Metal retention behaviour of diluent degradation products

The PUREX solvent, tri-butyl phosphate (TBP) in n-dodecane (n-DD), during the reprocessing of spent fuel, undergoes hydrolysis and radiolysis due to the intense ionizing radiation environment and decay heat from the short-lived radio isotopes in addition to the chemical environment due to presence of nitric acid. The primary degradation products resulted during solvent degradation are aqueous washable unlike the secondary degradation products like high molecular weight phosphates and the diluent degradation products which are responsible for the retention of metal ions. There is a scarcity of information on the metal retention behavior of the diluent degradation products. In this context, investigations were carried out on the gamma radiolysis of n-DD in monophasic as well as biphasic system in presence of 4M HNO₃. Gamma radiolysis was carried out up to 500 kGy. The zirconium metal retention behavior of the irradiated diluent was determined before and after alkali wash upon diluting the degraded n-DD up to 1.1 M using fresh TBP and was compared with un-irradiated solvent ions. There is a scarcity of information on the metal retention behavior of the diluent degradation products. In this context, investigations were carried out on the gamma radiolysis of n-DD in monophasic as well as biphasic system in presence of 4M HNO₃. Gamma radiolysis was carried out up to 500 kGy. The zirconium metal retention behavior of the irradiated diluent was determined before and after alkali wash upon diluting the degraded n-DD up to 1.1 M using fresh TBP and was compared with un-irradiated solvent. The D value obtained for the un-irradiated 1.1 M TBP/n-DD was about 0.31 which gradually increased up to 0.45 as the absorbed gamma dose by the diluent increased