El Afifi E M, Hilal M A, Attallah M F, El-Reefy S A
Department of Analytical and Environmental Control, Hot Laboratories and Waste Management Center (HLWMC), Atomic Energy Authority, Post Office No. 13759, Abu Zabaal, Cairo, Egypt.
J Environ Radioact. 2009 May;100(5):407-12. doi: 10.1016/j.jenvrad.2009.01.005. Epub 2009 Mar 9.
The present work is directed to characterize the phosphogypsum (PG) wastes associated with phosphoric acid produced by the wet process in industrial facility for the production of fertilizers and chemicals in Egypt. The PG waste samples were characterized in terms of spectroscopic analysis (X-ray diffraction, X-ray fluorescence, IR spectra) and radiometric analysis (gamma- and alpha-measurements). The gamma-ray measurements showed that the average activity concentrations are 140+/-12.6, 459+/-36.7, 323+/-28.4, 8.3+/-0.76 and 64.3+/-4.1 Bq/kg for U-238, Ra-226, Pb-210, Th-232 and K-40, respectively. The alpha-particle measurements of uranium isotopes showed that the average activity concentrations of U-238, U-235 and U-234 were 153+/-9.8, 7+/-0.38, 152+/-10.4 Bq/kg, respectively. The average radiochemical recovery (%) of the destructive alpha-particle measurements is approximately 70% with a resolution (FWHM) of approximately 30 keV. Activity ratios of U-238/Ra-226 and U-238/Pb-210 were less than unity (i.e., <1) and equal to 0.31+/-0.02 and 0.47+/-0.16, respectively. The isotopic ratios of U-238/U-235 and U-238/U-234 (in PG and PR samples) were close to the normal values of approximately 21.7 and approximately 1, respectively and are not affected by the wet processing of phosphate rock (PR). The obtained results of PG waste samples were compared with phosphate rock (PR) samples. The radiation hazard indices are namely, radium activity index (Ra-Eq>370 Bq/kg), total absorbed gamma dose rate (D(gamma r)>5 nGy/h) and radon emanation fraction (Rn-EF>20%). Uncertainty of the sample counting was 95% confidence level of sigma. The results indicated the necessity to find suitable routes to decrease and/or redistribute the radionuclide of environmental interest (i.e., Ra-226) in PG wastes, consequently to reduce its radiation impacts in the surrounding environment.
本研究旨在对埃及化肥和化工生产工业设施中湿法生产磷酸所产生的磷石膏(PG)废料进行特性分析。通过光谱分析(X射线衍射、X射线荧光、红外光谱)和辐射分析(伽马和阿尔法测量)对PG废料样本进行了特性分析。伽马射线测量结果表明,U-238、Ra-226、Pb-210、Th-232和K-40的平均活度浓度分别为140±12.6、459±36.7、323±28.4、8.3±0.76和64.3±4.1 Bq/kg。铀同位素的阿尔法粒子测量结果表明,U-238、U-235和U-234的平均活度浓度分别为153±9.8、7±0.38、152±10.4 Bq/kg。破坏性阿尔法粒子测量的平均放射化学回收率(%)约为70%,分辨率(半高宽)约为30 keV。U-238/Ra-226和U-238/Pb-210的活度比小于1(即<1),分别为0.31±0.02和0.47±0.16。U-238/U-235和U-238/U-234(在PG和PR样本中)的同位素比分别接近约21.7和约1的正常值,且不受磷矿石(PR)湿法加工的影响。将PG废料样本的所得结果与磷矿石(PR)样本进行了比较。辐射危害指数分别为镭活度指数(Ra-Eq>370 Bq/kg)、总吸收伽马剂量率(D(γr)>5 nGy/h)和氡析出率(Rn-EF>20%)。样本计数的不确定度为95%置信水平的西格玛。结果表明有必要找到合适的途径来减少和/或重新分配PG废料中具有环境意义的放射性核素(即Ra-226),从而降低其对周围环境的辐射影响。