Radiation? No Fear
Posted: Tue Jul 08, 2008 9:13 pm
I am somewhat less intimidated by Radiation than most folks.
As a freshman in college, on one of my first days in Chemistry, I learned something that shocked me.
A classmate told me the story of a Professor in the Engineering department who had a new Geiger counter a Geiger-Muller tube hooked up to an amplifier and speaker the classic science fiction radiation detector.
The Professor was so excited that he called a fellow professor in the Chemistry department and insisted on demonstrating it. He carried the whole contraption out to his car, drove over to the Chemistry Building, lugged the contraption up to the lab, and plugged it in. Nothing.
He dragged the whole thing back to his own lab to find the problem, set it up, and it worked perfectly.
He took it back to the Chem building, and again, it failed to operate.
After a couple of similar pointless excursions, he tried a new tack. He scrounged up a number of long extension cords, and set up the thing out in the Quad. Much better this time, when he turned it on he heard the familiar pop and crackle we now know are cosmic rays.
He moved the contraption closer and closer to the Chem building. As he approached the front step, the noise began to increase more popcorn noises. In the front door, it rattled like hail on a tin roof. Crossing the hallway, the noise rose to a crescendo, then stuttered and stopped at the top of a table in the hallway.
Geiger-Muller tubes operate by cascades of electrons. There is a very high voltage on separated cathode and anode, in a vacuum. One is a metal tube with a vacuum inside, and up through the middle of the tube is a metal bar that forms the other electrodes. The very high voltage means that when a high-speed charged particle passes an electron, a positron, or proton it releases a short-term shower of electrons that flow across the gap. That brief shower is the click of the Geiger-counter.
One of the limits of the Geiger-counter is that when the particle flow gets above a critical level, a constant current develops across the gap that does not particularly depend on external radiation.
On that tabletop, the particle flow was too high. Literally, when the Engineer had turned it on, on the table, it had been dead silent, because it was overwhelmed. That was unsettling. To test this outlandish conclusion, later that night, they turned out the lights and laid a fluorescent tube on the table. There, in the dark, it dimly glowed, powered by the latent radioactivity in the tabletop.
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And, the chemistry student concluded, I was now sitting on that very table. That was not a very funny joke, but I moved anyway. I later asked my lab instructor, a graduate student, if that was possibly true.
He rolled his eyes and asked me where I heard that rumor.
He also dodged the question, so I asked again. Ok, he admitted, it was true. Horrors. In fact, he said, the whole building we were in was so contaminated that no one should be allowed in it. Turns out that some of the initial research and preliminary refining of Uranium had been done in that building during World War II, for the Manhattan project. A couple of years later the building was closed and remained off limits for years. Eventually, I saw men in HAZMAT suits gutting the place and it was completely rebuilt inside.
So do I think that radiation exposure was a direct cause of my current problems?
Not at all.
Remember, the Geiger-counter constantly clicks, even when no radioactive source is near. We are all constantly bathed in very-low-grade radiation. I expect that my total dose of cosmic radiation over my lifetime far exceeds the amount I received in the few minutes I sat on the table.
Radiation, like everything else dangerous, must be respected, but it too, has its place.
As a freshman in college, on one of my first days in Chemistry, I learned something that shocked me.
A classmate told me the story of a Professor in the Engineering department who had a new Geiger counter a Geiger-Muller tube hooked up to an amplifier and speaker the classic science fiction radiation detector.
The Professor was so excited that he called a fellow professor in the Chemistry department and insisted on demonstrating it. He carried the whole contraption out to his car, drove over to the Chemistry Building, lugged the contraption up to the lab, and plugged it in. Nothing.
He dragged the whole thing back to his own lab to find the problem, set it up, and it worked perfectly.
He took it back to the Chem building, and again, it failed to operate.
After a couple of similar pointless excursions, he tried a new tack. He scrounged up a number of long extension cords, and set up the thing out in the Quad. Much better this time, when he turned it on he heard the familiar pop and crackle we now know are cosmic rays.
He moved the contraption closer and closer to the Chem building. As he approached the front step, the noise began to increase more popcorn noises. In the front door, it rattled like hail on a tin roof. Crossing the hallway, the noise rose to a crescendo, then stuttered and stopped at the top of a table in the hallway.
Geiger-Muller tubes operate by cascades of electrons. There is a very high voltage on separated cathode and anode, in a vacuum. One is a metal tube with a vacuum inside, and up through the middle of the tube is a metal bar that forms the other electrodes. The very high voltage means that when a high-speed charged particle passes an electron, a positron, or proton it releases a short-term shower of electrons that flow across the gap. That brief shower is the click of the Geiger-counter.
One of the limits of the Geiger-counter is that when the particle flow gets above a critical level, a constant current develops across the gap that does not particularly depend on external radiation.
On that tabletop, the particle flow was too high. Literally, when the Engineer had turned it on, on the table, it had been dead silent, because it was overwhelmed. That was unsettling. To test this outlandish conclusion, later that night, they turned out the lights and laid a fluorescent tube on the table. There, in the dark, it dimly glowed, powered by the latent radioactivity in the tabletop.
----------
And, the chemistry student concluded, I was now sitting on that very table. That was not a very funny joke, but I moved anyway. I later asked my lab instructor, a graduate student, if that was possibly true.
He rolled his eyes and asked me where I heard that rumor.
He also dodged the question, so I asked again. Ok, he admitted, it was true. Horrors. In fact, he said, the whole building we were in was so contaminated that no one should be allowed in it. Turns out that some of the initial research and preliminary refining of Uranium had been done in that building during World War II, for the Manhattan project. A couple of years later the building was closed and remained off limits for years. Eventually, I saw men in HAZMAT suits gutting the place and it was completely rebuilt inside.
So do I think that radiation exposure was a direct cause of my current problems?
Not at all.
Remember, the Geiger-counter constantly clicks, even when no radioactive source is near. We are all constantly bathed in very-low-grade radiation. I expect that my total dose of cosmic radiation over my lifetime far exceeds the amount I received in the few minutes I sat on the table.
Radiation, like everything else dangerous, must be respected, but it too, has its place.