Nuclear fuel granule simulator

FIELD: nuclear power engineering.

SUBSTANCE: proposed invention may be found useful for optimizing manufacturing process of dispersion-type fuel elements using granules of uranium, its alloys and compositions as nuclear fuel and also for hydraulic and other tests of models or simulators of dispersion-type fuel elements of any configuration and shape. Simulators of nuclear fuel granules of uranium and its alloys are made of quick-cutting steel alloys of following composition, mass percent: carbon, 0.73 to 1.12; manganese and silicon, maximum 0.50; chromium, 3.80 to 4.40; tungsten, 2.50 to 18.50; vanadium, 1.00 to 3.00; cobalt, maximum 0.50; molybdenum, 0 to 5.30; nickel, maximum 0.40; sulfur, maximum 0.025-0.035; phosphor, maximum 0.030; iron, the rest.

EFFECT: enhanced productivity, economic efficiency, and safety of fuel element process analyses and optimization dispensing with special shielding means.

1 cl, 3 dwg

 

The invention relates to the nuclear industry and can be used in the development of the technology of manufacture of the fuel rods of the dispersion type, which as nuclear fuel used pellets of uranium, its alloys and compounds, as well as hydraulic or other tests of mock-UPS or bundle simulators dispersion type any configuration and shape.

Known use as nuclear fuel crushed grains of the alloy U-9% Mo, dispersed in the magnesium matrix (Samoilov A.G., Chestnut A.I., V.S. Volkov Dispersion fuel elements. Tom. 2, M, Energoizdat, 1982, s-161). However, obtaining powder-grain U-9% Mo alloy methods of crushing or mechanical grinding of the original ingots enough energy and time-consuming process.

In recent years there has been increased interest in powders and granules of uranium and its alloys with Mo, Zr, Nb, Si, Os, Re, and other items in connection with the international program of the non-proliferation of nuclear weapons, reducing nuclear fuel dispersion fuel elements of research reactors, isotope uranium - 235. At lower enrichment fuel in the isotope uranium - 235 to less than 20% of the mass, with the aim of preserving in Fe total uranium - 235 at a constant level, it is necessary to increase the concentration of total uranium in the fuel elements, or to use as fuel over the raft is s uranium compounds, what used to reduce enrichment (oxides, aluminides, silicides uranium). Because the limits of increasing concentrations of nuclear fuel rods dispersion type have been exhausted (40-50% by volume), and the required amount of uranium - 235 was not brought to the required number, as fuel for dispersion fuel elements was proposed to use compounds of uranium and its alloys with a density greater than 17 g/cm3. Alloying elements in the alloy are introduced in quantities sufficient for a partial or complete stabilization γ-phase, to reduce the interaction of the fuel with the matrix material and the shell, to help reduce swelling during operation of a fuel rod in the reactor. Most commonly used dispersion fuels in the form of pellets, spheres with a size less than 500 microns.

Known pellets of nuclear fuel from uranium-molybdenum alloy and method of production thereof by centrifugal atomization of the melt with the rotating ingot electrode (A.B.Aleksandrov, A.A.Enin and Tkachyov. Reduction of fuel enrichment for research reactors built-up in accordance with Russian (Soviet) projects. Transactions Oral Presentations and Posters ENS RRFM 2001, p. 127-131, 2001.), (R.Kh.Gibadullin, A.D.Karpin, Yu M.Pevchikh, V.V.Popov, V.N.Sugonyaev, V.M.Troyanov. Examination of U-9% Mo alloy powder microstructure in its initial condition and after fuel pin fabrication. 6thInternetional Topical Meeting on Research Reactor Fuel Management. Ghent, Belgium. March 17-20, 2002, R-196).

