|Year : 2013 | Volume
| Issue : 1 | Page : 27-31
Assessment of natural radioactivity and the associated hazards in some local cement types used in Yemen
Muhammed El-Azab Farid1, Abdallah Ibrahim Abd El-Mageed1, Emran Eisa Saleh2, M Mansour1, Anwar Khadher Mohammed3
1 Department of Physics, Faculty of Science, Assiut University, Egypt
2 Department of Physics, Faculty of Education, Toor El-Baha, Yemen
3 Faculty of Education, Yafea, Aden University, Yemen
|Date of Web Publication||21-Nov-2013|
Emran Eisa Saleh
Department of Physics, Faculty of Education, Toor El-Baha, Aden University
Source of Support: This study was carried out within the framework of a Ph D thesis conducted at Assuit University., Conflict of Interest: None
The cement industry is considered as one of the basic industries that plays a significant role in the national economy of developing countries. Activity concentration of 226 Ra, 232 Th, and 40 K in 38 samples of local cement types from different Yemeni factories has been measured by using the gamma ray spectrometry and their mean values were in the ranges (25.18-40.39 Bq/kg), (14.6-24.75 Bq/kg) and (160.01-596.38 Bq/kg), respectively. The average values obtained for 226 Ra, 232 Th, and 40 K activity concentration in different types of cement are lower than the corresponding global values reported in United Nation Scientific Committee on the Effect of Atomic Radiation publications. The obtained results show that the averages of radiation hazard parameters for all types of local cement in the current study are lower than the acceptable level of 370 Bq/kg for radium equivalent, 1 for level index (Iγ), the external hazard index ≤ 1 and (59 nGy/h) for absorbed dose rate. The measured activity concentrations for these natural radionuclides were compared to the reported data for other countries. Therefore, the natural radioactivity of cement samples under study was lower than the recommended values in the established standard and hence safe for use in building constructions.
Keywords: Cement, natural radioactivity, radiation hazards, γ-spectroscopy
|How to cite this article:|
Farid ME, Abd El-Mageed AI, Saleh EE, Mansour M, Mohammed AK. Assessment of natural radioactivity and the associated hazards in some local cement types used in Yemen. Radiat Prot Environ 2013;36:27-31
|How to cite this URL:|
Farid ME, Abd El-Mageed AI, Saleh EE, Mansour M, Mohammed AK. Assessment of natural radioactivity and the associated hazards in some local cement types used in Yemen. Radiat Prot Environ [serial online] 2013 [cited 2019 Jul 17];36:27-31. Available from: http://www.rpe.org.in/text.asp?2013/36/1/27/121821
| Introduction|| |
Man has been exposed to radiation from the natural environment throughout history. Natural radiation arises from three main sources; cosmic radiation, radiation from terrestrial source, and radioactivity in the body itself. The main source of terrestrial radiation ( 226 Ra, 232 Th, and 40 K) comes from rocks and soils of the earth's strata. 
As is known, cement is an important construction material of today's civilization. The radioactivity content of cement varies considerably depending upon the geological characteristics of the initial raw materials from which the cement is processed.  Cement is an important construction material for houses, buildings, and other purposes. It is used for making blocks and concrete, and for plastering the buildings made of bricks. The knowledge of natural radioactivity in building materials is then important for determining the amount of public exposure because people spend most of their time (about 80%) indoors.  Continuous exposure to even low-level radiation may adversely affect human health. Therefore, it is important to monitor the concentration of radionuclides in cement materials in different countries and to assess the radiation exposure to the people. 
The present study was undertaken to measure the concentration of natural 226 Ra, 232 Th, and 40 K in different cement samples, manufactured in Yemen using gamma-spectroscopy, and determination of the associated radiological hazard.
| Experimental Methods|| |
Sampling and sample preparation
A total of 38 samples of two types of local cement were collected for the measurement of radionuclide activity concentration from four cement factories of Yemen, 32 Portland cement (PC) and 6 sulfate resistant cement (S.R.C). For PC samples were collected from Al Wahda factory (eight samples), Al Wataniya factory (eight samples), and Al Barh factory (eight samples) and from Al Mukalla factory (eight samples). For S.R.C samples were taken from Al Barh factor (six simples). These samples were obtained from suppliers and/or factories. Typically, 175 cm 3 of each sample was placed in plastic containers dimensions of 55 mm in diameter and 75 mm height. The samples were weighed and stored for a minimum period of 1 month to allow daughter products to come into radioactive equilibrium with their parents 226 Ra and 232 Th.
