Physical Insights

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Sodium as a reactor coolant

with 2 comments

I have a quick question for the readers.

We often hear from the anti-nuclear crowd that molten Sodium metal, often used as a coolant in fast-spectrum reactors, “explodes when exposed to air”.

Now, anyone with a basic familiarity with chemistry can tell you that a sufficient quantity of Sodium will explode when in contact with water, and molten liquid sodium especially so.

But how reactive is molten Sodium in contact with air?

We know that solid Na is reasonably stable on contact with air, and it can indeed be handled, cut weighed and so forth, both in industry and in the laboratory, in an air atmosphere, although it is generally handled as much as possible under an inert atmosphere where possible so as to prevent oxidation.

Solid Sodium certainly is not explosive or pyrophoric in contact with air.
Is liquid Sodium explosive or pyrophoric in contact with air?

Can anyone provide any credible, useful references on the topic?

Written by Luke Weston

July 29, 2007 at 1:05 pm

Posted in reactor technology

2 Responses

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  1. Liquid Na is explosive when it comes in contact with air and boils violent when in contact with water, but in liquid metal cooled reactors, the reactors are not pressurized. Meaning that they are at atomspheric pressure. Using natural convection to transport the heat through the reactor. So there is a very little chance that the Na could leak in to air or water and as long as the Na does not boil.

    heath

    October 2, 2008 at 4:32 am

  2. Well, I wouldn’t say that liquid sodium is “explosive” when it comes into contact with air.

    It can certainly explode in contact with water, but most any high temperature molten metal will “explode” if you pour water on it.

    I think much of the fear and distrust of sodium stems from fear of sodium-water interaction inside a sodium-primary steam generator… but if this is such a concern, then why not use a sodium reactor to heat helium or nitrogen as the secondary coolant, or air, to drive a Brayton cycle? For that matter, why not make the fast reactors entirely gas cooled?

    Luke Weston

    October 3, 2008 at 2:21 am


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