Advances in high temperature gas-cooled reactor technology developments and related IAEA activities to support near-term deployment

High temperature gas-cooled reactor (HTGR) is one of the major technology lines for advanced small modular reactors (SMRs) for near-term deployment. The historic operation of pilot or test reactors as far back as the 1970s and subsequent progress of modular HTGR design developments have leveraged the promotion of HTGR technology in the nuclear sector today. Inherent safety, embedded in any HTGR concept, is one of its distinct advantages. Besides, it is expected to meet both electric and non-electric needs. Owing to its high outlet temperature, HTGR is designed to reach higher thermal efficiency than the existing light water reactors (LWRs) and provide process heat applications. The advanced fuel as well as low power density core can provide some additional benefits in terms of safety, however, the power density could also lead to bigger core sizes. There are also several challenges associated with HTGRs, such as manufacturing maturity, supply chain management, licensing, commissioning etc. In this paper, several typical HTGR designs, both pebble-bed design and prismatic design, of different power levels and in different stages of development are described to illustrate their design features and development milestones. Furthermore, this paper briefly describes key programmatic activities carried out by the International Atomic Energy Agency (IAEA) to support Member States’ interested in this technology and its applications.