Each sample was measured with a gamma ray spectrometer consisting of a NaI (Tl) setup and multichannel analyzer 8192 channel, with the following specification: Resolution full width maximum half at 661.6 keV 137 Cs (i.e., it is about 40 keV) and about 60 keV for the photopeak of 60 Co at 1332 keV- relative efficiency at 661.6 keV 137 Cs is 6% and relative efficiency at 1332 keV 60 Co is 7.5%. The detector is shielded in a chamber of two layers starting with stainless steel (10 mm thick) and led (30 mm thick). This shield serves to reduce different background radioactivity.
Appropriate radionuclides must be selected for use as in efficiency calibration. Solutions of certified mixed radionuclides with reasonably long half-lives are available from several reputable suppliers. Accurate absolute gamma ray emission rates should be stated in the certificates supplied with the standards. The spectrometer was calibrated for efficiency and energy using the multi-nuclide standard solution (QCY 48) PTB (Germany) (a mixed source containing 241 Am, 57 Co, 60 Co, 85 Sr, 88 Y, 109 Cd, 137 Cs, 139 Ce, and 203 Hg). The standard source peaked in the same geometry as that used for measured samples. For calibration, the standard source is placed above the detector, and the measurement started. [Figure 1] shows the gamma ray spectrum of the standard source for cement of NaI (Tl) detector for 2 h is the time of counts. The dependence of the efficiency on the radiation energy was determined at 0.0 mm sample-detector distance. The absolute efficiency of the NaI (Tl) detector was determined. [Figure 2] shows the full energy peak efficiency as a function of gamma ray energy. It can be noticed that the detector efficiency decreases continuously with energy.
|Figure 1: Gamma ray spectrum of the standard source for cement of NaI (Tl) detector for 2 h is the time of counts|
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|Figure 2: Full energy peak efficiency as a function of gamma ray energy for NaI (Tl) detector for cement in bottle (cylindrical plastic containers 175 cm3)|
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Each sample was placed in plastic containers of the same size as that of the multi-element standard. The spectra were either evaluated with the computer software program Maestro (EG and G ORTEC) or manually with the use of a spread sheet (Microsoft Excel) to calculate the natural radioactivity. 226 Ra activity of the samples was determined via its daughters ( 214 Pb and 214 Bi) through the intensity of the 351.93 keV, for 214 Pb and 609.31,1120 and 1764.49 keV, for 214 Bi gamma-line. 232 Th activity of the sample was determined from the daughters ( 228 Ac), ( 212 Pb) and ( 208 Tl) through the intensity of 911.2 keV gamma-line for ( 228 Ac), ( 212 Pb) emissions at 238.63 keV and ( 208 Tl) emission at 2614 keV gamma-line. 40 K activity was determined from the 1460.7 keV emission gamma-line. The samples were counted for 12-24 h depending on the concentration of the radionuclides.
The activity concentrations for the natural radionuclides in the measured samples were computed using the following relation. 
Where NP is the number of counts in given peak area corrected for background peaks of a peak at energy E, ε (Eγ) the detection efficiency at energy E, t c is the counting lifetime, Iγ(Eγ) the number of gamma per disintegration of this nuclide for a transition at energy E, and M the mass in kg of the measured sample.
