A radiation-shielding storage/transport container has a cast-iron vessel having an open end defining an end face, a steel ring engaging the end face and forming at least one annular seat, a weld unitarily bonding the ring to the end face, and a cover secured to the steel ring in the seat thereof. The cast-iron vessel is formed at its open end with an annular seat having a shoulder surface forming the end face. The weld is an aluminothermic weld that extends over the entire surface of the interface between the ring and the vessel. The ring is formed with two such seats and the cover includes an inner plug cover and an outer cover each in a respective one of the seats. The outer cover is of steel and a second peripheral weld connects the outer cover to the respective seat.