Nuclear reactor fuel assembly

FIELD: nuclear power engineering.

SUBSTANCE: members used for fastening fuel element in hole of bottom end spacer grid are made in the form of shortened plug that has coaxial blind hole on its butt-end formed by annular walls expanded (burnished) in hole of larger diameter within bottom end spacer grid.

EFFECT: enhanced reliability of fuel assembly, reduced manufacturing cost and structural material input.

1 cl, 3 dwg

 

The invention relates to atomic energy and can be used in the manufacturing of fuel assemblies for nuclear reactors mainly of type water water power reactors VVER.

Known fuel assemblies of a nuclear reactor VVER-440, including a bunch of fuel elements (FE), established in the frame of the grid spacers hex form, mounted on a Central tubular channel, fixed together with the Fuel rod lower end in the lower grille, a shank connected with the lower grille with adapters attached in the corners of this grid, the case covering the whole bundle of fuel Rods of hexagonal tubes attached at one end to the shank, a head fixed to the other end of the cover, and the elements ensuring the fixing of the fuel Rods in the lower grille (see Dementiev B.A. “Nuclear power reactors”: the textbook for high schools, 2eedition, revised and enlarged, M.: Energoatomizdat, 1990, p.31-35).

In the known fuel Assembly against axial movement up and down the Rods fixed in the lower grille its lower plugs placed in their respective holes. As part of preventing axial movement of the Rods relative to the lower grille down, used a circular ledge on each bottom flap over the top of torso is this grid.

Axial movement of the Rods relative to the lower grille up is limited by a pin placed in a groove made on the lower end of this lower grilles along the series of holes for the bottom stub of a fuel rod and passing through holes in each bottom cap on the level of the above-mentioned groove for placement of the splint. The number of pins corresponds to the number of rows of fuel Rods in the fuel assemblies. Both ends of each pin is fixed on a lateral side of the lower grille. Central tube channel used for placement in the TVs measuring devices attached to its tip at the bottom of the grille the same mount as the Fuel elements.

The disadvantage of this FA is the high complexity of its manufacture due to manual operations orientation of each fuel rod holes in the plugs towards the cotter pin, splineway through holes in the bottom stub of each fuel rod and the fixing pin by welding. These operations do not lend themselves to automation. Known nuclear fuel assemblies of VVER-1000 reactor comprising a bundle of fuel Rods mounted in the frame of the grid spacers hexagonal shape, mounted on tubular channels fastened together with the fuel rods of the lower plugs in the lower grille, a shank connected with the lower grille with adapters attached in the corners of this grid, head and members, about is ensuring the fixing of the fuel Rods in the lower grille (see ibid, p.41-45). This FA, except for the Central one, has a number of tubular channels are used for control rods.

The fuel rods fixed in the lower grille similar to that in the above-described assemblies, by the way. The shank is equipped with a system of support ribs for the bottom of the grid that are adjacent to its bottom end, and the head is fixed on a projecting from the bundle of fuel Rods of the upper tubular channels for control rods.

This FA has the same drawback that FAS are described above, but expressed more explicitly, since it has almost three times as much Fuel, therefore, the higher the complexity of the operation of mounting pins when attaching the bundle of fuel Rods in the lower grille. In addition, both teplovidelyaushaya Assembly are molded, which creates certain difficulties when replacing one or more fuel elements and fuel assemblies, and the grooves on the lower ends of the lower bars for splints, placed perpendicular to the flow of coolant can cause unpredictable vibration FA and destruction by welding the lower plug of a fuel rod.

Closest to the technical essence and the achieved effect is a fuel Assembly of a nuclear reactor, mainly VVER, including bundle of fuel elements installed in the frame of the grid spacers mounted on the tubular channels, sakralen the x with fuel elements, the bottom plugs in the bottom grid with adapter, shank support ribs attached to the adapter lower grilles, head, mounted on the upper ends of tubular channels, and elements that provide anchorage of the bottom stub of the fuel elements in the lower grille (see Russian Federation Patent RU 2079170 from 30.05.1995 published 10.05.1997, IPC 6 G 21 With 3/32).

In the fuel Assembly of the prototype at the lower plugs fuel elements lower ends before Assembly cut longitudinally into two equal parts, and when assembling the fuel Assembly these equal parts for the bottom end of the lower grille apart, for example, setting them on a tapered mandrel.

Fuel Assembly-prototype eliminates the disadvantages of the known FA in terms of complexity due to the exclusion of spontania Rods, automation fixing plugs of the fuel Rods in the lower grille and the possibility of substitution of one or more fuel Rods, i.e. the fuel assemblies can be called as a variant of the folding assemblies. However, it is not considered that the thickness of one Rassegna part is 1.5 mm, which does not exclude its bending, damage at the stage of manufacturing and transportation. During the pressing of a fuel rod through 15 grid spacers and bottom bars when assembling the fuel Assembly could be damaged rasset is the R parts of the lower plug during Assembly FA. Not be damaged dissected parts of the lower stub in the process of their precipitation on the mandrel. TVEL broken, at least one part goes into the marriage.

