ABSTRACT

Nigeria has for a very long time engaged in the peaceful application of nuclear technology. The use of ionizing radiation due to its unique properties has considerably increased over the years in oil and gas industry. In this study, the radiation safety procedures have been evaluated and whole-body occupational exposure for workers in some selected industrial radiography and well-logging facilities were assessed using thermoluminescent dosimeters (TLDs) for a 10y period. The TLDs were read using Harshaw dual-4500 TLD reader on quarterly basis. During the 10y study period, the average annual effective doses were found to be 1.3 mSv and 0.96 mSv for the industrial radiography and well-logging practices respectively. The annual collective dose received by the exposed workers in industrial radiography and well-logging practices were found to be between the ranges 27.8-99.6 man mSv and 12.1-32.2 man mSv respectively, while the two practices contribute 768 man mSv to the total world collective dose value. On the TLD return rates, well-logging practice records the highest with 95.7% while industrial radiography practice scored 90.1%. The overall result showed that 89% of the workers received doses lower than 1 mSv and there was no instance where a worker received dose greater than the dose limits prescribed by Nigerian Nuclear Regulatory Authority (NNRA). The average annual effective doses obtained from this study were compared and discussed with the results obtained from other countries and UNSCEAR. Although, the radiation workers covered by this study received doses less than the dose limits set by the NNRA, licensees and all stakeholders involved should make sure that, the radiation workers are regularly and properly trained on operational procedures and radiation protection matters, so that the doses to the individual and the working environment are kept as low as reasonably achievable (ALARA).

xviii

CHAPTER ONE

INTRODUCTION

1.1      Background to the Study

Nigeria has, for a very longtime, engaged in the peaceful application of nuclear technology.

The use of ionizing radiation, because of its unique properties, has considerably increased

over the years in oil and gas industry.

Due to the adverse health effect when people are over-exposed to ionizing radiation,

radiation is feared by many, worldwide, and Nigerians are no exception. This concern is

even much higher with inhabitants living at close proximity to nuclear establishments and

other facilities using ionizing radiation sources. What most people do not realize is that

radiation is present everywhere, in everything in the environment and even in the bodies

(Oyeyinka et al, 2012). There is cosmic radiation made up of protons, alpha particles and

heavy nuclei bombarding the earth from space which, upon interaction with the atmosphere

results into large assortment of secondary particles, including pie (π) and mu (µ) mesons,

electromagnetic photons, neutrons, protons and electrons contributing high radiation dose

burden to man even at sea level (Maduemezia et al, 2008). Other natural radiation includes

the terrestrial gamma rays from land, sea and walls of houses we live. Humans are also

internally exposed from radiation emitted by radionuclides absorbed into the body through

the consumed food (Oyeyinka et al, 2012). Examples of such radionuclides are potassium-

40, heavy elements and carbon-14. Therefore, living isolated from radiation is almost

impossible in the modern world as humans and animals are subjected to both natural and

artificial radiation in the environment, due to increase in living standard (Zakari et al,

2009). There is no need for fear of radiation but there is the need to understand its

properties, make use of it and reduce the exposure to dose levels which the society judged

1

as acceptable, with minimum associated risk. As long as the contribution from the artificial

radionuclides does not push the annual dose equivalent level beyond 1mSv for the public

and 20mSv averaged over five years for classified workers, then there is no need to fear

radiation (NNRA, 2003).

Oil and gas industry utilize many radiation sources in various applied radiation-based

technologies (Abu-Jarad, 2008). Those technologies provide significant benefit to society

through the daily operations of the industry. Gamma radiation sources such as Caesium-137

(137Cs) and Cobalt-60 (60Co) and neutron source like Americium-241/Beryllium (241Am-

Be) are extensively used in well logging operation while Barium-133 (133Ba), 241Am and

137Cs sources are used in multiphase flow meters technology at platform of oil and gas

production facilities (Abu-Jarad et al, 2007; Abu-Jarad, 2008). Transmission level gauges

for tanks in refineries use gamma radiation sources such as 137Cs and 241Am while X-ray

fluorescence (XRF) techniques are used for sulfur gauges in laboratories. Refineries

employ Cadimium-109 (109Cd) and Iron-59 (59Fe) in alloy and Sulfur analysis. Neutron

sources such as Californium-252 (252Cf) and 241Am-Be are used in operating nuclear

density gauges in Oil and Gas Industry. Iridium-192, 1