[en] A solution of one-dimensional nonstationary equation of neutron transport by the Laplace transformation method is presented. It is shown that when the indicatrix of neutron scattering is presented in the form of a sum of monotonous and delta-shape parts of the equations which depends stepwisely on time, highest discrete values conditioned by the existence of pseudoasymptotic neutron distributions are observed in the spectrum of equation intrinsic values in addition to the main asymptotic one. Calculational and experimental results obtained for a small-size reactor with beryllium reflector are presented to illustrate the given theory. 5 refs.; 3 figs

[en] Application possibility for mechanism of magnetic field effect on neutron scattering to modulate reactivity of a nuclear reactor is estimated. Slow neutron interaction with ferromagnetic materials is considered. Layout of reactor with reactivity magnetic modulation is described

[en] Problems, related to numerical solution of neutron kinetics equation by analysis of emergency situations at nuclear reactors are discussed. The possibility of applying density drop curves, obtained in pulse experiments in a critical assembly, for determination of kinetics differential equation coefficients in three-group approximation

[en] The possibilities of the QTRAD code for calculating the radioactive fission products yield (RFP) from the nonhermetic fuel elements of the reactors with the heavy coolant are described. This code is based on the complicated model of the RFP transport from the place of their formation up to the place of their yield from the damaged fuel element shell into the primary circuit. The test calculations, relative to the QTRAD code, showed, that the obtained results are in agreement with the experiments and calculations by other programs

[en] The simple kinetic models applicability investigation for describing pulse experiments in fast reactors with slowing down moderators is performed. Spatial and time neutron flux distribution of various energy groups in the field of higher harmonics and in the asymptotic region is analyzed. The neutron flux is presented in the form of a series of eigenfunctions of a homogeneous equation for neutron flux which comprises as eigenvalues damping factors. On the base of the analysis a simplified two-region two-group kinetics model of reactors of the above class is suggested. It is shown that using this model permits to correctly interpret pulse experiments conducted in fast berrilium moderated reactors by means of the threshold neutron detector

[en] The traditional version of the α method is based on a point one-group kinetic model of reactivity. In fast reactors with a moderating reflector this method is inapplicable because of the strong dependence of the neutron generation time in the region of asymptotic neutron flux decay on the subcriticality. In this paper the authors modify the alpha method to a two-group point kinetic model with a corresponding modification of the measurement procedure in order to extend the method to this class of reactors. The modifications are tested against experimental results of pulsed investigations on a BFS-40 fast critical pile with a beryllium reflector

[en] Based on the reactor kinetics two-group point model an expression for reactivity is derived, in which in contrast to expression, used in traditional pulsed α-method for measuring reactivity, correction coefficient is present. This coeffisient is determined experimentally by recording the time distribution of two energy harmonics instead of one asymptotic harmonic, as it is performed in the classical α-method. For this purpose threshold neutron detectors are applied. Experimental testing of the modification proposed in a fast reactor with beryllium reflector has shown the possibility of its application up to subcriticalities-9 β_eff

[en] To study regularities of appearance and range of existence for a discrete set of higher harmonics the experimental and calculational studies of non-stationary neutron distribution in the BFS-40 critical assembly are performed. Neutron pulsed method is used as the experimental one. Calculations of the higher harmonics damping decrements are made using the MMKFK program complex. As a result of experimental studies three energy harmonics are separated. The same harmonics are obtained by calculations. The calculated and experimental results agree well. Theoretical interpretation of the results obtained is given. 14 refs.; 2 figs.; 3 tabs

[en] Experimental and calculational studies of non-stationary neutron distribution in the BFS-40 critical assembly are made in order to investigate laws of occurrence and existence range of neutron flux harmonics. Neutron pulsed method is used in the experiments. Calculations of the damping factors of higher harmonics are conducted using the MMKFK program complex. Three energy harmonics are separated as a result of experimental study. The same ones are obtained by means of calculations. Calculational and experimental results are in a good agreement

[en] The VVERRAD computer code for simulating the WWER reactor primary circuit coolant radioactivity taking into account the dynamics of fission product release from failed fuel elements under conditions of space distribution variations in their energy release, temperature and fuel physical-chemical properties is briefly described. The code applicability for simulating abrupt change in ¹³¹ I radioactivity in the case of local power release disturbance in the WWER-440 reactor core which takes place at core lifetime finish because of the central regulating element fast lowering is proved. It is shown that coolant radioactivity will be increased by the factor of 5 if failed fuel element is located near the absorber introduced