Fuel element power nuclear reactor and method of sealing

 

(57) Abstract:

The invention relates to nuclear engineering, mainly to the design of fuel elements for power reactors and method of sealing. An object of the invention is the reduction of metal fuel element, the improving technology of its manufacture, improving the reliability in long-term operation. This task is solved in that in the fuel element plug in direct contact with the fuel, is connected with the shell welds made of electron-beam welding, and has its seat in the casing throughout the length of the "flats", which forms with the inner surface of the shell technology channel, partially naplavljaemyj in the area of welded joint that connects with a vertical technological channel for subsequent evacuation, located in the plane of the joint and completely naplavlyaemym during welding, the opposite end of the shell remote from the fuel column, connected flash butt welding with cover thus between the inner surface of the shell and welded seam, there is a fold metal. 2 S. and 3 C.p. f-crystals, 21 ill.

The invention otnositel and method of sealing.

Fuel elements (cartridges) of nuclear power reactors and their welded joints for a long time working in difficult operating conditions under the action of radiation, thermo-mechanical and hydraulic loads in the presence of aggressive, relative to the material of the shell and welded seams, chemical elements (hydrogen, iodine, etc. and should, according to the requirements of normative and technical documentation, to provide corrosion and erosion resistance, ability to withstand vibration and shock loading without breaching.

Currently, to improve efficiency and konkurentnosposobnosti nuclear fuel, addressed the issue of increasing the lifetime of the fuel rod up to 4-5 years, with a simultaneous increase of requirements to their reliability and without substantial increase in cost. One of the conditions for enhancing the safety and reliability of nuclear fuel is the use of the elements containing in the composition of the fuel pellets oxide gadolinium (GdO2). The gadolinium oxide has a large capture cross section for neutrons and is used as a burnable absorber. Hit gadolinium in the coolant circuit, in the case of depressurization of the weld, leading to contamination in the touch of the gap between fuel and cladding, down to zero, an increase in output of the fuel gaseous fission products that enhance nutricline pressure and aggressive content in relation to the zirconium products of the fission of fissile materials. The combination of these factors greatly complicates the shell of a fuel rod. In this regard, important to ensure the required service characteristics TVEL get not only the individual design decisions and the choice of certain technological processes and equipment for their implementation, but also the optimal combination of these factors, which could be satisfied as a consumer, from the point of view of reliability and fuel cost, and manufacturer. In this question the leading role of design and technology sealing TVEL, which is the most labour-intensive in their production process. The sealing technology develops, as a rule, of several operations: preparation of the casing, which includes degreasing, mechanical processing ends, to give them the required shape and dimensions, Assembly shell bottom cover (with welding by fusion) and welding.

Known for a large number of fuel rods of the nuclear power reactor shall Bo one method of welding (see French patent N 2135233, 1972, U.S. patent N 3677894, 1968, Japan patent N 5222074, 1952, "the Development, production and operation of fuel cell power reactors", book 2, page 158, M, Energoatomizdat, 1995).

In recent years, an increasing number of fuel rods sealed welds made by the method of flash butt welding in the solid phase without melting the metal. From the point of view of production, the design of these fuel rods quite technologically advanced, however, in connection with various operating conditions of welds located on the lower and upper end of the rods, this solution may not be optimal and requires additional measures to ensure the reliability of their work. So, in order to improve the efficiency of the fuel rods of the type RBMK part of the stub inside the fuel element and in direct contact with the fuel, made in the form of "fungus". For fuel rods with shells of smaller diameter, which, in particular, is of TVEL VVER-1000 reactor, a design team stubs, consisting of several parts (see RF patent N 2045788, Ál. G 21 C 3/10, 1995).

The use of such plugs, due to the high metal consumption, and complexity of the Assembly plugs and fuel in the CYI seams, made of flash butt welding.

The high level of residual after welding stresses made by this welding, which is repeatedly confirmed by experience increases the likelihood of their exposure to corrosion under tension when there is under cover free iodine formed during reactor operation. The length of the working part of the stub directly involved in the formation of the welded joint is chosen equal to four thicknesses of the walls of the shell. With this design plugs stable reception of weld length of more than 2 wall thickness of the shell, and for TVEL VVER she is 0.6-0.7 mm, in production conditions is extremely difficult. Due to the insufficient amount of the deformation in the interface oxide remain on and microparasite, in particular dust particles of uranium dioxide. Attempts to evacuate them by increasing the displacement of the stub lead to the fact that during the welding process, due to the short working part of the stub, the interaction of metal (external flash) with welding equipment. In the snap quickly breaks down, resulting in poor quality welds.

