|
Gumby
Fishnologist


Registered: 06/13/01
Posts: 26,656
|
Question about the reactor meltdown in Japan
#14163732 - 03/22/11 09:57 AM (12 years, 11 months ago) |
|
|
I initially read that the reactors in Japan were using radioactive cesium as their fuel rods. I'm now reading that radioactive iodine is showing up in Tokyo's drinking water and in Iceland. Why iodine? Is the cesium decaying to iodine?
|
koraks
Registered: 06/02/03
Posts: 26,691
|
Re: Question about the reactor meltdown in Japan [Re: Gumby]
#14163777 - 03/22/11 10:11 AM (12 years, 11 months ago) |
|
|
No, cesium is not used as nuclear fuel. The nuclear fuel is mostly uranium dioxide, and possibly up to about 5% plutonium oxides to recycle nuclear weapons if MOx fuel is used, which decays into a variety of stable and unstable elements. Radioactive iodine and cesium are among those elements. If the fuel assemblies remain intact, cesium and iodine (along with various other elements, including the short-lived but also radioactive N16, which continues to be a local risk to workers in the direct vicinity of the reactors) remain locked into the fuel elements and cannot escape to the environment. However, if the zircaloy cladding of the fuel elements overheats and ruptures or otherwise degrades (as happened in Fukushima), these radioactive elements can escape into the environment. The reason that especially cesium and iodine are mentioned in reports on nuclear incidents is that they pose particular health hazards. While radioactive iodine is readily absorbed and stored by the thyroid gland, cesium is chemically similar to potassium and tends to be stored easily in plants (including vegetables). Hence, both of these elements pose a particular health hazard, as they are either stored in the body where they keep decaying, continuously radiating the body, or they end up in our food and cycle through the body while emitting hazardous radiation. Radioactive strontium is often mentioned in this respect as well, as it behaves in a similar way as calcium and is therefore stored in bones and teeth.
Edited by koraks (03/22/11 10:16 AM)
|
Gumby
Fishnologist


Registered: 06/13/01
Posts: 26,656
|
Re: Question about the reactor meltdown in Japan [Re: koraks]
#14163821 - 03/22/11 10:23 AM (12 years, 11 months ago) |
|
|
Ah ha! That makes perfect sense. I always thought that they used uranium and plutonium, so I was very confused when I read that there was radioactive cesium in the reactor cores; I'd never heard of them using that before. I was also under the assumption that uranium decayed directly to radium for some reason. I thought I had a decent understanding of radioactive decay but it turns out I'm kinda in the dark on this one.
|
koraks
Registered: 06/02/03
Posts: 26,691
|
Re: Question about the reactor meltdown in Japan [Re: Gumby]
#14163912 - 03/22/11 10:43 AM (12 years, 11 months ago) |
|
|
Dude, that's no shame. I've been researching nuclear technology and nuclear disasters in particular for over 5 years now, and I only begin to realize how little I understand of the underlying physics. Thank God for wikipedia to fill in all the blanks!
|
Seuss
Error: divide byzero



Registered: 04/27/01
Posts: 23,480
Loc: Caribbean
Last seen: 23 days, 1 hour
|
Re: Question about the reactor meltdown in Japan [Re: koraks]
#14164546 - 03/22/11 01:05 PM (12 years, 11 months ago) |
|
|
A few more minor points.. you hear about the cesium and iodine because they are the elements that the body will absorb that cause the most harm. Xenon is another very common byproduct of fission, but has a very short half life. It is important because it is a gas and increases the pressure inside the reactor. (It also absorbs free neutrons like a sponge, helping to stop nuclear fission.)
-------------------- Just another spore in the wind.
|
|