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The Radiation Chemistry of CMPO: Part 2. Alpha Radiolysis

2014; Taylor & Francis; Volume: 32; Issue: 2 Linguagem: Inglês

10.1080/07366299.2013.850300

1532-2262

Bruce J. Mincher, Stephen P. Mezyk, Gracy Elias, Gary S. Groenewold, Jay A. LaVerne, Mikael Nilsson, Jeremy D. Pearson, Nicholas C. Schmitt, Richard D. Tillotson, Lonnie G. Olson,

Analytical chemistry methods development

Abstract 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 10B 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. Keywords: CMPOfree radicalsalpha irradiationsolvent extraction ACKNOWLEDGMENTS The authors thank Prof. Michael Wiescher for making the facilities of the Notre Dame Nuclear Structure Laboratory available; the latter is supported by the U.S. National Science Foundation. This work was supported under a DOE-NEUP grant and Fuel Cycle R&D programmatic funding, both under Idaho Operations Contract DE-AC07-05ID14517. The research of JAL as described herein was supported through the Division of Chemical Sciences, Geosciences and Biosciences, Basic Energy Sciences, Office of Science, United States Department of Energy through grant number DE-FC02-04ER15533. This is contribution number NDRL 4976 from the Notre Dame Radiation Laboratory.