TerraPower today submitted its formal construction permit application to the Nuclear Regulatory Commission for the Natrium reactor demonstration project—a milestone submission for the nation’s first commercial advanced reactor of its kind.

TerraPower officials said last week to expect “dirt moving” at its Wyoming site come June—and for operations to begin there as early as 2030—as it advances plans to build new nuclear in the United States. But 40-plus pages of initial commentary from the Nuclear Regulatory Commission, in the form of a preapplication readiness assessment report, may slow TerraPower’s plans.