Abstract: A global variance reduction method is described.The method is based on a modified transport problem that can be solved by analog Monte Carlo with zero variance.It is developed by breaking up the whole into parts and coupling Monte Carlo method with discrete ordinates method and using approximate importance function to guide Monte Carlo simulation.Performance of the method for a one-dimensional sphere transport problem is demonstrated.The method is shown to produce lower variances globally compared to analog Monte Carlo.

Key words: Monte Carlo method, particle transport, discrete ordinate method, adjoint calculation, global variance reduction