Physics of Atomic Nuclei最新文献

A study of fractographic features of fracture surfaces, patterns of structural-phase transformations, and mechanisms of plastic deformation and fracture of low-activation vanadium alloy V–Cr–W–ZrC in the process of toughness tests was carried out. The appearance of a qualitatively new (non-dislocation) mechanism of plastic deformation was revealed—the mechanism of bcc → hcp → bcc transformation with a change in the systems of reverse transformations and (or) the participation of quasi-viscous mass transfer in the fields of high local pressure gradients. An important feature of this mechanism is its activation at the nanoscale level with the formation of nanovolumes several nanometers in size—new carriers of homogeneous transformation deformation of the Bain type. A significant feature of these carriers is the absence of any effective obstacles such as dislocations or disorientation boundaries for both homogeneous tensile/compressive deformation and quasi-viscous mass transfer. The activation of bcc → hcp → bcc transformations as a new non-dislocation deformation mode is based on the phenomenon of phase instability of the bcc crystal in fields of high local stresses and high local gradients of the nanoscale level. The above transformations (both direct and reverse) can be carried out under conditions of thermodynamic gain with a local (in the transformation zone) decrease in energy in the transformation region. This leads to intense softening of the material and high deformation and relaxation rates of highly defective substructures of deformation and deforming and local internal stresses.

The unique properties of high-temperature superconductors (HTSCs) and progress in the manufacture of HTSC-based wires made it possible to develop a new generation of tokamaks. In Russia, a tokamak project with reactor technologies (TRT), in which the magnetic field induction reaches 8 T on the plasma axis and 15 T and higher on the windings of the electromagnetic system, is being developed. The creation of HTSC current-carrying elements (CCEs) that meet the stringent requirements for the TRT magnetic system is one of the key issues of the entire project. A number of short experimental CCE samples that are potentially applicable in TRT magnetic systems was developed. A series of physical and mechanical tests were carried out to check the mechanical properties and develop a universal certification methodology for CCEs accepted for operation.

Changes in the structural state of steels of VVER-1000 reactor pressure vessels (RPVs) at an extended lifetime of 60 years and more were considered. A comprehensive analysis of available experimental data on changes in the structural state of RPV materials under irradiation was carried out. Extended dose dependences of the accumulation rate of radiation-induced structural elements and grain-boundary segregation of phosphorus are presented. The nature of changes in strength characteristics and critical brittleness temperature of RPV materials due to irradiation was shown. A preliminary estimate of the lifetime of RPV steels depending on their nickel content was made basing on the study of trends in the volume density and average size of radiation-induced structural elements, radiation defects, and radiation embrittlement mechanisms.

The article presents the results of testing miniature CT-0.16 specimens made from materials of the VVER-1000 reactor pressure vessel materials in both unirradiated and irradiated conditions, as well as after thermal aging, treated using the master curve method (ASTM E1921). A comparative analysis of the obtained transition temperatures T₀ and results previously obtained for standard three-point bending of PCV specimens was conducted, showing a similarity of these values. An assessment of metal heterogeneity on the basis of the conducted tests according to the SINTAP procedure was carried out, indicating the need to increase the number of CT-0.16 specimens in the test series for the correct determination of the parameter T₀. A conclusion was drawn regarding the prospects of using CT-0.16 type specimens for determining fracture toughness of reactor pressure vessel steels in conditions of limited volume of metal.

The results of a part of works carried out by the NRC Kurchatov Institute in the development of the physical and technical foundations of the technology of high-temperature gas-cooled reactor (HTGR) systems are presented. Integral components of the development of the physical and technical foundations of the HTGR technology are the improvement of methodology and software for calculations to justify the nuclear and physical part of the project and experimental studies, such as the study of neutronic characteristics of reactors of this type on a critical facility, the study of tightness of fuel samples, and materials science studies of samples in fuel quality control procedures. Maintaining the HTGR knowledge base makes it possible to consolidate the accumulated experience and identify individual critical technologies and is also used in the preparation and implementation of technological development plans aimed at obtaining missing design data.

In this paper, we present the test results of the corrosion and mechanical resistance of the KhN80MTYu alloy and its modifications under dynamic nonisothermal conditions of circulation of a coolant with a molar composition of 0.66LiF–0.34BeF₂ in the range of operating parameters of the MSR intermediate contour. The three most promising compositions of candidate alloys for the MSR are selected. In terms of the rate of uniform corrosion and mechanical properties, the alloys were shown to be capable of ensuring reliable operation of the structure for up to 30 years with maximum temperature of up to 690°C upon maintaining the melt redox potential in the range of E_PBe = –(0.59–0.79) V.

The article considers the possibilities of a fusion neutron source with a molten-salt blanket to provide fuel for thermal fission reactors with uranium-thorium nuclear fuel cycle, and it also formulates recommendations for closing fuel nuclide balances in a nuclear power system with fission and fusion reactors.

Uncertainty of predictive calculations of the neutronic characteristics of the RBMK-1000 reactor due to the lack of information about the cutting scheme to be used in the repair of graphite masonry is assessed. The main schemes of the repair of graphite masonry are considered.

The paper presents the results of a study of the properties of high-sensitivity self-powered neutron detectors (SPND) in order to determine their sensitivity to the conditional neutron flux and absorbed dose rate of ⁶⁰C gamma radiation in metrologically certified zones at the research reactors OR and IR-8, the critical nuclear stand KVANT, and the gamma radiation installation GUT-200M at the NRC Kurchatov Institute.

A simple qualitative model of the influence of grouping of atomic levels on the radiation losses of impurity ions in a near-wall low temperature plasma is proposed using the example of line radiation losses when excited states are populated by impact excitation by plasma electrons. A comparison of the relevant data simulated by the ADAS codes for low-charge ions of argon, neon, and nitrogen ions confirms the predicted effects of possible underestimation or overestimation of radiation losses when the number of atomic levels taken into account in the simulation in the collisional-radiative model decreases.