某地下核设施场址地下水化学特征及其对水循环的指示意义

Hydrochemical Characteristics and Its Significance to Groundwater Flow System at an Underground Nuclear Facility Site

在核设施场址筛选和长期性能安全评价中,地下水化学特征是最重要的因素之一.本文采用数理统计、离子比例法、同位素分析法以及水文地球化学模拟等方法,对沿海某核设施场址水化学特征及主要控制因素、地下水补给来源与年龄等进行了分析,并构建了该场址地下水循环演化模式.研究表明:场址地下水中TDS较低,pH值多呈弱酸性;地下水化学类型主要为HCO_(3)-Na·Ca型和HCO_(3)-Ca·Na型;水化学组分主要受硅酸盐岩风化作用的控制;地下水主径流路径上以钠长石、钙长石的风化溶解为主;地下水来源于当地大气降水入渗补给,硐室深度范围内地下水14C表观年龄为2.08~3.60 ka.该场址地下水化学特征及水循环交替条件对于保障该核设施的安全性是有利的.

Hydrochemical characteristics are one of the most critical evaluation factors for the site selection and long-term performance safety evaluation of nuclear facilities.Mathematical statistics,ion proportion method,isotope analysis method,and hydrogeochemical simulation were used in this paper to investigate hydrochemical characteristics of an underground nuclear facility site along the coast.Its hydrochemical characteristics,possible controls,groundwater recharge source,and apparent age were analyzed.Furthermore,the conceptual model of groundwater flow and hydrochemical evolution in the area was preliminarily constructed.The results suggest that the total dissolved solids(TDS)of the groundwater is low,and the pH value in most samples is weakly acidic.The hydrochemical types of groundwater sampling from boreholes and tunnels are mainly HCO_(3)-Na·Ca and HCO_(3)-Ca·Na.The weathering of silicate rocks specifically controls hydrochemical components.Moreover,the weathering dissolution of albite and anorthite is the primary water-rock interaction of groundwater along unconfined aquifer main runoff paths.The groundwater source is the infiltration recharge of local atmospheric precipitation,and the 14C apparent age in the depth range of nuclear facilities is about 2.08-3.60 ka.It is concluded that the hydrochemistry and groundwater circulation conditions at the site are beneficial to ensure the safety of underground nuclear facilities.