Determination of the natural radioactivity, elemental composition and geological provenance of sands from Douala in the littoral region of Cameroon using X-ray and γ-ray spectrometry

peer reviewedThis study aimed to determine the concentration of natural radionuclides, the chemical composition, and the geological provenance of sand samples from seven large quarries within the Douala Basin and surrounding locations within the Littoral Region of Cameroon along the Gulf of Guinea. The analyses were undertaken on a total of 24 samples, using both gamma- and X-ray spectrometry techniques. Gamma spectrometric results indicated that the samples from the study area contained amounts of natural radioactivity that are less than the globally agreed safe limits. X-ray fluorescence spectrometry yielded quantitative major, minor, and trace element concentrations that were used in tectonic discrimination diagrams, indicating that these sediments were deposited in a passive margin environment. These concentration and natural radionuclide radioactivity level data provide a reference database for this region of Cameroon as well as for the wider Gulf of Guinea

Counting time measurement and statistics in gamma spectrometry: the balance

Nuclear counting statistics at high count rate are assessed on a γ-ray spectrometer set-up. Our typical gamma spectrometry system consists of a High Purity Germanium (HPGe) detector, liquid nitrogen cooling system, preamplifier, detector bias supply, linear amplifier, analog-to-digital converter (ADC), multichannel storage of the spectrum, and data readout devices. Although the system is powerful enough for background measurements, it is important, nowadays, to have a great statistical in short time measurement: which is a challenge for scientists. The purpose of this study was to determine the average time for gamma spectrometry measurement. To detect Uranium, Thorium and their respective daughters and Potassium series with a relative related error less than 1%, it was found that it is necessary to count during a minimum of 24 Hours (86,400 s). This result is in accordance to the literature with planar geometry detector. These results conduct us to make the following three guidelines for selecting the detector best suited for an application: 1. The more detector material available (germanium semi-conductor), the higher the full-energy peak efficiency. 2. The smaller the distance between the detector and the source material, the higher the full- energy peak efficiency. 3. While better resolution gives a better MDA, the resolution contributes only as the square root to the MDA value, whereas the MDA is proportional to the full-energy peak efficiency. This idea came to us by comparing the spectra of measuring radioactivity lasts for 12 hours in the day that does not fully covered the night spectra for the same sample. The conclusion after several investigations became clearer: to remove all effects of radiation from outside (earth, sun and universe) our system, it is necessary to measure the background for 24, 48 or 72 hours. In the same way, the samples have to be measures for 24, 48 or 72 hours to be safe to be purified the measurement (equality of day and night measurement). It is also possible to not use the background of the winter in summer. Depend to the energy of radionuclide we seek, it is clear that the most important steps of a gamma spectrometry measurement are the preparation of the sample and the calibration of the detector

Origins of 137Cs and 133Xe in Soils from two Campuses in University of Douala-Cameroon

This paper presents an evaluation of 238U, 235U, 137Cs and 133Xe in soils from two campuses in university of Douala-Cameroon using gamma spectroscopy based Broad Energy Germanium Detector (BEGe6530). The mean activity of 238U, 235U, 137Cs and 133Xe in soils from two campuses in university of Douala-Cameroon were 40.16±8.98, 3.39±0.33, 0.46±0.33 and 0.14±0.16 Bq/kg for Campus 1; and 31.45±12.24, 3.02±1.00, 0.30±0.26 and 0.35±0.24 Bq/kg for Campus 2, respectively. In terms of health scrutiny, the absorbed dose rate in air at 1.0m above the ground was measured using an In situ survey meter and the annual effective dose was calculated. The mean values of the absorbed dose rate were 71.43 nGy/hr and 62.72 nGy/hr for Campus 1 and 2, respectively. The estimated average of the outdoor effective dose for Campus 1 and 2 were 87.60 μSv/y and 76.93 μSv/y, respectively. The results obtained in both sites were found to be relatively high than the save limit of 70 μSv/y by UNSCEAR. The observed traces of 137Cs and 133Xe in the studied samples call for future investigation to seek for the origin of these radionucleides. The National Radiation Protection Agency (NRPA) within the activities planned in the Cameroon INSSP: “Establish and maintain national capability to provide technical support to front line detection capabilities and to categorize and characterize suspected radioactive material” will carry out investigations, considering that the radioactivity from the fallout nuclear tests since 1986 in the Sahara reached as far as West Africa (Nigeria) and the Central African Republic to the south. More than 210 nuclear tests were carried out in North Africa between 1960 and 1996. However, no research has been carried out in Cameroon in this domain after the Chernobyl catastrophe in 1886 and the Fukushima accident in 2011

