Shipping out the spent fuel of the research reactors at the Institute for reprocessing is examined. The spent fuel is characterized by a great diversity of structural characteristics of the fuel assemblies and fuel elements, fuel compositions, and the enrichment, burnup, and cool-down times of the fuel as well as the state of the components of the assemblies and the structural materials. A classification and quantitative indicators of the accumulated spent fuel from the standpoint of the modern state of its reprocessing technology and the requirements for delivery to the Mayak Industrial Association are presented. The structural features of the TKU-19 and -128 shipment containers are presented, and the loading of spent fuel assemblies into them for shipment to reprocessing is described. The plans and goals of further work on the removal of spent fuel from the Institute's territory are presented.Twelve research nuclear reactors, about 20 experimental critical and subcritical nuclear stands, hot materials science laboratories for performing research with irradiated nuclear fuel, and some other unique physical factilities have operated as part of the experimental base at the Russian Science Center Kurchatov Institute [1, 2]. As a result of many years of experimental operation of the reactor base, a substantial amount of spent nuclear fuel with total activity exceeding 10 16 Bq has accumulated in the course of various scientific programs. This high level of activity is what dictates the urgency of removing this fuel from the Institute's territory to reprocessing facilities.Storage Conditions, Characteristics, and Classification of Spent Fuel. The irradiated fuel is primarily in the form of spent fuel assemblies, fuel elements, and their fragments in research reactors which were disassembled at different times: RFT, IRT, Romashka, Enisei, VVR-2 and OR, MR operated in the final shutdown regime, and the IR-8 and rebuilt OR which are currently operating.After being off-loaded, the irradiated fuel was put into temporary storage sites at the Institute, which were built so that the reactors could meet their operational requirements and that the spent fuel is handled safely. The technical state of the storage sites meets the modern nuclear and radiation safety as well as physical protection requirements. Spent IR-8 fuel is located in a storage pond at the reactor site; IRT, RFT, and MR fuel is located in a centralized dry storage facility on the main site of the Institute; Romashka and Enisei fuel is located in a dry storage facility of complex "R" as well as on the main site; VVR-2 and OR fuel is located in storage ponds of a complex of research reactors and critical stands (Gazovyi Zavod complex) that is located on an auxiliary site at the Institute.
Experiments on measuring the water velocity in the gaps between the fuel elements of an IRT-3M eight-tube fuel assembly with 90% fuel enrichment, used in pool and tank research reactors, are described. The experiments were performed on a hydraulic facility at the National Research Center Kurchatov Institute. The velocity was determined from the dynamic head in the gaps of a model fuel assembly. These velocities were used as a basis for determining the water flow rate in each gap and the total flow rate through a fuel assembly. Comparative hydraulic calculations of IRT-3M fuel assemblies with 90% fuel enrichment and IRT-4M fuel assemblies with 19.7% enrichment, developed as a replacement for IRT-3M, are described. It is shown that if the IRT-4M gaps decrease to 1.85 mm, then the water velocity in them will decrease by only 5% as compared with IRT-3M.The development in 1963 of tubular fuel elements with a square cross section for the IRT subsequently continued to improve. Initially, the IRT-M fuel assemblies consisted of three tubes [1]. The fabrication of four-tube IRT-2M fuel assemblies was perfected in 1968 [2]. The IRT-3M fuel assemblies for pool and tank IRT and VVR-S research reactors were developed by 1979 to replace IRT-2M fuel assemblies with fuel assemblies having an extended heat-emission surface [3]. These fuel assemblies with 90% fuel enrichment were first used as regular assemblies in the IR-8 at the Kurchatov Institute in 1981 and subsequently in the IRT at the Moscow Engineering-Physics Institute (MIFI) and IRT-T in Tomsk. Later, a modification of these assemblies was developed with fuel enrichment 36%, which started to be used in VVR-SM in Tashkent [4].IRT-4M fuel assemblies with 19.7% enrichment were developed because it was necessary to lower the fuel enrichment for research reactors [5]. These fuel assemblies are similar to the IRT-3M fuel assemblies, but their fuel elements and kernels are thicker and the gap between the fuel elements is smaller. The development work was completed in 2004. The IRT-4M fuel assemblies started to be used in VVR-SM, IRT-1, and VR-1 in Uzbekistan, Libya, and Czechoslovakia, respectively.In 1973, experiments to determine the water velocity in the gaps between fuel elements as a function of the pressure differential in IRT-2M fuel assemblies were performed at the Kurchatov Institute [6]. In 1978, similar experiments were performed for IRT-3M fuel assemblies. In the process of developing the IRT-4M fuel assemblies, comparative hydraulic calculations were performed for IRT-3M and -4M; these calculations permitted making a final choice of the IRT-4M gap and to determine the hydraulic characteristics. These experiments and calculations are described in the present article.Description of the Geometry. The IRT-2M, -3M, and -4M fuel assemblies consist of coaxial tubular fuel elements with a square cross section with rounded corners, secured on the top and bottom end pieces. Each fuel element is three-layered and consists of a kernel and cladding. The kernel is 600 mm long an...
The aim of the paper is to obtain a unified finite element model of a complex process, which makes it possible to obtain visual information related to the influence of the welding process parameters on the results of the process of wave strain hardening of the weld material. Modeling of sequentially executed technological processes of different physical nature - welding and hardening, makes it possible to obtain more general and objective visual information about the process as a whole. Modeling in the Ansys software package is performed in stages, with the output of an earlier stage of modeling acting as the input data of the subsequent stage. At the first stage, the problem of visualizing the process of forming a weld is solved with the possibility of calculating temperature fields, stress and strain fields during heating and cooling of the welded workpiece. At the second stage, the calculated data is imported into the finite element model of processing welds with a deformation wave. A finite element model makes it possible to build microhardness maps for selected (dangerous) sections and visually monitor the change in stresses and strains in welded workpieces, depending on the technological modes of hardening by a deformation wave. The obtained visual information allows for a qualitative and quantitative assessment of the result of a complex process, which contributes to an increase in the bearing capacity and performance of the product as a whole.
The article presents results of study possibility of hardening of high-manganese steel X120Mn12 by a deformation wave in the process of wave strain hardening (WSH). Features of the method is possibility of using shock waves for plastic deformation, which significantly expands the technological capabilities for formation of a hardened surface layer. The dominant design and technological parameters of the hardening treatment are established, which have the main influence on the microstructure and hardness of the hardened surface layer. Possibility of a significant increase in hardness and depth of hardened surface layer is established. The depth of hardened layer can reach 6-8 mm, and the hardness can be increased by more than three times. Microstructural analysis showed no cracks. The obtained results of conducted research can be used to develop a technology for strengthening the deformation wave of various heavy-loaded parts made of high-manganese steel.
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