Manny Mathuthu, Ntokozo Khumalo, North-West University (Mafikeng)
Center for Applied Radiation Science and Technology (CARST)Mmabatho, 2735, South [email protected]
Determination of Lead isotope ratios for Nuclear Forensic signatures from uranium
mine products in South Africa
Overview
Aim of the Research
Objectives
Background
Methodology
Results & Discussions
Conclusions
Aim of U-Pb Isotopic Ratio TechniqueAim: 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 mineDevelop a nuclear forensics Library for U & Pb from the mineUse 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 Pbisotopic 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
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% HNO3, 9 ml of 32% HCl)
We flash with 2 ml of 2% H2O2 - 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)
MATERIALS AND METHODS
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)
RESULTSTable 1: ICP-MS Results for mining and Processing
SAMPLE IDPb Sr Th U Co
T1E1 0.129 0.18 0.044 0.68 0.32T1E2 0.076 0.10 0.044 0.62 0.28T1E3 0.072 0.16 0.038 0.60 0.33T1E4 0.076 0.16 0.042 0.72 0.49T1E5 0.053 0.20 0.043 0.46 0.26T1E6 0.089 0.10 0.040 0.04 0.23T1E7 0.096 0.13 0.039 0.23 0.36T1E8 0.071 0.12 0.042 0.00 0.34T1E9 0.131 0.17 0.055 0.94 0.28T1E10 0.105 0.13 0.088 1.37 0.57T1E11 0.086 0.28 0.048 0.23 0.41AVRG 0.090 0.16 0.048 0.53 0.35MAX 0.131 0.28 0.088 1.37 0.57MIN 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 0.18T2E2 0.175 0.18 0.038 0.50 0.21T2E3 0.172 0.35 0.051 0.46 0.45T2E4 0.159 0.20 0.064 0.68 5.19T2E5 0.052 0.11 0.049 0.46 0.23T2E6 0.041 0.09 0.050 0.68 0.25T2E7 0.069 0.13 0.043 0.69 0.25T2E8 0.087 0.25 0.059 0.83 0.33T2E9 0.077 0.12 0.039 0.00 0.20T2E10 0.100 0.20 0.058 0.61 0.31T2E11 0.075 0.15 0.043 0.70 0.24T2E12 0.281 0.09 0.044 0.23 0.48T2E13 0.086 0.22 0.045 0.84 0.41AVRG 0.111 0.17 0.047 0.55 0.67MAX 0.281 0.35 0.064 0.84 5.19MIN 0.041 0.09 0.030 0.00 0.18
STD.DEV 0.068 0.07 0.009 0.24 1.36
Sample ID 208Pb/206Pb -normalized 208Pb/206Pb normalized 208Pb/206Pb normalized207Pb/206Pb 208Pb/206Pb 204Pb/206Pb
CW4 0.8254 ± 0.0640 1.987 ± 0.0873 0.0578 ± 0.0037
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
± 0.00033
2.1681
± 0.0008
0.059042
± 0.000037
RESULTS Cont..
Table 2: Lead isotopic ratios for water samples after208Pb/206Pb normalization for mass balance.
Table 3: Water sample results relative to 204Pb for the mine area (Poujol 1999)
•Sample ID 208Pb/204Pb 207Pb/204Pb 206Pb/204Pb
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
NIST SMR 981
36.72185
± 0.0008
15.49161698
± 0.00033
16.93736
± 0.000037
Pb-Pb isotopic plot
Figure 6: A plot 207Pb/204Pb versus 206Pb/204Pb for mine (fissure) water samples.
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15.00 16.00 17.00 18.00 19.00 20.00 21.00 22.00 23.00 24.00 25.00
207P
b/20
4Pb
206Pb/204Pb
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 (206Pb/204Pb ≤ 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
A 206Pb/204Pb ratio greater than 20 indicates that Pbinvestigated 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.
CONCLUSIONS
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.
ACKNOWLEDGEMETS
Thank you!!!
