NaK Coolant: Difference between revisions

From Citizendium
Jump to navigation Jump to search
imported>Carl Jantzen
(Copied page NaK from Wikipedia)
 
imported>Carl Jantzen
(de-wikipediaed, and re-organized to emphasize the coolant aspect)
Line 1: Line 1:
'''NaK''' (often pronounced as such, rhyming with "sack") is an alloy of [[sodium]] (Na) and [[potassium]] (K), and particularly one that is liquid at room temperatures. It is a commercially available material in various grades. NaK is highly reactive with air or water, and must be handled with special precautions. Quantities as small as one gram can be a fire or explosion risk.
'''NaK Coolant''' is an alloy of [[sodium]] (Na) and [[potassium]] (K) used as a coolant in nuclear reactors. It is particularly useful in these situations because it remains liquid at room temperature and is commercially available in various grades. NaK is highly reactive with air or water, and as a consequence must be handled with special precautions. Quantities as small as one gram can be a fire or explosion risk. Use of [[lead]] or pure sodium, the other materials used in practical reactors, would require continual heating to maintain the coolant as a liquid. Use of NaK overcomes this. NaK is used in many other heat transfer applications for similar reasons.


[[CAS registry number]]: 11135-81-2.
The Soviet [[RORSAT]] radar satellites were powered by a NaK-cooled reactor. Apart from the wide liquid temperature range, NaK has a very low [[vapor pressure]], important in the absolute vacuum of [[Outer space|space]]. Some of the coolant has leaked and these NaK droplets constitute a significant [[space debris]] hazard.


==Physical properties==
==Physical properties==
Alloys with between about 40% and 90% potassium by weight are liquid at room temperature. The mixture with the lowest melting point (the [[eutectic]] mix), consisting of 78% potassium and 22% sodium, is liquid from &minus;12.6 to 785 °C, and has a density of 866&nbsp;kg/m³ at 21°C and 855&nbsp;kg/m³ at 100°C.<ref>{{cite web | title=BASF Corporation &ndash; Sodium-Potassium Alloy (NaK) | url=http://www.basf.com/inorganics/pdfs/tech_datasheet/NaK.pdf | accessmonthday=September 13 | accessyear=2006 }}</ref>
Alloys with between about 40% and 90% potassium by weight are liquid at room temperature. The mixture with the lowest melting point (the [[eutectic]] mix), consisting of 78% potassium and 22% sodium, is liquid from &minus;12.6 to 785 °C, and has a density of 866&nbsp;kg/m³ at 21°C and 855&nbsp;kg/m³ at 100°C.<ref>{{cite web | title=BASF Corporation &ndash; Sodium-Potassium Alloy (NaK) | url=http://www.basf.com/inorganics/pdfs/tech_datasheet/NaK.pdf | accessmonthday=September 13 | accessyear=2006 }}</ref>
==Usage==
===As coolant===
One notable use is as the [[coolant]] in experimental [[Fast neutron reactor|fast neutron nuclear reactor]]s. Unlike commercial plants, these are frequently shut down and defuelled. Use of [[lead]] or pure sodium, the other materials used in practical reactors, would require continual heating to maintain the coolant as a liquid. Use of NaK overcomes this. NaK is used in many other heat transfer applications for similar reasons.
The Soviet [[RORSAT]] radar satellites were powered by a NaK-cooled reactor. Apart from the wide liquid temperature range, NaK has a very low [[vapor pressure]], important in the absolute vacuum of [[Outer space|space]]. Some of the coolant has leaked and these NaK droplets constitute a significant [[space debris]] hazard.
===In catalysis===
NaK is also used as a catalyst for many reactions, including precursors of [[ibuprofen]].
===As desiccant===
Both sodium and potassium are used as [[desiccant]]s in drying solvents prior to distillation. However, without heating, the solid metal is only able to react at the surface. Formation of crusts of oxide also helps to reduce the reactivity. As a liquid metal alloy at room temperature, the use of NaK as a [[desiccant]] helps to avoid these problems.


==Cited references==
==Cited references==
Line 22: Line 10:
<references/>
<references/>
</div>
</div>
[[Category:Fusible alloys]]
[[Category:Coolants]]
[[Category:Potassium]]
[[Category:Sodium]]
[[Category:desiccants]]
{{alloy-stub}}
[[ca:NaK]]
[[ja:ナトリウムカリウム合金]]

Revision as of 05:00, 30 November 2007

NaK Coolant is an alloy of sodium (Na) and potassium (K) used as a coolant in nuclear reactors. It is particularly useful in these situations because it remains liquid at room temperature and is commercially available in various grades. NaK is highly reactive with air or water, and as a consequence must be handled with special precautions. Quantities as small as one gram can be a fire or explosion risk. Use of lead or pure sodium, the other materials used in practical reactors, would require continual heating to maintain the coolant as a liquid. Use of NaK overcomes this. NaK is used in many other heat transfer applications for similar reasons.

The Soviet RORSAT radar satellites were powered by a NaK-cooled reactor. Apart from the wide liquid temperature range, NaK has a very low vapor pressure, important in the absolute vacuum of space. Some of the coolant has leaked and these NaK droplets constitute a significant space debris hazard.

Physical properties

Alloys with between about 40% and 90% potassium by weight are liquid at room temperature. The mixture with the lowest melting point (the eutectic mix), consisting of 78% potassium and 22% sodium, is liquid from −12.6 to 785 °C, and has a density of 866 kg/m³ at 21°C and 855 kg/m³ at 100°C.[1]

Cited references

  1. BASF Corporation – Sodium-Potassium Alloy (NaK). Retrieved on September 13, 2006.