Radiolytic evaluation of acetohydroxamic acid (AHA) under biphasic (HNO3:n-dodecane and TBP/DEHBA/DEHiBA) used nuclear fuel reprocessing conditions

Radiolytic evaluation of a new technetium redox control reagent for advanced used nuclear fuel separations

“…Within the investigated dose range, DEHiBA was found to degrade linearly with absorbed gamma dose, which is consistent with previous findings for the irradiation of DEHiBA under a variety of solvent system conditions. 56,65 A linear fit to the data shown in Fig. 5 gave a G-value of À0.55 AE 0.02 mmol J À1 for the loss of DEHiBA, in excellent agreement with that reported by Drader et al (À0.53 mmol J À1 ) for the gamma irradiation of 1 M DEHiBA/n-dodecane contacted with an aqueous HNO 3 phase in the absence of DAG.…”

“…These degradation efficiencies are relatively high compared with other molecules considered for this redox-control role, such as AHA ( d ∼ −(5.87 ± 0.61) × 10 −3 kGy −1 ). 56 Further, it is evident from Fig. 3 and the range of d -values in Table 2 that the rate of DAG radiolysis is very dependent upon solution composition, and that it was completely degraded within 100 kGy of absorbed gamma dose in systems containing 2.0 M HNO 3 .…”

“…This was not observed in our previous DEHiBA irradiations in the absence of DAG. 56 The steady-state gamma irradiation of DAG afforded its complete destruction within a few hundred kilogray, with its observed loss in water being much slower than in the investigated 2.0 M HNO 3 systems. This solution formulation dependence is attributed to an important thermal reaction between DAG and the major HNO 3 radiolysis product, HNO 2 , which occurs with a relatively fast rate coefficient of k = 5480 AE 85 M À1 s À1 at 25.0 1C.…”

“…Previous work showed that the additional volume and height afforded by the 10 mL biphasic samples had a negligible effect (<2.5% higher) on the dose rate relative to that experienced by 5 mL samples. 56…”

“…65 Our data clearly show that the presence of DAG and its degradation products have little effect on interfacial radiation chemistry under the investigated conditions, which is consistent with findings for the irradiation of DEHiBA in contact with an AHA containing aqueous HNO 3 phase. 56 That said, the organic phases developed a green hue, the intensity of which increased with absorbed gamma dose. This was not observed in our previous DEHiBA irradiations in the absence of DAG.…”