A survey of background radiation dose rates and radioactivity in Tanzania.

Potential terrestrial sources of naturally occurring elevated radiation levels have been identified in Tanzania. Thus, efforts are currently being undertaken to create a natural radiation database, in the form of a radiation level map of natural radioactivity, to be used to assess the associated radiation risk to public and workers. Background radiation dose rate was determined with thermoluminescent dosimeters for 7 y (1993-1999) in five stations. The average background radiation dose rates for these stations were as follows: Tropical Pesticides Research Institute (TPRI) (102 +/- 7 nGy h(-1)), Same (98 +/- 2 nGy h(-1)), Namanga (98 +/- 5 nGy h(-1)), University of Dar Es Salaam (99 +/- 2 nGy h(-1)), and Kilimanjaro Christian Medical Center (121 +/- 3 nGy h(-1)). These stations were found convenient from an economic point of view since the project has no funds to cover wider and/or more remote areas in Tanzania. For the sake of comparison, similar measurements were made for the same period at Minjingu phosphate mine. The mine was one of the suspected areas with elevated levels of natural radioactivity. The radiation dose rate measured in this mine was about fourteen times higher (1,415 +/- 28 nGy h(-1)) than the average value obtained in northern Tanzania (98 nGy h(-1)). The high average activity levels of phosphate (5760 +/- 107 Bq kg(-1) for 261Ra, 497 +/- 5 Bq kg(-1) for 228Ra, 350 +/- 6 Bq kg(-1) for 228Th, and 280 +/- 5 Bq kg(-1) for 40K) and radiation dose rate recorded show that Minjingu phosphate mine has higher values than the highest radioactivity in phosphate compiled by the United Nations Scientific Committee on the Effect of Atomic Radiation. In view of these findings, a comprehensive risk-management strategy for reduction of radiation risk to the public and mine workers should be put in place. Efforts are currently being made to seek support to improve the background radiation database for subsequent assessment of radiation risk to miners and the societies in the vicinity of these mines in Tanzania.     

(226)Ra, (232)Th and (40)K contents in soil samples from Garhwal Himalaya, India, and its radiological implications

The exposure of human beings to ionising radiation from natural sources is a continuing and inescapable feature of life on earth. Natural radionuclides are widely distributed in various geological formations and ecosystems such as rocks, soil groundwater and foodstuffs. In the present study, the distribution of (226)Ra, (232)Th and (40)K was measured in soil samples collected from different lithological units of the Thauldhar and Budhakedar regions of Garhwal Himalaya, India. The collected soil samples were analysed using gamma ray spectrometry. The activity concentrations of the naturally occurring radionuclides (226)Ra, (232)Th and (40)K in these soil samples were found to vary from below detection level (BDL) to 131 +/- 18 Bq kg(-1), 9 +/- 6 to 384 +/- 53 Bq kg(-1) and 471 +/- 96 to 1406 +/- 175 Bq kg(-1), respectively. The distribution of radionuclides depends upon the rock formation and chemical properties within the earth. The activity concentrations vary widely depending on the sample origin. The external absorbed gamma dose rates due to (226)Ra, (232)Th and (40)K were found to vary from 49 to 306 nGy h(-1). The average radium equivalent activity from these soil samples was 300 Bq kg(-1).     

Natural radioactivity in the soil samples of Coastal Karnataka of South India

Studies on radiation level and radionuclide distribution in the region of Coastal Karnataka, India, were undertaken. The purpose of this study is to provide baseline data on radiation level and radionuclide distribution in the region for the future assessment of the impact of the nuclear and thermal power stations that are being set up in the region. Further, this study may reveal information on the transportation of radionuclides in the environment. The external gamma dose rates in air have been measured throughout Coastal Karnataka using a sensitive plastic scintillometer. The measured dose rates include both terrestrial and cosmic ray components. The gamma dose rates in air range from 26 to 174 nGy h(-1) with a median value of 74 nGy h(-1). The activities of naturally occurring radionuclides in the soil samples of the region were measured using HPGe gamma ray spectrometry, and the resulting doses in air were calculated. The activity of 40K varies from 61.0 to 316.7 Bq kg(-1) with a median of 117.5 Bq kg(-1); the activity of 226Ra varies from 20.1 to 62.3 Bq kg(-1) with a median value 35.0 Bq kg(-1) and that of 232Th from 14.3 to 48.6 Bq kg(-1) with a median value of 29.8 Bq kg(-1). The mean absorbed dose rate in air due to naturally occurring radionuclides is found to be 41.5 nGy h(-1). In addition to this, the correlations between 226Ra and 40K, 232Th and 40K, and 226Ra and 232Th were computed from the results of the concentration of these naturally occurring radionuclides. A weak correlation was observed between 226Ra and 40K and between 232Th and 40K while a moderately good correlation was observed between 226Ra and 232Th. The results of these systematic investigations are presented and discussed in this paper.     

