A metrological characterisation of a high-energy neutron field at the iThemba Laboratory for Accelerator-Based Sciences (LABS) was combined with Monte Carlo radiation transport simulations to estimate the absorbed dose delivered to vials of human blood for an experimental setup relevant to conducting radiobiology experiments at this facility. Neutrons with a peak energy of 62.34(37) MeV were produced by a 66.48 MeV proton beam irradiating an 8.0 mm lithium target. The neutron beam energy distribution and fluence were characterised at emission angles of 0 degrees and 16 degrees via Time-of-Flight measurements with a BC-501A liquid scintillation detector, a 238U fission ionisation chamber, and two beam monitors. These measurements were combined with Monte Carlo radiation transport simulations developed in Geant4 to calculate the absorbed dose that would be delivered to four vials of human blood contained in high-density polyethylene phantoms placed at a distance of 4.300 m from the target during a typical irradiation. The absorbed dose delivered to each blood vial per unit monitor count was estimated and combined with measured monitor count rates to determine the absorbed dose rate. Depending on the vial position in the phantom, dose rates ranged from 24.36(78) mGy hour-1 to 26.22(84) mGy hour-1 at 0 degrees, and from 13.16(42) mGy hour-1 to 14.21(46) mGy hour-1 at 16 degrees.

The activity concentrations of natural radionuclides Ra-226, Th-232 and K-40 in 19 soil samples from Zabili uranium exploration area were measured using a low-background digital gamma-ray spectrometer equipped with broad energy germanium detector. The activity concentrations of U-238, Th-232, and K-40 range from 16.5 to 1110.9 Bq.kg(-1), 19.45 to 76.97 Bq.kg(-1), and 3.28 to 839.5 Bq.kg(-1), with their mean values of 478.0, 58.9, and 562.5, respectively. In addition, radiological hazard parameters from the activity concentrations obtained were assessed by estimating radium equivalent activity, external and internal hazard index, indoor and outdoor absorbed gamma dose rate and the corresponding annual effective dose, effective dose rate to different body organs and tissues, and excess lifetime cancer risk. Derived radiological hazard indices have been revised in accordance with relevant national and international legislation and guidelines. The radiological hazard parameter values were found to be above the relevant limit values for soils. In order to investigate the distribution of radionuclides and associated health hazard parameters in the study area, a statistical study was performed.

In this work, a high-purity germanium (HPGe) detector in a low-background setup was used to determine the activity concentrations of 238 U, 232 Th, and 40 K in soil samples collected in and around some gold mining areas of the Mayo-Kebbi region in Chad. Subsequently, the radiological risks due to these natural radionuclides were also assessed. The activity concentrations of 238 U, 232 Th, and 40 K varied from 1.42± 0.32 to 430.88± 7.3 Bq/kg , 1.19± 0.98 - 56.61± 1.61 Bq/kg , and 27.38± 2.17 – 840.51± 8.99 Bq/kg with average values of 29.67± 15.80 (STD) Bq/kg , 11.98± 2.80 (STD) Bq/kg , and 234.43± 43.28 (STD) Bq/kg , respectively. The highest values of 238 U, 232 Th, and 40 K concentrations were found in soil sample collected at a gold mining area of Zabili. The 232 Th/ 238 U activity ratio was consistently lower than the naturally occurring equilibrium ratio of 1.1 at the majority of the sampling sites. The assessment of the 232 Th/ 40 K mass ratio revealed the existence of montmorillonite, kaolinite, and heavy thorium-bearing minerals in the regions under investigation. The mean annual effective dose of the soil samples collected in the studied area was found to be 0.18 mSv/y. The calculated mean values of the external hazard index ( H ex ) and the internal hazard index ( H in ) of the study area were 0.18 and 0.26, respectively. Correlation studies between 238 U versus 232 Th, 40 K versus 238 U, and 40 K versus 232 Th were performed. The results showed a good correlation between the pairs ( 238 U, 232 Th); however, a weak correlation was observed between the pair ( 238 U, 40 K) and ( 232 Th, 40 K). In order to investigate the statistical variation of the data and its implications on environmental exposure, the hierarchical binary cluster tree was implemented.

Establishing a deep underground physics laboratory to study, amongst others, double beta decay, geoneutrinos, reactor neutrinos and dark matter has been discussed for more than a decade within the austral African physicists' community. PAUL, the Paarl Africa Underground Laboratory, is an initiative foreseeing an open international laboratory devoted to the development of competitive science in the austral region. It has the advantage that the location, the Huguenot tunnel, exists already and the geology and the environment of the site is appropriate for an experimental facility. The paper describes the PAUL initiative, presents the physics prospects and discusses the capacity for building the future experimental facility.

