Modelling of CANDU-SCWR Unit Cell With DRAGON: From Cartesian to Hexagonal Geometry

Abstract

A new hexagonal model of the Canadian supercritical water cooled reactor unit cell geometry is compared with the Cartesian model in DRAGON. This hexagonal model is considered for a compact core since further saving in the construction costs can be achieved by a reduction in the heavy water inventory in the core while still satisfying the constraints on the mechanical size of the pressure tube header. In our study, we investigate two options: using a reduced lattice pitch while preserving the same pressure tube; and increasing the outer radius of the pressure tube while using an hexagonal cell that has the same 2-D surface as the original Cartesian model. Preliminary results indicate that reactivity of the equivalent hexagonal unit cell is slightly lower than of the original Cartesian cell (0.3 mk). Reducing the lattice pitch of the hexagonal cell to that of the Cartesian cell decreases further the reactivity (20 mk) but reduces the moderator volume by more than 20 %. In the main paper, additional options for reducing the moderator volume will be considered, including an increase in the outer radius of the pressure tube, therefore replacing the moderator by super critical light water coolant.