Naturally occurring radioactive material from the aluminium industry--a case study: the Egyptian Aluminium Company, Nag Hammady, Egypt.

The activity concentrations and the gamma-absorbed dose rates of the terrestrial naturally occurring radionuclides (226)Ra and (232)Th were determined in samples of bauxite, alumina and aluminium dross tailings industrial waste (used to produce two types of alums) using high purity germanium (HPGe) gamma ray spectrometry. The bauxite and alumina are imported by Egyptalum (The Egyptian Aluminium Company, Nag Hammady, Egypt) from Guinea and India. The activity concentrations in the bauxite range from 29 +/- 1 to 112 +/- 6 Bq kg(-1) for (226)Ra, and 151 +/- 8 to 525 +/- 12 Bq kg(-1) for (232)Th, with mean values of 62 +/- 8 and 378 +/- 50 Bq kg(-1), respectively. With respect to alumina and tail, the mean values are 5.7 +/- 1.1 and 8.4 +/- 0.8 Bq kg(-1) for (226)Ra and 7.2 +/- 1.6 and 10.7 +/- 1.2 Bq kg(-1) for (232)Th. Potassium-40 was not detected in any of the studied samples. The measured activity concentrations of (226)Ra and (232)Th in bauxite are higher than the world average while in alumina and tail they are lower. As a measure of radiation hazard to the occupational workers and members of the public, the Ra equivalent activities and external gamma dose rates due to natural radionuclides at 1 m above the ground surface were calculated. The external gamma-radiation doses received by the Egyptalum workers are 97, 409, 8.5 and 12.7 microSv y(-1) for the Guinean and Indian bauxite, the alumina and tail, respectively, which is well below the recommended allowed dose of 1 mSv y(-1) for non-exposed workers.     

降札异常高氡温泉天然辐射外照射水平调查

目的调查降札温泉区域的天然1辐射水平,掌握温泉区域的人员外照射剂量。方法采用便携式x-1剂量率仪和x-γ射线巡测仪对周围环境7照射量率进行测量,采用高纯锗γ谱仪进行土壤、河床沙样品进行比活度测量。结果该区域1辐射水平和放射性核素含量都很高,温泉小院中1辐射均值9630nGy／h,为四川省室外平均水平的150倍。温泉周围建筑物室内均值为3461nGy／h,最高值28718nGy／h,为四川省室内平均水平的38和312倍。结论该区域异常高水平γ照射量率,主要是该区域存在铀矿浅层露头、矿渣铺垫院子、采用铀矿石修建房屋、土壤中含高比活度放射性核素238u、236Ra等因素所致,温泉水流入牛棚沟,使放射性核素随河流迁移,对环境造成一定的污染。     

Measurement of activity concentrations of natural radionuclides in the topsoil of IITA Ibadan by gamma-ray spectrometry.

The activity concentrations of the natural radionuclides in the soils at the International Institute of Tropical Agriculture, (IITA), Idi-Ose, Moniya, Ibadan, Nigeria were investigated using a NaI (Tl) scintillation detector coupled with a Canberra series 10 plus multichannel analyser as the detecting device for gamma scintillation spectroscopy. The whole area was divided into grids and soil samples were collected from the points of intersection of the grids. The average activity concentrations obtained for the three radionuclides (40K, 238U and 232Th) were 180.08 +/- 90.54 Bq kg(-1) for 40K, 8.901 +/- 5.063 Bq kg(-1) for 238U and 11.01 +/- 7.686 Bq kg(-1) for 232Th. The average values of the absorbed dose rate for each radionuclide were found to be 7.33 nGy h(-1) for 232Th, 7.55 nGy h(-1) for 40K and 3.82 nGy h(-1) for 238U. The average (baseline) of the total absorbed dose rate was found to be 18.72 +/- 8.11 nGy h(-1). The baseline average outdoor annual effective dose equivalent at IITA due to the concentrations of the radionuclides was found to be 22.95 +/- 9.94 microSv y(-1). This value is low compared to the world average of 70 microSv y(-1) specified by UNSCEAR for an outdoor effective dose. Hence the probability of occurrence of any of the health effects of radiation is low.     

