Louis Slotinthe WorkbenchISTP

At about twenty past three on the afternoon of Tuesday, 21 May 1946, in a laboratory in a canyon outside Los Alamos, a screwdriver slipped.

Louis Slotin, 35, had been using its blade to hold the top half of a beryllium shell above a ball of plutonium. The screwdriver was all that kept the two halves apart.

He was born in Winnipeg on 1 December 1910, the son of Jewish refugees from Russia. By 1946 he was, in his own words, one of the few experienced “bomb putter-togetherers” left at Los Alamos. He liked to do the hands-on work himself.

The experiment was a delicate one. The closer the top shell came to the bottom, the nearer the core came to a runaway chain reaction. The whole art lay in keeping a gap and never closing it. The approved method used shims as spacers between the halves. Slotin used the screwdriver, lowering and raising the shell by hand. He had done it before, and it had worked.

That is the kind of shortcut Workbenches are proudest of finding: the shortest method that works, with nothing extra. To hands as good as his, the spacers looked like extra. Every success made the screwdriver feel a little safer than it was.

In ordinary life the screwdriver rarely looks deadly. It looks like skipping a safety check because you have done the job a hundred times, or cutting a step that has never once caught an error. Most of the time, the instinct is right. The trouble is that most of the time is not a safety margin.

That afternoon he was showing the technique to Alvin Graves, who was due to take the work over. Seven other people were in the room.

When the blade slipped, the top shell dropped onto the bottom one and the core went critical. There was a blue flash and a wave of heat. Slotin flicked the top shell off with his left hand, and the reaction stopped. He had moved before anyone else in the room could.

There was no panic in it, and no speech. It was a technician's verdict on a failed run, from a man who understood at once what had happened to him.

Then he turned to the next job. He sketched the room, marking where each person had been standing at the moment of the flash, so the doctors could work out the dose each of them had taken.

Slotin died nine days later, on 30 May 1946. The seven others in the room survived the accident.

The confidence that let him trust a screwdriver was the same confidence that moved his hand within half a second when it slipped. It was one gift, pointed two ways.