Nuclear and Radiation

The level of implementation of quality control program (QCP) in diagnostic radiology facilities in Akwa Ibom state, Nigeria, was investigated. A total of thirty (30) diagnostic radiology centres took part in the study. A two part structured self completion questionnaire of thirty six items was the instrument used for data collection. Result shows that the level of implementation of quality control programme (QCP) in these diagnostic radiology facilities was low, importance of QC to the facility and radiation safety notwithstanding. This low level of implementation of QCP was identified with some fundamental factors namely, lack of radiation safety officers (RSO), lack of retraining programme for the medical personnel, lack of adequate funding, power and QC test equipment for the facilities. The aim of this investigation is to study the level of implementation of quality control programme which enhances radiation protection in diagnostic radiology facilities.

The dependency of neutron self-shielding factor on neutron field and sample size in large sample neutron activation analysis was experimentally assessed for powdered leaves samples up to 5 g in mass. The measurements of the neutron flux depression inside the samples were used in determining the neutron self-shielding factor. The experimental results agreed with the theoretical estimation that neutron self-shielding factor is dependent on neutron flux level and sample size. Neutron self-shielding was found to increase with decreasing neutron flux level and increasing sample size and vice versa.

In this article, we have discussed the effect of changes in acceleration of gravity on the amount of human awareness. The concentration of research is on the outcomes of the brain which effectuates the loss of consciousness when the acceleration of gravity is changed (G-LOC). G-LOC, pronounced 'GEE-lock', is the abbreviation of G-force induced Loss Of Consciousness, a term generally used in aerospace physiology to describe a loss of consciousness occurring from excessive and sustained g-forces draining blood away from the brain causing cerebral hypoxia. The condition is most likely to affect pilots of high performance fighter and aerobatic aircraft or astronauts but is possible on some extreme amusement park rides. G-LOC incidents have caused fatal accidents in high performance aircraft capable of sustaining high g for extended periods. High-G training for pilots of high performance aircraft or spacecraft often includes ground training for G-LOC in special centrifuges, with some profiles exposing pilots to 9 gs for a sustained period. Experiments carried out on people all in good condition, revealed that they underwent different sofferings, both physically and mentally, when exposed to accelerated movements.

Efforts to minimize dose delivered to critical organs of cancer patients and also to improve local tumour control have led to the development of High Dose Rate (HDR) brachytherapy procedures. The associated risks in HDR brachytherapy are relatively high, hence strict quality assurance requirements are needed. In this study, mathematical model has been used to compute the dose rate distributions around an Ir-192 HDR brachytherapy source. The calculations were based on separation of dose rates around the sources into transverse axis component and an anisotropy function. The two dimensional coordinate system for anisotropy functions was then transformed into a one dimensional system with radial distances from the centre of the source as constraints. The maximum average fit uncertainty was found to be 0.35% for the anisotropy functions. The maximum uncertainty in the calculated dose rate distribution around the source was 14.31%, which is less than the uncertainty quoted in published reports for other methods. The model is therefore an improvement over existing recommended systems for dose calculations and the results can be used as quality control tool to improve dose delivery to cancer patients undergoing brachytherapy.

In this work, the natural radionuclide contents of some building materials widely used in Nigeria were measured by the means of gamma-ray spectrometry using Na(I)Tl detector. A total of 15 samples were assayed from different materials. The mean of 226Ra, 232Th and 40K concentrations determined are 30.35±8.69BqKg-1, 20.12±6.00 BqKg-1 and 241.95±76.31 BqKg-1 respectively. These values were lower than permissible global values except for potassium which is higher than that of global permissible value of 52.2, 41.0 and 230.0 (BqKg-1 ) respectively by UNSCEAR. The obtained mean absorbed dose rate for all the collected building materials samples is 39.90(nGgh-1). These results, along with the results of the estimated annual effective dose rates, radium equivalent (Raeq), external hazard index (Hex) are presented and they are found below the internationally accepted safe limits. It suffices to say therefore the analyzed samples could be used for building and construction purposes. It is safe to say that there is no threat pose to any users of the materials.

Absorbed dose rate and annual effective dose estimated for occupational workers for Goldmines in Ghana that uses nuclear gauges in their operations and external ionizing radiation exposure during cargo radiographic inspections were measured as part of the authorization process for the use of ionizing radiations sources in Ghana. The measurements reported in this paper were made with portable radiation monitor which employed GM tube and was calibrated against secondary standard dosimetry system and a data for a five-year period (2010-2014) was compiled from the RAIS of the Ghana Radiation Protection Board. The average absorbed dose rate in air for Goldmine workers was 0.73µSv/h with an annual effective dose of 1.45 mSv while the average external radiation dose for workers and members of the public during cargo inspection was 0.23 µSv/h for Cobalt 60 scanners and 0.1 µSv/h for x-ray scanners and the annual effective dose for both workers and members of the public for Cobalt-60 and X-ray scanners were 0.46mSv and 0.2mSv respectively. It was concluded that the prevalent radiation levels did not pose any significant radiological health hazard to workers and members of the public.

In this work had be determine the ratio of the drift velocity to the diffusion coefficient W/D to calculate the motion of free electrons in air and helium gas. The following parameters of the electronic motion were determined as a function of the electric field strength E, apparent energy factor, K1 and Townsend energy factor, KT for Helium gas and air at 300?K and 288?K respectively in case of Maxwell and Druyvesteyn distribution law. The transport equation solved numerically to obtain the transport coefficients values and had be fed to the equations to calculate the above parameters. The gas parameters are obtained and compared with available experimental data.

Void fraction measurements are made by the gamma radiation method in crude oil-water two phase flow. To measure the void fraction, the required gamma-ray source and the strength of the source is experimentally found for oil-water two phase flow using Cs137.This is achieved by the empty small plastic tubes were used for simulating the void fraction through the mixture. The obtained results show that, the void fraction value increase with the source count rate by the NaI (Tl) counter.

An estimation of volumetric efficiency in large sample neutron activation analysis through the application of an empirical expression for the full energy peak efficiency was done. The gamma-ray self-attenuation correction factor and the geometric correction factor based on which the volumetric efficiency is finally estimated were experimentally and theoretically determined respectively. Within the limits of mass range of the sample investigated, there was no significant difference between the photo-peak efficiency and the volumetric efficiency. The result of the study therefore establishes that the mass (volume) of the test portions does not have significant effect on the efficiency of elemental detection when geometrical correction is considered.

As part of the nuclear power project envisaged during the period of the first republic, attempts have been made to prospect for uranium as raw material for the nuclear reactor. The Biakpa area in the Volta region had been known by the indigenes to be a potential source of this raw material. A field survey had been carried out using a Fieldspec radiation survey meter and the uranium content of some rock samples taken from the area has been determined. The uranium content determined by comparison with an IAEA uranium standard S-13 lot 370 using the track etch technique gave a mean value of 0.018%. The dose rate obtained during the survey ranged from 1.22 - 2.25 µSv/h.