The definition of a microreactor is ambiguous. But whether your upper cutoff is 10 MW or 20 MW, the Microreactor Applications Research Validation and Evaluation (MARVEL) reactor that the Department of Energy plans to build is, at 100 kW, on the tiny side of micro.

The Department of Energy’s Office of Nuclear Energy is spreading the word about plans to build a tiny microreactor called the Microreactor Applications Research Validation & EvaLuation (MARVEL) project inside Idaho National Laboratory’s Transient Reactor Test (TREAT) Facility and have it in operation within the next three years. INL recently released a video that describes how MARVEL could help researchers and industry partners test, develop, and demonstrate the integration of a microreactor’s heat and electricity output with other technologies.

The Department of Energy launched a 14-day public review and comment period on January 11 on a draft environmental assessment for a proposal to construct the Microreactor Applications Research Validation & EvaLuation (MARVEL) project microreactor inside Idaho National Laboratory’s Transient Reactor Test (TREAT) Facility.

The basics: The MARVEL design is a sodium-potassium–cooled thermal microreactor fueled by uranium zirconium hydride fuel pins using high-assay, low-enriched uranium (HALEU). It would be a 100-kWt reactor capable of generating about 20 kWe using Stirling engines over a core life of about two years.

The DOE proposes to install the MARVEL microreactor in a concrete storage pit in the north high bay of the TREAT reactor building. Modifications to the building to accommodate MARVEL are anticipated to take five to seven months. Constructing, assembling, and performing preoperational testing are expected to take another two to three months prior to fuel loading.