A method of obtaining spherical pellets of uranium and its alloys, for localsize is the uranium and alloying materials are loaded into the crucible, melt electric arc or induction heating, the melt is fed to the rotating disc and is sprayed in the atmosphere of inert gas under the action of centrifugal force. The composition of the spherical granules obtained by this method is as follows: basis of uranium, about 4-9 mass % Q and about 4 mass % X, where Q - Mo, Nb, Zr, and X is selected from Mo, Nb, Ru, Pt, Zr, Si, Ir, Rd, W, with Q≠X (U.S. Patent No. 5978432 from 02.11.1999,, MKI G 21 3/60 priority from 17.04.1998, the patent of the Republic of Korea (South Korea) No. 98-15783).

Obtained by the above methods Krupka and spherical granules are used as a dispersion nuclear fuel in the fuel elements of research reactors. The increase in the load on the dispersion of the fuel matrix, the fuel rod, the use of spherical fuel instead of semolina require experimental work on the development of technological regimes, such as

- mixing of spheres, granules of powder matrix material (aluminum, its alloys or magnesium);

- pressing mixtures;

- rolling or extrusion billets in the shell;

hydraulic tests of fuel elements when changing their design, as well as a number of other research and development.

To use for these purposes spherical pellets of nuclear fuel from uranium and its alloys is not always advisable because of the product received, the AK rule, sent for processing. In addition, working with radioactive materials imposes a number of restrictions, both organizational and safety. All these restrictions reduce the number and increase the experiments and experimental works. For the initial studies, you can apply granules simulators substitutes nuclear fuel. So, in the work (T.C.Wiencek and I.G.Prokofiev. Low-Enriched Uranium-Molybdenum Fuel Plate Development. To be presented at the 2000 International Meeting on Reduced Enrichment for Research and Test Reactors/ October 1-6, 2000, Las Vegas, Nevada, USA, p. 273-284) as the simulator uranium-molybdenum spheres are spherical tungsten particles.

theoretical density of tungsten is close to the density of uranium and its alloys, therefore, spherical granules of tungsten require fractional composition as nuclear fuel, can be used in the practice of blending modes and loading the mixture into the form, the study of the process of separation of spherical granules and matrix powder of aluminum, magnesium and their alloys. However, pure spherical tungsten powder, a particle size close to the size of the granules of U-Mo alloy ie, less than 160 microns is also quite expensive because it requires a special high-temperature technology of its production and mechanical processing cores bundle simulators with granules of tungsten is difficult due to the fact that the ox is FRAM is intractable metal.

The objective of the invention is to replace the spherical pellets of nuclear fuel from uranium and its alloys and their imitators of tungsten in experimental work and development of technological regimes and structural elements, less expensive, more accessible and safer granules.

The problem is solved by applying spherical pellets of known materials, such as high-speed steels having the following chemical composition, wt.%: carbon from 0.73 to 1.12; manganese and silicon not more than 0,50; chromium from 3.80 to 4,40; tungsten from 2.50 to 18,50; vanadium from 1.00 to 3.00; cobalt, not more than 0,50; molybdenum from 0 to 5.30; Nickel not more than 0,40; sulfur does not exceed 0.025-0,035; phosphorus not more than 0,030, the rest is iron.

Spherical pellets of high-speed steels obtained by centrifugal electric arc spraying rotating ingot electrode or by gas atomization of the melt. So, for example, spherical granules of high-speed steel brand PR-RM (GOST 19265-73 Bars and strips of high speed steel. Technical conditions. Ed., standards, 1986) produced according to the technical specifications (Technical specifications 14-1-3851-84. Powder high-speed steel used for the manufacture of cutting tools by powder metallurgy methods.

Figure 1 shows the surface morphology of spherical granules of high-speed steel PR-RM.

2 shows the morphology is poverhnosti spherical granules of alloy U-9% Mo.

Figure 3 shows the cut: spherical pellet of high-speed steel brand PR-RM-1, in the matrix of aluminum alloy - 3, simulating the interaction matrix of a fuel rod of aluminum alloy with the formation of intermetallic IUxAly- 2.

The surface morphology of the granules made of high speed steels identical surface morphology of the pellets of uranium-molybdenum alloys.

