Determination of Lead isotope ratios for Nuclear Forensic ...lsc2017.nutech.dtu.dk/wp-content/uploads/2-MATHUTHU-LSC2017... · Introduction Cont… Nuclear forensics Here we describe

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!!!