Compact Analyzer Tracks Uranium Levels in Mine Resin On-Site

In-situ recovery (ISR) mining pumps uranium-bearing solution to the surface, where ion-exchange resins capture the dissolved uranium. Standard laboratory analysis can take hours to days. Researchers led by Prof. Daqian Hei at Lanzhou University, with colleagues at East China University of Technology, the Beijing Research Institute of Chemical Engineering and Metallurgy, and Nanjing Tech University, built a compact prompt gamma-ray neutron activation analysis (PGNAA) system that measures elements beside a resin adsorption tower, reported in the journal Advanced Scientific Instruments.

The sealed cylindrical measurement head is 237 cm long, 17.5 cm in diameter and weighs about 80 kg; it was installed vertically in a bypass loop, versus conventional cross-belt PGNAA analyzers exceeding 6 cubic meters and 6,000 kg. Two He-3 proportional counters track thermal and epithermal neutrons, whose ratio quantifies uranium from prompt fission neutrons. For other elements, a LaBr3(Ce) detector and a BGO detector together cover the prompt-gamma spectrum, combining LaBr3's finer resolution with BGO's higher efficiency.

In laboratory calibration with eight uranium standards from 0.161 to 15.28 g/L, the neutron count ratio showed a linear response with R² = 0.9965. For a 60-second measurement, the uranium detection limit was 0.129 g/L at 95% confidence, with relative uncertainty below 3.26% within the calibration range.

The system was then tested in a bypass loop at a commercial uranium ISR mine, yielding about 100 daily datasets across a first adsorption stage, elution, resin transformation and a second adsorption stage. Over the roughly 80-day first adsorption stage, uranium concentration rose through four stages to a maximum of 74.1 g/L before stabilizing near 70 g/L; a five-day elution stage brought it below 0.3 g/L. Calcium, iron, silicon, magnesium and aluminum rose during adsorption and fell during elution; sulfur and chlorine did the opposite.

The authors note the setup samples a side stream rather than the full tower inventory. Future work will focus on reducing probe diameter for direct insertion into standard process piping.