Molten salts for nuclear cogeneration

The utilization of process heat from a high temperature nuclear reactor for hydrogen production and chemical industry support could be a significant step towards increasing national energy independence and reducing greenhouse gases. For this co-generation, thermochemical process plants should be co-located with a nuclear power plant, but from a safety standpoint they must be separated by a reasonable distance. Molten salts have the potential to be excellent heat transport fluids for the heat exchange loop. Fluoride salts are specifically being considered for these heat transfer applications. However, materials corrosion has been identified to be a problem in molten fluoride salts, particularly at high temperatures. Corrosion tests have been performed to determine the compatibility of a few candidate high temperature materials for the heat transfer loop in a molten alkali fluoride eutectic salt, LiF-NaF-KF: 46.5-11.5-42 mol %, also known as FLiNaK. Generally, higher Cr content alloys experienced higher corrosion due to the propensity of Cr to selectively dealloy and dissolve into this fluoride salt. Additionally, data from three important experiments in the literature dealing with forced convective heat transfer in flowing molten FLiNaK were compiled and re-evaluated. For turbulent flow, in experiments conducted in systems constructed of Inconel alloys, it was determined that FLiNaK salt behaves as a normal fluid and can be modeled using the Dittus-Boelter (DB) correlation within ± 15% accuracy. The DB correlation can thus be used for preliminary calculations in design of the heat transfer equipment for molten FLiNaK.