Michael Colella

Kinetics of uranium release from Synroc phases

This paper presents experimental studies on the kinetics of U release from near single-phase zirconolite, pyrochlore, brannerite and pyrochlore-rich titanate ceramic materials. The dissolution tests were conducted at 20–75°C with initial pHs from 2 to 12, and flow rates from 10 to 80 ml d−1 in the open atmosphere. The U releases from these titanate materials are controlled by initial fast process and then followed by linear kinetics. The close-to-stoichiometric U release from zirconolite and pyrochlore-rich materials and preferential U release from brannerite are consistent with the alterations observed for the natural samples. The rate constants for U releases were determined and the effects of pH and temperature were examined. For each material, the U release vs. pH exhibits a V-shape with a minimum near pH 8. The measured activation energies suggest surface reaction controlled dissolution mechanism. Pyrochlore-rich materials and zirconolite demonstrated higher chemical durability and more resistance to aqueous attack than brannerite. However, impurities and minor brannerite inclusions do not appear to have a detrimental effect on U releases from pyrochlore-rich multi-phase ceramics.

Dissolution of synthetic brannerite in acidic and alkaline fluids

Abstract The dissolution of synthetic brannerite in aqueous media at 40 and 90 °C under atmospheric redox conditions has been studied. At 40 °C, the presence of phthalate as a buffer component in the pH range of 2–6 has little effect on uranium release from brannerite. Bicarbonate increases uranium release and enhances the dissolution of brannerite. Compared to UO 2 , brannerite is more resistant to dissolution in bicarbonate solutions. In under-saturated conditions at 90 °C, the dissolution of brannerite is incongruent (preferential release of uranium) at pH 2 and nearly congruent at pH 11. TEM examinations reveal a polymorph of TiO 2 (pH 2 specimen) and a fibrous Ti-rich material (pH 11 specimen) as secondary phases. XPS analyses indicate the existence of U(V) and U(VI) species on the surfaces of specimens both before and after leaching, and U(VI) was the dominant component on the specimen leached in the pH 11 solution.

Optical emission due to ionic displacements in alkaline earth titanates

Abstract Optical emission spectra in the 300–700 nm range were collected from single crystal CaTiO 3 , SrTiO 3 and BaTiO 3 , and polycrystalline CaTiO 3 samples, that were irradiated at room temperature using a Febetron 706 variable energy pulsed-electron-beam generator. The long-lived emissions (up to microseconds after the electron pulse) consist of broad (halfwidths ∼100 nm) bands centred around 380, 425, and 445 nm for CaTiO 3 , SrTiO 3 and BaTiO 3 , respectively. These emission bands are similar to cathodoluminescence emissions from 25 keV electron irradiation attributed by others to direct conduction-valence band transitions in unreduced samples and oxygen vacancies in reduced samples. CaTiO 3 , SrTiO 3 and BaTiO 3 all have emission thresholds of 0.26±0.02 MeV. This corresponds to a threshold displacement energy for oxygen, E d of 45±4 eV.

Composition, Geochemical Alteration, and Alpha-Decay Damage Effects of Natural Brannerite

