It has been five days since authorities found out a dangerous radioactive capsule was missing in Western Australia, but search efforts to find the tiny device across a 1,400-kilometre distance are ongoing.
Here's what we know about the capsule and the efforts to retrieve it.
How was it lost?
The capsule was packaged and transported from the Rio Tinto Gudai-Darri mine site on January 11 and was delivered to a depot in the Perth suburb of Malaga by a third party on January 16, over a distance of 1,400km.
But authorities and Rio Tinto say they weren't notified until January 25 when the container was unpacked.
Lauren Steen, Radiation Services WA general manager, says under the standard protocol, the capsule would normally be secured in highly protected housings and would be subject to testing including vibration, heat and high impact.
Ms Steen says while “anything’s possible”, the industry has strict protocols and it would be very surprising if the company involved hadn’t followed them.
“To be honest we’re still scratching our heads,” she said.
“I think it’s a bit of a wakeup call to all companies about the serious nature of the radioactive sources that they have on site.”
Simon Trott, Rio Tinto Iron Ore's chief executive, says a Geiger counter was used to "confirm the presence of the capsule inside the package" before leaving the site.
Who is searching for it?
A multi-agency incident management team is scouring the search area with specialised equipment.
The search is being led by the state's Department of Fire and Emergency Services.
Mr Trott says the company has offered their "full and ongoing support" in searching for the device.
"We have completed radiological surveys of all areas on site where the device had been, and surveyed roads within the mine site as well as the access road leading away from the Gudai-Darri mine site."
Finding a tiny capsule on a 1,400 kilometre path
Considering the search spans about 1,400km, Darryl Ray, DFES Acting Superintendent and Incident Controller, says the department has brought in specialist equipment.
“What we're not doing is trying to find a tiny little device by eyesight,” Mr Ray says.
“We're using the radiation detectors to locate the gamma rays using the meters that will help us then locate the small device.”
Dale Bailey, professor of medical imaging science in the Faculty of Medicine and Health at the University of Sydney and Royal North Shore Hospital, has likened the search to "finding a needle in a haystack".
"Radiation detectors on moving vehicles can be used to detect radiation above the natural levels but the relatively low amount of radiation in the source means that they would have to "sweep" the area relatively slowly," Professor Bailey says.
But Ms Steen, who is the Radiation Services WA general manager, says despite its tiny size the chance it would be found was “pretty good”.
“If it’s fallen off on that road, if they’re doing a grid-style search it’s pretty likely we’ll be able to get a signal on the radiation monitor and hopefully find it,” she says.
How big is the capsule?
It's about 6mm in diameter and 8mm long, so it really is small.
The lost capsule is a density gauge, commonly used in mining and forms part of a level sensor.
The dangers of getting too close
WA Chief Health Officer Andy Robertson says the capsule emits both beta and gamma rays.
"If you were to stand one metre [away] … you would be receiving about the equivalent of 10 chest x-rays," Dr Robertson says.
He says having it close could cause skin damage, including burns and if it was kept long enough, it could have impacts on the immune and gastrointestinal systems.
“We strongly discourage people from picking it up. Certainly don't put it in a pocket. Don't put it in your car. Don't put it on your sideboard, because it will continue to radiate,” Dr Robertson says.
Authorities are urging anyone who encounters the capsule to stay at least five metres away and report it to the Department of Fire and Emergency Services.
What happens next?
Authorities say it could take weeks to finish covering the potential search area, and even then, there's no guarantee it will be found.
The capsule has a half-life of 30 years, which means it will be somewhat radioactive for the next 300 years, according to Professor Bailey.
Deputy Premier Roger Cook is calling for a review that looks into how the device was lost.
"I understand there was stringent arrangements in place to protect and track this particular capsule … but the fact that it's missing is very concerning," he said.
"This is a very dangerous material and we want it to be recovered as soon as possible."
