Application of the Discrete Ordinates Adjoint Function to Accelerate Monte Carlo Reactor Cavity Dosimetry Calculations

The deterministic adjoint function is employed to accelerate Monte Carlo reactor cavity dosimetry calculations. Equations for calculating source biasing parameters and weight window lower bounds based on contribution to detector response are developed. The facilities to calculate and use these parameters have been incorporated into the MCNP code. Use of the adjoint function is shown to increase the calculational efficiency of the reaction rate calculation by more than a factor of 4 and improve the statistical convergence with respect to our best manually optimized model. Further the use of the adjoint function does not require the intuition, guess work, and/or iterative process typical of current variance reduction techniques.