What caused radiation leak in New Mexico?

On Thursday a U.S. Energy Department investigation explained how radiation leaked from a New Mexico storage facility.

The Waste Isolation Pilot Plant is supposed to be a tomb for items such as tools and clothing that are contaminated with low levels of radiation.

The container that released the radiation was in a salt mine chamber, a half a mile below ground. The investigation found the ventilation system that was supposed to stop radiation from escaping to the surface leaked because of an inadequate design.

Ten hours passed before workers were alerted. Twenty-one were exposed to radiation.

"After 15 years of continual operation and no, absolutely no detection, it was certainly a wake-up call," said Russell Hardy, who runs a center at New Mexico State University that monitors the plant and can test people for radiation exposure.

CBS News spoke to him in February, 13 days after the leak was detected.

"Certainly as soon as the event happened, we should have been notified," he said.

The exposures were at low levels and no one became ill. But today's report said there had been a "degradation of key safety management programs and safety culture" at the facility including a "reluctance to bring up and document issues" among employees.

At a community meeting last night, the plant's field office manager, Joe Franco, said this: "As I have been saying from the beginning, we continue to hold the safety of our employees and our workers and the public and the protection of the environment as a top priority for us."

A team of workers went back down into the waste facility yesterday. They reported finding no major structural damage to the chamber but they still have not determined precisely what caused the leak and contamination that investigators called "preventable".