美国有线新闻 CNN 美国华盛顿州核废料隧道坍塌 初步检查未造成核泄漏（在线收听）

Earlier this week, there was a cave-in at a tunnel in Washington state. No one was hurt but officials scrambled to fix that quickly because it's part of the Hanford Facility, a nuclear waste site. The collapsed tunnel was covered in eight feet of soil. It was built during the Cold War as a place to put rail cars contaminated with nuclear waste.

They've been used to produce plutonium, a fuel for nuclear weapons. In fact, some of the material from the Hanford site was used in the atomic bomb dropped in Nagasaki, Japan, in 1945, leading to its surrender that ended World War II.

Plutonium is incredibly toxic to humans. It can cause lung and bone cancer among other things. So, when the cave in was discovered, the 3,000 workers at the facility were told to shelter in place. There were concerns that contamination could spread through the air.

Leaks have happened at this facility before, but a spokesman says the tunnel collapse is a first. The section was sealed in the mid-1990s, and workers don't know how it would have caved in. Initial tests showed there's no evidence of a radiation leak or that workers were exposed to it.

The U.S. Department of Energy plans to fill in the tunnel with clean soil and the effort to clean up the site, which started in 1989, will continue.

SUBTITLE: The One Thing.

DAN SIMON, CNN CORRESPONDENT: The one thing you need to know about nuclear waste is that it is incredibly difficult to store. It needs to be far away from human reach and protected in a way so that it can't be leaked into the environment. That's because nuclear wastes can be radioactive for thousands and thousands of years.

Nuclear waste has been piling up in the U.S. for decades, but there's no permanent solution for it. It's stored across more than 30 states at more than 100 different sites. And that worries industry critics who feared that it could be vulnerable to a terrorist attack or natural disaster.

Politicians for years have been trying to figure out a better solution to store nuclear waste, but it's become a thorny issue, because after all, nobody wants a nuclear waste site in their backyard.