It didn't take as long as Mohammed Matsui expected. They found the fissionables magazine, and in it plenty of plutonium, each subcritical slug in a five-hundred-pound collapsium canister. There were repair-robots, and they only had to replace the cartridges in the power units of three of them. They sent them inside the collapsium-shielded death-to-people area--transmitter robots, to relay what the others picked up through receptors wire-connected with the outside; foremen-robots, globes a yard in diameter covered with horns and spikes like old-fashioned ocean-navy mines; worker-robots, in a variety of shapes, but mostly looking like many-clawed crabs. Neither the converter nor the reactor had sustained any damage while the fissionables were burning out. So the robots began tearing out reactor-elements, and removing plutonium slugs no longer capable of sustaining chain reaction but still dangerously radioactive. Nuclear reactors had become simpler and easier to service since the First Day of the Year Zero, when Enrico Fermi put the first one into operation, but the principles remained the same. Work was less back-breaking and muscle-straining, but it called for intense concentration on screens and meters and buttons that was no less exhausting. The air around them began to grow foul. Finally, the air-analyzer squawked and flashed red lights to signal that the oxygen had dropped below the safety margin. They had no mobile fan equipment, or time to hunt any; they put on their fishbowl helmets and went back to work. After twelve hours, with a few short breaks, they had the reactors going. Jerry Rivas and a couple of others took a heavy-duty lifter and went looking for conversion mass; they brought back a couple of tons of scrap-iron and fed it to the converters. A few seconds after it was in, the pilot lights began coming on all over the panels. They took two more hours to get the oxygen-separator and the ventilator fans going, and for good measure they started the water pumps and the heating system. Then they all went outside to the ship to sleep. The sun was just coming up. It was sunset when they rose and returned to the building. The airlocks opened at a touch on the operating handles. Inside, the air was fresh and sweet, the temperature was a pleasantly uniform 75 degrees Fahrenheit, the fans were humming softly, and there was running hot and cold water everywhere.