集成缓冲材料对锶的长期阻滞效应
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摘要
缓冲材料作为高放废物处置库中多重屏障体系的最后一道人工屏障,其对放射性核素的阻滞性能将直接影响到处置库的长期稳定性和安全性。以具有低渗透性和良好的膨胀自愈性的膨润土作为集成缓冲材料的基材,以沸石和黄铁矿作为矿物添加剂,三者按照质量比为63∶27∶10均匀混合构成集成缓冲材料B7ZP,并采用恒定源扩散实验分析了锶在干密度为1.70g/cm~3试样中的扩散特性,结果表明,B7ZP缓冲材料对锶具有良好的阻滞性能,其表观扩散系数为3.30×10~(-12) m~2/s。同时,以多孔介质污染物迁移理论为依据,建立了锶在集成缓冲材料B7ZP中迁移的对流-弥散-吸附多场耦合方程,并应用Matlab软件分析了不同的时间尺度、渗流速率、表观扩散系数和阻滞因子等因素下集成缓冲材料B7ZP对锶的长期阻滞性能,为高放废物处置库的缓冲材料设计和长期阻滞性能评价提供科学依据。
Buffer material was the last artificial barrier of high-level radioactive waste repository,and its retardation capability to radioactive nuclides would directly affect the security and stability of the repository system.Bentonite was a suitable mineral,which can be used to build an integrated buffer material because of low hydraulic conductivity,good swelling and sealing properties,plasticity and high sorption capacity.Bentonite-zeolite-pyrite type integrated buffer material was constituted by the bentonite-zeolite-pyrite weight ratio was 63∶27∶10(abbreviated as B_7ZP),that zeolite and pyrite were chosen as mineral addi-tives.Then constant source diffusion experiment was carried out to investigate strontium diffusibility in B_7ZP with initial dry density of 1.70g/cm~3.The experimental results indicate that B_7ZP has good retardation capability for strontium,and the apparent diffusion coefficient of strontium is 3.3×10~(-12) m~2/s,smaller in B_7ZP than in pure bentonite.The convection-diffusion-adsorption multi field coupling model for strontium migration was established based on the theory of porous media pollutant migration.MATLAB software was used to analyze migration distance of strontium in B_7ZP under the condition of different time scales,seepage velocity,apparent diffusion coefficient and retardation factor.These research results can supply reference for usage of barrier materials and assessment of long-term retardation capability.
Buffer material was the last artificial barrier of high-level radioactive waste repository,and its retardation capability to radioactive nuclides would directly affect the security and stability of the repository system.Bentonite was a suitable mineral,which can be used to build an integrated buffer material because of low hydraulic conductivity,good swelling and sealing properties,plasticity and high sorption capacity.Bentonite-zeolite-pyrite type integrated buffer material was constituted by the bentonite-zeolite-pyrite weight ratio was 63∶27∶10(abbreviated as B_7ZP),that zeolite and pyrite were chosen as mineral addi-tives.Then constant source diffusion experiment was carried out to investigate strontium diffusibility in B_7ZP with initial dry density of 1.70g/cm~3.The experimental results indicate that B_7ZP has good retardation capability for strontium,and the apparent diffusion coefficient of strontium is 3.3×10~(-12) m~2/s,smaller in B_7ZP than in pure bentonite.The convection-diffusion-adsorption multi field coupling model for strontium migration was established based on the theory of porous media pollutant migration.MATLAB software was used to analyze migration distance of strontium in B_7ZP under the condition of different time scales,seepage velocity,apparent diffusion coefficient and retardation factor.These research results can supply reference for usage of barrier materials and assessment of long-term retardation capability.
引文
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[21]刘艳,王青海,陈洁,等.锶、铯在压实柯尔碱膨润土中的扩散行为[J].环境化学,2013,32(12):2250-2255.
[22]Neretnieks I.Diffusivities of some consitutents in compacted wet bentonite clay and the impact on radionuclide migration in the buffer[J].Nucl Technol,1985,71(2):458-470.
[23]张石升.核环境学基础[M].北京:原子能出版社,1999.
[24]仵彦卿.多孔介质污染物迁移动力学[M].上海:上海交通大学出版社,2007.
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[26]贺勇.膨润土对重金属离子的阻滞特性研究[D].长沙:长沙理工大学,2012.
[27]Cho W J,Lee J O.Hydraulic conductivity of compacted bentonite-sand mixture for potential backfill material for highv-level radioactive waste repository[J].Journal of the Korean Nuclear Society,2000,32(5):495-503.
[28]Wang X K,Du J Z,Tao Z Y,et al.Evaluation of Eu(Ⅲ)migration in compacted bentonite[J].J Radioanal Nucl Chem,2004,260(1):69-73.
[29]王榕树,冯为.放射性核素在地质介质中的迁移研究[J].核化学与放射化学,1994,16(2):117-121.
