A method of manufacturing a three-layer ribbed tubular fuel elements and a matrix for carrying out the method

 

(57) Abstract:

Usage: in the field of nuclear energy and may find application in the manufacture of three-layer ribbed tubular fuel elements in the core of the dispersion type. The inventive method includes the operations of obtaining a mixture of fine powders for the manufacture of fuel cladding by powder metallurgy by mixing powders of starting materials in the presence of a liquid plasticizer, cold pressing into the material of the core using a plasticizer, present in the mixture as a lubricant. When this liquid plasticizer is introduced into the mixture during the mixing process in individual portions in the form of spray and mixture is produced in a period of time sufficient to obtain a uniform distribution of fissile phase in non-dividing. Then perform hot pressing - calibration of the core to the desired density and size to use as lubrication products of the pyrolytic decomposition of organic matter. In the matrix for implementing the method containing lead-conical portion forming the edges of the pie sites, evenly distributed around the circumference of the matrix and education is implementing the grooves, sector sites are made so that the sides of each form an angle of less than 180o. Moreover, the sides of the adjacent sector platforms converge at a point on the outer diameter of lead-in cone. 2 S. and 2 C.p. f-crystals, 8 ill.

Izobretenie relates to nuclear power and may find application in the manufacture of three-layer ribbed tubular fuel elements (Fe) core dispersion type. Fuel elements of this type are in the form of tubes of circular or polygonal cross-section consisting of an inner layer (core) and bilateral protective shell of corrosion-resistant material, such as aluminum alloy. Operating conditions, the protective sheath on the inside of the tubes have smooth, and has external longitudinal spacer ribs. The inner and outer layers of the shell, connecting beyond the ends of the core, form a built-tight coating.

The core module is manufactured by powder metallurgy from a mixture of dispersed uranium dioxide (fissile material) aluminium powder (matrix material). Tubular fuel elements produced by hot pressing procurement team, consisting of three concentrarsi nuclear energy for the manufacture of cores of the fuel rods dispersed type used for example, uranium dioxide, and as a continuous matrix powder of aluminum, which is subjected to mixing in the presence of an organic plasticizer. The resulting mixture is subjected to cold pressing into the material of the core. When it particles of fissionable material is uranium dioxide should be evenly placed in the volume of the aluminum matrix, without breaking its continuity, without forming local clusters and depleted zones.

The plasticizer present in the mixture, is also a lubricant during the extrusion of billets.

To obtain a solid billet core, the latter after cold pressing is subjected to thermal sintering in vacuum, in which the plasticizer decomposes and evaporates through the pores of the workpiece, and the particles are extruded aluminum are sintered, forming a metal matrix.

After ochazuke and sintering the porous preform core to give it the specified density and dimensions are subjected to hot pressing calibration. Then, a metal sleeve together with the billet shell is completed with the team in the blank, from which the hot pressing through the matrix receive a three-layer tubular fuel elements. The closest of those who widelyused elements and the matrix for the implementation of this method [1 and 2]

A method of manufacturing a three-layered tubular ribbed rods (prototype) has a similar operation as the operation described above, and the mold Fig. 7 [1, c. 313] matrix for pressing ribbed three-layer fuel rods, [2, Fig. 18.10, S. 418] billet for extrusion of three-layer fuel rods [2, Fig. 18.13, S. 420] for the best display summarized in Fig.1 in a device for molding three-layer ribbed rods, and defects pressing[2, Fig. 18.7, C. 416] shown in Fig.2.

Device for pressing a three-layer ribbed rods includes sintered bushing 1, the inner sleeve 2 and the outer sleeve 3 made of aluminum alloy, the upper cover 4 and the lower cover 5 made of aluminum. The workpiece is placed in a heated container 6 from which the plunger 7 through matrix 8 produce the pressing of a fuel rod.

Matrix 8 (Fig.1) has a conical lead-in surface 9 channels 10 to form ribs. Pie pad 11 is formed with the axis of the matrix angle which is smaller than the angle b, the half angle of the lead-in cone. Between the pie sites located longitudinal grooves 12 forming the ribs, and calibrating the belt 13.

In the manufacture of fuel elements by the method of powder metallurgy in the powder. However, when mixing two dissimilar powders due to the difference in specific weights (aluminum powder 2.7 g/cm, and the uranium dioxide 10,0-10,5 g/cm) occurs the phenomenon of segregation, a kind of "floating" on the surface of the lungs powders and aspirations heavy powders "drown" in the charge.

These phenomena to some extent be eliminated by pouring in the mixture of plasticizer from alcohol-oleic acid mixture in a ratio of 3-5% by weight of the mixture and mixing them together.

