低中放处置场环境影响评价中~(90)Sr分配系数的选取
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摘要
放射性固体废物处置的基本安全目标是保护人类和环境免受电离辐射的有害影响。开展放射性固体废物处置场环境影响评价可以量化对人体健康和环境潜在影响。放射性核素分配系数是反映放射性核素在处置场周边土壤介质中迁移的关键参数,对环境影响评价结果的影响显著。不同核素分配系数试验测量方法的实验周期、经济成本以及结果精确度等方面差别很大。从工程角度考虑,如测量结果相差不大,则应优先选择实验周期短、费用低的方法进行分配系数测量。~(90)Sr是拟近地表处置的放射性固体废物中具有代表性的裂变核素之一。采用静态实验和动态实验方法对~(90)Sr在我国北方几种典型土壤(砂土、粘土和黄土)包气带中的迁移进行了研究,分析了不同试验方法测量得到的~(90)Sr分配系数的差异。结果表明:对~(90)Sr的吸附能力,粘土最强,黄土次之,砂土最弱;对于低中放处置场地下水核素迁移模拟,~(90)Sr在粘土和黄土中采用平衡吸附模式或非平衡吸附模式模拟结果差别不大;而采用非平衡模式模拟砂土中~(90)Sr的迁移更为恰当;在低中放处置场环境影响评价中,对于砂土介质,~(90)Sr分配系数的测量应优先选择动态实验法,对于黄土和粘土则可采用静态吸附法。
The fundamental safety objective for the disposal of radioactive solid waste is to protect humans and the environment from harmful effects of ionizing radiation. The environmental impact assessment of radioactive solid waste disposal sites can quantify the potential impacts on human health and the environment. The radionuclide distribution coefficient is a key parameter which is used to characterize the migration of radionuclides in soil media around the disposal site and has a significant impact on the results of environmental impact assessment. The experimental cycle,economic cost,and accuracy of results of different nuclide distribution coefficient test methods vary widely. From the engineering point of view,the method with short experimental period and low cost should be chosen as the priority,in the premise that the measurement results do not vary much.~(90)Sr is one of the representative radionuclides in low and intermediate level radioactive solid waste to be treated near the surface. The static experiments and dynamical experimental methods were conducted to study the migration rules of~(90)Sr in the vadose zone of several typical soils( sandy soil,clay,and loess) in arid area of Northern China. The differences of~(90)Sr distribution coefficients measured by different test methods were analysed. The results show that the clay soil has the strongest adsorption capacity of ~(90)Sr,followed by loess,and the sandy soil was the weakest. For the simulation of groundwater nuclide migration of ~(90)Sr in the low-middle discharge disposal field,the simulated results are not much different using equilibrium adsorption model or non-equilibrium adsorption model for clay and loess,while it is more suitable to use nonequilibrium adsorption model to simulate ~(90)Sr migration in sandy soil. In terms of environmental impact assessment of low and intermediate level disposal sites,the dynamic column experimental method should be given priority for the measurement of ~(90)Sr distribution coefficient for the sandy soil,while the static batch experimental method can be used for loess and clay.
The fundamental safety objective for the disposal of radioactive solid waste is to protect humans and the environment from harmful effects of ionizing radiation. The environmental impact assessment of radioactive solid waste disposal sites can quantify the potential impacts on human health and the environment. The radionuclide distribution coefficient is a key parameter which is used to characterize the migration of radionuclides in soil media around the disposal site and has a significant impact on the results of environmental impact assessment. The experimental cycle,economic cost,and accuracy of results of different nuclide distribution coefficient test methods vary widely. From the engineering point of view,the method with short experimental period and low cost should be chosen as the priority,in the premise that the measurement results do not vary much.~(90)Sr is one of the representative radionuclides in low and intermediate level radioactive solid waste to be treated near the surface. The static experiments and dynamical experimental methods were conducted to study the migration rules of~(90)Sr in the vadose zone of several typical soils( sandy soil,clay,and loess) in arid area of Northern China. The differences of~(90)Sr distribution coefficients measured by different test methods were analysed. The results show that the clay soil has the strongest adsorption capacity of ~(90)Sr,followed by loess,and the sandy soil was the weakest. For the simulation of groundwater nuclide migration of ~(90)Sr in the low-middle discharge disposal field,the simulated results are not much different using equilibrium adsorption model or non-equilibrium adsorption model for clay and loess,while it is more suitable to use nonequilibrium adsorption model to simulate ~(90)Sr migration in sandy soil. In terms of environmental impact assessment of low and intermediate level disposal sites,the dynamic column experimental method should be given priority for the measurement of ~(90)Sr distribution coefficient for the sandy soil,while the static batch experimental method can be used for loess and clay.
引文
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[2]李洋,赵杨军,陈海龙,等.低中放处置场环境评价参数灵敏度分析[J].环境科学与管理,2017,42(5):175-179.
[3]李洋,赵杨军,杨洁,等.中国低中放近地表处置场环境评价方法研究[J].环境科学与管理,2017,42(1):190-194.
[4]李书绅,王志明,等.核素在非饱和黄土中迁移研究[M].北京:原子能出版社,2003.
[5]郭择德,倪世伟,李书绅,等.包气带中核素迁移模拟实验的设计和方法[J].辐射防护,2003,23(3):163-170.
[6]杨月娥,李洋,潘伟,等.稳定元素Sr在土柱中的迁移[J].原子能科学技术,2006,40(3):292-296.
[7]朱君,邓安嫦,石云峰,等.不同质地土壤对核素Sr-90阻滞及迁移的影响[J].安全与环境学报,2018,18(1):330-334.
[8]杨勇,苑国琪,张东,等.90Sr、137Cs在某种包气带土壤中的迁移研究[J].四川环境,2004,23(3):85-89.
[9]李洋,朱君,康晶,等.90Sr在干旱地区包气带砂土中的迁移研究[J].环境科学与管理,2017,34(6):40-42.
[10]李洋,张艾明,赵杨军,等.90Sr在干旱地区包气带粘土中的迁移[J].中国科技成果,2017,(12):40-42.
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