Natural soil gamma radioactivity levels and resultant population dose in the cities of Zacatecas and Guadalupe,Zacatecas, Mexico

The study of natural gamma radioactivity was made to determine the concentrations of natural radionuclides in soil. Twenty soil samples collected in the cities of Zacatecas and Guadalupe and their suburban areas in the Mexican state of Zacatecas were analyzed by gamma-ray spectrometry to determine the activity concentrations of 226Ra, 232Th, and 40K. Gamma-spectrometry measurements were made using a hyperpure germanium detector surrounded with shielding material to reduce the background counting rate. The GammaVision-32 MCA emulation software was used for gamma-ray spectrum analysis and the TRUMP card of 2k as a MCA emulator. Conversion factors were used to calculate the dose to the population from outdoor exposure to terrestrial gamma rays. The measured activity concentration of 226Ra varies from 11 to 38 Bq kg(-1), the activity concentration of 232Th varies from 8 to 38 Bq kg(-1). The activity concentration of 40K is in the range 309-1,049 Bq kg(-1). The overall population mean outdoor terrestrial gamma dose rate is 44.94 nGy h(-1).     

Measurement of the natural radioactivity in building materials used in Ankara and assessment of external doses

A total of 183 samples of 20 different commonly used structural and covering building materials were collected from housing and other building construction sites and from suppliers in Ankara to measure the natural radioactivity due to the presence of (226)Ra, (232)Th and (40)K. The measurements were carried out using gamma-ray spectrometry with two HPGe detectors. The specific activities of the different building materials studied varied from 0.5 +/- 0.1 to 144.9 +/- 4.9 Bq kg(-1), 0.6 +/- 0.2 to 169.9 +/- 6.6 Bq kg(-1) and 2.0 +/- 0.1 to 1792.3 +/- 60.8 Bq kg(-1) for (226)Ra, (232)Th and (40)K, respectively. The results show that the lowest mean values of the specific activity of (226)Ra, (232)Th and (40)K are 0.8 +/- 0.5, 0.9 +/- 0.4 and 4.1 +/- 1.4 Bq kg(-1), respectively, measured in travertine tile while the highest mean values of the specific activity of the same radionuclides are 78.5 +/- 18.1 (ceramic wall tile), 77.4 +/- 53.0 (granite tile) and 923.4 +/- 161.0 (white brick), respectively. The radium equivalent activity (Ra(eq)), the gamma-index, the indoor absorbed dose rate and the corresponding annual effective dose were evaluated to assess the potential radiological hazard associated with these building materials. The mean values of the gamma-index and the estimated annual effective dose due to external gamma radiation inside the room for structural building materials ranged from 0.15 to 0.89 and 0.2 to 1.1 mSv, respectively. Applying criteria recently recommended for building materials in the literature, four materials meet the exemption annual dose criterion of 0.3 mSv, five materials meet the annual dose limit of 1 mSv and only one material slightly exceeds this limit. The mean values of the gamma-index for all building materials were lower than the upper limit of 1.     

