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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

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

Observation of transient ions in radiolysis

Description: Pagodane radical cation and its transformation into pagodiene radical cation was observed by time-resolved FDMR (fluorescence detected magnetic resonance). Other highly unstable radical cations are discussed as well.
Date: March 1, 1996
Creator: Trifunac, A.D. & Werst, D.W.
Partner: UNT Libraries Government Documents Department

Modeling of water radiolysis at spallation neutron sources

Description: In spallation neutron sources neutrons are produced when a beam of high-energy particles (e.g., 1 GeV protons) collides with a (water-cooled) heavy metal target such as tungsten. The resulting spallation reactions produce a complex radiation environment (which differs from typical conditions at fission and fusion reactors) leading to the radiolysis of water molecules. Most water radiolysis products are short-lived but extremely reactive. When formed in the vicinity of the target surface they can react with metal atoms, thereby contributing to target corrosion. The authors describe the results of calculations and experiments performed at los alamos to determine the impact on target corrosion of water radiolysis in the spallation radiation environment. The computational methodology relies on the use of the Los Alamos radiation transport code, LAHET, to determine the radiation environment, and the AEA code, FACSIMILE, to model reaction-diffusion processes.
Date: December 1, 1998
Creator: Daemen, L.L.; Kanner, G.S.; Lillard, R.S.; Butt, D.P.; Brun, T.O. & Sommer, W.F.
Partner: UNT Libraries Government Documents Department

Mechanisms for radiation damadge in DNA

Description: A comprehensive report is provided of the author`s research since 1986 on radiolysis of DNA as well as current state of knowledge in this area. In particular study areas such as the influence of hydration on the absolute yield of primary ionic free radicals in irradiated DNA at 77K, Ab Initio molecular orbital calculations of DNA base pairs and their radical ions, and radiation-induced DNA damage as a function of hydration are discussed.
Date: November 1, 1994
Creator: Sevilla, M.D.
Partner: UNT Libraries Government Documents Department

Interaction of Plutonium with Diverse Materials in Moist Air and Nitrogen-Argon Atmospheres at Room Temperature

Description: Chemical and radiolytic interactions of weapons-grade plutonium with metallic, inorganic, and hydrogenous materials in atmospheres containing moist air-argon mixtures have been characterized at room temperature from pressure-volume-temperature and mass spectrometric measurements of the gas phase. A reaction sequence controlled by kinetics and gas-phase composition is defined by correlating observed and known reaction rates. In all cases, O{sub 2} is eliminated first by the water-catalyzed Pu + O{sub 2} reaction and H{sub 2}O is then consumed by the Pu + H{sub 2}O reaction, producing a gas mixture of N{sub 2}, argon, and H{sub 2}. Hydrogen formed by the reaction of water and concurrent radiolysis of hydrogenous materials either reacts to form PuH{sub 2} or accumulates in the system. Accumulation of H{sub 2} is correlated with the presence of hydrogenous materials in liquid and volatile forms that are readily distributed over the plutonium surface. Areal rates of radiolytic H{sub 2} generation are determined and applied in showing that modest extents of H{sub 2} production are expected for hydrogenous solids if the contact area with plutonium is limited. The unpredictable nature of complex chemical systems is demonstrated by occurrence of the chloride-catalyzed Pu + H{sub 2}O reaction in some tests and hydride-catalyzed nitriding in another.
Date: April 1, 2001
Creator: Haschke, John M.; Martinez, Raymond J.; II, Robert E. Pruner; Martinez, Barbara & Allen, Thomas H.
Partner: UNT Libraries Government Documents Department

Results of Scoping Studies for Determining Radiolytic Hydrogen Production from Moist CST and CST Slurries

