As a major component in the nuclear fuel cycle, octoxide uranium is subjected to intensive nuclear forensics research. Scientific efforts have been mainly dedicated to determine signatures, allowing for clear and distinct attribution. The oxygen isotopic composition of octoxide uranium, acquired during the fabrication process of the nuclear fuel, might serve as a signature. Hence, understanding the factors governing the final oxygen isotopic composition and the chemical systems in which U3O8 was produced may develop a new fingerprint concerning the history of the material and/or the process to which it was subjected. This research determines the fractionation of oxygen isotopes at different temperatures relevant to the nuclear fuel cycle in the system of U3O8 and atmospheric O2. We avoid the retrograde isotope effect at the cooling stage at the end of the fabrication process of U3O8. The system attains the isotope equilibrium at temperatures higher than 300 °C. The average δ18O values of U3O8 in equilibrium with atmospheric oxygen have been found to span over a wide range, from −9.90‰ at 300 °C up to 18.40‰ at 800 °C. The temperature dependency of the equilibrium fractionation (1000 ln αU3O8‑atm. O2 ) exhibits two distinct regions, around −33‰ between 300 °C and −500 °C and −5‰ between 700 °C and −800 °C. The sharp change coincides with the transition from a pseudo-hexagonal structure to a hexagonal structure. A depletion trend in δ18O is associated with the orthorhombic structure and may result from the uranium mass effect, which might also play a role in the depletion of 5‰ versus atmospheric oxygen at high temperatures.

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The structure of chemical-vapor-deposited (CVD) WSi 2 in a multilayered configuration of Si/SiO 2 /polySi/WSi 2 /poly-Si was analyzed by X-ray diffraction (XRD). Individual layers of this multilayered structure were deposited sequentially on separate wafers, and the changes occurring in WSi 2 at each stage of the fabrication process were determined by XRD in the as-deposited and annealed conditions. The XRD line broadening was used to construct the Williamson-Hall (WH) plots. As a first approach to get introductory information, reflections from all planes observed by the XRD analysis were used to evaluate, by the WH technique, the mean domain size and the microstrain, respectively. At the next stage, WH plots were constructed by using planes of crystallographic families for two cases, namely, for partially crystallized and for fully crystallized multilayered films. It seems that when the film is well annealed, with small or no anisotropy, all the plains can be used to evaluate strain and domain size by the WH method, and it can provide almost the same results as those obtained from using XRD reflections only from planes of a family. This is the first time that that this well-known method has been applied to silicide films.

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"Spot samples" of urine are routinely used to monitor occupational exposure to uranium and other toxic heavy metals, such as mercury, lead, and cadmium. In the present work, it was shown that diurnal variations in the uranium concentration in different urine samples from the same individual could be quite large. However, these variations were in correlation to the creatinine level of the same samples, with values of R = 0.72-0.99, for the five subjects studied here. Thus, it is proposed here that uranium concentrations in "spot" urine samples be expressed in terms of ng uranium g(-1) creatinine rather than ng uranium L(-1). Once the 24-h creatinine level is estimated for the individual based on weight, height and age, the adjusted values can be used for determination of the internal dose of uranium.