Tiny radioactive capsule lost in Australian outback found by side of 1,400km stretch of road

A tiny radioactive capsule that was lost in the Australian outback for more than two weeks and posed a “significant public health risk” has been found by the side of the road.

The 8mm by 6mm capsule, which fell from a secure device on a truck that was travelling from a Rio Tinto mine site in the Pilbara region of Western Australia to Perth, was found south of the town of Newman.

The Australian defence force is now verifying the small radioactive device by its serial number. It is being stored at a secure location in Newman, before being transported to Perth on Thursday, inside a lead container to shield people from radiation.

The radioactive capsule was part of a gauge used to measure the density of iron ore feed at the mine in the state’s remote Kimberley region.

A 20-metre exclusion zone has been established where the device was found, just a short distance from where it began its 1,400km journey to Perth. Authorities will now survey the area for any contamination.

WA’s chief health officer, Andrew Robertson, said an investigation had been launched to determine how the device was lost. If negligence is proved then charges may be laid.

“I have responsibility as the chair of the radiological council to actually investigate and if required, prosecute offences under the act,” Robertson said.

“We have a number of authorised officers who are doing that. Our radiation health branch, within the Department of Health, is conducting that investigation and they will be looking at all aspects of this event.”

Robertson said he was not aware of any injuries or people exposed to radiation. “It does not appear the device has moved,” he said. “It appears to have fallen off the truck and landed by the side of the road. It is remote enough that it is not near any major community.”

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Health authorities had warned that standing within a metre of the capsule would be equivalent to receiving 10 Xrays in an hour. They warned people not to touch or approach the capsule if found.

The Department of Fire and Emergency Services commissioner, Darren Klemm, said the device was found using specialist radiation detection technology.

It was initially detected by staff inside a car that was travelling at 70km/ h past the capsule. A handheld radiation device was then used to find the exact location on the ground.

The WA emergency services minister, Stephen Dawson, praised everyone involved in the “relentless search” over the last six days.

“When you consider the scope of the research area, locating this object was a monumental challenge,” he said. “The search groups have quite literally found the needle in the haystack.”

According to WA authorities, the capsule was packaged on 10 January, transported offsite on 12 January, and the casing it was contained within arrived in Perth on 16 January. It wasn’t until nine days later, on 25 January, that it was discovered missing when the package was unpacked for inspection.

It is believed a bolt securing the lead-lined gauge containing the capsule worked loose somewhere on the journey – potentially shaken loose by the vibrations of the truck – and the capsule fell through a hole left by the missing bolt.

Last week, Robertson defended the state government’s decision to wait before informing the public, saying the mine and depot had to be searched and excluded, and the route confirmed.

“It is unusual for a gauge to come apart like this one has,” he said on Friday.

The general manager of Radiation Services WA, Lauren Steen, said capsules like these are commonly used industrially as fixed radiation gauges, which measure the density and flow of materials. They are widely used in the mining, and oil and gas industries.