Method for manufacturing spacer grid of nuclear-reactor fuel assembly

FIELD: nuclear engineering.

SUBSTANCE: proposed method primarily used for manufacturing spacer grids of VVER reactor fuel assemblies involves pre-compression of dynamometric clamp by welding gun electrodes prior to spot welding of shaped subchannels beyond subchannel field, evaluation of compression of welding gun electrodes by displacement distance of clamp jaws and force indicator readings, whereupon information about this compression force is processed in computer and passed to spatial displacement actuating mechanism of welding gun for conducting spot welding of shaped subchannels in assembled field when compression forces of electrodes comply with desired values or for ceasing spot welding when compression forces do not comply with desired values, this information being displayed on computer monitor.

EFFECT: enhanced quality of spacer grid manufactured by this method.

1 cl, 3 dwg

 

The invention relates to nuclear power and may find application in the manufacture of fuel assemblies for nuclear reactors.

Analysis of mechanical properties, radiation growth and relaxation characteristics of grid spacers of zirconium alloys allows to make a conclusion about the benefits of their use at present in the fuel assemblies to increase energy production.

Known spacer grid for nuclear power reactor VVER-1000, collected from individual curly cells welded together at the points and sealed the outside of the rim (see Bajamonti. “Nuclear power reactors VVER-1000”. M.: Energoatomizdat, 1990, p.44, is well), the lack of which is the deformation of the cells in the set of fuel elements, which leads to their marriage.

Known spacer lattice fuel Assembly of a nuclear reactor VVER-1000, collected from individual curly cells welded together at points and bonded to the rim, containing in each cell internal ledges, durable, shrink-fixing passed through the fuel cell elements and preventing radial movement when excited vibrations of structures under the action of turbulent flow of the coolant (see “Development, production, and ek is the operation of the fuel elements from power reactors” Ed. Fgurative, book 1. M.: Energoatomizdat, 1995, table 7.1 on str and str) prototype.

There is also known a method of manufacturing a grid spacers made of an alloy of zirconium, 1% niobium, including set and spot welding figured cells between the education field shaped cells for the passage through them of fuel elements, production of hexagonal rim spacer lattice of an alloy of zirconium, 1% niobium, the typed fields curly cells in the rim of the spacer grid and spot welding the peripheral figured cells to the rim of the lattice (see “Development, production and operation of fuel cell power reactors” edited Fgurative, book 1. M.: Energoatomizdat, 1995, table 7.1. on str and str). According to the existing technology grid spacers for fuel assemblies rim of an alloy of zirconium, 1% niobium is made of two paleologou TIG welding tungsten electrode in a controlled argon atmosphere to prevent oxidation of zirconium during welding. When this welding seam requires Stripping, since the spacer grid should be executed strictly “turnkey”. Cleaning of the weld - removal of influx to the level of the rim can cause damage to the rim, causing scratches on its surface that, due to the properties of qi is Konya, in particular its tendency to corrode corrosion will lead to the destruction of the spacer grid during operation in the reactor. And this, in turn, may lead to violation of the fuel elements, which, under the action of turbulent flow of the coolant, will vibrate to touch each other, and this is influenced by fluctuations even at very low amplitudes does not exclude destruction of the fuel cladding. In the process of TIG welding argon in Boxing contaminated gas products welding, which can easily interact with the Zirconia lattice due to its high chemical activity. This fact will worsen the quality of welding two paleologou lattice to each other, especially in the area of the weld.

It is known that curly cells from an alloy of zirconium, made of thin-walled tubes have fluctuations as the wall thickness and diameter in accordance with the specifications. This leads to the fact that typed in the box curly cells included in the rim or proslavlenie or tightness, but in both cases these variations can adversely affect the quality of the spacer grid and the performance of additional work: in the case of typed fields of cells in the rim with proslavlenie required before spot welding the rim and peripheral cells to carry out Ogata rim to cells which leads to deformation of the middle portion of the face of the rim, whereas in the corners of the rim gaps remain, and increased the gap between the rim and the field of figured cells leads to burnout peripheral cells and marriage; in the case of typed fields of cells with tightness of the deformation of the peripheral figured cells, loss of the established step between cells and occlusion of the openings of the cells for fuel elements during Assembly.

