We have developed a new portable instrument for the determination of UF6 levels of enrichment in the field for nuclear safeguards applications at gas centrifuge enrichment plants (GCEP). The method employs a Single-Use Destructive Assay (SUDA) sampler for collecting UF6 gas, which is absorbed as uranyl fluoride in a solid zeolite matrix, and then directly analyzed for isotope ratios. For this purpose, a small amount of the matrix is heated in a high-temperature microcrucible, which produces an atomic beam of uranium. This atomic beam is interrogated by a narrow linewidth diode laser and the isotopic absorption spectrum is measured. Our instrument then determines the enrichment level by comparing the relative contributions of 235U and 238U to the absorption signal. The analysis takes less than 10 min and there is no need for sample preparation or chemical separations. This technology is promising for bias defect enrichment determination of uranium samples collected at GCEPs.