Rotary vacuum filters are typically used to separate precipitated high value products such as plutonium oxalate from the “mother liquor”. An example design of rotary vacuum filter, used routinely over many years at a number of reprocessing plants, is shown in Fig. 3.5.

In this application, plutonium nitrate solution is fed to the precipitator vessels and oxalic acid used to precipitate plutonium oxalate. The resulting slurry is fed via nozzles onto a filter table which is formed of a stainless steel fine mesh and which is rotated at a few rpm. The underside of this mesh table has a vacuum applied to it which draws the mother liquor away from the precipitated solids. As the table rotates the accumulated solids move under a wash station where they are washed with water, and then under a “scraper” system that removes them from the table and collects them in a screw feeder for transfer to the next process stage. By suitably balancing the slurry feed rate and the rotation speed of the table, continuous operation can be achieved. The unit is small and compact enough to be installed within a glovebox for radioactive contamination containment, but it is not suitable for in-cell use so is not used for materials emitting penetrating radiation.