Results 1 - 10 of 563
Results 1 - 10 of 563. Search took: 0.021 seconds
|Sort by: date | relevance|
[en] The radionuclide 99Mo was produced and separated in the process of irradiating powdered mixtures of molybdenum compounds and buffer particles by 30 MeV protons. The separation is based on the Szilard–Chalmers effect wherein 99Mo recoil particles are fixed in inert buffer particles. Two types of targets were investigated by using mixtures: soluble molybdenum compound–insoluble buffer and insoluble molybdenum compound–soluble buffer. 99Mo yield equal to 20% with enrichment coefficient 18.3 was obtained by using a target consisting of a mixture of submicron 100MoO3 and Al2O3 particles; the 99Mo yield was equal to 20% and the enrichment coefficient 18.3. For a target with the composition 100MoS2 + KCl, making it possible to separate 99Mo recoil atoms directly into solution, the 99Mo yield was equal to 8.7% and the enrichment coefficient 30.7.
[en] The maximum graphite temperature upon increasing the reactor power in the No. 1 unit of the Leningradskaya NPP to 80% of the nominal value in November–December 2013 after the restoration of the service life characteristics of the graphite stack is presented. A comparative analysis is made of the temperature regime of the graphite stack at power equal to 80 and 100% of nominal value before and after restoration of the service life characteristics at nominal helium content in the gas mixture blown through the reactor space. A comparison is made of the maximum temperature of the graphite stack of the reactors in the No. 1 unit of the Leningradskaya NPP and No. 2 unit of the Kursk NPP upon startup and assimilation of the power after restoration of the service life characteristics. The effect of the restoration of the service life characteristics on the thermohydraulic regime of the fuel channels in the reactor is studied.
[en] Research building B at the Bochvar High-Technology Research Institute for Inorganic Materials (VNIINM) located within the city limits of a dense residential development was decommissioned in 2013–2015. Radioactively contaminated equipment and utility services were disassembled and removed, building structures were decontaminated, the framework was dismantled, the grounds of the development site were restored, and radioactive waste was transferred to specialized organizations. The framework was liquidated in strict accord with the norms and regulations governing the use of atomic energy.
[en] An approach to the comparative assessment of the impact of accidental radioactive emissions on the biota and radioecological validation of nuclear fuel cycle objects is presented. It is shown that the dose loads on woody tier in a coniferous forest as a result of severe accidents in NPPs with PWR-890, BWR-1412, and EPR-1600 significantly exceed the limit recommended by the ICRP. The impact of the radiation factor can result in serious disturbances in forest ecosystems in the immediate vicinity of NPPs.
[en] The main results of tests performed on VVER-1000 fuel elements with high burnup of fuel in a channel of the MIR channel reactor for LOC accident conditions are examined. The experimental setup contains one fuel element, which is arranged along the central axis. The aim of the tests is to determine the parameters of cladding depressurization. In the experiment, questions concerning fragmentation, axial displacement, and possible escape of fuel to outside the cladding were studied and the properties of the cladding material and fuel, which were subjected to the extreme parameters, were determined. The main parameters and the results of two experiments are presented. The conditions under which fuel-element depressurization occurred are determined.
[en] A linear-algebraic form of the equations of the method of characteristics, which is used to approximate the neutron transport equation, is obtained. It is shown on the basis of the obtained linear-algebraic form that the discrete form of the conjugate equation differs from the algebraically discrete problem constructed by linear-algebraic transformations of the discrete form of the normal problem. The reason for the discrepancy lies in the approximation of the volumes of the spatial cells in covering the working region by a network of characteristics. It is shown by means of test calculations that when the network of characteristics is refined the solution of the conjugate transport equation converges to the solution of the algebraically conjugate problem.
[en] The gas-phase conversion of UN and UC into water-soluble compounds in the atmosphere NOx–H2O (vapor)–air and HNO3 (vapor)–air in the interval 298–423 K was investigated. It is shown that in the gasphase conversion process UN is converted into water-soluble compounds (nitrates, hydroxy nitrates). It is found that the gas-phase conversion of UN in the atmosphere NOx–H2O (vapor)–air is less efficient than in the atmosphere HNO3 (vapor)–air. In the process of gas-phase conversion of UC in a nitrating atmosphere the main products of conversion are uranyl nitrate hydrates. In addition, carbon-containing products are formed and their removal requires ozonation of the solutions formed as a result of contact between water and the products of UC conversion.
[en] The current trend in neutron-aided scientific research presupposes the development of new high-intensity pulsed sources. One variant of such an installation could be a pulsed reactor with a fissile-isotope core – 237Np. The present work is devoted to a study of the dynamics of power pulses of a neptunium reactor taking account of fast temperature feedback during pulse buildup. The problem is reduced to a simple model of a single frequency oscillator combined with the equation of single point kinetics of a reactor neglecting delayed neutrons. It is shown that on the basis of such an approximation, owing to feedback on the temperature of a fuel element the estimated energy of accidental power pulses decreases by almost a factor of 10 compared with a calculation neglecting fast feedback.
[en] The possible consequences of flooding of nuclear and radiation-hazardous sites and objects should be included among the environmental risks arising during the rapid development of the infrastructure in the Arctic. A mathematical model, algorithms, and software codes for evaluating the condition and predicting the collapse of the protective barriers, and determining the emission rate of radionuclides and the possible radioactive contamination of the environment, including long-term prediction and situation analysis, have been developed. The software codes have been accepted into the government registry at Rospatent.