Analysis of the failure of Stevie metal particles, falling in various ways in the primary coolant of the reactor with the membrane of a fuel rod. One of the design solutions that reduce the likelihood of such particles between the fuel cladding is a considerable increase in the length of the lower plug of a fuel rod. The use of such plugs in the fuel rods, sealed by the above method of flash butt welding is impossible in principle, because of the nature of this method of welding. The known method of flash butt welding, in which the shell is sealed with two ends, by welding thereto plugs, the diameter of which is less than the outer diameter of the pipe, but most of its internal diameter. Welding lead in a special ring mandrel (see "Development, production and operation of fuel cell power reactors", book 2, page 218, Energoatomizdat, M., 1995).

The application of this method requires additional design decisions to optimize the weld site in direct contact with the fuel, and additional technological operations - to reduce the residual after welding stresses, such as annealing operation is energy intensive and unproductive. The presence of annealing makes it almost nebo is welded joints are determined not only by welding modes but the geometry of the working part of the stub, and the value of electric resistance of the mandrel, which is clamped one end of the shell. In the known method requirements cover is missing.

The shell is cut at right angles to its longitudinal axis. Because of misalignment between the welded parts (the misalignment of their axes) contact area at the interface is not uniform around the perimeter of the compound that affects the initial heating of the parts and the formation of the welded connection. There is a real possibility of clamping the junction of the pulverized particles of uranium dioxide, which is always present in the welding chamber of the machine. The uranium dioxide in its properties of ceramic dielectric, which, falling into the butt welded joint, leads to the formation of non-metallic inclusions and poor penetration.

The closest to the technical nature of the proposed solution is TVEL VVER-1000 4-seam construction in which the connection stub with a shell made of electron-beam welding (see "Development, production and operation of fuel cell power reactors", book 2, page 210, Energoatomizdat, M., 1995).

The design of the fuel rod is not technology, has increased the Oia 4 welds, each of which takes at least 2 control operations. Design is not suitable for the manufacture on automated production lines or welding machines with continuous loading and unloading of products. Welding the lower plug in contact with the fuel, runs on units of electron-beam welding separate parties for 90-120 pieces. Installation, and the large podgotovitelnaya time consists of the time required for a set of vacuum discharge the cooling of articles, loading and unloading shells two operators, inefficient. Application for this welding seam installations rotary type, it is impossible, because in these settings in a welding camera fits only the end of the shell with welded plug. The other end of the fuel rod is in the air. Thus, the welding chamber, which prior to welding should be ovakwanyama to 105-106mm RT.art., through the shell of a fuel rod communicates with the atmosphere. When welding installations chamber type simultaneously vacuumized a few dozen shells. In connection with one end of the casing stub, the evacuation is carried out through open her butt. A large length of the shell and small vnutrenniy subjected to welding, up to 110-1mm RT.article Due to the difference of pressures in the chamber and under cover of TVEL happen spillage from the weld pool during welding and formation of defects such as pores and the gas channels. Welds form factor of the weld (H/B) is equal to 1-1/3, where H is the height of the seam, B - width of the seam, the recommended prototype are hardening the structure and level of post-welding stress, close to welds made by this welding, which makes them susceptible to iodine stress corrosion cracking.

