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Australians scour desert for dangerous radioactive capsule smaller than a penny

nytimes.com

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Re: Australians scour desert for dangerous radioactive capsule smaller than a penny

#61

Post by pfdietz »

evrydayhustling wrote: post #49
cloudking wrote: post #17

Interview question: can you design a system to safely locate and retrieve the capsule?

I'm kind of surprised that something this radioactive isn't pretty easy to hone in on with a good Geiger counter. Someone with better physics want to enlighten me about ranges and sensitivity?

You wouldn't use a Geiger counter, you'd want to use a gamma ray spectrometer. For example, a sodium iodide crystal doped with thallium (acting as a scintillator, connected to a photon detector) or semiconductor detector (large crystal of Si, Ge, or other materials, preferably of high atomic number.)

The Geiger counter is filled with gas and will not effectively interact with gamma ray photons; the solid state detectors interact much more strongly with them, and (particularly the semiconductor detectors) have very good energy resolution, to spot the particular energy of photons from this particular radioisotope.

Re: Australians scour desert for dangerous radioactive capsule smaller than a penny

#62

Post by toomuchtodo »

leaving wrote: post #56

This is mostly a data analysis job. If the capsule is on or very near the road, a single trip from start to finish with a NaI(Tl) or CsI scintillation counter will find it. Every CBRN team in the world has these, so they have obviously completed the first run at this without finding it. The capsule is not on or near the road. Australia is famous for road trains on the Great Northen Highway. They travel fast and heavy…

You comment is fantastic because it demonstrates we are beyond finding it with a rolling road block and sensors on trucks. This is a recovery operation where you're going to want surveillance for when someone shows up somewhere (medical care provider) with radiation sickness and to start contact tracing. If a human has it in their possession, exposure is ongoing. If it's sitting in a ditch somewhere, maybe it's years before it's found, maybe it's never found (and perhaps buried if and when a torrential rain passes through the area, typically in the upcoming winter months).

Re: Australians scour desert for dangerous radioactive capsule smaller than a penny

#63

Post by skissane »

pfdietz wrote: post #61
evrydayhustling wrote: post #49

Earlier quoted context omitted.

I'm kind of surprised that something this radioactive isn't pretty easy to hone in on with a good Geiger counter. Someone with better physics want to enlighten me about ranges and sensitivity?

You wouldn't use a Geiger counter, you'd want to use a gamma ray spectrometer. For example, a sodium iodide crystal doped with thallium (acting as a scintillator, connected to a photon detector) or semiconductor detector (large crystal of Si, Ge, or other materials, preferably of high atomic number.) The Geiger counter is filled with gas and will not effectively interact with gamma ray photons; the solid state detect…

One of these? https://georesults.com.au/product/radiation-solutions-rs-125...

Or maybe even https://georesults.com.au/product/rs-350-backpack-human-port...

I imagine they are both rather expensive.

Re: Australians scour desert for dangerous radioactive capsule smaller than a penny

#65

Post by cshimmin »

todd8 wrote: post #45
fnands wrote: post #41

Oh, reminds me a of a time some students lost a Polonium source in the physics lab while I was a Masters student. The HoD had them crawling around the building for days with a Geiger counter, but they never found it. Luckily it was a small source and Polonium has a relatively short half-life, but the department had to go through a whole song and dance of declaring an incident.

According to Wikipedia, Polonium is 5000 times more radioactive than Radium (just 0.001g of Po emits the same number of particles as 5g of Ra). It has a half life of just 138 days so in only 4.6 years the missing Polonium will be equivalent in radioactivity to Radium, which is known to cause cancer. This doesn't sound like something that should be treated lightly.

Sure but all that means is that 1g of radium will have the same activity as 0.2mg of polonium. Of course they will also have different decay spectra etc. We don't know how big the source was that the students lost, but I'm guessing that if they just gave up after a few days, it probably wasn't a very high activity. This means either very low mass, or a higher mass but just older so that it's decayed away.

Re: Australians scour desert for dangerous radioactive capsule smaller than a penny

#66

Post by remus »

evrydayhustling wrote: post #49
cloudking wrote: post #17

Interview question: can you design a system to safely locate and retrieve the capsule?

I'm kind of surprised that something this radioactive isn't pretty easy to hone in on with a good Geiger counter. Someone with better physics want to enlighten me about ranges and sensitivity?

I guess it's one of those things where the intensity of the radiation is proportional to 1/d^2.

If you're holding it in your hand it emits enough radiation to be very unhealthy, but as soon as you put some distance between you and it then it becomes very hard to detect.

Re: Australians scour desert for dangerous radioactive capsule smaller than a penny

#67

Post by Symbiote »

dsfyu404ed wrote: post #39
Waterluvian wrote: post #34

Earlier quoted context omitted.

I think finding it is the expensive part.

It pretty much broadcasts its location if you wave the right instrumentation around.

You "just" need to wave that instrument over 1400km of highway, potentially with a 100m+ width if the capsule has been kicked some distance away by a truck tyre.

Re: Australians scour desert for dangerous radioactive capsule smaller than a penny

#68

Post by dalmo3 »

JoeAltmaier wrote: post #47
genmon wrote: post #15

Earlier quoted context omitted.

Because it’s enormously dangerous to stand a meter from, and people near it won’t even know (eg it could have been picked up in a tyre tread so someone is carrying it around), but radiation and therefore ability detect drops according to the inverse square law so it will be hard to find from much further away. And Australia is big.

Again, hyperbole. "the equivalent of 10 X-rays in an hour" People routinely get exposed to that during their normal job. An x-ray is a fraction of a year's natural exposure from the sun. Airline pilots experience this radiation in a few months at work. The numbers matter. This instance, the device hardly matters. Not as much as a national news report anyway. We'd be better off reading about pay disparity or access to…

> People routinely get exposed to that during their normal job.

What jobs you're referring to? Your examples cite years and months but the quoted sentence states "in an hour."

Re: Australians scour desert for dangerous radioactive capsule smaller than a penny

#70

Post by car »

leaving wrote: post #56

This is mostly a data analysis job. If the capsule is on or very near the road, a single trip from start to finish with a NaI(Tl) or CsI scintillation counter will find it. Every CBRN team in the world has these, so they have obviously completed the first run at this without finding it. The capsule is not on or near the road. Australia is famous for road trains on the Great Northen Highway. They travel fast and heavy…

A network of scintillators in every phone would be amazing for finding stuff like this.

That was my first thought too. Do you think it’s physically possible to make a MEMS scintiallation device?

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