Fuel element, a method of manufacturing a fuel element and a device for its implementation

 

Group of inventions relates to nuclear technology, in particular, to the design of fuel elements (cartridges) and the technology of production. TVEL contains a shell filled with nuclear fuel. One seam made contact butt welding with recessed plugs. The diameter of a fuel rod in the zone of the weld after welding is not larger than the original diameter of the shell. Area with a modified structure is as in the shell and the plug. The maximum width of this zone in the blank in the radial direction in any cross-section of a welded joint to half the original diameter of the stub is not more than 1/3. We propose a method of manufacture of a fuel rod. The method includes manufacturing a stub with an outside diameter greater internal and less external diameter of the shell, the fixation of the membrane in the electrical power supply with depth, compression shell with cover and heat welded parts electric current distribution along the section of the shell in the welding zone while simultaneously providing heat removal from the outer surface of the shell and the outer end portion of the stub. The cover is made with a ratio of its diameter to the diameter of the shank is set to 0.95 and 1.1. In the process of fixing and implementation ecopedology on the edges of the weld zone of the welding current. Welding lead with a slew rate of a current of 0.4-5 kA/MS. A device for the manufacture of a fuel rod. This device contains an annular detachable current lead. The latter includes in the formation zone of the welded joint area with a high electric resistance. The device has a resistance value of this site is always greater than the electrical resistance of the section of the shell of a fuel rod in the welding area. The group of inventions can improve the reliability, stability, sealing and to simplify the design. 3 S. and 2 C.p. f-crystals, 3 ill.

The invention relates to nuclear technology, in particular, to the design of fuel elements (Fe) and manufacturing technologies.

Known TVEL at the request of Germany 4222180, IPC G 21 21/00, 23 To 11/02, 1922, contains a tubular shell and welded it with a landing plug in a weld zone which created a region with a modified metal structure.

A disadvantage of the known fuel is not sufficiently high structural strength and corrosion resistance, due to the configuration and size ratio established area with a modified metal structure.

The known method of flash butt resistance welding of pipe stub with an outer diameter greater inner diameter of the shell, but a smaller outer, the fixation of the membrane in the electrical power supply with depth, compression shell with cover and heat welded parts electrical shock while simultaneously providing heat removal from the outer surface of the shell.

The disadvantage of this method is the impossibility of obtaining the field with a modified structure of the metal in the welding zone with the specified value dimensions and configuration, providing increased structural strength and corrosion resistance.

Known apparatus for forming compounds in the manufacture of fuel rods by the method of flash butt welding along.with. The USSR 1508458, the IPC 23 To 11/02, 1987, containing the ring current lead in the insulating housing part which is in contact with pretorias area of the shell, made of a set of metal plates electrically isolated between themselves and the United electrical shunt.

A disadvantage of the known device is that it is not possible to generate in visitors product desired area with the changed structure of the metal.

The closest in technical essence and the achieved result - the prototype is a fuel element according to the patent of the Russian Federation 2082574, the IPC 23 To 11/02, G 21 3/00, 1997, the military structure of the metal on the penetration depth of the plugs, equal to 2-5 wall thickness of the shell, and the thickness from the inner surface of the shell not higher than 0.9wherethe wall thickness of the shell.

The disadvantages of this fuel element is the fact that the diameter of the fuel element in the weld equal to the diameter of the shell. It provides a stable and reliable electrical power supply and fixation of the pipe during welding, butt welded stub can be located against the flow of the coolant in the reactor, which impairs the flow resistance of the fuel element and fuel Assembly as a whole. The coincidence of areas with a modified structure with the value of embedding the beginning of this zone coincides with the junction of the shell in the cap (thick to thin), which increases the level of stress in the most dangerous section closest to the claimed prototype is known the method according to the patent of the Russian Federation 2082574, the IPC 23 To 11/02, G 21 3/00, 1997, including the manufacture of plugs with a maximum diameter, a large internal diameter of the shell 0.2 to 1.4the fixation of the membrane in the electrical power supply with depth, compression shell with cover and heat welded parts, electrical current, pliney 2-5 from its end face, 0.3 0.9 welding current, while providing heat removal from the outer surface of the shell.

