As the country struggles to find a place to bury spent nuclear fuel, the Nuclear Regulatory Commission has decided that nuclear waste from power plants can be stored above ground in containers that can be maintained and guarded indefinitely.

The decision, in a unanimous vote of the commission on Tuesday, means that new nuclear plants can be built and old ones can expand their operations despite the lack of a long-term plan for disposing of the waste.

The chairwoman of the commission, who voted with the majority but dissented on certain aspects, said Friday that the vote risked allowing Congress to ignore the long-term problem.

“If you make the assumption that there will be some kind of institution that will exist, like the Nuclear Regulatory Commission, that will assure material stays safe for hundreds or thousands of years, there’s not much impetus for Congress to want to deal with this issue,” the chairwoman, Allison M. Macfarlane, said Friday. “Personally, I think that we can’t say with any certainty what the future will look like. We’re pretty damned poor at predicting the future.”