【正文】 uildings .generally of reinforced concrete or metal construction ,a factory can be given a “shed ”type ridge roof ,incorporating windows facing north so as to give evenly distributed natural lighting without sunglare .Assessment of natural radioactivity levels and radiation hazards due to cement industry Abstract The 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 cement and other local cement types from different Egyptian factories has been measured by using γray spectrometry. From the measured γray spectra, specific activities were determined. The measured activity concentrations for these natural radionuclides were pared with the reported data for other countries. 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 radiological hazard when used for construction of buildings. 1. Introduction The 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 and 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 are many types of cements according to the chemical position 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 characteristics. 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 濰坊學(xué)院本科畢業(yè)論文 3 body by gammarays and irradiation of lung tissues from inhalation of radon and its 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 radiation sources (UNSCEAR, 1988). Low level gammaray spectrometry is suitable for both qualitative and quantitative determinations of gammarayemitting nuclides in the environment (IAEA, 1989). The concentration of radioelements in building materials and its ponents are important in assessing population 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 70 nGy h?1. Indoors elevated external dose rates may arise from high activities of radionuclides in building materials (Zikovsky and Kennedy, 1992). Great attention has been paid to determining radionuclide concentrations in building materials in many countries (Amrani and Tahtat, 2020。 Kumar et al., 2020。C to ensure that moisture is pletely removed, The samples were crushed, homogenized, and sieved through a 200 mesh, which is the optimum size to be enriched in heavy minerals. Weighted samples were placed in a polyethylene beaker, of 350cm3 volume. The beakers were pletely sealed for 4 weeks to reach secular equilibrium where the rate of decay of the radon daughters bees equal to that of the parent. This step is necessary to ensure that radon gas is confined within the volume and the daughters will also remain in the sample. . Instrumentation and calibration 濰坊學(xué)院本科畢業(yè)論文 4 Activity measurements were performed by gamma ray spectrometry, employing a 3″3″scintillation detector. The hermetically sealed assembly with a NaI(Tl) crystal is coupled to a PCMCA (Canberra Accuspes). Resolution % specified at the 662 keV peak of 137Cs. To reduce gamma ray background a cylindrical lead shield (100 mm thick) with a fixed bottom and movable cover shielded the detector. The lead shield contained an inner concentric cylinder of copper ( mm thick) to absorb lead Xrays. In order to determine the background distribution 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 43 200 s. The background spectra were used to correct the peak area of gamma rays of measured isotopes. A dedicated software program (Genie 2020 from Canberra) analyzed each measured γray spectrum. 3. Conclusion The natural radionuclides 226Ra, 232Th and 40K were measured for raw materials and final products used in the Assiut cement factory in Upper Egypt and pared with the results in other countries. The 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 parable with the corresponding values of other countries. The obtained results show that the averages of radiation hazard parameters for Assiut cement factory are lower than the acceptable level 370 Bq kg?1 for radium equivalent Raeq, 1 for level index Iγr, the external hazard index Hex ≤1 and 59 (nGy h?1) for absorbed dose rate. The manufacturing operation reduces the radiation hazard parameters. So cement products do not pose a significant radiological hazard when used for building construction. The radi