Natural radioactivity and elemental composition of sands in the Douala region, Littoral of Cameroon Using Portable XRF and HPGe detector

Twenty four sand samples from seven sand quarries alone the Gulf of Guinea, Douala Littoral region of Cameroon, were analyzed using high purity germanium detector and a portable X-ray fluorescence (PXRF) spectrometer. A comprehensive study was conducted to determine the natural radioactivity concentrations and the geological provenience of sand samples from seven different quarries sites of the Douala, a popular city, and its surroundings. The radioactivity investigation was performed by using high resolution gamma-ray spectrometry. From the measured gamma-spectra, the average activity concentrations were determined for 226Ra, 232Th, 40K and 235U for a depth of 5–25 cm. Results of this study were compared to values from other locations around the world. X-ray fluorescence spectrometry (XRF) measurements were performed for the quantitative elemental analysis of the sands, revealing the major, minor and trace elements present in the investigated samples. Reference marine and geological sample are used to check precision and accuracy of the equipment for major and minor components. From XRF experimental results it was possible to estimate the geological provenience of the analyzed sands. These data record the radioactivity background levels in sands and could be used as reference information in Cameroon. The comparison of major (Si, Al), minor (K, Ca,Fe), and trace (Ti, Mn, Zr, Rb, Sr) element ratios was made. The results indicate that the levels of Si and Al can be very helpful in subgroup definition and provide useful clues to the raw materials used for glassmaking in Cameroon

Gamma-Ray Spectrometry: Experimental Measurement and Monte Carlo Simulation using GEANT4 toolkit

Nowadays the precision in the measurement has become a challenge for physicists. That is why in recent decades, the interest is very granted to simulation. Since 1940, the method Monte Carlo is more useful for validation and even for prediction of the results of the experiment. The aim of this study is to validate experimental models. Our laboratories are equipped with HPGe gamma spectrometers for measuring the natural radioactivity, it becomes interesting to compare and even to improve the performance of our system. Geant4 is used for the construction of the geometry of detection, the physics processes and the primary particles. First and prliminary result was prsented in this paper.HPGe_GEANT

Gamma Emitting Radionuclides in Soils from Selected Areas in Douala-Bassa Zone, Littoral Region of Cameroon

peer reviewedA study of natural radioactivity levels in some composites of eighteen soil samples selected within Douala-Bassa zone of Littoral Region has been evaluated. The samples were analysed using gamma spectrometry based broad energy germanium detector (BEGe 6350). The activity profile of radionuclide shows low activity across the studied areas. The obtained mean values of 226Ra, 232Th, and 40K in the two campuses were 25.48 Bq/kg, 65.96 Bq/kg, and 39.14 Bq/kg for Campus 1 and 24.50 Bq/kg, 66.71 Bq/kg, and 28.19 Bq/kg for Campus 2, respectively. In terms of health analysis, some radiation health hazard parameters were calculated within the two campuses. The mean values of radium equivalent activity were 122.81 Bq/kg and 122.08 Bq/kg, absorbed dose rate in air was 99.13 nGy/h and 98.18 nGy/y, annual outdoor effective dose was 0.12 mSv/y and 0.12 mSv/y, and external health hazard index was 0.34 and 0.33 in Campus 1 and Campus 2, respectively. These health hazard parameters were seen to be below the safe limit of UNSCEAR 2000 except the absorbed dose rate in air and the annual outdoor effective doses which are relatively high compared to the values of 60 nGy/h and 0.07 mSv/y. These results reveal no significant radiological health hazards for inhabitance within the study areas