The closest way to the proposed technical solution is the method of sealing a fuel rod with the use of electron beam welding (see "Development, production and operation of fuel cell power reactors", book 2, pages 211-212, Energoatomizdat, M., 1995), including the preparation of the ends of the shell, its Assembly with the cover and subsequent multi-pass welding in cooling devices for a given program, the heating of the junction of beam power 15-40% of nominal, welding, pressing passages and smooth decay of the beam current to zero. While the welded edges are performed with some disclosure on plugs and shells are various channels for output hasanatan leads to the loss or displacement of the stub when transporting shell and welding and as noted in the prototype requires the additional details puklavec or vydavac, which is not always acceptable due to the restrictions on the requirements of the inadmissibility of mechanical damage to the membranes. The presence of uneven and rough surface, with bumps and hollows, contributes to pollution and deterioration of the quality of welding. To provide constant tension in 15-20 microns recommended by the prototype, is quite difficult because of the variation in tolerances of the inner diameter of the shell and seat plugs. Often this has to go on the selective Assembly for producing difficult and uncomfortable. The presence of dense planting along the entire length of seat plugs, impedes the escape of gases from the weld joint during heating and welding. To reduce the influence of this factor on the welded parts have to perform special channels, which increase the area of the welded surfaces, contribute to the increase of gas emission during welding and, as a consequence, the formation of pores in the weld. When assembling the inner edge of the end face of the sheath slides over the mounting surface of the door, and, like a scraper collects oxide inclusions and microparasite with this surface, concentrating them and shell are going to stop. Thus, the maximum number of microcontaminants, worsening the quality of welding, is clamped between the welded surfaces at a depth equal to the thickness of the shell. Their removal is recommended prior to welding to perform the heating of the edges of the electron beam, the power of which should be 15-40% of nominal. For more efficient use of the heating of the junction has some openings, which is accomplished by cutting the edges of the stub (see "Development, production and operation of fuel cell power reactors", book 2, page 185, Fig.21.1 and, "Energoatomizdat", M, 1995). However, to achieve effective degassing of the joint under such conditions is not possible. Set the prototype of the beam power during warm-up 15-40% from nominal can be both insufficient and excessive. Insufficient warm-up is only a superficial cleaning of the welded parts and edges of the junction adjacent to the welded surfaces that does not affect the quality of welds. Heating of the connection beam with redundant power leads to the fusion of the edges of the parts and deterioration of the conditions of degassing of the junction of the root side of a welded joint, which contributes to the formation of welded joints is not what ontact between the welded parts in the root of the joint. Because of the intense heat in massive detail cannot adequately be treated with a beam of this most complex part of the compounds containing the maximum amount of pollution and the closed volume of air.

Execution after welding pressing passage in the known method is considered only as a means of compensating for the shortfall of the weld metal resulting from the use of the cutting edges of the welded components. Redundant power input in connection with the crimping, increases the volume of the weld pool, including the root part. As a result, melting involving new surface with the clamped microvolumes gases and residues from pollution.

Finally, at the end of the welding process, there are unacceptable defects volume of continuity of the weld metal, spillage, resulting in the occurrence of undercuts, which are located along the line of fusion of the base metal and weld metal. To eliminate these defects during the recession of beam current is not possible due to the reduction of its power and, accordingly, the width of the weld pool.

The aim of the invention is the reduction of metal fuel, increase of technological effectiveness, increase nanosredstvami in contact with the fuel, connected with the shell welds made of electron-beam welding, and has its seat in the casing throughout the length of the "flats", which forms with the inner surface of the shell technology channel, partially naplavljaemyj in the area of welded joint that connects with a vertical technological channel, located in the plane of the joint and completely naplavlyaemym during welding, and the shape factor of the seam, at a depth of penetration not less than 1.4-1.7 wall thickness of the shell is in the range of 0.3-0.25 in.

In the process of preparing the shell tortsujut from two sides, with the formation on the ends of the conical surface with unequal forming, forming large which is directed toward the outer surface of the shell, and a smaller in the direction of its inner surface, the angle of taper greater forming with the vertical plane under electron-beam welding is 14-18oand under the contact welding 10-20oand the sum of the projections forming the vertical plane is equal to the wall thickness of the shell, while the projection of the outer surface is always greater internal and is 3/4-4/5 of the thickness of the wall of the shell.

The end of the shell under electron-beam welding calibrated by sieges is 6-8 wall thickness of the shell, the challenge in increasing until the end of seat clearance.

Vacuum internal volume of the shell is performed by using technological channel formed "flats", performed along the entire length of seat plugs, and the inner surface of the shell, connecting with a vertical technological channel, located in the plane of the joint.

In the process of electron-beam welding preheating the weld joint is carried out until the beginning of the melting of the edges of parts, and an additional pass is made with the repeated penetration of the weld metal in the range of the height of the junction to the difference between the height of the joint and the maximum pore size, while 1/3-2/3 additional passage perform astrosociology beam, then the beam refocusing 1.1 part of its original diameter, or a drop in the current in the gun at the end of the weld cycle is performed with the rotation of the beam in a circular path with a radius equal 0,28-0,33 joint width obtained after the main and additional passes with the speed of the beam 60-80 Hz.

