Radio-species transport model for coupled fluid dynamics-neutron activation calculations.

• Water activation. • First Wall CFD models. • Turbulence and stagnation. • Distribution of residence times function. • ANSYS Fluent User Defined Scalars and User Defined Functions. A coupled methodological approach was developed for the modelling of fluid activation on ITER relevant components, using Computational Fluid Dynamics (CFD). Based on ANSYS Fluent's general transport mathematical model, built-in equations (UDS) were customized to represent radioactive species' activation and decay processes, fully embedded in fluid transport equations. Such model, so called Radioactive Species Transport Model (RSTM) was benchmarked against previous approaches on this field. Additionally, two applications relevant for ITER In-Vessel design are reported: (1) a complete FW06 and (2) a complete FW18 with its Shielding Block (SB18). These results provide new sensibility on the effects of flow stagnation and recirculation under real activation rate fields for In-Vessel components. This implementation shows that previous approaches may have overestimated the activation levels expected on downstream FWs by the order of 20–40%, depending on the characteristics of the FW panel. [ABSTRACT FROM AUTHOR]