Separation of rare earths and transuranium elements from spent nuclear fuel solution by high performance liquid chromatography

This study concerns the separation of rare earths (RE) uranium, transuranium elements (TUE)from spent nuclear fuel solution by high performance liquid chromatography (HPLC). The correlation between retention behaviour and ionic radii of lanthanides and actinides are also discussed. The aim of this work is to develop a convenient separation procedure for RE, uranium and TUE by studying optimum physico-chemical conditions such as pH of the eluent, temperature and effect of the concentration of the matrix element. The experimental conditions were established by using a mixture of fourteen lanthanides plus yttrium and uranium of known concentration. The behaviour of plutonium was investigated by tracer experiment. Beta-gamma counting, alpha- and gamma-spectroscopy and coulometry were used for detection of the elements. The effect of pH shows that the retention time falls sharply, especially for lighter lanthanides, at lower pH (3.0-3.5) following a gradual decline in the pH range of 4.0-5.0, and then the retention time attains a plateau at high pH of 5.0-6.0. The separation features of RE, uranium and plutonium were satisfactory at 70-90 degree C, and 80 degree C was used as the working temperature. The effect of the concentration of matrix element, uranium, of nuclear fuel on the separation characteristics of RE was studied in the range of 70-700 μg (300-3000 nmol). No appreciable effect was observed up to 220 μg of uranium and above this concentration the elution profile of uranium overlaps with that of heavier lanthanides (up to Er). The elution profiles of spent nuclear fuel solution show that uranium elutes seven minutes earlier than that observed in the simulated experiment. Plutonium elutes at two different retention times (12 and 27 minutes), suggesting the presence of more than one species of plutonium in the spent nuclear fuel solution. Ruthenium elutes at 4 minutes of retention time. The elution profiles of americium and curium overlap, and europium elutes five minutes later than that observed in the simulated experiment. The retention and ionic radii profiles show the consistency for all of the studied lanthanides and actinides except for plutonium