We show that a Krylov iterative meihod, preconditioned with DSA, can be used to efficiently compute solutions to diffusive problems with discontinuities in material properties. We consider a lumped, linear discontinuous discretization of the S N transport equation with a 'partially consistent' DSA preconditioner. The Krylov method can be implemented in terms of the original S N source iteration coding with little modification. Results from numerical experiments show that replacing source iteration with a preconditioned Krylov method can efficiently solve problems that are virtually intractable with accelerated source iteration. Key Words: Krylov iterative methods, discrete ordinates, deterministic transport methods, diffusion synthetic acceleratio
