RU2307406C1 - Research reactor fuel element - Google Patents

Abstract

FIELD: nuclear power engineering; mechanical design of research reactor fuel elements.

SUBSTANCE: proposed research reactor fuel element is made in the form of uranium-molybdenum spherical fragment measuring 50 - 200 μm coated with zirconium layer, 3 to 5 μm thick. It is designed for disposing in aluminum matrix. Fuel element is covered with external aluminum coating. Distant arrangement of fuel fragments reduces probability of their immediate contact when compressing fuel composition.

EFFECT: enhanced yield.

4 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 a fuel cell for a research nuclear reactor. Such fuel cells are designed to be placed in the aluminum matrix of the core of the fuel element.

2. The prior art.

Known fuel cell research nuclear reactor, made in the form of a spherical particle of uranium dioxide, intended for placement in an aluminum matrix. (see, for example, A.S. Zaimovsky, V.V. Kalashnikov, I.S. Golovin, "Fuel elements of atomic reactors", Gosatomizdat, Moscow, 1962, p. 254).

Such a fuel cell does not make it possible to provide a uranium concentration of more than 4.5 g / cm ³ in the composition of a fuel element, with the accepted manufacturing technology, which makes it difficult to solve the problem of reducing enrichment by ²³⁵ U to 19.5% in research reactors.

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

- spherical fuel particle,

- the particle is intended for placement in an aluminum matrix.

Also known is a fuel cell of a research nuclear reactor made in the form of a 50-200 μm uranium-molybdenum spherical particle intended for placement in an aluminum matrix (see, for example, M.I.Solonin, A.V. Vatutin et al., " Development of a method for grinding high-density fuel for research reactors "," Selected Works of VNIINM ", v.1, Moscow, 2002, pp. 201-203).

The disadvantage of such a fuel cell is, first of all, the formation at the interface between the uranium-molybdenum particle and the matrix of interaction products having a lower density than the interacting materials, which, along with increased gas evolution, leads to significant local formations of the fuel element. In addition, fission products driven into the matrix to a depth of approximately 13 μm diffuse in it and, therefore, increase the likelihood of contamination of the coolant during depressurization of a fuel element.

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

- spherical fuel particle,

- the particle is made of a uranium-molybdenum alloy,

- the particle is intended to be placed in an aluminum matrix,

- particle size of 50-200 microns.

In the aggregate of essential features, the last fuel cell is closest to the claimed device and is selected as a prototype.

3. The invention

The proposed fuel cell research nuclear reactor is made in the form of a uranium-molybdenum spherical particle with a size of 50-200 microns, designed to be placed in an aluminum matrix, which is coated with zirconium with a thickness of 3-5 microns.

This device differs from the prototype in that the particle is coated with zirconium 3-5 microns thick.

This difference ensures the compatibility of uranium-molybdenum fuel with an aluminum matrix, which allows to achieve greater burn-out without fuel element formation.

In development of the inventive fuel cell, a fuel cell is proposed in which an aluminum coating is applied to a zirconium-coated fuel particle. This solution increases the yield of fuel elements due to the spacing of the fuel particles and reduce the likelihood of their direct contact when pressing the fuel composition.

In development of the claimed design, a fuel cell is proposed in which a coating of ZrAl ₃ intermetallic with a thickness of 8-10 μm is formed on a zirconium coating or between zirconium and aluminum coatings. The introduction of this coating makes it possible to localize fission products from uranium-molybdenum fuel in it, since their mobility in the indicated intermetallic compound (melting point 1560 ° С) is significantly lower than their mobility in aluminum (melting point 660 ° С).

Also in development of the claimed design, a fuel cell is proposed in which, along with the introduction of a ZrAl ₃ intermetallic coating, between the coatings of ZrAl ₃ intermetallic and zirconium, a buffer layer of Zr _n Al _m intermetallic compounds of the Zr-Al system is formed, where n≥2, m ≠ 3. The introduction of a buffer layer of stronger than ZrAl ₃ intermetallic compounds makes it possible to increase compressive stresses in the fuel particle and thereby reduce swelling.

In further development of all the claimed designs, a fuel cell is proposed in which the fuel particles have a size of 100-150 μm and are made with porosity P [%] = (1.1-1.3) B [%], where B [%] is the specified burnout of heavy atoms.

The choice of the indicated sizes of fuel particles and their porosity provides an increase in the geometric stability of a fuel rod by compensating for the "solid" expansion of nuclear fuel by its porosity.

4. List of figures

Figure 1. - Drawing of a fuel cell research nuclear reactor:

1 - uranium-molybdenum spherical particle;

2 - zirconium coating;

3 - coating of aluminum;

4 - coating of intermetallic ZrAl ₃ ;

5 - buffer layer of Zr _n Al _m of the Zr-Al system, where n≥2, m ≠ 3.

Figure 2. - Fuel cell thin section:

1 - spherical uranium-molybdenum particle;

2 - zirconium coating.

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 fuel cell of a research nuclear reactor, consisting of a uranium-molybdenum spherical particle 1 with a size in the range of 100-150 μm, a coating of zirconium 2 with a thickness of 3-5 μm, a coating of aluminum 3, a coating 4 of intermetallic ZrAl ₃ with a thickness 8-10 μm and buffer layer 5 of Zr _n Al _m of the Zr-Al system, where n≥2, m ≠ 3.

All coatings are applied and formed by vacuum magnetron sputtering of the corresponding targets. As an example, FIG. 2 shows a thin section of a spherical uranium-molybdenum particle 1 coated with zirconium 2.

Claims (4)

1. The fuel cell of the research nuclear reactor, made in the form of a uranium-molybdenum spherical particle with a size of 50-200 microns with a coating of zirconium with a thickness of 3-5 microns and intended for placement in an aluminum matrix, characterized in that the outer cell is coated with an aluminum coating . 2. The fuel cell according to claim 1, characterized in that between the zirconium coating and the outer coating is formed a coating of intermetallic ZrAl ₃ with a thickness of 8-10 microns. 3. The fuel cell according to claim 2, characterized in that between the coatings of intermetallic ZrAl _s and zirconium, a buffer layer is formed of intermetallic compounds Zr _n Al _m of the Zr-Al system, where n≥2, m ≠ 3. 4. A fuel cell according to any one of claims 1 to 3, characterized in that the fuel particles have a size of 100-150 μm and are made with a porosity of P [%] = (1.1-1.3) B [%], where B [%] is the given burnup of heavy atoms.

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