Abstract: The invention concerns an alloy containing equally 0.02 to 0.07% wt. % of the total iron, of chromium or vanadium, 0.8 to 1.3 wt. % of niobium, 100 ppm or less of tin, 1100 to 1700 ppm of oxygen, less than 100 ppm of carbon, 10 to 30 ppm of sulphur and less than 50 ppm of silicon.

Abstract: A process in which isotopes of the same element belonging to the alkaline earth metals, transition elements and heavy metals having an atomic mass of less than 209, in particular lanthanide metals, are separated in an aqueous medium by treating an aqueous medium.

Abstract: The invention proposes a zirconium-based alloy also containing, by weight, apart from unavoidable impurities, from 0.02 to 1% of iron, from 0.8% to 2.3% of niobium, less than 2000 ppm of tin, less than 2000 ppm of oxygen, less than 80 ppm of carbon, from 5 to 35 ppm of sulphur and less than 0.25% in total of chromium and/or vanadium, the ratio R of the niobium content less 0.5% to the iron content, optionally supplemented by the chromium and/or vanadium content, being lower than 3.

Abstract: A method to design a nuclear fuel assembly having the following steps including establishing the falling speed of the control rod upon entry into the lower damping portion when the control cluster falls in the event of a shutdown of the nuclear reactor, establishing, based on the falling speed established in step a), the progression of the falling speed of the control rod in the lower damping portion, establishing, based on the progression of the speed established in step b), a maximum elevated pressure produced in the liquid contained in the lower damping portion, and establishing, based on the maximum elevated pressure established in step c), a maximum circumferential stress produced in the lower damping portion.

Abstract: An annular facing is machined in an inside surface of the spherical wall around the periphery of a zone where the wall has a bore for securing the tube passing therethrough. A first welding material is deposited in the facing, and the bore is made by drilling through a portion of the spherical wall that is surrounded by the facing. The tube is engaged tightly in the bore, and a second welding material is deposited in the facing at the periphery of the tube in order to weld the tube to the first welding material. At least one of the operations of depositing the first and second welding materials in the facing is performed automatically by causing a welding torch to turn around the axis of the bore while moving the torch in a direction that is parallel to the axis of the bore and while causing it to pivot about an axis that is orthogonal to the axis of the bore while rotation is taking place.

Abstract: A method for designing a nuclear fuel assembly, including the steps of establishing a progression of a speed of the control cluster after the impact of the support against the upper end piece, establishing, based on the speed established in step a), a maximum longitudinal load for compression of the spring, and establishing, based on the maximum longitudinal load for compression, at least a maximum shearing stress in the spring.

Abstract: A spacer grid for a fuel assembly in a light-water-cooled nuclear reactor, for providing the transverse retention of a bundle of fuel rods in mutually parallel arrangements, having an array of cells juxtaposed and placed in a regular lattice, each bounded and separated from neighboring cells by at least one peripheral wall which is open at two opposed ends, along the direction of an axis of the cell, so as to receive a fuel rod of cylindrical general shape passing along the cell along its axis parallel to the peripheral wall.

Abstract: A system for delivering tooling around the annulus of a steam generator without damaging any part of the steam generator is provided where the tooling delivery device travels between the tube bundle and the vessel shell and delivers tooling for cleaning, inspection, retrieval and repair. The device has various types of locomotion system including treads, rollers, magnets and vacuum. The cleaning device has multiple high pressure nozzles that rotate 180 degrees about a horizontal axis and 360 degrees about a vertical axis enabling the device to sweep multiple lanes of tubes simultaneously and also clean the front and back of the annulus floor and tube sheet.

Abstract: Marking of the cuts which have to be made, cutting of the section at two ends, removal of the section which has to be replaced, bevelling of the joint ends of the parts remaining after the section has been cut out from the pipe, adjustment of a new or replacement section for length and bevelling of its joining ends and positioning and narrow bevel welding of the ends joining the replacement section to the ends of the remaining parts of the pipe are performed outside the pipe. Within the pipe operations of machining and inspecting an internal part of the joining ends welded together are performed by remote control in a programmed way by introducing and positioning means for working within the pipe from a component of the primary circuit.

Abstract: A control cluster for a pressurized water nuclear reactor comprising a bundle of neutron-absorbing rods each of which comprises a metal tube called cladding which is sealed off by a top end plug at its top end and by a bottom end plug at its bottom end and has a support, or spider, of radiating shape to which the absorber rods are attached through their upper end plugs, characterized in that the cladding of at least some of the absorber rods is weld-free hafnium tubes, the top end plugs of the absorber rods having hafnium cladding being of titanium-based alloy and being welded to the top end part of the hafnium cladding of the absorber rod, the bottom end plugs being of massive hafnium and being welded to the bottom.

Abstract: The invention relates to a method and a device for loading a fuel assembly into the core of a nuclear reactor. The inventive method consists in: inserting a dummy assembly (4) into the loading location (3) of the fuel assembly (5), said dummy assembly essentially having the same shape and dimensions as the loading location (3) and comprising smooth side walls; fixing the position of at least one fuel assembly (5) that is adjacent to the loading location (3), in the presence of the aforementioned dummy assembly (4), in relation to at least one second assembly (5) of the core, using at least one fuel assembly support tool (11); removing the dummy assembly (4) from the loading location (3); introducing the fuel assembly (5) which is being loaded into the loading location (3); and removing the fuel assembly support tool(s) (11).