Assessment of radionuclide contents in food in Hong Kong

Baseline values of concentrations of the natural radionuclides (238U, 226Ra, 228Ra/232Th, 210Pb) and artificial radionuclides (137Cs, 60Co) in food and drinks (tap water, milk, and water-based drinks) were determined by gamma spectroscopy. All food and drinks were found to contain detectable 40K contents: 0.1 to 160 Bq kg(-1) (fresh mass) for food and 0.006 to 61 Bq L(-1) for drinks. Most of the other natural radionuclides in solid food were found to have contents below the minimum detectable activities (MDA). More samples in the leafy vegetable, tomato, carrot and potato categories contained detectable amounts of 228Ra than the meat, cereal, and fish categories, with concentrations up to 1.2 Bq kg(-1) for the former categories and 0.35 Bq kg(-1) for the latter categories. The 238U and 226Ra radionuclides were detectable in most of the water-based drink samples (reaching 0.22 and 0.015 Bq kg(-1), respectively), and the 228Ra and 210Pb radionuclides were detectable in fewer water-based drink samples. The 137Cs contents in solid food were detectable in most of the solid food samples (reaching 0.59 Bq kg(-1)), but in drinks the 137Cs contents were very low (the maximum value is 0.23 Bq L(-1)) and normally lower than the MDA values. Nearly all the 60Co contents in food and drinks were below the MDA values and their contents were below those of 137Cs. The results indicate that drinks provide higher intake of natural radionuclides than solid food, but the solid food provides higher intake of 137Cs than drinks. From the measured concentrations, estimates were made on the consumption rate of radionuclides from food and drinks. The health effects due to the ingestion of the radionuclides were evaluated by calculating the committed effective dose. The committed effective dose due to the ingestion of natural radionuclides was estimated to be 69 microSv and 280 microSv for an adult male and female, respectively. The committed effective dose due to the ingestion of 137Cs and 60Co was estimated to be 0.5 microSv for both an adult male and female. The contributions from these two artificial radionuclides were less than those from the natural radionuclides by a factor of more than 100 and were also below the 1 mSv limit set in the new ICRP recommendations.     

某铁矿辐射职业危害因素调查

目的 调查某铁矿氡浓度、矿石放射性核素活度,估算矿工年有效剂量.方法 利用CR-39固体径迹探测器累积测量氡浓度:利用高纯锗γ谱仪分析矿石<'226>Ra、<'232>Th、<'40>K活度浓度.结果 矿井下氡浓度平均值约为207 Bq/m<'3>,估算所致矿工年有效剂量约为1.30 mSv;矿石中<'226>Ra、<'232>Th、<'40>K活度浓度分别为26.4、2.5和17.5 Bq/kg,估算所致矿工年有效剂量约为0.05 mSv/a.总计矿工年有效剂量为1.35 MSv/a.结论 该铁矿应考虑采取加大通风能力等措施来降低井下氡浓度,并对井下矿工按照职业照射人员的要求开展职业健康监护.     

Population dose distribution due to soil radioactivity concentration levels in 18 cities across Nigeria.

The natural radioactivity concentrations in soil samples collected from 186 locations across 18 cities in the six geo-political zones of Nigeria have been determined using gamma-ray spectrometry. Results show that the concentrations of (40)K, (238)U and (232)Th in the soil samples varied from below detection limits (BDL) to 1459.4 Bq kg(-1) with a mean of 73.3 +/- 18.5 Bq kg(-1) for (40)K, whereas for (238)U and (232)Th values varied from 9.2 to 113.7 Bq kg(-1) with a mean of 33.9 +/- 7.4 Bq kg(-1) and from BDL to 175.7 Bq kg(-1) with a mean of 12.4 +/- 3.1 Bq kg(-1), respectively. The average gamma absorbed dose rate in air across the cities ranged between 19 +/- 5 and 88 +/- 44 nGy h(-1) and the gross mean was 42.0 +/- 21.0 nGy h(-1). Using available population data in the study areas, about 2.84% of the population is exposed to a radiation dose rate of less than 20 nGy h(-1), 52.40% to a radiation dose rate between 20 and 30 nGy h(-1), 31% to a radiation dose rate between 30 and 60 nGy h(-1) and about 13.76% to dose rates greater than 60 nGy h(-1).     

