The method of welding the spacer grids of the fuel assemblies of a nuclear reactor

 

The invention relates to nuclear energy and may find application in enterprises that manufacture fuel assemblies (FA) for nuclear power reactors. The technical result of the invention is the expansion of technological capabilities and improving the quality of welding cells with the rim and hub by determining the point of coupling of the welded surfaces and reduce technological deformation during welding. In the method of welding the spacer grids of the fuel assemblies of nuclear reactors, including the operation of the Assembly field of the lattice, welding, compression throughout the whole time of welding, adjustment of the positioning of the electrodes in the process of their movement, welding line, skipping the cells located in places of passage of the guide channels, according to the invention for adjusting the positioning of the electrodes during the welding cells of the main field with the rim move the electrodes parallel to the welded flat surface, double-touch the electrode to be welded cylindrical surface of the cell, and then calculate the trajectory of the electrodes, passing through the midpoint between the points of the electrode touches the cylindrical surface and perpendi can find application in enterprises, manufacture of fuel assemblies (FA) for nuclear power reactors.

The spacer grid (OTHERS) in the FA must provide the exact location of the fuel elements (FE)in accordance with a specified step, to comply with such conditions, when each cell is connected with the neighboring cells, the rim and the Central bushing pin-point welding must be in place by welding the molten core of the required equivalent area (OST.95.503-84 the industry standard. Connections welded and brazed for products active zones of nuclear reactors. General technical requirements).

When designing sites using point and roller welding it is necessary to provide convenient approaches electrodes and rollers to the place of the compounds (P. L. Chulochnikov, “Point and roller welding of alloyed steels and alloys”, M.: engineering, 1968, page 17). In this regard, it is technically difficult to provide quality welding cells of the main field to the rim or the center hub to the cells, i.e., the cylindrical surface to the plane (see ibid page 15, Fig.9). This is due to the fact that may be compromised the accuracy of the placement of cells collected field cells due to deviations of the wall thickness of the tubes, ispolzueschemu, what can cause positioning of the cells of the spacer grid relative to the nominal grid, and “spot-welding the axis of the electrodes should be perpendicular to the surfaces of the welded components” (see page 39), i.e., the movement of the electrodes should be directed through the contact point of the welded parts between a normal to their surfaces. In the case of non-compliance with these conditions, the compressing force of the electrodes will not provide compression of the welded surfaces and optimum area of contact will increase the dissipation and impedance plot of the electrode-electrode (see ibid, page 5), and this may affect the quality of welding the spacer grid may be outbursts, the spots will not meet the requirements.

There is a method of resistance spot welding with compression of the peripheral zone connections (see Russian Federation patent No. 2036759, 23 To 11/10, publ. 09.06.1995), in which the total compression force of parts set of conditions of forging connections and maintain it unchanged during the entire weld cycle. The amount of force compression set equal to the difference between the total force of the compression part and the force on current-carrying electrodes. After Imstalcon this method is the possibility of technological deformation of cells in the welding process (see P. L. Chulochnikov, “Point and roller welding of alloyed steels and alloys”, M.: engineering, 1968, page 88), which may lead to the violation of their positioning in the spacer grid.

The closest in technical essence and the achieved effect is the method of welding the spacer grids of the fuel assemblies of nuclear reactors, including the operation of the Assembly field of the lattice, welding, compression throughout the whole time of welding, adjustment of the positioning of the electrodes in the process of their movement, welding line, skipping the cells located in places of passage of the guide channels (see patent RU 2152085, MPK7 G 21 3/34, published 27.06.2000) prototype. The disadvantage of this method is the inaccuracy based electrodes when welding cells with a Central hub and rim, which may lead to the closure of the electrodes are not at the point of contact of the cell and the rim, and this may lead to technological deformations change the compression force of the electrodes in the process of entering the weld point and the reduction of laser pulse as a result of the bypass because of the touch electrode surface of the cell is not in the place of welding.

An object of the invention is to expand the population point of coupling of the welded surfaces and reduce technological deformation during the welding process.

