The discovery of a highly radioactive Caesium capsule on a desert highway in Australia: Rio Tinto and the Great Northern Highway

It is said that an 8mm by 6mm silver capsule, without a larger than a coin, is lost on a stretch of a vast desert highway in Australia.

Mining company Rio Tinto issued an apology on Monday saying it was supporting state government efforts to find the capsule, which contains Caesium-137, a highly radioactive substance used in mining equipment.

Rio Tinto said it has checked all roads in and out of the Gudai-Darri mine site in remote northern Western Australia, where the device 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 off the back of a truck trundling along a 1,400 kilometer (870 miles) section of the Great Northern Highway – a distance longer than the Californian coastline.

And there are fears that it may have already been carried further from the search zone, creating a radioactive health risk for anyone who comes across it for potentially the next 300 years.

State authorities raised the alarm on Friday, alerting residents to the presence of a radioactive spill across a southern swathe of the state, including in the north-eastern suburbs of Perth, the state’s capital, home to around 2 million people.

The capsule was put inside a package on January 10 and taken to the Rio Tinto mine site in the morning of January 12.

The vehicle was only unloaded for inspection in Perth on January 25 after it spent four days on the road.

“Upon opening the package, it was found that the gauge was broken apart with one of the four mounting bolts missing and the source itself and all screws on the gauge also missing,” said the Department of Fire and Emergency Services (DFES).

The loss of the Caesium-137 capsule at the Perth Regional Airport is “unusual” according to the Australian Radiological Council

“Exposure to this substance could cause radiation burns or severe illness – if people see the capsule or something that looks similar, stay away from it and keep others away from it too,” Dr. Andrew Robertson, Western Australia’s chief health officer and radiological council chair, said in a statement.

Standing within one meter of the capsule for an hour would deliver 1.6 mSv, more than 17 chest X-rays, according to a company that provides radiation protection advice.

The worst scenario would be a curious child picking up the capsule and putting it in their pocket, according to Ivan Kempson.

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 them to be transported in highly protective cases.

If a person finds a capsule they’re exposed to a constant level of radiation from things around them and the foods they eat, but the concern is the health of the person who finds the capsule.

Handling radioactive materials such as Caesium-137 is highly regulated with strict protocols for their transportation, storage and disposal which comes as a surprise to experts.

Western Australia has no issues with radioactive substances being transported on a daily basis. It said that it was a failure of control measures that had caused the capsule’s loss.

Authorities are attempting to find the device with specialized radiation detection equipment fitted to search vehicles driving slowly up and down the highway in both directions at 50 kilometers an hour (31 miles per hour).

Dale Bailey, a professor of medical imaging science from the University of Sydney, said the slow speed was needed to give the equipment time to detect the radiation.

A radioactive substance risk posed by the Caesium-137 capsule in the Pilbara, Western Australia, of Rio Tinto

Authorities are warning anyone who may come across the capsule to stay at least 16 feet away from it and not to touch it but rather to call the fire and emergency services agency.

“What we’re not doing is trying to find a tiny little device by eyesight. The radiation detector is being used to locate the rays.

Authorities say it might have become lodged in another car’s tire and been carried away or even dispersed by birds, raising fears that it may no longer be within the search zone.

“Imagine if it was a bird of prey for example that picks up the capsule and carries it away from the (original) search area – there are so many uncertainties and it will pose more problems,” said Dave Sweeney, nuclear policy analyst and environmental advocate at the Australian Conservation Foundation.

Caesium-137 has a half-life of about 30 years, which means that after three decades, the capsule’s radioactivity will halve, and after 60 years, it’ll halve again.

Rio Tinto, one of the world’s biggest mining giants, operates 17 iron ore mines in Western Australia’s Pilbara region. The company has caused controversy in the past, including the destruction of two ancient rock shelters at Juukan Gorge, prompting an apology and the resignation of the CEO.

The round, silver capsule — measuring roughly a quarter of an inch in diameter by a third of an inch tall — is posing a radioactive substance risk in the regions of Pilbara, Midwest Gascoyne, Goldfields-Midlands and Perth, officials said.

According to the state’s Department of Fire and Emergency Services, the capsule was packed up on Jan. 10 for transport by road, and the shipment arrived in Perth on Jan. 16.

On the discovery of the X-ray Detector at Rio Tinto, a mining site in the Yukawa Delta – a case study

The company said it had hired a third party to package the device, and was working with that company to figure out what went wrong. Rio Tinto undertook surveys in areas where the device was found as well as roads that went away from the mine site.