Sunday, February 5, 2023

Orphan Source:

the Australian missing radioactive pellet was not alone

Zoë Sharp


When most people in the UK use the phrase “fell off the back of a lorry” most other people understand that means the object, whatever it is, has been stolen.


Not quite the case with the radioactive capsule that did indeed fall off the back of a truck as it drove along a 1400km stretch of road in Western Australia recently.


I’m not entirely sure what frightens me most about this story.



To give you the background, this harmless-looking pellet was “a 19-gigabecquerel caesium-137 ceramic source”. The pellet measured just 8mm in height and 6mm in diameter – somewhat smaller than a coin.


It was part of an industrial radiation gauge used to measure the density of iron ore feed at a mine in Rio Tinto. In theory, it was designed to be exposed to weather and vibration, but a bolt holding the lead-lined gauge together worked loose, and the pellet then fell out through the resultant bolt-hole.


It was thought that the problem might have been caused by vibration on the truck ride taking the device from a mine north of Newman in the Pilbara region, to its destination in Perth. Somewhere along the intervening stretch of desert highway, the pellet had bounced out of the back of the truck and disappeared.


Now, a pellet measured in millimetres sounds very small – and physically, it is. But from what I can gather, the safe level of radon in a home environment, for example, is 148 becquerels per cubic metre. A gigabecquerel is 1,000,000,000 becquerels.


So, this pellet could be considered really quite radioactive, then. Certainly, it was said to pose “a significant risk” to public health. Standing within a metre of the object would be the equivalent of having 10 X-rays per hour.



Perhaps scarier than losing this glow-in-the-dark doodad in the first place, was the fact that those responsible did not discover it was missing at all for fifteen days. The pallet containing the item was collected from the mine on January 10th. Six days later, it was delivered to a radiation service company in Malaga, a suburb of Perth, but it was not for another nine days that the company opened the delivery to reveal the damaged device.


Prolonged exposure, it is reported, can cause skin burns, radiation sickness, effects on the gastrointestinal and immune systems, and cancer.


When this loss was discovered, a warning was issued not to pick up or handle the pellet. Western Australia’s chief health officer, Andrew Robertson, said: “If you are further than five metres away from the source, certainly if you are more than twenty metres away from the source, it will pose no danger to you. If it is closer than that, and we strongly discourage people from picking it up, certainly don’t put it in your pocket or put it in your car, don’t put it on your sideboard, it will continue to radiate.”


Slightly Less Scary

Six days later, on February 1st, Australian authorities were able to report they had successfully found the missing pellet south of Newman – not far from where it began its journey.


The initial discovery was made by driving along the route at 70kmh with detection equipment. Staff then narrowed it down using a handheld radiation device. A twenty-metre exclusion zone was established around the site and further radiation surveys will be carried out. As well as a thorough investigation, one hopes, of how this happened in the first place.


Scariest of All

But the really scary thing, according to Dr Edward Obbard, a senior lecturer in nuclear engineering at the University of New South Wales, Sydney, is how frequently dangerous or deadly substances are mislaid.


A piece of radioactive material that is not under any type of oversight or regulatory authority is called an “orphan source”. This reminds me of a quote from a 1995 film starring Christian Slater and John Travolta called Broken Arrow.


A “broken arrow” is defined as “an unexpected event involving nuclear weapons that result in the accidental launching, firing, detonating, theft, or loss of the weapon.” When one character explains this definition to another in the movie, he responds: “I don’t know what’s scarier – losing nuclear weapons, or that it happens so often there’s actually a term for it.”


Since 1950, the US military has had more than thirty broken arrow incidents. Six nuclear weapons remain unaccounted for.


Around the world, material is classified as orphan source about a hundred times every year. In total, 1205 cases since 2013.


The Liá Accident

One of the most well-known international incidents was in rural Georgia (the country, not the US state) in 2001. Villagers from Liá, out collecting firewood near the Enguri Dam in the Tsalenjikha district found two metal canisters that were hot enough to melt the snow around them. They used the objects as heaters during a cold night in the forest, and within hours had fallen sick. One man died as a result.


The metal “heaters” turned out to be strontium-90 from radioisotope thermoelectric generators (RTGs) which had been intended for use to power radio transmitters connecting the Enguri Dam with the Hudoni Dam. The project, begun in the 1980s, was abandoned on the eve of Georgian independence from the Soviet Union, and the RTGs with it. Although some were dismantled, others simply went missing. Two have yet to be found.


Between the fall of the Soviet Union, and 2006, the International Atomic Energy Agency has recovered more than three hundred orphan sources in Georgia.


And Finally…

At least, if you are dealing with an orphan source, it can be found using radioactive detection equipment. As Dr Obbard pointed out, this particular needle in the haystack was crying out, “Here I am!”


But there is plenty that is, potentially, just as dangerous that has no distinctive signature. If the pellet lost in the Australian desert had been a different toxic substance, such as a deadly nerve agent, Dr Obbard fears it might never have been found.


It sounds like the kind of scenario we writers of thriller fiction are likely to come up with, knowing the incredibly high stakes will make for a page-turning story.


And praying to all that’s holy it never becomes a reality.


This week’s Word of the Week is illaudible, from the Latin illaudabilis, and meaning deserving of no praise. An obvious antonym when you think about it, but not one I’ve heard used, although it has been around since 1589. I have often wondered if someone can be ruth, as opposed to ruthless, or ept as instead of inept.


  1. Yes, a very scary event. As you say, the scarier part is that these types of things happen all the time. Now, with nuclear waste, we DELIBERATELY lose it...

    1. Indeed, Michael. That, I fear, is a whole 'nother story!

  2. What a sobering post. Thank you for such thorough information.

  3. Looks to me as the outline for your next thriller! Fascinating, frightening, and foreboding.

  4. When I heard about the deadly pellet gone missing, I figured it would be easy to detect. What I worried about was who would get to it first. With all those orphan sources and broken arrows about, now I am scared that maybe no one is even bothering to look. Yikes!! Riveting writing as usual, Zoe! FromAA