Many households in gold-mining regions of northern Tanzania have limited access to safe and reliable drinking water and rely on surface water, groundwater, and locally caught fish as key drinking-water and dietary sources, yet the radiological safety of these sources remains uncertain. This study evaluated age-dependent radiological risks from ingestion of naturally occurring radionuclides (234U, 238U, 226Ra, 210Po, 210Pb) in multiple water sources and in fish tissues (bones, gills and flesh) of African lungfish (Protopterus aethiopicus), Nile tilapia (Oreochromis niloticus) and African Catfish (Clarias gariepinus). Activity concentrations were determined by radiochemical separation followed by alpha spectrometry and gas-flow proportional counting. Annual effective dose (AED) and excess lifetime cancer risk (ELCR) were estimated using age-specific water and fish consumption rates. Groundwater, particularly from shallow wells, produced the highest exposures, with a maximum AED for a 5-year-old child, dominated by 234U, exceeding both the World Health Organization (WHO) screening level (0.1 mSv/y) and the International Commission on Radiological Protection (ICRP) public dose reference level (1 mSv/y). Fish consumption was the dominant pathway, with African lungfish consistently yielding the highest AEDs, followed by Tilapia and Catfish. The dose contributions were dominated by 210Pb (75% -96%) and 210Po (4% - 25%), while 234U, 238U, and 226Ra contributed <1%. The estimated ELCRs associated with consumption of all fish species, exceeded the USEPA acceptable risk range (10-6 - 10-4). Elevated 234U/238U activity ratios (>1) indicated preferential mobilisation of 234U via alpha-recoil, while low 210Po/210Pb ratios (<1) confirmed 210Pb predominance. These findings underscore the need for continued radiological monitoring and targeted mitigation to protect vulnerable communities.

Rare earth elements and valuable elements within Mkuju uranium core samples were analysed using EDXRF. Mean elemental concentrations for selected elements including Al, P, K, Ti, V, Mn, Fe, Y, Mo, Ag, Ba, La, Ce, and U were determined as 96445.79 μg/g, 547.19 μg/g, 25296.88 μg/g, 5926.33 μg/g, 116.26 μg/g, 455.02 μg/g, 60.1 μg/g, 142.34 μg/g, 15.8 μg/g, 493.98 μg/g, 67.53 μg/g, 118.68 μg/g, and 128.37 μg/g respectively. The Rare Earth elements: Y, La and Ce and valuable elements: Mo, Ag and U have enrichment factor of EF >1.5 which indicates that, these elements were formed from rocks through geological processes and can be mined at a profit. The valuable elements AL, P, K, Ti, V, Mn, Fe and Ba have enrichment factor of EF ≤ 1.5 which indicates that, these elements were formed from natural weathering processes. It is concluded that, despite the low concentration of the Rare Earth and valuable elements, the possibility of recovering both valuable and Rare Earth elements in Mkuju deposit is significant. Keywords: Rare Earth; Valuable Elements; Mkuju; EDXRF

Pre-mining natural radioactivity levels in soils over a 27.96 km2 site around the Manyoni Uranium Project in Tanzania were determined by a high purity germanium detector. The mean activity concentrations of 226Ra, 232Th, and 40K in soils were 227.43 +/- 38.79 Bq/kg, 65.22 +/- 3.70 Bq/kg, and 107.32 +/- 23.07 Bq/kg, respec-tively. The average radium equivalent activity (Raeq), external hazard index (Hex), and internal hazard index (Hin) at these concentrations were 328.95 Bq/kg, 0.89, and 1.50, respectively. The mean absorbed dose rate in air at 1 m above the ground (Da) was 148.94 nGy/h, and the mean outdoor annual effective dose (Ed) was 0.18 mSv/y. Additionally, natural radioactivity levels in soils over a 0.71 km2 site, which is inside the 27.96 km2 site, which is prone to mine dust pollution above healthy levels, were also determined. The mean activity concentrations of 226Ra, 232Th, and 40K in the soils from this site were 380.4 +/- 59.93 Bq/kg, 78.69 +/- 8.99 Bq/kg, and 70.40 +/- 7.91 Bq/kg, respectively. The corresponding means for Raeq, Hex, and Hin were 498.35 Bq/kg, 1.35, and 2.37, respectively. The mean Da and Ed were 226.21 nGy/h and 0.28 mSv/y, respectively. The average values of Ed at both sites were less than the public exposure limit of 1 mSv/y. This means that the sites have normal background radiation levels that do not endanger people's health when they engage in outdoor activities. When mining begins, the natural radioactivity levels obtained in this study, rather than national or global averages, can be used by mine owners or government agencies to assess the environmental effects of mining. Even after mining and during decommissioning, these baseline levels can also be used to measure how well the land has been restored.

