Method for hot isostatic pressing cermet rod of nuclear reactor fuel element

FIELD: physics, nuclear.

SUBSTANCE: invention relates to nuclear power engineering and specifically to methods of making cermet rods of fuel cores of fuel elements of nuclear reactors for different purposes. A workpiece is put into a container. Working medium in form of solid glass is put into the container and the container with the workpiece and the working medium is heated to pressing temperature. The container is put into a press mould and moulding force is applied by increasing pressure of the working medium while moving the moulding die. In the proposed method the working medium is in form of a briquette. The briquette is placed at the bottom of the container. The workpiece is put on top of the briquette. The container with the workpiece and the working medium is heated outside the press mould until the workpiece is immersed in the working medium.

EFFECT: reduced probability of formation of voids, transfer of pressure onto the moulded workpiece becomes more uniform, increased output of the suitable products.

 

1. The technical field to which the invention relates.

The invention relates to the field of nuclear energy, in particular, to methods for producing kermeth rods of the fuel cores of fuel elements (Fe) of nuclear reactors for various purposes.

2. The level of technology

One of the areas in nuclear power is the use of fuel in which the fuel cores recruited from kermeth rods (see, for example, I.I. Fedik, Gavrilin S. and other New generation of fuel-based micro-fuel for VVER, M.: Nuclear energy, 2004, t 4 s), and the rods capsulised in the zirconium alloy cladding (see, for example, Solonin M.I., Bibilashvili J.K. and other Zirconium-niobium alloys for fuel cladding and fuel Assembly power reactors and plants of VVER and RBMK reactors, Selected works VNIINM, M.: FSUE VNIINM, vol. 1, p.65-69).

As the blanks in the manufacture of such kermeth rods used zirconium tube filled with powder of nuclear fuel and closed with plugs (see, for example, Gavrilin S., Deniskin V.P. Leonov A.V., I.I. Fedik Billet fuel rod core kermetnogo fuel element of a nuclear reactor, RF Patent № 2305333 from 15.03.2006, publ. 27.08.2007, bull. No. 24). After encapsulation fuel zirconium shell compression is just the Cai and the seal fuel by isostatic pressing (see, for example, Gavrilin S., Permyakov, L.N., Chernikov A.S. Composite material for fuel cores of the dispersion fuel elements, RF Patent № 2139581 from 23.06.98, publ. 10.10.99, bull. No. 28; Gavrilin S., Deniskin V.P. Leonov A.V., I.I. Fedik a Method of manufacturing kermetnogo fuel rod core fuel element of a nuclear reactor, RF Patent № 2305334 from 15.03.2006, publ. 27.08.2007, bull. No. 24).

Isostatic transfer pressure in the pressing of objects of the specified type can be done in different ways. There is a method of hot isostatic pressing billet fuel rod core kermetnogo of a fuel rod of a nuclear reactor, in which the workpiece is placed in the container, served in a container of gas, the working environment, through which is passed the pressure on the workpiece, heat the container and the working environment to a temperature of the pressing and maintain the workpiece under pressure required time (see, for example, Samoilov A.G., V.S. Volkov, M. Solonin. Fuel elements for nuclear reactors", M.: Energoatomizdat, 1996, s). For pressing the specified workpiece at a temperature of about 1000°C is required gas pressure of at least 100 MPa at the time of pressing 1-1,5 hours. The provision of such pressure gas at high temperature and with considerable output is solved by creating a complex PROIZVODSTVENNO the equipment, time-consuming and strict regulation of work of the staff from the point of view of the implementation of safety rules.

With the proposed method this method is the same as the operation of placing the billet in the container, the supply in the container of the working environment for the transmission of pressure to the workpiece, heating the container and the working environment to a temperature of extrusion and exposure of the workpiece under pressure.

There is also known a method of hot isostatic pressing billet fuel rod core kermetnogo of a fuel rod of a nuclear reactor, in which the workpiece is heated to a temperature pressing, place the workpiece in the container, and the gaps between the workpiece and the walls of the container, fill the pre-molten working medium, which use glass, place the container in the mold press and apply a pressing force to increase the pressure of the working medium during movement of the punch press (see, for example, V.I. Ural, V.S. Plakhotin and other metal Deformation by high pressure fluid, M.: metallurgy, 1976, p.390).

Since the molten glass has a high viscosity, in this way the probability of formation in the melt of gas bubbles, causing unevenness of the applied pressure on the surface of the compression zagotovka and its curvature. This reduces the yield of blanks.

