Terrestrial Energy USA, Inc.

partnered with

idaho National Laboratory

Investigation of the Structural Integrity and Corrosion Resistance of Surface Treatment on Alloy-709 in a Molten Fluoride Salt Environment, NE-22-28244

YEAR AWARDED: FY-2022

ABSTRACT: The business objective of Terrestrial Energy USA (TEUSA) is to develop, license, construct, commission, and demonstrate the commercial operation of the Integral Molten Salt Reactor (IMSR®) nuclear power plant in the United States within 10 years. TEUSA is located in Charlotte, NC.

While Stainless Steel 316H (SS-316H) is the structural material of choice for use in the IMSR® Core-unit, structural materials with higher temperature creep strength are being sought as an alternative to support higher temperature operation during off normal conditions. Alloy-709 (A709) is currently being code qualified by the DOE Advanced Reactor Technologies (ART) program for inclusion in the ASME Boiler and Pressure Vessel Code, Section III, Division 5 for high-temperature reactors. However, A709 is not optimal for molten salt corrosion resistance, but surface treatments may improve the performance. This project seeks to perform baseline studies on surface-treated A709 for corrosion resistance and mechanical properties to understand long-term corrosion protection when subject to periods of sustained and cyclic loading at high temperatures and its potential use in the IMSR®.

Idaho National Laboratory (INL) is part of the ART team that is developing data to support the A709 ASME Code Case. Extensive creep-fatigue testing and microstructural characterization of A709 have been performed at INL and TEUSA intends to leverage this knowledge to conduct the testing needed.