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

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

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

Monte Carlo method for gamma spectrometry based on GEANT4 toolkit: Efficiency calibration of BE6530 detector

The combination of gamma-ray spectrometry, the development of related Monte Carlo method and the GEANT4 (GEometry ANd Tracking) toolkit have been developed for gamma spectrometry simulation. The main objective was to validate simulation models of broad energy germanium (BEGe) detector geometry built in our laboratory (BE6530 model). Monte Carlo simulation of the geometry of BE6530 detector for efficiency calibration was carried out with GEANT4 toolkit. The simulated efficiencies curves using MC were compared with experimental results. Measurement uncertainties for both simulation and experimental estimations of the efficiency were assessed in order to see whether the consequences of the realistic measurement fall inside adequate cut-off points. The validation of the simulation was carried out by experimentally estimating the activity concentration in a reference sample and the comparison showed good correlation between experimental and simulation. Therefore, from the outcomes of this study, it can be concluded that Monte-Carlo simulation is a helpful, reasonable option that additionally gives more prominent adaptability, greater flexibility, precision and accuracy, and gained time when determining the detector response and efficiency in routine of environmental radioactivity monitoring.SpectroGammaGeant

Multivariate statistical assessment of natural radioactivity and radiological hazards data of cement building materials mainly used in Cameroon

The present study aimed to assess radioactivity level in thirty cement samples from five main cement types manufactured and commonly used in Cameroon using a gamma-ray spectrometric technique based-Broad Energy Germanium (BEGe-6530 model) Canberra coaxial detector. The activity concentrations of 226 Ra, 232 Th, and 40 K in cement samples varied from 9.49 to 33.24, 15.54 to 48.15, and 60.78 to 285.7 Bq kg− 1, respectively. Radiological parameters and hazard indexes such as the Radium equivalent activity, the outdoor and indoor absorbed gamma dose rate, the outdoor and indoor annual effective dose, the outdoor and indoor excess lifetime cancer risk, the annual gonadal dose equivalent, the activity utilization index, the representative level index, the external and internal hazard indexes, and the gamma and alpha indexes were assessed and compared with the recommended standard

Precision measurement of radioactivity in Gamma-rays spectrometry using two HPGe detectors (BEGe-6530 and GC0818-7600SL models) comparison techniques: Application to the soil measurement.

To obtain high quality of results in gamma spectrometry, it is necessary to select the best HPGe detector for particular measurements, to calibrate energy and efficiency of gamma detector as accurate as possible. To achieve this aim, the convenient detector model and gamma source can be very useful. The purpose of this study was to evaluate the soil specific activity using two HPGe model (BEGe-6530 and GC0818-7600SL) by comparing the results of the two detectors and the technics used according to the detector type. The relative uncertainty activity concentration was calculated for 226Ra, 232Th and 40K. For broad energy germanium detector, BEGe-6530, the relative uncertainty concentration ranged from 2.85 to 3.09% with a mean of 2.99% for 226Ra, from 2.29 to 2.49% with a means of 2.36% for 232Th and from 3.47 to 22.37% with a mean of 12.52% for 40K. For GC0818-7600SL detector, it was ranged from 10.45 to 25.55% with a mean of 17.10% for 226Ra, from 2.54 to 3.56% with a means of 3.10% for 232Th and from 3.42 to 7.65% with a mean of 5.58% for 40K. The average report between GC0818-7600SL model and BEGe-6530 model was calculated and showed the mean value of 3.36. The main study was based on the following points: • Determination of The relative uncertainty activity concentration of 226Ra, 232Th and 40K • Determination of the relative uncertainty related to the radium equivalent activity to compare the performance of the two detection systems • Proved that the activity concentration determination in gamma spectrometry depended on the energy range emitted by a radionuclide. This study showed that the standard deviation measurement was less important to the result realized with BEGe-6530 HPGe model. Our findings were demonstrated that the results of the Broad Energy Germanium detector were more reliable

Barite concrete for 252Cf spontaneous neutron shielding based on Monte Carlo computation

Recently, neutron applications as neutron imaging widespread and safety issue related to high neutron penetration is still a concern in neutron industry. Especially, the design of a structure to shield neutron requires structural stability, high-density material, and large fast-neutron removal cross-section while it must be cost-benefit evaluated and using available materials. In this regard, attention has been paid on different barite composite shielding material and their neutron attenuation property based on the Monte Carlo calculation using Particle and Heavy Ion Transport code System. Different types of material as barites aggregate, barites cement, and barites concrete were investigated to find the most appropriate for fast neutron shielding, especially spontaneous neutron emitted from the Cf-252 source. Preliminary results obtained from the geometry presented in Fig. 1 are displayed in Fig. 2. As the barite concrete has high density compared to other materials, and high removal cross-section, the dose computation throughout the geometry and in different tallies show that it is the most appropriate neutron shielding in this case. Besides, gamma radiations generated by neutron interaction are easily shielded by barite concrete. Fast neutron shielding properties obtained by Monte Carlo simulation here are comparable to the experimental value described by William J. Grantham (1961). Barite concrete fast-neutron attenuation good properties were expected as it is the material with the highest removal cross-section among the investigated compound

Optimal measurement counting time and statistics in gamma spectrometry analysis: The time balance

The optimal measurement counting time for gamma-ray spectrometry analysis using HPGe detectors was determined in our laboratory by comparing twelve hours measurement counting time at day and twelve hours measurement counting time at night. The day spectrum does not fully cover the night spectrum for the same sample. It is observed that the perturbation come to the sun-light. After several investigations became clearer: to remove all effects of radiation from outside (earth, the 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 measured 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 on 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