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Anion solvation in alcohols

Description: Anion solvation is measured in alcohols using pump-probe pulse radiolysis and the activation energy of solvation is determined. Solvation of an anion appears to be different than excited state solvation. The continuum dielectric model does not appear to explain the results.
Date: March 1996
Creator: Jonah, C. D.; Xujia, Zhang & Lin, Yi
Partner: UNT Libraries Government Documents Department

Radiolysis Model Sensitivity Analysis for a Used Fuel Storage Canister

Description: This report fulfills the M3 milestone (M3FT-13PN0810027) to report on a radiolysis computer model analysis that estimates the generation of radiolytic products for a storage canister. The analysis considers radiolysis outside storage canister walls and within the canister fill gas over a possible 300-year lifetime. Previous work relied on estimates based directly on a water radiolysis G-value. This work also includes that effect with the addition of coupled kinetics for 111 reactions for 40 gas species to account for radiolytic-induced chemistry, which includes water recombination and reactions with air.
Date: September 20, 2013
Creator: Wittman, Richard S.
Partner: UNT Libraries Government Documents Department

Coupling the Mixed Potential and Radiolysis Models for Used Fuel Degradation

Description: The primary purpose of this report is to describe the strategy for coupling three process level models to produce an integrated Used Fuel Degradation Model (FDM). The FDM, which is based on fundamental chemical and physical principals, provides direct calculation of radionuclide source terms for use in repository performance assessments. The G-value for H2O2 production (Gcond) to be used in the Mixed Potential Model (MPM) (H2O2 is the only radiolytic product presently included but others will be added as appropriate) needs to account for intermediate spur reactions. The effects of these intermediate reactions on [H2O2] are accounted for in the Radiolysis Model (RM). This report details methods for applying RM calculations that encompass the effects of these fast interactions on [H2O2] as the solution composition evolves during successive MPM iterations and then represent the steady-state [H2O2] in terms of an “effective instantaneous or conditional” generation value (Gcond). It is anticipated that the value of Gcond will change slowly as the reaction progresses through several iterations of the MPM as changes in the nature of fuel surface occur. The Gcond values will be calculated with the RM either after several iterations or when concentrations of key reactants reach threshold values determined from previous sensitivity runs. Sensitivity runs with RM indicate significant changes in G-value can occur over narrow composition ranges. The objective of the mixed potential model (MPM) is to calculate the used fuel degradation rates for a wide range of disposal environments to provide the source term radionuclide release rates for generic repository concepts. The fuel degradation rate is calculated for chemical and oxidative dissolution mechanisms using mixed potential theory to account for all relevant redox reactions at the fuel surface, including those involving oxidants produced by solution radiolysis and provided by the radiolysis model (RM). The RM calculates the ...
Date: August 30, 2013
Creator: Buck, Edgar C.; Jerden, James L.; Ebert, William L. & Wittman, Richard S.
Partner: UNT Libraries Government Documents Department

Radiolysis of actinides and technetium in alkaline media

Description: The {gamma}-radiolysis of aerated alkaline aqueous solutions of Np(V), Np(VI), Pu(VI), Tc(IV), Tc(V), and TC(VII) was studied in the absence of additives and in the presence of CO{sub 3}{sup 2-}, NO{sub 3}{sup -}, NO{sub 2}{sup -}, EDTA, formate, and other organic compounds. The radiolytic reduction of Np(V), Np(VI), Pu(VI), and TC(VII) under different experimental conditions was examined in detail. The addition of EDTA, formate, and alcohols was found to considerably increase the radiation-chemical reduction yields. The formation of the Np(V) peroxo complex was observed in the {gamma}-radiolysis of alkaline aqueous solutions of Np (VI) in the presence of nitrate.
Date: July 10, 1996
Creator: Delegard, C. H.
Partner: UNT Libraries Government Documents Department


Description: A small, laboratory-sized loop was designed for steady-state radiolytic gas recombination studies. It consists of an electrolysis cell, which simulates the radiolytic gas formed in a reactor, and a bomb for containing slurry under test. The electrolysis capacity of the system is adequate for the study of slurries having recombination rates as high as 10 moles/hr/liter of slurry at the proposed slurry reactor operating conditions. (auth)
Date: September 18, 1958
Creator: Culver, R.S.
Partner: UNT Libraries Government Documents Department

