Science: Trick with Mirrors

The Atomic Energy Commission usually hates to tell about accidents to nuclear reactors. Reason: the public gets so jumpy. But about the latest such accident it not only lifted secrecy but has made a color motion picture snowing the tricky and dangerous work of repairing a reactor at Oak Ridge, Tenn. The film shows dozens of scientists and technicians working for nine months to patch two small holes that had been burned in the 5/16-in. zirconium shell of the reactor’s fiercely radioactive core.

This was no work for amateurs or bunglers. To gain access to the heavily shielded core vessel, high-density concrete slabs first had to be lifted by remotely controlled cranes, exposing the underground room that houses the reactor and its maze of pipes and pumps. The cell was then flooded with 20 ft. of water to protect the technicians from radiation while they lowered specially designed long-handled tools into a flanged opening, 2⅛ in. in diameter, at the top of the vessel. Then, cutting torches and reamers, operated by delicate levers, rounded out the irregular-shaped holes in the reactor shell, making them easier to patch.

Every step of the repair job was a novel and ticklish problem. Parts of the core that stood in the way were cut up and extricated on the points of slender spikes, all by remote control because of their radioactivity. The deadly inside of the reactor was invisible to direct observation, but long periscopes, manipulated through a 3-in. opening in the blanket around the core, gave a clear view of the melted spots. All these lights, probes and gauges had to be specially designed, and they were tested on an accurate mockup of the reactor before the atom-age repair crew dared to tackle the real job.

At no time, says AEC, was there any danger from escaping radiation. But just the same, added the official statement, it was “a most difficult feat.”