sodium through the reactor, which suggested no more than six assemblies could have melted. Further testing involved slowly removing one control rod at a time to see what occurred, and this demonstrated that some melting had definitely happened. The problem then became how to identify the exact assemblies that were damaged, and how to remove them from the core. As there was no clear picture of how the fuel was arranged after melting, moving any of the assemblies might cause prompt criticality. Over the next several months, fuel assemblies were removed one by one and shipped to a hot cell in Columbus, Ohio for examination. This revealed that four assemblies had melted, and two had stuck together. Most of the fuel had been removed by May 1967. At that point, the sodium began to be drained and by August enough had been removed to expose the bottom of the reactor vessel. The interior was examined with a periscope and discovered what looked like a crushed beer can at the bottom. New systems were used to get better images, revealing it to be a folded piece of sheet metal. The problem became how to retrieve the object for study. Ultimately this required one of the sodium inlets to be cut open and a new device built that retrieved the metal. It was soon identified as a piece of zirconium shielding. To prevent melted fuel from burning through the bottom of the reactor, sheets of zirconium, which could withstand the temperatures of a meltdown, were spread across the bottom of the sodium tank. When the conical guide had been added, it was later noticed that it presented an unprotected area in the center of these plates. Amorosi added six triangular zirconium plates to the cone to prevent this escape route. The shields were added in 1959, late in the design process, and had not been added to the blueprints. Two of these plates had broken off and plugged the holes that allowed the sodium to flow around the fuel, causing the assemblies in those areas to overheat and melt. Restart A review demonstrated that the cone ultimately served no purpose, and the entire system had been removed by the end of 1968. The plant received permission to load fuel again in February 1970. In May, while under inspection by the AEC for startup, of sodium burst from a pipe, causing another pipe