An in-reactor test facility has been designed and built at The Ohio State University Research Reactor to evaluate the static and dynamic performance of nuclear reactor in-core sensors in environmental and neutronic conditions comparable to those expected in a high-temperature gas reactor. The primary objective for design and construction of this facility was to evaluate the performance of prototype constant-temperature power sensors. The facility can test sensors and materials over a wide range of temperatures up to 800°C, over a range of Reynolds numbers that can be varied to evaluate thermal-dynamic response, and at a reasonable neutron flux value that can be oscillated nearly 7% (up to 100 Hz eventually) to deterministically evaluate sensor transfer functions. Testing has demonstrated that this facility safely performs its desired functions with the current limitation of a 50-Hz maximum neutron flux oscillation speed.