Urgent public health warning issued over lost radioactive capsule

@defrost Great discussion and addition by the way. I only have one additional comment concerning radon. Radon is produced in a radioactive decay in the ground, and as it is gaseous it usually dissipates into the atmosphere rather quickly, so there is not too much of it near the detector at any given time. As you mention correctly, certain weather condition obviously can trap it near the ground. We usually study urban centers, with lots of asphalt covering the ground, affecting the amount released near the ground and near our detectors. We usually see it during rain, as then the radon in the atmosphere is washed down through the rain and accumulates on top of the ground for a while, which we often see as a strong uptick followed by an exponential decay. I have a coworker that just submitted a paper for review regards modeling this, sorry can't link the work yet. Overall, radon is quite tricky to understand and what you mention seem very reasonable. It would be quite interesting putting a detector for a while in these areas. Nevertheless, the measured amount of radon usually fluctuates on larger scales, maybe hundreds of meters, while the source will create a very localized signal, so it shouldn't cause too much troubles for a search like this.

[1] https://en.wikipedia.org/wiki/Western_Australian_radioactive...

For context, Rio Tinto operations in Mt. Newman are mining iron ore from near surface open pit | mesa deposits; blasting rock with minimal crushing to fit in rail carriages for transport to the ocean ports where ore is crushed smaller, screened and graded (blended) for shipping overseas .. in total some 850 million tonne per annum of iron ore from that region (not just Newman alone).

I'm guessing the guage is for estimating ore density | grade on the fly as rocks tumble through the load out (from the remote operated semi autonomous near robot trucks) into kilometre+ long robot trains.

> Considering they still haven't found it

Yeah, I'm very surprised the search is still on, I'm leaning towards it's well off route in a tire in a truck (or already fallen free) OR some heavily tatted FiFo worker (fly in | fly out) nicked it as a souvenir for the local bikkie clubhouse and hasn't came home from a holiday in Thailand yet .. .

Radon: IIRC there are additions in the Australian AGSO radiometric processing guidelines re: radon removal that derived from work I did levelling out radon smearing back in the 1990s - somewhat out of date these days, but hey, that's the world for you.

There are also potential modifications to the work by Brian Minty | Jens Hovgaard | Bob Grasty using an NASVD to firstly highlight the use of Radon eigenvectors and then to rotate them out of the signal space in the processing pipeline.

I'm guessing (completely w/out context) that perhaps your friend is moving down that path (or perhaps well past and elsewhere, as I said, it's been a while).