  In this work, we expand the weighted delta-tracking routine to include a
treatment for scattering. The weighted delta-tracking routine adds survival
biasing to normal delta-tracking, improving problem figure of merit. In the
original formulation of this method, only absorption events were considered. We
have expanded the method to include scattering and investigated the method's
effectiveness with two test cases: a pressurized water reactor pin cell and a
fast reactor pin cell. We compare the figure of merit for calculating infinite
flux and total cross-section while incrementally changing the amount of
weighted delta-tracking used. We find that this new WDT routine has strong
potential to improve the efficiency of fast reactor calculations, and may be
useful for light water reactor calculations.

Computational Physics;Instrumentation and Detectors;Applications