However, inkjet filling in charge of the plasticizer has a negative side clumping fine phase uranium dioxide in a fairly large conglomerates, which can lead to uneven dispersion of fissile phase in dividing the matrix, reducing the quality of the fuel rod and the yield of products.

In the process of hot calibration on the surface of the billet core and the mold put a layer of water-graphite lubrication and carry out hot calibration. Water, included in the water-graphite lubricants designed for the uniform distribution on the workpiece surface of the core and the mold penetrates into the pores of the preform core, it hydrates the aluminum matrix (non-dividing phase) that calls the ode fit.

The disadvantage of three-layer coupling the workpiece (Fig.1) is the presence of a large number of prefabricated elements: fuel and core 1, the outer shell (sleeve) 3, the inner shell (sleeve) 2 and two plugs 4 and 5 on the ends, that does not preclude the ingress of lubricant through the gaps between the shells 2 and 3 and covers 4 and 5 directly on the fuel core 1.

The ingress of water from the water-graphite grease applied during the extrusion, the aluminum matrix of the fuel core will cause its hydration and formation of gas bubbles, excluding the clutch shell with the core, which will reduce the quality and yield of the fuel rods. A large number of components for a three-layer preform will complicate the Assembly will require fixtures for Assembly and sealing both ends, which will reduce the output of the fuel rods.

In the process of hot pressing such blanks in a three-layer pipe at the ends of the core distortion in the form of thickening and nodules (Fig.2), which cause thinning of the skin in areas of education end of the defect core (a and b). During subsequent calibration extruded multilayer pipes by drawing places the end of the defects occurs breakage or stir about the process of hot pressing a three-layer preform through matrix 8 (Fig. 1) with grooves 12 for the formation of the ribs is not achieved the uniformity of thickness of the cladding layer in the consequence of the fact that the formation of the ribs is not with the entire surface of the cladding layer of the workpiece, but only at the expense of material collected from areas of sector areas 11, whereas the material in intersectoral platforms in the formation of the ribs is not involved and the thickness of the cladding layer on the circumference of a fuel rod is obtained variable, i.e., thickened in the intercostal spaces and thinned near ribs 14 (Fig.2).

The uneven thickness of the cladding layer will lead to a breach of heat removal during operation of a fuel rod in a nuclear reactor, i.e., the maximum heat removal will occur in places thinning cladding layer and Vice versa in places thickening of the cladding layer (ribs and intercostal part) heat removal will be less than that can lead to burnout shell of a fuel rod, the pressure loss of the fuel rod in a nuclear reactor, i.e., the execution of such low quality fuel rods reduces the yield.

An object of the invention is to improve the quality of a fuel rod and yield. This task is achieved in that in the method of manufacturing a three-layered tubular ribbed rods and the matrix for the implementation of this spotboy metallurgy by mixing powders of starting materials, for example, uranium dioxide powder with a powder of aluminum metal in the presence of a liquid plasticizer, cold pressing into the material of the core using a plasticizer, present in the mixture as a lubricant, thermal sintering in a dynamic vacuum billet core with removing plasticizer from the pores of the preform core, hot pressing, calibration blanks core to the desired density and size with the use of lubrication on the surface of the mold and preform core, placing a workpiece in the shell Assembly for pressing, lubrication of the three-layer Assembly and the mold and hot pressed in a die with grooves for the edges in the three-layer tubular fuel rod with longitudinal ribs;

According to the invention the liquid plasticizer is introduced into the mixture during the mixing process in individual portions in the form of spray and mixture is produced in a period of time sufficient to obtain the dimension of the distribution of fissile phase in non-dividing. As lubrication during hot pressing calibration of the core to the desired density and size use organic substance with temperature pyrolytic decomposition equal to the temperature calibration angry longitudinal grooves with the widening in the upper part and the inner and outer chamfer on the bottom. The manufacture of the shell is carried out by execution in the pipe-casing annular groove, the shape of the core with the response of the longitudinal inner edges, beveling the bottom of the back edge angle that is identical to the lead-in cone of the matrix, place the core in the annular groove of the shell, the resulting Assembly being calibrated, is heated to a temperature greater than the temperature of the subsequent heat treatments, seal the open end of the Assembly by welding the annular stub to the end of the shell, combine the slots of the core Assembly with rapoorteuse grooves matrix and perform hot pressing of three-layer fuel rod with external longitudinal ribs.

