Determination of Lead isotope ratios for Nuclear Forensic signatures - PowerPoint PPT Presentation

Determination of Lead isotope ratios for Nuclear Forensic signatures from uranium mine products in South Africa Manny Mathuthu, Ntokozo Khumalo, North-West University (Mafikeng) Center for Applied Radiation Science and Technology (CARST) Mmabatho, 2735, South Africa. Manny.Mathuthu@nwu.ac.za

Overview  Aim of the Research  Objectives  Background  Methodology  Results & Discussions  Conclusions

Aim of U-Pb Isotopic Ratio Technique Aim: To Determine Lead isotope ratios for Nuclear Forensic signatures for South African Uranium Mining and Processing. Objectives are to:  Resolve the U, Pb isotopic ratio for nuclear forensics signatures for the mine  Develop a nuclear forensics Library for U & Pb from the mine  Use Library to trace origin of interdicted nuclear material

Introduction: Uranium deposits  In South Africa there is a vast uranium ore (uraninite) deposits (Fuchs, Williams-Jones et al. 2016), with a lot of mining and processing activities.  It is therefore imperative for South Africa to properly collect and compile databases and national libraries for nuclear forensic signatures  These can be used as evidence for attribution of the seized nuclear or radioactive material.  the Carletonville Gold field) in South Africa has been investigated by Researchers like Fuchs et. al. (2016)  He used a LA-ICP-MS to measure trace elements (provenance of uranium) on the Transvaal Supergroup  Results showed that the higher U and gold concentrations are embedded in the pyrite rock (Fuchs, Williams-Jones et al. 2016).

Introduction Cont… Nuclear forensics  Results from the first stage in the fuel cycle are described,  the data presented could form a basis for a South African nuclear forensics library.  However, all the stages in the fuel cycle need to be investigated to produce a comprehensive nuclear forensic library.  Here we describe the investigation of Pb isotopic composition and trace elemental analysis to determine respectively the fingerprint lead signatures and the provenance of the uranium in the uraninite ore.

Introduction Cont… Nuclear forensics  Here we describe the investigation of Pb isotopic composition and trace elemental analysis  the fingerprint lead signatures and the provenance of the uranium in the uraninite ore is discussed.  Interpretation of the results for possible tracing (attribution) of the origins of South African Pb is presented.  Finally the limitations of Pb isotopic fingerprinting technique in this work (Cheng and Hu 2010) of the technique are outlined

MATERIALS AND METHODS  Isotopic Techniques). Many Instruments are being used to apply various analytical techniques for chronometric analysis of intercepted nuclear materials from a nuclear facility. For example (Andersen 2002, Balcaen, Moens et al. 2010, Varga, Katona et al. 2010):  The laser ablation (LA ICP-MS) instruments and the  The laser-ablation micro-sampling (LAM-ICP- MS)  Perkin Elmer NexION 300Q ICP-MS Isotopic ratio analysis used for determining the lead isotopic signatures of the sample material

MATERIALS AND METHODS  Interference correction and digestion  the oxides, hydrides, hydroxides and nitrides molecular ions are potential sources of interferences;  Aqua Regia acid (3 ml of 55% HNO 3 , 9 ml of 32% HCl)  We flash with 2 ml of 2% H 2 O 2 - which enhances the oxidation properties of nitric acid  The aqua regia extraction is capable of complete recovery for Cd, Cu, Pb (our target element) and Zn (Gaudino, Galas et al. 2007)  The EPA Method 3052 used in the sample digestion achieves total sample decomposition (Mangum 2009)

Study Area Figure 1: Study Area showing sampling points

SAMPLING PATTERN Figure 2: : Sampling the Tailing slurry

(B) Gamma spectroscopy for isotopic ratio analysis – Figure 3: Instrument : The High Purity Germanium Detector (HPGe) { Canberra Model GCW 2021 HPGe Well detector }

Equipment Used (A) ICP-MS for major and trace elements Figure 4: Instrument: NexION 300Q ICP-MS (Perkin Elmer)

RESULTS Table 1: ICP-MS Results for mining and Processing SAMPLE ID Pb Sr Th U Co T1E1 0.129 0.18 0.044 0.68 0.32 T1E2 0.076 0.10 0.044 0.62 0.28 T1E3 0.072 0.16 0.038 0.60 0.33 T1E4 0.076 0.16 0.042 0.72 0.49 T1E5 0.053 0.20 0.043 0.46 0.26 T1E6 0.089 0.10 0.040 0.04 0.23 T1E7 0.096 0.13 0.039 0.23 0.36 T1E8 0.071 0.12 0.042 0.00 0.34 T1E9 0.131 0.17 0.055 0.94 0.28 T1E10 0.105 0.13 0.088 1.37 0.57 T1E11 0.086 0.28 0.048 0.23 0.41 AVRG 0.090 0.16 0.048 0.53 0.35 MAX 0.131 0.28 0.088 1.37 0.57 MIN 0.053 0.10 0.038 0.00 0.23 STD.DEV 0.024 0.05 0.014 0.41 0.10 T2E1 0.068 0.14 0.030 0.54 0.18 T2E2 0.175 0.18 0.038 0.50 0.21 T2E3 0.172 0.35 0.051 0.46 0.45 T2E4 0.159 0.20 0.064 0.68 5.19 T2E5 0.052 0.11 0.049 0.46 0.23 T2E6 0.041 0.09 0.050 0.68 0.25 T2E7 0.069 0.13 0.043 0.69 0.25 T2E8 0.087 0.25 0.059 0.83 0.33 T2E9 0.077 0.12 0.039 0.00 0.20 T2E10 0.100 0.20 0.058 0.61 0.31 T2E11 0.075 0.15 0.043 0.70 0.24 T2E12 0.281 0.09 0.044 0.23 0.48 T2E13 0.086 0.22 0.045 0.84 0.41 AVRG 0.111 0.17 0.047 0.55 0.67 MAX 0.281 0.35 0.064 0.84 5.19 MIN 0.041 0.09 0.030 0.00 0.18 STD.DEV 0.068 0.07 0.009 0.24 1.36