Radiation Chemistry of Advanced TALSPEAK Flowsheet

Description: This report summarizes the results of initial experiments designed to understand the radiation chemistry of an Advanced TALSPEAK process for separating trivalent lanthanides form the actinides. Biphasic aerated samples were irradiated and then analyzed for post-irradiation constituent concentrations and solvent extraction distribution ratios. The effects of irradiation on the TALSPEAK and Advanced TALSPEAK solvents were similar, with very little degradation of the organic phase extractant. Decomposition products were detected, with a major product in common for both solvents. This product may be responsible for the slight increase in distribution ratios for Eu and Am with absorbed dose, however; separation factors were not greatly affected.
Date: August 28, 2013
Creator: Mincher, Bruce; Peterman, Dean; Mcdowell, Rocklan; Olson, Lonnie & Lumetta, Gregg J.
Partner: UNT Libraries Government Documents Department

Radiolysis Process Model

Description: Assessing the performance of spent (used) nuclear fuel in geological repository requires quantification of time-dependent phenomena that may influence its behavior on a time-scale up to millions of years. A high-level waste repository environment will be a dynamic redox system because of the time-dependent generation of radiolytic oxidants and reductants and the corrosion of Fe-bearing canister materials. One major difference between used fuel and natural analogues, including unirradiated UO2, is the intense radiolytic field. The radiation emitted by used fuel can produce radiolysis products in the presence of water vapor or a thin-film of water (including OH• and H• radicals, O2-, eaq, H2O2, H2, and O2) that may increase the waste form degradation rate and change radionuclide behavior. H2O2 is the dominant oxidant for spent nuclear fuel in an O2 depleted water environment, the most sensitive parameters have been identified with respect to predictions of a radiolysis model under typical conditions. As compared with the full model with about 100 reactions it was found that only 30-40 of the reactions are required to determine [H2O2] to one part in 10–5 and to preserve most of the predictions for major species. This allows a systematic approach for model simplification and offers guidance in designing experiments for validation.
Date: July 17, 2012
Creator: Buck, Edgar C.; Wittman, Richard S.; Skomurski, Frances N.; Cantrell, Kirk J.; McNamara, Bruce K. & Soderquist, Chuck Z.
Partner: UNT Libraries Government Documents Department

Characterization of radiolytically generated degradation products in the strip section of a TRUEX flowsheet

Description: This report presents a summary of the work performed to meet the FCRD level 2 milestone M3FT-13IN0302053, “Identification of TRUEX Strip Degradation.” The INL radiolysis test loop has been used to identify radiolytically generated degradation products in the strip section of the TRUEX flowsheet. These data were used to evaluate impact of the formation of radiolytic degradation products in the strip section upon the efficacy of the TRUEX flowsheet for the recovery of trivalent actinides and lanthanides from acidic solution. The nominal composition of the TRUEX solvent used in this study is 0.2 M CMPO and 1.4 M TBP dissolved in n-dodecane and the nominal composition of the TRUEX strip solution is 1.5 M lactic acid and 0.050 M diethylenetriaminepentaacetic acid. Gamma irradiation of a mixture of TRUEX process solvent and stripping solution in the test loop does not adversely impact flowsheet performance as measured by stripping americium ratios. The observed increase in americium stripping distribution ratios with increasing absorbed dose indicates the radiolytic production of organic soluble degradation compounds.
Date: August 1, 2013
Creator: Peterman, Dean R.; Olson, Lonnie G.; Groenewold, Gary S.; McDowell, Rocklan G.; Tillotson, Richard D. & Law, Jack D.
Partner: UNT Libraries Government Documents Department

Nanosecond Mid-Infrared Detection for Pulse Radiolysis

Description: Pulse radiolysis, utilizing electron pulses from accelerators, is the definitive method for adding single positive or negative charges to molecules. It is also among the most effective means for creating free radicals. Such species are particularly important in applications such as redox catalysis relevant to solar energy conversion and advanced nuclear energy systems. Coupled with fast UV-visible detection, pulse radiolysis has become an extremely powerful method for monitoring the kinetics of the subsequent reactions of these species on timescales ranging from picoseconds to seconds. However, in many important contexts the radicals formed are difficult to identify due to their broad and featureless UV-visible absorption spectra. Time-resolved infrared (TRIR) absorption spectroscopy is a powerful structural probe of short-lived intermediates, which allows multiple transient species to be clearly identified and simultaneously monitored in a single process. Unfortunately, due to technical challenges the coupling of fast (sub-millisecond) TRIR with pulse radiolysis has received little attention, being confined to gas-phase studies. Taking advantage of recent developments in mid-IR laser technology, we have recently begun developing nanosecond TRIR detection methodologies for condensed-phase samples at our Laser Electron Accelerator Facility (LEAF). The results of preliminary pulse radiolysis-TRIR investigations on the formation of the one-electron reduced forms of CO{sub 2} reduction catalysts (e.g. see above) and their interactions with CO{sub 2} will be presented.
Date: July 12, 2009
Creator: Grills,D.C.; Preses, J.M.; Wishart, J.F. & Cook, A.R.
Partner: UNT Libraries Government Documents Department