The NanoSIMS secondary ion mass spectrometer, with a nanometer-scale spatial resolution, was used to measure the F + /U + secondary ion ratio of individual particles immediately after sample preparation, and at different time intervals.

Expressly for the purpose of this work, we prepared a set of UO 2 F 2 particle samples from the hydrolysis of UF 6 and stored these samples in environmental chambers at different temperature, humidity and lighting conditions. This study aims to determine how those environmental conditions affect the relative amount of fluorine in UO 2 F 2 particles. As fluorine is not always detected in uranium particles originating from enrichment facilities, it is assumed that UO 2 F 2 is unstable under certain environmental conditions. Additional and complementary information on the particles' source, formation process and exposure history can be obtained from elemental, molecular and morphological analysis. Despite their small size, the uranium isotopic composition of these particles is used to determine whether an enrichment facility is compliant with its declarations. The UO 2 F 2 particles settle on various surfaces within the enrichment facility where they are collected by safeguards organizations such as the International Atomic Energy Agency (IAEA) through a technique called environmental sampling. When a small amount of UF 6 is released in the environment, it forms uranium oxyfluoride (UO 2 F 2 ) particles and hydrogen fluoride from the reaction with atmospheric moisture.

Gaseous uranium hexafluoride (UF 6 ) is used for the enrichment of uranium and is known to be a very reactive and volatile gas. The question concerning whether there will be a future role for the current form of the periodic table in predicting chemical properties and aid in the identification of elements beyond those currently known is considered. Mendelevium still remains the heaviest element to have been identified first by chemical rather than nuclear or physical techniques. The discoverers proposed the name mendelevium to honor the predictive power of the Mendeleev Periodic Table. It is noteworthy that the element with Z =101 (mendelevium) was identified in 1955 using chemical techniques. The value, as well as the sometimes negative effects, of periodic tables in guiding the discovery of new elements based on their predicted chemical properties is assessed. The history of the development of periodic tables of the chemical elements is briefly reviewed beginning with the presentation by Dmitri Mendeleev and his associate Nikolai Menshutkin of their original 1869 table based on atomic weights. It also marks the 175 th anniversary of his birth in Tolbosk, Siberia. This year (2009) marks the 140 th Anniversary of Mendeleev's original 1869 periodic table of the elements based on atomic weights.

Keymaker indir dosya tc