The aim of the present study was to investigate deviations between prescribed from delivered dose for cervical cancer patients treated at Ocean Road Cancer Institute using Equinox 80 Tele-cobalt machine. In this work, anterior-posterior (AP) and posterior-anterior (PA) fields using Source-to-Axis Distance (SAD) technique was used. Measurements of entrance doses were taken using calibrated diode detector in three groups of patients. In group 1, only 15 patients out of 31 curative intent patients received doses lower than ± 5% of 2 Gy as compared to the prescribed dose. In group 2, 1 measurement was done for 9 patients who received palliative single dose of 10 Gy and 2 patients out of 9 received doses within the range of ± 5% of the prescribed dose. In group 3, 1 daily measurement was done for 12 patients who were prescribed a curative dose of 50 Gy in 25 fractions. The maximum observed deviation was + 25.08%, while that of minimum was – 0.59%. Since significant deviations between prescribed and delivered doses exist, there is a need to conduct another study using both patient and machine related factors to refine the problem of high dose deviations among the patients Keywords: Tele-cobalt machine; in-vivo dosimetry; measured and delivered dose; cervical cancer; diode detector

There are few experimental data for neutron cross-section libraries in (n,xn) reactions for various materials at energies above 20 MeV. For neutron energies above 20 MeV, these set of (n,xn) reactions are important for neutron fluence monitoring and spectra unfolding for future generation IV nuclear reactors. There were attempts to measure the cross-sections on natural cobalt and bismuth at incident neutron energies of about 90 MeV and 140 MeV. These measurements were made using the quasi-monoenergetic neutron facility at iThemba LABS, South Africa. In addition, at The Svedberg Laboratory facility in Sweden, similar experiments were performed on natural Yttrium. The measured cross-sections were compared with some of the few available data for neutron-induced reactions at high energies. Data collected from these two facilities, required corrections to be made for the contribution of the low energy tail (continuum) in the incident neutron spectrum. Preliminary results from iThemba LABS showed large discrepancy which we suspect was due to instability of the proton beam during the irradiations. Follow-up experiments are planned to accurately determine the uncertainty contributions, with additional data at other neutron energies.

This study aimed on the investigation of depth dose curves from beeswax, water and paraffinphantoms using FLUKA Monte Carlo code. In order to test the validity of FLUKA code,computational values of depth doses in water, beeswax and paraffin have been obtained using thiscode. The relative average coefficient of variation of percentage depth dose was observed to beless than 0.38% between beeswax and water, below 0.2% between water and paraffin and 0.98%between beeswax and British Journal of Radiology supplement 25 data. The deviations ofpercentage depth doses within the beeswax phantom material were also calculated and it wasconcluded that, among the treatment fields, the average coefficient of variation was about 0.74%for 7 × 7 cm2 and 1.23% for 20 × 20 cm2. The minor deviation in percentage depth dose obtainedin this work demonstrates that beeswax phantom has a potential to provide a better alternativematerial for dose calculations, and hence can be used as substitute material for in-vivo dosimetry inexternal beam radiation therapy using Theratron Equinox 80 Cobalt-60 unit. Keywords: FLUKA; Monte Carlo code; beeswax; percentage depth dose; phantom;

Abstract. Neutron Activation Analysis (NAA) is among the most accurate and reliable analytical techniques that is be used for the simultaneous analysis of multiple elements present in a sample. The technique involves exposing samples to a flux of neutrons for a predetermined time and then measuring the emanating characteristic γ-rays from the activated elements using a calibrated γ-ray spectrometer. A successful analysis depends on various factors, such as the neutron energy, neutron flux, and the sample matrix. The aim of this study was to investigate the feasibility of using the technique for routine elemental pollution measurements in soil and water in the Richards Bay area. Richards Bay is an industrialized area and consists of industries that can emit elements such as aluminum, iron, lead, arsenic etc. The calibration of the neutron facility using a mixed metals sample showed the possibility to analyze Al and Fe using 14 MeV neutrons (from the STNG) and that Al can be identified using a neutron flux from the Am-Be source.

Acid mine drainage samples were collected from the central basin of the Witwatersrand basin in South Africa to study the removal of radioactivity. The samples were analyzed for gross alpha/beta activity, specific radionuclides, metals and anions concentration. The pH of the acid mine drainage samples was then varied and ion-exchange column experiments were carried out to remove radioactivity from acid mine drainage. The gross alpha activity ranged between 60 and 75 Bq/L and gross beta activity ranged from 56 to 70 Bq/L. The speciation of uranium, thorium and radium was modelled using Joint Expert Speciation System. The speciation had a big influence on the removal of radio-activity from acid mine drainage using ion exchange resin. The optimum pH was determined to be 8. Acid mine drain-age samples treated at this pH showed gross alpha activity below the detection limit of 0.03 Bq/L for all samples and gross beta activities below 5 Bq/L for 9 of the 10 treated samples

The study was conducted to understand, (a) the effect of pH on the speciation of uranium in acid mine drainage and (b) determine the effect of uranium speciation on the removal of gross alpha activity from acid mine drainage. Speciation modeling predicted a dominance of neutral and positively charged species under acidic and neutral conditions. Negative species become dominant from pH 8. The effectiveness of the anionic exchange resin to remove gross alpha activity was lower under acidic conditions (pH < 6) compared to alkaline conditions (pH ≥ 8).