Rio Tinto Ltd (RIO.AX) apologized on Monday for the loss of a tiny radioactive capsule that sparked a radiation alert across parts of the vast state of Western Australia.
The radioactive capsule, believed to have fallen from a truck, was part of a gauge used to measure the density of iron ore feed which had been entrusted to a specialist contractor to transport. The loss may have occurred up to two weeks ago. The capsule is round and silver, 6 millimeters in diameter, and 8 millimeters long.
An emergency hunt for the device, which is about the size of a pea, is underway along the 1,400km (870 miles) route. The capsule contains a small quantity of radioactive Caesium-137, which could cause serious illness to anyone who comes into contact with it. That could include skin damage, burns, or radiation sickness.
Caesium-137 emits potentially fatal amounts of radiation, almost equivalent to receiving 10 X-rays in an hour and prolonged exposure can even cause cancer. It takes Caesium-137 almost 30 years to decay by half.
“It disappears quite quickly, compared to other radionuclides. However, short half-life means it’s quite active,” Hajime Kinoshita, a senior lecturer in materials chemistry at the University of Sheffield in the U.K., told NBC News.
The truck bearing the capsule left the mine on 12 January, arriving in Perth on 16 January, but the capsule wasn’t discovered missing until nine days later when the secure housing was opened on 25 January.
“We recognize this is clearly very concerning and are sorry for the alarm it has caused in the Western Australian community,” chief executive Simon Trott said in a statement.
It is believed a bolt securing the lead-lined gauge containing the capsule worked loose somewhere on the journey – potentially shaken loose by the vibrations of the truck – and the capsule fell through a hole left by the missing bolt.
“Upon opening the package, it was found that the gauge was broken apart with one of the four mounting bolts missing and the source itself and all screws on the gauge also missing,” the emergency services said. “What we’re not doing is trying to find a tiny little device by eyesight,” he said. “We’re using the radiation detectors to locate the gamma rays.”
“Our concern is someone will pick it up, not knowing what it is, think this is something interesting [and] keep it,” Robertson said.
Authorities did not close the road, National Highway 95, over the ordeal, though the emergency department’s incident map showed the entire stretch of road marked in red with a radioactive warning symbol. They have warned people to stay at least 5 meters from it.