Assessment Of Soil Radionuclide Level In Ilorin, Kwara State

Description

ABSTRACT

A study of soil radionuclide from Ilorin, Nigeria, has been carried out and it was analyzed by g-ray spectroscopy to determine the ²²⁶Ra and ²²⁸Ra concentrations. The activity concentration values range from 0.81 ± 0.08 to 7.4 ± 2.2 Bq/l for ²²⁶Ra and from 1.8 ± 0.3 to 5.6 ± 2.6 Bq/l for ²²⁸Ra. The derived Annual Effective Dose received by the population as a result of the ingestion of ²²⁶Ra was estimated to range from 0.08 ± 0.01 to 0.12 ± 0.07 mSv/y with an average of 0.39 ± 0.11 mSv/y and ²²⁸Ra range from 0.50 ± 0.32 to 1.42 ± 0.70 mSv/y with an average of 0.91 ± 0.31 mSv/y. Consequently, the Annual Effective Dose received, as a result of the combined ingestion of ²²⁶Ra and ²²⁸Ra, was found to range from 0.81 to 1.74 mSv/y with an average of 1.30 mSv/y. Therefore, this work is aimed at estimating the lung cancer risk of indoor radon exposure in residential basements.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

INTRODUCTION

1.1     Background of the Project

1.2       Sources of Radon

• Concentration units

1.4       Properties of Radon

1.4.1    Physical properties of Radon

1.4.2    Chemical properties of radon

1.5       OCCURRENCE OF RADON

1.5.1    Radon in groundwater

1.5.2    Radon in rainwater

1.5.3    Radon in the oil and gas industries

1.5.4    Radon in mines and caves

1.5.5    Radon in houses

1.6       Aim and Objectives

CHAPTER TWO – LITERATURE REVIEW

2.1     Overview of Radon

2.2     Risk of Radon

2.2.1 Geographic and Residential Risk

2.2.2 Risk for Smokers

2.2.3 Risk for Women and Men

2.2.4 Risk for Children and Elderly

2.3 Harmful Effects of Radon

2.4 Radon Measurement

References

CHAPTER THREE –

RESEARCH METHODOLOGY

3.1     study area

3.2     samples collection and treatment

3.3     radioactivity computation

CHAPTER FOUR

4.1     Discussion

CHAPTER FIVE

5.1     Conclusion

References

CHAPTER ONE

1.0                                        INTRODUCTION

1.1 BACKGROUND OF THE STUDY

Radon is a naturally occurring radioactive gas, formed as the decay product of radium-226 (half-life 1600 years), which is a member of the uranium-238 decay chain. Uranium and radium occur naturally in soil and rocks and provide a continuous source of radon. Radon-222 which is the most stable isotope of radon has a half lifeof 3.8 days. It is considered health hazard because of its radioactivity. Radon gas emanates from the earth’s crust and as a consequence is present in the air, outdoors and in all buildings, including workplaces. Radon generally disperses into the atmosphere, resulting in generally low level of radon immediately above the ground. Buildings that are poorly ventilated and have cracks in their foundations or floor drains are susceptible to high radon levels which may gradually build up to hazardous levels.

Radon is formed as one intermediate step in the normal radioactive decay chains, through which thorium and uranium slowly decay into lead. Thorium and uranium are the two most common radioactive elements on earth; they have been around since the earth was formed. Their naturally occurring isotopes have very long half-lives, on the order of billions of years. Thorium and uranium, their decay product radium, and its decay product radon, will therefore continue to occur for tens of millions of years at almost the same concentrations as they do now. As radon itself decays, it produces new radioactive elements called radon progenies or decay products. Unlike the gaseous radon itself, radon daughters are solids and stick to surfaces, such as dust particles in the air. If such contaminated dust is inhaled, these particles can stick to the airways of the lung and increase the risk of developing lung cancer.

Radon is responsible for the majority of the public exposure to ionizing radiation. It is often the single largest contributor to an individual’s background radiation dose, and is the most variable from location to location.(ICRP, 1993). Despite its short lifetime, some radon gas from natural sources can accumulate to far higher than normal concentrations in buildings, especially in confined areas such as attics and basements. It can also be found in some spring waters and hot springs.

1.2 SOURCES OF RADON

Radon is produced by the radioactive decay of radium which is a member of the naturally occurring Uranium decay series. The most abundant isotope ²²²Rn is a descendant of ²³⁸U while ²²⁰Rn (Thoron) and ²¹⁹Rn (Actinon) are the descendants of ²³²Th and ²³⁵U respectively. As radon itself decays, it produces new radioactive elements called radon daughters or decay products. There are around seventeen known isotopes of radon. The decay series leading to the three abundant isotopes of radon is shown in Fig. 1.1