Effect of Co Irradiation on Boehmite Dissolution in Caustic Solutions.

Here, we examine how radiation impacts the dissolution behavior of boehmite by subjecting dry nanoparticles of different sizes to Co γ radiation and subsequently analyzing their dissolution behavior in caustic solutions as a function of temperature. The measured kinetics show that irradiation with an amount 228.24 Mrad significantly slows the dissolution rate, particularly for smaller sizes at lower temperatures.

In Situ Uranium Extraction through the Synthesis of the Uranyl Peroxide Studtite Using a Nonthermal Plasma.

Extraction of uranium from water is an essential step in leach (ISL) mining and environmental decontamination. This is often done by precipitating uranium in solution as the uranyl peroxide studtite, [(UO)(O)(HO)](HO), by adding hydrogen peroxide, which is energy-intensive to produce and hazardous to transport. Here, we present a method for synthesizing studtite, by generating reactive oxygen species in solution using a nonthermal plasma.

Activation of uranyl peroxides by ionizing radiation prior to uranyl carbonate formation.

The solid form of the uranyl peroxide cage (UPC) cluster LiU (Li[(UO)(O)]) was irradiated by 5 MeV He ions to achieve doses up to 42 MGy. An intermediate compound formed that reacts with atmospheric CO to form uranyl carbonates. The role of water in the UPC to uranyl carbonate transformation was studied by flowing either dry or hydrated Ar over samples during He irradiation, and by storing samples in dry and humid environments before and after irradiation.

Radiation-Induced Defects in Uranyl Trinitrate Solids.

Actinides are inherently radioactive; thus, ionizing radiation is emitted by these elements can have profound effects on its surrounding chemical environment through the formation of free radical species. While previous work has noted that the presence of free radicals in the system impacts the redox state of the actinides, there is little atomistic understanding of how these metal cations interact with free radicals. Herein, we explore the effects of radiation (UV and γ) on three U(VI) trinitrate complexes, M[UO(NO)] (where M=K, Rb, Cs), and their respective nitrate salts in the solid state via electron paramagnetic resonance (EPR) and Raman spectroscopy paired with Density Functional Theory (DFT) methods.

Effect of impurities on radical formation in gibbsite radiolysis.

The generation and stabilization of gamma radiation-induced hydrogen atoms in gibbsite (Al(OH)) nanoplates is directly related to the nature of residual ions from synthetic precursors used, whether nitrates or chlorides. The concentration of hydrogen atoms trapped in the interstitial layers of gibbsite is lower and decays faster in comparison to boehmite (AlOOH), which could affect the management of these materials in radioactive waste.

Solid-State Transformation of Uranyl Peroxide Materials through High-Level Irradiation.

The solid-state transformation of sodium uranyl triperoxide (Na(UO)(O)·9HO, NaUT) to sodium uranyl tricarbonate (Na(UO)(CO)) by radiolysis was observed for the first time. The exposure of NaUT to 3 MGy gamma irradiation resulted in partial breakdown of the peroxides forming a mixed peroxide and carbonate species. The effects of He-ion irradiation on NaUT were also investigated up to 225 MGy using both hydrated argon and dry argon.

Atomistic-Level Effects of Noncovalent Interactions and Crystalline Packing for Organic Material Structural Integrity upon Exposure to Gamma Radiation.

Developing an atomistic understanding of ionizing radiation induced changes to organic materials is necessary for intentional design of greener and more sustainable materials for radiation shielding and detection. Cocrystals are promising for these purposes, but a detailed understanding of how the specific intermolecular interactions within the lattice upon exposure to radiation affect the structural stability of the organic crystalline material is unknown. This study evaluates atomistic-level effects of γ radiation on both single- and multicomponent organic crystalline materials and how specific noncovalent interactions and packing within the crystalline lattice enhance structural stability.

Investigation of Radiation Effects in the Uranyl Mineral Metaschoepite.

The effects of water vapor and He ion irradiation on the alteration of particles of the uranyl hydroxide phase metaschoepite, [(UO)O(OH)](HO), are determined. Raman spectra collected immediately postirradiation revealed the presence of a uranyl oxide phase structurally similar to γ-UO or UO. Short-term storage postirradiation at elevated relative humidity accelerated formation of the uranyl peroxide phase studtite, [(UO)(O)(HO)](HO).

