Yu.M. Platov

Prospect of development and manufacturing of low activation metallic materials for fusion reactor

Abstract A study of the information generation on the subject of LAM is given. Some results on the development of low activation metallic materials in Russia (vanadium, steels) are presented. The industrial technology for pure vanadium manufacturing is considered from the point of view of low activation material. The important consequences of gaseous forming elements present in vanadium on induced activity are highlighted. Results on the development of a few prototypes of low activation steels are given. The suggestion to use isotopically enriched materials for the most critical structures of reactor has been systematically considered, and conclusions are given. Some aspects of the recycling of structural materials are briefly discussed.

The use of liquid metals in porous materials for divertor applications

Abstract Features of using capillary porous materials (stainless steel, tungsten, graphite) cooled by liquid lithium for divertor module of thermonuclear fusion reactor have been considered. Temperature distribution in divertor plate under the power density of 10 MW/m2 was calculated for steady state and pulsed heat influences. The surface temperature as a function of power density and dependence of lithium evaporation yield on temperature was evaluated. Thickness of cover lithium layer with safe porous material against direct pulse heat influence type of plasma disruption (power density in the range of (1–5)103 MW/m2) was estimated. Concerning the problem under consideration, features of hydrodynamic and capillary effects as well as chemical interaction between lithium and investigated materials have been discussed.

The possibility of the commercial production of low-activation structural steels for fusion energy in the Russian Federation

Laboratory meltings of low activation austenitic and ferritic steels (Fe0.1C12Cr20Mn1W0.2V and Fe0.1C9Cr1W0.15Ta) were done in an inductive furnace. The panoramic analysis of the charge materials and steels were made by means of spark mass-spectrometry. Series of calculations of activation parameters for steels composing from hypothetically pure, isotopically enriched macrocomponents and for real materials were conducted. The possible metallurgical technologies of industrial production of the low activation steels in the Russian Federation including processes of initial charge materials purification are considered.

Radiation resistance and parameters of activation of aluminium-magnesium-scandium and aluminium-magnesium-vanadium alloys under neutron irradiation

Alloys Al2.24Mg0.23Sc0.04Zr, Al2.24Mg0.12Sc0.04Zr, and Al2.24Mg0.05V (at.)) annealed at 150°C and 400°C were irradiated ≈70 and ≈150°C in the SM-2 reactor. The maximum neutron fluence was 4.7×1024 m−2 (E > 0.1 MeV). The tensile tests were carried out in the temperature range 20 to 350°C. Alloy Al2.24Mg0.23Sc0.04Zr annealed at 400°C and alloy Al2.24Mg0.12Sc0.04Zr annealed at 150°C at all test temperature, retained good mechanical properties after irradiation. The mechanisms for the radiation resistance of aluminiumscandium and aluminiummagnesiumscandium alloys are discussed. Calculations of induced radioactivity and its decay behaviour after shutdown in aluminium and Al2.24Mg(0.12–0.23)Sc alloys were carried out. Composition of the radionuclides in these materials after irradiation in the SM-2 reactor were also determined using a gamma-spectroscopy technique.

VGa-based alloys as candidate materials for fusion reactor application

Abstract Results of the experimental study of some physical, mechanical and technological properties of the reduced activation vanadium—gallium-based alloys are presented. The activation calculations show that Ga has the lowest cooling time not only in comparison with alloying elements Ti and Cr in low activation VTiCr alloys but also with vanadium. The effect of Ga(1–8 at%), Cr (5–6 at%) and Ce(0.05–0.1 at%) on workability, mechanical properties, thermal conductivity, elastic modulus (E,G), and Poissons ratio of VGa was studied. The same properties of some are also studied. The level of tensile properties, thermal conductivity and elastic properties of VGa alloys are comparable with VTiCr alloys, but their activation parameters and ductility are superior. The experimental results make it possible to recommend VGa-based alloys as reduced activation structure materials for fusion reactors.

Phase instability of alloys caused by transmutation effects during neutron irradiation

Abstract A theory of the phase changes in a two-phase binary A-B alloy in the coarsening condition caused by burnout of solute B due to nuclear reactions is presented. It is shown that this burnout process introduces diffusion redistribution of solute between second phase precipitates and solid solution. The burnout induced solute flux away from second phase precipitates to solid solution maintaining the concentration of element B in the vicinity to its solubility limit and stimulates, thus, the second phase particle dissolution. This occurs in addition to a process decreasing their sizes as a result of direct burnout of atoms B in the precipitates. In the framework of the theory developed here, analytical expressions describing time evolution of the precipitate size distributions, changes of mean radius and number density of the precipitates, and second phase dissolution times are obtained. On the basis of these results and numerical calculations for aluminium-scandium alloy, it is shown that the burnout processes can induce essential phase changes, and thus cause significant changes of the properties of irradiated materials at high neutron fluences.

Lithium Carbide is Prospective Material for Breeder of Fusion Reactor

It is shown that lithium carbide is a prospective material for breeder of fusion reactor. The lithium carbide equivalent dose rate reaches a biologically safe level (2.3 × 10−5 Sv/h) one minute after the irradiation with fusion reactor neutrons (with a fluence of 2 × 1023 cm−2) is stopped. The yield of tritium from lithium carbide is 1.5–2.6 times higher than the corresponding yield from such lithium ceramics as Li4SiO4 and Li2TiO3.

Nucleation and growth of interstitial dislocation loops in irradiated aluminum

Formation and growth of dislocation loops of interstitial type in Al (99.999%) during in situ irradiation with 1-MeV electrons at 20–150°C using a high-voltage electron microscope are investigated by transmission electron microscopy. Experimental results are analyzed within the classical theory and kinetic model of nucleation and growth of loops. The parameters controlling the process of radiation-induced formation of interstitial dislocation loops under irradiation are determined.

Kinetics of low-temperature radiation hardening of metallic materials under irradiation

A formula is obtained which describes the kinetics of low-temperature radiation hardening caused by creation of dislocation loops of interstitial type during irradiation. The radiation hardening of aluminum and vanadium is estimated using this formula and results of experiments on studying processes of nucleation and growth of interstitial dislocation loops in these materials by transparent electron microscopy. It is shown that the proposed formula is valid for description of the kinetics of low-temperature radiation hardening.

Structural and phase changes and radiation damage in low-activation vanadium-titanium alloys on electron and neutron irradiation

Abstract Vanadium and vanadium-titanium alloys were irradiated either at 100°C with electrons ( E = 2.2 MeV) or at ≈150°C in the SM-2 reactor. The maximum electron irradiation fluence was 5×10 22 m −2 , and neutron fluence was equal to 4.7×10 24 m −2 ( E >0.1 MeV). The structural and phase changes in the irradiated materials were studied by utilization of positron annihilation, microhardness, and transmission electron microscopy techniques. The mechanisms of suppression of radiation damage in vanadium-titanium alloys are discussed on the basis of the results obtained. Calculations of the induced radioactivity and its decay behaviour after shutdown in hypothetically pure vanadium and vanadium-titanium alloys were carried out. Studies of the radionuclides produced in vanadium and a V-21.5at%Ti alloy after irradiation in the SM-2 reactor to a fluence of 5×10 24 m −2 were conducted with the use of gamma-spectroscopy.