18 C.F.R. § 4.83
Cancellation and loss of priority
(a) The Commission may cancel a preliminary permit after notice and opportunity for hearing if the permittee fails to comply with the specific terms and conditions of the permit. The Commission may also cancel a permit for other good cause shown after notice and opportunity for hearing. Cancellation of a permit will result in loss of the permittee's priority of application for a license for the proposed project.
(b) Failure of a permittee to file an acceptable application for a license before the permit expires will result in loss of the permittee's priority of application for a license for the proposed project.