L.I. Ivanov

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.

Hydrogen permeability over the joint weld of the steel parts of fusion reactor with magnet confinement of plasma

Abstract Hydrogen and its isotopes diffusion and permeability over the laser joint weld of low-activation 10Cr9WVA ferritic steels have been studied. Welding of steel sheets were produced with the help of Russian gas laser TL-5M type ( l =10.6 mm, P =2.5 kW) in He atmosphere with the rate of 66 mm/s. Hydrogen diffusion over the joint welds was detected by the conventional method of electrical resistance measurement. By this way, the kinetics of resistance changes during hydrogenation of specimens engraved from weld metal, neighboring zone of thermal effect as well as basic metal have been determined. Coefficients of hydrogen diffusion were measured in the temperature range from 773 to 1073 K. So, for 10Cr9WVA steel at 873 K it was established that the hydrogen diffusion coefficient in the weld metal is approximately 10 times higher than in the basic metal, and three times higher than that in the zone of thermal effect. Hydrogen permeability over the joint weld specimens was measured by the Dines–Barrer method on the volummetric setup. It was established that the hydrogen flux over the laser joint weld is significantly (up to two orders) more than that over the basic metal. Using the data on the hydrogen permeability and diffusion coefficient, the hydrogen solubility in the weld metal was estimated, which is several ten times higher than that in the basic metal of the steel investigated. As a result, it was concluded that welding the steel parts of the first wall of thermonuclear reactors with magnet confinement of plasma is undesirable due to possible tritium leaking into the environment. A possible way of decreasing the joint welds hydrogen permeability, including application of protective impermeable for hydrogen coatings, is considered.

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.

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.

High temperature creep behaviour of 12Cr-20Mn-W austenitic stainless steel

Abstract Results of a simple creep test of three FE-12Cr-20Mn-1W alloys are presented, performed at temperatures from 873 to 973 K and at applied stresses corresponding to dislocation creep conditions. The influence of the carbon content on creep behaviour is established. The creep behavior of the steels is also comparedwith that of some standdard Fe-Cr-ni and Fe-Cr-Mn-Ni austenitic stainless steels.

Environmental problems of application of iron as a base material of low activating steels for fusion and fission reactors

Abstract A forecast of the accumulation of the long-lived radionuclides of 60Co and 53Mn from iron irradiated in fusion and fission reactors was made. It was demonstrated that from hypothetically pure iron consisting entirely of 56Fe isotope, one can create structural steels whose cooling takes less than 50 years for decay of induced radioactivity to a safe level after ten years of irradiation. Some problems related with manufacturing of iron enriched in isotope 56Fe have been considered. Due to the important role of trace elements, an analysis of impurity control for some industrial grades of iron and other steel components available on the market has been carried out. It has been found that only two samples of direct-reduced iron manufactured by the association “Tula Chermet” and the Institute of Metallurgy (Moscow) are pure enough to be used as a base material for a low activating steel.

Study of Fe-12Cr-20Mn-W-C austenitic steels irradiated in the SM-2 reactor

Abstract A comparison has been made between the mechanical properties and swelling of austenitic stainless steels EP-838 (Fe-Cr-Mn) and 316SS (Fe-Cr-Ni) irradiated in the mixed-neutron spectrum of the SM-2 reactor in the temperature range 400–800°C (every 100°C) to 16 dpa dose with 1000 and 3000 appm helium generation correspondingly, determined by nickel content. EP-838 exhibited less susceptibility to void swelling and radiation hardening. Fe-12Cr-20Mn-W-0.1C steel without nickel irradiated at 100°C to 21 dpa exhibited significant radiation hardening accompanied by α-phase formation in the steel structure.