A radioisotope generator system can include a column assembly having a column, an inlet arm, an outlet arm. The column can contain packing material that binds a radioisotope. In addition, the column may define a notch between an open area and a stopper receptacle area in which an opening of the outlet arm is positioned. In some examples, the system includes a Luer lock connection between the outlet arm and a connector tubing. The Luer lock connection can include a male Luer cap and a female Luer cap each comprising tabs configured to line up with or overlap each other so as to indicate when the caps are sufficiently tightened together so as to form a non-leaking lock.