The Energy Department has granted compact fast reactor developer Oklo Inc. a permit to build a small nuclear reactor at the Idaho National Laboratory.

Oklo, which will announce the landmark development Tuesday, is the first non-light water power reactor design to receive a site use permit, effective for the lifetime of the plant.

The permit is a critical milestone on the path toward deployment of Oklo’s 1.5-megawatt Aurora plant, which company co-founders Jacob DeWitte and Caroline Cochran unveiled at an invitation-only event in Washington, D.C., on Nov. 7, and later announced more widely on Dec. 2.

That kind of event is new territory for nuclear: Oklo wanted “to channel a little bit of Apple-type vibe” and build up excitement for the plant concept, said DeWitte, Oklo’s chief executive, in an interview ahead of the permit announcement. The unveiling featured signature cocktails, each bearing a miniature copper “heat pipe” reminiscent of the Aurora’s heat transport system.

“The system itself is designed to build on the really tremendous legacy of metallic fuels that were developed in this country for decades,” DeWitte said at the event. The Aurora could generate both usable heat and electricity, run for at least 20 years on one load of fuel and operate without the need for water, DeWitte said.

Oklo is the first company to complete the new site use permit application process, which the Energy Department’s Idaho Operations Office established about two years ago. The project is subject to environmental analysis under the National Environmental Policy Act, a process to be led by the Nuclear Regulatory Commission.

The site use permit comes after Oklo entered into a memorandum of understanding in 2017 with the Energy Department — something that Edward McGinnis, then principal deputy assistant secretary of the Office of Nuclear Energy, told members of a House Energy and Commerce subcommittee in May 2018, though he did not offer specifics at the time.