Analytical Estimation of the Central Reflector Impact on Thermal Neutron Flux Density in Research Reactors

Abstract

Abstract. In this research was shown an analytical assessment of the impact of the central reflector as an example of spherical reactor in one-group approximation. From the external reflector introduced an effective border that simplifies the mathematical problem of critical task. The validation of the research is done just for one of the IRT-T reactor conditions. Mathematical model and study techniqueIn the academic literature assessments of the impact of the central reflector is not given [1][2][3]. In some works a crucial problem was solved for planar geometry of the one-group, one-group modified [4] and in the diffusion-age approximation [6][7][8].It should be noted [1][2], that the inner central reflectors are used in the projects of research and power reactors to increase the thermal neutron flux and for the energy alignment on the core of a nuclear reactor. These results can be widely applied in practice, e.g. in solving the acute problem of central reflector masonry beryllium poisoning, (on the example of the IRT-T research reactor). The purpose of this research is to solve the critical problem as an example of a homogeneous spherical reactor with internal and external reflectors in the single-group approximation. To simplify the problem, is used the method of effective boundary conditions, following which from the outside of the reflector introduce efficient frontier R. Graphical interpretation is shown in Figure 1. Article available at

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“…Program of numerical calculations of two-dimensional and three-dimensional temperature fields very difficult [4,5]. Therefore, for an approximate estimation of the maximum temperature of the graphite is necessary to resort to various simplifications and assumptions.…”

Aspects of calculating the temperature for the graphite stack of the RBMK reactor

“…The programs for numerical calculations of two-dimensional and three-dimensional temperature field are very complex. Therefore, various simplifications and assumptions should be performed to estimate the maximum temperature of graphite [4,5].…”

Analytical estimation of the distribution of thermal neutron flow

“…More than half a century of nuclear reactor operating experience identified the reasonability using internal and external reflectors [1,6], also it's shown by previously researches [2,3]. E.g., in research reactor IRT-T using not only external but also internal reflectors can lead to increase of the average density of the neutron flow [4].…”