Abstract: An analytical determination of the concentration of admixed component in the product and waste streams of a multistream cascade separating a multicomponent isotopic mixture is examined. It is proposed that the solution of the systems of differential equations describing the variation in the concentration of the components of a mixture over the steps assuming the enrichment effects to be small be used. The general approach to obtaining analytical relations for the evaluations is shown for the example of cascades with several feed and product streams. Calculations of uranium cascades are performed, showing good agreement between the analytical determinations and the numerical calculations for the separation of natural and waste depleted uranium hexafluoride obtained from regenerated uranium. PubDate: 2015-08-14

Abstract: A comparative study is made of the properties of six types of carboxyl cationites differing by the composition and structure of the matrix. It is shown that the use of weakly acidic ionites as the charge in the upstream filters in the special water purification system and block desalination setups will make it possible to extract very efficiently the lithium, potassium, ammonium or monoethanolamine ballast salts from the purified flows with dealkalization of the flows. As a result, the effective capacity of the regular filters can be increased considerably and, correspondingly, their service life extended by decreasing the volume and salt content of the secondary liquid radioactive wastes. PubDate: 2015-08-14

Abstract: Methods for modeling the coagulation in an aerosol code developed for calculating the behavior of multicomponent aerosols are examined. A comparative analysis is made and the methods are tested on model problems for conditions characterizing the formation of aerosols of fission products in the first loop of VVER during an accident with depressurization of fuel elements. PubDate: 2015-08-14

Abstract: The results of computational studies of the possibility of using beryllium reflectors to improve the neutronphysical characteristics of the VVR-Ts reactor, which is used at the Karpov Research Institute of Physical Chemistry to produce radionuclides, are presented. The calculations showed that in principle beryllium can be used by substituting it for some number of standard fuel assemblies. This made it possible to decrease the number of fuel assemblies from 70 in the standard core to 59 in a modified core and increase the run time to 14 days. The calculations also indicate that the neutron flux density in the experimental channels can be increased significantly, which is important for increasing the production of radionuclides. The
hermophysical aspects of the modified core are not studied. PubDate: 2015-08-14

Abstract: The possibilities of early detection of serious accidents at NPPs by using passive microwave radiolocation are discussed. Estimates of the brightness and antenna temperature of a partially ionized cloud created by the first emission of γ-radiation from the Chernobyl NPP are presented. It is shown that the microwave radiation can be detected by means of modern radiometers placed in low-flying satellites and airplanes as well as on stationary ground-based platforms. PubDate: 2015-08-14

Abstract: It is shown experimentally that the resistance to mass transfer during the rectification of mixtures of uranium hexafluoride with tungsten and molybdenum hexafluoride is mostly due to the liquid phase. It is recommended that the equivalent diameter of the packing be used as the linear size when calculating the criterional equations for mass transfer. PubDate: 2015-08-14

Abstract: A water technology developed at the Institute of Physics and Power Engineering was used to obtain and investigate the composition Eu2O3 + MgO – a simulator of the oxide fuel Am2O3 + MgO, intended for burning americium. This technology includes the production of precipitate containing particles of different size simultaneously, including nanoparticles, followed by heat-treatment, pressing, and sintering. The composition has a special structure (nanoporosity in grains, europium oxide clusters of substoichiometric composition with the metallic bond Eu–Eu) that promotes high thermal conductivity. Increasing the thermal conductivity of the fuel will lower the temperature at the center of the fuel upon irradiation, which will increase the fuel burnup and the operational safety of the reactor, and make operation in the maneuvering regimes possible. PubDate: 2015-08-11

Abstract: A comparative experimental study is performed of the lasing characteristics of a laser operating on the 2.03 μm transition of atomic xenon with direct, uranium fission fragment, pumping of the active medium in the form of a mixture of the gases He, Ar, and Xe in cylindrical active elements of two types, differing by the diameter and thickness of the uranium coating. It is shown that a three-fold reduction of the diameter and coating thickness of the active element results in a 1.5-fold increase of the laser efficiency in terms of energy. One possible explanation of this effect is examined: a source of internal losses of laser radiation present in the active medium due to scattering by radial acoustic gas-density waves excited by the pump pulse. PubDate: 2015-08-11

Abstract: The maximum temperature of fuel-element cladding in VVER-SKD reactors, where a triangular lattice with relative spacing x = 1.1 is used, can be determined using known relations, since the Prandtl number Pr ~ 1 for superheated steam at supercritical pressure. PubDate: 2015-08-11

Abstract: The aim of this work is to validate the electrochemical model of the dissolution of uranium nitride in nitric acid. It is shown that uranium nitride dissolution in water solutions of HNO3 can be explained by the presence of electrochemical processes which are interrelated but proceed separately: UN dissolution at the anode, subsequent chemical decomposition of UN in the space near the anode, and oxidation of HNO3 at the cathode. The proposed model explains the isotopic composition and ratio of the products formed in the gas phase. The mechanism of the process of uranium nitride dissolution in nitric acid can be described by the total reaction 6UN + 25HNO3 → 6UO2(NO3)2 + 3NH3 + N2 + N2O + 6NO + 6NO2 + 8H2O. PubDate: 2015-08-11

