An improved system for receiving and storing a radioactive salt solution includes a tank configured to receive the radioactive salt solution while preventing criticality accidents, a solution inlet for carrying the radioactive salt solution to the tank, an overflow bottle, and a cap sealing the top end of the tank. The cap includes a lateral wye fitting having a lateral pipe configured to direct the radioactive salt solution from the solution inlet into the tank, a vertical pipe configured to direct gases from the tank to a ventilation system, and an overflow line configured to carry excess radioactive salt solution from the tank to the overflow tank. An air gap between the lateral pipe and the solution inlet prevents backflow of the radioactive salt solution into the solution inlet. A control system includes a level switch configured to provide a signal that the tank contains a maximum volume of the radioactive salt solution, a first valve configured to terminate flow of the radioactive salt solution to the lateral pipe upon receipt of the signal from the level switch; and a second valve configured to allow flow of the radioactive salt solution from the tank to the overflow line.