In this study, pre-mining ambient gamma dose equivalent rates at 1 m above the ground were measured using a Gamma-Scout portable radiation survey meter at two sites, A and B, around the Manyoni uranium deposit in Tanzania. Site A is expected to receive mine-dust particles with an aerodynamic diameter ≤ 10 µm (PM10) that have mean annual ground level concentrations (AGLC) ≥ 10% of the WHO air quality guideline limit of 20 µg/m3, and Site B is expected to receive PM10 with a mean AGLC ≥ 20 µg/m3. At Site A, the average of the ambient dose equivalent rates was 0.25 ± 0.03 µSv/h and ranged from 0.08 to 0.69 µSv/h. Similarly, at Site B, the average of the ambient dose equivalent rates was 0.23 ± 0.02 µSv/h and ranged from 0.12 to 0.34 µSv/h. The effect of the local geology on the measured dose rates was also presented. Since the ambient dose equivalent is an operational quantity for area monitoring, the results of this study will be very useful for comparing with the operational monitoring results of Sites A and B once uranium mining starts in Manyoni. This can help mine operators and regulatory agencies keep an eye on any rise in background radiation so they can take the necessary measures to safeguard locals and the environment from the harmful effects of ionising radiation.

This study aimed at determining the concentrations of rare earth elements (REEs) in coal and coal fly ash (CFA) from three coal mines in Tanzania: Kiwira, Ngaka and Rukwa. The goal was to assess if these resources could be commercially viable for extracting REEs. Coal and CFA samples were analysed using X-ray fluorescence (XRF) spectrometry and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The total concentrations of REEs in the coal samples ranged from 89.48 parts per million (ppm) to 196.30 ppm, while in CFA samples, ranged from 362.55 ppm to 475.77 ppm. Computed percentage of critical REEs (REYdef, rel%) and outlook coefficient (Coutl) values ranged from 27.41% to 50.74% and 0.62 to 2.00, respectively. Based on the evaluation criteria proposed for assessing coal and coal ash as sources of REEs, the results suggest that the studied coal and CFA samples have the potential to be used as sources of REEs for economic development. These findings have important implications for the Tanzanian government and other relevant authorities, as they provide valuable insights into the feasibility of investing in the coal and coal ash as promising sources of REEs. This is particularly significant considering the high global demands for REEs.

This study employed PM10 source parameters and pre-processed topographical and meteorological data as input into the AERMOD atmospheric dispersion model to demarcate pollution-prone areas around the Manyoni Uranium Project. Knowing these areas before mining is an important step toward establishing efficient and effective environmental baseline data. This is because resources for collecting the data will be concentrated in areas with higher contamination potential. In this regard, AERMOD predicted that the regions suitable for pollution demarcation would be 25.55 km2, 25.85 km2, and 27.96 km2 if the prospective mine at Playa C1 operated for 5, 7, and 10 years, respectively. Within the demarcated areas, AERMOD predicted that the maximum annual ground level concentration of PM10 averaged over 5, 7, and 10 years would be 22.2 µg m−3, 22.8 µg m−3, and 25.7 µg m−3, respectively. These values are 11

