The US Department of Energy’s high temperature reactor research and development program – Progress as of 2019

•The High Temperature Gas-Cooled Reactor is a relatively mature technology; deployable within a decade.•US Department of Energy sponsorship of HTGR technology research and development is resulting in the retirement of significant risks confronting deployment.•Extensive testing confirms that modern TRISO and graphite grades meet designer requirements.•Alloy 617 has been approved by the ASME for nuclear construction up to 425 °C.•Design and high fidelity fuel core analysis tools are being developed and benchmarked.•Significant gains have been made in the advanced reactor regulatory framework. The modular high temperature reactor is a leading candidate for near-term deployment of an advanced reactor concept. The US Department of Energy supports the development of high temperature reactors through qualification of fuels, materials, and analysis methods that exploit the capabilities of the national laboratories (mainly Idaho, Oak Ridge, and Argonne) to generate the fundamental fuel, material, and core behavior data needed to support design and licensing efforts by vendors. Industrial vendors of high temperature reactor concepts provide input to the R&D program and engage in the design of the systems, structures, and components that are unique to their designs. Although there is considerable variation in the plant designs being developed, they all exploit the properties and behavior of the TRISO fuel, material, and analysis methods being tested in the DOE qualification programs. This paper summarizes the goals and recent progress of the Department of Energy’s Gas-Cooled Reactor research and development campaign and how it supports a wide variety of industrial efforts to deploy high temperature reactors to serve modern energy markets.