ADVANTG is a software package that generates variance reduction parameters (space- and energy-dependent weight windows and biased source probabilities) that can substantially improve the convergence rate of fixed-source neutron and photon radiation transport simulations using MCNP. ADVANTG implements the Consistent Adjoint Driven Importance Sampling (CADIS) method to accelerate individual tallies and the Forward-Weighted CADIS (FW-CADIS) method to obtain nearly uniform statistical precision across multiple tallies and large mesh tallies. Additionally, ADVANTG 3.2.0 has the capability to produce variance reduction parameters based on the Multi Step CADIS (MS-CADIS) methodology for optimal calculations of delayed gamma radiation fields such as the shutdown dose rate (SDDR) in fusion facilities.

The workshop will discuss the theoretical background of the methods implemented in ADVANTG before moving on to a demonstration of the use of CADIS and FW-CADIS methods on test cases. The workshop will also include a tutorial on how to visualize the discretized geometry, source and discrete ordinates solutions using the open-source VisIt software (https://wci.llnl.gov/codes/visit/). Common issues when using variance reduction will be discussed alongside some best practices and suggestions for ADVANTG workflows.

ADVANTG has been used in a variety of radiation transport applications at ORNL as well as other organizations. Some recent advanced applications will be presented and discussed, including the use of ADVANTG for pressure vessel fluence predictions, neutron fluence and radiation heating in LWR concrete bioshields, and in the workflow for determining SDDR in the JET and ITER fusion facilities.