After 6 days of searching the route more than 1,400 km with modern equipment, Australian authorities found a dangerous radioactive capsule that was lost.
On January 25, mining group Rio Tinto announced that a tablet containing radioactive cesium-137 (Cs-137) smaller than a coin had been lost in transit, causing Western Australia state officials to devoted all his might to the seemingly “impossible” search mission.
The radioactive pellet was lost on its way from the Gudai-Darri mine in the town of Newman to a warehouse north of Perth city centre. This means authorities will have to scour more than 1,400 km for a cylindrical object about 6 mm in diameter, 8 mm long, only slightly larger than a pea.
Western Australia state officials immediately took action, mobilizing special forces and firefighters to search for the radioactive pellet. Many nuclear science, emergency management, radiation protection experts across the country were also asked to help.
The initial theory was that the truck during transport shook violently, causing the radioactive pellet to fall out of a specialized box and into a hole in the rivet that had loosened and lost. Officials are also concerned that it could fall on the road and get stuck in the grooves of a passing car’s tire, making the search more difficult.
CS-137 is used in mining radiation meters. People not wearing protective clothing standing near the radioactive pellet are at risk of skin irritation or radiation burns. Exposure from standing about one meter away from the object would be equivalent to taking 17 consecutive X-rays.
On January 26, authorities began searching in Perth and around the Newman mine. The next day, they devoted themselves to a search operation and issued a “radioactive hazard” warning, sending a message to the people: “Stay away from this dangerous capsule”.
The search team used a hand-held Geiger-Muller radiometer, capable of detecting radiation within a radius of 20 meters, focusing on the route the truck had traveled, along with urban areas in Perth. .
“We don’t look for radionuclides with the naked eye, but rely on radiation detectors, in the hope that they will lead us where we need to go,” a Western Australian state police spokesman said.
On January 28, a Geiger-Muller instrument detected unusual radiation near the Great Northern Highway. The police gathered forces and search equipment in this area, but no radioactive material was detected.
A day later, the Australian government approved additional resources to assist the state of Western Australia with the search operation. The people running the search began planning the next phase.
According to local media, the equipment provided by the government includes radiation measurement (RPM) ports for people and vehicles passing, commonly used at airports, and gamma-ray spectrometers (GRS), capable of measure the energy distribution of gamma radiation.
Darryl Ray, incident control officer at the emergency agency, said the devices can be attached to cars, allowing searchers to detect traces of radioactive pellets while traveling at speeds of about 50 km/h. “Reviewing the entire 1,400km distance took about five days,” he said.
But by the end of January 31, they still had not identified traces of radioactive pellets.
The good news came on February 1, when staff from Nuclear Science and Technology Australia announced they had found the radioactive pellet at 11:13 a.m. near the town of Newman, two meters from the highway. The site is located about 200 km from the Gudai-Darri mine, so officials believe the radioactive pellet fell from the vehicle before it had traveled far.
“It’s a pretty deserted stretch of road,” Darren Klemm, commissioner of the Fire and Emergency Service, said at a news conference. “When the readings on the radiometer suddenly spiked, the people searching in the car were surprised.”
After checking the device’s serial code, they confirmed it was the missing radioactive pellet. It was found about 74 km from the town of Newman, about 200 km from the mine. Officials said no one appeared to be injured, nor did the radioactive pellet move after it fell on the road.
Associate Professor Nigel Marks from Curtin University in Western Australia hailed the discovery as a “victory of science”.
The chairman of the Australian Radiation Council will investigate the exact cause of the radioactive worker’s disappearance, as well as determine the possibility of wrongdoing by mining group Rio Tinto.
After the radioactive pellet was found, Rio Tinto chief executive Simon Trott said the group would “cooperate fully in the investigation”, adding that the cost of the search would be paid for if the government requested it.
Duc Trung (Theo BBC)