A modal analysis of free-surface and internal gravity waves in a fast-reactor hot pool

Abstract This paper follows the classical approach and presents a linear, inviscid, free-mode analysis of a stratified fluid in a prismatic tank consisting of an eccentric above-core structure (ACS) as well as four pump pods and eight intermediate heat exchanger (IHX) standpipes. The prismatic geometry (i.e. the horizontal cross-section is independent of the vertical position) implies a decoupling of the mathematics governing variations in the horizontal and vertical planes; the latter depends only on the vertical density profile and provides the dispersion relation between frequency and eigenwavenumber. After exploiting the analogy between the horizontal-plane problem and acoustic vibrations in a rigid cavity, the modal shapes and eigenwavenumbers of the first seven modes are determined by employing acoustic elements in the BERDYNE finite-element structural dynamics code.