Specially trained workers are finalizing plans to enter the nation's only underground nuclear waste dump after two separate incidents forced its closure weeks ago, including a leak that exposed more than a dozen workers to low levels of radiation.

Officials with the Waste Isolation Pilot Plant say initial testing shows there's no contamination at an air intake shaft that leads into the mine or at the bottom of the mine's salt shaft.

What remain uncertain are the deep in the repository where plutonium-contaminated clothing, tools and other waste from federal nuclear sites around the country are stored.

Plant spokesman Donavan Mager said Monday the crews will be practicing before entering the mine later this week.

Once they enter, they will continue taking as they get closer to the source of the contamination.