A 8mm by 6mm pellet containing dangerous radioactive Caesium-137, used in mining operations, has been missing since mid-January, travelling about 1,400km between the remote town of Newman and the northern suburbs of Perth, Australia.
Mining company Rio Tinto apologized on December 30 and said it was working with the state government to find the radioactive pellet.
Due to the small size of the radioactive pellet and the large search area, officials warn the chances of finding it are slim. There are concerns that it may have been carried further away from the search area, posing a health risk to anyone who comes across it for the next 300 years.
Don't know why it's lost?
The equipment was originally planned to be transported by truck from a mine near the town of Newman to the northern suburbs of Perth, a total distance of more than 1,200km.
Due to the tiny size of the radioactive pellet, authorities warn the chances of finding it are slim.
The truck left the Rio Tino mine on January 11 and arrived at the Malaga depot in Perth on January 16. However, it was not until January 25 that Australian authorities received a report from Rio Tino stating that no radioactive pellets had been found during an inventory.
How dangerous are radioactive pills?
Experts have warned that Caesium-137 can cause serious health problems for those exposed to it, including: skin burns from close contact, radiation sickness and the risk of deadly cancer, especially for those who are accidentally exposed to it for long periods of time.
Radiation Services WA, a company that provides radiation protection advice, says standing within 1 metre of a radioactive pellet for an hour would generate about 1.6 millisieverts (mSv), equivalent to about 17 standard chest X-rays.
Picking up the radioactive pellet would cause 'severe damage' to the finger and surrounding tissues of the human body, the company said in a statement .
Ivan Kempson, associate professor of biophysics at the University of South Australia, said the worst case scenario would be for a curious child to pick up the radioactive pellet and put it in his pocket.
"It's rare but it can happen and it has happened before. There have been a few examples of people finding similar things and getting radiation poisoning, but those were much stronger than the missing pellet," Kempson said .
Why is this a strange incident?
The loss has shocked experts, who say the handling of radioactive materials like Caesium-137 is tightly controlled with strict procedures for transporting, storing and handling them.
Rio Tinto said it routinely transports and stores dangerous goods as part of its business and employs specialist contractors to handle radioactive materials. In a statement, the radioactive pellet was part of a density meter used at the Gudai-Darri mine to measure the density of iron ore feed in the crushing circuit.
The WA Radiation Service said radioactive material is transported throughout Western Australia on a daily basis without incident. In this case, there appears to have been a lapse in the controls normally in place.
Pradip Deb, a lecturer and radiation safety officer at RMIT University in Melbourne, Australia, said the loss of the radioactive pellets was " very unusual " because Australian safety rules require them to be transported in highly protective containers.
Rio Tinto said the name of the logistics company used to transport the equipment has not been disclosed.
How does the search process work?
Authorities are trying to find the radioactive pellet using specialized radiation detection equipment equipped to search for vehicles traveling on and off the highway in both directions at speeds of 50 km/h.
Authorities have warned people not to approach the radioactive pellet if it is spotted within five metres, but admitted it would be difficult to see from a distance.
Authorities are trying to find the radioactive pellet using specialized radiation detection equipment.
But there are concerns that the radioactive pellet may no longer be in the search area. Authorities say it may have been trapped in a vehicle's tyre and carried further afield, or even carried away by wild animals or birds.
What happens if the radioactive pellet is not found?
The radioactive substance Caesium-137 has a half-life of about 30 years, meaning that after 3 decades, the radioactivity of the radioactive pellet will decrease by half and after 60 years it will decrease by half again.
'Caesium-137 is typically a sealed source, which means that if it is not broken, it will not contaminate the soil or the environment… If the radioactive pellet is never found, it will not contaminate or transfer radioactivity to the surrounding soil ,' Deb added.
Kempson (University of South Australia) said that if the radioactive pellet was lost in an isolated area, it would be "very unlikely to have much impact".
