RU2305333C1 - Rod billet for nuclear-reactor ceramic fuel core - Google Patents

Abstract

FIELD: nuclear power engineering.

SUBSTANCE: proposed rod billet designed for use in compacting nuclear-reactor fuel core rods has zirconium alloy tube, nuclear fuel and matrix material fill, as well as two cylindrical plugs with annular drillings for localizing excess solder placed in the form of paste. Plugs are installed in tube in guaranteed space relation to the latter. Cylindrical surface of each plug has two annular drillings spaced 5 to 7 mm apart; drillings external with respect to fill are filled with paste. Provision is made for combining degassing and sealing processes by raising temperature directly upon completion of degassing operation.

EFFECT: enhanced productivity and reduced cost of process equipment and rigging.

3 cl, 2 dwg

Description

1. The technical field to which the invention relates.

The invention relates to the field of nuclear energy, in particular to the design of the workpiece used in the pressing of the fuel core rods of cermet fuel elements (fuel elements) of nuclear reactors for various purposes.

2. The level of technology

One of the areas in nuclear energy is the use of fuel rods in which cermet fuel cores are drawn from rods (see, for example, Fedik II, Gavrilin SS and others. A new generation of microfuel fuel rods for VVER. - M. : Atomic Energy, 2004, vol. 96, issue 4, p. 280).

For the manufacture of such a rod, a billet made in the form of a pipe made of zirconium alloy can be used (see, for example, Solonin MI, Bibilashvili Yu.K. et al. Zirconium-niobium alloys for cladding of fuel rods and fuel assemblies of power reactors and WWER-type installations and RBMK, Selected Works of VNIINM, Federal State Unitary Enterprise VNIINM, Moscow, v. 1, pp. 65-69), filled with a backfill of nuclear fuel powders and matrix material and closed at the ends with two cylindrical plugs (see, for example, A. Samoilov, Volkov BC, Solonin MI The fuel elements of nuclear reactors. - M .: nergoatomizdat, 1996, p.217).

This design of the workpiece involves sealing a pipe cavity filled with backfill of nuclear fuel powders and matrix material by fusion welding of plugs with a pipe at normal temperature (see, for example, Samoilov A.G., Volkov VS, Solonin M.I. Nuclear fuel elements Reactors. - M .: Energoatomizdat, 1996, p. 216). Since before the workpiece is sealed, degassing of the powder backfill by holding it in a vacuum at high temperature must be carried out, the need arises for the use of specialized technological equipment and equipment to cool the workpieces, lock them and move them to the welding position and conduct the welding itself.

The disadvantage of the use of the workpiece is the high cost of manufacturing the rod, which can be reduced by reducing the amount of expensive technological equipment and equipment.

With the proposed technical solution, this device matches the following essential features:

- a pipe made of zirconium alloy;

- filling in powders of nuclear fuel and matrix material;

- two cylindrical caps.

Also known is a preform consisting of a pipe made of a zirconium alloy, backfill of nuclear fuel powders and matrix material, and two cylindrical plugs with annular grooves to localize the excess solder laid on the edges of the joint in the form of a paste (see, for example, Samoylov A.G. , Volkov BC, Solonin M.I. Fuel elements of nuclear reactors. - M.: Energoatomizdat, 1996, p.231-232). This design involves the operation of degassing backfill before laying the solder, since it blocks the path of the exit of gases. In this case, the laying of solder should be carried out in vacuum at a temperature lowered relative to the degassing mode.

The disadvantage of using the workpiece is that the implementation of the considered operations requires significant interoperational time and the use of specialized technological equipment. These two factors determine the productivity and cost of manufacturing the rods.

This device coincides with the proposed solution in the following essential respects:

- a pipe made of zirconium alloy,

- filling in powders of nuclear fuel and matrix material,

- two cylindrical plugs,

- annular grooves on the plugs to localize excess solder,

- solder laid in the form of a paste.

In terms of the set of essential features, the last device is closest to the proposed device and is selected as a prototype.

3. The invention

The proposed billet of the core core of the cermet fuel element of a nuclear reactor consists of a pipe made of zirconium alloy, a bed of powders of nuclear fuel and matrix material, two cylindrical plugs with annular grooves to localize the excess solder laid in the form of a paste, and the plugs are installed in a pipe with a guaranteed a gap, on the cylindrical surface of each plug are made two annular grooves at a distance of 5-7 mm from each other, and external relative to the backfill grooves filled with paste.

