Precipitation Strengthened Ni-Based Alloys for Liquid Salt Containment and Transport in Energy Systems

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OPEN 2021
Oak Ridge,
Project Term:
09/06/2022 - 09/05/2025

Critical Need:

Fluoride salt cooled high temperature reactors (FHRs) and molten salt reactors (MSRs) can provide a non-carbon-based source of high-power energy generation and have attractive performance and safety attributes. Because the fuel and coolants for FHRs and fuel-salt/coolant for MSRs are suitable for very high temperatures (well in excess of 1000 °C), the limiting factor in achieving the highest possible FHR and MSR core outlet temperatures and thus thermal efficiency is the availability of compatible structural alloys. Hastelloy® N, the leading candidate MSR structural alloy, performs poorly at temperatures above 700°C. Conventional concentrated solar power (CSP) systems, which currently use a blend of sodium and potassium nitrate salts, are employed in the ~500 to 565 °C temperature range. Their efficiency is limited because nitrate salts decompose at temperatures above 600 °C. Higher temperatures, and consequently higher thermal efficiencies, can be achieved in CSP systems by using chloride or fluoride salts if a suitable alloy can be identified.

Project Innovation + Advantages:

Using a computationally-guided approach, Oak Ridge National Laboratory (ORNL) has developed carbide strengthened alloys in small laboratory-scale trials that show good resistance to corrosion by fluorides but with significantly improved strength and/or creep rupture life at temperatures up to 850°C compared with Hastelloy® N. The team proposes to identify a small subset of alloys, fabricate larger trials, measure salt resistance, and evaluate creep and irradiation resistance to enable alloy composition modifications, down-select the best alloy capable of meeting property requirements, and develop processing and welding techniques to fabricate components using this down-selected alloy. This project will decrease risks associated with new alloy development and significantly accelerate the timeline for commercialization of the structural alloy for use in high-efficiency MSR, FHR, and CSP systems.

Potential Impact:

Carbide-strengthened alloys will likely provide the proper combination of molten salt resistance, creep resistance, and irradiation resistance required for high-temperature FHRs and MSRs.


FHRs and MSRs can provide lower cost, high efficiency, large-scale electrical power due to their higher thermal efficiency, low pressure, passive safety, and the elimination of the requirement for safety-related offsite power or cooling water.


FHRs and MSRs can be used as a cost-effective process heat source for thermochemical hydrogen production that, when combined with biological sources of carbon, can result in carbon neutral gasoline. CSP systems can be used as a cost-effective, renewable power source.


FHRs and MSRs potentially have improved efficiency, economics, waste production, and water usage compared with water or helium cooled reactors and could potentially replace aging fossil-fueled power plants.


ARPA-E Program Director:
Dr. Jenifer Shafer
Project Contact:
Steven Zinkle
Press and General Inquiries Email:
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University of Tennessee

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