Chemical and Radiolytical Solvent Degradation in the Purex Process.

The state of the art of chemical and radiolytical solvent degradation is described. For the hydrolysis of tributylphosphate TBP yields HDBP yields H//2MBP yields H//3PO//4 values are given for the individual constants in a temperature range from 23 to 90 degree C. Radiolytic yields were measured for HDBP as 80 mg/Wh, for H//2MBP as 2 mg/Wh, and for H//3PO//4 as 5 mg/Wh. Experimental results on the degradation products of the diluent are summarized and their influence on the process is discussed. Long chain acid phosphates and acid TBP oligomers were identified as responsible for the retention of fission products. Techniques such as polarography, infrared spectrometry and electrolytic conductometry are applied to estimate concentrations of degradation products down to 10** minus **5 mol/l.