Tvel, a method of manufacturing rods and device for its implementation

 

(57) Abstract:

The invention relates to nuclear engineering, the design of fuel elements and their manufacturing techniques. The inventive fuel rod contains a shell and welded it with a landing plug. In the zone of welding stub created a region with a modified metal structure on the penetration depth of the insert is equal to (2-5), and the thickness from the inner surface of the shell not higher than 0.9 d, where d is the thickness of the walls of the shell. The method includes manufacturing a stub having an outer diameter larger inner diameter of the shell (of 0.2 - 1.4)d, where d is the thickness of the walls of the shell; the fixation of the membrane in the electrical power supply with depth; the compression shell with cover and heat welded parts electric shock. The current spread on the current supply and the shell so that the current flowing in the section of shell length (2-5)d from its end, was 0.3-0.9 welding current, while providing heat removal from the outer surface of the shell. The device comprises a ring current supply, part of which is in contact with petrovoi area, made of a set of electrically isolated plates connected between an electrical shunt. Each of the plates is made of a thickness of 0.2-2)d, the GFC. f-crystals, 5 Il.

The invention relates to nuclear technology, in particular, to the design of fuel elements and their manufacturing techniques.

Known fuel rod containing shell and varennuyu her with a hollow stub (ed.St. USSR N 1762694, class B 23 K 11/02, 1989 [1]). In a known fuel rod to improve the efficiency of performing the fold of the shell near the weld zone. The disadvantage of TVEL is the complexity of its manufacture, is not high enough structural strength of the connection and corrosion resistance.

Closest to the claimed by its technical essence is known a fuel rod containing the tubular shell and welded it with a landing plug in a weld zone which created a region with a modified metal structure (application Germany N 4222180, CL G 21 C 21/00, B 23 K 11/02, 1922 [2]).

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.

A known method of manufacturing a fuel pressure butt welding (ed. St. USSR N 1520763, CL 23 To 11/02, 1987 [3]). The method involves the fabrication stub darwinianism, application to welded details the efforts of the compression and transmission through them welding current.

The disadvantage of this method is the impossibility of obtaining changing the structure of the metal in the welding zone with the optimal balance of size and desired configuration, which provides increased structural strength and corrosion resistance.

Closest to the claimed is a method of flash butt resistance welding pipes with blank used in the manufacture of fuel elements (ed. St. USSR N 1596576, CL 23 To 11/02, 1987 [4]). The method includes manufacturing a stub with an outer diameter greater inner diameter of the shell, but less external, the fixation of the membrane in the electrical power supply with depth, compression shell with cover and heat suasively 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.

A device dleu feeding, part of which is in contact with pretorias part of a shell made of metal plates electrically isolated from each other (ABT. St. USSR N 664785, CL 23 To 11/02, 1977 [5]).

The known device provides effective heat removal from the welding zone, but does not allow you to adjust the ratio of the currents flowing through the current lead and the shell, and as a result does not provide the possibility of creating in the zone of the welding area with a modified structure of metal of the desired ratio, the presence of which in a fuel rod increases its performance.

Closest to the claimed is known device for forming a connection with the manufacture of fuel rods by the method of flash butt welding, 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 (ed. St. USSR N 1508458, CL 23 To 11/02, 1987 [6]).

A disadvantage of the known device, despite the ability to control the values of the currents flowing through the current lead and the shell is that it does not allow sformirowal aims to increase its structural strength and corrosion resistance, and the inventive method of manufacture and a device for implementing the method is aimed at ensuring the formation in Fe region with a modified metal structure with a ratio of a size to provide the specified result. In addition, the inventive method is intended to simplify the production technology of the fuel rods due to the receipt of a welded joint without external Burr.

This result is achieved in that the fuel rod contains a shell and welded it with a landing plug in a weld zone which made the region with a modified metal structure on the penetration depth of the insert is equal to (2-5), and the thickness from the inner surface of the shell not higher than 0.9 d, where d is the thickness of the walls of the shell.

Distinctive features of the proposed Fe is the ratio of the sizes of the running area with a modified metal structure and its location, namely the length of the shell size of the region is the amount of penetration of the plug (i.e., from the end of the shell to butt plugs) and two equal five shell thickness, and depth from the inner surface of the shell not higher than 0.9 from its thickness.

Changing the structure of the material in the weld zone, as shown practiceno, the ratio of the size and location of the region with a modified structure of the metal affects the structural strength and corrosion resistance of a fuel rod. In particular, when the ratio of the size of the area affected by design changes along the shell less than two thicknesses worsens as the corrosion resistance of a fuel rod and its structural strength, while increasing the length of the field to 5d is a noticeable improvement in performance characteristics is not observed, but increases consumption of a product that, given the cost of the material becomes uneconomic.

