Gamma radiolysis of hydrophilic diglycolamide ligands in concentrated aqueous nitrate solution

The radiation chemistry of a series of hydrophilic diglycolamides (DGAs: TEDGA, Me-TEDGA, Me2-TEDGA, and TPDGA) hasbeen investigated under neutral pH, concentrated, aqueous nitrate solution conditions. A combination of steady-stategamma and time-resolved pulsed electron irradiation experiments, supported by advanced analytical techniques and multiscalemodeling calculations, have demonstrated that: (i) the investigated hydrophilic DGAs undergo first-order decay withan average dose constant of (-3.18 ± 0.23) 10–6 Gy–1; (ii) their degradation product × distributions are similar to those underpure water conditions, except for the appearance of NOx adducts; and (iii) radiolysis is driven by hydroxyl and nitrate radicaloxidation chemistry moderated by secondary degradation product scavenging reactions. Overall, the radiolysis ofhydrophilic DGAs in concentrated, aqueous nitrate solutions is significantly slower and less structurally sensitive than underpure water conditions, similar to their lipophilic analogs. Overall, acid hydrolysis, not radiolysis, is expected to limit theiruseful lifetime. These findings are promising for the deployment of hydrophilic DGAs as actinide aqueous phase strippingand hold-back agents, due to the presence of high concetrations of nitrate in envisioned large-scale process conditions