[backhoe]

Appreciate the further info.
Re: Liquid sodium? The little I recall from chemistry years ago is that it is only slightly less nasty than metallic potassium or lithium...

[drmatt]

Yep, sodium, which is very volatile when exposed to air or water. Called the Liquid Metal Fast Breeder Reactor (LMFBR). The French made the most progress with this concept, building a prototype (Phoenix) and a full-scale reactor Super Phoenix). They abandoned their LMFBR program after many operational problems. The Japanese have built one LMFBR (Monju, I think), but it also has had problems, including an accident with a sodium leak.