Abstract: An automated system, method and apparatus for producing welded end closures in thin-walled metal tubes, preferably sealing a radioactive source inside the tubes, by use of an electronically controlled robot that grasps and sequentially repositions the tube through a series of stations in which the tube is bottom-welded, inspected, filled, inspected, top welded and inspected, and wherein the tube bottom and top are welded using multi-directional laser beams generated by a single laser light source and discharged through a plurality of spaced-apart laser welder heads. Brachytherapy seeds containing radiolabeled microspheres are produced using the system, method and apparatus of the invention.