The disadvantage of this method is the instability of the quality of a welded joint as it does not take into account the ratio of the diameters of the plugs. The difference in diameters exceeding their attitude more than 1.1, results in the welding process to collapse is the most heated area stub at its maximum diameter and its offset relative to the cold shank with the formation of long folds, reducing the length of the welded connection to an invalid value. In real terms is always also there is some misalignment between the end of the shell and plugs, which further disturbs the uniformity and worsens the conditions for the formation of a welded joint. Also not taken into account the parameters of the pulse of welding current, in particular the speed of its rise, that in certain moments leads to poor welding.

Processing an end face at a right angle or with an external chamfer facilitates contact with the end of the pipe during transportation on the production line contamination, which can lead to the appearance of the weld seam of unacceptable defects.

Closest to the claimed prototype is Solovyinaya elements by the method of flash butt welding, containing ring current supply, part of which is in contact with pretorias area, made of a set of electrically isolated plates connected between an electrical shunt. Each of the plates is made of a thickness of 0.2-2the size of the inlaid part of the electrical power supply along the axis of the hole is made with a length of 2.5-6.

A disadvantage of the known device is that it provides complete isolation plates package. This requirement must be combined with a minimum thickness of the insulation layer to preserve the heat sink conditions and prevent oxidation of the outer surface of the shell. Complete isolation of the plates causes a major role in the current distribution along the length of the shell executes the shunt. Higher current loads in place of the bypass plate pack can cause oxidation in places of passage of current, with the consequent increase of the resistance in this place and, accordingly, the violation of the specified current distribution along the perimeter and the length of the welding area, which affects the quality of welds. Therefore, this design requires reliable direct connection of shunt shunt plates. Abeshi object of the invention is to improve the reliability and stability of the seal, simplify the design of the device.

The solution of the technical problem is achieved by the fact that in the fuel element containing envelope filled with nuclear fuel, at least one seam made contact butt welding with recessed plugs, according to the formula of the invention the diameter of the fuel element in the zone of the weld after welding is not larger than the original diameter of the shell, and the area with the changed structure of the shell and the plug, while the maximum width of this zone in the blank in the radial direction in any cross-section of a welded joint to half the original diameter of the stub is not more than 1/3.

Problem is solved thanks to the fact that the method of manufacturing a fuel element comprising manufacturing a stub with an outer diameter, a large internal, but less than the outer diameter of the shell, the fixation of the membrane in the electrical power supply with depth, compression shell with cover and heat welded parts electric current distribution along the section of the shell in the weld zone, while simultaneously providing heat removal from the outer surface of the shell and the outer end portion of the stub, according to the formula of the invention the cap INIA electrical power supply wedged the end of the shell rebuff on a cone in the elastic range of deformation of the preferential heating of the shell at the edges of the weld zone of the welding current, with a slew rate of 0.4-5 kA/MS, while the faces of the end shell for welding process on the shape close to spherical, the radius equal to 0,15-0,4 its thickness.

This task is achieved by the fact that the device for the manufacture of fuel elements containing ring demountable current lead containing formation zone of a welded joint area with high electrical resistance, according to the formula of the invention has a resistance value of the plot more than the electrical resistance of the area of the fuel cladding by welding area in 4-30 times.

This set of features is new and involves an inventive step, since the reduction of the original diameter of the shell in the area of the weld contributes to the quality of the weld, reducing the level of residual stresses in the area of the inner Burr.

The presence of a zone with a modified structure in the cone promotes uniform heating of the welded parts and improves the quality of their connection.

When the maximum width of this zone in the blank in the radial direction in any cross-section of a welded joint to half the original diameter of the stub within 1/3 dostigaet ysenia this ratio leads to overheating of the stub, deteriorating conditions of formation of the welded joint and the quality of the weld.

The stub execution with respect to its maximum diameter (D) diameter shank diameter (d) is from 0.95 to 1.1 contributes to the reduction of the outer folds, the length of the weld and the density of the metal in the weld zone. With respect to more than 1.1 in the process of welding a shift of the heated metal at a relatively cold shank, which leads to a sharp decrease in the length of the weld.

