A new, versatile iteration algorithm for the analytic nodal method

A new outer (source) iteration algorithm for numerical solution of the discretised equations of the Analytic Nodal Method is proposed. This new algorithm is obtained by re-arranging terms in the source iteration equations of the more traditionally used Fission Source Iteration (FSI) method. The new Transverse Leakage Source Iteration (TLSI) algorithm is characterised by the fact that the outer iterations are driven by the nodal transverse leakage sources only. The TLSI method appears to have a number of advantages over the Fission Source Iteration method in which Wielandt's Eigenvalue Shifting (FIS-WES) has been implemented to enhance the rate of convergence: It is computationally competitive without the need for any convergence acceleration parameters; it displays rapid outer iteration convergence properties, and in the initial stages of iteration the maximum assembly (relative) power error behaviour is monotonic, as opposed to the oscillatory behaviour of this parameter for the FIS-WES combination. As a result of these convergence properties, the TLSI method may have application in a wide variety of reactor calculation types ranging from benchmarking to survey and scoping applications. The rapid, monotonic convergence behaviour suggests that the method will be useful for scoping calculations since the speed and (reduced) accuracy requirements can be met by limiting the number of outer interactions to 2 or 3 only instead of introducing further approximations into the nodal equations themselves. (orig.)