Emergency services are searching for a radioactive capsule which has been lost along a 1,4000-kilometre stretch of road in Western Australia.
The capsule (6mm in diameter, 8mm tall) is round, silver and contains a radioactive substance known as Caesium-137.
This substance is used in mining operations and went missing in transit between a mine site north of Newman and the north-eastern parts of Perth between 10-16 January 2023.
The Government of Western Australia Department of Health said in a statement the capsule cannot be weaponised but it can cause serious health consequences.
People are urged not to touch the capsule.
Department of Fire and Emergency Services (DFES) Chief Superintendent Country North, David Gill, said a search was underway to find the capsule and safely contain it.
“DFES was notified by WA Police on 25 January and is now coordinating the search as the lead agency for hazardous materials,” he said.
“A multi-agency Incident Management Team, comprised of DFES, Department of Health, WA Police and other subject matter experts, are confirming the exact route and stops made during the journey from north of Newman.
“The start and finish of the transportation journey – the mine site north of Newman and the transport depot in the north-eastern suburbs of Perth – were among the locations searched yesterday and today,” he said.
“We are also combing roads and other areas in the search zone.”
Dr Andrew Robertson, Chief Health Officer and Radiological Council Chair, said the immediate focus was to find and safely contain the material to protect the community and to warn the public of the health dangers.
“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,” said Dr Robertson.
“Do not touch or pick it up. The public is asked to report it immediately by calling 13 DFES (13 33 37).
“If you have touched the material, or have been close to it for an extended period, contact your local health practitioner or visit a hospital emergency department and tell them that you think you may have been exposed to radioactive material.
“If you are very close to the material or touching it, the radiation risk increases immensely and could cause serious damage to your health, including causing radiation burns to the skin.”
Authorities speculate the capsule fell through a hole where a bolt had been dislodged after a container collapsed inside the heavy vehicle.
Radiation Services WA General Manager, Lauren Steen, said this scenario is highly unlikely due to the safety measures typically in place for transporting radioactive materials.
“Typically they’re transported in highly protected casing that are subject to a certification verification stage,” Steen told ABC.
“The housing is subjected to rigorous testing for vibrations, heat, high impact.
“If the source is certified and the packaging and the transport requirements … basically make it a very unlikely occurrence.”
Mining company, Rio Tinto, reported the capsule was lost while being transported by a contractor. It is also working with expert radioactive materials handlers to handle and package safely transport it offsite.
The Authorities involved in the search for the radioactive capsule anticipate it could take weeks to cover the potential search area.
Radiation Services WA claim there are thousands of these sources around WA which are used and transported without any issues.
In this instance, however, there was a failure of the control measures typically implemented.
“Radioactive sources are typically highly protected within a source housing,” said Radiation Services WA.
“This protects us from the radiation emitted and protects the source from damage.
“Sources are used commonly for density or level detection in processing plants in the mining and oil and gas sectors. These sources (and housings) are designed to be installed and left in place for 15 years without any attention (apart from regular auditing).
“The housings are certified to be safe when subject to corrosion and vibration and can withstand a fall from 9m, or subject to 800 deg C for 30 minutes, with minimal impact.
“Transporting radiation sources is also subject to strict controls relating to the training of personnel, packaging requirements and controls for safe handling and emergency response.”
Caesium-137 is reported to emit both beta and gamma radiation and has a half-life of 30 years.
“This means that after 30 years, the source will be half of its original activity (in this case, the original activity was 18.5 GBq),” said Radiation Services WA.
“After 60 years, it will be a quarter of its original activity.”
The source is also reported to be in a ceramic form and is double encapsulated in stainless steel.
“The source encapsulation would be to an ISO certified standard – and is known as ‘Special Form’ under transport regulations,” said Radiation Services WA.
“This means that the main risk from these sources is from external radiation only.
“It’s likely this source has decayed from its original 18.5 GBq, but if it was at its full activity, we can calculate some hypothetical dose rates from an ‘unshielded’ source using what is known as a gamma factor or specific gamma ray constant. For Cs-137, this is 0.090 mSv/h per GBq at 1m.
“Therefore, the dose rates from this source will be approximately 1.665 mSv/h at 1 m given the media is telling us it’s unshielded.”
To put the health risk of exposure into perspective, spending an hour from one metre of the radioactive capsule is close to:
A normal amount of background radiation in Australia in a year – which is around 1.5 mSv.
Around 17 normal chest x-rays (at around 0.1 mSv per exposure).
The same risk of dying in a car or workplace accident in any given year. Each are around 1 in 10,000 risk – 2 mSv of radiation exposure also increases your risk of contracting a fatal cancer by around one in 10,000.
The risk with radiation sources dramatically increases within one metre:
At 1 cm, the dose rate will be 10,000 time higher … 16,650 mSv/h (or 16.65 Sv/h).
At 1mm (i.e., if you were to pick the source up with your fingers), the dose rate would be 1,665 Sv/h – this will cause some serious damage to your fingers and surrounding tissues.
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