PURPOSE: To make an on-line analysis by admitting a solvent of nitric acid and an organic solvent into a settler from a pulse column used for nuclear fuel reprocessing, and providing piping for sampling from the settler to analyzing devices for respective liquids.

CONSTITUTION: The solution of nitric acid and organic solvent are sucked from inlets 19 and 19 above and below the perforated disc 4 in the cylindrical casing 3 of the pulse column and admitted into the settler 22. The solution of nitric acid gathers in a layer A in the settler 22 and the organic solvent gathers in a layer B. Their boundary surface is adjusted through interface meters 32 and 33. Then, the piping for sampling is provided to sent the solution of nitric acid from the layer A in the settler 22 to an analyzing device 24 and the organic solvent from the layer B to an analyzing device 25. Both liquids are flowed to discharge outlets 20 and 20 after analyses and admitted into the pulse column 3. Thus, the solution of nitric acid and organic solvent are sent to the analyzing devices through the piping for sampling, so uranium and plutonium in the liquids are analyzed speedily and easily on on-line basis.