FLiNaK

LiF-NaF-KF

Moderators & Coolants

Density: 2.09 g/cm³

Lithium fluoride–sodium fluoride–potassium fluoride eutectic salt (46.5-11.5-42.0 mol%). Used as a secondary coolant and heat-transfer fluid in MSR designs.

Composition

Nuclide / Element	Fraction
Lithium (natural)	0.232500
Sodium	0.057500
Potassium (natural)	0.210000
Fluorine	0.500000

Code output

MCNP

c FLiNaK (46.5LiF-11.5NaF-42.0KF mol%)
c Density: 2.09 g/cm3 (use -2.09 on cell card)
c Natural Li (7.59% Li-6, 92.41% Li-7)
m22    3006.80c  0.017647  $ Li-6
       3007.80c  0.214853  $ Li-7
      11023.80c  0.057500  $ Na-23
      19000.80c  0.210000  $ K (natural)
       9019.80c  0.500000  $ F-19

Notes

Eutectic melting point ~454°C. Unlike FLiBe, FLiNaK typically uses natural Li since it serves as a secondary (non-fuel-bearing) coolant where tritium production is less critical.

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