Authors & Affiliations

Gordeev S.S.1, Sorokin A.P.2, Denisova N.A.2
1 National Research Nuclear University “MEPhI”, Moscow, Russia
2 A.I. Leypunsky Institute for Physics and Power Engineering, Obninsk, Russia

Gordeev S.S. – graduate student, National Research Nuclear University "MEPHI". Contacts: 31, Kashirskoe shosse, Moscow, Russia, 115409. Tel.: +7(967) 179-20-80, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it..
Sorokin A.P. – Chief Researcher, Dr. Sci. (Tech.), A.I. Leypunsky Institute for Physics and Power Engineering.
Denisova N.A. – Leading Engineer, A.I. Leypunsky Institute for Physics and Power Engineering.

Abstract

The temperature regime of the core of fast neutron reactors close to the limiting one, the influence of a mass of factors, high demands on the thermophysical justification. The main factors are the distribution of geometric parameters, energy release, coolant flow, interchannel and inter-packet exchange intensity, uncertainty in the values of these parameters and their variation during reactor operation. Formation of the core during the campaign is complex. Along with systematic deviations of parameters, random deviations of parameters are observed. The available data allow us to describe the distribution of geometric parameters in the shape-modified fuel assemblies. To reduce the level and equalize the temperature unevenness, it is necessary to optimize the parameters of the peripheral zone. The deformation of the displacers determines the temperature conditions of the peripheral fuel rods, which are close to the case of the geometry of a compact beam. Formation of fuel rods and fuel bundles during the campaign can be one of the most significant factors in the formation of the temperature field in fuel assemblies. Typical, including significant deformations of fuel assemblies in the process of the campaign in the core center area do not, as a rule, lead to an increase in the level fuel cladding temperature above 650°C, maximum azimuthal uneven fuel rod temperature above 100°C. Uneven energy release of fuel rods in the cross-section of fuel assemblies leads, as a rule, to an increase in the level of maximum fuel rod temperature and maximum azimuthal unevenness in the temperature of the fuel rods. Interpacket leakage of the coolant and inter-packet heat transfer cause a change in the temperature regime of peripheral fuel rods. Influence of the whole factors leads to overheating of the fuel cladding by 10–20 % of the heating of the coolant in the fuel assembly for nominal conditions and up to 50–100 % of the heating of the coolant in the fuel assembly for changes in fuel assemblies, which requires thermomechanical calculations. A significant factor in the formation of temperature fields in fuel assemblies is the interchannel exchange. The thermophysical justification of the operation modes of fuel assemblies of the reactor core on fast neutrons with a sodium coolant should be carried out taking into account changes in various parameters, primarily the formation of fuel assemblies during the campaign.

Keywords
fast reactor, campaign, sodium, active zone, fuel assembly, fuel rod, sheath, temperature, flow, factor, geometric parameters, energy release, shape-change, stochastic deviations of parameters, interchannel mixing, maximal temperature, temperature unevenness

Article Text (PDF, in Russian)

References

UDC 621.039;532.54

Problems of Atomic Science and Technology. Series: Nuclear and Reactor Constants", 2018, issue 3, 3:20