Analytical approach for 226Ra, 228Ra and 210Pb measurements for environmental monitoring using liquid scintillation spectrometry.

Uranium and thorium mining and milling facilities are required to monitor naturally occurring radionuclides (like natU, 226Ra, 228Ra and 210Pb) as part of their Environmental Radiological Monitoring Programs (ERMP), both under routine conditions and during discharge of radioactive effluents or emergency situations. In this work, a rapid and robust analytical method was developed for the determination of 226Ra, 228Ra, and 210Pb in various environmental matrices using liquid scintillation spectrometry. The methodology was specifically designed and validated in accordance with the ERMP requirements of the Uranium Concentration Unit (URA) operated by Brazilian Nuclear Industries (INB). Key performance parameters including chemical recovery, detection limits, counting efficiency, and analytical turnaround time were thoroughly evaluated. Radiochemical separations of radium and lead achieved average chemical yields of approximately 87%, while counting efficiencies reached 90% for 226Ra, 55% for 228Ra, and 84% for 210Pb in GCT high-efficiency counting mode. The total analysis time was less than 24 h, demonstrating the method's suitability for both routine monitoring and rapid response scenarios. The procedure was successfully applied to diverse environmental samples, such as rainwater surface waters, groundwater, sediments, process liquids and treated effluents. Radionuclide activity concentrations were highest in process liquids and treated effluents, whereas surface and rainwater samples showed significantly lower levels. 228Ra activity concentrations were generally low in most monitored matrices. The results were consistent with literature data reported for uranium mining and milling sites in comparable geological and operational contexts, providing no evidence of URA radiological impact on the environment. This study reinforces the importance of rapid and accurate radionuclide monitoring to ensure environmental safety and regulatory compliance in uranium mining operations.