Abstract: Highly detailed computational models of the reactors in the Nos. 2 and 3 units at the Rostov NPP and the No. 3 unit at the Tianwan NPP (China) with the first fuel load are briefly described. Calculations of two states of the reactors were performed with the MCU code, implementing the Monte Carlo method, for each model: at the lowest controllable power and at nominal power. A TPA thermophysical module connected to the MCU code was used to take account of feedbacks in calculating the state of the reactor at nominal power. Analysis of the results obtained using the MCU and BIPR-7A codes showed agreement between the main characteristics of the reactor facilities. PubDate: 2015-08-11

Abstract: A method of direct numerical modeling of turbulent flows in the elements of nuclear power setups using a supercomputer is being developed at the Institute of Problems in the Safe Development of Nuclear Energy. The method is based on developed low numerical diffusion algorithms for which discrete approximations are constructed using finite-volume and completely separated grid methods. A regularized nonlinear monotonic operator separation scheme has been developed for solving the advection problem. Richardson’s iteration method with a preconditioner (i.e., a special matrix, premultiplication by which improves the convergence of the numerical method) in the form of the fast Fourier transform for the Laplace operator is used to solve the pressure equation. This approach to solving elliptic equations with variable coefficients gives multifold acceleration compared with the ordinary method of conjugate gradients. Quasi-direct numerical modeling is used to model the three-dimensional turbulent flows in single-phase flows. The method is implemented in the CONV-3D code, which is parallelized and efficient on the multiprocessor cluster computers Chebyshev and Lomonosov (Moscow State University). PubDate: 2015-08-11

Abstract: A variant of a fuel load for burning power-grade plutonium in VVER is examined. Using power-grade plutonium in fuel elements without the raw isotope makes it possible to increase its power potential almost 1.5-fold compared with the conventional mixed fuel and eliminates the need for repeated processing of the spent fuel obtained when plutonium is burned. PubDate: 2015-08-05

Abstract: The latitude distribution of the 137Cs concentration in the surface waters of the Atlantic Ocean on the section from the North Sea to Montevideo in September–October 2013 is investigated. The data obtained are compared with the investigations of the distribution of its concentration in close transatlantic sections in 1992 and 2002. The effective half–removal times from the surface layer of the waters in the northern (45–15° N) and central (15° N – 30° S) latitude zone of the Atlantic Ocean are determined to be 15.4 ± 4.6 yr and 12.3 ± 1.6 yr, respectively. Approximate exponential expressions for predicting the multiyear changes in the 137Cs concentration in the surface waters of the northern and central zones of the Atlantic Ocean are proposed. PubDate: 2015-08-05

Abstract: A seismic qualification database being developed on the basis of proper experience and a large volume of results obtained in previous works (more than 5000 pieces of inspected equipment) can increase the efficacy of computational-experimental evaluation of the seismic resistance of the equipment in commissioned power-generating units at NPPs and power units with extended service-life. The set of parameters to be included in the database and the structure of the database were determined on the basis of previously developed criteria and methods of reducing the labor intensiveness of the computational-experimental evaluation of the seismic resistance of the equipment in NPPs. The database can be used to systematize and colligate the results of computational-experimental examinations and to evaluate the seismic resistance of equipment by indirect methods. PubDate: 2015-08-05

Abstract: It is shown on the basis of an analysis of regulatory-legal documents that the assumptions characterizing very low-level wastes contain semantic contradictions and critical discrepancies of a classification nature regarding wastes containing natural radionuclides and are not consistent with the absolute values of the bounding indices – the dose rates and specific activity. The presence of these uncertainties and inconsistencies in the regulatory documentation makes reaching the primary objective of introducing very low-level wastes as a category – reduction of the cost of managing wastes by lowering the requirements for their isolation – problematic. Some variants of the elimination of normalization shortfalls are proposed. PubDate: 2015-08-05

Abstract: Constant monitoring of the state of the core ensures safe operation of a nuclear reactor. This article examines the reconstruction of the energy release in the core of a nuclear reactor on the basis of the indications of height sensors. Situations where some sensors fail are not rare. Any reduction in the number of sensor indications increases the error. However, the missing measurement information can be reconstructed by mathematical methods, and replacement of the failed sensors can be avoided. The simplest algorithm for reconstruction missing indications consists in approximating the height distribution by harmonic functions. However, the coefficients of these functions are found to be correlated. It is suggested that a set of natural functions determined by means of statistical estimates obtained from archival data be constructed. The procedure proposed makes it possible to reconstruct the field even with a significant loss of measurement information. PubDate: 2015-08-05

Abstract: Models of an aerosol module intended for calculating the formation and evolution of aerosol particles of fission products in the first loop of VVER in the case of a serious accident with emission of fission products from damaged fuel elements into the coolant are described. The characteristic features of the module are modeling of the nucleation kinetics of aerosols in the classical approximation, nonequilibrium condensation of the vapors of the fission products, fuel, and components of the reactor structures, and the method for calculating the coagulation of multicomponent aerosols. PubDate: 2015-07-01