Other differences in the method of manufacturing a finned tubular fuel elements are:

1) use as an organic substance polyethylene rubber;

2) use as a protective layer on the surface of a core of aluminium foil with a drawing of her usual water-graphite lubricants;

3) using the matrix for the manufacture of multilayer cylindrical fuel rods with longitudinal ribs by the method of plastic deformation, containing conical lead-in portion with the forming edges of the sector areas, is equal to the lead angle of the cone, and calibrating the belt with longitudinal grooves, characterized in that the sides of each form an angle of less than 180oand the side of the neighboring sector sites converge to a point on the outer diameter of lead-in cone.

Introduction to mixed fissile and non-fissile phase of the plasticizer in the form of aerosols will ensure uniformity of fine uranium dioxide in an aluminum powder, to eliminate the phenomenon of clumping dioxide in the conglomerates, to improve the quality of the fuel rods and the yield.

Use as lubrication products of the pyrolytic decomposition of the organic material at a temperature equal to the temperature calibration of the core, prevent ingress of water into the porous preform, to exclude hydrating the aluminum phase, and consequently to eliminate swelling and defects on the finished fuel rods that will improve their quality and yield.

Use as a protective layer of aluminum foil, in which is placed the core in front of the hot calibration, and application of water-graphite grease the foil will prevent ingress of water into the porous preform, hydrating the aluminum phase and consequently to improve the quality and the yield-per is SkyCity appearance on the bottom by pressing the three-layer fuel rod swelling of the core and utoncennij shell, that will improve the quality and the yield of fuel elements.

Running in the shell ring groove will reduce the number of parts in Assembly with five (core, inner sleeve, outer sleeve, top cap, bottom cap) to three (core, shell, stub); to avoid the grease on the core during pressing, which could take place in the famous three-layer Assembly and to improve the quality of extruded rods and the yield.

Performing on the outer part of the core longitudinal grooves and the return of ribs on the inner surface of the annular groove and the orientation of the alignment grooves of the core rapoorteuse the grooves of the matrix will allow you to get under each rib shell thinning core that will prevent overheating and burnout of the shell in the zone of the ribs in the process in the channel of a nuclear reactor, and the execution of the work piece core of the broadening of each groove in the upper part will be excluded from the pressing chipped corners of the slots of the core and moving these chips at the end of the shell, which increases the quality and yield of the fuel rods.

In the process of pressing sectoral platform for forming a lead-in cone of the proposed matrix create a local ousia ribs. The shape and dimensions of the sector areas provide the necessary distribution of the metal billet shell running on the formation of ribs, and a shell with a uniform thickness in the intercostal space, which will increase the quality and the yield of fuel elements.

In Fig.1 shows a device for pressing a three-layer tube of a fuel rod according to the method, adopted as the prototype of Fig.2 the image of a fuel rod received under the terms of the prototype, and defects in extrusion of Fig. 3 procurement cermet core, performed by the proposed method, Fig.4 billet shell of aluminum alloy and end cap of Fig. 5 team billet for hot extrusion of tubular fuel rod of Fig.6 matrix for pressing of a fuel rod according to the proposed method, Fig. 7 extruded three-layer tubular fuel rod of circular cross section with ribs on the outside of the shell; Fig.8 extruded fuel element after forming in hex pipe.

A method of manufacturing a three-layered tubular fuel elements is as follows.

The uranium dioxide, sintered to a density of 10.0 to 10.5 g/cm, crushed and scattered to fraction (40 to 160 μm) are mixed in the mixer with aluminium powder booleanova mixture in an amount of 3-5% by weight of the charge injected into the mixing process in individual portions in the form of aerosols.

To obtain a solid billet cores, the latter after cold pressing are subjected to thermal sintering in a dynamic vacuum, where the plasticizer is removed from the pores of the workpiece, the porosity of the latter reaches 15-18%

After ochazuke and sintering the porous preform core to give it the specified density and size were subjected to hot pressing calibration with a dry lubricant carbon and pyrolytic carbon formed on the workpiece of the core and the surface of the mold with a thin layer in captaim flame of organic matter placed in the mold, using a heating temperature of the mold for thermal decomposition of organic matter.

Example 1. As organic matter used granulated rubber or polyethylene in a ratio of 5-10% by volume of the workpiece. The mold was heated to 440-460oC and pyrolytic carbon thin layer was deposited on the surface of the billet core and the mold and used as a lubricant in the calibration pressure of 3.5-4.0 t/see

Example 2. Billet core I wrapped in aluminum foil and calibration was carried out under a pressure of 3.5-4.0 t/cm at a temperature of 440-460oC in her parts perform chamfer 16 and 17 on the outer and inner surfaces. In addition, the core 15 perform longitudinal exterior grooves 18. Manufacturer of shell 19 (Fig.4) carry out, for example by the method of backward extrusion of the annular groove 20, is identical to the shape of the bottom of the lower end face of the core, with the response, the longitudinal ribs 21, the annular plug 22 and the beveling of the lower blind end 23 at an angle identical to the lead-in cone of the matrix. Each groove 18 of the core 15 (Fig.5) perform the broadening 24 in the upper part.

