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3. Material and Methods

3.2. Investigated materials

3.2.1. Uranium Ore Concentrates

The investigated uranium ore concentrates (UOCs) originated from a total of 48 different facilities across 17 countries, with varying chemical composition. They were available at EU Commission JRC, Karlsruhe.

Table 5 lists the UOCs used in this study, along with information of their origin, chemical composition, label used in the analysis, and whether they were acquired with scanning electron microscope (SEM) or hyperspectral imaging (HSI). A priori information used for colour categorization of the UOCs was provided by Lorenzo Fongaro, EU Commission JRC Karlsruhe.

In his paper Image texture analysis and colorimetry for the classification of uranium ore concentrate powders a method for classifying UOCs by their colour was proposed. This was done by applying hierarchical clustering on measurements taken by a spectrophotometer on the UOCs (Marchetti, et al., 2019). The paper reports that six colour classes were found. In this study, UOCs from five of these classes are investigated. To prevent confusion, the colour classes from the study will be named colour categories throughout this thesis, while classes refer to the sample’s origin.

The UOCs for each facility were distributed into sample holders as preparation before image acquisition as illustrated in Figure 5. Most of the facilities were represented by three sample holders, but not all UOCs had enough quantity to be distributed into more than two sample holders.

As Table 5 shows, both pressed and unpressed UOCs were used. The meaning of “pressed” is that sample preparation of UOCs included some sort of pressing (Fongaro, Ho, Kvaal, Mayer, &

Rondinella, 2016). Images of unpressed UOCs were acquired after it was concluded that the pressed sample preparation practice was suboptimal, according to Lorenzo Fongaro. In this study, the pressed UOCs are only used in the initial analysis along with unpressed UOCs belonging to the same facility for comparison.

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Figure 13: Illustration of the distribution of UOC into three sample holders.

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Table 5: The UOCs investigated in this study. Information of their respective colour category, labels used in the analysis, origin, chemical composition, whether they were acquired with SEM or HSI, and ID No. is shown. The ID number is important to discriminate the hyperspectral images from each other as their filenames include this number but no abbreviation for origin. There are three columns containing label names because the image filenames were not named consistently. The abbreviation n.d. means

“not declared”. It was observed that the labelling of UOC from Rossing (Namibia) seems to be wrong as both prefixes “Nia” and

“Sa” occurred. The labels are derived from the filenames of the images.

