A Three Dimensional investigation of Xenon and temperature transients

The Paper describes the development of a Three Dimensional Xenon and temperature feedback transient code for Advanced Gas Cooled Reactors. This has been based on a standard UK Three Dimensional Fuel Management code which has all the necessary irradiation and flux restart options so that transients can be followed at any point in the reactors' life history. It incorporates both a conventional eigenvalue calculation and some rather novel flux solution techniques e.g. to shape the radial power distribution by means of the stainless steel 'grey' rods to yield a desired macroscopic shape. Detailed solution of the Xenon and Iodine number densities is performed by a Runge-Kutta integration routine while the fuel and moderator temperatures including re-entrant flow are modelled by newly developed procedures which are fast yet accurate. Results for several transients will be presented in the paper together with comparisons with simpler one dimensional models