Analysis of solid uranium samples using a small mass spectrometer

A mass spectrometer for isotopic analysis of solid uranium samples has been constructed and evaluated. This system employs the fluorinating agent chlorine trifluoride (ClF₃) to convert solid uranium samples into their volatile uranium hexafluorides (UF₆). The majority of unwanted gaseous byproducts and remaining ClF₃ are removed from the sample vessel by condensing the UF₆ and then pumping away the unwanted gases. The UF₆ gas is then introduced into a quadrupole mass spectrometer and ionized by electron impact ionization. The doubly charged bare metal uranium ion (U²⁺) is used to determine the U²³⁵/U²³⁸ isotopic ratio. Precision and accuracy for several isotopic standards were found to be better than 12%, without further calibration of the system. The analysis can be completed in 25 min from sample loading, to UF₆ reaction, to mass spectral analysis. The method is amenable to uranium solid matrices, and other actinides.