SEM Labels HSI Labels

NiaRos SaROS Namibia Rossing Peroxide Yes No 5

Zam_Min Zambia Mindola Peroxide No Yes 6

USAPet UsPET USA Pathfinder Peroxide Yes No 9

SAfPal SaPAL S.Africa Palabora Peroxide Yes No 13

AusQue AuQUE Australia Queensland Peroxide Yes No 17

CanKel CaKEL Can_Key Canada Key Lake Peroxide Yes Yes 21

ChiHeY ChHEY Chi_Hen China Hengyang Peroxide + Oxide Yes Yes 22

YugSpB YuSPB Yogoslavia Spisak Black Peroxide Yes No 26

AusOlD AuOLD Aus_Oly Australia Olympic Dam Peroxide Yes Yes 28

USAAtl UsATL USA Atlas Peroxide + Oxide Yes No 57

AusMak AuMAK Australia Mary Kathleen Peroxide Yes No 58

USAFAP UsFAP USA Federal American Partners Peroxide Yes No 62

SAfNuf SaNUF S.Africa Nufcor Peroxide Yes No 69

RusTex RuTEC Rus_Tec Russia Techsnab Peroxide Yes Yes 70

Yeelir Australia Yeelirre n.d. Yes No 4

Cotter USA_Cot USA Cotter n.d. Yes Yes 7

BeCong Belgian Congo Hydroxide Yes No 14

Nucleb Bra_Nuc Brazil Nuclebras ADU Yes Yes 15

Wismut Ger_Wis Germany Wismut ADU Yes Yes 18

CaDyno Can_Dyn Canada Dyno n.d. Yes Yes 20

Can_Sun Canada Sunnar Hydroxide No Yes 25

Can_Far Canada Faraday Hydroxide No Yes 27

SpisYe Yog_Spi Yogoslavia Spisak-Yellow ADU Yes Yes 29

Fallsc USA_Fal USA Falls City n.d. Yes Yes 31

USAESI USA ESI ADU Yes No 34

macass Canada Macassa Hydroxide Yes No 35

Anacon USA Anaconda ADU Yes No 36

RadiHi Aus_Rad Australia Radium Hill ADU Yes Yes 40

RumJun Aus_Run Australia Run Jungle n.d. Yes Yes 65

Yog_Rud Yogoslavia Rudnik ADU No Yes 72

KMcGee USA Kerr McGee ADU Yes No 2

SpaGen Spa_Gen Spain Gen ADU Yes Yes 3

GabEFI Gabon EFI(Mouand) ADU Yes No 8

Can_Nor Canada North Span Hydroxide No Yes 41

Ellwel Ger_Hel Germany Helwiler ADU Yes Yes 45

Ransta Swe_Ran Sweden Ranstadt SDU Yes Yes 53

Deniso Canada Denison ADU Yes No 56

Millik Can_Mil Canada Milliken Lake ADU Yes Yes 64

southa Aus_S A Australia S Alligator Hydroxide Yes Yes 73 Romani Rum_Rum Rumania Rumania SDU + Oxide Yes Yes 76

StanRo Canada Stamrock ADU Yes No 10

HDelft Holland Delft ADU Yes No 11

ElMesq USA El Mesquite n.d. Yes No 54

USDawn USA Dawn ADU Yes No 63

Irigar USA_Iri USA Irigaray Peroxide Yes Yes 33

UMobil USA_Mob USA Mobil Peroxide Yes Yes 38

Rabbla Canada Eldore(Rabbit Lake) Peroxide Yes No 51 EverYe USA_Eve USA Everestr-Yellow Peroxide Yes Yes 52 Color category 6 (Light Yellow- White)

Colour category 5 (Yellow- Light Yellow) Colour category 4 (Dark Yellow-Yellow)Colour category 3 (Light Brown-Dark Yellow)Colour category 1 (Black-Dark Brown)

Composition SEM HSI ID No.

Unpressed Pressed

SEM labels Country Facility

26 3.2.2. Image acquisition

3.2.2.1. Scanning electron microscope images

Unpressed SEM images were acquired from five regions for each sample holder, as illustrated in Figure 14. Within these regions, at least three images at different magnification were acquired.

These three images originating from the same area in the sample holder overlapped, as depicted in Figure 15. Some UOCs were acquired at the four magnifications 100x, 250x, 500x, and 1000x.

Only three magnifications per sample were used in this study, due to inconsistent practices. By doing this, the UOCs belonging to the same colour category had the same origin across the acquired magnifications. The underlying cause of inconsistent acquisition across the magnifications was that during 1000x magnification particles of the UOC started moving due to charging effects induced by the SEM.

Figure 14: Illustration of the regions within a sample holder where SEM images were acquired, looking down onto the sample holder. The outer circle ilustrates the sample holder wall and the squares within are the regions.

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Figure 15: Example of SEM images acquired from the same region in one sample holder at the different magnifications. The magnification of each image is showed in the centre corners of the images. The red regions mark the area in which the next magnified image represents. The UOC imaged originates from the facility Key Lake in Canada.

3.2.2.2. Hyperspectral images

One hyperspectral image was acquired for each sample holder (containing unpressed UOC) with the push-broom hyperspectral camera Specim FX17e, with 224 bands in the range of 936 nm to 1720 nm. Four sub-images were picked out from each hyperspectral image for use in the analysis, Figure 16 illustrates the process. This was done in the same code as where spectra were extracted from the hyperspectral images.

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Figure 16: The process of acquiring the hyperspectral images for the analysis from the raw hyperspectral image. The columns of images show (from left to right) the raw hyperspectral image, the reflectance calibrated image, then the same image again but with a square selecting a cropped area, and the last four images are sub-images from the cropped area. These equally sized sub-images from the cropped area were used for feature extraction. The two last characters (suffix) in the image name denotes the location of the sub-image. T means top, B means bottom, L means left, and R means right. All hyperspectral images are shown with the RGB bands [20, 120, 220].