The present work deals with the radioactivity of samples of tin tailings collected from a mining site in Jos, Nigeria. The activity concentrations of the samples were measured using a gamma-ray spectrometer with a hyper-pure germanium detector. In situ dose rates at the site were also measured using a precalibrated survey meter. Potassium-40 was not detected in any of the studied samples. The activity concentrations of (238)U and (232)Th ranged from 17.1 x 10(2) to 16.6 x 10(3) Bq kg(-1) and from 52.9 x 10(2) to 47.5 x 10(3) Bq kg(-1), with mean values of 72.2 x 10(2) and 16.8 x 10(3) Bq kg(-1), respectively. The absorbed dose rates were between 4.0 and 36.3 microGy h(-1), with a mean value of 13.5 microGy h(-1), which is much higher than the world average of 0.06 microGy h(-1) for soil. The calculated effective dose rates varied between 2.8 and 25.4 microSv h(-1), with a mean value of 9.4 microSv h(-1), whereas the effective dose rates obtained for the in situ measurement varied between 6.0 and 28.0 microSv h(-1). The annual gonadal dose equivalent was calculated as 92.4 mSv. This is much higher than the world average dose equivalent rate to individuals from soil (0.30 mSv y(-1)).

Coal fired power plants produce significant amounts of ashes, which are quite often being used as additives in cement and other building materials. Coal contains trace quantities of 226 Ra, 232 Th and 40 K. The concentrations of these radionuclides are usually low in the coal, but enriched in fly ash. The activity concentrations of natural radionuclides in fly ash and soil samples in the vicinity of Orji River thermal power station in Nigeria was determined by gamma ray spectroscopy method using NaI(Tl) detector. The mean activity concentrations of 226 Ra, 232 Th and 40 K in the fly ash were 40.8 ± 11.6, 49.1 ± 9.3 and 321 ± 17 Bq•kg −1 , respectively. Coarse fly ash collected from the dump site had mean activity concentrations of 28.2 ± 8.3, 37.6 ± 5.0 and 335 ± 32 Bq•kg −1 , respectively for 226 Ra, 232 Th and 40 K. Soil samples collected at about distances of 10 m from the dump site had 32.7 ± 4.3, 40.0 ± 4.2 and 298 ± 15 Bq•kg −1 , respectively. Those collected at about distances of 100 m from the dump site had 39.1 ± 11.2, 34.1 ± 5.2 and 257 ± 19 Bq•kg −1 , respectively. Occupational dose received by workers due to exposure to the fly ash ranged between 33.0 and 61.2 µSv•y −1 with a mean value of 47.1 ± 8.4 µSv•y −1 , which is below the intervention exemption level of 1 mSv•y −1. The radium equivalent activity concentration, external and internal hazard indices of the fly ash were below the recommended maximum values for building materials. The mean outdoor absorbed dose rate and the annual effective dose obtained in the vicinity of the plant were 49.7 ± 4.0 nGy•y −1 and 0.30 ± 0.02 mSv (dump site), 51.7 ± 3.6 nGy•y −1 and 0.32 mSv (soil 10 m from dump site), 49.4 ± 4.9 nGy•y −1 and 0.30 ± 0.03 mSv (soil 100 m away from dump site), which are lower than the world average. The results obtained in this study show that there is no significant radiological impact of the fly ash on both the workers and the public from radiation protection point of view.

Radioactivity concentrations of concrete building block samples made and used in Jos, Nigeria, were determined using a gamma ray spectrometry method. The mean values of the radioactivity concentrations were calculated as 66, 126 and 589 Bq kg(-1) for (226)Ra, (232)Th and (40)K, respectively. The radium equivalent activities ranged between 131 and 712 Bq kg(-1), with six of the samples exceeding the UNSCEAR reported maximum permissible level of 370 Bq kg(-1). The mean radium equivalent activity (292 Bq kg(-1)) is higher than the values available in the literature for some countries by factors ranging between 2 and 5, a situation that can be traced to the practice of sourcing sand aggregates from mining sites. The indoor annual effective dose for a dwelling of dimension 3.6 x 3.6 x 3.0 m(3) was calculated as 0.81 mSv.

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The natural radionuclide contents of some concrete building blocks randomly sampled in the city of Ibadan have been determined using NaI(Tl) gamma ray spectrometry. The radionuclides 226Ra, 232Th and 40K were determined with city mean specific activities 47 +/- 21 Bq.kg-1, 52 +/- 21 Bq.kg-1, and 352 +/- 222 Bq.kg-1, respectively. These activities amount to a radium equivalent of about 150 Bq.kg-1, which is lower than the recommended maximum value of 370 Bq.kg-1. The mean value of the external hazard index was found to be 0.41 which implies that the building blocks used in the city of Ibadan are within the acceptable level of radioactivity. The mean indoor gamma dose equivalent to individuals due to the walls was calculated to be 412 microSv.y-1 and the collective dose equivalent 563 man.Sy.y-1.