FORMATION OF RADIOLYSIS PRODUCTS OF THE EXTRACTION REAGENT

The radiolysis of individual TBP and its solutions in hydrocarbons of various compositions has been investigated in a number of studies [4-11]. It is known that an increase in the concentration of dibutyl phosphate (DBP) in the organic solution leads to a sharp increase in the distribution coefficient (Kd) of zirconium [12], when the latter is present in trace amounts. Analogous results were obtained in [10, 11] in an investigation of the radiolysis of solutions of TBP, where it was shown that the changes in K d of zirconium depend on the nature of the diluent and are rather well correlated with the concentration of the DBP formed. Data on the radiolysis of TBP in contact with a solution of nitric acid containing zirconium and uranium nitrates were cited in [13]. Both in our studies and in other published studies, until recently the deterioration of the extraction characteristics was explained by the appearance of DBP. And yet it is clear that at sufficiently large doses of radiation, monobutyl phosphate (MBP) and phosphoric acid should also be accumulated in the system. As was shown in [4, 8], in the radiolysis of individual TBF in the absence of an aqueous phase, the concentration of MBP is only 5-10% of the concentration of DBP. In the presence of an aqueous phase, in accord with the distribution coefficient [!4], MBP should be accumulated primarily in it, and if we take into consideration the low radiation yield of MBP as well, it might seem that its influence on the extraction of zirconium should be minor. Nonetheless, there were indications of the participation of this compound in the process of extraction at relatively high concentrations of zirconium in solution [3]. In this work we discussed the formation of the basic radiolysis products of the extraction reagent - DBP, MBP, and H3PO4, "polymer" - and their influence on the extraction of zirconium when its concentration in solution is high. The radiation source was ~~ with an activity of the preparation equal to 200,000 gram radium equivalents. The dose was 20 W/liter, interval up to 0-100 W �9 h/liter. The doses were calculated according to the energy absorbed by the entire system. Irradiation was conducted in glass ampoules equipped with a mixer, supply lines for the passage of gas and collection of samples. The ratio of the volumes of the organic and aqueous phases in the irradiated system was equal to 1 : 1. Composition of the phases: organic- 25% TBP + synthine; aqueous- 3 M HNO3, 3 M HNO 3 + 2 -10 -2 ZrO 2 �9 (NO3)2. The experiments were conducted while bubbling oxygen through the solution under conditions of its equilibrium with air and a temperature of 18-20~ and in the presence of a 'Ideficiency" of it, when oxygen was not bubbled through, but there was an atmosphere of air above the solution. It was shown that in this case, in the geometry of our experiments at doses >5 W .h/liter, the system was identical with deaerated systems with respect to the yield of the radiolysis products of TBP.