[juliennakache]

From a link shared in a thread below:

“High-temperature properties such as the volumetric storage density, viscosity and transparency are similar to water at room temperature. The major advantages of molten salts are low costs, non-toxicity, non-flammability, high thermal stabilities and low vapor pressures. The low vapor pressure results in storage designs without pressurized tanks (Fig. 1). Molten salts are suitable both as heat storage medium and heat transfer fluid (HTF). In general, there is experience with molten salts in a number of industrial applications related to heat treatment, electrochemical treatment and heat transfer for decades.”

I don’t know anything about this but it does seem that things are not as clear cut as your comment made it seem.

ref: https://onlinelibrary.wiley.com/doi/10.1002/cite.202000137

EDIT: From ChatGPT 3.5:

“ One of the most commonly used molten salts in nuclear reactors is a mixture of lithium fluoride (LiF) and beryllium fluoride (BeF2), commonly referred to as FLiBe. FLiBe is used as both a coolant and a neutron moderator in some types of nuclear reactors, such as molten salt reactors (MSRs) and some advanced small modular reactors (SMRs).

FLiBe has several advantages as a coolant in nuclear reactors, including its good heat transfer properties and its ability to operate at high temperatures without evaporating. Additionally, FLiBe is not highly corrosive to many materials commonly used in reactor components, which can help reduce maintenance and replacement costs.

However, FLiBe does have some potential disadvantages, such as its relatively high viscosity, which can make it more difficult to pump and circulate, and its high melting point, which can increase startup times for reactor systems. Additionally, FLiBe can be corrosive to some materials, such as aluminum and some types of steels, so care must be taken in selecting materials that are compatible with FLiBe.”

[credit_guy]

The reactor that Gates talks about (Natrium) uses sodium as moderator and coolant. In other words, the uranium fuel is submerged in a pool (literally, a pool) of liquid sodium. There are some pipes that circulate the liquid (and very hot) sodium to a separate place, where it heats up a secondary circuit of molten salt. That molten salt then goes on to heat some water and make it steam, which then drives some turbines and generate electricity. Or that molten salt can be left molten for a number of hours, as some form of energy storage solution.

So, the molten salt does not get in contact with the nuclear fuel in any way in this design.

There are other designs where this happens, and especially, there are designs where the uranium (or thorium) is itself part of the molten salt. Even Gates's company, Terrapower, has such a design in the works. But the Natrium reactor is not that.