Radioactive Pa — how dangerous is it?
By Frederic Friedel
On 26 April 1986 a nuclear reactor blew up in Chernobyl, Ukraine, which was at the time part of the Soviet Union. It was a light water graphite moderated reactor, and the accident took place during a power-failure stress test with safety systems deliberately turned off — human error. There was an uncontrolled reaction in the core, which led to a disastrous steam explosion and an open-air graphite fire which sent giant plumes of fission products into the atmosphere. The radioactive material from Chernobyl spread over the surface of the western USSR and most of Europe.
At the time I owned a Geiger-Müller counter (note that I do not forget German physicist Walther Müller, who had a role in developing the device). It contains a tube that is filled with a very low pressure gas mixture with two electrodes kept at a potential difference of a few hundred volts.
When a high energy particle passes through the tube some gas molecules are ionized and allow current to pass between the electrodes. That produces a click in the loudspeaker built into the device., and I cleverly connected it to the “+” key of a pocket calculator. By pressing 1+1 and then switching on the GM counter I could read the number of clicks over a period of time, measured by a stop watch.
Immediately after the Chernobyl event my boss in the German TV station I worked for called the manufacturers of Geiger-Müller counters in an effort to buy one. They just laughed: apparently they were completely sold out, but receiving calls every few minutes. So we were stuck with my tiny little device, and I was sent out to measure the fallout.
But there was a problem: under normal conditions I would register 8–12 clicks per minute — mainly charged particles from cosmic sources. However, this background radiation did not change at all when I took it outside the house after the Chernobyl disaster. We were perplexed: reports said that Europe had been blanketed by radioactive fallout — in fact there were warnings about eating any vegetables grown in the open, or drinking milk from grass-grazing cows. But I was measuring nothing. Your counter is broken, they said at the TV station.
But then I was sent to Munich, where I stayed in the house of a friend. When I went into his garden I suddenly measured 120 clicks per minute. Clearly this was Chernobyl material. The friend, Helmut, was terrified: are we all going to die? I told him to calm down. On the flight to Munich I had measured 250–300 clicks per minute, the radiation level at 35,000 feet. In any case we came to the conclusion that the clouds of radioactive material had circled Hamburg, where I live and work, and that we had received practically no fallout. Prevailing wind conditions will do that.
We made a 20-minute TV segment on Chernobyl and on the radiation levels in Germany. I borrowed a very expensive, accurate counter from the University of Hamburg and prowled around the Kernkraftwerk Stade, an atomic energy plant near Hamburg. It was built in 1972, over ten years before Reactor #4 in Chernobyl (the one that blew up). Getting as close to the reactor as possible without being arrested, I could still not get the counter to register more than normal background radiation — not an extra micro REM per minute. Then I had an idea: we proceeded to the local church, and there I was able to measure a small increase in radiation — from the granite blocks at the base of the church.
I still have my Innova Gamma counter, and over the years have taken it with me to many exotic places. It is always a disappointment: apart from the plane trip I never get more than a few clicks above normal background radiation. But I use the counter to scare people: I have a clock, built by my father in 1952 (it is described here). Its dial used radium that would glow at night. But that stopped many decades ago — now the numerals and hands just have a thin dark crust on them, and not even the faintest glow in the dark. That radium is dead, you would think — until you bring my Innova counter close to the face: then I get 30–40 clicks, still, after all this time. I shudder to think what it must have been originally, when the clock glowed brightly at night. The same applies to a wrist watch I own — it stopped glowing ages ago, but still causes dozens of extra clicks per minute. When it was at full power I wore it 24 hours a day, for a number of years. Strangely my hand is still intact.
One more horror story? I remember during my childhood watching women paint radium onto the dials and hands for the timepieces my father’s company would produce. They had radium paste in little jars, and used very fine painters’ brushes to apply them into the grooves of the dials and hands. In between they would twist the brush between their lips to sharpen the point. Really! Some were quite old and had been doing this for most of their lives. Apparently it is not immediately and fatally dangerous.
