The worst case scenarios with misplaced radioactive materials

The disappearance of a tiny capsule of radioactive material in Western Australia has sparked fears of contamination causing serious health problems.

But if the Tic-Tac sized capsule containing Caesium-137 can never be found, the side of a highway in the most remote part of the world is far from the worst-case scenario.

Professor of Medical Imaging Science Dale Bailey at the University of Sydney said the capsule would be giving off the same radiation as a CT scan every hour.

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"If this thing is lost in the desert, and it's never found, that's not a bad outcome," Bailey said.

"The nightmare scenario is some fossicker comes along in five or 10 years' time and pops it in their pocket."

University of South Australia's Associate Professor in Biophysics Ivan Kempson said a fleeting encounter with the capsule would probably not be dangerous.

"If you go out in the sun, if you go for a little walk for five minutes  - not a problem," he said.

"If you went to lay down for five hours, you're gonna have a problem with sunburn."

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Another grim possibility is the capsule becomes wedged in the tyre tread of a passing car.

"If there was a bedroom right next to the garage and someone slept there every night, someone could get a small dose," Bailey said.

"But I still don't think it would be approaching anything lethal like that."

The worst-case scenario with the loss of a radioactive capsule was realised in the 1980s in the USSR.

A capsule containing Caesium-137 was lost in a quarry used to dig up gravel.

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By terrible chance, that capsule ended up in the building materials of an apartment block in the Ukrainian town of Kramatorsk.

The wall where the capsule was stuck happened to be beside the bed of a teenager.

In 1981, the teen girl died suddenly, followed by her brother and mother, all from leukaemia.

Doctors blamed those deaths on genetics.

It was only after the leukaemia death of a child in a new family who had moved into the apartment that an investigation began.

Six deaths and 17 other cases of radiation exposure were linked to the Kramatorsk apartment.

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Kramatorsk is now on the front lines of the Ukraine-Russia war.

In another tragic instance, a radioactive source was left in a teletherapy unit at an abandoned hospital in Brazil, also in the 1980s.

Two burglars stole the unit and broke it up for scrap metal.

The burglars, who were unknowingly already suffering from radiation poisoning, sold the radioactive source to a scrapyard.

When the scrapyard owner noticed it glowing, he brought it into his house and invited friends and family to look at it.

In the end, four people died and 249 suffered radioactive contamination.

But Bailey noted that while it was the same substance, Caesium-137, the situations are very dissimilar.

"This was about 2000 times stronger in terms of the radioactivity," he said.

"It's not the same magnitude, but it's the same isotope."

It is possible to track down the radioactive capsule, but such a search would be time-consuming.

Detectors could pick up its radioactivity from a distance of about 10 to 15 metres, Bailey told 9news.com.au.

"If they had a van that had a couple of detectors mounted around, and they crawl down the road at 10km an hour, you've got a chance to find that," he said.

But failing that, the capsule may remain missing forever, but its radioactivity will remain.

Caesium-137 has a half-life of 30 years, which means it will likely remain radioactive until the year 2323.

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