It is known that nuclear reactors VVER reactors operate at temperatures 270-330°With coolant and the pressure of 10-20 MPa with a flow of coolant from the bottom up active zone (see “Development, production and operation of fuel cell power reactors”. Book 1, M, Energoatomizdat, 1995, p.14, §1.2), that does not preclude axial displacement of a fuel rod from the bottom up in FA and ejection from the holes on the bottom of the lattice. In addition, the diluted part of the lower plug of a fuel rod create additional resistance to the flow of coolant. If we consider that the lower ends of the plugs are placed in the holes on the bottom of the lattice with a gap, you may experience unpredictable vibration of the fuel elements and the destruction of the weld membrane of a fuel rod with the bottom bracket, so as zirconium is prone to corrosive corrosion resulting from fluctuations even at very low amplitudes (see “the metallurgy of zirconium”. Translation from English. Publishing house of foreign literature, M., 1959, str).

When assembling the fuel Assembly to prevent damage to the bottom dissected parts of the lower plugs the fuel rod during insertion through the cells of fifteen parallel installed the spacer is of ECETOC before pressing on the cut part of the bottom plugs were installed polymer tips. The insertion of a fuel rod through the cells of the spacer grids was carried out tips forward until the bottom of the lattice. Front lower grille pressing the continued removal tips, and then go finish pressing of a fuel rod lower part of the lower plug in the hole in the bottom of the lattice, where the bottom end of the lower grille was carried out sediment cut part of the bottom plug mandrel. Stop pressing, the reduced performance of the Assembly FA, and manual removal tips in front of the lower grille and the burnishing dissected part of the stub increased labor costs and increased the cost of manufacturing fuel assemblies.

According to the requirements of the Fuel rod volume fraction of structural materials should be minimal (see “Development, production and operation of fuel cell power reactors”. Book 1. Edited Fgurative. - M.: Energoatomizdat, 1995, p.44). However, in the design of the fuel assemblies and prototype fuel Rods in conflict with this requirement, as are long, the bottom plug having directly end-sealing fuel rod portion located above the bottom grid, the middle part is located in the hole of the lower grille, and the lower mounting portion under the lower grille, which is dissected along its ends by donovania divorced in hand. While at donovani cut the ends of the lower plug in contact with sharp edges of the holes on the bottom of the lattice can be damaged until it is time to trim.

An object of the invention is to improve the reliability of operation of the fuel assemblies in a nuclear reactor, the reduction of production cost and volume fraction of the material of construction.

This technical problem is solved in that in the fuel Assembly of a nuclear reactor, mainly type reactors, including the bundle of fuel elements installed in the frame of the grid spacers mounted on the tubular channels fastened together with fuel elements of the lower plugs in the bottom grid with adapter, shank support ribs attached to the adapter lower grilles, head, mounted on the upper ends of tubular channels, and the elements ensuring the fixation of the fuel elements at the bottom of the grate according to the invention for fastening a fuel element in the hole of the lower grille, made in the form of a truncated lower stub with total the length of the middle and lower mounting parts not exceeding 1/2 of the thickness of the lower grille, mounting part of the lower stub coaxial its cylindrical middle part at the end made blind hole with the formation of an annular wall with a thickness sufficient to expanding into the larger hole on the bottom that is CA bottom of the lattice to a depth below the protruding portion of the annular wall of the lower end of the bracket into the hole of larger diameter lower grilles, when the fastener lower plug made expanding ring wall in the specified hole of larger diameter.

In this fixture the lower plug of a fuel rod at the bottom grate and the bottom stub of the channels of the guides increases operational reliability of the fuel assemblies in the reactor core of a nuclear reactor by eliminating the backlash of the lower plug in the lower grid by expanding holes in the bottom of the lattice, respectively, will eliminate the vibration of the fuel rod, will increase the reliability of fastening, to preclude axial displacement of the fuel rod up and unpredictable vibration. The proposed elements of fastening of the bottom stub of the fuel elements in the lower grille reduces the cost of production through technological operations and reduced volume fraction of structural material by performing a shortened bottom plugs TVEL, channels, guides and weight loss lower gratings due to make the holes larger diameter for expanding them in the lower ends of the plugs.

The drawings show a fuel Assembly of a nuclear reactor, where:

figure 1 - General view of the fuel Assembly;

figure 2 is a fragment of the lower mounting bracket into the lower grille to flaring;

figure 3 is a fragment of the lower mounting bracket into the bottom grate after flaring.

A fuel Assembly for nuclear is eactor, mainly VVER-type, includes a bundle of fuel elements 1 mounted in the frame of the grid spacers 2, mounted on the tubular channels 3, secured together with heat-generating elements 1 lower plug 4 in the lower grating 5 with adapter, shank 6 with a support ribs attached to the adapter bottom grating 5, the head 7 mounted on the upper ends of the tubular channels 3, and the elements ensuring the fixation of the fuel elements 1 in the lower grille 5.

