Radiometric Method for the Determination of Uranium in Soil and Air: Single-Laboratory Evaluation and Interlaboratory Collaborative Study

摘要

Results of a single-laboratory evaluation and an interlaboratory collaborative study of a method for determining uranium isotopes in soil and air samples are presented. The method is applicable to 10-gram soil samples and to both glass fiber and polystyrene air filter samples. Sample decomposition is accomplished with a nitric-hydrofluoric acid dissolution. After a solvent extraction step to remove most of the iron present, the uranium is isolated by anion exchange chromatography and electrodeposition. Alpha spectrometry is used to measure the uranium isotopes. Two soil samples, a glass fiber air filter sample, and a polystyrene air filter sample were used to evaluate the method for uranium concentrations ranging from a few tenths to about one hundred disintegrations per minute (dpm) per sample. Tracer recoveries for the single-laboratory evaluation averaged 78 percent, while the tracer recoveries for the collaborative study averaged 66 percent. Although the precision of the collaborative study results did not approach counting statistics errors, the measured uranium concentrations for these samples agreed to within 5 percent of the reference concentrations when the uranium concentration was greater than one dpm per gram of soil or one dpm per air filter.