It is found experimentally that if the thickness of the created region with a modified structure of the metal from the inner surface of the shell over (2-5)d from its end face is at least a few microns, it becomes a noticeable improvement in the performance of this product, but if the thickness of this zone increases to dimensions higher than 0.9 d, then begins to degrade the corrosion resistance. The optimal size ratio, as shown by the experiments, is the thickness (0.2 to 0.5)d.

This result is achieved in that the method of manufacture of fuel elements with the required configuration area with izmeneniya shell on (0,2-1,4)d, where d is the thickness of the casing wall, the fixation of the membrane in the electrical power supply with depth, compression shell with cover and heat welded parts, electrical current, which distribute the electrical power supply and the shell so that the current flowing in the section of shell length (2.5 to 5)d from its end, was 0.3-0.9 welding current, while providing heat removal from the outer surface of the shell.

This result is achieved by the fact that in particular cases the implementation of the method of manufacture of a fuel rod blank is made step one part facing the shell is made of diameter D + (0,2-1,4)d height (0,5-3,0)d, and the second diameter is equal to D to 0.2 d, where D is the internal diameter of the shell.

In addition, in certain cases, the implementation of the method at the end of the shell to the external chamfer so that the diameter of the stub was greater than the external diameter of the end rings of the shell on (0,1-0,3)d.

Distinctive features of the proposed method are: production of caps having an outer diameter exceeding the inner diameter of the shell (of 0.2-1.4)d; formation of the distribution of current flowing through the shell and a current supply so that the amount of current flowing through the portion of the sheath from the end of the date so the diameter of the part facing the membrane was equal to D + (0,2-1,4)d and height (0,5-3,0)d, and the diameter of the second part is equal to D to 0.2 d, where D is the internal diameter of the shell.

Through the use of the whole set of features stated in the independent claim, characterizing the way, produces in visitors Fe region with a modified structure of the metal in the weld joint area with the required ratio of the dimensions and configuration.

However, as a result of technological experiments established the boundary values of the individual parameters on the achieved results. In addition, it was found that the selection of process parameters is possible not only in the formation of product sizes, but also manufacture products with no external Burr, eliminating in the process the operation for its removal.

In particular, the excess of the outer diameter of the stub on the internal diameter of the shell by an amount greater than 1.4 d increases the probability of formation of external Burr and degrades the quality of a welded joint, as expanding area of thermocline in the shell. If exceeded, as mentioned size less than 0.2 d who is the process of exploitation.

Set that to provide education with a modified metal structure necessary aspect ratios need to create a local heating of the shell in the weld zone, namely plot length (2-5)d from the end of the shell. To create this electric heating properly create the required distribution of the currents flowing through the current lead and the heated area of the shell. For example, on the surface of this section of the sheath is applied insulation coating with the calculated resistance or this coating is carried out on a dedicated section of the electrical power supply in contact with the shell or pick up material with a specific resistance of which is made the part of the electrical power supply, which comes in contact with the specified area of the shell.

In this case, as shown by the experiments, each of these techniques has its advantages and disadvantages. In particular, in the case of insulating coatings in the respective areas, complicates the technology, do not allows you to adjust the achieved ratio of currents or does not provide the most optimal dimensions of the area with the changed structure of the metal. The most expedient was used for forna from a set of isolated plates. The appropriate parameters are selected so that through that section of the shell flowed from 0.3 to 0.9 welding current. If the amount of current flowing through the section of the sheath from the end surface to the distance from the (2,0-5)d is less than 0.3 of the welding current, the shell is heated to a temperature substantially below the temperature of the stub, which degrades the quality of the welded connection. The same pattern is observed if more current is 0.9, but in this case becomes overheated shell.

In private cases, the implementation of the method should be carried out at the end of the shell outer chamfer. The presence of the bevel can improve the reproducibility of the welding results, i.e., to ensure the production of products with the same quality, negating the effect of misalignment of the location of the stub and envelope on the distribution of currents in the weld zone, since the contact area of the plug shell is always constant, and therefore will provide uniform heating of the workpiece around their perimeter. In this case, as shown by the experiments, the result is achieved in all cases perform a chamfer in the specified range of ratios of geometric parameters.

Manufacturer stub with these two sootnosheniyami region with a modified metal structure, namely, from 0.2 to 0.5 d thickness from the inner surface of the shell.

This result is achieved by using the proposed device for the formation of compounds in the manufacture of fuel elements flash butt welded shell with a stub that contains the 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 with the following ratios of sizes: each of the plates is made of a thickness of 0.2-2)d, where d is the shell thickness, and the size of the inlaid part of the electrical power supply along the axis of the hole made in length (2,5-6)d.

