Development of the Hydrogeological Survey Method Using the Natural Dissolved Noble Gases for the Site-Characterization for Radwastes Disposal
Development of the Hydrogeological Survey Method Using the Natural Dissolved Noble Gases for the Site-Characterization for Radwastes Disposal
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利用天然溶解稀有气体进行放射性废物处置现场表征的水文地质调查方法的开发
DOI：
10.1557/proc-353-1371
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
Y. Mahara
中科院分区：
文献类型：
--
作者：
Y. Mahara
本研究的重点是利用溶解的天然惰性气体开发示踪方法。该方法精确测量地下水中溶解的氦和氖，用于测年。由于溶解氦由三种不同组分（大气氦、放射性成因氦和地幔氦）组成，如果能够将总溶解氦分离到每一组分中，就可以预测原位地下水中年轻地下水和古老地下水的混合速率。然后，通过测量地下水样本中的氚和生氚3He来确定年轻地下水的年代。另一方面，古老地下水的测年方法还没有得到验证。在本研究中，通过岩石中铀和钍的α衰变，通过放射性成因氦的积累速率来预测旧地下水年龄。该示踪方法应用于熊本平原某承压含水层（10km × 20km），对该含水层的地下水流动和地质水文形成进行了较为详细的研究。该地区的地下水由年轻地下水（年龄小于20年）和古老孤立地下水（年龄大于1000年）混合组成。此外，氦同位素比值的剧烈变化意外地揭示了地下水盆地中活动断裂的存在。因此，使用溶解惰性气体的方法在现场表征的早期阶段对含水层的地质水文形成进行研究是可行的。
This study focused on developing the tracer method using the dissolved natural noble gases. The method measures precisely helium and neon dissolved in groundwater for dating. Since the dissolved helium consists of three different components (Atmospheric He, Radiogenic He and Mantle He), if it is possible to separate total dissolved helium into each component, the mixing rate between young groundwater and ancient will be predicted in in-situ groundwater. Then, dating of young groundwater is determined by measuring tritium and tritiogenic 3He in a groundwater sample. On the other hand, the dating method for old groundwater is not still verified. In this study, the old groundwater age is predicted by the accumulating rate of radiogenic helium through the alpha decay of uranium and thorium contained in rock. This tracing method was applied to a confined aquifer in the Kumamoto plain (10km × 20km ), where the groundwater flow and the geohydrological formation of aquifer was investigated in detail in the past. The groundwater in the area consists of mixture of young groundwater (less than 20 yrs old) and ancient isolated groundwater (more than 1000 yrs old). Furthermore, the drastic change in the helium isotopic ratio revealed unexpectedly the existence of active faults covered in groundwater basins. Consequently, the method using the dissolved noble gases is practicably available for investigating the geohydrologic formation of aquifer at the early stage of the site characterization.