Western Australian authorities are scrambling to find a missing radioactive capsule that is a fraction of the size of a 10c coin, conceding it was not found missing until more than two weeks after it left a Rio Tinto mine site.
The 8mm by 6mm capsule is a 19-gigabecquerel caesium 137 ceramic source, commonly used in radiation gauges, and was supposed to be contained in a secure device which had been “damaged” on a truck which travelled from the mine site north of Newman in the Pilbara to a depot in Perth.
Authorities are now searching along the 1,400km stretch of the Great Northern Highway for the capsule, which they warn can cause skin burns, radiation sickness and cancer.
At a news conference on Saturday, Darryl Ray, the acting superintendent for Western Australia’s Department of Fire and Emergency Services, said authorities were largely searching for the capsule at “strategic sites”.
He said an incident management team including the Department of Health and police had been formed.
“We have continued the search on strategic sites along the route that the vehicle had taken, concentrating on sites close to high-population areas within the metropolitan suburbs,” he said. “The search involves the use of radiation survey meters to detect the radiation levels which will help us locate the small device.
“What we are not doing is trying to find a tiny little device by eyesight. We are using the radiation detectors to locate the gamma rays, using the meters, that will help us then locate the small device.
“We have secured the GPS data from the trucking company to determine the exact route and stops that the vehicle has taken on its journey.
“We will continue to use specialist equipment to help us search the remaining known locations ... in particular, the Great Northern Highway between Perth and Newman.”
The WA chief health officer, Andrew Robertson, said there were screws missing from the protective gauge holding the capsule when it was discovered missing.
“These gauges are designed to be robust and to be used in industrial settings where they may be exposed to weather and vibration, so it is unusual for a gauge to come apart like this one has,” Robertson said.
“We are conducting an investigation on all of the circumstances from when it was originally transported from the mine site, the whole of the transport route, and then its handling on arrival in Perth.”
Robertson urged anyone who found the capsule not to handle it.
“People could end up developing redness of the skin and eventually burns of the skin from the beta radiation,” he 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.”
Robertson said the capsule was “most dangerous if it is handled or if it is close to the body”.
“If you are further than five metres away from the source, certainly if you are more than 20 metres away from the source, it will pose no danger to you,” he said. “If it is closer than that, and we strongly discourage people from picking it up, certainly don’t put it in your pocket or put it in your car, don’t put it on your sideboard, it will continue to radiate.
“While you may not have immediate health effects, they can occur relatively rapidly over a short period of time if it is close to the body.
“If you see it [or] identify it, move away from the source, contact 13DFES and report it. We will get somebody out there to have a look at the source and we will use our radiation meters to identify whether it is the source.”
Robertson said officials did not know the date the capsule fell off the truck.
Ray said the capsule was placed on to the pallet on 10 January at the mine site, transited and arrived at the radiation service company in Malaga on 16 January.
“It was not until the 25th, late morning, when they opened it up to reveal that the device had fallen apart, was damaged in transit, and that the actual capsule was discovered missing, which is when authorities were first notified.”
Ray said police had determined the capsule was not taken in a criminal act.
Robertson said specialist equipment had been requested from agencies within the commonwealth, including the Australian Radiation Protection and Nuclear Safety Agency.
“What we are looking for is mobile radiation detection equipment that we can put in a car and then drive at a reasonable speed,” he said.
“But, you know, there are a number of variables here: it could have been knocked further out into the bush, it could have been picked up and carried in a tyre wheel in another direction. We have to look at all of those options.”
Mining giant Rio Tinto confirmed earlier on Saturday that the capsule had come from one of its mining sites.
The company said it had contracted an expert radioactive materials handler to “package the capsule and transport it safely” to the depot.
“Rio Tinto was informed of the missing capsule by a contractor on January 25,” a spokesman said. “The contractor, an expert radioactive materials handler, was engaged by Rio Tinto to handle and package the capsule and transport it safely off site.
“Safety is our highest priority, and we are working with and supporting the Radiological Council, the contractors involved, as well as emergency services to assist in the search.”
• This article was amended on 29 January 2023. An earlier version said the radiation source was 19 becquerels; the correct figure is 19 gigabecquerels
