The Investigation of an Alternative Tailings Deposition System for Uranium Tailings

ORANO undertook a tailings deposition review for the JEB Pit Tailings Management Facility (TMF) at the McClean Lake uranium mill in northern Saskatchewan.  After initial screening, two tailings deposition alternatives were advanced to the detailed review stage.  The first option included continuation of deposition using tremie methodology but with the implementation of satellite deposition barges placed radially from the existing barge.  The second option utilized sub-aqueous rather than tremie deposition. Subaqueous deposition offers several advantages but is a fundamental shift in the tailings deposition methodology and had to be investigated and proven suitable.

Extensive test design work was conducted to demonstrate the effectiveness of the test to both internal and external stakeholders.  This work included conducting rheology and geotechnical testing campaigns, computational Fluid Dynamic (CFD) simulation to design the sub-aqueous diffuser, and deposition simulations to assess the accumulation of tailings during this short-term test.  This paper focuses on the CFD and deposition modelling results and how they compared to the actual short-term test results. 

The CFD simulations investigated the type of diffuser to use, and the effect the tailings density and depth of the discharge had on the tailings stream behaviour.  A horizontal trumpet type diffuser produced the least suspended solids and highest placed initial density. Deposition modelling estimated the degree of tailings mounding and lateral spread near the deposition point during the test.  In the fall of 2017, the test was conducted for 25 days. The results from this test were very consistent with the predicted behaviour in both the CFD and deposition modelling and the trial was considered a success.