Due to the manipulation of radioactive material, nuclear industry has to achieve very strict productivity and purity specifications. Thus, the involved chemical unit operations may involve specific designs. Traditional mixing technics are then adapted to set environmental and process specifications. In the case of actinide precipitation, the operation is conducted in a vortex reactor, which consists in an un-baffled tank reactor stirred by a magnetic rod located at the bottom of the vessel [1]. The reactor is fed by the two reactant solutions and the suspension flows out at the top of the reactor. The resulting internal flow pattern produces a vortex-shaped free surface and two macro mixing zones in the liquid phase: forced and free vortices (see Figure 1). The forced vortex, located in the center around the reactor axis, is characterized by poor axial mixing, while the free vortex zone, corresponding to the annular zone between the forced vortex and the reactor wall, can be described as a well-mixed compartment.