Investigation of the Suspected Radioactive Contaminated Container at the Kribi Deep Seaport - Cameroon

peer reviewedGiven the potential growth of the illicit trafficking of radioactive material in the world, Cameroonian seaports inspect a large number of goods entering and exiting national borders. The Kribi deep seaport (in the South Region of Cameroon) is moving toward inspection of all containers crossing the sea borders of Cameroon. These inspection's objective was to identify the most important research initiatives and the major policy issues that need to be addressed in order to improve the security of imports and export using shipping containers, particularly against the unauthorized importation and exportation of nuclear and radioactive materials, and contaminated foodstuffs. Following the request of the Commander of Kribi deep seaport for the potential presence of the radioactivity in an export container, a fact-finding mission was organized by the National Radiation Protection Agency (NRPA) of Cameroon. The process was triggered following two alarms obtained during two consecutive passages of the concerned container to the Radiation Portal Monitor (RPM) whose orders are held by TransAtlantic S.A. A team of experts from NRPA conducted a safety assessment mission around the said container. The approach involves container isolation, dose rate measurement around the container (horizontal and vertical measurement by scanning), remote process approach (for reduction of the received dose), determination of the hottest points, identification of the source, opening of the container, sampling and laboratory analysis if necessary. The investigation began at the Radiation Portal Monitor command office and continued to the container by raising the dose values at several points of the container. Two situations were then observed when reading the measured data. Firstly, it was noted a distribution of dose rates with average values ranged between 0.06 and 0.14 μSv/h for the upper parts of the suspected container, and secondly an area consisting essentially of the base of the container where the dose rates ranged from 0.10 to 0.24 μSv/h. This last value, although lower than the public dose rate limit (0.5 μSv/h), is higher than the action level, which is three times the natural background. This finding motivated further investigations allowing the following conclusion: The material transported in the container FCIU3774607 subjected to the investigations was not radioactive. The radiation that triggered the alarm came mainly from sludge covering the base of the container. It should be noted that the planned nuclear security measures for the scanning of exports through a coupled system of the Sentry Portal Scanner and the Radiation Portal Monitor allow Kribi seaport to guarantee the export of uncontaminated foodstuffs. This work identified a sample technical approach that is feasible technically and operationally and involves components already in the early deployment stage by the NRPA. A protocol of similar incidents in the future was written and documented in view of improving nuclear security at seaports in Cameroon. As for Kribi deep seaport perspectives will be a question of making arrangements for setting up a mechanism to manage the illicit traffic of radioactive sources and other nuclear material detected during scanning operations and put in place a mechanism for managing food and other consumer products with radioactive contamination, in partnership with the NRPA

Radiological Hazards in Soil from the Bauxite Deposits Sites in Dschang Region of Cameroon

peer reviewedThis work evaluates the radiological health risk from NORM exposure in bauxite deposition sites of West Region in Cameroon. In-situ and laboratory measurements were performed using dose rate survey meter and Broad Energy Germanium (BEGe) detector. Radiometric analysis of 226Ra, 232Th and 40K in the soil samples from Fongo-Tongo and Mini-Matap were done with average activity concentration of 108.91 Bq/kg, 117.79 Bq/kg and 143.07 Bq/kg and, 113.15Bq/kg, 196.14 Bq/kg and zero were determined respectively. In-situ measurement of dose rate at 1 m above the ground and the annual effective dose values due to 226Ra, 232Th and 40K in 5 cm soil layer were determined using conversion factors by UNSCEAR. The average external hazard indexes in samples from Fongo-Tongo were 0.78 and 1.06 while the internal hazard indexes in samples from Mini-Matap were 1.07 and 1.37. Comparing these values with the worldwide values set by UNSCEAR we realized that avoidance of high exposure from gamma radiation due to NORM to the populace should be of concern