铀、钍在花岗岩单裂隙中的运移

利用自制花岗岩水平单裂隙实验装置与有机玻璃裂隙对照装置,采用脉冲注入法,研究了饱水单裂隙中铀(Ⅵ)和钍(Ⅳ)混合元素作为溶质的运移情况。获得了两个元素浓度随时间的变化曲线及核素的运移参数,得到以下结论:(1)元素在花岗岩单裂隙中的运移能力与裂隙中水流流速有关,流速越小,峰现时间越晚,元素的相对浓度越小,拖尾现象越明显;(2)花岗岩单裂隙中,等流速、等运移距离条件下,钍的相对浓度小于铀,并且随着流速减小和运移距离增长,差异逐渐增大,表明铀在花岗岩中的运移能力强于钍,主要与元素化学性质有关;(3)对比空白裂隙,元素在花岗岩单裂隙中的穿透曲线有明显的峰值削弱、峰现时间滞后和拖尾现象,表明花岗岩对铀、钍运移的阻滞效果十分理想。

U,Th Transport in Single Fractured Granite

The transport of U(Ⅵ) and Th(Ⅳ) through saturated single fracture with pulsed injection was studied using a self-made horizontal single fractured granite and an single fractured organic glass as control.Relative concentration change with time and radionuclide transport parameters are obtained.The results show that:(1) The transport ability of these two elements is related to flow rate.The relative concentration is reduced and the tailing phenomena is more obvious while the flow rate is reduced.(2) Under a same flow rate and transport distance,the relative concentration of Th in the fracture is lower than that of U,and the difference between the two elements increases with a lower flow rate and a longer transport distance,which indicates that the transport ability of U is stronger than that of Th as a result of the different chemical properties between these two elements.(3) Comparing with the control,the peak of the breakthrough curve in granite fracture is smaller in value and occurr later with tailing phenomena,which indicates that granite is an idealmaterial for retarding the transport of U and Th.