Lower the temperature of the melt (melting) upon receipt of the granules of relatively high-speed steels tungsten, as well as the content composed of a small number of expensive components, such as tungsten and molybdenum, make granules available for use as imitators of pellets of nuclear fuel.

Typically, in the manufacture of fuel rods dispersion type as the matrix of the fuel core fuel elements are aluminum, magnesium and their alloys. Temperature regimes of their treatments and the fuel rods does not exceed 600°and, as a rule, are in the range C°C.

Proposed as imitators of nuclear fuel spherical granules of alloy high-speed steel to a temperature of 600°resistant to oxidation in air for a long time, do not form an oxide layer that is prone to shattering or interaction with the matrix and shell material of the fuel elements.

However, during long-term exposure more than 5 hours at a temperature of more than 500°material granules imitators, as well as material pellets of uranium and its alloys, starts to interact with the material of the fuel core and the shell, that is, aluminum or alloys of aluminum, forming their intermetallic compounds of the type MexAly. Thus, it is possible to observe the change in the volume of fuel elements or components as in the case of the interaction of uranium and its alloys with aluminum.

Example 1. Figure 3 shows the use as a simulator of pellets of nuclear fuel in the matrix of the aluminum alloy during heating of the simulator core of a fuel rod at a temperature of 600°C for 6 hours, industrially produced spherical granules of high-speed steel brand PR-RM having the following chemical composition, wt.%: carbon 0,82-0,90, manganese and silicon not more than 0,50; chrome 3,80-4,40; tungsten 5,50-6,50; vanadium 1,70-2,10; cobalt, not more than 0,50; molybdenum 4,80-5,30; Nickel not more than 0,40; sulfur does not exceed 0.025-0,035; phosphorus not more than 0,030, the rest is iron.

1 - simulator nuclear fuel-spherical granules of alloy RM;

2 - the layer of intermetallic MexAlyformed by the interaction of spherical granules of alloy RM with aluminum alloy that simulates the interaction of nuclear fuel matrix and shell mother of the scrap; 3 - aluminum alloy.

The presence of granules made of high speed steel-type elements tungsten, molybdenum makes these granules contrast on the background of the membranes of the fuel elements and the matrix of aluminum and its alloys, that is, allows x-ray control their distribution in the matrix core simulator fuel element.

Be aware that uranium and its alloys with Mo, Zr, Nb, W, TA, Si, Ru, Rd have different hardness, depending on how the content of these components, and methods of obtaining and treatment. Thus, the hardness of the alloy U-Mo 8% (mass) can vary from 280 to 620 kg/mm2when the temperature of the processing from 300 to 600°and the exposure time at these temperatures from 0.1 to 1000 hours, and the hardness of the alloy U-Mo 10% (mass)treated at the same temperature-time characteristics ranges from 300 to 560 kg/mm2.

Selected as imitators of nuclear fuel pellets from alloys of high speed steels can be changed to the desired hardness as the pellets of nuclear fuel, changing the time-temperature regimes preliminary heat treatments. For this purpose, the granules of the high-speed alloys subjected to quenching or tempering.

Example 2. Increasing the temperature of the granules of alloy R6M5 500°With up to 860°With subsequent slow cooling is about 50° C/hour, the hardness of the material of the granules varies from 975 to 340 kg/mm2.

Thus, the application of the simulator pellets instead of pellets of nuclear fuel will allow the processes of research and development of the technology TVEL without equipment with special protection, more economical, efficient and safe.

The use of granules of alloy high-speed steel composition: carbon from 0.73 to 1.12; manganese and silicon not more than 0,50; chromium from 3.80 to 4,40; tungsten from 2.50 to 18,50; vanadium from 1.00 to 3.00; cobalt, not more than 0,50; molybdenum from 0 to 5.30; Nickel not more than 0,40; sulfur does not exceed 0.025-0,035; phosphorus not more than 0,030 wt.%, the rest is iron, as imitators of pellets of nuclear fuel from uranium and its alloys.



 

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