R&D of Structural Alloy for Molten Salt Reactor in China

Abstract

Structural materials (Alloy N) of molten salt reactor are used to fabricate the reactor vessel, loops, heat exchangers, control rod sleeves, which should have long-term stable properties and enough strength and ductility in multiple extreme environments e.g. high temperature, high pressure, corrosion and neutron irradiation. The choice and evaluation of materials for different reactor components depend on the specific working conditions of the components. For thorium molten salts reactor-solid fueled one (TMSR-SF1), the reactor vessel is filled with argon gas and the outside parts are exposed to the air. It contains a primary loop of FLiBe coolant and a secondary loop of FLiNaK coolant. The outlet temperature is 700 °C, and the core operating pressure is less than 0.5MPa.The calculated total neutron fluence after 20 years’ service is 2.01×1017n/cm2 for the reactor vessel. Based on these working conditions, the different properties of structural materials are considered and evaluated. The most important issues of TMSR-SF1 materials include the supply of materials (their preparation, processing, welding, for example) and their qualification in ASME Code. We review alloy N for TMSR-SF1 including alloy physical properties, creep and rupture life time, thermal stability, corrosion, irradiation performance, as well as reliability evaluation of the weldments and so on.