ABSTRACT
Radiolysis of diisodecyl phosphoric acid (DIDPA) in n-dodecane containing tributyl phosphate (TBP) was examined by analyzing concentrations of acidic extractants and H3PO4, and its effect on the extraction of neptunium was studied from the aspect of the extraction rate. For the solvent containing 0.5 M DIDPA and 0.1 M TBP irradiated in the absence of HNO3, G-values for degradation of DIDPA and for production of dibutyl phosphoric acid (DBP) were found to be 0.47 and 0.14, respectively. For the solvent irradiated in stationary contact with 0.5 M HNO3, G-value for DIDPA degradation was found to be 0.73, which was 1.7 times larger than the value for the solvent irradiated in the absence of HNO3.
In the experiment on the extraction of neptunium initially in the pentavalent state from the solution containing 0.5 M HNO3 and 0.5 M H2O2, it was found that the extraction rete tas determined by the concentration of MIDPA forted by radiolysis when the solvent was irradiated with lower dose than 1 MGy in the absence of HNO3. When the solvent absorbed higher dose or was irradiated in the presence of HNO3, the extraction rate was influenced by the other radiolysis products. Even in this case, when the solvent contained TBP, the rate varied little until absorbed dose increased over 0.5 MGy.