With the proposed method this method is the same as for the following essential features:

the workpiece is heated to a temperature of the pressing out of the press,

- place the workpiece in the container

- fill the working environment, in which they use glass, the gap between the billet and the container wall,

- place the container in the mold press,

- apply a pressing force to increase the pressure of the working medium during movement of the punch press.

There is also known a method of hot isostatic pressing billet fuel rod core kermetnogo of a fuel rod of a nuclear reactor, in which the workpiece is placed in the container, fill the gaps between the billet and the container wall of the working medium in the solid state, which uses crushed glass, carry out a degassing container with the workpiece and the working environment in the vacuum, place the container in the mold press, heat the container in the mold to a temperature of the pressing and apply the pressing force to increase the pressure of the working medium during movement of the punch press (see, for example, Karl M., Vincent C., Microstructurally toughened metal matrix composite article and method of making same, US Pat. No. 4885212, Dec.5, 1989).

The disadvantage of this method, as the previous is high verojatnost the education in the molten glass, closed cavities, the elimination of which is difficult due to high viscosity of the melt. Such cavity, unpredictable United with each other, lead to uneven distribution of pressure over the surface of the workpiece and, consequently, to its curvature. This reduces the yield of blanks. In addition, since the melting of the crushed glass is significant shrinkage, for the implementation of this method requires increased container size, which, in turn, leads to an increase in energy costs to heat press.

With the proposed method this method is the same as for the following essential features:

- place the workpiece in the container

in a container placed in a working environment in which use of glass in the solid state,

- place the container in the mold press,

- heat the container with the workpiece and the working environment to a temperature of extrusion,

- apply a pressing force to increase the pressure of the working medium during movement of the punch press.

The last method of hot isostatic pressing billet fuel rod core kermetnogo of a fuel rod of a nuclear reactor in essential characteristics closest to the proposed and selected as a prototype.

3. The invention

The offers is way hot hydro-extrusion billet fuel rod core kermetnogo of a fuel rod of a nuclear reactor, namely, that the workpiece is placed in the container, the container is placed in a working environment, in the form of briquettes glass, put briquettes on the bottom of the container, heating the container with the workpiece and the working environment prior to immersion of the workpiece in the working environment, place the container in the mold press and apply a pressing force to increase the pressure of the working medium during movement of the punch press. Unlike the prototype, the proposed way of working environment are in the form of briquettes, put it on the bottom of the container, the workpiece set on top of the cake container with the workpiece and the working medium is heated outside the mold press to immersion of the workpiece in the working environment.

Effect the specified differences immersion of the workpiece occurs under its own weight in homogeneous environment, which significantly reduces the probability of formation of voids and, therefore, the transmission of pressure on the compression of the workpiece becomes more in comparison with the prototype, uniform. Thus, the proposed method provides a higher yield of products.

4. Information confirming the possibility of carrying out the invention

Pressing the proposed method was subjected to a block of seven billet rods of the fuel core kermetnogo of a fuel rod of a nuclear reactor. Each blank was the FDS is th zirconium pipe diameter 9.1 mm, length of 60 mm and a wall thickness of 0.7 mm Pipe was filled fuel spheres of uranium dioxide with a diameter of 500 μm and closed with plugs. As the matrix material in the fuel sector was applied a coating thickness of 35 microns zirconium alloy. Block blanks were placed in a steel container with an inner diameter of 46 mm on top of the briquette mass of 320 g of sodium silicate selected as the working environment. The container together with the block of blanks and briquette working medium is heated in a separate furnace to a temperature of 1000°C for 30 minutes After immersion of the block of material in a glass container is transferred into the mold of a hydraulic press and a block of blanks were pressed at a load of 120 tons and machine time 30 C. the Deviation of the shape of the pressed blanks from the cylindrical did not exceed 100 μm, which makes possible to reduce the diameter of the rod during further machining (centerless grinding) to the appropriate value of 7.6 mm without opening and destruction of the fuel particles.

Method of hot isostatic pressing billet fuel rod core kermetnogo of a fuel rod of a nuclear reactor, which consists in the fact that the workpiece is placed in the container, the container is placed in a working environment in which use of glass in the solid state, heat the container with just vcoi and working environment to a temperature of extrusion, place the container in the mold press and apply a pressing force to increase the pressure of the working medium during movement of the punch press, characterized in that the working environment are in the form of briquettes, put briquettes on the bottom of the container, the workpiece set on top of the cake container with the workpiece and the working medium is heated outside the mold press to immersion of the workpiece in the working environment.



 

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