Uranium oxide particles

Carbide-based cermets have particles of carbides of tungsten, chromium, and titanium. Tungsten carbide in a cobalt matrix is used in machine parts requiring very high hardness such as wire-drawing dies, valves, etc. Chromium carbide in a cobalt matrix has high corrosion and abrasion resistance it also has a coefficient of thermal expansion close to that of steel, so is well-suited for use in valves. Titanium carbide in either a nickel or a cobalt matrix is often used in high-temperature applications such as turbine parts. Cermets are also used as nuclear reactor fuel elements and control rods. Fuel elements can be uranium oxide particles in stainless steel ceramic, whereas boron carbide in stainless steel is used for control rods. 

In the earlier history of the earth, up to perhaps 1.4x 10 years ago, there was almost no oxygen in the atmosphere and uranium oxides could exist at the surface of the earth as grains or nuggets without being oxidized from their 4+ state into the soluble 6+ state. As such, these uranium oxide particles could travel in streams and because of their density they were segregated from less dense materials in streams, in the same way that Au collects in placer deposits. With time these stream deposits were buried, thrust deep into the ground and metamorphosed into the type of accumulation called a quartz... 

The density of the particle also influences the amount of deposition and retention of particulate matter in the lungs upon inhalation. Particles of high density behave as larger particles of smaller density on passage down the respiratory tract by virtue of the fact that their greater mass and consequent inertia tend to impact them on the walls of the upper respiratory tract. Thus a uranium oxide particle of a density of 11 and 1 pm in diameter wiU behave in the respiratory tract as a particle of several microns in diameter, and thus its pulmonary deposition wiU be less than that of a low density particle of the same size. 

Tamborini, G, et al. (2000) SIMS characterization of in-house monodispersed isotopic standard uranium oxide particles. 995-998. 

Highlights. Uranium oxide particles that are the most common form of nuclear fuel can be characterized by spectroscopic methods (NIR and Raman) with or without a combination of SEM and the isotopic composition of oxygen is also an indicator of the geographic source. The production process used in the manufacture of the particles is reflected in the analysis and can thus help to identify the origin of the particles. It should be noted that the analytical method used may have an effect on the particle consistence and morphology and should thus be used with care. 

Laser ablatiou-ICPMS has beeu applied to measurement of the isotopic composition and U) of single uranium oxide particles with dimensions... 

FIGURE 5.13 (a) The dark field image of an FTA detector in an optical microscope of uranium oxide particles (10% 0.8 pm diameter) irradiated for 90 s. The number near each... 

Hocking, H.E., Burggraf, L.W., Duan, X.F. et al. (2012). Composition of uranium oxide particles related to TOF-SIMS ion distribution. Surf. Interface Anal. 45, 545-548. 

Stetzer, O., Betti, M., van Geel, J. et al. (2004). Determination of the content in uranium oxide particles by fission track analysis, Nucl. Instrum. Methods Phys. Res. A 525, 582-592. 

Find the pore size distribution of pellets of uranium oxide with these properties. True density = 7.57 g/cc, particle density =3.2 g/cc, porosity = 57.8% Measurements were made of the penetration of Mercury, cc/gm of pellet, against pressure in psi. 

The results of uranium isotope ratio measurements by MC-TIMS (TRITON Thermo Fisher Scientific) on a single uranium oxide reference particle (10 pan) are illustrated in Figure 8.5.9,144 The high precision of multiple ion counters and high detection power in the MC-TIMS are... 

The two Windscale piles were fuelled with natural uranium canned in aluminium. Coolant air was blown through the reactor and exhausted from a 120-m stack (Fig. 2.4). Filters were installed at the top of the stack, but were not very effective. Some fuel cans developed pinholes during operation, and others became damaged and lodged in the ducts behind the pile. It is estimated that about 20 kg of irradiated uranium were disseminated to atmosphere as oxide particles from these cans (Stather et al., 1986). The temperature of oxidation was 200-400°C. The particle size, measured at the top of the stack, showed a mass median diameter of 35 fim (Mossop, 1960). 

The particle size of Pu aerosols is very variable, depending on the mode of formation. In Fig. 5.2, curves A, B and C show size spectra obtained by Carter Stewart (1971) in laboratory experiments on the oxidation of Pu metal in air. In controlled oxidation at temperatures below the ignition point (about 500°C), scaly, friable, oxide particles were produced, with median diameter increasing with temperature. Few particles less than 1 jum in diameter were found. When the delta alloy of Pu was used, the oxide was more adherent, and the particle size larger. Increase of particle size with increase of temperature was also found in laboratory oxidation of uranium metal (Megaw et al., 1961), and was ascribed to sintering of the oxide layer. 

SIMS is mostly employed for microlocal analytical investigations. For example, isotope ratio measurements by SIMS have been performed in nuclear forensic studies to determine the age of Pu particles." For the age determination of Pu particles, relative sensitivity coefficients (RSC) were determined as correction factors for the different ionization efficiency of Pu compared to U. The age of a sample of known origin calculated from Pu/ " and °Pu/ U ratios agreed well with the reported age of 2.3 years." SIMS was employed for oxygen isotope ratio measurements in three different uranium oxide microparticles of nuclear forensic interest by Betti s working group." The... 

Undoubtedly the most unlikely substrate for ferritin is U02 +, however, the imphcations of biomimetically synthesizing uranium oxide loaded ferritin could have use in neutron capture therapy. The synthetic approach utilized ion binding of U02(02CCH3)2 according to a known stoichiometry of 12 ions per ferritin molecule, followed by hydrolytic polymerization of metal ions within apo-ferritin. Characterization by TEM analysis confirmed dense cores of polymerized uranyl oxyhydroxide particles of 6 nm in diameter. 

Oughton D. H., Salbu B., Brand T. L., Day J. P., and Aarkrog A. (1993) Underdetermination of Strontium-90 in soils containing particles of irradiated uranium oxide fuel. Analyst 118, 1101-1105. 

---