High-temperature reactors materials development

Very High Temperature Reactor (VHTR) Survey of Materials Research and Development Needs to Support Early Deployment, INL/EXT-03-004-141, January 31, 2003. 

Regarding the potential to share design and technology development with reactors of other types, a remarkable example is provided by the AHTR, a pre-conceptual system that is part of the U S. Department of Energy Generation IV reactor programme. About 70% of the R D required for the AHTR is shared with that for helium cooled high temperature reactors. This includes fuel development, materials development, and Brayton power cycles. Annex XXVI. 

About 70% of the R D required for the AHTR is shared with that for helium cooled high temperature reactors. This includes fuel development, materials development, and Brayton power cycles ... 

For high-temperature operations, materials, and fuels are key technologies. There is a century of large-scale experience in the use of fluoride molten salts. Aluminum is made by electrolysis of a mixture of bauxite and sodium aluminum fluoride salts at 1000 C in large graphite baths. Fluoride salts are compatible with graphite fuels. A smaller nuclear experience base exists with molten fluoride salts in molten salt reactors. Nickel alloys such as modified Hastelloy-N have been qualified for service to 750 C. A number of metals and carbon-carbon composites have been identified for use at much higher temperatures however, these materials have not yet been fully developed or tested for such applications. 

The favorable properties of the lead coolant and nitride fuel (a feature of some advanced LFR designs), combined with high-temperature stmctural materials, can extend the reactor coolant outlet temperature up the 750—800°C range in the long term (GIF, 2002, 2014), but this will require the development of new structural... 

Carbon-based materials have been shown to be compatible with molten salts at temperatures of 1000°C, and for graphite up to 1400°C. Carbon-carbon composites which are currently being considered for fusion and for high-temperature reactors (e.g., in-core applications such as control rods, straps, etc.) are therefore also an option for the MSR and MSFR. For these materials there are nevertheless uncertainties in the joining technology and large-scale development work and demonstrations would be needed for their application in safety-related components. 

The Oak Ridge National Laboratory, under the sponsorship of the U. S. Atomic Energy Commission, has engaged in research on molten salts as materials for use in high-temperature reactors for a number of years. The technology developed by this work was incorporated in the Aircraft Reactor Experiment and made available for purposes of civilian application. This earlier technology and the new information found in the. civilian power reactor effort is summarized in this part. 

Fusion Reactors. The development of fusion reactors requires a material exhibiting high temperature mechanical strength, resistance to radiation-induced swelling and embrittlement, and compatibUity with hydrogen, lithium and various coolants. One aUoy system that shows promise in this appHcation, as weU as for steam-turbine blades and other appHcations in nonoxidizing atmospheres, is based on the composition (Fe,Co,Ni)2V (30). 

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