Description: In support of the Salt Disposition team, scoping studies have been performed on the radiolysis of moist and aqueous slurries of Crystalline Silicotitanate(CST). If CST is used for removal of Cs-137 from SRS salt solutions, radiolysis of the water by Cs-137 on the CST will produce H2. Also it has been shown that the presence of a solid in the system can enhance the production of H2 by transferring absorbed energy from the solid to the water (1). As indicated in the test plan (2) for this scoping study, it is the intent of this study to determine if CST enhances the radiolytic production of H2 and to estimate the radiolytic hydrogen generation rate from an aqueous CST slurry in a column at the maximum expected Cs-137 loading on the CST.Initially several CST slurry systems were irradiated with Co-60 gamma rays and the radiolytic yield of H2 measured in terms of its G value (molecules of H2 produced per 100 eV of energy absorbed). Based on the results of these tests it was determined that CST did not enhance the radiolytic production of H2 by transferring energy to the water and causing it to decompose.Calculations were then performed to estimate the rate of H2 production from a process column 16ft. long by 5ft. in diameter containing CST that was fully loaded with Cs-137. The maximum rate of H2 production based on the G values measured in this study was one liter per minute at STP (0.04 cfm). This was for a 63 percent water/CST slurry with a G value of 0.2 molecules/100eV for H2 production and a loading of 1 gram of Cs-137 per 100 grams of resin. The present work also indicates that for a column containing salt solution and CST rather than water and CST, the rate would ...
Date: December 11, 1998
Creator: Bibler, N.E.
Partner: UNT Libraries Government Documents Department

EFFECTS OF TRITIUM ON UHMW-PE, PTFE, AND VESPEL POLYIMIDE

Description: Samples of ultrahigh molecular weight polyethylene (UHMW-PE), polytetrafluoroethylene (PTFE), and the polyimide Vespel{reg_sign} were exposed to tritium gas in closed containers initially at 101 kPa (1 atmosphere) pressure and ambient temperature for various times up to 2.3 years. Tritium exposure effects on the samples were characterized by dynamic mechanical analysis (DMA) and radiolysis products were characterized by measuring the total final pressure and composition in the exposure containers at the end of exposure period.
Date: November 1, 2006
Creator: Clark, E & Kirk Shanahan, K
Partner: UNT Libraries Government Documents Department

PULSE RADIOLYSIS IN SUPERCRITICAL RARE GAS FLUIDS

Description: Recently, supercritical fluids have become quite popular in chemical and semiconductor industries for applications in chemical synthesis, extraction, separation processes, and surface cleaning. These applications are based on: the high dissolving power due to density build-up around solute molecules, and the ability to tune the conditions of a supercritical fluid, such as density and temperature, that are most suitable for a particular reaction. The rare gases also possess these properties and have the added advantage of being supercritical at room temperature. Information about the density buildup around both charged and neutral species can be obtained from fundamental studies of volume changes in the reactions of charged species in supercritical fluids. Volume changes are much larger in supercritical fluids than in ordinary solvents because of their higher compressibility. Hopefully basic studies, such as discussed here, of the behavior of charged species in supercritical gases will provide information useful for the utilization of these solvents in industrial applications.
Date: January 1, 2007
Creator: HOLROYD,R.
Partner: UNT Libraries Government Documents Department

Hydrogen Generation by Radiolysis of Tetraphenylborate Solutions and Slurries

Description: This report is a summary of experimental results on radiolytic hydrogen yields from tetraphenylborate (TPB) slurries related to the In-Tank Precipitation (ITP) process. The yields are presented as ''G values'' in units of molecules per 100 eV of absorbed energy. If the radiolytic dose rate is known, the combination of the G value and dose rate gives the rate of hydrogen production. The results of this study are discussed in detail.
Date: May 26, 2004
Creator: CRAWFORD, CHARLESL.
Partner: UNT Libraries Government Documents Department

Interfacial Radiolysis Effects in Tank Waste Speciation

Description: The intent of this program was to establish an understanding of the role of solid-state radiolysis, secondary electron interactions, charge transfer dynamics and the general effect of heterogeneous solids (interfaces and particulate surface chemistry) on tank waste radiation processes. Specifically, there was a need to understand the role of interfaces and solids in the generation of noxious gases and the mechanisms of organic compound degradation.
Date: June 1, 2000
Creator: Orlando, Thomas M.; Meisel, D. & Camaioni, D.M.
Partner: UNT Libraries Government Documents Department