Leaching basket

The eluant is usually 1 M N07 in the form of NH4NO3. The physical method for carrying out the extraction can involve (a) a fixed resin bed, (b) a resin-in-pulp technique where resin in baskets is passed through a stream of pulp or slurry from the leach process, or (c) a moving bed of resin. 

Several types of moving beds have been adopted for leaching. The Boilman extractor involves a chain of perforated baskets that moves downward at one side of the bucket... 

Sheared fuel is fed to a receiving basket held in one compartment of a three-compartment semicontinuous dissolver. Nitric acid is fed continuously to the compartment and leach liquor is discharged continuously from it to the feed adjustment tank. When the basket is filled with fuel, the compartment holding it is rotated to a second position in which dissolution of the remaining oxide fuel in additional acid is completed. The basket and fuel hulls are finally rotated to a third position where water washes the residual leach liquor into the feed adjustment tank. The nitric acid contains 5.6 g of gadolinium as nitrate, to prevent criticality. 

In Fig. 12.8-2a an enclosed moving-bed bucket elevator device is shown. This is called the Bollman extractor. Dry flakes or solids are added at the upper right side to a perforated basket or bucket. As the buckets on the right side descend, they are leached by a dilute solution of oil in solvent called half miscella. This liquid percolates downward through the moving buckets and is collected at the bottom as the strong solution or full miscella. The buckets moving upward on the left are leached countercurrently by fresh solvent sprayed on the top bucket. The wet flakes are dumped as shown and removed continuously. 

The French stationary-basket extractor is a variant of this. The flakes are contained in stationary, compartmented beds filled by a rotating spout to feed the solids and are leached with solvent and miscella countercurrently [15, 33]. 

The BoHman extractor [38] (Fig. 13.20) is one of several basket-type machines. Solids are conveyed in perforated baskets attached to a chain conveyor, down on the right and up on the left in the figure. As they descend, they are leached in parallel flow by a dilute solvent-oil solution ha f miscelld) pumped from the bottom of the vessel and sprayed over the baskets at the top. The liquid percolates through the solids from basket to basket, collects at the bottom as the final strong solution of the oil (/ // miscella)y and is removed. On the ascent, the solids are leached countercurrently by a spray of fresh solvent to provide the half miscella. A short drainage time is provided before the baskets are dumped at the top. There are many variants of this device, e.g., the horizontal arrangement of Fig. 13.21. 

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