Multilevel methods to solve the neutron diffusion equation

In this paper, we develop multilevel strategies to solve the time dependent neutron diffusion equation. These methodologies are based on the discretiz ation of the spatial part of the neutron diffusion equation using a nodal c ollocation method which makes use of an expansion of the neutron flux in te rms of Legendre polynomials. The different levels or grids of the multileve l strategies have been defined in terms of the different number of polynomi als used for the nodal collocation method expansions instead of using diffe rent nodalization sizes. Results for two transients associated with the bid imensional TWIGL reactor are reported. (C) 2001 Elsevier Science Inc. All r ights reserved.