A few studies have reported the risks of secondary cancer in patients after radiation therapy in Tanzanian hospitals. This study was designed to assess non-target organ doses from Co-60 teletherapy for patients with nasopharyngeal cancer and to estimate the risk of radiation-induced secondary cancer. Specific organ-absorbed doses were evaluated in anatomically realistic 15-year-old and adult male phantoms based on Monte Carlo simulation. The assessed organ doses were used to calculate the lifetime secondary cancer risks in non-target organs according to the BEIR VII risk models. Survival information and the baseline cancer risks were associated with statistical data for the Tanzanian population. The average absorbed doses in non-target organs depended heavily on the distance from the target isocentre and patient's age. Organs near the tumour target, such as the salivary glands, brain, thyroid glands, eye bulb and oesophagus, received very high absorbed doses. The absorbed doses decreased exponentially towards the testis and prostate which are far from the tumour target. The highest received absorbed doses in non-target organs were due to the leakage in the gantry head and scattered radiation from collimator and inside the patient body. The absorbed doses were higher for young patients than in adults because of the larger body area exposed to high-dose radiation. The lifetime attributed risks for all organs considered were relatively lower than the baseline cancer risks. Results can help provide future database about radiation-induced second primary cancer incidence after Co-60 external beam radiation therapy for nasopharyngeal cancer in Tanzania and in many other developing countries.

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;

We have designed an extended range neutron long counter on the basis of work optimized using SuperMC code. The problem of the existing traditional long counters is that their response function falls rapidly above 5 MeV. We proposed a new designed by adding two layers of converter material inside the polyethylene moderator. The relatively low density chromium and high density lead metals convert high energy neutron by (n, xn) spallation reaction. This produces more neutrons of lower energies, which have higher probability of being detected by thermal 3He-counter. The response function at lower neutron energies was improved by inserting small polyethylene cylinder in front of 3He counter. In this design we achieved to extent the flat response function of the long counter from few keV up to 150 MeV. The total fluctuation of response curve is less than ±9% over the entire energy range. The designed long counter is suitable to be used as neutron monitor for monitoring neutron fluence at high-energy neutron source.

In this study, a reduced size neutron long counter with improved response function was designed using SuperMC simulation code. The main parts of the reduced size long counter are 3He proportional counter, cylindrical moderators made of polyethylene, chromium metal converter, neutron absorber material and outer aluminum cover. A 1.5 cm thick layer of chromium metal was embedded into the hydrogen-rich moderator to enhance response of the long counter at high neutron energies. The radius and length of the long counter was reduced to 15 cm and 35 cm, respectively. In this design we managed to obtain a flat response function from a few keV to 20 MeV energy range. The angular response function, determined at 0.5 MeV and 14 MeV neutron energies, confirmed that the reduced size long counter designed in this study is not significantly affected by in-scattered neutrons. The reduced size long counter is suitable for use as a standard transfer instrument for monitoring neutron fluence in mono-energetic neutron fields.

A low-sensitivity neutron long counter was designed as a standard directional flow detector to monitor neutron fluence reference values of an accelerator-based 14-MeV D-T neutron source with yield of 10(13) n s(-1). The energy response over 6 MeV was improved using a tungsten radiator, which acts as an energy converter via the (n, xn) reaction. Different parameters were optimised to flatten the neutron energy response over a wide energy range. A simulation of the designed neutron long counter was performed using the Monte Carlo codes SuperMC. The response function is relatively flat in the energy range of 1 keV-20 MeV. The results show that the maximal relative variation is ∼7.8 %.

The discovery of high concentration uranium deposit at Mkuju, southern part of Tanzania, has brought concern about the levels of natural radioactivity at villages in the neighborhood of the deposit. This study determined the radioactivity levels of 30 soil samples and 20 water samples from Likuyu village which is 54 km east of the uranium deposit. The concentrations of the natural radionuclides 238 U, 232 Th, and 40 K were determined using low level gamma spectrometry of the Tanzania Atomic Energy Commission (TAEC) Laboratory in Arusha. The average radioactivity concentrations obtained in soil samples for 238 U (51.7 Bq/kg), 232 Th (36.4 Bq/kg), and 40 K (564.3 Bq/kg) were higher than the worldwide average concentrations value of these radionuclides reported by UNSCEAR, 2000. The average activity concentration value of 238 U (2.35 Bq/L) and 232 Th (1.85 Bq/L) in water samples was similar and comparable to their mean concentrations in the control sample collected from Nduluma River in Arusha.