Friday 21 August 2015

Don't do this at home kids

Now I'm not stupid. I had a very expensive education. I've won prizes in pub-quizzes. I've spent a life-time in science. But I shouldn't be left alone in a laboratory because I don't think quickly enough. Many people are a lot more useful to science because they are a good pair of hands even if they don't know as much as me.  I've had my own disaster with radioactive material, so I am especially sensitive to stories of avoidable nuclear accidents. I've told the story of Chernobyl from my point of view 2000km to the West rather than investigating the failures of protocol and management on site that caused the melt-down and blow-up. I was a little more up-close-and-personal in my coverage for the Windscale fire which was brought under control by heroic, experienced and very smart technicians who stayed at their posts. I would have been useless in those hours; the best thing I could of done was either make tea or run like buggery to get out of the way.

You had to have a certain type of smarts to get a post on the Manhattan Project building the first atomic bombs.  It was time critical; every day of delay meant more allied servicemen dying, so only the smartest boys in the room need apply. Harry Daghlian was such a boy.  He grew up in Connecticut and went at an absurdly young age to MIT to read mathematics, switched to physics and was sent to Los Alamos while still working on his PhD in particle physics. He was assigned to a group that was working to determine how to minimise the critical mass of a radioactive 'pile'. Uranium and Plutonium were insanely expensive and each hard-won lump was destined to cause an explosion over distant Japan. It was clearly better to use as little as possible in each bomb-assembly.  How little was enough? That was the The Question.

70 years ago today, 21st August 1945, was just after the unconditional surrender had been agreed (15/08/45) but before the documents had been signed on USS Missouri (02/09/45). Meanwhile back at Los Alamos basic science was still going on.  The Critical Assembly Group was working with a 6.2kg sphere of radioactive Plutonium to see if they could make it "go critical" under controlled conditions.  The experiments that day involved adding tungsten carbide bricks one at a time around the 'hot' sphere and listening to the Geiger counter go fzzzzz.  Each alteration of the pile was recorded and another idea was tried out. Tungsten Carbide acts as a neutron reflector, so that these sub-atomic particles go back into the core to cause more fissions rather than dissipating into the surrounding air.

After dinner that night, Daghlian went back to the lab alone because he'd had an idea and couldn't wait to check it out. He was alone in the room except for a squaddie called Pte Robert J. Hemmerly who was there to stop unauthorized people stealing stuff. Daghlian went to work building up his Lego bricks in a 'let's try this' assembly [L] until it was damned close to going critical. As his hand hovered over the plutonium core and . . . he dropped the brick. Tungsten carbide is really dense (15x heavier than water), so each little brick - about the size of a tin of beans - weighed 5kg. Daghlian was probably wearing cotton gloves, he was well fed, it was near his bedtime, he'd been working all day and the golldarn brick slipped from his grasp.  There was a blue flash and the young researcher sustained a fatal dose of radiation.  He was alert enough to unpack his fatal pile and tell Hemmerly that something bad had happened. Another graduate student was on-site and drove him to hospital. Over the next 25 days, Daghlian's skin peeled off in layers, and he suffered through progressive system shutdown until he fell into a coma and died. Hemmerly was more fortunate, he lived for another 33 years before dying from leukemia. That's why we have SOPs [Standard Operating Procedures] in laboratories, so that it's more difficult for accidents to happen. When I flipped radioactive phosphorus into the corner of my eye I was definitely outside the SOP, and I was alone in the room.

15 years ago, Daghlian's surviving relatives unveiled a plaque in his home town of New London, CT "A brilliant scientist on the Manhattan Project . . . though not in uniform, he died in service to his country".  Whatever about de mortuis nil nisi bonum that statement is really not correct.

No comments:

Post a Comment