This technical problem is solved in that in the method of welding the spacer grids of the fuel assemblies of nuclear reactors, including the operation of the Assembly field of the lattice, welding, compression throughout the whole time of welding, adjustment of the positioning of the electrodes in the process of their movement, welding line, skipping the cells located in places of passage of the guide channels, according to the invention, to adjust the positioning of the electrodes during the welding cells of the main field with the rim move the electrodes parallel to the welded flat surface, double-touch the electrode to be welded cylindrical surface of the cell, and then calculate the trajectory of the electrodes, passing through the midpoint of the segment between points touch electrode cylindrical surface and perpendicular to the plane of the rim.

The application of the method will improve the quality of the welding rim with cells of the main field, which, in turn, will increase the reliability of fuel assemblies in a nuclear reactor.

The drawings show a method of welding the spacer grids of the fuel assemblies of a nuclear reactor, where

Fig.1 shows the spacer grid;

Fig.2 - location of electrode welding.

The method is carried out in the following order: operation Assembly field of the lattice cells of the main field 1, the peripheral cells 2, the Central sleeve 3, the circuit of the field in hex rim 4, the compression him during the entire welding time, welding cells 1, 2 between them, adjusting the positioning of the electrodes 5, 6 in the process of their movement parallel to the face of the rim 4, touching the electrode 6 of the cylindrical surface 7 of the cell 1 at the points 8 and 9 with subsequent determination of the midpoint of segment 10 between these two points and passing through the midpoint of the segment 10 normal 11 to the edge of the rim 4, which will be the line of movement of the electrodes 5, 6 when welding cells of the main field 1 with the rim 4. At this point touch electrodes with cell and rim 12-13 and the touch point of the cell with the rim 14 lie on the normal 11.

Claims

The method of welding the spacer grids of the fuel assemblies of a nuclear reactor, comprising an Assembly operation field of the lattice, welding, compression throughout the whole time of welding, adjustment of the positioning of the electrodes in the process of their movement, welding line, skipping the cells located in places of passage of the guide channels, wherein for korrektirovki is those flat surfaces, double-touch the electrode to be welded cylindrical surface of the cell, and then calculate the trajectory of the electrodes passing through the midpoint of the segment between points touch electrode cylindrical surface and perpendicular to the plane of the rim.

 

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FIELD: nuclear power engineering.

SUBSTANCE: proposed method is used for manufacturing fuel assemblies for type VVER-1000 and VVER-440 reactors. In order to check spacer grid for passability it is placed in machine between two covers with depressions that follow grid outline and blind holes coaxial to each subchannel of grid accommodating calibrated balls, then it is tuned together with covers through 180 deg., subchannels of inadequate caliber are detected and burnished by means of drift. For checking diameter of circumference inscribed in subchannel the grid is placed in machine equipped with large-diameter calibrating balls, subchannels through which these balls have passed are detected and squeezed by means of clamping tool with jaws disposed in holes between subchannels. Decision on quality of spacer grid subchannels is taken by sticking of balls in them as spacer grid is turned in machine through 180 deg. Balls of different diameters are differently colored.

EFFECT: enhanced quality and yield of spacer grids.

2 cl, 4 dwg

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

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

FIELD: nuclear power engineering; spacing apart fuel elements in reactor fuel assemblies.

SUBSTANCE: proposed method includes insertion of auxiliary inserts in assembly field holes designed for guide channels and central tube with desired inscribed circumference in each hole prior to spot welding of subchannels to join them together in assembled field; these auxiliary inserts have same diameter as guide channel and central tube and their temperature coefficient of linear expansion equals that of subchannel material; spot welding of subchannels to each other and to rim is effected while inserts are installed and upon heat treatment these inserts are removed.

EFFECT: enhanced quality and yield of spacer grids.

1 cl, 1 dwg

FIELD: nuclear power engineering; spacing apart fuel elements in reactor fuel assemblies.

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EFFECT: enhanced quality and yield of spacer grids.