Final sealing of a fuel rod to produce a welded connection made by the flash butt welding having between int the key of the sheath from the end of the stub, with the ratio of the maximum diameter (dmax) for welding to the length of the working part of the stub (L3), herbal 1,8-2,4 before welding control no shunt circuit in the secondary circuit of the welding machine and the position of the end face of the shell in the welding equipment, welding is performed with variable speed precipitation stub having a peak value at the beginning and end of the move. With the increase of the resistance of the snap-in more optimal welding force correspondingly increases, and the energy of the welding current decreases with a decrease in resistance below the optimum welding force is reduced, and the energy of the welding current increase.

The positive effect is provided by the totality of structural and technological factors.

The presence in the fuel design of the weld made by this welding, to reduce the metal content of the product, by reducing the number of plugs, to improve manufacturability of its manufacture. The flow of the material of construction is reduced to 500 kg for one load in the active area.

The decrease in the amount of zirconium in the area reduces the parasitic capture of neutrons and sposors the Dov.

The presence between the shell and the landing place of the stub technological channel connecting with the technological channel, located in the plane of the interface allows you to perform electron beam welding TVEL in continuous production lines and to improve the conditions of vacuum in the internal volume of the fuel rod. Degassing interface significantly improved by melting the sharp edges of the welded parts and disclosure interface for all its depth during the first pass of the electron beam (warm-up). This contributes to the optimization of the geometry of the joint, weld and Assembly conditions of the welded components. Increasing the angle of cutting more than 18oleads to a deficiency of metal in the seam, which is not compensated by the pressing passage. The seams are formed with an invalid failures. When the value of the angle is less than 14oit is difficult to perform the warming-up without education total weld pool, at the seams started amplification, which requires machining. As in the welding zone weight stub significantly more mass shell, heating and welding is advisable to engage with the displacement of the beam on the door. The displacement of the beam on the cover allows to form the seam mainly of dense material shell m is due to residue gas at the end of the welding pass of the gap seats, deleted pressing passage. Thus the value of the current in the gun set of conditions for re-penetration of the weld metal to a depth equal to the thickness of the wall of the shell to the difference between the wall thickness of the shell and the value of the diameter of the maximum pore. This eliminates the involvement in the new seam welded surfaces and pores remaining in the seam during the welding pass, are removed from the weld pool. Evacuation of the pores of the weld pool, as a rule, is accompanied by the splashing of the metal of varying intensity. Some of them lead to the appearance of external defects (undercuts) along the line of fusion of the base metal and weld metal. The removal of these defects is achieved by defocusing the beam 1,1 its original diameter after welding or, more effectively, due to the rotation of the beam on a circular path with a radius equal 0,28-0,33 joint width obtained after the primary and secondary passages, with the frequency of rotation of the beam 60-80 Hz. Increase or decrease defocus outside the specified limits are not appropriate, because in this case the metal is melted only in the Central part of the weld. Weld edges remain with a rough surface, there remains the possibility of formation of podesti beam from the center seam to the edges. In preplasma the ability of the beam at the edges of the weld increases and becomes sufficient to melt the metal on the depth and width of cut, that is actually to eliminate the undercut. During the rotation of the beam with a frequency less than 60 Hz is formed a rough cheshuichatoe seam and increases the diameter of the seam in the middle, exceed the permissible values. The rotation of the beam with a frequency of 80 Hz and below leads to the growth of the weld reinforcement at the edges failure in the middle that is also not permitted. When the radius of rotation of the beam less than 0,28 joint width beam does not fully overlap the seam width. When the radius of rotation exceeding 0.33 joint width the beam power is not sufficient to eliminate undercuts.

All this, ultimately, improves yield, reduces production costs of the fuel elements and reduces their cost. The results of the comparative testing of joints made of electron-beam welding, the recommended prototype and offered at a special test methodology, show a significant difference in sensitivity to the effects of iodine. Higher resistance of welded joints of the proposed design is achieved through the reduction of residual after welding stresses, as the seams form the roar connection with welding leads, in some cases, to the beginning of the process of diffusion bonding. Between the plug and the shell in the zone of thermocline, in the immediate vicinity of the weld, in places of dense contact shell and seat plugs, there's a kind of "spikes", which are partially relieve the welded seam in the presence of axial or radial forces.

