Heat Transfer

[catseye747]

Does anybody know why thorium is better than uranium as far as heat transfer is concerned?

[Astronuc]

Does anybody know why thorium is better than uranium as far as heat transfer is concerned?

Thermal conductivity of Th is 54 W/m-K, and the of U is 27 W/m-K. I believe this is a room temperature.

Th has slightly lower atomic mass than U do it would offer less resistance to phonon conduction.

Th-Th bond length = 359.5 pm
U-U bond length = 277 pm

But -

http://www.webelements.com/webelements/elements/text/Th/xtal.html
Space group: Fm-3m (Space group number: 225)
Structure: ccp (cubic close-packed)
Cell parameters:
a: 508.42 pm
b: 508.42 pm
c: 508.42 pm
α: 90.000°
β: 90.000°
γ: 90.000°

http://www.webelements.com/webelements/elements/text/U/xtal.html
Space group: Cmcm (Space group number: 63)
Structure: orthorhombic
Cell parameters:
a: 285.37 pm
b: 586.95 pm
c: 495.48 pm
α: 90.000°
β: 90.000°
γ: 90.000°

I suspect that the orthorhombic crystal with different lengths in all three dimensions plays the biggest role in the lower thermal conductivity of U as compare to Th, which has a closed packed cubic structure.