Application of the Coordinate Transformation in Nodal Diffusion Calculations of Radially Expanding SFR Cores

In this study, the coordinate transformation technique was assessed for radial expansion of Sodium cooled Fast Reactor (SFR) cores with the focus on time-dependent calculations. This method was implemented into nodal diffusion code DYN3D and was tested against the already available direct mesh expansion model. The newly implemented method was tested for uniform radial core expansion cases. Within DYN3D, the coordinate transformation method was verified on steady-state cases and was validated on one of the transient scenarios from the Phenix reactor experiments. The obtained results demonstrate equivalence between the coordinate transformation and direct mesh expansion techniques and therefore presenting the viability of the former one in transient calculations of SFR cores.