With respect to less than 0.95, the increase of the volume of the outer Burr prevents movement of the door, and worsens the conditions for the formation of a welded joint, its appearance. Decreased performance welding equipment.

Precipitate the end of the shell on a cone in the process of fixing and implementation of electrical power supply in the elastic range of deformation improves the conditions Toko - and heat transfer in the weld joint area, reduces the likelihood of fires and reduce the corrosion resistance of the welded connection. The slew rate of the welding current is less than 5 kA/MS eliminates the formation bursts in welding and receiving welds with incomplete fusion. When the rate of current rise more than 0.4 kA/MS to 5 kA/MS no overheating of the metal is substantially heating the shell welding current at the edges of the weld zone creates the most favorable conditions for the formation of a welded joint. This is ensured by the device, the value of electrical resistivity which is always greater than the resistance of the shell on the welding area. The increase of this ratio is more than 40 times leads to overheating of the shell, the deterioration of corrosion resistance and welding due to uneven heat and contributes to the formation of inner bursts, resulting in poor penetration and violation of the integrity of the weld. When the value of this ratio less than 3 on the contrary is heated mainly only the end of the shell is marked overheating stub almost "cold" shell along the length of the weld zone. Deteriorating resistance welding equipment.

The proposed technical solutions are illustrated by the drawings.

In Fig.1 shows a fuel element.

In Fig.2 - location and value of the zone with a modified structure in the plug in section of a welded joint.

In Fig.3 - design plugs, ensure the implementation of the proposed method.

The proposed fuel element consists of a shell 1, in which the ends are welded welded seams 2 and 3 stub 4 and 5. At least one of the plugs 4 from the end of the fuel element welded with depth in oblationem (b) is less than the original diameter of the shell (In). The length of the section with a reduced diameter of the fuel element is larger than the length of the welded connection. The minimum diameter (b) is usually to 0.9 from the original diameter of the shell. The shell and the plug have an area with a modified structure 6 and 7, respectively, with the ratio of the width of the zone with a modified structure in the cone (H) to the maximum diameter of the plug (D) in any cross section of the welded connection is less than 1/3 (Fig.2). The length of the zone with a modified structure 7 in the shell does not coincide with the amount of penetration of the stub 4 and the length of the weld 3.

The device 8 for the manufacture of fuel element contains the ring current lead 9. Part of the busbar 10 is a plot of electrical resistance greater than the resistance of a shell in the welding zone from 3 to 40 times. The required resistance value depending on the properties of welded materials and welding modes is achieved by manufacturing the device package partially isolated on the contact surfaces between the metal plates, which may be the same or different thickness (not shown). If necessary, the plate can be optionally bridged on the ends by welding, p is, aunoma 0,15-0,4 its thickness allows, on the one hand, to assemble good uniform contact between the welded parts, and on the other prevents it in the manufacturing process of the fuel element contamination, which increases the stability of welding.

The proposed method for the fabrication of fuel elements is generally implemented in the process of the claimed device as follows.

The end of the shell is pre-treated with the shape close to spherical, the radius equal to 0,15-0,4 its thickness. The shell 1 is fixed in a predetermined position in the device 8, its upsetting the end of the cone in the elastic range of deformation, the end caps 4, with the ratio of the diameter D to the diameter of the shank is set to 0.95 and 1.1, press to the side of the membrane force, providing the necessary quantity and dynamics of movement of the stub when heating parts welding current. For the shell of alloy e-110 with a diameter of about 9 mm and a nominal wall thickness of 0.7, the value of welding current is 10-18 kA, depending on resistance welding equipment and time parameters of the current pulse. Regardless of the duration of the welding current, the optimum value of the speed of its rise on the pulse, within 250-5000 CA2. The value of the changed structure of the shell and the plug depends on resistance welding equipment and welding conditions, provide available welding equipment. Therefore, the specific values of these quantities are determined in each case separately, based on current technological capabilities. Under the action of the welding current and the efforts of the plug is pressed into the shell with mutual strain of metal in the welding zone and is fixed in this position the weld seam.