The hallmark of the claimed device is the ratio of the sizes of the inlaid part of the electrical power supply, made of plates. Due to the specified ratio in visitors Fe region is formed with a modified structure of the metal to the desired configuration. Deviations from these ratios in either direction leads to a change in the ratio of the size of the area with the changed structure of the metal to such an extent that improving the performance characteristics of manufactured products is not observed. The presence of electricaccelerator shunt selected, based on the material of the busbar, shell and their sizes. To ensure the universality of the device, the shunt should be performed removable and made of materials with different resistance. The shape of the shunt can be any of the known, for example, in the form of a tape or cone studs [6] current lead may not be supplied with an insulating sleeve, as in the prototype, because its function can be fulfilled by a layer of insulating coating, which is applied to the sponge Tsang welding machine.

In Fig.1 shows a fuel rod, a longitudinal section before welding, and Fig.2 is a longitudinal section after welding; Fig.3 photograph of a thin section of a welded joint; Fig.4 apparatus for forming compounds in the manufacture of fuel rods, the cross-section of Fig.5 a special case of the method with two-door.

TVEL includes (Fig.2) the shell 1 is filled with fuel (not shown), and mounted in such deeper the plug 2, in the welding zone which formed area 3 (highlighted by the dotted line) with a modified metal structure.

Device for the manufacture of fuel rods (Fig.4) contains the ring current lead 4.

Part of the electrical power supply 4 in contact with pretorias area of the shell 1 made of metal is actrices shunt (not shown).

The inventive method of manufacture is generally implemented in the process of the claimed device as follows.

The device establishes an electrical shunt with parameters (determined by calculation on the basis of the electric resistance of the membrane, its size, the material of the shunt and so on), ensuring the specified current distribution between the shell and inlaid part of the electrical power supply (the size of the inlaid part of the electrical power supply device is equal to the length of the shell in which you want to create the necessary current plus the amount of penetration of the shell in the current lead).

The shell 1 is secured on the electrical power supply 4 depth (0.5 to 2)d, the plug 2 is inserted into its electrode holder (not shown) and is compressed by the axial force of the shell blank, simultaneously feeding a pulse of welding current, for example, from commercially available condenser machine MTC-5001.

As a result, in accordance with Ohm's law, the currents are distributed through the shell and feeding (shunt), forming in the weld zone region with a modified structure of the metal. Composing a part of the electrical power supply at the same time performs the function of heat dissipation from the outer surface of the shell.

After removing the welding usilivalos method and proposed for implementation of the device of the fuel rods had a high quality of welded joints, defects, most of the length of weld, its location along the longitudinal axis of the shell. In addition, the obtained products were no external Burr, which exclude them from subsequent machining, and in the outer layers of the shell in the zone of welding preserved the original structure of the metal.

To validate the properties of fabricated fuel rods made with them in the zone of the welding area with a modified structure of the metal, carried out the appropriate tests, which included: control appearance by comparison with a standard; ultrasonic inspection; establishing a gas pressure in the shell; analysis of thin sections of welded joints; corrosion testing; validation of the strength properties by the shock of the limb outwards sector shell width of 2-3 mm (destruction of the shell where it mates with the plug did not occur even when the angle of the limb 180oC).

According to the results of the test fuel rods fabricated using different process parameters were manufactured and tested 300 products) were found to be optimal, allowing to obtain a region with a modified metal structure of a given configuration.

The increase in the operating characteristics of the fuel elements, izgotovlenie the metal structure is oriented transversely of the shell, and in accordance with the invention along it.

TVEL containing envelope filled with nuclear fuel, and at least one stub welded to it with a deep, characterized in that the weld seam and the area changed from welding the metal structure is made on the penetration depth of the insert is equal to (2-5), and the thickness from the inner surface of the shell not higher than 0.9 , where is the wall thickness of the shell.

2. TVEL under item 1, characterized in that the area changed from welding structure of the metal from the inner surface of the shell is made of a thickness equal to (0,2-0,5).

3. A method of manufacturing a fuel pressure butt welding, including manufacturing stub with an outer diameter, a large interior, but a smaller 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 electrical shock while simultaneously providing heat removal from the outer surface of the shell, wherein the cover is made with an external diameter of

D+(0,2-1,4),

where D is the inner diameter of the shell,

and in the process of heating electric current flowing through the current lead, and a shell distribution is 3 0.9 amperage welding.

4. The method according to p. 3, characterized in that the cover is made length (0,5-3,0) and provide its end with a diameter equal to D 0,2 .

5. Device for the manufacture of a fuel rod by forming connections with contact butt welding of the shell with a cover containing ring current supply, part of which is in contact with pretorias area of the shell, made of a set of electrically isolated plates connected between an electrical shunt, wherein each of the plates is made of a thickness of 0.2 - 2), and the size of the inlaid part of the electrical power supply along the axis of the inner hole is (2,5 - 6).The

 

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