Radioactivity And The Geiger Counter – Part 1

Doc Mike Finnley, Going Postal
A GS-3CD Geiger counter from the 1960s

I would not say that I am afraid of science and technology but I do make an exception in certain areas: nuclear physics being one example.

Firstly, it’s very dangerous to play with (duh!). Secondly, the materials – thank goodness – are very difficult to obtain; and thirdly, for the amateur, it has no practical use.

Curiosity, however, usually allows me to find an exception to my exceptions and the Geiger counter is a case in point.

Let’s look at an example of where a Geiger counter would have proved extremely useful – to say the least!

Goiânia Accident (or stupidity, as I call it!)

Doc Mike Finnley, Going Postal
Nice Fountain 

The year is 1987 and the story unfolds in the Brazilian city of Goiânia, the capital of Goiás.

In this city was an abandoned hospital and within an equally abandoned radiotherapy machine. Before I get to Roberto and Wagner’s stupidity we’ll have a look inside one of these units.

A radiotherapy unit is used for treating cancer (a great irony of physics). At its heart is a source of radioactive material. In the case of this unit it contained a capsule of caesium-137. The capsule is designed to ‘hold’ the radiation until it is needed. The radiation comes out of a ‘window’ in the capsule which can be opened or closed. When in the open position it releases 4.5 grays of radiation per hour at a 1 meter distance.

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Okay, let’s just stop there for a moment. That last sentence is very important to the understanding of the power of nuclear radiation and radiation in general.

There are many units of measurement for radioactivity: Sievert, Becquerel (Bq), Rad, Gray and Rem amongst others. Ionising radiation has an accumulative effect upon the human body. We all know that a doctor will be reluctant to send you for, say, a chest X-ray. Having such a X-ray will expose your body to about 10 milli-rem of radiation or 0.0001 gray.

The total background radiation (in the UK) that we all receive annually is about 300 milli-rem, so your chest X-ray ‘uses up’ 1/30th of your yearly ‘normal’ exposure. About 12 days worth of background radiation per chest X-ray.

This capsule was releasing 4.5 gray every hour, or 450,000 milli-rem. Not in one year but every hour! That’s the dose of radiation that you would receive if you stood one meter in front of it for one hour. It makes a chest X-ray look pretty tame!

And just to put 4.5 gray into context, workers at Chernobyl were exposed to an excess of 175 gray-per-hour! Such a radiation level means that they received a lethal dose in less than a minute. Poisoned with no antidote.

Back to the story…

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Introducing the two culprits that, through their greed and stupidity, caused the worst peacetime civilian nuclear incident that the world has seen: Roberto dos Santos Alves and Wagner Mota Pereira.

September 13, 1987, they broke into the abandoned hospital and thought it a good idea to steal the radiotherapy machine. They used a wheelbarrow to take it to Alves’s home thinking that it might have some scrap metal value!

As they disassembled the unit – no doubt covered with bright yellow radiation warning stickers – they both started to vomit. Not good.

The following day Pereira began to experience diarrhoea and dizziness and his left hand began to swell. He had to have several fingers amputated.

This didn’t stop Alves, though. Oh no. He continued to dismantle the machine until he’d freed the caesium capsule. His right arm ulcerated and he had to have it amputated.

On September 16, while Alves’s right arm was cooking nicely at gas mark 1000, he manged to puncture the caesium capsule with a screwdriver. He saw a deep blue light emerging from the hole that he’d made.

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The blue glow is probably formed by Cherenkov radiation. In this case an interaction between the radiation and the moisture in the air.

A similar glow was observed in 1988 at the Oak Ridge National Laboratory while they were dismantling a caesium-137 capsule.

The photo below shows the blue Cherenkov glow emitted from the water in the Advanced Test Reactor in Idaho.

Doc Mike Finnley, Going Postal
Cherenkov Radiation

* * *

The Tragedy

On September 18, Alves sold the capsule to scrapyard owner Devair Alves Ferreira. He was fascinated by the blue glow and thought that it might be valuable or even a supernatural phenomenon!

Ferreira managed to free some of the caesium from the capsule and on September 24 he took the substance to his house.

He spread some of it onto a concrete floor, no doubt amazed at the magical glow.

He had a six year old daughter, Leide das Neves Ferreira. Leide ate a sandwich whilst sitting on the contaminated floor. She was naturally fascinated by the strange blue glow. She wiped some of the powder onto her body and showed the magical effect to her mother.

Leide received 6 gray of radiation. Both externally and through ingestion.

The Authorities Are Notified

Finally, on September 28 Leide’s mother, after becoming sick herself, took a sample of the caesium to a local hospital. Fifteen days after the idiots Alves and Pereira had stolen the radiotherapy machine.

Leide died on October 23, 1987 suffering from septicaemia and general infection. From Wikipedia:

“She was buried in a common cemetery in Goiânia, in a special fibreglass coffin lined with lead to prevent the spread of radiation. Despite these measures, news of her impending burial caused a riot of more than 2,000 people in the cemetery on the day of her burial, all fearing that her corpse would poison the surrounding land. Rioters tried to prevent her burial by using stones and bricks to block the cemetery roadway. She was buried despite this interference.”

Her mother died on the same day. Her father survived, even after being exposed to 7 grays of radiation! He died in 1994 by drinking himself to death.

Interesting things that were (supposedly) contaminated by the event:

* Three buses
* 42 houses
* 14 cars
* Five pigs and…
* 50,000 rolls of toilet paper! (Don’t ask. It’s Wikipedia.)

 

Full article:  Goiânia accident

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In part 2 we’ll take a look at detecting radioactivity and an unusual source of radiation to test a home made Geiger counter.
 

© Doc Mike Finnley 2019
 

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