FLiBe: Difference between revisions
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[[Category:Lithium compounds]] |
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Revision as of 17:10, 17 September 2009
FLiBe is a mixture of lithium fluoride (LiF) and beryllium fluoride (BeF2). As a molten salt it is proposed as a nuclear reactor coolant, and was actually used in the MSRE.
The 2:1 mixture with proportions Li2BeF4 has a melting point of 459°C, a boiling point of 1430°C, and a density of 1.94 g/cm3. Its heat capacity is 4540 kJ/m3, which is similar to that of water, more than four times that of sodium, and more than 200 times that of helium (at typical reactor conditions). [1] The eutectic mixture is slightly greater than 50% BeF2 and has a melting point of 360°C. [2]
Coolant
As a molten salt it can serve as a coolant which can be used at high temperatures without reaching a high vapor pressure. Unlike sodium or potassium which can also be used as high-temperature coolants, it is not flammable and does not react with air or water.
Nuclear properties
The low atomic weight of lithium, beryllium and to a lesser extent fluorine make FLiBe an effective neutron moderator. If only lithium-7 is used, FLiBe also has a low cross section for neutron absorption. Natural lithium also contains lithium-6 which absorbs neutrons producing tritium and alpha particles.
Beryllium will occasionally disintegrate into two alpha particles and a neutron when hit by a fast neutron. This provides a small degree of neutron multiplication.
Applications
In the Molten Salt Reactor Experiment it served as solvent for the fissile and fertile material fluoride salts, as well as moderator and coolant.
Some other designs (sometimes called molten-salt cooled reactors) use it as coolant, but have conventional solid nuclear fuel instead of dissolving it in the molten salt.
See also
References
- ^ http://www.ornl.gov/~webworks/cppr/y2001/pres/122842.pdf CORE PHYSICS CHARACTERISTICS AND ISSUES FOR THE ADVANCED HIGH-TEMPERATURE REACTOR (AHTR), Ingersoll, Parma, Forsberg, and Renier, ORNL and Sandia National Laboratory
- ^ http://www.fusion.ucla.edu/apex/meeting4/5sze0798.pdf FLIBE: WHAT DO WE KNOW?, Sze and Wang, 1998, Argonne National Laboratory
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