Abstract: The invention is directed to an apparatus for washing a solvent in the recessing of irradiated nuclear fuel. The solvent is washed with an aqueous solution in a mixer-settler having at least one stage which includes a mixing chamber and a settling chamber. The pH is measured by a sensor adjacent stirring means in the mixing chamber and is coupled to a controller controlling metering of the washing solution. The pH of the dispersion in the mixing chamber is measured and an amount of washing solution is added which influences the pH toward the desired operational value. Various recycling means and weir overflow means also influence pH control and the washing operation.

Abstract: The invention is directed to a method of washing a solvent in the reprocessing of irradiated nuclear fuel. The solvent is washed with an aqueous solution in a mixer-settler having at least one stage which includes a mixing chamber and a settling chamber. The pH of the dispersion in the mixing chamber is measured and an amount of washing solution is added which influences the pH toward the desired operational value. An apparatus for carrying out the method is also disclosed.