Cations impact radical reaction dynamics in concentrated multicomponent aqueous solutions.

Ultraviolet (UV) photolysis of nitrite ions (NO2-) in aqueous solutions produces a suite of radicals, viz., NO·, O-, ·OH, and ·NO2. The O- and NO· radicals are initially formed from the dissociation of photoexcited NO2-.

An integrated Monte Carlo track-structure simulation framework for modeling inter and intra-track effects on homogenous chemistry.

. The TOPAS-nBio Monte Carlo track structure simulation code, a wrapper of Geant4-DNA, was extended for its use in pulsed and longtime homogeneous chemistry simulations using the Gillespie algorithm..

Ozone-Facilitated Formation of Uranyl Peroxide in Humid Conditions.

Metaschoepite, [(UO)O(OH)](HO), maintained in a high relative humidity (RH) environment with air initially transformed into an intermediate phase that subsequently was replaced by the peroxide phase studtite, [(UO)(O)(HO)](HO), over the course of 42 days, as observed using Raman and infrared spectroscopy and powder X-ray diffraction. Addition of atmospheric ozone vastly increased the rate and extent of the transformation to studtite but only in a high-RH atmosphere. Owing to its strong affinity for peroxide, uranyl reacted with hydrogen peroxide as it formed and precipitated stable studtite.

TOPAS-nBio simulation of temperature-dependent indirect DNA strand break yields.

Current Monte Carlo simulations of DNA damage have been reported only at ambient temperature. The aim of this work is to use TOPAS-nBio to simulate the yields of DNA single-strand breaks (SSBs) and double-strand breaks (DSBs) produced in plasmids under low-LET irradiation incorporating the effect of the temperature changes in the environment. A new feature was implemented in TOPAS-nBio to incorporate reaction rates used in the simulation of the chemical stage of water radiolysis as a function of temperature.

Radiation-Induced Solid-State Transformations of Uranyl Peroxides.

Single-crystal X-ray diffraction studies of pristine and γ-irradiated Ca[UO(O)]·9HO reveal site-specific atomic-scale changes during the solid-state progression from a crystalline to X-ray amorphous state with increasing dose. Following γ-irradiation to 1, 1.5, and 2 MGy, the peroxide group not bonded to Ca is progressively replaced by two hydroxyl groups separated by 2.

Unusual Metal-Organic Framework Topology and Radiation Resistance through Neptunyl Coordination Chemistry.

A Np(V) neptunyl metal-organic framework (MOF) with rod-shaped secondary building units was synthesized, characterized, and irradiated with γ rays. Single-crystal X-ray diffraction data revealed an anionic framework containing infinite helical chains of actinyl-actinyl interaction (AAI)-connected neptunyl ions linked together through tetratopic tetrahedral organic ligands (). exhibits an unprecedented net, demonstrating that AAIs may be exploited to give new MOFs and new topologies.

Crystallization and Phase Transformations of Aluminum (Oxy)hydroxide Polymorphs in Caustic Aqueous Solution.

Gibbsite, bayerite, and boehmite are important aluminum (oxy)hydroxide minerals in nature and have been widely deployed in various industrial applications. They are also major components in caustic nuclear wastes stored at various U.S.

Gamma radiation-induced defects in KCl, MgCl, and ZnCl salts at room temperature.

Room temperature post-irradiation measurements of diffuse reflectance and electron paramagnetic resonance spectroscopies were made to characterize the long-lived radiation-induced species formed from the gamma irradiation of solid KCl, MgCl2, and ZnCl2 salts up to 100 kGy. The method used showed results consistent with those reported for electron and gamma irradiation of KCl in single crystals. Thermal bleaching of irradiated KCl demonstrated accelerated disaggregation of defect clusters above 400 K, due to decomposition of Cl3-.

Design and performance of high-temperature furnace and cell holder for in situ spectroscopic, electrochemical, and radiolytic investigations of molten salts.

