Radiation chemistry of the branched-chain monoamide di-ethylhexyl-isobutyramide
The radiolytic degradation rate of DEHiBA is similar to that of TBP and malonamides, and slow compared to the DGAs, and is unaffected by contact with an aqueous phase or aeration. However, product distributions vary with irradiation conditions. Based on these results, DEHiBA apparently undergoes degradation via two pathways: an acid promoted pathway, Scheme 1, and an acid independent pathway, Scheme 2. It is clear that the monoamide degrades when irradiated in the presence of an aqueous phase to form a series of lower molecular weight species generated from the cleavage of the C-N amide bond or C-N amine bond. As this is the active site during synthesis, it is not surprising that this is the weak point in the ligand structure. The main degradation products appear to be DEHA and EHiBA. These species, and the smaller fragments produced by their radioysis have increased solubility in the aqueous phase. Another product common to all irradiation conditions was the species at m/z 310.2, which is identified as an unsaturated derivative of DEHiBA, resulting from the loss of two H-atoms. In contrast, when an aqueous phase is not present, higher molecular weight products are generated via carbon radical addition reactions under the more reducing conditions. These products have maximum abundance at 750 kGy, and then decrease with increasing absorbed dose. Their significance to a biphasic solvent extraction process is probably inconsequential. Solvent extraction results show that DEHiBA radiolytic degradation had little effect on uranium distribution ratios even at absorbed doses as high as 1 MGy. The build-up of degradation products in the aqueous phase apparently decreased stripping distribution ratios, which is not adverse to a process application. Thus, these findings for DEHiBA are in agreement with previous work that claimed good radiation stability and generation of inoffensive radiolysis products for the monoamides. This, in addition to their CHON nature suggests that they will be good candidates for the development of advanced fuel cycles. Interesting future work would include a comparison study on the n-alkane monoamide DEHBA.
- Research Organization:
- Idaho National Laboratory (INL), Idaho Falls, ID (United States)
- Sponsoring Organization:
- USDOE Office of Nuclear Energy (NE)
- DOE Contract Number:
- AC07-05ID14517
- OSTI ID:
- 1406976
- Report Number(s):
- INL/EXT-16-39882-Rev000; TRN: US1800528
- Country of Publication:
- United States
- Language:
- English
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