CARLSBAD, N.M. (AP) – The U.S. Energy Department and its contractors have been working for nearly three years to reopen the federal government’s only underground nuclear waste repository following a radiation release, but more needs to be done.

A preliminary review of the readiness effort at the Waste Isolation Pilot Plant identified 21 issues that need to be resolved before operations can start at the southern New Mexico facility.

Officials also highlighted another 15 issues that can be addressed as waste disposal work resumes.

State officials are also inspecting the repository this week and must sign off before any work begins.

The repository has been shuttered since February 2014, when a drum of inappropriately packed waste burst thanks to a chemical reaction. The radiation release contaminated a significant portion of the disposal area.