[30]谢水波,陈泽昂,张晓健,等.宏观弥散度和阻滞系数对地下水中核素迁移模拟的影响[J].湖南大学学报(自然科学版),2007,34(5):78-82.
[2]Nielsen S P.The biological role of strontium[J].Bone,2004,35(3):583-588.
[3]王驹.世界放射性废物地质处置[M].北京:原子能出版社,1999.
[4]Takashi M,Rodney C.Scientific basis for nuclear waste managementⅩⅧ(Part I)[C].California:Materials Research Society,1995.
[5]Pusch R.Highly compacted sodium bentonite for isolating rock-deposited radioactive waste products[J].Nucl Technol,1979,45(2):153-157.
[6]Motsi T,Rowson N A,Simmons M J H.Adsorption of heavy metals from acid mine drainage by natural zeolite[J].International Journal of Mineral Processing,2009,92(1-2):42-48.
[7]张虎元,梁健,刘吉胜,等.混合型缓冲回填材料压实性能研究[J].岩石力学与工程学报,2009,28(12):2585-2592.
[8]Salem A,Akbari R.Removal of lead from solution by combination of natural zeolite-kaolin-bentonite as a new low-cost adsorbent[J].Chem Eng J,2011,174(2-3):619-628.
[9]Hodges F N,Westsik J H Jr,Bray L A.Development of a backfill for confinement of high level nuclear waste[C]∥Scientific Basis for Nuclear Waste Manage 6th Symp Proc,Material Research Society,1982:641.
[10]崔玉军.高放核废物地质处置中工程屏障研究新进展[C]∥第260次香山科学会议“高放废物地质处置”会议论文集.北京:香山科学会议第206次学术讨论会筹备组,2005:166-173.
[11]叶为民,王琼,陈永贵,等.缓冲/回填材料:砂-膨润土混合物研究进展[J].铀矿地质,2010,26(2):95-100.
[12]陈永贵,叶为民,王琼,等.砂-膨润土混合屏障材料渗透性影响因素研究[J].工程地质学报,2010,18(3):357-362.
[13]崔素丽,张虎元,刘吉胜,等.混合型缓冲回填材料膨胀变形试验研究[J].岩土力学,2011,32(3):684-691,696.
[14]王茂丽.缓冲/回填材料的导热性能研究及预测分析[D].绵阳:西南科技大学,2015.
[15]刘艳,易发成,王哲.膨润土对铀的吸附研究[J].非金属矿,2010,33(1):52-53,57.
[16]范香.回填材料的工程性能研究[D].绵阳:西南科技大学,2010.
[17]侯莉.回填材料的优化集成及其性能研究[D].绵阳:西南科技大学,2008.
[18]易发成,侯莉,王哲.一种放射性废物处置回填材料及其制备方法:中国,ZL200810044755.6[P].2011-11-16.
[19]Idemitsu K,Tachi Y,Furuya H,et al.Diffusion of Cs and Sr in compacted bentonites under reducing conditions and in the presence of corrosion products of iron[A].Proceedings of the 1997Symposium on Scientific Basis for Nuclear Waste ManagementⅩⅪin Davos,1997.
[20]苏锡光,任立宏,龙会遵,等.放射性Sr、Cs及锕系元素在膨润土中扩散系数的研究[J].原子能科学技术,1998,32(Suppl):67-75.
[21]刘艳,王青海,陈洁,等.锶、铯在压实柯尔碱膨润土中的扩散行为[J].环境化学,2013,32(12):2250-2255.
[22]Neretnieks I.Diffusivities of some consitutents in compacted wet bentonite clay and the impact on radionuclide migration in the buffer[J].Nucl Technol,1985,71(2):458-470.
[23]张石升.核环境学基础[M].北京:原子能出版社,1999.
[24]仵彦卿.多孔介质污染物迁移动力学[M].上海:上海交通大学出版社,2007.
[25]郑春苗,Bennett G D.地下水污染物迁移模拟[M].北京:高等教育出版社,2009.
[26]贺勇.膨润土对重金属离子的阻滞特性研究[D].长沙:长沙理工大学,2012.
[27]Cho W J,Lee J O.Hydraulic conductivity of compacted bentonite-sand mixture for potential backfill material for highv-level radioactive waste repository[J].Journal of the Korean Nuclear Society,2000,32(5):495-503.
[28]Wang X K,Du J Z,Tao Z Y,et al.Evaluation of Eu(Ⅲ)migration in compacted bentonite[J].J Radioanal Nucl Chem,2004,260(1):69-73.
[29]王榕树,冯为.放射性核素在地质介质中的迁移研究[J].核化学与放射化学,1994,16(2):117-121.
[30]谢水波,陈泽昂,张晓健,等.宏观弥散度和阻滞系数对地下水中核素迁移模拟的影响[J].湖南大学学报(自然科学版),2007,34(5):78-82.