Key Points
- Authorities are searching for a radioactive capsule that fell off a truck in Western Australia.
- The capsule is used in radiation gauges.
- A warning has been issued about the potential for skin burns or radiation sickness from the capsule's rays.
Authorities have launched an investigation to determine how a tiny but potentially deadly radioactive capsule got lost as it was transported from a West Australian Rio Tinto mine to Perth.
An urgent search continues for the 8 by 6 millimetre unit that is believed to have fallen off the back of a truck on its 1,400 kilometre journey from Newman to a depot in the Perth suburb of Malaga.
What is the capsule, and what are the exposure risks?
The small silver cylinder is a 19-becquerel caesium 137 ceramic source commonly used in radiation gauges.
Western Australia chief health officer, Andrew Robertson has said the unit emits the equivalent of having 10 X-rays in an hour and members of the public should stay at least five metres away.
La piccola capsula contenente cesio-137 radioattivo è stata smarrita durante il trasporto tra un sito minerario a nord di Newman e le parti nord-orientali di Perth tra il 10 e il 16 gennaio. Credit: Department of Fire and Emergency Services WA
Long-term exposure could also cause cancer, however, experts say the capsule cannot be weaponised.
"Our concern is someone will pick it up, not knowing what it is, think this is something interesting (and) keep it," Dr Robertson said.
"If it were kept long enough and they were exposed long enough, they could also have some acute effects, including impacts on their immune system and the gastrointestinal system."
Where are teams focusing their search?
The Department of Fire and Emergency Services have teams with handheld radiation detection devices and metal detectors along a 36km stretch of the busy freight route.
Superintendent Darryl Ray said they were concentrating on populated areas along the Great Northern Highway north of Perth.
"What we're not doing is trying to find a tiny little device by eyesight" he told reporters on Saturday.
"We're using the radiation detectors to locate the gamma rays using the meters."
Authorities are also using the truck's GPS data to determine the exact route the driver took and where it stopped after it left the mine on or about January 10.
They are hampered in their efforts by a lack of equipment and have called on the Commonwealth and other states to urgently provide more, including units that can be fitted to a vehicle.
There are also concerns the solid capsule may have already become lodged in another vehicle's tyre and potentially be hundreds of kilometres away from the search area.
How is the capsule thought to have fallen off the truck?
It is believed a screw worked loose inside the large lead lined gauge it was contained in and the unit fell through a hole left by the missing fastener.
Rio Tinto said it contracted an expert radioactive materials handler to "package the capsule and transport it safely" to the depot and was not told it was missing until Wednesday.
Dr Robson said it was packed in accordance with the radiation safety transport and regulations inside a box bolted onto a pallet.
"We believe the vibration of the truck may have impacted the integrity of the gauge, that it fell apart and the source actually came out of it," he said,
"It is unusual for a gauge to come apart like this one has."
An investigation will look at the handling of the gauge and capsule at the mine site, the transport route used and the procedures at the depot in Perth after it arrived on 16 January.
Police have determined the incident to be an accident and no criminal charges likely.
A radioactive substance health warning remains in place.
