ABSTRACT
Fluoride Salt Cooled High Temperature Reactors (FHRs) are important to the world as a potential future primary electricity source, with a very high potential that the present fleet of aging Light Water Reactors (LWRs) could be replaced by FHRs. As both the fuel and coolants for FHRs are suitable for very high temperature use (well in excess of 1000 °C), the limiting factor in achieving the highest possible FHR core outlet temperatures and thus thermal efficiency is the availability of compatible structural alloys. Nickel based alloys are candidate materials for high temperature structural applications where they excel in retaining strength, creep and oxidation resistance at high homologous temperatures. There is an extensive body of information on the corrosion of materials in molten fluoride salts as a result of the work performed at the Oak Ridge National Laboratory (ORNL) on fluoride cooled reactors in the 1950s and 1960s. However, very little data is available on alloys for performance in molten fluoride environments at temperatures greater than 750 °C. Furthermore, the effect of alloying elements on the resistance to molten fluoride environments is not known. This study presents preliminary data on the corrosion behavior of selected experimental alloys in 46.5 LiF-11.5 NaF-42.0 KF (FLiNaK).
INTRODUCTION
Fluoride Salt Cooled High Temperature Reactors (FHRs) are important to the world as a potential future primary electricity source, with a very high potential that the present fleet of aging Light Water Reactors (LWRs) could be replaced by FHRs. As a class of reactors, FHRs provide a non-carbon based source for high power density electricity generation and have attractive performance and safety attributes. FHRs can provide lower cost, high efficiency, large-scale electrical power due to their higher thermal efficiency, low-pressure, passive safety, and the elimination of offsite power or cooling water.1 The excellent heat transfer characteristics of liquid fluoride salts enable passive safety at almost any power scale, small modular reactors to high power reactors, and consequent economies of scale. FHRs potentially have improved efficiency, economics, waste production, and water usage characteristics than either water or helium cooled reactors. In addition, small, modular FHRs can be used as a cost- effective, local process heat source for the production of domestic oil shale based gasoline, and to enable efficient hydrogen production. FHRs employ high-temperature ceramic fuel, fluoride salt as the primary coolant, and a low-pressure, pool type primary system configuration. Several countries including France, EU members, Russia, China, Japan, Korea, and the US, are cooperating on Molten Salt Reactor and FHR technologies through the Generation IV International Forum (GIF) Process.2 Other countries including Czech Republic, England, Italy, India, Australia, and Canada have additional supportive technology development efforts.
