Assessment of natural radioactivity levels and radiation hazards due to cement industry 土木专英论文.doc
《Assessment of natural radioactivity levels and radiation hazards due to cement industry 土木专英论文.doc》由会员分享,可在线阅读,更多相关《Assessment of natural radioactivity levels and radiation hazards due to cement industry 土木专英论文.doc(10页珍藏版)》请在三一文库上搜索。
1、Assessment of natural radioactivity levels and radiation hazards due to cement industryAbstractThe cement industry is considered as one of the basic industries that plays an important role in the national economy of developing countries. Activity concentrations of 226Ra, 232Th and 40K in Assiut ceme
2、nt and other local cement types from different Egyptian factories has been measured by using -ray spectrometry. From the measured -ray spectra, specific activities were determined. The measured activity concentrations for these natural radionuclides were compared with the reported data for other cou
3、ntries. The average values obtained for 226Ra, 232Th and 40K activity concentration in different types of cement are lower than the corresponding global values reported in UNSCEAR publications. The manufacturing operation reduces the radiation hazard parameters. Cement does not pose a significant ra
4、diological hazard when used for construction of buildings.Keywords: Natural radioactivity; Cement; Raw materials; Radiation hazards1. IntroductionThe need for cement is so great. That it considered a basic industry. Workers exposed to cement or its raw materials for a long time especially in mines a
5、nd at manufacturing sites as well as people, that spend about 80% of their time inside offices and homes (Mollah et al., 1986; Paredes et al., 1987) result in exposure to cement or its raw materials being necessary reality so we should know the radioactivity for cement and its raw material. There ar
6、e many types of cements according to the chemical composition and hydraulic properties for each one. Portland cement is the most prevalent one. The contents of 226Ra, 232Th and 40K in raw and processed materials can vary considerably depending on their geological source and geochemical characteristi
7、cs. Thus, the knowledge of radioactivity in these materials is important to estimate the radiological hazards on human health. The radiological impact from the natural radioactivity is due to radiation exposure of the body by gamma-rays and irradiation of lung tissues from inhalation of radon and it
8、s progeny (Papastefanou et al., 1988). From the natural risk point of view, it is necessary to know the dose limits of public exposure and to measure the natural environmental radiation level provided by ground, air, water, foods, building interiors, etc., to estimate human exposure to natural radia
9、tion sources (UNSCEAR, 1988). Low level gamma-ray spectrometry is suitable for both qualitative and quantitative determinations of gamma-ray-emitting nuclides in the environment (IAEA, 1989).The concentration of radio-elements in building materials and its components are important in assessing popul
10、ation exposures, as most individuals spend 80% of their time indoors. The average indoor absorbed dose rate in air from terrestrial sources of radioactivity is estimated to be 70nGyh1. Indoors elevated external dose rates may arise from high activities of radionuclides in building materials (Zikovsk
11、y and Kennedy, 1992). Great attention has been paid to determining radionuclide concentrations in building materials in many countries (Amrani and Tahtat, 2001; Rizzo et al., 2001; Kumar et al., 2003; Tzortzis et al., 2003). But information about the radioactivity of these materials in Egypt is limi
12、ted. Knowledge of the occurrance and concentration of natural radioactivity in such important materials is essential for checking its quality in general and knowing its effect on the environment surrounding the cement producing factories in particular.Because of the global demand for cement as a bui
13、lding material, the present study aims to: (1) Assess natural radioactivity (226Ra, 232Th and 40K) in raw and final products used in the Assiut cement factory and other local factories in Egypt. (2) Calculate the radiological parameters (radium equivalent activity Raeq, level index Ir, external haza
14、rd index Hex and absorbed dose rate) which is related to the external -dose rate.The results of concentration levels and radiation equivalent activities are compared with similar studies carried out in other countries.2. Experimental technique2.1. Sampling and sample preparationFifty seven samples o
15、f raw materials and final products used in the Assiut cement factories were collected for investigation. Twenty five samples of raw materials were taken from (Limestone, Clay, Slag, Iron oxide, gypsum) which are all the raw material used in cement industry, 20 samples of final products were taken fr
16、om Assiut cement (Portland, El-Mohands, White, and Sulphate resistant cement (S.R.C). For comparison with products from other factories, 8 samples were taken from the ordinary Portland cement from (Helwan, Qena, El-kawmya, Torra) and 4 samples were taken of white cement (Sinai and Helwan). Each samp
17、le, about 1-kg in weight was washed in distilled water and dried in an oven at about 110C to ensure that moisture is completely removed, The samples were crushed, homogenized, and sieved through a 200mesh, which is the optimum size to be enriched in heavy minerals. Weighted samples were placed in a
18、polyethylene beaker, of 350-cm3 volume. The beakers were completely sealed for 4 weeks to reach secular equilibrium where the rate of decay of the radon daughters becomes equal to that of the parent. This step is necessary to ensure that radon gas is confined within the volume and the daughters will
19、 also remain in the sample.2.2. Instrumentation and calibrationActivity measurements were performed by gamma ray spectrometry, employing a 33scintillation detector. The hermetically sealed assembly with a NaI(Tl) crystal is coupled to a PC-MCA (Canberra Accuspes). Resolution 7.5% specified at the 66
20、2keV peak of 137Cs. To reduce gamma ray background a cylindrical lead shield (100mm thick) with a fixed bottom and movable cover shielded the detector. The lead shield contained an inner concentric cylinder of copper (0.3mm thick) to absorb lead X-rays. In order to determine the background distribut
21、ion in the environment around the detector, an empty sealed beaker was counted in the same manner and in the same geometry as the samples. The measurement time of activity or background was 43200s. The background spectra were used to correct the net peak area of gamma rays of measured isotopes. A de
22、dicated software program (Genie 2000 from Canberra) analyzed each measured -ray spectrum.3. ConclusionThe natural radionuclides 226Ra, 232Th and 40K were measured for raw materials and final products used in the Assiut cement factory in Upper Egypt and compared with the results in other countries. T
23、he activity concentration of 40K is lower than all corresponding values in other countries. The activity concentration of 226Ra and 232Th for all measured samples of Portland cement are comparable with the corresponding values of other countries. The obtained results show that the averages of radiat
24、ion hazard parameters for Assiut cement factory are lower than the acceptable level 370Bqkg1 for radium equivalent Raeq, 1 for level index Ir, the external hazard index Hex 1 and 59 (nGyh1) for absorbed dose rate. The manufacturing operation reduces the radiation hazard parameters. So cement product
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- Assessment of natural radioactivity levels and radiation hazards due to cement industry 土木专英论文 土木 论文
链接地址:https://www.31doc.com/p-3901036.html