A LITTLE BIT LOST | RADIATION MONITORING AND ALARA
radioactive needle in a haystack
Finding a
Deployment of a modified radiation detector in the back of a car travelling at 70 kph was key to locating a radiation source lost on a 1400 km stretch of desert highway
A TINY RADIOACTIVE CAPSULE THAT was lost while in transit in Western Australia has been successfully located by the emergency services. The device involved was a 19 GBq caesium 137 source bound in a ceramic matrix and encapsulated in stainless steel. It was just 6mm by 8mm and had been lost somewhere on a 1400 km road trip between the Rio Tinto mining company’s Gudai-Darri iron ore mine north of Newman in the Pilbara area of Western Australia, and Perth. Such sources are commonly found in the mining industry
where they are used within level sensors and other similar devices. The steel prevents beta emission but allows gamma penetration which is detected to give a measure of density and/or flow rates of materials. In this instance it was being used at the Gudai-Darri mine site to measure iron ore feed in the crushing circuit of the plant. With a half-life of just over 30 years, this type of
radioactive source might be expected to have a service life of about 15 years although regulatory requirements mean
it must be regularly tested. There are thousands of similar radioactive sources in use across Australia, however, this particular device was being transported to Perth for repair.
The capsule was packaged by a specialist radioactive
materials handler on 10 January, transported offsite on 12 January and the casing that contained it arrived in Perth on 16 January. It was discovered that the capsule was missing over a week later, on 25 January, when the package was opened for inspection. It is believed it had fallen through a bolt hole within a secure device that had been attached to the transport truck. Once alerted, the authorities launched a massive search for the device in a ‘needle in a haystack’ mission to recover the source.
Head out on the highway The operation, led by the State’s Department of Fire and Emergency Services, spanned hundreds of miles from the outback to metropolitan Perth. U
Above: The radioactive capsule was located by the side of the road in the Pilbara region
www.neimagazine.com | March 2023 | 29
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