Measurements of Radiation Doses of Natural Radioactive Material in Oil fields at West Kourdofan

Abstract

Scale, sludge and sand samples were collected and analysed using thallium activated sodium iodide NaI(Tl) spectrometer to determine type, activity concentration, absorbed dose rate and annual effective dose of naturally occurring radioactive material (NORM) of samples collected from oil fields at West Kourdofan state. Scale radionuclides was found to be, 238U, 232Th and 40K at concentrations ranged from (4106.9 - 358.05) Bq/Kg, (2736.7 - 375.88) Bq/Kg and (9294 - 16.07) Bq/Kg respectively. Concentrations in sludge was ranged from (655.36 - 23.3) Bq/Kg for 238U, (396.34 - 16.19) Bq/Kg for 232Th and (353.52 - 16.07) Bq/kg for 40K. Concentrations in sand for 238U was ranged from (2807.36 - 13.89) Bq/Kg, for 232Th was ranged from (3466.24 - 14.6) Bq/Kg and for 40K ranged from (614.89 - 16.06) Bq/kg. Absorbed dose rate of scale samples ranged from (3692.01 - 398.03) nGy/h, sludge samples ranged from (542.84 - 30.49) nGy/h, sand samples ranged from (3395.25 - 23.42) nGy/h. Annual effective dose of scale samples was ranged from (4.53 - 0.49) mSv/y, sludge samples was ranged from (0.7 - 0.08) mSv/y. sand samples was ranged from (4.16 - 0.02) mSv/y. 

Contents

vii ……………………………………………………………………………. الآیـــــــــــة

Dedication……………………………………………………...…………………... vii

Acknowledgments………………………………………………………….……….vii

Abstract ……………………………………………………………………..…...…vii

 vii …………………………………………………………………………….الخلاصة

Contents ………………………………………………………………………...…..vii

List of Figures ………………………………………………………………...…....vii

List of tables …………………………………………………………………...…...vii

Chapter One ……………………………………………………………..…………1

Introduction ……………………………………………………………………...…2

1-1 Origin of petroleum ……………………………………………………..........2

1.2 History of oil in Sudan ………………………………………….……………2

1-3 A brief history of GNPOC pipeline & Production ………………….….……3

1.4 Norm definition and hazards ……………………………………....………...4

1-5 NORM & TENORM …………………………………..…….…….…...……4

1-6 Research Problem …………………………………………...…..……...……5

1-7 Objectives of the research ……………………….……………..……...…..…6

1-8 Research methodology …………………………………………….…………6

1-9 Literature Review ……………………………………………....…….………7

1-10 limitation of the research and future work ……………….……….…..….. 13

1-11 Outline of the thesis ………...……………………………..….……………13

Chapter Two ………………………………………………………………….……15

Radiation, NORM In Oil And Gas Industry And Radiation Detector…….……16

2.1 Radiation & Nuclear Structure ……………………...……………….………16

2.2 Radioactivity and radiation ……………………………...………..…………16

2.3 Radioactive decay …………………………………………...………….……17

2.4 Modes of radioactive decay ……………………………….......….…….……18

2.4.1 Alpha Particles decay ………………………………….…….…….……18

2.4.2 Negative beta particle (β–) decay ………………………...………..……20

2.4.3 Positive beta particle (β+) decay ………………………...…………...…22

2.4.4 Gamma Emission ………………………..……….….….………...…….22

2.4.5 Internal conversion ………………………...…….……....………...……23

2.4.6 Electron Capture ………………………………………….........…….….23

2.5 Interaction of Gamma radiation with matter ……………………………..…24

2.5.1 Photoelectric Absorption ………………………………………..……25

2.5.2 Compton scattering …………………………………..…..…………….25

2.5.3 Pair production ………………………………..…………….….………26

2.6 Law of Radioactive decay …………………………………....….............…..27

2.7 Growth of activity from decay of a parent ………………….………….……29

2.7.1 Transient equilibrium – t1/2 parent > t1/2 daughter ……………...……30

2.7.2 Secular equilibrium – t1/2 parent >> t1/2 daughter ……………...….…31

2.7.3 No equilibrium – t1/2 parent < t1/2 daughter ………….......…...………32

2.8 Radioactive decay series ……………...……………………….……….……32

2.9 Natural decay series …………………...………………….…………………33

2.9.1 Primordial Radionuclides ………………….………..…….……………34

2.9.2 Decay Chains …………………....………………………....…...………35

 2-10 NORM in oil and gas industry ………………………………....……..……37

2-10-1 Brief History of Norm in oil and gas fields ………….…..………...…37

2-10-2 Origin of Norm in oil and gas fields ……………....…….……………37

2-10-3 Radionuclides concentrations in oil and gas industry. …….…….……39

2-10-3-1 Norm in scale…………………………………………..…………40

2-10-3-2 Norm in sludge ………………………………………..…………41

2-10-3-3 Norm in sand ……………………………………...……..………42

2-10-4 Norm hazards and precautions …………………………………..……42

2-10-4-1 External exposure ……………………………...….………..……43

2-10-4-2 Internal exposure …………………………….……..……………44

2-10-5 Doses Limits …………………………………..………………………45

 2-11 Radiation detectors ……………………………………….…….....…..……46

2-11-1 Principle of detection …………………………..…...……..…………46

2-11-2 Detector resolution and efficiency …………………....…..….………46

2-11-3 Type of detectors ………………………………….…….……..….…46

2-11-3-1 Gas-Filled Detectors …………………….…….…………....……47

2-11-3-2 Semiconductor Detectors …………………...….…………...……47

2-11-3-3 Scintillation detectors …………………………….………...……48

2.11.3.3.1 Basic Principles.……………………………....………...……48

2.11.3.3.2 Photomultiplier Tubes (PMT) ………………….……....……49

2.11.4 Efficiency and resolution of HPGe and NaI (Tl) detectors ……..……51

ChapterThree…….………..…………………………………….….…...…………52

Samples Preparation and Experimental Method………………………...…....…52

3-1 fields trips ……………………………………………………....….……...…53

3-2 Sampling and sample preparations ……………….……………....…….……54

3-3 Experimental method ………………………………………...….…………..55

 3-3-1 Marinelli beaker …………………………………………….…………..55

 3-3-2 calibration process …………...…………………………....……………56

3-3-2-1 Energy calibration……….……………………..…..…....…………56

3-3-2-1 Efficiency calibration ……………..……..……………...…………57

 3-4 Sample measurements …………………………..…………………………….58

 3-5 Calculations ……………………………………...……….…………...………60

 3-5-1 Activity concentration ……………………………….…….…………….60

 3-5-2 Absorbed dose …………………………….…….……………………….60

 3-5-3 Anuual effective dose ………………………………….……………..….61

Chapter Four ……………………………………..……….……..………..……….. 62

Result and discussion ……………………………………..…….…….…………….63

4-1 Result ……………………………….……………..………………………….63

4-2 discussion …………………………….…………..…………………………...71

4-3 Conclusion …………………………………….…….….………………….…72

References ………………………………………….………...………………...…...73

Appendix I ………………………………………….…………..……………...……77

Appendix II ……………………………………………….….…....………...………81

Appendix III ……………………………………………………....……...…………82

Appendix IV…………………………………………………….…...………………83