The mining giant Rio Tinto has been forced to issue an apology to the people of Western Australia, after loosing a capsule containing a small amount of the radioactive isotope caesium¹³⁷ while it was being shipped across the state earlier this month. The capsule served as a radiation source for a device which was able to measure the density of iron within ore samples, which was being transported between the Gudai-Darti Mine, to the north of Newman and the state capital, Perth, a distance of 1400 km, by a specialist contractor brought in by Rio Tinto to undertake the job. The device was inspected at Gudai-Darti and seen to be safe on 12 January 2023, but when inspected in Perth on 16 January is was found that a gauge, one of its four mounting bolts, several screws, and the caesium¹³⁷ capsule had gone missing, apparently shaken loose by the vibration of the truck.
The missing capsule is described as silver in colour, 6 mm in diameter and 8 mm long, small enough to raise concerns that it could be caught in the tread of a car tire. The radiation it emits has been described as equivalent to 10 medical X-rays per hour, not threatening to anyone simply driving past, but potentially harmful to anyone remaining within 5 m of the capsule for any length of time, who could potentially suffer burns or even radiation sickness, with the potential for harm to anyone directly handling the capsule being quite high. Authorities in Western Australia are searching for the missing capsule using portable radiation survey meters, which can be mounted on vehicles, and which should be able to detect the capsule from a distance of about 20 m. This method should be able to detect the capsule if it has remained on or close to the road along which it was transported, although if it has moved from this route, for example by being caught on another vehicle, then the task will become much more difficult, and the danger of members of the public having been exposed to harmful levels of radiation much higher.
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