COSTANZA-XE, 2-D Pebble-Bed or Prismatic Fuel Elements HTR Dynamic in Cylindrical Geometry

1 - Nature of physical problem solved: Two-dimensional reactor dynamics in cylindrical geometry. The code is especially designed for high temperature pebble bed reactors or for reactors with prismatic elements. Optionally it can be used for the study of fast transients or for slow operational transients with xenon variation. 2 - Method of solution: The neutronics uses a Krouk-Nicolson method, with direct solution along the radii for both energy groups, and Gauss-Seidel iterative method in axial (z) direction. The thermohydraulics is solved separately for each channel in two dimensions. The system of heat balance equations is solved with a direct method at each axial level. The solution obtained at the level (i) is used as boundary condition for the level (i+1). 3 - Restrictions on the complexity of the problem: Two energy groups, six groups of delayed neutrons. The maximum number of mesh points is 350