From the weld made by this welding, the fuel is at a distance of about 200 mm, which, in principle, preclude the mechanical stresses on the weld site. Therefore, as possible sources of the occurrence of tensile stresses welded top node of a fuel rod can only be viewed residual after welding voltage and voltage caused by the gas pressure under the membrane, which in normal conditions, as a rule, are compensated by the external pressure of the coolant. In this regard, weld, remote from the fuel and have a higher level of welding stresses, works in more favorable conditions. However, it is obvious that reducing the post-weld stress is a positive factor, to abandon all of which is not advisable, especially with the increase of life proteinrna node between the inner surface of the shell and welded educated deformed inner layers of the shell and outer layers of the working part of the stub, there is zaborshchika metal, the length of which is in the range of 0.2-0.6 mm from the shell thickness. The presence of such a gap folds increases efficiency of welded node with variable bending loads.

The increase in the folds of more than 0.6 mm from the shell thickness leads to a decrease of the total length of the weld, the crease becomes tremendously gap, which may serve as an additional hub stresses.

The execution of the stub with the ratio of its maximum diameter (dmax) for welding to the length of the working part of the stub (L3) 1.8 to 2.4 and availability at the end of the pipe tapered surfaces allow guaranteed to obtain defect-free welded joint with the length of the weld along the axis of the fuel rod is equal to 3-4 wall thickness of the shell. This achieves such conditions of plastic deformation of metal at the junction of that of the welded joint are completely removed oxide film, and the distance between the end face of the shell and collet that holds the stub, after welding is approximately the wall thickness of the shell. Due to the high electric coprative causes increased heat and crushing under the action of the welding force. The increase in this ratio leads to an increase of load on the welding equipment, which contributes to its rapid wear and deterioration of the quality of welding. The running end of the shell in the form of a conical surface stabilizes the contact area of the workpiece along the perimeter of the connection and, consequently, heating of the metal in the joint. The decrease in contact area, compared with vertical cuts, increases the initial heating of the contacting surfaces in the joint, which increases the plasticity and fluidity, which is especially important for alloys with increased heat resistance, facilitates the removal of interface contamination. The likelihood of hitting the seam inclusions of uranium dioxide is reduced by 25-30%. Slice the shell at an angle of less than 10oand more than 20oto the vertical plane does not provide tangible results to improve the density of welds.

Surfacing at an angle of more than 20oto the vertical plane leads to the formation of sharp edges from the inner surface of the shell, which is in the process of transportation and equipment of TVEL fuel mechanically damaged, it formed nicks, dents, worsen the conditions of welding and conducive to getting into the junction of foreign materials affecting the key, therefore, the presence of sharp edges or inaccurate centering of the shell when loading fuel complicate equipment TVEL, help getting into the junction of uranium dioxide.

These drawbacks are eliminated by performing chamfer on the inner edge of the end face of the shell. However, its projection on the vertical plane should not be more than 1/4 of the wall thickness of the shell. Otherwise, the welding quality is deteriorating or because of the formation of the section in the joint with no contact welded parts when they are offset relative to each other, or due to fundamental changes in the conditions of deformation of the welded parts, when the end caps in contact with the generatrix of the conical surface of the chamfer on the inner edge of the shell.

The lack of control of shunt circuits before welding is required in connection with the possibility of failure of the insulating spacers separating not electrically connected parts of the welding equipment. Damaged gaskets leads to the formation of parasitic circuits through which the bypass welding current. The current density in the contact of the welded parts is reduced, although its value remains unchanged.

Wrong vystupleniev welded area of the shell, either his underheating. Both are unacceptable, because the quality of welding and properties of welded joints. Therefore, before switching on the welding current is necessary to determine the position of the end face of the shell into the collet holder. Design and manufacturing technology collet clamp complicated enough. Long work clamp in conditions of cyclic thermo-mechanical loads leads to a change in its resistance. The increase in resistance is compensated by the decrease of the welding force and increase energy pulse of welding current, and a decrease in resistance, on the contrary, a decrease in the energy of the welding current and the increase of the welding force. However, in all cases, the speed of movement of the stub should have two maximum. Only the first peak speed indicates the deviation of the welding conditions from optimal due to a change in resistance welding equipment or welding mode. Two peak velocities are integral indicator of the stability and quality of welding.

