Experimental and Modeling Indications for Self-Sealing of a Cementitious Low- and Intermediate-Level Waste Repository by Calcite Precipitation
Experimental and Modeling Indications for Self-Sealing of a Cementitious Low- and Intermediate-Level Waste Repository by Calcite Precipitation
复制标题
通过方解石沉淀自密封水泥基低中放废物库的实验和建模指标
DOI：
--
复制
发表时间：
2002
期刊：
影响因子：
--
通讯作者：
W. Pfingsten
中科院分区：
文献类型：
--
作者：
W. Pfingsten
摘要在核废物水泥处置库附近，矿物反应将改变水泥降解阶段的水力条件和描述放射性核素随时间迁移的参数。由于矿物和水泥反应引起的孔隙度变化将影响渗透率和扩散率。富含CO2的地层水将导致水泥废物处置库周围导水带中的方解石沉淀。这将对放射性核素从胶结处置库释放到主岩环境中产生影响。顺序耦合的流动，运输和化学反应代码MCOTAC被用来包括这样的过程中的建模。孔隙度-渗透率关系和孔隙度-扩散率关系用于描述水泥降解和相关的次生矿物沉淀及其与反应性输运模型的耦合。二维模型计算被用来预测的时间演变的一个“小尺度”的水泥废物处置库的近场内的放射性核素的输运参数。减少溶质运移计算在存储库近场由于孔隙度和渗透率的变化，在岩石存储库接口。在小规模的多孔介质的方法，化学反应和流体动力学参数的耦合表明在主岩石存储库接口的几种情况下的自我密封的障碍。这一屏障可能会持续很长时间，并有效地将放射性核素限制在工程处置库系统内。考虑流动路径和屏障特定的异质性将是进一步提高对真实的水泥近场附近耦合过程的理解的一步。
Abstract In the vicinity of a cementitious nuclear waste repository, mineral reactions will change the hydraulic conditions and the parameters describing radionuclide transport with time during the cement degradation phase. Porosity changes due to mineral and cement reactions will influence permeability and diffusivity. Formation water rich in CO2 will lead to calcite precipitation in the water-conducting zones surrounding the cementitious waste repository. This will have an impact on the radionuclide release from the cementitious repository into the host rock environment. The sequentially coupled flow, transport, and chemical reaction code MCOTAC is used to include such processes in the modeling. A porosity-permeability relation and a porosity-diffusivity relation are used for describing cement degradation and related secondary mineral precipitation and their coupling to reactive transport modeling. Two-dimensional model calculations are used to predict the temporal evolution of transport parameters for radionuclides within a “small-scale” near field of a cementitious waste repository. Reduced solute transport is calculated in the repository near field due to porosity and permeability changes at the rock-repository interface. Within the small-scale porous medium approach, coupling of chemical reactions and hydrodynamic parameters indicates a self-sealing barrier at the host rock–repository interface for several scenarios. This barrier might persist for very long times and effectively contain radionuclides within the engineered repository system. Taking into account flow path and barrier-specific heterogeneity will be a further step to improve the understanding of coupled processes in the vicinity of a real cementitious near field.