MCNP full-core modeling of the advanced test reactor

A full-core Monte Carlo neutron and photon (MCNP) transport model has been completed for the advanced test reactor (ATR) at Idaho National Engineering Laboratory. This new model is a complete three-dimensional model that represents fuel elements, core structures, and target regions in adequate detail. The model can be used in evaluating heating and reaction rates in various target regions of the core. This model is especially useful in physics analysis of an asymmetric experiment loading in the core. The ATR is a light-water-cooled thermal reactor with aluminum/uranium-aluminide fuel plates grouped in arcuate fuel elements that form a serpentine arrangement, as shown in Fig. 1. The core is surrounded by a beryllium reflector. Nine test loops are nestled in the lobes of the serpentine core, and numerous other irradiation holes with varying dimensions and radiation environments are located in the reflector and in the core interior