RESULTS Cont.. Table 2: Lead isotopic ratios for water samples after 208 Pb/ 206 Pb normalization for mass balance. 208 Pb/ 206 Pb -normalized 208 Pb/ 206 Pb normalized 208 Pb/ 206 Pb normalized Sample ID 207 Pb/ 206 Pb 208 Pb/ 206 Pb 204 Pb/ 206 Pb 0.8254 ± 0.0640 1.987 ± 0.0873 0.0578 ± 0.0037 CW4 WV14 0.8738 ± 0.0734 2.0187 ± 0.0978 0.0574 ± 0.0025 DAM31/3 0.8154 ± 0.0673 1.9487 ± 0.0732 0.0586 ± 0.0037 WV13 0.8271 ± 0.0782 2.0426 ± 0.0895 0.0623 ± 0.0047 DSW9/14 0.8128 ± 0.0687 1.8810 ± 0.0852 0.0411 ± 0.0023 DSW21/11 0.8187 ± 0.0675 1.9329 ± 0.0789 0.0493 ± 0.0038 DSW199 0.8454 ± 0.0674 2.0693 ± 0.0796 0.0602 ± 0.0046 DSW7/12 0.8958 ± 0.0596 2.0564 ± 0.0864 0.0581 ± 0.0039 DSW43/19 0.8638 ± 0.0769 2.0558 ± 0.0897 0.0536 ± 0.0047 DSW39/17 0.8320 ± 0.0694 2.0753 ± 0.0786 0.0532 ± 0.0037 DSW18/3 0.8528 ± 0.0654 2.0837 ± 0.0698 0.0577 ± 0.0051 DSW4/5 0.8601 ± 0.0684 2.0678 ± 0.0944 0.0590 ± 0.0034 AVER 0.8436 ± 0.0598 2.0183 ± 0.0897 0.0557 ± 0.0051 SDEV 0.0261 0.0660 0.0058 %RSD 3.0962 3.2722 10.3423 NIST SRM 981 0.91464 2.1681 0.059042 ± 0.00033 ± 0.0008 ± 0.000037

Table 3: Water sample results relative to 204 Pb for the mine area (Poujol 1999) 208 Pb/ 204 Pb 207 Pb/ 204 Pb 206 Pb/ 204 Pb Sample ID CW4 34.36 14.27 17.29 • WV1/4 35.14 15.21 17.41 WV1/3 32.79 13.28 16.05 DAM3/13 33.24 13.91 17.06 DSW9/14 45.78 19.78 24.34 DSW21/11 39.17 16.59 20.27 DSW19/9 34.38 14.04 16.61 DSW7/12 35.40 15.42 17.21 DSW43/19 38.38 16.13 18.67 DSW39/17 38.98 15.63 18.78 DSW18/3 36.14 14.79 17.34 DSW45/1 35.02 14.57 16.94 AVER 36.56 15.30 18.16 SDEV 3.59 1.71 2.25 36.72185 15.49161698 16.93736 ± 0.0008 ± 0.00033 ± 0.000037 NIST SMR 981

Pb-Pb isotopic plot 24.00 22.00 20.00 207Pb/204Pb 18.00 16.00 14.00 12.00 10.00 15.00 16.00 17.00 18.00 19.00 20.00 21.00 22.00 23.00 24.00 25.00 206Pb/204Pb Figure 6: A plot 207 Pb/ 204 Pb versus 206 Pb/ 204 Pb for mine (fissure) water samples.

Discussions on ICP-MS Results  The concentration of uranium is below 10 ppm for both tailing dam 1 and 2- absence of blackshale deposit  The results from Table 1 & 2, show that all the DWS water samples from this mine have lead isotopic ratios close to the NIST SRM 981 values.  Table 3, shows that the uranium ore mineralisation is a pyrite, with Pb ratios similar to that found by Jopoul et al. (Poujol 1999).  The isotopic signatures are less radiogenic ( 206 Pb/ 204 Pb ≤ 20).  Also the Pb-Pb plot for these results (see our Fig. 3), confirm that the Carletonville gold fields are pyrite deposits, giving another signature for this mine

CONCLUSIONS  A 206Pb/204Pb ratio greater than 20 indicates that Pb investigated emanates from a uranium ore  A 206Pb/204Pb ratio less than 20 indicates a Pb- rich ore (Bellucci, Simonetti et al. 2013)  The lead isotopic composition of water direct from the mine shaft varied largely from those from the borehole or purified water.  Thus this can be applied as a parameter to distinguish ore bodies from different origins.

ACKNOWLEDGEMETS  Authors would like to acknowledge the International Atomic Energy Authority for sponsoring this Project under CRP J2003.  We also acknowledge the Faculty Research Committee for providing part of the sponsorship to this conference.

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