Radioactive rock phosphate: the feed stock of phosphate fertilizers used in Pakistan

The existence of natural radioactivity in phosphate fertilizers originates from the rock phosphate that is used as a feed stock for the manufacturing of various types of phosphate fertilizers. Gamma ray activity mass concentrations have been determined in phosphate rock and fertilizer samples collected from different fertilizer manufacturing factories and suppliers in Pakistan. The technique of gamma ray spectrometry was applied using a HPGe (high purity germanium) gamma ray detector coupled with a personal computer (PC) based multichannel analyzer (MCA). The specific activity values of 40K, 226Ra, and 232Th were widely distributed in the rock and fertilizer samples. Activity mass concentrations of 238U (226Ra) in the rock phosphate from Jordan and Pakistan were 428 +/- 11 and 799 +/- 10 Bq kg(-1), respectively, and that in the triple-superphosphate fertilizer was 701 +/- 21 (-1), which was greater than the average values of 238U (226Ra) for other types of fertilizers under study. The concentrations of 40K and 232Th were of the order of background level on the Earth's crust. Chemical analysis for concentration of different constituents in rock phosphate was also carried out. The higher the concentrations of P2O5 and K2O were, the higher the specific activities of 226Ra and 40K were, respectively, in the rocks under study. The amount of radioactivity in the rock phosphate is a source of continuous exposure to radiation, which varies widely depending upon the origin and grade of rock; therefore, radiation dose rate has been estimated. The values of dose rate and other derived quantities were many folds larger than the limits specified for those quantities.     

Non-destructive determination of 224Ra, 226Ra and 228Ra concentrations in drinking water by gamma spectroscopy

The U.S. Environmental Protection Agency mandates that drinking water showing gross alpha-activity greater than 0.19 Bq L(-1) should be analyzed for radium, a known human carcinogen. The recommended testing methods are intricate and laborious. The method reported in this paper is a direct, non-destructive gamma-spectroscopic method for the determination of 224Ra, 226Ra, and 228Ra, the three radium isotopes of environmental concern in drinking water. Large-volume Marinelli beakers (4.1-L capacity), especially designed for measuring radioactive gases, in conjunction with a low-background, high-efficiency (131%) germanium detector were used in this work. It was first established that radon, the gaseous decay product of radium, and its progeny are quantitatively retained in this Marinelli beaker. The 224Ra, 226Ra, and 228Ra activity concentrations are determined from the equilibrium activities of their progeny: 212Pb, 214Pb (214Bi), and 228Ac; and the gamma-lines used in the analysis are 238.6, 351.9 (and 609.2), and 911.2 keV, respectively. The 224Ra activity is determined from the first 1,000-min measurement performed after expulsion of radon from the sample. The 226Ra activity is determined from the second, 2,400-min measurement, made 3 to 5 d later, and the 228Ra activity is determined from either the first or the second measurement, depending on its concentration level. The method's minimum detectable activities are 0.017 Bq L(-1), 0.020 Bq L(-1), and 0.027 Bq L(-1) for 224Ra, 226Ra, and 228Ra, respectively, when measured under radioactive equilibrium. These limits are well within the National Primary Drinking Water Regulations required limit of 0.037 Bq L(-1) for 226Ra and for 228Ra. The precision and accuracy of the method, evaluated using the U.S. Environmental Protection Agency and the Environmental Resource Associates' quality control samples, were found to be within acceptable limits.     

Radionuclide content of local and imported cements used in Egypt.

The activity concentrations of natural and artificial gamma-ray emitting radionuclides in local and imported cement have been investigated during the period from 2000 to 2003 using a 50% HPGe gamma-spectroscopy system. The total numbers of local and imported samples were 29 and 8, respectively. The results showed a low activity concentration of (137)Cs in both the local and imported samples. The only exception was found in one imported Portland cement (2.8 +/- 0.2 Bq kg(-1)) and one local blast furnace slag cement (1.9 +/- 0.3 Bq kg(-1)). The average activity concentrations of (226)Ra, (232)Th and (40)K in local cement were 33 +/- 17, 14 +/- 2.4 and 45 +/- 26 Bq kg(-1), respectively, whereas those in imported cement were 27 +/- 7, 8 +/- 7 and 134 +/- 22 Bq kg(-1), respectively. The results showed that blast furnace slag cement contains the highest level of natural radioactivity, whereas white cement contains the lowest levels. The measured activity concentrations of the detected radionuclides were compared with other measurements carried out in Egypt and elsewhere. Radium-equivalent activities were also calculated to assess the radiation hazards arising from using such material in the construction of dwellings. Generally, the radium-equivalents of the analysed samples were smaller than the guideline limit of 370 Bq kg(-1).     