The invention is illustrated by drawings:

Fig.1 - the design of TVEL VVER-1000;

Fig.2 - cover under ELS;

Fig.3 - cover under KCC;

Fig.4, Fig.5 - training schemes ends is luski in the shell;

Fig.8 is a diagram of the vacuum internal volume of the shell in the welding installations chamber type;

Fig.9 is a diagram of the vacuum internal volume of the shell in the welding installations rotary type;

Fig.10 - weld connection before electron-beam welding;

Fig. 11 - weld connection in the preliminary heating of the welded edges of the parts;

Fig.12 - weld connection after the main welding pass;

Fig. 13 - weld connection once more (pressing) pass;

Fig.14 is welded joint after welding cycle with the rotation of the beam on the decline;

Fig.15 is a sequence diagram of electron-beam welding;

Fig. 16 diagram of the flash butt welding before welding application efforts;

Fig. 17 diagram of flash butt welding when the welding force;

Fig. 18 is a graph of changes in the velocity of the stub when flash butt welding;

Fig. 19 - butt welded joint after heating the welded edges by electron-beam welding;

Fig. 20 - welded seam, made of electron-beam welding to complete the program;

Fig. 21 - weld made by this welding. Theprovides the measures seam 3, made of electron-beam welding, and with the cover 4 (Fig.3) by means of a seam 5, made of flash butt welding. Between the cap 2 and the inner surface of the shell is partially naplavljaemyj when welding technology channel 6 value of 0.2-0.3 mm, formed by the inner surface of the shell and the "flats" 7 on the seat plugs, which connects with a vertical technological channel 8 value of 0.15-0.25 mm, formed by the end face of the shell and the "sample" 9 in the cap (Fig.2) and fully naplavlyaemym in the process of obtaining a welded joint. Directly with the plug connected to the shell of the electron-beam welding, the contact of the fuel column, recruited from tablets 10 uranium dioxide having an inner hole 11 and the chamfer on the outer edge 12. The post is held in a predetermined position by the clamps 13. Between the inner surface of the shell 1 and the deformed during the welding process, the metal layers is the fold 14, the value of which from the end of the stub 4 is 0.2-0.6mm thickness ( () ) the wall of the shell 1. As a result of mutual deformation of the shell 1 and the stub 4 is the inner 15 and outer 16 grata.

The method is as follows.

Sagatova structural features of plants NDT not checked and should be removed. Trim ends is performed by turning. Originally becomes a bevel cut on the entire wall thickness of the shell 1 (Fig.4). The result that the ends are tapered shape with an angle to the vertical plane 14-18ofor electron-beam welding and 10 -20ofor flash butt welding. To simplify technology, under specific conditions, the corners are usually made the same and equal 14-18o. On the edge, facing toward the inner diameter of the shell remains, as a rule, sharp Burr 17, which further prevents the quality of a fuel rod Assembly and welding. Remove Burr is followed by trimming the edges with a guaranteed removing the top of the cone 18 (Fig.5) from the inner surface of the shell 1. For this purpose, the tool handling device is configured or assembled so as a result of its stroke, the magnitude of the cut edges do not exceed 1/4-1/5 of the wall thickness of the shell. At least one end of the shell 1, is designed under ELS, placed in 3-4 radar tool holder 19 (Fig. 6) installed at the center of its polished metal rod 20, the surface finish and hardness which is nice outer perimeter of the shell 1 is not less than 20%. The length of the working portion 22 in contact with the shell is not less than 6-8 wall thickness of the shell. The edges of working parts of the petals are rounded and polished. Compression (calibration) (Fig.6) shell execute in automatic mode. After machining of the shell are flush cleaning solution, the parties 10-30 pieces or separately, and drying. Similar washing and drying take place and plugs. And then assembles the calibrated end of the shell 1 with a cover 2 under ELS. Assembly (Fig.7) is performed in automatic mode on a special installation 23 to accept the stop end of the shell 1 in the end 2, which excludes the loss of the insert from the tube during further operations. The shell 1 is assembled with the cover 2 by a system of conveyors serves on the operation of weighing to determine their weight without fuel. After the automatic weighing and recording the results in the memory of a computer casing with a plug is supplied for the installation of electron-beam welding. In installations ELS chamber type into the chamber 24 (Fig.8) is loaded at the same time, the party shell 1 into dozens of pieces. Then the camera closes and vacuumized to exhaustion 5105-4105mm RT.article roumirues internal volume of each shell. The magnitude of the pressure changes inside the shell from atmospheric to a loading position 25 to 5105-4105mm RT.article on the position of the weld 26. The camera installation is only the end of the shell 1 with a cover 2 with a length of about 200 mm, the Rest of it is in the air. In this regard, the free end of the shell before vacuum closes technological stub. As the technology plugs you can use sealing devices in the form of caps. However, the simplest and most technologically acceptable technological plugs 27 (Fig.9) with a rubber seal 28 to the inner diameter of the shell. The installation of these plugs into the shell and removing is done by automatic devices. Vacuum internal volume of the shell through technological channels 6 and 8 (Fig.9).

