I'm afraid you appear to have misunderstood the whole meaning of...

I'm afraid you appear to have misunderstood the whole meaning of "tails" - you can have "tails" of U₃O₈ as in the South African case or "tails" of UF6 - they are entirely different. The Silex process is only applicable to "tails" of UF₆ NOT U₃O₈ - sorry, You have to understand the nuclear fuel cycle. Firstly you mine uranium ore (usually UO₂ (pitchblende but now called uraninite) but sometimes different ores of uranium (see more HERE). Extraction of the mined ore will never give you 100% recovery - what remains after extraction goes into the tailings dam - some of the older extraction processes (probably those in previously used in South Africa had poor recovery and thus what is now in the "tailing dam" or could not be then economically processed is still thereand using modern uranium processing (e.g Ion Exchange) may now be economic - THAT IS NOT WHAT Silex DOES. All uranium (except for a mine in **on called OKLO which has a very interesting history - it was a natural reactor - see HERE) all have a ²³⁵U assay of .71% (the other 99.29% is ²³⁸U). The ²³⁵U isotope is the ONLY naturally occurring fissionable material but for light water reactors (LWR) which are about 95% of all the world's reactors this percentage needs to be increased to about 4% ²³⁵U - this is called enrichment and is what Silex does (and other older and less efficient technologies (gaseous diffusion & now centrifuge - our competitors). For all these enrichment process to work(including Silex) the U₃O₈ must be turned into a gas (UF6). The "tails we are talking about are from the old (and inefficient) gaseous diffusion plant in Paducah which left a lot of the ²³⁵UF⁶ in those tails - it was similar to just taking the "cream" off the milk but left a lot of the lactose in the "milk") - the Silex process is the only process suitable for removing the "lactose" from the milk - this is because the Silex process becomes more efficient as the ²³⁵U (in the "tails" UF₆) goes down below the "natural" .71% - the Paducah "tails" are the ones we are talking about NOT "mining tails". So unless you are talking about "tails" that came from the South African enrichment (aerodynamic enrichment - which was also inefficient - an improved version of that is what our "aspirant" South African competitor "ASP isotopes" is using) then "mining tails" are unsuitable for Silex - sorry to disappoint.