Abstract: The device comprises a first valve (35a) and a second valve (35b) each comprising a chamber (13a, 13b) communicating via an admission orifice (19a, 19b) with a circuit or a receptacle containing a first or a second fluid, and via an exhaust orifice (18a, 18b) with exhaust means for the first or the second fluid, at least one valve member (20a, 20b) mounted to move within the valve chamber (13a, 13b) between a position for closing and a position for opening the exhaust orifice (18a, 18b), a piston (22a, 24a, 22b, 24b) connected to the valve member (20a, 20b) and resilient return means (32a, 32b) for returning the valve member (20a, 20b) to a closed position. Each of the first and second pistons (22a, 24a, 22b, 24b) has a first face exposed to one of the first and second fluids, and an opposite second face subjected to a force exerted respectively by the second fluid or by the first fluid.

Abstract: The invention relates to a process for treating alkali metals such as sodium charged with tritium or components contaminated with alkali metals such as sodium charged with tritium, in which the alkali metal is reacted with liquid water or water vapor, so as to obtain hydrogen and tritiated hydrogen, characterized in that the hydrogen and the tritiated hydrogen are subjected, in a recombiner (2) to a treatment of catalytic recombination by the addition of oxygen so as to obtain water and tritiated water, and in that the water and the tritiated water are treated so that they are not discharged into the environment. The invention also relates to a plant for carrying out the process.

Abstract: A process in which isotopes of the same element belonging to the alkaline earth metals, transition elements and heavy metals having an atomic mass of less than 209, in particular lanthanide metals, are separated in an aqueous medium by treating an aqueous medium.

Abstract: The invention relates to a process for treating alkali metals such as sodium charged with tritium or components contaminated with alkali metals such as sodium charged with tritium, in which the alkali metal is reacted with liquid water or water vapour, so as to obtain hydrogen and tritiated hydrogen, characterised in that the hydrogen and the tritiated hydrogen are subjected, in a recombiner (2) to a treatment of catalytic recombination by the addition of oxygen so as to obtain water and tritiated water, and in that the water and the tritiated water are treated so that they are not discharged into the environment. The invention also relates to a plant for carrying out the process.

Abstract: The steam generator (1) comprises a first normal feed water device (8) and a second emergency feed water device (16) of the steam generator, comprising, respectively, a first toroidal header (10) and a second toroidal header (17) arranged coaxially with respect to the outer jacket (2b) of the steam generator. The second toroidal header (17) of the second emergency feed water device (16) placed inside the upper cylindrical part (2b) of the outer jacket comprises, fastened to each of a set of openings penetrating an upper part of its toroidal wall, a water injection tube (22) having an open lower end part fastened to the opening of the toroidal wall, a straight part inclined with respect to the vertical axial direction in the direction of a central part of the steam generator and an open upper end at the end of the straight part of the tube (22) for injecting emergency water inside the steam generator.

Abstract: The invention provides a method and tool to perform an analysis of CRUD on a nuclear fuel rod. The method recites providing a nuclear fuel rod with a layer of CRUD on an exterior of the fuel rod, scraping the CRUD from the fuel rod with a CRUD scraping tool and collecting CRUD flakes from the CRUD scraping tool. The method also provides for sorting the CRUD flakes into particle fractions, and analyzing the CRUD with a scanning electron microscope, wherein the scraping tool has a blade with a rigidity that is matched to an anticipated CRUD deposit shear strength.

Abstract: Welding material is deposited automatically in the annular facing. A welding torch is causes to rotate about an axis of rotation that extends in a direction that is radial relative to the spherical wall and that passes through a point of the concave inside surface of the spherical wall in the central portion of the annular facing. Simultaneously with the welding torch being caused to rotate about the axis of rotation, it is displaced in a direction perpendicular to the axis of rotation in controlled manner, and the position of the welding torch in a direction parallel to the of rotation is also controlled so that the electrode of the welding torch describes an elliptical path and ensures that the welding material is deposited in the annular facing in the form of an elliptical bead.

Abstract: A Nuclear Steam Supply Stem (NSSS) Mode 5 Steam Generator Chemical Cleaning system is disclosed which applies chemical cleaning solvent (formulated to remove SG deposits) to the secondary side of the SG using primary side supplied heat during NSS Mode 5 shutdown to maintain the desired application temperature. Mixing is achieved via nitrogen sparging.

Abstract: A fuel assembly for a boiling-water reactor has a water channel and a fuel assembly base, made from a sieve plate and a frame section enclosing the same. The water channel supports a plug with a bore running therethrough, at the lower end thereof, to which the fuel assembly base is fixed. The fuel assembly further comprises an opening through the sieve plate, a skirt, formed on the underside of the plug, surrounding the bore, extending into the opening in the sieve plate, a bush, provided with a first and a second longitudinal section, whereby the first longitudinal section extends from the underside of the sieve plate into the opening in a rotationally-fixed manner and a radial shoulder is provided between the two sections which contacts the underside of the sieve plate. A threaded section of a screw extends through the bush which engages in a thread in the bore in the plug.