CPU time reduction strategies for the Lambda modes calculation of a nuclear power reactor

In this paper, we present two strategies to reduce the CPU time spent in the lambda modes calculation for a realistic nuclear power reactor.The discretization of the multigroup neutron diffusion equation has been made using a nodal collocation method, solving the associated eigenvalue problem with two different techniques: the Subspace Iteration Method and Arnoldi's Method. CPU time reduction is based on a coarse grain parallelization approach together with a multistep algorithm to initialize adequately the solution. (author). 9 refs., 6 tabs