Shutdown dose rate analysis with unstructured tetrahedral element based R2S method using deterministic transport solver AETIUS

We have been developing an in-house deterministic neutron and gamma transport solver, AETIUS, which uses an unstructured tetrahedral mesh for spatial discretization such as Attila. We make the most of the spatial discretization of AETIUS for a shutdown dose rate analysis. This is similar to the MCR2S unstructured mesh method with the exception that the deterministic solver AETIUS is used for the neutron and gamma transport calculations instead of MCNP(X). AETIUS provides neutron spectra for every unstructured tetrahedral element belonging to the activation zones. Activation calculations are then carried out using FISPACT-2007, and the resulting gamma spectra of each element are used as decay gamma sources for the AETIUS gamma transport calculation to obtain a shutdown dose map. We calculated the shutdown dose rate on the ITER port plug computational benchmark, and our results are the most similar to those of the FDS R2S method.