1 cl, 1 dwg

FIELD: nuclear power engineering.

SUBSTANCE: proposed fuel assembly primarily designed for use in nuclear power reactors VVER-1000 and VVER-440 has composite bottom spacer grid built of at least two parts identical with respect to disposition of holes and total thickness of component parts equal to height of circular collar on bottom plug of fuel element, and tubular channel hole diameter for bottom plugs equal to diameters of lower ends of bottom plugs; the latter are secured in holes of aligned parts of bottom spacer grid by shifting component parts of bottom spacer grid relative to each other, by locking bottom plugs on circular collar of bottom plugs between annular projections of upper and lower parts of bottom spacer grid, and by aligning flow holes of bottom spacer grid component parts. Component parts of bottom spacer grid are rigidly fixed upon their shifting to bottom nozzle of fuel assembly in case of nonseparable type of assembly and loosely attached upon their shifting to bottom nozzle in case of separable type of assembly.

EFFECT: enhanced reliability of fixing fuel element plugs in bottom grid holes of separable and nonseparable fuel assemblies, reduced labor consumption for manufacture and assembly.

1 cl, 3 dwg

FIELD: nuclear power engineering.

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EFFECT: enhanced reliability of fixing fuel element plugs in bottom grid holes of separable and nonseparable fuel assemblies, reduced labor consumption for manufacture and assembly.

1 cl, 3 dwg

FIELD: nuclear engineering.

SUBSTANCE: proposed spacer grid designed for assembling fuel rods in triangular arrangement primarily used in type VVER reactors has encircling band and three groups of relatively intersecting strips arranged in parallel in each group and provided with slits at points of intersection, as well as with alignment stops disposed between adjacent alternate slits. Intersection of strips forms subchannels for receiving fuel elements and bonding elements. Elements are shaped as equilateral triangle in cross-sectional area and look like figure with convex sides whose centers of curvature radii are disposed on lines crossing intersection point of strips and axis of fuel element engageable with this side. Alignment stops on each strip are made in the form of bends. In addition mixing blades are provided on at least two groups of strips and unidirectionally positioned in one group of strips. Bends provided on each strip between adjacent alternate slits make it possible to obtain bonding elements of different type at strip intersection point thereby enabling formation of shaped subchannel with alignment stops of sufficient elasticity margin (elastic displacement margin or stiffness coefficient).

EFFECT: enhanced precision of fuel element alignment and stiffness of its locking in subchannel.

5 cl, 13 dwg

FIELD: nuclear power production, possibly processes for making spacing grids of fuel assemblies assembled of cells formed of tubular blanks.

SUBSTANCE: method comprises steps of securing solder in the form of amorphous belt to edges of cells; selecting surface area of solder in the form of amorphous belt secured to edges of cell in range 0.17F -0.61F where F - surface area of cell edge; placing cells in jig for further heating soldered surfaces higher than temperature of solder melting; pressing soldered surfaces one to other with effort in range 300 - 500g/sq.cm.

EFFECT: enhanced corrosion proofness and strength of soldered joint, increased rigidity of the whole spacing grid.

4 cl, 1 dwg

FIELD: nuclear power engineering; nuclear reactor fuel assembly manufacture.

SUBSTANCE: in order to improve shape and appearance of fuel assembly subchannels, to raise precision of their geometry, to minimize stresses during fuel assembly manufacture and introduction of fuel-element spacer grids in subchannels we propose to select press tools by actual wall thickness of tube and, consequently, that of subchannel billets using formula S die = K springiness (S of subchannel - 2S of billet wall); billets and subchannels are degreased, rinsed, and dried out, then placed in jig, subchannels are compressed, welded by means of robot, coordinates of welded subchannels are computed, spacer grid is oxidized and inspected by illuminating with laser beam and sorted out, and fuel assembly is produced without varnishing, and inserting expansion tip.

EFFECT: enhanced quality and operating reliability of fuel assemblies.

5 cl, 5 dwg

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