To facilitate the development of molten salt reactor technologies, a fundamental understanding of the physical and chemical properties of molten salts under the combined conditions of high temperature and intense radiation fields is necessary. Optical spectroscopic (UV-Vis-near IR) and electrochemical techniques are powerful analytical tools to probe molecular structure, speciation, thermodynamics, and kinetics of solution dynamics. Here, we report the design and fabrication of three custom-made apparatus: (i) a multi-port spectroelectrochemical furnace equipped with optical spectroscopic and electrochemical instrumentation, (ii) a high-temperature cell holder for time-resolved optical detection of radiolytic transients in molten salts, and (iii) a miniaturized spectroscopy furnace for the investigation of steady-state electron beam effects on molten salt speciation and composition by optical spectroscopy.

Unprecedented Radiation Resistant Thorium-Binaphthol Metal-Organic Framework.

A thorium-organic framework () containing hexameric secondary building units connected by functionalized binaphthol linkers was synthesized, characterized, and irradiated to probe its radiation resistance. Radiation stability was examined using γ-rays and 5 MeV He ions to simulate α particles. γ-irradiation of to an unprecedented 4 MGy dose resulted in no apparent bulk structural damage visible by X-ray diffraction.

Stability of Solid Uranyl Peroxides under Irradiation.

The effects of radiation on a variety of uranyl peroxide compounds were examined using γ-rays and 5 MeV He ions, the latter to simulate α-particles. The studied materials were studtite, [(UO)(O)(HO)](HO), the salt of the U uranyl peroxide cage cluster, LiK[(UO)(O)(OH)]·255HO, the salt of UOx uranyl peroxide oxalate cage cluster, LiK[{(UO)(O)}(CO)]·HO, and the salt of the UPp (Pp = pyrophosphate) uranyl peroxide pyrophosphate cage cluster, LiNa[(UO)(O)(PO)]·120HO. Irradiated powders were characterized using powder X-ray diffraction, Raman spectroscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, and UV-vis spectroscopy.

Ionizing radiation processing and its potential in advancing biorefining and nanocellulose composite materials manufacturing.

Nanocellulose is a high value material that has gained increasing attention because of its high strength, stiffness, unique photonic and piezoelectric properties, high stability and uniform structure. Through utilization of a biorefinery concept, nanocellulose can be produced in large volumes from wood at relatively low cost via ionizing radiation processing. Ionizing radiation causes significant break down of the polysaccharide and leads to the production of potentially useful gaseous products such as H and CO.

Relativistic electron acceleration by mJ-class kHz lasers normally incident on liquid targets.

We report observation of kHz-pulsed-laser-accelerated electron energies up to 3 MeV in the -klaser (backward) direction from a 3 mJ laser interacting at normal incidence with a solid density, flowing-liquid target. The electrons/MeV/s.r.

Inhibition of Radiolytic Molecular Hydrogen Formation by Quenching of Excited State Water.

Comparison of experimental measurements of the yield of molecular hydrogen produced in the gamma radiolysis of water and aqueous nitrate solutions with predictions of a Monte Carlo track chemistry model shows that the nitrate anion scavenging of the hydrated electron, its precursor, and hydrogen atom cannot account for the observed decrease in the yield at high nitrate anion concentrations. Inclusion of the quenching of excited states of water (formed by either direct excitation or reaction of the water radical cation with the precursor to the hydrated electron) by the nitrate anion into the reaction scheme provides excellent agreement between the stochastic calculations and experiment demonstrating the existence of this short-lived species and its importance in water radiolysis. Energy transfer from the excited states of water to the nitrate anion producing an excited state provides an additional pathway for the production of nitrogen containing products not accounted for in traditional radiation chemistry scenarios.

Scavenging the Water Cation in Concentrated Acidic Solutions.

Picosecond pulse radiolysis techniques were used to observe the kinetics of the SO4(•-), H2PO4(•), Cl2(•-), and Br2(•-) species formed in the fast oxidation of concentrated and highly acidic solutions of SO4(2-), PO4(3-), Cl(-), and Br(-). Experimental results were compared with model predictions to gain insight into the possible mechanisms occurring on the fast time scales. Simple kinetics involving the oxidizing OH(•) radical formed by radiolytic water decomposition could not account for the observed yields at the very short times (within the electron pulse ∼7 ps).