To investigate the long-term alteration behavior of brannerite, we have undertaken a study of twelve natural samples from a range of geological environments. Our results indicate that seven of the samples exhibit only minor alteration, usually within veinlets or around the rim of the sample. The remaining five samples consist of variable amounts of unaltered and altered brannerite. SEMEDX analyses of unaltered areas indicate that the chemical formulae may deviate from the ideal stoichiometry. The U content ranges from 0.45 to 0.88 atoms per formula unit (pfu). Maximum amounts of the other major cations on the U-site are 0.48 Ca, 0.22 Th, 0.14 Y, and 0.07 Ln (lanthanide = Ce, Nd, Gd, Sm) atoms pfu. The Ti content ranges from 1.86 to 2.10 atoms pfu. Maximum values of other cations on the Ti-site are 0.15 Fe, 0.14 Si, 0.09 Al, 0.06 Nb, 0.04 Mn, and 0.04 Ni atoms pfu. Altered regions of brannerite contain significant amounts of Si and other elements incorporated from the fluid phase, and up to 40-90% of the original amount of U has been lost as a result of alteration. SEM-EDX results also provide evidence for TiO 2 phases, galena, and a thorite-like phase as alteration products. Electron diffraction patterns of all samples typically consist of two broad, diffuse rings that have equivalent d-spacings of 0.31 nm and 0.19 nmi, indicating complete amorphization of the brannerite. Many of the grains also exhibit weak diffraction spots due to fine-grained inclusions of a uranium oxide phase and galena. Using the available age data, these samples have average accumulated alpha-decay doses of 2-170 × 10 16 alphas/mg. Our results indicate that brannerite is subject to amorphization and may lose U under certain P-T-X conditions, but the overall durability of the titanate matrix remains high.

In situ radiation damage studies of LaxSr1−3x∕2TiO3 perovskites

Seven perovskite samples in the LaxSr1−3x∕2TiO3 solid solution series were monitored in situ during irradiation with 1.0MeV Kr2+ ions using the intermediate voltage electron microscope-Tandem User Facility (IVEM) at Argonne National Laboratory. All the perovskites pass through the crystalline-amorphous transformation. However, the critical temperature for amorphisation Tc of the LaxSr1−3x∕2TiO3 perovskites varies nonlinearly with composition, decreasing from 394±3K for SrTiO3 to a minimum of 275±1K for La0.2Sr0.7TiO3, then increasing with composition again to 865±3K for La0.67TiO3. In combination with the work of previous authors, the electron microscopy results and IVEM data in this study suggest that there is a vacancy-assisted recovery mechanism in the cubic perovskites with compositions in the range 0<x<0.2 that may not be directly associated with the cubic-tetragonal phase transformation and that vacancy-enhanced amorphisation occurs for both cubic and orthorhombic perovskites with compositions in th...

Non-metamict zirconolite polytypes from the feldspathoid-bearing alkali-syenitic ejecta of the Vico volcanic complex (Latium, Italy)

This paper presents the results of a combined electron microprobe and analytical TEM study that describes the chemical and structural characteristics of non-metamict zirconolite from a volcanic ejectum collected within a pyroclastic formation of the Vico volcanic complex, near Tre Croci Community, Latium (Italy). The host rock is a foid-bearing alkali-syenite and consists of potassium-feldspar and plagioclase, with minor biotite, titanite, clinopyroxene and magnetite. Sodalite occurs as well-faceted crystals inside miarolitic cavities between intersecting feldspars and it is variably altered to a kaolinite-like product. Accessory minerals include zircon, baddeleyite, stillwellite, hellandite, fluorite, apatite and monazite. Zirconolite occurs both as elongated acicular crystals of orthorhombic symmetry (zirconolite-3 O ), space group Acam, with (in A) a = 10.13(1), b = 14.16(1) and c = 7.288(2), and as pseudo-hexagonal platy crystals of trigonal symmetry (zirconolite-3 T ), space group P 3 1 2, with a = 7.279(2) and c = 16.89(2). TEM studies revealed additionally the presence of polytype zirconolite-2 M in a subset of grains analyzed. Zirconolite displays pronounced compositional zoning, observed in backscattered electron images, resulting mainly from an antipathetic variation in the actinide elements (Th + U) and REE contents. Analytical TEM results indicate compositional differences exist between the zirconolite-3 T and zirconolite-2 M polytypes. Zirconolite, and associated accessory REE, Th, U minerals crystallized after the formation of the major rock-forming minerals of the ejectum, from metasomatic fluids rich in F and P.

