A routine analytical determination of di- and tributylphosphate in PUREX-process solutions

Determination of the extractant tributylphosphate and its main degradation product dibutylphosphate is necessary for a control of solvent- and raffinatestreams. These analyses must be carried out with samples, which contain - depending on their origin - various amounts of uranium, plutonium, fission products and nitric acid. For dibutylphosphate the concentration range is between 5 and 500 mg/l. The analysis of TBP must cover a very wide range: depending on the efficiency of the raffinate wash, aqueous systems may contain 5 to 300 mg TBP/l; in a mixture with n-alkanes concentrations of 200 - 300 g TBP/l must be analyzed. A procedure is described, which can be easily adapted to the respective problem: Dibutylphosphate is separated from the interfering matrix by a simple extraction process and, after methylation, is measured by a standardised, automated gaschromatography. Depending on the concentration, TBP is measured by gaschromatography either directly or after an enrichment by extraction. For the range from 5 to 500 mg/l both organophosphates are analyzed with recovery rates of 93 - 100% and variation coefficients from +- 1% to +- 5%. (orig.)