Annual report for contract year 1969. Supporting research and technology, Project 493

Advances in the methods for neutronic and radiation design of NERVA are described.The transport code DOT-IIW was improved in the acceleration of convergence, handling of boundary conditions and tape operations, and extensively tested for flux and eigenvalue convergence at different orders of quadrature and in r,0 geometry.Satellite codes for preparation of cross sections, and geometry were developed.Reduction of ray effects through Lagrangian interpolation in discrete ordinate fluxes was ochieved.Improvements in two-dimensional perturbation code were made.