Seismic Engineering of a Horizontal, Compact High Temperature Gas Reactor

Boston Atomics have proposed a radical redesign of the high temperature gas reactor by first integrating essential reactor components including the reactor vessel, steam generator, and helium circulator into a unified unit and second by rotating the longitudinal axis of the unit from vertical to the horizontal. The integration and the horizontal reorientation of the reactor components drastically reduces the height of the reactor building, resulting in an increase in the power density, lower overnight capital cost, and an accelerated construction schedule. The innovative horizontal design necessitates analysis and design studies across multiple disciplines including nuclear, mechanical, and structural engineering, which are being pursued now as part of a DOE-sponsored ARC-20 project. This paper discusses work completed to date on the structural and earthquake engineering of the horizontal, compact high temperature gas reactor (HC-HTGR), with a focus on characterizing its seismic response from the plant level (i.e., building + soil domain) to individual structures (e.g., reactor building), systems (e.g., integrated reactor primary system), and components (e.g., core barrel), down to the fuel-block assemblies inside the reactor core. Effective strategies to mitigate the impact of the seismic load case are identified and a clear pathway to standardization is presented.