Gamma Irradiation as a Biological Decontaminant and Its Effect on Common Fingermark Detection Techniques and DNA Profiling

Abstract:  The use of disease‐causing organisms and their toxins against the civilian population has defined bioterrorism and opened forensic science up to the challenges of processing contaminated evidence. This study sought to determine the use of gamma irradiation as an effective biological decontaminant and its effect on the recovery of latent fingermarks from both porous and nonporous items. Test items were contaminated with viable spores marked with latent prints and then decontaminated using a cobalt 60 gamma irradiator. Fingermark detection was the focus with standard methods including 1,2‐indanedione, ninhydrin, diazafluoren‐9‐one, and physical developer used during this study. DNA recovery using 20% Chelex extraction and quantitative real‐time polymerase chain reaction was also explored. Gamma irradiation proved effective as a bacterial decontaminant with D‐values ranging from 458 to 500 Gy for nonporous items and 797–808 Gy for porous ones. The results demonstrated the successful recovery of latent marks and DNA establishing gamma irradiation as a viable decontamination option.

The Recovery of Latent Fingermarks from Evidence Exposed to Ionizing Radiation

Abstract:  Continual reports of illicit trafficking incidents involving radioactive materials have prompted authorities to consider the likelihood of forensic evidence being exposed to radiation. In this study, we investigated the ability to recover latent fingermark evidence from a variety of substrates that were exposed to ionizing radiation. Fingermarks deposited on common surfaces, including aluminum, glass, office paper, and plastic, were exposed to doses ranging from 1 to 1000 kGy, in an effort to simulate realistic situations where evidence is exposed to significant doses of radiation from sources used in a criminal act. The fingermarks were processed using routine fingermark detection techniques. With the exception of glass and aluminum substrates, radiolysis had a considerable effect on the quality of the developed fingermarks. The damage to ridge characteristics can, in part, be attributed to chemical interactions between the substrate and the components of the fingermark secretions that react with the detection reagents.

Bioterrorism: The effects of biological decontamination on the recovery of electronic evidence

The investigation of a bioterrorism event will ultimately lead to the collection of vital data from electronic devices such as computers and mobile phones. This project sought to determine the use of gamma irradiation and formaldehyde gas as effective biological decontaminants, and the effect of these methods on the recovery of electronic evidence. Electronic items were contaminated with viable spores and then exposed to both decontaminants. Log values for each matrix were calculated with flash drives recording the highest value of 566 Gy for gamma irradiation and a maximum of 50 min exposure to formaldehyde saw the effective destruction of spores. The results indicate that recovery of data varied based on the decontaminant selected, formaldehyde gas giving the most promising results, with electronic data recovered after the required exposure time. Gamma irradiation proved damaging to electronic circuitry at levels required to render the items safe. The implications to computer intelligence and forensics will be discussed based on the outcomes of these findings.

Nuclear forensic analysis of uranium oxide powders interdicted in Victoria, Australia

Abstract Nuclear forensic analysis was conducted on two uranium samples confiscated during a police investigation in Victoria, Australia. The first sample, designated NSR-F-270409-1, was a depleted uranium powder of moderate purity (∼ 1000 μg/g total elemental impurities). The chemical form of the uranium was a compound similar to K2(UO2)3O4 · 4H2O. While aliquoting NSR-F-270409-1 for analysis, the body and head of a Tineid moth was discovered in the sample. The second sample, designated NSR-F-270409-2, was also a depleted uranium powder. It was of reasonably high purity (∼ 380 μg/g total elemental impurities). The chemical form of the uranium was primarily UO3 · 2H2O, with minor phases of U3O8 and UO2. While aliquoting NSR-F-270409-2 for analysis, a metal staple of unknown origin was discovered in the sample. The presence of 236U and 232U in both samples indicates that the uranium feed stocks for these samples experienced a neutron flux at some point in their history. The reactor burn-up calculated from the isotopic composition of the uranium is consistent with that of spent fuel from natural uranium (NU) fueled Pu production. These nuclear forensic conclusions allow us to categorically exclude Australia as the origin of the material and greatly reduce the number of candidate sources.