The closest to the technical conditions and the achieved effect is a method of manufacturing the spacer grids of the fuel assemblies of a nuclear power reactor, including the recruitment and spot welding figured cells between the education field shaped cells for the passage through them of fuel elements, production of the rim spacer grid, the typed fields curly cells in the rim of the spacer grid and spot welding the peripheral figured cells to the rim of the spacer grid, where the manufacture of the rim spacer grid, the typed fields curly cells in the rim of the spacer grid and spot welding the peripheral figured cells to the rim spacer grids carried out simultaneously, using as a rim integral part of and the mount point welding of each pair abutting sostav the piece to carry out adjacent to the junction of the peripheral cell (see Patent RU 2155998, IPC 7 G 21 3/34 from 04.08.1998, epubl).

Execution of the rim of the three parts will be excluded as a free - proslavlenny the typed fields curly cells in the rim, and enter in this field the rim with tightness that will exclude marriage by welding to the peripheral rim curly cells and deformation of the latter, while the input cells in the rim, will improve the quality of manufacturing of the spacer grid, hard to get reliable design of the spacer grid with a high quality interface, which excludes welding, seam welding, so that does not create conditions for degradation of Zirconia, which is present in the design of the lattice, since the excluded operation argon-arc welding of the rim in argon, leading to contamination of the weld gas products welding, in addition, the operation of Stripping the weld of flows it is not, therefore, eliminates the possibility of damage to the rim of the spacer grid.

However, to ensure a quality field welding the spacer grid (DR) strict adherence to the process parameters, which are determined by the amount of current, the duration of its existence, the compressing force of the electrodes, the dimensions of the working surface of the electrodes (Nkhabarov, “welding at the contact machines”, M., “Higher school”, 1973, p.65). If the effort is compressed is I little it is possible splash or extrusion of the melt between the parts, and after cooling in the core of the possible shrinkage of the shell and cracks.

In addition, spot-welding the axis of the electrodes should be perpendicular to the surfaces of the welded parts. (Plougasnou, “Point and roller welding of alloyed steels and alloys”, M., “engineering”, 1968, p.39).

The electrodes in the welding process perform three main tasks: compress parts fail welding current and dissipate the heat generated during the welding process. From the shape of the working surface of the electrodes that make contact with details, depends largely on the quality of welded joints. The wear of the working surface and the associated increase in contact area of the electrode-part leads to a decrease of the current density and the specific pressure in the weld zone, and consequently, change the previously obtained sizes of cast area and quality of connections (see Plougasnou, p.36).

When designing sites using point and roller welding it is necessary to provide convenient approaches electrodes and rollers to the place of the compounds (9 ibid p.15). Basically, the approaches to the welding limited by the size of the electrodes, which must provide the required F (compressing force of the electrodes), depending on the thickness, grade, metal, shape of connected components (the m Plougasnou, p.17).

When you change the mode settings in comparison with the nominal falling character R (impedance plot of the electrode-electrode) remains, however, the numerical values at different points of the welding process of change in comparison with the nominal (Fig.3, Plougasnou, p.5).

So, if you raise the compression force of the electrodes Fc grow square contacts and R falls; when it drops Fc reduced area of contact, increasing the dissipation and R increases. By reducing the current ICB reduced size cast zone and increases R, if you increase the current ICB falls R.

The mode is set by the current Iwithduration of his course tc, by the force of the compression ratio RSGsize of the working surface of the electrode deand Reor diameter d (see Nkhabarov “welding at the contact machines”, M., “Higher school”, 1973, p.65).

If the compression force is small, it is possible splash or extrusion of the melt between the parts (see Nkhabarov “welding at the contact machines”, M., “Higher school”, 1973, p.58).

If the compressing force is insufficient, the cooling in the core of the possible shrinkage of the shell, and sometimes cracks. Normally welded point has a dense core (see Nkhabarov “welding at the contact machines”, M., “Higher school”, 1973, p.58).

Details with respect to the thickness of not more than 1:3 weld re the Imam welding of thin parts. Very fine details (δ≤25 mm) weld on particularly hard modes at tc<0,01 seconds (see Nkhabarov “welding at the contact machines”, M., “Higher school”, 1973, p.72).

Pressure, temperature and duration of their action significantly affect the structure of compounds. When a large pressure is greater crushing of grains, and if possible small pores (see Nshibanova, “welding at the contact machines”, M., “Higher school”, 1973, p.18).

In the method prototype for the patent 2155998 information to control the compressing force of the electrodes is missing, when the reproduction method may lead to marriage welding grid spacers, because at low force compression of the electrodes is possible splash or extrusion of the melt between the parts and the pores in the cast area, and when a large force compression of the electrodes increases the crushing of the grains.

