摘要
It is well known that fission product 135 Xe has a very large absorption for thermal neutrons. A small fraction of this nuclear species is formed directly in fission and a major part results from the decay of 135 I. The behavior of 135 Xe density can affect neutron flux distribution and hence reactor operation in a thermal reactor. The aim of this paper is to give a nonlinear study of time dependent multigroup diffusion equations coupled with Xe feedback through the notion of the upper-lower solution and the monotone iterative method. The study includes the construction of neutron flux, explicitly upper and lower bounds of the neutron flux, and the asymptotic behavior of neutron flux under Xe feedback. Finally, we also obtain sufficient conditions for supercriticality and subcriticality of the coupled system. © 1990.