Effects of a tiny amount of radioactive material

[Dog Star]

Reading the "nuclear core" thread this was posted....

rpguk said:

I read an interesting article on the Goiânia accident recently. I'll try and dig it out but it's basically the story of a bit of radioactive material from an x-ray machine that ended up at a scrap dealers. Quite a few people came to see it and it didn't end well for them.

Edit to add - I think it was the wikipedia page I read - https://en.wikipedia.org/wiki/Goi%C3%A2nia_acciden...

... which is absolutely incredible.

Now - purely hypothetically and without wanting to seem alarmist - just what would happen if some loons - probably of ths suicide bomber persuasion (cos they are going to die) gets hold of some caesium 137 - lets say a lead container of half a kilo of rice sized pellets and just strolls round London randomly sticking them in peoples shopping bags, dropping them on buses, on tube trains, flicking them in parked car air vents etc. They'd be spread very quickly.

Pure conjecture on my part - but you could pretty well render the place uninhabitable due to hysteria.

[Brother D]

It would be very hard to get hold of significant amounts and transport to the UK without being detected, secondly that incident it was basically a powder, which is obviously much harder to contain. Either way, it would be a massive PITA to deal with the clean-up, especially with the public's (and government's) ignorance with all things nuclear related.

[hairykrishna]

Half a kilo’s a lot. The chances of obtaining that amount, or any significant quantity, transporting it undetected and living long enough to do anything with it are quite small I think.

If you did have some you could dose a bunch of people I suppose and cause some panic. Clean up’s not that difficult though and nowhere would be rendered uninhabitable for any significant length of time.

[bigbob77]

There are easier ways to terrorise and they're already doing them, rather successfully

Why go to so much effort when they're already getting the job done?

[otolith]

That's the kind of radiological source that one might expect to be used in a dirty bomb. The actual impact would be small, but the fear, cost and disruption would be major.

[EagleMoto4-2]

That's a fascinating article. In my line of work much of the things we work with require terminal sterilisation by sending them off to a facility with a cobalt 60 gamma radiation source. This facility is just on some random industrial estate with no real security to speak of.
Having said that the sources themselves are stored in a deep pool so would be very hard to get hold of. We were even lucky enough to be shown the sources giving off a faint blue light under the water. Its interesting to read what effect a small dose of radiation can have on the body. To assure sterility our "products" receive a dose of 25-40kGy.

[jshell]

Particularly in the oil industry, the yards that receive and then store or forward equipment and tooling brought back onshore from the rigs and platforms have detectors on the gates. There is 'NORM' radiation present on many oil reservoirs, so tooling can be contaminated. The gate detectors pick up faint signals of, I think, alpha radiation.

I'd imagine every port and airport has similar in case of illegal import to the UK by individuals carrying small amounts.

[hidetheelephants]

Dog Star said:

... which is absolutely incredible.

Now - purely hypothetically and without wanting to seem alarmist - just what would happen if some loons - probably of ths suicide bomber persuasion (cos they are going to die) gets hold of some caesium 137 - lets say a lead container of half a kilo of rice sized pellets and just strolls round London randomly sticking them in peoples shopping bags, dropping them on buses, on tube trains, flicking them in parked car air vents etc. They'd be spread very quickly.

Pure conjecture on my part - but you could pretty well render the place uninhabitable due to hysteria.

Single pellets of any gamma emitter like that will cause burns to anyone spending much time in proximity but unless they ingest them or have them in pockets(like the Brazilian case) it's unlikely to do anything more longterm. Cause panic yes, but serious widespread harm no. Gamma sources of any strength can be detected from the air with suitable equipment(in some cases from space; you don't want to be near those) so easily rounded up.

[Flooble]

jshell said:

Particularly in the oil industry, the yards that receive and then store or forward equipment and tooling brought back onshore from the rigs and platforms have detectors on the gates. There is 'NORM' radiation present on many oil reservoirs, so tooling can be contaminated. The gate detectors pick up faint signals of, I think, alpha radiation.

I'd imagine every port and airport has similar in case of illegal import to the UK by individuals carrying small amounts.

A determined terrorist would either steal from somewhere already in the UK (like a Hospital or Industrial unit) or would use a yacht and a natural harbour. The fact that we don't see more of this sort of thing happening suggests it is beyond the ability of people who are minded to commit such acts. Or they have determined that it would not cause sufficient headlines for their cause.

[ncaplin]

Let's talk about ionising radiation woo!

hidetheelephants said:

Single pellets of any gamma emitter like that will cause burns to anyone spending much time in proximity but unless they ingest them or have them in pockets(like the Brazilian case) it's unlikely to do anything more longterm. Cause panic yes, but serious widespread harm no. Gamma sources of any strength can be detected from the air with suitable equipment(in some cases from space; you don't want to be near those) so easily rounded up.

Echoing this^ kind of. But the harm depends on a few factors.

Cs-137 is actually a beta-gamma emitter so not strictly gamma and therefore has some other energy properties.