An object of the invention is to improve the quality of manufacturing of the spacer grids of the fuel assemblies of a nuclear power reactor.

This technical problem is solved in that in the method of manufacturing the spacer grids of the fuel assemblies of a nuclear power reactor, including the recruitment and spot welding electrodes welding tongs shaped cells between the education field shaped cells for the passage of fuel through them the elements the manufacture of the rim of the component parts, spot welding the peripheral cells of the constituent parts of the rim to mount each pair of abutting parts of the rim adjacent to the junction of the peripheral cell; according to the invention before spot welding figured cells between the education field shaped cells of the spacer grids carry out curly cells pre-compression torque bracket electrodes welding tongs, determined by the displacement of the jaws torque bracket and indicator efforts compression electrodes welding tongs, information on efforts compression which, after processing in the computer is issued to the actuator spatial movements welding tongs for carrying out spot welding figured cells in the collected field in accordance efforts compression of the electrodes specified effort, or termination of spot welding in overstating or understating efforts compression electrodes welding tongs relative to a given compression force of sending information to the monitor.

The proposed method of manufacturing the spacer grids of the fuel assemblies of a nuclear reactor will allow to solve the technical problem to improve the quality of manufacturing of the spacer grids of the fuel assemblies of a nuclear power reactor.

p> The drawings show a method of manufacturing the spacer grids of the fuel assemblies of a nuclear reactor, where:

figure 1 is a device for implementing the method of manufacturing the spacer grids;

- figure 2 - electrode welding tongs;

- figure 3 - the spacer grid.

A method of manufacturing the spacer grids of the fuel assemblies of a nuclear power reactor includes a set, spot welding curly cell 1 between the education field figure 1 cells to pass through them fuel elements 2, the manufacture of the rim 3 of the component parts, spot welding the peripheral cells 1 to the integral part of the rim 3 with fastening each pair of abutting parts of the rim 3 to the adjacent to the junction of the peripheral cell 1.

Before spot welding curly cell 1 between the education field shaped cells 1 spacer grids carry out curly cells 1 preliminary compression torque bracket 4 electrodes 5 welding tongs 6 and determined by the displacement of the jaws 7 a torque bracket 4 and the indicator 8 compression force of the electrodes of the welding tongs 6.

Information on efforts compression after processing in the computer 9 is issued to the actuator 10 of the spatial movement of the welding 6 ticks on holding point with the arch shaped cells 1 in the assembled box in accordance efforts compression electrodes 5 a given effort, or termination of the welding point in overstating or understating efforts compression welding electrodes 5 6 ticks relative to a given compression force of sending information to the monitor 11.

Make the spacer grid as follows. In the welding jig 12 carry out a set of curly cells 1. Before spot welding between a stateful compression force of the welding electrodes 5 6 ticks, which carry out dialed figured cells 1 preliminary compression torque bracket 4 between the electrodes 5 welding tongs 6.

Offset jaws 7 torque bracket 4 and the indicator 8 determine the compression force of the electrodes 5, information about the compression force is transmitted to the computer 9, which issues a command to the actuator 10 of the conduct of spot welding figured cells 1 to each other when the compression force of match. If efforts do not match, then the information is transmitted to the monitor 11 and the operator makes the appropriate adjustments to the compression force of the electrodes 5.

After the box shaped cells 1 are, carry out spot welding the peripheral cells 1 to the integral part of the rim 3.

Ready spacer grid is installed in the frame on the guides and channels in cell 1 for a given program is administered TVEL is 2, secure the head and the shank and the fuel assemblies loaded in the core of a nuclear reactor.

A method of manufacturing the spacer grids of the fuel assemblies of a nuclear power reactor, including the recruitment and spot welding electrodes welding tongs shaped cells between the education field shaped cells for the passage through them of fuel elements, production of the rim of the component parts, spot welding the peripheral cells of the constituent parts of the rim to mount each pair of abutting parts of the rim adjacent to the junction of the peripheral cell, characterized in that before spot welding figured cells between the education field shaped cells of the spacer grids carry out curly cells pre-compression torque bracket electrodes welding tongs, determined by the displacement of the jaws torque bracket and the indicator of the compression force of the electrodes of the welding tongs, information on efforts compression electrodes after processing in the computer is issued to the actuator spatial movements welding tongs for carrying out spot welding figured cells in the assembled box in accordance efforts compression of the electrodes given effort or termination of spot welding at overestimate or sanii the NII efforts compression electrodes welding tongs relative to a given compression force of sending information to the monitor.



 

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