Current trends in multidimensional static reactor calculations

The more recent attempts to formulate alternatives to the classical finite difference method for solving large three-dimensional reactor problems are discussed in some detail. A number of higher order coarse mesh methods are described that allow the solving of global 3D-reactor problems accurately and efficiently on a routine basis. The present status of the finite element methods is then reviewed briefly. An attempt is made to evaluate the further potential of FEM for application to realistic multidimensional reactor problems. Results of numerical comparison studies are presented that show the promise of consistent nodal methods to give an optimal balance with respect to accuracy and efficiency. Special consideration is given also to new aspects that arise if coarse mesh methods are applied for practical reactor design calculations. It is shown that accurate predictions of local quantities may be obtained by solving detailed fine-mesh problems imbedded in a converged global solution. Finally, some more general aspects of multidimensional flux synthesis methods are discussed. Improvements may be expected by using more flexible schemes of trial function generation and applying overlapping multichannel synthesis methods. (65 references) (U.S.)