Granite has relatively low-permeability and it has been considered as one of favorable geological formation for final disposal of high-level radioactive waste (HLW). However, the granite is often fractured and characterized as complex discrete fracture-matrix systems with considerable degree of uncertainties in its physical and geometrical properties. Prediction of nuclide migration in fractured granite at large spatial and long temporal scales is important for safety assessment of HLW disposal. In the present study, parametric studies are performed to evaluate the long-term barrier performance of fractured granite using the Beishan granite barrier as an illustration example. As the distance between the fast water-conducting path (FWCP) and the disposal pit decreased from 80 m to 0, the nuclides' arrival time () in the biosphere decreased from 9000 to approximately 2000 years when the effects of the fault and the FWCP are considered. The maximum nuclide concentration () increases from 0.0019 (350,000 years) to 0.0121 mSv/y (150,000 years), exceeding the limit of 0.01 mSv/y. In addition, as the permeability (equivalent hydraulic aperture) of the FWCP increased from 5.0 × 10 m to 1.0 × 10 m, the of Cs-135 further decreases to about 15,000 years, and the increases to 0.0256 mSv/y (100,000 years), suggesting a significant reduction in the long-term performance of the geological barrier. These findings are helpful for site assessment of HLW repositories built in fractured granite.

中文翻译：

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评估用于核废料处理的裂隙花岗岩的长期屏障性能：快速导水路径的影响


花岗岩具有相对较低的渗透性，被认为是最终处置高放废物（HLW）的有利地质构造之一。然而，花岗岩经常断裂并被表征为复杂的离散断裂基质系统，其物理和几何性质具有相当程度的不确定性。大空间和长时间尺度裂隙花岗岩中核素迁移的预测对于高放废物处置的安全评估具有重要意义。在本研究中，以北山花岗岩屏障为例，进行参数研究来评估裂隙花岗岩的长期屏障性能。随着快速导水路径 (FWCP) 与处置坑之间的距离从 80 m 减小到 0，当断层和 FWCP 的影响时，核素到达生物圈的时间 () 从 9000 年缩短到大约 2000 年。被考虑。最大核素浓度 () 从 0.0019（350,000 年）增加到 0.0121 mSv/y（150,000 年），超过了 0.01 mSv/y 的限值。此外，随着FWCP的渗透率（等效水力孔径）从5.0×10m增加到1.0×10m，Cs-135的渗透率进一步降低到15000年左右，增加到0.0256mSv/y（100000年） ，表明地质屏障的长期性能显着降低。这些发现有助于对裂隙花岗岩建造的高放废物处置库进行现场评估。