The shell 1 with the cover 2 in a vacuum chamber, clamped in the cooling device 29 (Fig.10), includes the rotation of products and e-beam 30 (Fig.11).

In the process of electron-beam welding preheating (Fig.11) is carried out prior to the melting of the edges of parts, welding pass (Fig. 12) is carried out by the current, providing ha is the making of the weld metal in the range of the height of the junction to the difference between the height of the joint and the maximum pore size moreover, the beam shift on the cap on the amount of 0.15 to 0.3 of the height of the joint.

To improve the appearance of the weld and exceptions defects such as undercut, in 1/3-2/3 of the additional passage of the beam automatically refocusing 1.1 part of its original diameter or, more effectively, at the start of the decrease of beam current the beam rotate on a circular path (Fig. 14) with a radius equal 0,28-0,33 joint width obtained after the primary and secondary passages with a frequency of 60-80 Hz. The rotation of the beam is either standard systems of the type SU-229, or systems-based industrial computers. In the diagrams of welding (Fig. 11, Fig.12, Fig.13, Fig.14) shows: 1 shell, 2 cap, the cooling unit 29, 30 electron beam, 31 weld bead obtained after the main passage 32 time 33 weld bead obtained after pressing passage 34 of the suture line obtained by rotating the beam. The welding cycle is shown in Fig. 15. Welding is carried out at an accelerating voltage of 30 kV, welding speed of 0.96 cm/s, the welding current 14-15 mA, the magnitude of the vacuum 5105-4105mm RT.article.

In the welding process is the deposition of pairs of the metal surface of the weld and heat-affected zone of a fuel rod, which results in dalmasca spraying after welding is activated abrasive tool.

After equipment fuel shell 1 with welded stub 2, determine the weight of the fuel column and lock it against longitudinal movement, billet fuel is fed to the position of the flash butt welding. The open end of the shell 1 and the cover 4 are placed in a welding chamber 35 setup (Fig. 16), consisting of 2 sliders 36, 37 are electrically isolated from each other. One of these insulators is the rubber seal 38 sliders. The floaters is welding tools in the form of a collet grippers 39, 40. The grip 40 is clamped by the cap 4, is automatically fed into the chamber at the moment when the sliders are in the dissolved state. In the grip 39 of the slide 36 is clamped end of the shell 1. Grip 39 is a 3 - blade the collet and provided with a device 42 having an electrical resistance of 700-1200 ľohm that exceeds the resistance area of the membrane that is involved in the formation of the welded connection. The width of this part of the shell equal to the width of the device 42 and is 3.0-4.0 mm or 5-6 wall thickness of the shell. After you install the grip 40 of the stub 4 sliders 36 and 37 are brought to a stop, compressing the rubber seal 38. Through the input 43, also isolated from the masses, the welding chamber and the internal volume of the TV is atiem welded parts is determined by the absence of electrical contact between isorevenue from each other by parts of the welding machine, eliminating the shunt current during welding in addition to the welded parts. In the absence of a bypass details are compressed with a specific pressure 18-22 kg/cm2. Existing between the welded parts, the gap 44 is fully selected, and its value is recorded in computer memory and used to control the correctness of the clamping stub 4 in the nip 40 and calculate the end position of the shell 1 in the nip 39. For 0.2-0.5 seconds after application of welding force (PSt.) controlled the absence of shift of the shell in the welding equipment (Fig. 16). During this time, plastic deformation occurs in the sharp edge of the end face of the shell 1 and the stub 4 (Fig.17), is aligned with the contact area between them and in the end, with the help of the sensor 45, is determined by the starting position of the stub before welding, which is later used to calculate the movement of the caps in the welding process. In case of positive result of this control command is sent to switch on the welding current. Under the influence of forces and the welding current is thermoplastic deformation of the welded components. The formation of a welded joint occurs by moving the stub 4, with the ratio of dmaxstub/Lzag is kOhm 45 (Fig.17). During welding is determined by the nature of the change in the velocity of the stub. For this purpose, they use directly the speed sensor or the speed is calculated by the method of differentiation path, measured by the displacement sensor 45. According to the results of welding estimated as the amount of movement of the stub, and the nature of the change speed 46, 47 (Fig. 18). The presence of 2 peaks speed indicates the stability of the welding process and the quality of the weld.

