A tiny radioactive capsule is missing in Australia. Here’s why people are concerned
It’s like looking for a needle in a haystack – an 8mm by 6mm silver capsule, no bigger than a coin, thought to be lost somewhere along a stretch of desert highway in Australia’s largest state .
Mining company Rio Tinto issued an apology on Monday and said it supported state government efforts to find the capsule, which contained Caesium-137, a highly radioactive substance used in mining equipment.
Rio Tinto said it checked all roads in and out of the Gudai-Darri mine site in remote northern Western Australia, where the rig was located, before a contractor collected it for the journey south to the state capital, Perth.
Authorities believe the capsule, which emits both gamma and beta rays, fell from the back of a truck traveling along a 1,400 kilometer (870 mile) stretch of the Great Northern Highway – a distance longer than the California coastline.
Due to the small size of the capsule and the great distances involved, authorities warn the chances of finding it are slim.
And there are fears that it may have already been carried further from the search zone, creating a radioactive health risk for anyone who encounters it for possibly the next 300 years.
State authorities raised the alarm on Friday, warning residents of the presence of a radioactive spill across a southern part of the state, including in the north-eastern suburbs of Perth, the state capital, home to about 2 million people.
According to authorities, the capsule was placed in a package on January 10 and collected by a contractor from Rio Tinto’s Gudai-Darri mine site on January 12.
The vehicle spent four days on the road and arrived in Perth on January 16, but was only dropped off for inspection on January 25 – when it was discovered missing.
“On opening the package it was found that the meter was broken apart with one of the four mounting bolts missing and the source itself and all screws on the meter were also missing,” the Department of Fire and Emergency Services (DFES) said.
They believe strong vibrations caused by bumpy roads damaged the pack – loosening a mounting bolt that held it in place.
Experts have warned that Cesium-137 can create serious health problems for people who come into contact with it: skin burns from close exposure, radiation sickness and potentially fatal cancer risks, especially for those unknowingly exposed for long periods of time.
Radiation Services WA, a company that provides radiation protection advice, says standing within one meter of the capsule for an hour will deliver about 1.6 millisieverts (mSv), as much as about 17 standard chest X-rays.
Picking up the capsule will cause “serious damage” to your fingers and surrounding tissue, the company said in a statement.
Ivan Kempson, an associate professor of biophysics at the University of South Australia, said the worst-case scenario would be a curious child picking up the capsule and putting it in their pocket.
“It’s rare, but can happen and has happened before,” Kempson said. “There have been some previous examples of people finding similar things and getting radiation poisoning, but they were much stronger than the current missing capsule.”
“We are all exposed to a constant level of radiation from things around us and the food we eat, but the primary concern now is the potential impact on the health of the person who would find the capsule.”
The incident came as a shock to experts who said the handling of radioactive materials such as Caesium-137 is highly regulated with strict protocols for its transport, storage and disposal.
Rio Tinto said it regularly transports and stores dangerous goods as part of its business and hires specialist contractors to handle radioactive material. The small capsule was part of a density meter used at the Gudai-Darri mine site to measure the density of iron ore feed in the crushing circuit, it said in a statement.
Radiation Services WA says radioactive materials are transported daily through Western Australia without any problems. “In this case, it appears to be a failure of the controls that are typically implemented,” it said, adding that it had nothing to do with the loss of the capsule.
Pradip Deb, a lecturer and radiation safety officer at RMIT University in Melbourne, said the loss of the capsule was “very unusual” as Australian safety rules require it to be transported in highly protective cases.
The name of the logistics company used to transport the device has not been released, Rio Tinto said.
Authorities are trying to find the device with specialized radiation detection equipment equipped to search vehicles driving slowly up and down the highway in both directions at 50 kilometers per hour (31 miles per hour).
“It will take approximately five days to travel the original route,” the DFES said in a statement on Monday.
Dale Bailey, a professor of medical imaging at the University of Sydney, said the slow speed was necessary to give the equipment time to detect the radiation.
“Radiation detectors on moving vehicles can be used to detect radiation above natural levels, but the relatively low amount of radiation in the source means they will have to ‘sweep’ the area relatively slowly,” he said.
Authorities warned members of the public not to come within five meters of the device, while admitting it would be difficult to see from a distance.
“What we’re not doing is trying to find a tiny device by sight. We use radiation detectors to detect the gamma rays,” DFES officials said.
But there are fears it may no longer be within the search zone – authorities say the capsule may have become lodged in another vehicle’s tire, carried a greater distance, or even spread by wild animals, including birds.
“Imagine if it was, say, a raptor picking up the capsule and carrying it away from the (original) search area – there are so many uncertainties and it would cause more problems,” said Dave Sweeney, nuclear and environmental policy analyst. advocate at the Australian Conservation Foundation.
“This resource must of course be recovered and secured, but there are so many variables and we simply don’t know what could happen.”
Cesium-137 has a half-life of about 30 years, meaning that the capsule’s radioactivity will halve after three decades, and halve again after 60 years.
At that rate, the capsule could be radioactive for the next 300 years, said Deb from RMIT University.
“Cesium-137 is normally a sealed source – meaning, if it is not broken, it will not contaminate the ground or environment… If the capsule is never found, it will not contaminate or transfer radioactivity to the surrounding land,” added Deb.
Kempson, of the University of South Australia, said that if remains were lost in an isolated area, “it would be very unlikely to have much impact.”
Rio Tinto, one of the world’s largest mining giants, operates 17 iron ore mines in Western Australia’s Pilbara region. The company’s mining activities have caused controversy in the past, including the 2020 destruction of two ancient rock shelters at Juukan Gorge, prompting an apology and the resignation of then-CEO Jean-Sébastien Jacques.