The elements that provide anchorage of the fuel element 1 in the hole 8 of the bottom grating 5, made in the form of a truncated lower stub 4 with a total length of an average 9 and the lower fixing parts not exceeding 1/2 of the thickness “H” of the lower grating 5.

In the mounting part of the lower plug 4 coaxially its cylindrical middle part 9 on the end a blind hole 10 with the formation of the annular wall 11 with a thickness sufficient for its expanding in the hole 12 has a larger diameter on the bottom end of the lower grating 5 at a depth below the protruding portion of the annular wall 11 of the lower end of the insert hole 12 of larger diameter lower grating 5. Fastening the lower plug 4 made by expanding (randombly) annular wall 11 in the specified hole 12 of large diameter. Joe the governing Assembly assemble as follows. Assemble the frame of the grid spacers 2 on tubular channels 3 with the lower bars 5. Lower grille 5 must be prepared for Assembly fuel Assembly, which on each hole 8 with the lower end of the lower grating 5 must be completed holes 12 of larger diameter, and the lower plug 4 on the fuel Rods 1 should be on the lower ends of the blind holes 10, coaxial cylindrical middle part 9, and having an annular wall 11, which resultatives (rastorgovyvalsja) in the hole 12 of the lower grating 5.

To lower the grate 5 is fixed to the shank 6, and the upper ends of the tubular channels 3 fixed head 7.

A fuel Assembly of a nuclear reactor, mainly type reactors, including the bundle of fuel elements installed in the frame of the grid spacers mounted on the tubular channels fastened together with fuel elements of the lower plugs in the bottom grid with adapter, shank support ribs attached to the adapter lower grilles, head, mounted on the upper ends of tubular channels, and the elements ensuring the fixation of the fuel elements in the lower grille, characterized in that the elements that provide anchorage of the fuel element in the hole of the bottom grating made is in the form of a truncated lower stub with a total length of the middle and lower mounting part not exceeding 1/2 of the thickness of the lower grille, mounting part of the lower stub coaxial its cylindrical middle part at the end made blind hole with the formation of an annular wall with a thickness sufficient to expanding into the larger hole on the bottom edge of the lower grille to a depth below the protruding portion of the annular wall of the lower end of the bracket into the hole of larger diameter lower grilles, while the fasteners of the lower stub carried out by the expanding ring wall in the specified hole of larger diameter.



 

Same patents:

FIELD: nuclear power engineering.

SUBSTANCE: proposed fuel assembly designed for use in water-moderated water-cooled reactors, primarily those of VVER-1000 type, is characterized in that its uranium dioxide mass in bundle, outer and inner diameters of fuel element cladding are 436.24 to 561.18 kg, 7.00 · 10-3 to 7.50 · 10-3 m, and 5.94 · 10-3 to 6.36 · 10-3 m, respectively, for bundle of 468 to 510 fuel elements, or uranium dioxide mass in bundle, outer and inner diameters of fuel element cladding are 451.37 to 582.17 kg, 7.60 · 10-3 to 8.30 · 10-3 m, and 6.45 · 10-3 to 7.04 · 10-3 m, respectively, for bundle of 390 to 432 fuel elements, or uranium dioxide mass in bundle, outer and inner diameters of fuel element cladding are 442.22 to 544.12 kg, 8.30 · 10-3 to 8.79 · 10-3 m, and 7.04 · 10-3 to 7.46 · 10-3 m, respectively, for bundle of 331 to 367 fuel elements, water-uranium ratio of subchannel being chosen between 1.27 and 1.83.

EFFECT: reduced linear heat loads and fuel element depressurization probability; enlarged reactor power control range, improved fuel utilization.

4 cl, 11 dwg

FIELD: nuclear power engineering.

SUBSTANCE: proposed fuel assembly designed for use in water-moderated water-cooled reactors, primarily those of VVER-1000 type, is characterized in that its uranium dioxide mass in bundle, outer and inner diameters of fuel element cladding are 436.24 to 561.18 kg, 7.00 · 10-3 to 7.50 · 10-3 m, and 5.94 · 10-3 to 6.36 · 10-3 m, respectively, for bundle of 468 to 510 fuel elements, or uranium dioxide mass in bundle, outer and inner diameters of fuel element cladding are 451.37 to 582.17 kg, 7.60 · 10-3 to 8.30 · 10-3 m, and 6.45 · 10-3 to 7.04 · 10-3 m, respectively, for bundle of 390 to 432 fuel elements, or uranium dioxide mass in bundle, outer and inner diameters of fuel element cladding are 442.22 to 544.12 kg, 8.30 · 10-3 to 8.79 · 10-3 m, and 7.04 · 10-3 to 7.46 · 10-3 m, respectively, for bundle of 331 to 367 fuel elements, water-uranium ratio of subchannel being chosen between 1.27 and 1.83.

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The invention relates to fuel assemblies used for dual functions: energy production and regulation of the neutron flux in water-cooled nuclear power reactors, especially in nuclear reactors VVER-440

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EFFECT: higher efficiency.

4 cl, 1 dwg

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