Ядерна фізика та енергетика Nuclear Physics and Atomic Energy   ISSN: 1818-331X (Print), 2074-0565 (Online)   Publisher: Institute for Nuclear Research of the National Academy of Sciences of Ukraine   Languages: Ukrainian, English   Periodicity: 4 times per year   Open access peer reviewed journal

Full text (ru)

V. M. Khotyayintsev¹, O. M. Khotyayintseva², A. V. Aksonov¹, V. M. Pavlovich<sup>2

1</sup>Taras Shevchenko National University, Kyiv, Ukraine
²Institute for Nuclear Research, National Academy of Sciences of Ukraine, Kyiv, Ukraine

Abstract: Stability of the stationary wave of nuclear burning in fast reactor with uranium-plutonium fuel chain is investigated. The reactor model including 1-D diffusion equation in one-group approximation for neutron flux density and kinetic equations for nuclear densities describes slow evolution of nuclear densities followed by neutron flux. New analytical approach was proposed, which is based on the approximation of small wave velocity of the stationary wave. We obtain so-called wave velocity characteristics of the reactor which is the dependence of wave velocity to the effective absorber concentration. We show that due to instability of long-living ²⁴¹Pu a turning point and lower branch of stationary solutions appear. Numerical solution of the time dependent problem proves that the solutions of the lower branch are unstable. Thus, the turning point of the velocity characteristics corresponds to the lower margin of possible wave velocities of nuclear fission waves of the steady shape. At the same time the solutions of the upper branch are stable with respect to slow evolution of nuclear densities.

Keywords: nuclear burning wave, inner safety, fast reactor, one-group approximation.

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