Concentrations of 226Ra, 232Th, and 40K in the soils of Bangalore region, India

Several soil samples of Bangalore region were analyzed for the concentrations of Ra, Th, and K by gamma ray spectrometry. The concentration of Ra varied in the range 7.7-111.6 Bq kg with a mean value of 26.2 Bq kg, Th in the range 16.7-98.7 Bq kg with a mean of 53.1 Bq kg, and that of K in the range 151.8-1424.2 Bq kg with a mean of 635.1 Bq kg. The external gamma absorbed dose rates in air were also measured using a portable environmental radiation dosimeter, and the gamma dose rates were found to vary in the range 61.4-201.7 nGy h with a mean of 117.2 nGy h. These results along with the results of estimation of radium equivalent activity (Raeq), absorbed dose rate (D), annual effective dose rate, external hazard index (Hex), internal hazard index (Hin), and representative level index (Igamma) are presented in this paper. The results are also compared with the literature values reported for other regions of India as well as worldwide average values and discussed.     

Radium-226, 232Th, and 40K distribution in the environment of Kaiga of south west coast of India

Systematic studies on gamma radiation level and the distribution of natural radionuclides were carried out under a pre-operational survey for the establishment of baseline data on background radiation level and the distribution of radio-nuclides in the environment of Kaiga, in the south west coast of India, where a nuclear power reactor of 235 MWe has just been commissioned. The external gamma absorbed dose rates prevailing in the region were measured using a portable plastic scintillometer. Soil samples from 18 stations were collected from depth intervals of 0-5, 5-10, and 10-25 cm and analyzed for their 226Ra, 232Th, and 40K activity concentrations by gamma spectrometry employing a 90 cc PGT HpGe detector coupled to an EG&G ORTEC 8K multichannel analyzer. The activity of 226Ra was found to vary between 15.5-61.2 Bq kg(-1) with a mean value of 31.3 Bq kg(-1), that of 232Th varies between 11.4-41.9 Bq kg(-1) with a mean value of 27.5 Bq kg(-1) and of 40K between 78.3-254.8 Bq kg(-1) with a mean value of 159.9 Bq kg(-1) in 0-5 cm soil profiles of the region. The contributions of 238U, 232Th, and 40K to the total gamma absorbed dose rate were 39.9%, 40.7%, and 16.0%, respectively. The gamma absorbed dose rate in air estimated using the results of activity concentration of 226Ra, 232Th, and 40K are found to compare well with that of the direct measurement. The results of the study were compared with the literature values reported for other environs of the country as well as the world, and conclusions are drawn.     

The studies on radiological limits of color-glazed tiles used in home decoration

This study was carried out to lay down the radiological limits of color-glazed tiles used in home decoration. The activity concentrations of various end products and raw materials as well as processed materials were measured using gamma spectroscopy. 222Rn exhalation rates from the surface of color-glazed tiles were measured using charcoal canister method. Levels of exposure to alpha ray and beta ray from the surface of glazed tiles were measured by surface alpha and beta contaminant instrument. The results show a great difference between the radioactive levels of the surface glaze and the matrix of color-glazed tiles. The 222Rn exhalation rates from the surface of color-glazed tiles are in the range of 10(-3) - 10(-4) Bq m(-2) s(-1). The concentrations of some natural radionuclides in glaze exceed the exempt limits of International Basic Safety Standards for Protection against Ionizing Radiation Sources (IAEA 1997). The limits for color-glazed tiles were deduced according to these data and the theory of UNSCEAR (1993). The activity concentration of 226Ra (Bq kg(-1)) in the glaze of color-glazed tiles should be in the range of A(226Ra) < or = 1,000 (Bq kg(-1)), and, at the same time, the specific activity of the natural radionuclides (Bq kg(-1)) should be in the range of A(232Th)/230 + A(226Ra)/310 + A(40K)/3,500 < or = 1.     

