Vol 122, No 2 (2017)

The parameters of a mathematical model of power feedback are evaluated on the basis of an analysis of transient power processes arising in the IBR-2M reactor as a result of intentional square oscillations of the reactivity during operation in a self-regulation regime. The power feedback is described by three linear difference equations and represented in the form of three aperiodic elements connected in parallel. Two components play the role of negative and one component positive feedback. The total feedback is negative, i.e., it has a stabilizing effect on the operation of the reactor. The slowest negative component of power feedback is probably due to axial swelling of the fuel as it heats up. Since the power feedback parameters change in the course of operation, their periodically repeated evaluations are one way of securing the operational safety and reliability of the reactor.

A comparative analysis of ore-bearing rock in the Zavitinskoe and Ermakovskoe deposits is made. Such an analysis is needed because of the requirements of working with ore-mining concentrates, which model the basic physical and chemical parameters of beryllium-containing concentrates that influence their preparation efficiency and subsequent opening with reagents. It was found that it is possible to develop a general model system for the chemical and physical behavior of lithium and beryllium ore minerals and the bearing rock in the Ermakovskoe and Zavitinskoe deposits. Ore materials in the Zavitinskoe deposit (lithium association) model the physicochemical behavior of beryllium-containing ore minerals in the Ermakovskoe deposit (beryllium association).

The effect of low-temperature damaging irradiation on the high-temperature embrittlement (cold shortness) in metals was investigated in a previously proposed model. The cold shortness state with possible brittle fracture in metals is not formed in the irradiation process because of the dynamical radiation processes arising.

The VIZART software for computer modeling of production operations in the reprocessing of spent nuclear fuel, fabrication of nuclear fuel, and management of radioactive wastes was developed as part of the work on the complex technology of closed NFC. It makes it possible to develop models of process schemes or individual operations and perform supporting balance calculations of material flows of the prescribed schemes. A functional for calculating the material balance of products in a scheme taking account of the equipment productivity and constructing sequence diagrams of equipment operation was developed. The presented software, unlike most general-chemical simulators, makes it possible to calculate the characteristics of products which are specific for radiochemical processes: the isotopic composition and its variation during reprocessing, radioactivity, and heat release. These characteristics are important for validating the design and structural solutions from the standpoint of nuclear and fire-explosion safety.

A method of modeling the transport of electrons and positrons with energies 1 keV–10 MeV implemented in the FAN15 code is described. The code takes account of multiple Coulomb scattering, fl uctuations of ionization losses, formation of δ-electrons, and Bremsstrahlung and x-ray photons. The EEDL and EADL evaluated data libraries are used in the calculations of Bremsstrahlung and emission of x-ray photons upon relaxation of ionized atoms. The computational results are compared with the experimental data on the energy, angular, and dose distributions of 0.5–10 MeV electrons in different absorbers.

The impact of temporary storage sites for radioactive wastes in Guba Andreeva on the environmental conditions in the coastal zone of the Barents Sea after 50 years of operation is evaluated on the basis of general chronological reconstruction of the dynamics of radioactive contamination of the marine environment. The bottom deposits along the seacoast at different distances from the repository were investigated. It was found that the region of constant impact of the repository on the conditions in the marine environment is localized near the perimeter of the sanitary-protective zone. Growth of the specific activity of ¹³⁷Cs, ⁹⁰Sr, ²³⁸Pu, ^239,240Pu is recorded in sediments layers up to the level 16–20 cm. The impact of the emission of radionuclides from the repository site is not perceptible in the seacoast zone (Motovskii Zaliv). The age of the sedimentary layers was determined: it shows that the significant concentration of ¹³⁷Cs in the deposits in Motovskii Zaliv corresponds to the mid-1960s and 1986 and is associated with atmospheric fallout of radionuclides as a result of the nuclear weapons tests and the accident at the Chernobyl NPP.