Contact butt welding stub with sheath diameter 9,13 mm alloy E110 performed under the following mode settings:

Specific pressure - 18-22 kg/cm2;

Welding current - 10-15 kA;

The resistance of the snap - 700-1200 ľohm;

The current pulse duration is not more than 105ISS.

With increasing resistance welding equipment welding force increases, and the energy of the current is reduced. If the resistance of the snap-less than optimal, then the force is reduced, and the energy of the current increase. On the stability of the process is judged by the nature of the changes in the velocity of the stub. The absence of a second peak or a decrease, compared to the original, serves as the basis for either adjustment mode, if the speaker membrane, filled with the gas of specific composition and pressure of the fuel column in contact with one end of the stub, and the other held in a predetermined position, the latch stub connected to the shell welds, characterized in that the plug is in direct contact with the fuel, is connected with the shell welds made of electron-beam welding, and has its seat in the casing throughout the length of the "flats", which forms with the inner surface of the shell technology channel, partially naplavljaemyj in the area of welded joint that connects with a vertical technological channel, located in the plane of the joint and completely naplavlyaemym during welding, and the shape factor of the seam at a depth of penetration of 1.4 - 1.7 wall thickness of the shell is 0.3 to 0.25, the opposite end of the shell remote from the fuel column, connected flash butt welding with a plug having a maximum diameter (dmax) for welding to the length of the working part (LC) 1,8 - 2,4, while between the inner surface of the shell and welded seam formed by the deformed inner layers of the shell and outer layers part of the stub, there is a fold metal, the size of which from the end of saleclause the preparation of the shell and the plug weld, the Assembly of the shell with the cover in direct contact with the fuel, welding caps, including the use of multi-pass electron beam welding, characterized in that in the process of preparing the shell tortsujut from two sides with education on the ends of the conical surface with unequal forming, forming large which is directed toward the outer surface of the shell, and lower in the direction of its inner surface, the angle of taper greater forming with the vertical plane under electron-beam welding is 14-18oand under the contact welding 10 - 20oand the sum of the projections forming the vertical plane is equal to the wall thickness of the shell, while the projection of the outer surface is always greater internal and is 3/4-4/5 of the thickness of the wall of the shell, the end of the shell under electron-beam welding calibrated by precipitation on a metal mandrel with obtaining after assembling it with the cap fit tightly fitted around the perimeter to the length of 6-8 wall thickness of the shell, passing in increasing until the end seats of the gap, the vacuum in the internal volume of the fuel elements is performed with the use of technological channel formed "flats" on the cover and within the ideological channel in the junction, fully naplavlennogo when welding, electron beam welding preheating of the welded connection is carried out prior to the melting of the edges of parts, an additional pass is made with the repeated penetration of the weld metal in the range of the height of the junction to the difference between the height of the joint and the maximum pore size, final sealing of a fuel rod produced by this welding, before welding control no shunt circuit in the secondary circuit of the welding machine and the position of the end face of the shell in the welding equipment, welding is performed with variable speed precipitation stub having a peak value at the beginning and at the end of the move.

3. The method according to p. 1, characterized in that during the electron beam welding the current downturn in the gun at the end of the weld cycle is performed with the rotation of the beam in a circular path with a radius equal 0,28-0,33 joint width obtained after the primary and secondary passages, with the frequency of rotation of the beam 60-80 Hz or preheating, welding and 1/3-2/3 additional passage perform a focused beam, after which it refocusing 1.1 part of its initial diameter.

4. The method according to p. 2, characterized in that the, what if flash butt welding with the increase in resistance above the optimum welding force correspondingly increases, and the energy of the welding current decreases with a decrease in resistance below the optimum welding force is reduced, and the energy of the current increase.

 

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