The Radiation Chemistry of CMPO: Part 2. Alpha Radiolysis

• Published in: Solvent extraction and ion exchange Vol. 32; no. 2; pp. 167 - 178
• Main Authors: Mincher, Bruce J., Mezyk, Stephen P., Elias, Gracy, Groenewold, Gary S., LaVerne, Jay A., Nilsson, Mikael, Pearson, Jeremy, Schmitt, Nicholas C., Tillotson, Richard D., Olson, Lonnie G.
• Format: Journal Article
• Language: English
• Published: United States Taylor & Francis 23.02.2014; Taylor and Francis
• Subjects: alpha irradiation; alpha radiation; CMPO; free radicals; high LET; NUCLEAR FUEL CYCLE AND FUEL MATERIALS; radiation chemistry; solvent etxraction; solvent extraction
• ISSN: 0736-6299; 1532-2262
• DOI: 10.1080/07366299.2013.850300

Octylphenyl-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) dissolved in dodecane was subjected to α -irradiation using a He-ion beam, 244 Cm isotopic α -rays, and He and Li ions created by the n, α reaction of 10 B in a nuclear reactor. Post-irradiation samples were analyzed for the radiolytically-induced decrease in CMPO concentration, the appearance of degradation products, and their Am solvent extraction distribution ratios. The -G CMPO -value for the radiolytic degradation of CMPO was found to be very low compared to values previously reported for γ -irradiation. Additionally, isotopic irradiation to absorbed α -doses as high as 600 kGy in aerated solution had no effect on Am solvent extraction or stripping. The main CMPO radiolysis products identified in He-ion beam irradiated samples by ESI-MS include amides, an acidic amide, and amines produced by bond rupture on either side of the CMPO carbonyl group. Deaerated samples irradiated using the reactor in the absence of an aqueous phase, or with a dilute nitric acid aqueous phase showed small but measurable decreases in CMPO concentration with increasing absorbed doses. Higher concentrations of nitric acid resulted in lower decomposition rates for the CMPO. The radio-protection by dissolved oxygen and nitric acid previously found for γ -irradiated CMPO also occurs for α -irradiation. This suggests that similar free-radical mechanisms operate in the high-LET system, but with lower degradation yields due to the lower overall radical concentrations produced.