Application of inductively coupled plasma mass spectrometry (ICPMS) for determination of rare earth element pattern in uranium ore and uranium ore concentrate (UOC) samples for origin assessment

Illicit trafficking of radioactive/nuclear materials in recent years poses global concern due to the associated radiotoxicity and concern of nuclear proliferation. In this context, Nuclear Forensics (NF) plays an important role in providing technical evidences to trace the origin and intended use of the intercepted material for legal action. A significant interest appears in NF to trace the origin of UOC (Yellow cake) as these materials are the important intermediate materials in nuclear fuel cycle and represent the most common form of interdicted materials. Uranium, stable isotopic ratio and trace elemental impurities in UOC are generally used for its attribution. Chondrite normalized Rare Earth Element (CN-REE) pattern is used as an important forensic tool in discriminating between different types of uranium deposit as well as different uranium mines because of their tendency to fractionate within uranium oxide. Rare earth elements having similar chemical properties do not show significant elemental fragmentation or pattern change during milling process used for the fabrication of UOC. Therefore, REE pattern is used for origin assessment of UOC. Few literature studies also demonstrated comparable REE pattern in the UOC to that of the corresponding ore from which it is originated. Another important aspect of REE pattern as a forensic tool is, not only it can help to identify the origin of unknown UOC or ore by comparing with known material but also can be useful in absence of known material because of its uniqueness associated with the ore deposit type. Most common techniques used for REE determination in uranium materials are ICP-MS, ICP-OES, XRF and NAA. Among those ICPMS is the most powerful techniques in REEs determination because of its high sensitivity, large dynamic linear range, multi-element capability and possibility to perform isotopic measurements. However, any interference or matrix effect arising from ICPMS analysis can be solved with high resolution, reaction/collision cells and matrix separation. Present study focuses on the determination of REE concentration in uranium rich matrices (uranium ore and UOCs) using ICPMS. Direct microwave digested ore samples were used for determination of REE concentration whereas uranium separation was carried out using ion exchange chromatography for UOCs for analysis in ICPMS. CN-REE pattern was obtained for uranium ore samples collected from different mines at Singhbhum Shear Zone (SSZ) and was compared with REE pattern of indigenously prepared UOCs from two different milling plants using ores from above mines. (author)