[en] The method to retrieve the group-to-group transition cross sections depending on a scattering angle cosine is proposed. The method allows to take into account the fact, that for sufficiently fine group structure the cross section is not equal to zero in only a part of the (-1, 1) interval. The retrieved angular dependence may be used for evaluation of additional Legendre coefficients. 6 refs.; 5 figs.; 5 tabs

[en] The problem of adequate coolant mixing and flow pattern optimisation becomes more significant while considering pool type fast reactors. Within a vessel of this reactor type there are considerable bulks of coolant at different temperatures. Because of the complex design requirements certain difficulties exist in the problem of ensuring sufficient mixing of the coolant at the outlet of the core, radial blanket, in-pile fuel storage and in-pile neutron shielding. n the framework of the R and D activities carried out to justify fast reactor design solutions a proper attention is given to investigations of the coolant flow pattern within plena and in those sections of pool type reactor, where the coolant now takes place. In this connection It should be noted that, up to now, we did not obtain any clear evidence of the presence of a pronounced thermal stratification of sodium within reactor mixing chambers under normal operating conditions. The conclusion may be drawn on the basis of our experiments and design experience that there are certain gradients of temperature and Inefficient mixing of coolant flows with different temperatures within the chambers (both 'hot' and 'cold' ones). All these factors to a certain degree complicate a reactor operation. However, from our point of view, the main point in the problem of arranging an 'optimum' coolant flow pattern within the chambers is to insure the stability of coolant motion in the chambers (Including flows with different temperatures) by means ol special design solutions based on results of experimental and calculation studies. It is considered that the instability of coolant flow could be the most important factor influencing temperature distribution within structures and components. That is why coolant flow in all reactor chambers and cavities should be stable, including natural convection flows

[en] Configuration of the steam circuit is proposed for a nuclear power plant with a sodium-cooled reactor and with one or two sodium circuits. The steam circuit is provided with a reheater for steam taken off the turbine. Its inlet is connected to the hot side of the steam generator evaporating zone while its outlet is connected to the low temperature steam generator part. This configuration increases the nuclear reactor efficiency to 42%. (Z.M.)

[en] The results of the USA latest developments and investigation in the field of modular conceptions, passive protection and cooling systems for liquid metal cooled fast reactors are generalized. The modular conceptions correspond to a great extent to the present USA infrastructure: power engineering is in hand of private owned interprices, low rates of power growth, fear of a private owned sector to contribute a lot of means into high-power units due to the accidents taken place at NPPs. It is shown that under certain conditions (optimal core physical characteristics, structural and technological equipment construction chosen rationally) temperature increase in a reactor leads to vessel deformation, radial expansion of the core and fuel assembly bending, elongation of regulating rods and as a result to formation of negative resulting reactivity without the reactivity control. The control system serves to decrease reactor power to the values allowing to carry out reliable heat removal due to natural circulation of a coolant and air, being a final heat absorber

[en] Technical and economical characteristics of specific materials cousumption for the WWER-1000 reactor (the Novo-Voronezh-5 reactor) and BN-600 reactor (BNPP-3 reactor) are compared. Ways for decreasing specific materials consumptions and fast reactor cost are discussed. Specific technical and economical parameters and arrangement layouts of the RBMK channel reactors and those of thermal power plants with organic fuels are given for comparison. The data presented reveal that under comparable cQnditions (equal power, similar regions and construction periods) specific investments for NPPs with the BN-600 reactors turn to be by 30-50% higher than those for NPPs with the WWER-1000 reactors. Higher cost of equipment for the NPPs with fast reactors is explained by its larger nomenclature and increased metal consumprion. The BN-600 reactor proper has higher specific materials Consumption and higher cost, its specific materials consumption being 4 times as high as that of the WWER-1000 reactor. In-vessel thermal and neutron shields are most metal consuming elements of the BN-600 reactor (35% of total metal consumption) which cost makes up 20% of the total reactor cost. It is concluded that this difference in costs should be compensated by high-efficient fuel breeding in fast reactors

[en] Theoretical consideration of the problem on group representation of reactivity coefficient (RC) at the inhomogeneous reactor point has been carried out, basing on conception of group constants keeping reaction rate. A new approach to solving problem on group description of bilinear functionals caused by inhomogeneous perturbations has been developed. The approach consists in indicating special neutron distributions in a critical steady-state reactor, the distributions being called influence functions in the paper and directly conjugated to RC studied. Application of influence functions permits to bring the problem of RC group description in the point to the solution of equations of the moderation type. The result obtained gives the basis for solution of the followng practically important problems: firstly, the problem in estimation of traditional group method errors in calculation of bilinear functional of the RC type; secondly, the problem on preparation of group constants to carry out calculations of the perturbation theory

[en] The code system ZEMO for generating 26 group and 140-group constant sets for fast breeder reactors neutronics is considered. Group constant libraries, calculational techniques, formats of generated group constant sets and code control parameters are described. Results of one-dimensional model calculations for some critical assemblies and results of investigation of sodium void reactivity effect calculational error caused by 26-group approximation for two-dimensional model of BN-800 are presented. 14 refs.; 1 fig.; 3 tabs

[en] The state of developments of commercial fast reactors in industrially developed countries is described. The experience in experimental and demonstration fast reactor design is used as a foundation for the developments. Economic competative ability and maximum achievable safety are the main problems solved as applied to commercial reactors

[en] Results of recent investigation into creation of fast reactors with ultimate safety are considered in details. Two main directions of efforts are marked. The first one is linked with more comprehensive application of inherent-safety features and their improvement due to optimization of physicotechnical characteristics design solutions and fuel type. Safety provision passive factors are taken into account during development of perspective GN-800 and BN-1600 units

[en] The GRUKON-6 package of applied programs developed for recalculating the data on neutron cross sections into group constants is described. The programs are written in FORTRAN-4 and ASSEMBLER and are realized at the ES computer. The programs are also adapted for the ES-1060 and ES-1061 computers. 8 refs