Assessment of indoor radon-222 concentrations in the vicinity of Manyoni uranium deposit, Singida

This study aimed to assess indoor radon concentrations in the vicinity of the Manyoni Uranium Deposit in Singida. The concentrations were measured for two months in 32 houses in the vicinity of Manyoni Uranium Deposit and 9 houses at Manyoni town using a portable radon gas monitor (Alpha –GUARDTM). The radon concentrations ranged from 27±3 to 518±28 Bq/m3with the overall mean of 166±12 Bq/m3 which is above recommended values of 100 Bq/m3 and 148 Bq/m3 set by WHO (World Health Organization) and EPA (Environmental Protection Agency's), respectively. The overall mean of indoor radon concentrations from each village were Kipondoda (169±13 Bq/m3), Muhalala (177±16 Bq/m3), Mwanzi, (287±13 Bq/m3), Mitoo (325±21 Bq/m3) and Majengo (377±23 Bq/m3) which exceed the limit set by WHO (World Health Organization) and EPA (Environmental Protection Agency). The value of 325±21 Bq/m3 and 377±23 Bq/m3 from Mitoo and Majengo respectively, exceed the limit of 300 Bq/m3 recommended by ICRP (International Commission on Radiation Protection). Thus there is a non-negligible probability of incurring stochastic effects for people living in the vicinity of Manyoni Uranium mine. It is recommended that human activities should be controlled   near the uranium deposits and dwelings should be well ventilated.Keywords: Indoor radon, Concentrations, Cancer, Manyoni uranium deposit, Alpha –GUAR

Determination of radon gas and respirable ore dust concentrations in the underground merelani Tanzanite mines

This study has estimated the concentrations of radon gas and respirable ore dust in the Merelani underground tanzanite mines. Two different portable monitors were used to measure the radon gas and respirable ore dust concentrations respectively. The mean radon gas concentration (disintegrations per second per cubic meter) ranges from 40.1 Bq/m3 to 4.2x103 Bq/m3 with the geometric mean of 118.4 Bq/m3 which is below the ICRP workplace guidance level of 500 - 1500 Bq/m3. The estimated mean annual effective dose (D) was 1.6 mSv which is significantly lower than the external exposure annual effective dose of 20 mSv and the annual organ dose limit of 2.4 mSv. The overall concentrations of respirable ore dust arithmetic mean was 18.2 g/m3 and the geometric mean of 2.1 g/m3 which is very high compared to the guidance level of 2 g/m3. The respirable dust was mainly produced during drilling and blasting of rocks, under normal conditions the geometric mean of respirable gas concentrations was 0.8 g/m3. It is recommended that immediate intervention such as providing proper ventilation during the two processes to dilute radon levels in underground mines and the monitoring should be done regularly

Impact of mechanical activation of reactant powders on the solid-state-densification of Zn1-xLixO and Zn0.7Li0.28Mg0.02O ceramics

This paper presents effects of powder mechanical activation and controlled sintering on the densification properties of ZnO ceramics with Lithium (Li) and Magnesium (Mg) dopants. Dense bodies of Zn1-xLixO and Zn0.7Li0.28Mg0.02O ceramics were prepared via solid-state-reaction of mechanically activated mixtures of ZnO, Li2CO3 and MgO reactant raw powders. The density, surface microstructure, porosity and phase purities of the ceramics were investigated with a Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) techniques. The study highlights mechanical activation processes such as milling, calcination and compaction steps that are needed to overcome complicated interactive reactions during conventional sintering of Zn1-xLixO and Zn0.7Li0.28Mg0.02O ceramics that have been reported to show ferroelectric behavior. The results show that, densely packed single phase Zn1-xLixO and Zn0.7Li0.28Mg0.02O ceramics with average relative density values above 96% and single phase hexagonal wurtzite crystalline structure were achieved at a sintering temperature of 1000 °C for 2 h in air