This device differs from the prototype in that the plugs are installed in the pipe with a guaranteed gap, on the cylindrical surface of each plug two ring grooves are made at a distance of 5-7 mm from each other, and the grooves external to the filling are filled with paste.

This difference provides an increase in productivity in the production of rods and reduces the cost of technological equipment and tooling due to the possibility of combining the technological positions of degassing and sealing and sealing by raising the temperature immediately after the degassing operation.

To clarify this design, a blank is proposed in which the plugs are made of zirconium alloy, and the paste contains a mixture of copper and zirconium powders in a mass ratio of (0.17-0.25) :( 0.83-0.75).

The degassing operation of materials in such a preform, including the decomposition and removal of the paste binder, is completed at a maximum temperature of 800-850 ° C with the release of gases through a guaranteed gap between the pipe and the plugs, and sealing is carried out by raising the temperature to 1000 ° C. At this temperature, the solid components of the paste are converted into the liquid phase of the eutectic composition, which, under the action of capillary forces and good wettability of the surfaces, is drawn into the gap between the pipe and the plug, which ensures sealing.

Also, to clarify the design of the workpiece, it is proposed that the plugs be made of steel and the use of a paste containing a mixture of powders of copper, zirconium and iron in a mass ratio of (0.11-0.13) :( 0.78-0.74) :( 0.11- 0.13). The possibility of using steel plugs instead of zirconium in this design gives a significant economic effect (the cost of zirconium is an order of magnitude higher than the cost of steel).

4. The list of drawings

Figure 1. - drawing of the core blank of the fuel core:

1 - pipe made of zirconium alloy;

2 - filling powders of nuclear fuel and matrix material;

3 - plugs;

4 - grooves for localization of excess solder;

5 - grooves filled with solder in the form of a paste.

Figure 2 is a photograph of a thin section soldered connection:

1 - a stub;

2 - pipe;

3 - groove, originally filled with paste;

4 - groove for localization of excess solder;

5 - zone solder joints.

5. Information confirming the possibility of carrying out the invention

The possibility of carrying out the invention is illustrated by a specific example. Figure 1 shows a drawing of a billet consisting of a zirconium pipe 1, a bed of powders of nuclear fuel and matrix material 2, two cylindrical plugs of zirconium 3. On the plugs are made annular grooves 4 for localizing excess solder and annular grooves 5 filled with solder in the form of paste on a polyvinyl acetate bond containing a mixture of powders of copper and zirconium in a mass ratio of 0.22: 0.78. Fixing the plugs in the pipe is carried out, for example, using beetles in the zones of the grooves 4 (not shown in the drawing). To ensure a guaranteed gap between the pipe and plugs of, for example, 100 μm, the plugs are 200 mm smaller in nominal diameter than the nominal inner diameter of the pipe, and the tolerance on the plug diameter is chosen non-positive and non-negative for the pipe inner diameter.

Figure 2 shows a photograph of a thin section of the soldered joint of plug 1 with pipe 2. From a groove 3, originally filled with paste, at a soldering temperature, the eutectic composition of the liquid phase of 22 wt.% Cu - 78 wt.% Zr stretched into the gap between the pipe and the plug and stopped in groove 4, where the excess of solder was localized. The soldered joint zone 5 as a result of the mutual diffusion of copper and zirconium is converted into a structure without transition boundaries, which determines the high-quality sealing.

Claims (3)

1. The core of the fuel core of the cermet fuel element of the nuclear reactor, consisting of a pipe made of zirconium alloy, a powder of nuclear fuel and matrix material, two cylindrical plugs with annular grooves to localize the excess solder laid in the form of a paste, characterized in that the plug installed in a pipe with a guaranteed gap, on the cylindrical surface of each plug are made two annular grooves at a distance of 5-7 mm from each other, and the external relative to ypki grooves filled with paste. 2. The workpiece according to claim 1, characterized in that the plugs are made of zirconium alloy, and the paste contains a mixture of powders of copper and zirconium in a mass ratio (0.17-0.25) :( 0.83-0.75). 3. The workpiece according to claim 1, characterized in that the plugs are made of steel, and the paste contains a mixture of powders of copper, zirconium and iron in a mass ratio (0.11-0.13) :( 0.78-0.74): (0.11-0.13).

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