Enhanced Variance Reduction Capabilities in MCNPX-PoliMi

In the past several years, the MCNP-PoliMi code has been widely used for detailed simulation of detector response from organic scintillation detectors, particularly for correlated-particle measurement applications. Historically, all detector-response simulations performed using the MCNP-PoliMi code needed to be analog. This requirement creates a real limitation, particularly when simulating scenarios with large source-detector distances and/or large amounts of intervening shielding material. Last year, these MCNP-PoliMi capabilities have been released through the Radiation Safety Information Computational Center (RSICC) as a patch to the MCNPX code along with the associated detection postprocessor, MPPost. Since then, work has been underway to remove the analog-only requirement from MCNPX-PoliMi and MPPost simulations. The goal has been to allow MCNPX-PoliMi users access to all of the standard variance reduction capabilities of the MCNPX code. Results have been published for a few specific source-detector scenarios that show excellent agreement with measured data and significant speed-up compared to the usual analog simulations. In this work, the variance reduction options in MCNPX-PoliMi and MPPost will be expanded and demonstrated for a range of example scenarios, including cross-correlation measurements of a correlated neutron source. In addition, the MCNPX-PoliMi simulation results will be compared to measured data