Soil radionuclide concentrations and radiological assessment in and around a refining and petrochemical company in Warri, Niger Delta, Nigeria

Radioactivity measurements have been carried out using gamma-ray spectroscopy to determine the radionuclide concentrations in soil samples in the premises of the Warri Refining and Petrochemical Company located in the Niger Delta region of Nigeria and also in communities around it. The radionuclide contents of the crude oil and petroleum additives were also similarly determined. Results indicate that on the premises used by the company, the ranges of activity concentrations of (40)K, (226)Ra and (228)Th in the soil samples were 261.3-932.3 Bq kg(-1),<4.2-23.0 Bq kg(-1) and<5.1-10.2 Bq kg(-1), respectively. For the 13 villages studied, activity concentrations ranged from <17.2-766.3 Bq kg(-1),<4.2-104.7 Bq kg(-1) and<5.1-13.7 Bq kg(-1), respectively, for (40)K, (226)Ra and (228)Th. The lowest radionuclide concentrations were found in the crude oil relative to the petroleum additives. The highest outdoor effective dose rate obtained in the study was 47.5 microSv y(-1) for the villages and 35.2 microSv y(-1) within the company premises. These values are less than the world average outdoor value of 70 microSv y(-1) given by UNSCEAR. Overall, it can be concluded that the long duration of refining activities does not seem to have affected radionuclide concentrations in the environment. Measurements also showed that the observed radiation dose rates did not vary significantly from the previously determined Warri City outdoor gamma radiation dose rates, for which the probability of occurrence of any health effects of radiation was judged low. The measurements, therefore, are interpreted to represent baseline radiometric data for future reference and research in the area.     

Radioactive analysis of cement and its products collected from Shaanxi, China

This note presents a study of 226Ra, 232Th, and 40K in cement and its products manufactured in some areas of Shaanxi, China. The concentrations of 226Ra, 232Th, and 40K were 46.2, 28.4, and 137.4 Bq kg(-1), respectively, for cement brick; and 64.7, 48.7, and 161.3 Bq kg(-1), respectively, for cement plaster. The concentration of 226Ra, 232Th, and 40K in cement ranges from 34.7 to 68.3 Bq kg(-1) with a mean value of 56.5 Bq kg(-1), 18.5 to 51.7 Bq kg(-1) with a mean value of 36.5 Bq kg(-1), and 126.8 to 224.6 Bq kg(-1) with a mean value of 173.2 Bq kg(-1), respectively. The measured activity concentrations for these radionuclides were compared with the reported data of other countries. The radium equivalent activities (Raeq), external hazard index (Hex) and internal hazard index (Hin) associated with the radionuclides were calculated. The Raeq values of cement and cement products are lower than the limit of 370 Bq kg(-1), equivalent to a gamma dose of 1.5 mSv y(-1). The values of Hex and Hin are less than unity.     

A study on natural radioactivity in khewra salt mines, pakistan

The Khewra Salt Mines, the second largest salt mines in the world, are located 160 km south of Islamabad, the capital of Pakistan. Around 1000 workers are involved in the removal of salt from these mines. More than 40,000 visitors come annually to see the mines. The visitors and workers are directly exposed to the internal and external radiological hazards of radon and gamma rays in these mines. The general public is affected by the intake of the salt containing the naturally occurring radionuclides. Therefore the concentration of radon (²²²Rn) in the Khewra Salt Mines and activity concentrations of the naturally occurring radionuclides in the salt samples from these mines were measured. Both active and passive techniques were employed for the measurement of radon with Radon Alpha Detector (RAD-7) and SSNTD respectively. The concentration of ²²²Rn was 26 ± 4 Bq m^-3 measured by the active method while 43 ± 8 Bq m^-3 was measured by the passive method. The activity concentration of the radionuclides was measured using gamma ray spectrometry with HPGe detector. The mean activity of ⁴⁰K in salt samples was found to be 36 ± 20 Bq kg^-1 and the concentration of ²²⁶Ra and ²³²Th in the salt samples was below the detection limits. Gamma radiation hazard was assessed in terms of the external gamma dose from salt slabs and the rooms made of salt and the annual effective dose due to gamma radiation. The exposure to radon daughters, annual effective dose and excessive lifetime cancer risk due to radon in the mines were estimated. The mean annual effective dose due to an intake of ⁴⁰K from the salt was calculated as 20.0 ± 11.1 μSv, which is lower than the average annual effective dose rate of 0.29 mSv, received by the ingestion of natural radionuclides. Due to the low concentration values of primordial radionuclides in the salt and radon (²²²Rn) in the mines, a 'low level activity measurement laboratory' is suggested to be established in these mines.