Corrosion resistance of vanadium alloys in lithium upon neutron irradiation
The corrosion resistance of aluminothermic vanadium and vanadium-based binary (with 10 and 35 at. % Ti) and ternary (V–Ti–Cr) alloys in lithium is studied upon neutron irradiation. Samples of the alloys sealed in lithium-filled ampules are irradiated with fast neutrons to a fluence of 1023 cm–2 at 350–830°C in a BOR-60 reactor. It is found that the concentration of interstitial impurities (oxygen and carbon) at the surface of vanadium alloys upon irradiation is higher than that in the alloys studied under static conditions. When the vanadium alloys operate under irradiation and attack by lithium used as a heat-transfer medium, a high contamination of the surface layers in the alloys with interstitial impurities and their effect on the physical and mechanical
properties of the alloys it should be taken into account.
A major concern in using vanadium alloys for first wall/blanket systems in fusion reactors is their activity with regard to nonmetallic impurities in the coolants. This paper presents the results of studying the corrosion resistance in high-purity liquid lithium (with the nitrogen and carbon content of less than 10–3 wt %) of vanadium and vanadium alloys (V–1.86Ga, V–3.4Ga–0.62Si, V–4.81Ti–4.82Cr) both in the initial state and preliminarily irradiated with Ar+ ions with energy of 20 keV to a dose of 1022 m–2 at an irradiation temperature of ~400°C. The degree of corrosion was estimated by measuring the changes in the weight and microhardness. Corrosion tests were carried out under static isothermal conditions at a temperature of 600°C for 400 h. The identity of corrosion mechanisms of materials both irradiated with Ar ions and not irradiated, which consisted in an insignificant penetration of nitrogen into the materials and a substantial escape of oxygen from the materials, causing the formation of a zone with a reduced microhardness near the surface, was established. The influence of the corrosive action of lithium on the surface morphology of the materials under study was found, resulting in the manifestation of grain boundaries and slip lines on the sample surface, the latter being most clearly observed in the case of preliminary irradiation with Ar ions.
The influence of neutron irradiation on the mechanical properties of vanadium and the alloys V-10.6 Ti and V-10 Ti-6 Cr-0.05 Zr is investigated. Alloy samples are irradiated in the pile of a BOR-60 reactor to a fluence of (0.8-1)·10 22 cm -2 (E > 0.1 MeV) at 350°C. The results show that the irradiation of vanadium and its alloys in these conditions leads to insignificant (less than 0.1%) swelling but changes their mechanical properties (strength and plasticity). The radiational strengthening is greatest for pure vanadium and least for the alloy V-10.6 Ti. Adding chromium to the alloy reduces the positive effect of titanium and leads to low-temperature radiational embrittlement in the range 20-100°C. As shown by electron-microscope investigation, the change in mechanical properties of the alloys after irradiation is associated with the formation of a dislocational structure and with radiation-stimulated segregation.
The dynamics of a two-component Davydov-Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg-de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton`s component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations.
Radiation conditions are described for various space regions, radiation-induced effects in spacecraft materials and equipment components are considered and information on theoretical, computational, and experimental methods for studying radiation effects are presented. The peculiarities of radiation effects on nanostructures and some problems related to modeling and radiation testing of such structures are considered.
This volume presents new results in the study and optimization of information transmission models in telecommunication networks using different approaches, mainly based on theiries of queueing systems and queueing networks .
The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.