Also remember that the effects of radioactive materials are dependant on two interlinking factors: total dose and exposure time. Then you have the question of doses arising from ingestion (this gives an internal dose) and/or a dose from being in proximity to the gamma irradiation (external dose) which can also have different effects depending on persistence and type of radiation.

If we continue to use the Cs-137 example I can explain how this works for external dose i.e. if someone was to go and chuck some in your pocket. In the context of an experiment:

Say, the dose currently in use for a laboratory experiment is 90μSv/h. This dose is worked out from Cs-137 in a solution mixed into a solid media and acts as a point source. A point source is the continual source of radiation, which has the potential to affect living things that surround it at a specific distance. Note that the unit is given in dose over time and this is super important. Here are some exposure sources and an average total dose they give:

0.1 μSv - Eating a banana
40 μSv - One transatlantic flight
2000 μSv - Head CT scan
50,000 μSv - Annual safe limit for radiation workers
100,000 μSv - The lowest annual dose linked to an increased cancer risk
2,000,000 μSv - Fatal dose starts

If you compare the 90 μSv/h in use in your experiment to the figures above (providing you are standing next to it totally unshielded for an HOUR) it can be likened to a return flight to New York.

This is well under any internationally recognised threshold for damage to human health (imagine how frequently you'd get this dose as an airline pilot).

There are 720 hours in a 30 day month. If you were to stand by the 90 μSv/h source for this entire time, you'd get a dose of 64,800 μSv so just above the annual limit for someone working in a nuclear facility.

Another month spent next to the source and that'll be linked to an increased cancer risk at the low end.

You would have to stand by it for a very, very, long time for it to start causing some serious harm.

So, when you say a tiny amount of radioactive material it really does depend on how much and for how long.

I hope that clears things up a bit!

[llewop]

cut to just the points that made me twitch!

ncaplin said:

Echoing this^ kind of. But the harm depends on a few factors.

Cs-137 is actually a beta-gamma emitter so not strictly gamma and therefore has some other energy properties.

Also remember that the effects of radioactive materials are dependant on two interlinking factors: total dose and exposure time. Then you have the question of doses arising from ingestion (this gives an internal dose) and/or a dose from being in proximity to the gamma irradiation (external dose) which can also have different effects depending on persistence and type of radiation.

If we continue to use the Cs-137 example I can explain how this works for external dose i.e. if someone was to go and chuck some in your pocket. In the context of an experiment:

Say, the dose currently in use for a laboratory experiment is 90 uSv/h. This dose is worked out from Cs-137 in a solution mixed into a solid media and acts as a point source. A point source is the continual source of radiation, which has the potential to affect living things that surround it at a specific distance. Note that the unit is given in dose over time and this is super important. Here are some exposure sources and an average total dose they give: point source is a geometrical concept, you've said it's a continual source - point sources can decay to insignificance, sometimes quite quickly! and you've not mentioned the specific distance for your 90 uSv/h from your source - sorry, personal bug-bear; frequently people quote 'contact dose rates' when what matters is ambient dose rates most of the time


50,000 uSv - Annual safe limit for radiation workers legal limit for workers is 20,000 uSv per year - 'annual safe limit' sounds a bit like 49 is fine, 51 will kill you!

2,000,000 uSv - Fatal dose starts hmm - slightly simplistic and a little lower than the figure generally quoted


There are 720 hours in a 30 day month. If you were to stand by the 90 uSv/h source for this entire time, you'd get a dose of 64,800 uSv so just above the annual limit for someone working in a nuclear facility. actually over 3 times the legal dose limt for a year


So, when you say a tiny amount of radioactive material it really does depend on how much and for how long. the material in the Goiania incident was very dispersible and 'grains' would have had significantly higher contact dose rates than 90 uSv/h

I hope that clears things up a bit!

Apologies for dissecting your explanation, which was mostly fine - force of habit when looking at radiological stuff!

It has just occurred to me you may have been quoting the dose limit for USA? or the quirk of 50 mSv/y being allowable in a single year over 5 years, but the average needs to be below 20 mSv/year (for most of the world).

This thread has reminded me I wanted to go back and read that paper you'd linked to re Chernobyl (I'm sure it was you?) - I'm at home today so may do that!

[hairykrishna]

ncaplin said:

Cs-137 is actually a beta-gamma emitter so not strictly gamma

This is technically correct which, as we all know, is the best kind of correct. However, it's worth noting that there's no such thing as a pure gamma emitter. When people are using Cs-137 they're almost always using it for the Ba-137 gamma.

[otolith]

If the sources are salts of radioactive metals, I wouldn't have thought that it would be hard to powder them. Personally hazardous, no doubt, but that's hardly a major consideration for a lot of terrorists these days. I'd have thought that even metals could be aerosolised in an explosion.

[Fugazi]

hairykrishna said:

This is technically correct which, as we all know, is the best kind of correct.

This is a really interesting discussion, if a little macabre and I've just spent the last hour reading about nuclear accidents. Especially the 'Elephant's Foot' in Chernobyl which reads like something that should only occur in a horror film!

[Vanguard21]

Good film based on these events.

http://www.imdb.com/title/tt0259956/