Claims

1. Fuel element containing envelope filled with nuclear fuel, and at least one seam, made contact butt welding with recessed plugs, characterized in that the diameter in the zone of the weld after welding does not exceed the original diameter of the shell, and the area with the changed structure of the shell and the plug, while the maximum width of this zone in the blank in the radial direction in any cross-section of a welded joint to half the original diameter of the stub is not more than 1/3.

2. The method of manufacture of fuel elements, including the manufacture of the head of the electrical power supply with depth, compression shell with cover and heat welded parts electric current distribution along the section of the shell in the weld zone, while simultaneously providing heat removal from the outer surface of the shell and the outer end portion of the stub, wherein the cover is made with a ratio of its diameter to the diameter of the shank is set to 0.95 and 1.1, in the process of fixing and implementation of electrical power supply wedged the end of the shell rebuff on a cone in the elastic range of deformation of the preferential heating of the shell welding current at the edges of the weld zone, and weld lead with a slew rate of a current of 0.4-5 kA/MS.

3. The method according to p. 2, characterized in that the end faces of the shell for welding process on the shape close to spherical, with a radius equal to 0,15-0,4 its thickness.

4. Device for the manufacture of fuel elements containing ring demountable current lead having in the zone of formation of the welded joint area with high electrical resistance, wherein the resistance value of this site is always greater than the electrical resistance of the area of the fuel cladding by welding area.

5. The device according to p. 4, characterized in that the electric

 

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FIELD: mechanical engineering.

SUBSTANCE: proposed method is intended for manufacturing fuel elements using resistance-butt welding primarily for their joining to zirconium alloy cans. Welding is effected at equipment electrical resistance not over 30-fold resistance of can section forming welded joint having or not point discontinuities in the form of separate spots or chain of such spots forming no continuous line and measuring maximum ten thicknesses of weld in cross-sectional area of welded joint under check disposed at distance equal to two or three thicknesses of can wall from butt-end of plug located inside fuel element, welded joint being checked by uniformity of external fin. Length of poor fin formation section does not exceed 10% of joint perimeter.

EFFECT: enhanced quality of welds and reliability of fuel element sealing.

2 cl

FIELD: mechanical engineering; manufacture of devices for contact butt welding of pipes with plugs for sealing rod-type fuel elements of nuclear reactors.

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EFFECT: reduced labor consumption; enhanced operational stability; extended functional capabilities.

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FIELD: machine engineering, namely methods for contact-butt welding of tube with plug for making fuel elements of nuclear power stations.

SUBSTANCE: method comprises steps of fixing tube at embedding tube end in opening of welding fitting having predetermined value of electric resistance; placing plug having portion welded in tube wall and outer portion in electrode for supplying welding current to outer portion of plug; compressing parts by applying welding effort; heating parts by means of welding electric current and welding them. Outer portion of plug has several parts; its part adjacent to portion welded into tube wall has diameter exceeding diameter of said part but less than diameter of opening of welding fitting. At welding process part of outer portion of plug adjacent to portion welded into tube wall is at least partially introduced into opening of welding fitting for forming annular gap between said part of outer portion and tube end. Said annular gap is filled with outer burrs. Part of outer portion of plug that is not adjacent to portion welded into tube wall has diameter exceeding diameter of opening of welding fitting.

EFFECT: improved characteristics of articles, enhanced versatility of method.

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FIELD: nuclear engineering; fuel elements of nuclear reactors.

SUBSTANCE: proposed fuel element plug has section welded deep into can, its diameter being smaller than outer diameter of can but greater than its inner diameter; it also has end cap. The latter has surface for supplying welding current and applying force. End cap diameter is not smaller than that of fuel element can. Annular drilling is disposed between part to be welded in and surface for supplying welding current. End surface of annular drilling crosses surface of section being welded in. Diameter of annular drilling ranges between diametric dimensions of adjacent sections of plug.

EFFECT: reduced hydraulic resistance to coolant flow in reactor, facilitated manufacture, universal mechanical design.

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