Nitrogen pumping into a Nuclear Reactor- how does that work

[cloa]

I am sure its easier to pump lots of Nitrogen (easy availability) but how does it improve cooling efficiency?

 

[byrdj]

it doesnot "improve cooling efficiency"

Nitrogen is used to inert the atmoshere in primary containment. In this case to midagate the possiblity of a combustable mixture.

 

[electricpete]

The nitrogen isn't to improve cooling efficiency. It is to displace oxygen to help prevent hydrogen explosion. Hydrogen can be formed by zironium/water reaction at high temperature. Also smaller amounts are formed by radiolitic decomposition of water.

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(2B)+(2B)' ?

 

[cloa]

So the zirconium will become extremely hot due to insufficent cooling of reactor rods and hopefully evaporate all the water and then what will the heat definitely be conducted away and hopeful the radioactivity will fall enough to stop the heat generation. Isn't the nitrogen inflow going to be even more difficult than water, its not much denser than air and get heated and driven out as the reactor chamber is broken at the top. How to seal the top- gas tight. Hideous radiation makes that difficult.

 

[rmw]

Regardless of what produced it, the hydrogen torched off because of the oxygen present. The nitrogen displaces air and hence the availability of oxygen to combine with the hydrogen.

rmw

 

[cloa]

That doesn't the question of how they will keep the nitrogen in the reactor- it only excludes oxygen if its still there.

 

[vpl]

cloa

They are not pumping nitrogen into the reactor vessel. They are pumping it into the structure around the reactor. This structure is normally called "primary containment," but is sometimes referred to as as "drywell" because it doesn't contain water. Around the drywell there is a second structure, sometimes referred to as "secondary containment."

This picture (

http://en.wikipedia.org/wiki/File:Reaktor.svg),

which came from Wikipedia shows the various structures. The reactor vessel (which is a pressure vessel) is in yellow. The primary containment is outlined in orange. Notice that the bottom part, has water in it -- this is sometimes called the "wetwell." The secondary containment, which is where the explosions occurred is the whole building. The upper portion is the gird and panel section that appeared to explode at Fukushima. The place with a "5" looks to be the spent fuel pool. If you look on the NRC's website(

http://www.nrc.gov/reading-rm/basic-ref/teachers/03.pdf)there

is a document that provides additional pictures. On page 16 of that document, there is a nice color cutaway drawing.

The primary containment at a boiling water reactor is normally filled with nitrogen for the reason rmw mentioned. So they're trying to maintain the normal condition.


Patricia Lougheed

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[vpl]

It looks like I should have checked my links before hitting submit. Here's the NRC document I meant to link to.

Patricia Lougheed

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