coolant leaving the cyclone 25 may be safely discharged to atmosphere. Both the liquid reservoir 4 and the washing cyclone 13 are provided with cooling circuits 8 to 12 and 14 to 23 respectively for the liquids.

Abstract: A fuel rod support grid includes interleaved straps arranged to form a matrix of hollow cells. Each cell receives one fuel rod and is defined by pairs of opposing elongated walls which are shared with adjacent cells. Each wall of the pairs thereof forming a single cell has one side which is a part of the perimeter of the single cell and has an opposite side which is part of the perimeter of one of several cells disposed about and adjacent to the single cell. The improvements incorporated by the support grid comprise a first set of dimples formed at an upper end of each wall of the pairs thereof defining each cell of the grid and a second set of dimples formed at a lower end of each grid cell wall.

Abstract: A grid structure (42) is mounted within the upper portion (24) of a tapered canister (24), for receiving a relatively loosely packed rectangular array of rods (22) and rearranging the rods into a relatively tightly packed rectangular array at the lower end of the grid. The grid structure comprises a multiplicity of flat, vertically oriented trapezoidal segments (78, 80) interconnected to form a plurality of vertically overlapping grid layers (74, 76). The layers alternate between a row orientation and a column orientation, and thus form a substantially continuous honeycomb of longitudinal cells (64) for guiding individual rods. The cross-sectional area of each cell decreases from the uppermost layer (74a) to the lowermost layer (74i) such that the rods are funneled by the cells to form the tightly packed array.

Abstract: A system for consolidating spent fuel rods from spent fuel assemblies includes an operator and control station, a fuel rod transfer tool with a gripper assembly, indexing devices, and a fuel consolidation station. The fuel rod transfer tool and gripper assembly grips a fuel rod and withdraws it from a fuel bundle until it is clear of the bundle. The tool, with the fuel rod drawn up inside it, is moved to another location where it is desired to place the fuel rod; the tool inserts the rod, and the gripper releases it. The fuel consolidation station has a frame that holds two fuel assemblies and a consolidation container. The bottom of the frame rests on the floor of the fuel pool. The top of the frame supports the indexing devices. An indexing device is provided for each of the fuel assemblies and the consolidation container.

Abstract: Improvements to guide tubes for the fuel assemblies of light water nuclear reactors, said assemblies being immersed in operation in the cooling water of the core of such a reactor, the guide tubes being of the type made from zircaloy and fixed at their two ends respectively to an upper end part and a lower end part made from stainless steel or Irconel and which incorporate devices for braking the fall of the control rods which they house during the rapid shutdown of the reactor, wherein the said braking devices are constituted by means for restricting the diameter of the guide tubes comprising for each guide tube a zircaloy inner sleeve spot welded to the said guide tube and whose internal diameter permits the passage, with a calibrated clearance, of the corresponding control rod, the sleeve being distributed over the lower portion of each guide tube and associated with orifices made in the actual guide tubes to produce the progressive hydraulic absorption of the end of the fall of the control rods.

Abstract: A fast breeder which is formed with a driver core region having an enriched nuclear fuel substance and allowing liquid metal acting as a coolant to pass therethrough and with a blanket region surrounding the periphery of the driver core region. A reactor stopping control rod to be inserted downward into the driver core region has an axially uniform density of boron-10. A reactor power adjusting control to be inserted downward into the driver core region has a lower density of boron-10 in a lower region than that in an upper region.