Now fast forward thirty years from Chernobyl and my efforts to measure the fallout. Some years ago I noticed that I tended to be out of breath when walking and talking at the same time (which I do a lot). My doctor did not like this at all, and he sent me for a full cardiac checkup. The first step was a radiological examination of the blood flow in my coronary arteries. Unfortunately this does not show up in x-rays, and the Doppler measurement with external devices (seriously, they have radar equipment to measure the speed of blood flow in your arteries) is not specific enough to allow accurate diagnosis. The best way is to inject radioactive waste and then measure its distribution in your blood vessels. I kid you not.
So they injected Technetium into my vein. This is a chemical element (Tc 99m, atomic number 43) that does not occur naturally, except in minute traces, but is produced as a by-product of uranium-235 fission in nuclear reactors, where it is extracted from the spent fuel rods. On a side note: the world supply of Technetium is currently in serious danger. Almost all of it comes from six research reactors, four of which are over 50 years old and will soon be closing. The problem is that Technetium has a very short half-life — most of it decays within a day. So it cannot be stockpiled and has to be flown to the clinics every few days. Also: it is produced in reactors that use weapon-grade highly-enriched uranium, which we are trying to phase out. So the world is facing a Technetium shortage — we are running out of a crucial radioactive waste.
But back to my radioactive diagnosis: after injecting the Technetium they told me to stroll around for an hour, have a nice breakfast, and then come back for the scan. Of course I had my trusty GM counter with me, and as soon as I was outside I switched it on to check whether I was measurably radioactive. Unfortunately the battery had run out and the counter emitted no clicks, just a constant tone. I started looking for a shop to buy a new battery, but before I had found one it occurred to me to do an experiment: I placed the GM counter on a ledge, switched it on and stepped back. Immediately the constant tone was replaced by rapid clicks, which became slower the further I moved away from the counter. It was working, I was radioactive, and not just a little bit!
After the hour I was back in the clinic and they did the scan. You lie motionless on a table while a scintigraphic camera takes images of your heart from different angles, recording the Technetium’s presence in the muscles and recording that as images for later analysis. This is what it looks like:
The Technetium that has accumulated in the heart tissue can be detected quite accurately, and the cardiologist can tell which areas do not have sufficient circulation — in my case they could see that the left circumflex artery was blocked. A week later they opened it with a stent, inserted through an artery, using a procedure I had witnessed as a medical assistant decades earlier, when it was still in its early pioneer stage (read my report). It was very successful and I am fine now — thank you for asking.
One more thing: after they had finished the Technetium heart scan I walked over to the office of my sons, which is just a short distance away, and showed them how my GM counter reacted to me. Martin immediately burst into action. He called all the colleagues in the office together, also people from neighbouring companies, and held a lecture on radiation, on how Geiger Müller counters work. They dutifully noted that the background radiation was around ten clicks a minute. Then he led them into the meeting room, and the count immediately went up — 20, 30... Everyone was alarmed. Was it because the room overlooks railway tracks, on the fifth floor? Or was there some kind of dangerous contamination? Yes, there was. Martin walked over to where he had sat me down, and the GM counter rose to hundreds of clicks, until it became a constant tone. Later he repeated the experiment, with his smart phone recording the walk:
Note that initially, outside the meeting room, the Innova GM counter — yes, my original device! — does not emit a single beep. That is normal for ten beeps per minute. But when Martin goes into the room it start to register radioactive particles, all emanating from me. And then, when I take the counter into my hand, the beeps become a constant tone. It is thousands of beeps per minute.
Of course everyone was shocked and horrified, especially one female colleague, who looked particularly alarmed. To her I said: “Hug?” After ten seconds she bravely said “Okay,” and stepped forward, but I spared her the trauma. A week later I returned to the clinic and asked some trivial question. Actually I went there to measure the radiation in their workplace: it was many hundreds of clicks per minute. These people are working at such levels all day, every day of the week. Apparently human beings can take that kind of exposure. My own radiation continued for a day, subsiding considerably over that time, until two days later we were back to normal background radiation, coming from the cosmos. So apparently I am going to survive too.