Nuclear radiation contamination...

[Externet]

Hi.

What happens to common materials in the vicinities of a nuclear accident where neighborhoods have to be evacuated, decontaminated, cleaned ?

Is it like a -say house- got 'sprayed' with what?;  the wind brought what and deposited it where? towards it -or the wind has no effect like in electromagnetic radio waves, not carried/deflected by wind- ?

The decontamination being obviously more extensive near the initial accident site,  how deep does it reach ?  Is it skin deep as if paint would be scraped off, it would produce a considerable improvement, or is it deep into concrete, wood structures, soil, plants, trees, water in creeks ?  What is the change experienced by those common irradiated materials and the emissions they produce towards everything else ?

Any good analogies explaining it are also welcome.

[mathematic]

The major problem is that radioactive materials (fallout) settle on soil, etc.  For soil, the material can leech into the ground, so surface cleaning would not be enough.  These radioactive materials emit radiation which ca be very damaging to living things.

[swansont]

Contamination is the radioactive atoms, not the radiation. Wind can affect particulates, droplets and vapor.

[Externet]

Thanks, gentlemen. 

So the contamination occurs by migration of the leaked radioactive atoms that get deposited on other materials nearby a 'perforated/leaky' container of radiactive elements.  As I understand you.  A hermetic vessel containing a ruptured radioactive atoms vessel stops contamination. OK.

[Sensei]

One of Uranium-235 fission products is Caesium-137. It is member of I group of elements with just one valence electron, which violently reacts with water, and its salts are very well soluble in water, forming Cs⁺ ions. Plants, animals and humans, consume directly or indirectly contaminated water and this way Caesium-137 ends up in human body where it will sooner or later decay, perhaps eventually causing unpredictable mutation or cell damage.

Caesium-137 decay modes are explained in this article:

https://en.wikipedia.org/wiki/Caesium-137#Decay

Other Uranium-235 fission products are Barium-141 and Strontium-90. They are not so well soluble in water, but replace Calcium in bones ("bone seeker"), leading to bone cancer and Leukemia.

Article about Strontium-90 contamination of the environment:

https://en.wikipedia.org/wiki/Strontium-90#90Sr_contamination_in_the_environment

 

Edited December 16, 2019 by Sensei

[mathematic]

23 hours ago, Externet said:

Thanks, gentlemen. 

So the contamination occurs by migration of the leaked radioactive atoms that get deposited on other materials nearby a 'perforated/leaky' container of radiactive elements.  As I understand you.  A hermetic vessel containing a ruptured radioactive atoms vessel stops contamination. OK.

It stops contamination.  However radiation from the contents will be dangerous.  That is why permanent safe storage is a problem.

[John Cuthber]

On 12/15/2019 at 10:51 PM, swansont said:

Contamination is the radioactive atoms, not the radiation. Wind can affect particulates, droplets and vapor.

It's usually a small effect, but some of the problem is caused by neutron activation .

 

[MigL]

Not necessarily that small, John.
I remember in 3rd year Uni, sending a piece of metal ( for the life of me, I don't recall what it was ) to a nearby reactor, to sit in the core and be irradiated for about a week.
When it came back, we took  radiation readings of the shielded sample through a collimator shield to determine half-life, and other properties of the NA product.
This was a piece of heavy metal, and it emitted copious amounts of radiation for several weeks, but I think even air and water are capable of neutron activation. I would imagine that when they decommission a reactor core, it isn't just the fuel rods that are radioactive waste, but also quite a bit of the process and support structure.

[swansont]

10 hours ago, MigL said:

This was a piece of heavy metal, and it emitted copious amounts of radiation for several weeks, but I think even air and water are capable of neutron activation.

Regular water is pretty difficult via straight absorption. You need two absorptions to get to tritium, and three to get from O-16 to O-19. Yes, there can be deuterium and O-18 already present, but they don't comprise much of the water.

What happens in Oxygen is a proton ejection, producing radioactive Nitrogen. But that decays back into Oxygen with a half-life of about 7 seconds, so it's not really a contamination issue. Once the neutron source is gone, you'll have minimal radioactivity if you wait about a minute.

 

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I would imagine that when they decommission a reactor core, it isn't just the fuel rods that are radioactive waste, but also quite a bit of the process and support structure.

The iron is a big problem.  Also Cobalt.