ABSTRACT
The k0 – of the following (Ca-49, Ba-131, Cd-115, In-116m, Cd-116m2, Co-60, Cs-134, Ir-192, Hg-197, Se-75, Gd-153, Gd-159, Pd-109, Ag-110m, Tm-170, Re-186, Sm-153, S-36, U-239) suspected to have discrepant k0 –values were determined using Certified Reference , (SMELS I, III and NIST 1633b Coal fly Ash).
The 1.10E-4 for 49Ca at 3084keV, 1.95E-5, 3.43E-6, 6.45E-5 for 131Ba at the of 373, 486, and 496keV 4.70E-4 for 115Cd at 528keV; 1.66E-1 for 153Sm at 103keV; 6.88E-3, 1.38E-3 for 75Se at 136 and 401.73keV respectively;
7.27E-1, 1.54E+0, 2.28E+0 for 116mIn at 418.9, 1097 and 1293keV respectively; 4.00E-2, 7.32E2, 4.67E-1, 3.93E-2 for 134Cs at 562, 569, 602 and 802keV respectively were gotten.
The student t-test which is the statistical analysis was used to compare the result of this work with the recommended data. The result of the comparison at 5% confidences intervals showed no significance difference which reveals the accuracy of the k0- standardisation adopted in Nigeria Research Reactor -1 (NIRR-1).
TABLE OF CONTENT
Contents ………………………………………………………………Page
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
Abbreviations………………………………………………………….. xii
CHAPTER ONE: INTRODUCTION
1.0 Introduction………………………………………………………. 2
1.1 Research Problem…………………………………………………. 3
1.2 Justification of Study……………………………………………… 4
1.3 Objectives of this study……………………………………………. 6
1.4 Previous Work …………………………………………………….. 6
CHAPTER TWO : LITERATURE REVIEW
2.1 Neutron Sources………………………………………………. 9
2.1.1 Neutron Generators…………………………………………… 9
2.1.2 Isotopic Neutron Sources………………………………………9
2.1.3 Nuclear Reactors……………………………………………… 10
2.2 Description of NIRR-1……………………………………….. 10
2.2.1. Reactor Complex…………………………………………….. 13
2.2.2. Control System and Control console………………………… 13
2.2.3. Auxiliary System of NIRR-I ……………………………….. 13
2.2.4. Irradiation System…………………………………………… 14
2.3 General Principle of Neutron Activation Analysis (NAA)….. 14
2.3.1 NAA Procedure………………………………………………. 16
2.3.2 Forms of NAA………………………………………………… 16
2.4 Absolute method of NAA …………………………………… 17
2.5 The Relative method of NAA…………………………………. 18
2.6 ko Standardization method ……………………………………. 19
2.6.1 Full-Energy peak detection efficiency (ε p)……………………25
2.6.1 A. The fixed sample-detector geometry ……………………… 26
2.6.2.B. The variable sample-detector geometry …………………… 27
2.6.3. Ratio of resonance integral to thermal cross-section(Qo)……27
2.6.4. Neutron Spectrum Parameters ƒ and α…………………….. 27
2.7 Uncertainty in RNAA…………………………… 30
CHAPTER THREE: MATERIALS AND METHOD
3.1 Sample preparation…………………………………………… 32
3.2 Irradiation of samples ………………………………………… 33
3.3 Gamma- ray spectrometry measurement………………………33
3.3.1. Counting of Irradiated Samples……………………………. 34
3.3.3. Full energy peak efficiency calibration ( )……………….. 34
3.3.4 Calculations………………………………………………… 35
CHAPTER FOUR: RESULT AND DISCUSSION
4.1 Efficiency calibration…………………………………………. 37
4.2 Calculation of k0-values……………………………………….. 42
4.3 Measured k0-values…………………………………………… 42
CHAPTER FIVE: CONCLUSION AND RECOMMENDATION
5.1 Conclusion …………………………………………………… 52
5.2 Recommendation …………………………………………….. 53
REFERENCES …………………………………………… 54
INTRODUCTION
The interest in the role of trace, minor, and major elements in biology, environmental research, geology, and technology (to ensure safety) for the socio-economic development of several countries has led to an increasing need for multi element analysis on a large number of samples.
Various standardization methods have been used in neutron activation analysis (NAA), namely: Absolute, Relative or Single comparator.
In the absolute standardization, the physical parameters characterizing an element were determined by independent methods, their imprecision’ would add up when calculating the amounts of elements (Dung and Hien; 2003) leading to large systematic errors.
In the relative standardization, the unknown sample is irradiated together with a standard or reference material containing a known amount of the element of interest.
The standard reference material is measured under the same counting condition as the sample. This standardization method is still being regarded as one of the methods which has the highest accuracy of NAA (Dung and Hien; 2003).
However, it is not suited for multi-element analysis with regards to the experimental workload and the impossibility to quantify unexpected elements.
The single comparator standardization makes multi-element analysis with NAA feasible via the k0-factors, which are experimentally determined by co-irradiation of a standard and a single comparator.
The k0-standardization method of NAA (k0-NAA) launched in the mid 1970s (Simonits et al; 1975) is able to overcome the above-mentioned disadvantages.
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