In June 2001, the U.S. Department of Energy classified "certain privately generated information concerning an innovative isotope separation process for enriching uranium". Under the Atomic Energy Act, all information not specifically declassified is classified as Restricted Data, whether it is privately or publicly held. This is in marked distinction to the national security classification executive order, which states that classification can only be assigned to information "owned by, produced by or for, or is under the control of the United States Government". This is the only known case of the Atomic Energy Act being used in such a manner.
https://en.wikipedia.org/wiki/Separation_of_isotopes_by_lase...
The United States developed the somewhat related AVLIS process to industrial readiness for the Special Isotope Separation project to produce high-grade weapons plutonium from old reactor fuel. However, it was ready just in time for the end of the Cold War, so it got shut down in 1990.
https://inis.iaea.org/records/r6yew-5nk17
Construction and operation of a Special Isotope Separation (SIS) project using the Atomic Vapor Laser Isotope Separation (AVLIS) process technology at the Idaho National Engineering Laboratory (INEL) near Idaho Falls, Idaho are proposed. The SIS project would process fuel-grade plutonium administered by the Department of Energy (DOE) into weapon-grade plutonium using AVLIS and supporting chemical processes.