The method of preparation of materials, predominantly non-metallic, for use in neutron fields

 

(57) Abstract:

The invention relates to methods of processing materials intended for use in the core of nuclear reactors. The preparation of predominantly non-metallic materials for use in neutron fields provide shock-wave effects generated by explosives. The amplitude of the pressure P when the effect is selected in the range: 1 HPa < P 100 HPa.

The invention relates to a method of processing materials intended for use in the core of nuclear reactors.

When the materials in the core of nuclear reactors characteristic is the increase in dimensions of the parts, i.e., the decrease of the density of the materials. The most significant are the three causes of swelling: the changing nature of strength of bonds between atoms (including and leading to change of the crystal structure) - examples: BeO increases by 16%, diamond - 50%, GdAlO3- 6% (C. M. Kosenkov. X-ray diffraction effects and swelling of some non-metallic materials after neutron irradiation. Radiation materials science. T. 7. Proceedings of the International conference on R. the emer: stainless steel, an increase of 20% (C. Cawthorue, E. J. Fulton. Voids in irradiated stainloss steel. Nature, 216 (1966), 5115 N, R. 575); the formation of gas bubbles - example: B4C, increase by 40% (M. S. Kovalenko centuries, gardeners. Radiation damage to the material of the reflector. M: Atomizdat, 1979).

As a result of these events disrupted the normal maintenance of the reactor, burst protective steel shell elements with absorbing (B4C) and reflecting (BeO) materials.

Developed techniques to combat swelling of various materials. There is a method of preparation of reactor materials, which consists in obtaining the crystal structure more resistant to neutron irradiation. The dysprosium titanate is used as the absorber, with the equilibrium structure of the pyrochlore type, the radiation enters the structure of fluorite type with a volume increase of more than 4%. The training material is that it pre-irradiated in a fast neutron flux, which does not change the absorption ability of dysprosium, to fluence, when there is a transition in the structure of fluorite. For subsequent use in a nuclear reactor the amount of dysprosium titanate increases not more than irradiation;

the induced radioactivity of the material increases the technological difficulties of its further use;

significant methodological limitations in the implementation of this method.

A known method of improving the radiation resistance of stainless steels by cold deformation by 20 - 30% [2]. Arise during the deformation dislocations and other distortion patterns affect the dynamics of accumulation and aggregation of point defects that occur during irradiation, which leads to decrease swelling.

The disadvantage of this method is limited its scope only to the plastically deformable materials (metals).

Thus, before the creators and operators of nuclear technology has always stood and task - reduction of swelling materials from neutron exposure.

The present invention is to increase the radiation resistance of materials used in the fields. This is achieved by the fact that preparation for use in neutron fields materials are shock-wave impact of the explosion, resulting in their deformation. In the preparation of predominantly non-metallic material is P in the range of 1 GPA <P Shock waves and phenomena of high-speed deformation of metals, edited by Meyers, M. A., Murer L. E., metallurgy, 1984, page 512; Batsanov C. S., frost, E. M., Kasutin B. N. Effect of an explosion on the matter, Journal of structural chemistry, 1970, T. II, vol. 1, page 156; Adadurov, A., goldanskii Century. N. "Advances in chemistry, 1981, T. 50, page 1810).

From General considerations it is clear that each extra location or any other entity that is a drain for the primary radiation defects, reduces the amount of swelling.

As a result of application of the proposed method in forming high concentration of lattice defects, which affect the dynamics of primary radiation defects: vacancies and displaced atoms. As drains for primary defects, distortion patterns, the formation of the inventive method of processing of the material, removes them from the process of the formation of secondary defects clusters of defects of various types, which leads to the reduction of the swelling of the material compared to the swelling of those materials that have not undergone the claimed process.

An example implementation of the proposed method.

Was selected four ceramic substances belonging to different classes according to their crystalline characteristics. The gadolinium aluminate (GdAlO3) the IPA bias. Aluminum nitride (AlN) and zinc oxide (ZnO) are substances with temperature phase transitions reconstructive type. These two substances have different mechanisms of radiation damage of the crystal lattices. GdAlO3and Gd2Ti2O7was seen as absorbing compositions, AlN is used in magnetic sensors operating in neutron fields thermonuclear reactor, ZnO is similar for the crystallographic analysis-chemical structure of beryllium oxide (BeO), and has with him the same effects of radiation damage (C. M. Kosenkov. X-ray study of radiation damage in beryllium oxide and other compounds with lattice wurtzite. The dissertation. The Melekess, 1968).

In the context of the stated objectives of the original samples were subjected to the shock-wave effects generated by explosives with pulse amplitude 1 - 23 GPA.

Then blasted material along with the original were irradiated in the reactor CM-2 fluence to 11021n/cm2at a temperature of 100oC. the Results showed that after treatment with the explosion with the amplitude of the pressure pulse 1 HPa swelling blown materials within chuvstvitelnostyu explosion with pressure amplitude 23 HPa swelling GdAlO3accounted for 73% of the swelling of the source material, Gd2Ti2O7- 71%, AlN - 38%, and ZnO - 24 %.

Thus, there is a significant reduction in the lattice swelling of ceramic materials, processed by the blast.

Introduction processing by the explosion in technology training reactor materials experiencing significant swelling in the irradiation will reduce the amount of swelling that will reduce the load on the absorbing shell and other elements of the active zone, will prevent their failure from loss of containment shell which will increase the resource of the corresponding elements and components of the active areas, will enhance the safety of nuclear reactors. Because many of the materials of the active zones are used in the form of a powder, pour into a metal shell (BeO, B4C, GdAlO3), the application of the proposed method will not increase the cost of subsequent technological operations training blasted materials for use in nuclear reactors. For each material, the pressure in the pulse amplitude of the explosion must be chosen from considerations of valid values swelling and economic aspects of the interval 1-100 HPa (100 HPa is almost dollah, including the effects of the materials, resulting in their deformation, characterized in that in the preparation of predominantly non-metallic materials subjected to shock-wave impact generated by explosives, with the amplitude of the pressure P in the range of 1 GPA < P 100 HPa.

 

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