Planned Irradiation of IN-Pile Steady State Extreme Temperature Testbed

Advanced reactor designs such as high-temperature gas-cooled reactors (HTGRs), molten salt reactors (MSRs), small modular reactors (SMRs), microreactors, and space reactor systems are planned to operate in high prototypic temperatures, which will present limitations on the materials and instrumentation capable of properly operating in such extreme conditions. Limited data are available on survivability at high temperatures under neutron irradiation for candidate fuels, materials, and sensors for these environments. Certifying components for these reactors will require combined effects testing, irradiating components at the prototypic high temperatures expected for different reactor designs. The IN-pile Steady-state Extreme Temperature testbed (INSET) meets this requirement. INSET is a high-temperature material and instrumentation testing vehicle that is scalable to various research reactors to achieve the prototypic temperature levels while exposing candidate samples to prototypic neutron fluences expected in different advanced reactor designs such as nuclear thermal rockets, microreactors, and HTGRs. INSET can currently provide vacuum conditions as well as steady-state temperatures up to 2,000 °C, and it can be exposed to a neutron fluence using research reactors with large irradiation ports. It uses DC power to resistively heat graphite elements to heat sample holders within the experiment containment. Due to the versatile design of INSET, any desired location of the sample or instrumentation can be easily accommodated. The test vehicle was recently updated with a new graphite heating element and internal structures to create a more durable and repeatable experiment. Plans to update INSET to accommodate flowing gas are also being developed. The previous INSET design successfully irradiated samples in the Ohio State University Research Reactor (OSURR) three times, and a fourth irradiation is planned for the summer of 2023 to demonstrate the updated INSET test vehicle before the next phase of material and instrumentation testing.