On the compatibility of liquid sodium as heat transfer fluid for advanced concentrated solar thermal energy systems

The reaction of metallic sodium with a large excess of sodium and potassium nitrate salt mixtures was studied at temperatures up to 873 K. Reactions were carried out in 316 stainless steel (316SS) vessels to ascertain the extent of corrosive action that would take place if a leak developed in a sodium-to-nitrate heat exchanger employed in a solar thermal, central receiver power plant. The reaction was exothermic, producing sodium nitrate, sodium oxide, and nitrogen gas. A black residue of chromium depleted steel was also found. Heat exchanger damage due to a pinhole leak was estimated by injecting sodium through 316SS capillary tubes immersed in the salt mixture at 873 K. To determine the extent of damage to adjacent material, experiments were designed so that the sodium, which was injected through the capillaries, impinged on INCOLOY® 800 or 316SS targets.

D. E. Audette

Papers

The interaction of elemental sodium with molten NaNO3-KNO3 at 873 K