Assessment of Characteristics of Thermoluminescence Dosimetry (Tld) System Used In Centre For Energy Research And Training (Cert), Ahmadu Bello University, Zaria
Assessment of Characteristics of Thermoluminescence Dosimetry (Tld) System Used In Centre For Energy Research And Training (Cert), Ahmadu Bello University, Zaria.
ABSTRACT
Thermoluminescence dosimetry (TLD) system has been used to estimate the personal dose for external occupationally exposed workers in CERT.
The reliability and precision of dose measurements and the accuracy of dose evaluation are important factors for the improvement and achievement of individual monitoring objectives.
In this piece of work, evaluation of characteristics of TLD system was investigated at the Centre for Energy Research and Training, Ahmadu Bello University Zaria.
Dose sensitivity, dose linearity, residual signal, fading, batch homogeneity, stability of Calibration factor, re-usability over 10 cycles, sensitivity to ambient light, and the influence of environmental conditions were evaluated.
TABLE OF CONTENTS
Title page……………………………………………………………. i
Declaration………………………………………………………….. ii
Certification…………………………………………………………. iii
Dedication…………………………………………………………… iv
Acknowledgement…………………………………………………… v
Abstract………………………………………………………………. vi
Table of contents……………………………………………………… vii
List of tables………………………………………………………….. x
List of figures…………………………………………………………. xi
CHAPTER ONE
INTRODUCTION
1.1 Thermoluminescence detectors in dosimetry………………….. 1
1.2 Statement of research problem…………………………………. 3
1.3 Aim and objectives………………………………………………. 5
1.4 Justification………………………………………………………. 5
CHAPTER TWO
LITERATURE REVIEW
2.1 Thermoluminescence (TL)……………………………………… 7
2.2 Role of lattice imperfection in luminescence……………………. 8
2.3 Principles of thermoluminescence……………………………….. 9
2.4 Thermoluminescent dosimetric (TLD) system………………….. 14
2.4.1 TL detectors……………………………………………………… 14
2.4.2 TL reader………………………………………………………… 16
2.4.3 TL measurement cycle…………………………………………… 17
2.4.4 Mathematical evaluation of dose………………………………… 20
2.5 The main characteristics of the TLD system…………………….. 21
2.5.1 Batch homogeneity………………………………………………. 21
2.5.2 Dose linearity…………………………………………………….. 22
2.5.3 Energy response………………………………………………….. 23
2.5.4 Reproducibility…………………………………………………… 25
2.5.5 Dose sensitivity…………………………………………………… 26
2.5.6 Residual signal…………………………………………………… 27
2.5.7 Fading……………………………………………………………. 28
2.5.8 Sensitivity to ambient light………………………………………. 30
2.5.9 Sensitivity to other environmental conditions……………………. 31
CHAPTER THREE
EXPERIMENTAL MEASUREMENT
3.10 Introduction……………………………………………………… 33
3.20 Materials…………………………………………………………. 33
3.2.1 Four detector cards……………………………………………….. 33
3.2.2 TLD reader………………………………………………………. 34
3.2.3 Irradiation facility……………………………………………….. 34
3.30 Methods………………………………………………………….. 36
3.3.1 Batch homogeneity………………………………………………. 36
3.3.2 Reproducibility test……………………………………………… 36
3.3.3 Sensitivity factor (individual correction factor)………………….. 37
3.3.4 Calibration factor………………………………………………… 38
3.3.5 Stability of calibration factor…………………………………….. 38
3.3.6 Dose linearity……………………………………………………. 39
3.3.7 Residual signal…………………………………………………… 39
3.3.8 Sensitivity to ambient light………………………………………. 40
3.3.9 Sensitivity to other environmental conditions……………………. 40
3.3.10 Thermal fading…………………………………………………… 40
CHAPTER FOUR
RESULTS AND DISCUSSION
4.1 Batch homogeneity………………………………………………. 42
4.2 Reproducibility test………………………………………………. 44
4.3 Dose sensitivity (individual correction factor)…………………… 45
4.4 Calibration factor and stability of calibration factor…………….. 47
4.5 Dose linearity…………………………………………………… 48
4.6 Effect of residual signal………………………………………… 49
4.7 Effect of ambient light…………………………………………… 52
4.8 Sensitivity to other environmental conditions…………………… 52
4.9 Time effect of fading……………………………………………… 53
CHAPTER FIVE
SUMMARY, CONCLUSIONS AND RECOMMENDATIONS
5.1 Summary of characteristics of TLD system used in CERT……… 55
5.2 Conclusion……………………………………………………….. 58
5.3 Constraint…………………………………………………………. 58
5.4 Recommendation………………………………………………… 58
References…………………………………………………………… 60
REFERENCES
Bilski, P. and Budzanowski, M. (2005). Dosimetric properties of TLD European Cards with high sensitive MCP-7.
Daniels, F., Boyd, C.A. and Saunders, D.F. (1953). Thermoluminescence as a Research Tool, Journal of Science, 117: 343-349.
Danilkin, M., Kerikmäe, M., Kirillov, A., Lust, A., Ratas, A., Paama, L. and Seeman, V. (2006). Thermoluminescent dosimeter: Li2B4O7:Mn,Si – a false-dose problem. Proc. Estonian Acad. Sci. Chem., 55(3): 123–131
Duggan, L., Budzanowski, M., Przegietka, K., Reitsema, N., Wong, J. and Kron, T. (2000). The light sensitivity of Thermoluminescent materials:LiF:Mg,Cu,P, LiF:Mg,Ti and Al2O3:C. Radiation. Measurement, 32: 335-342
El-Faramawy, N. A., El-Kameesy, S. U., El-Agramy, A. and Metwally, G. (2000). The Dosimetric Properties of In-House Prepared Copper Doped Lithium Borate Examined Using the TL-Technique. Radiat. Phys. Chem. 58: 9-13
Furetta, C. and Weng, P.S. (1998). Operational Thermoluminescence Dosimetry, World Scientific Publishing, Singapore. pp. 1-247
