The accurate modelling of the activation of flowing material in a fusion reactor, such as coolant water or lithium-lead breeder, has important safety and shielding implications. Two codes developed at UKAEA which account for neutron flux variation have been investigated for the potential for incorporating computational fluid dynamics (CFD) and combining the codes’ capabilities. With the recent improvements, including path splitting and recombination, mixing and integration of CFD, benchmarking discrepancies have been clarified and the importance of fluid behaviour in the activation of both lithium-lead and water has been highlighted. This work paves the way for an accurate and benchmarked set of fluid activation codes.