National procurement completed in the following order (Fig.5). In the annular groove 20 of the shell 19 installing the fuel core 15 so that the grooves 18 coincides with the longitudinal edges 21 of the groove 20, and set the cover 22. The resulting billet gauge, heated to a temperature greater than the temperature of the subsequent heat treatments 540-550oC, maintained at these temperatures 5-20 min and seal the open end of the welding stub 22 with the casing 19. When calibrating the broadening 24 is filled with the fuel material, excluding chips and transfer them to a blank portion of the fuel element.

For the implementation of the method of manufacturing a three-layered tubular rods were used matrix (Fig.6), consisting of a body 25 having a conical lead-in surface 26, calibraiton site 29, forming with the vertical axis of the angle a lesser half of the lead angle b Angle solution sectoral areas g made less than 180oand divides forming lead-conical surface portion, the number of which is equal to the number of grooves 28, matrix 25.

In the manufacture of laminated rods with longitudinal ribs multilayer Assembly (Fig. 5) Orient, combining grooves 18 of the core rapoorteuse the grooves 28 of the matrix 25, and perform hot pressing of tubular fuel elements (Fig. 7), consisting of cermet core 30, the inner smooth shell 31 and the outer protective layer of the shell 32, the surface of which is formed spacer ribs 33. Tubular fuel rod of circular cross section may be formed in a polyhedron by drawing it through calibrating the matrix, for example in a hexagonal tube (Fig.8).

A method of manufacturing a source of parts, prefabricated blanks and hot pressing of a three-layer, tubular, finned fuel elements using the updated matrix provides a uniform distribution of uranium dioxide in the working volume of the core, the geometric stability of dimensions shell height and cross sections, swelling and flows along the length of the core material of the core towards the edges and ensure that any given measure of core in the areas of the ribs.

The effectiveness of the method of manufacturing a tubular ribbed rods confirmed positive test results of full-scale samples in a nuclear research reactor.

1. A method of manufacturing a three-layer ribbed tubular fuel elements (FE), which includes the operations of obtaining a mixture of fine powders for the manufacture of Fuel cladding by powder metallurgy by mixing powders of the starting materials, for example powder of uranium dioxide powder of metallic aluminum in the presence of liquid plasticizer, cold pressing into the material of the core using a plasticizer, present in the mixture as a lubricant, thermal sintering in a dynamic vacuum billet core with removing plasticizer from the pores of the preform core, hot pressing-calibration blanks core to the desired density and size with the use of lubrication on the surface of the mold and preform core, accommodation billet core in the shell Assembly for pressing, lubrication of the three-layer Assembly and the mold and hot pressed in a die with grooves for the edges in the three-layer tubular fuel rod with longitudinal ribs, characterized t and the mixture produced in the course of time, sufficient to obtain a uniform distribution of fissile phase in non-dividing and as a lubricant during hot pressing calibration of the core to the desired density and size use organic substance with temperature pyrolytic decomposition equal to the calibration temperature of the core, and before placing the core in the shell Assembly for pressing on the outer surface carry out longitudinal grooves with the widening in the upper part and the inner and outer chamfer on the bottom, making the shell is carried out by execution in the pipe-casing annular groove, the shape of the core with the response of the longitudinal inner edges, beveling the bottom of the back edge angle, identical lead-in cone of the matrix, place the core in the annular groove of the shell, the resulting Assembly being calibrated, is heated to a temperature greater than the temperature of the subsequent heat treatments, seal the open end of the Assembly by welding the annular stub end of the shell, combine the slots of the core Assembly with rapoorteuse grooves matrix and perform hot pressing of three-layer fuel rod with external longitudinal ribs.

2. The method according to PP.1 and 2, otlichayuschimisya fact, in the process of hot calibration core as the protective layer surface using aluminum foil with a drawing of her water-graphite lubricants.

4. Matrix for the manufacture of three-layer ribbed tubular fuel elements containing lead-conical portion forming ribs sector sites, evenly distributed around the circumference of the matrix and forming with the longitudinal axis of the matrix an angle less half of the lead angle of the cone, and calibrating the belt with longitudinal grooves, characterized in that sector of the site is made so that the sides of each form an angle of less than 180oand the side of the neighboring sector platforms converge at a point on the outer diameter of lead-in cone.

 

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