Calculation of the radiological parameters
| Results and Discussion|| |
The activities concentration (Bq/kg) of 226 Ra, 232 Th and 40 K have been measured in two types of local cement from four cement factories in Yemen. [Table 1] presents the ranges and mean values of activity of each radionuclide and [Figure 3] compares the mean values of natural radionuclide concentrations of local cement in Yemen. As it is seen from [Table 1] the highest mean values of 226 Ra and 232 Th were (40.4 ± 9.9) and (24.75 ± 5.5) Bq/kg in Al Wataniya (PC) while the Al Barh (S.P.C) samples were found to have the highest value of 40 K concentration, (596.38 ± 33.5) Bq/kg. According to the results of [Table 1], the maximum concentrations were found for 40 K in all types of local cement. The lowest mean values of 232 Th and 40 K were in Al Mukalla (PC) samples (18.77 ± 4.7), (160.1 ± 10.8) Bq/kg and lowest mean values of 226 Ra was found for Al Barh (PC) samples (25.18 ± 7.54) Bq/kg. The activities concentration of 226 Ra, 232 Th and 40 K in all the investigated samples were found to be lower than the world average values of 50, 50 and 500 respectively.  The only exception was the activity concentration of 40 K in Al Barh S.R.C.
|Figure 3: Mean values of natural radionuclide concentration of local cement in Yemen|
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|Table 1: Range and mean values activity concentration of 226Ra, 232Th and 40K (Bq/kg) for different types of local cement from Yemen|
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A comparison between the mean values of radioactive materials in Yemen and values in other countries is shown in [Table 2]. As can be seen from [Table 2], 226 Ra and 232 Th concentration values from the present work are match that reported by El-Taher et al.  in Egypt, Amrani and Tahatat.  in Algeria, Khan and Khan.  in Pakistan and by Kumar et al.  in India and lower than reported by Kamal Ali  in Iraq, Beretka and Matthew.  in Australia and Lu et al.  in China and higher than the values reported by Mehdizadeh et al.  in Iran, Sam and Abbas.  in Sudan and Brνgido Flores et al.  in Cuba. On the other hand, 40 K concentration values in the present study except samples from Al-Mukalla are in the same range as that reported by Brígido Flores et al.  , Kumar et al.  , Amrani and Tahatat.  and Sam and Abbas.  in India, Algeria and Sudan respectively, and higher than in Literature (El-Taher et al.  ; Mehdizadeh et al.  ; Beretka and Matthew et al.  ; Ali  ; Lu et al.  ; Khan et al.  ).
|Table 2: Comparison between the activity concentration of local cement samples from Yemen with that of other country|
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The estimated mean values of Ra eq activities for all types of local cement samples are summarized in [Table 3]. The highest mean value of R eq is estimated for Al Wataniya PC samples, 108.5 Bq/kg, which is below the recommended limit of 370 Bq/kg. 
Mean value of gamma dose rate in the air at the distance of 1 m from the ground were estimated for different types of local cement samples. As can be seen from [Table 3], the maximum gamma dose rate was 51.1 nGy/h in Al Wataniya (PC) while the minimum value was found for Al Mukalla (PC) about 31.5 nGy/h.
|Table 3: The average values of radiation parameter for different types of local cement from Yemen|
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The values of external hazard H ex along with gamma indexes Iγ is also shown in [Table 3]. As can be seen, the maximum value of H ex was found in Al Barh (S.R.C) 0.32. The highest values of Iγ is 0.42 was found in Al Wataniya (PC). All the local cement types in the current study have H ex and Iγ values lower than recommended limit of 1. 
| Conclusion|| |
The gamma spectroscopy method was used for assessment of the 226 Ra and 232 Th and 40 K in common local cement in Yemen. The lowest mean values of the 226 Ra, 232 Th and 40 K were found in Al Barh (PC), Al Wahda (PC) and Al Mukalla (PC) respectively, while the Al Barh (S.R.C) contained the highest value of 40 K and Al Wataniya (PC) contained the highest of 226 Ra and 232 Th. The values of dose rate at a distance of 1 m in air (D) were calculated using the activity concentration of radionuclides. The maximum value of dose rate (51.1 nGy/h) was found in Al Watania samples. The Ra eq activities, H ex and gamma index (Iγ) obtained were below recommended values. Therefore, the use of these types of local cement in the construction of buildings is safe for people.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]