Methods and Influencing Factors for the Simple and Rapid Identification of Depleted Uranium Weapon Use under Battlefield Conditions.

The purpose of this paper is to explore how to rapidly and easily identify depleted uranium (DU) samples under battlefield conditions and to study the factors that influence their measurement. The air-absorbed dose rate and surface contamination levels for DU samples of 2-330 g were measured using a patrol instrument and portable energy spectrometer. The results were analyzed in accordance with IAEA standards for judging radioactive substances. The energy spectra of 5-g quantities of DU samples were analyzed using a high-purity germanium gamma spectrometer, and the uranium content of 100 mg DU samples was determined with an inductively coupled plasma mass spectrometer to clarify the type and composition of the uranium. The same batches of DU samples were identified using a portable gamma-ray spectrometer. We added 0-5 g environmental soil powders at different proportions. After sealing, the spectra were collected with a detection distance of 1-5 cm for 10 min. The activities of U and U nuclides in the samples were detected with an NaI(TI) scintillation detector. The U and U mass abundances in samples were calculated from measured specific activities. The sample was determined to contain DU if the U to U ratio was below 0.00723. It is found that for detecting DU materials with a low activity, surface contamination level measurements are more effective than calculating the air-absorbed external irradiation dose rate. Hence, for low-activity samples suspected to be radioactive, a radiometer with a high sensitivity for surface contamination is recommended, and the optimal measurement distance is 1-3 cm. Under all detection conditions, U can be identified using a portable gamma spectrometer, whereas U can only be detected under certain conditions. If these nuclides can be detected simultaneously, a U to U ratio of below 0.00723 indicates the presence of DU. The main factors affecting this identification include the sample mass, sample purity, measurement distance, and measurement time. For the rapid identification of DU with a portable gamma-ray spectrometer, the mass of uranium in the sample must be more than 1 g, the measuring distance needs to be less than 1 cm, and the measuring time must be 1-10 min. It is feasible to use a portable gamma-ray spectrometer to rapidly identify the types and composition of nuclides in DU samples. The detection of U activity is a precondition for the identification of DU.

First-principle atomistic thermodynamic study on the early-stage corrosion of NiCr alloy under fluoride salt environment.

The atomic morphology change in the NiCr alloy surface induced by fluorine-chemisorption was investigated by the ab initio atomistic thermodynamic method to elucidate early-stage corrosion processes of nickel-based alloys in strong oxidizing environment. The surface phase diagrams of Cr-doped Ni(111) surface as a function of fluorine chemical potential were obtained to track the surface structures that are most likely to be fostered in various temperature and pressure conditions. The adsorption of fluorine on the top site of Cr in the alloy surface was the most energetically favorable one. With increasing fluorine chemical potential, more fluorine atoms started to agglomerate in the trapping sink of Cr. Fluorine-fluorine repulsion interaction coupled with strong F-Cr bonding could facilitate a decided morphology modification of the metal substrate. Moreover, an insight into the desorption pathways for potential species revealed that in the presence of fluorine, the dissociation of Cr predominantly stems from the relatively easy desorption in the form of CrF2/CrF3 molecules from the non-passivated Ni-based alloy surface.