ALBUQUERQUE, N.M. (AP) — The U.S. Department of Energy and the operators of the nation’s only underground nuclear waste dump said Monday they are making plans to allow specially trained workers to enter the site for the first time in weeks after more than a dozen employees were exposed to low levels of radiation during a mysterious leak.

Officials acknowledge they are in uncharted territory in responding to something that has never happened since the Waste Isolation Pilot Plant opened in 1999. The site is important to the nation’s efforts to clean up decades of Cold War-era waste, and administrators are eager to resume operations once they are convinced it’s safe to do so.