radiation chemical behavior of actinides in extraction systems. III. Pu(IV) Precipitates from gamma -irradiated 30% tbp + n-dodecane

Spectrophotometric, gravimetric, and γ-spectrometric analyses, together with solubility and IR methods, were used to investigate the composition and structure, as well as the conditions and behavior in various polar and low-polarity solvents, of Pu(IV) precipitates formed in the γ-irradiated system 30% TBP + n-dodecane. It was found that the formation of precipitates in solutions containing Pu(IV) in the range 4.10-3 to 2.10-2 M occurs at an absorbed γ-radiation doses Eγ in the range 2.105 to 2.6.106 Gy. At the same time the molar ratio of DBPA (formed by the γ-radiolysis of TBP) to metal lies in the range 3-5. In the given range of values of Eγ effectively all the plutonium passes into the precipitate. The precipitates form a gelatinous mass. 30-50 wt. % of which consists of the mother liquor. The plutonium content amounts to 11-14 wt. %. The molar ratios of DBPA and MBPA to plutonium (nD and nM, respectively) in precipitates formed at values of Eγ in the range 7.0.105 to 2.6.106 Gy are 2.9 +/- 0.5 and 0.5 +/0.1, respectively. Analyses of the IR spectra of washed and unwashed precipitates indicate the presence of hydrogen-bonded DMPA, carbonyl compounds (butyraldehyde or the anhydride), and NO3- ions in precipitates washed with n-dodecane and the absence of these components in precipitates washed with ethanol. On the basis of the experimental data assumptions are made about the composition of the precipitates formed at doses Eγ in the range 2.105 to 2.6.106 Gy