WASHINGTON, July 30  A one-sentence provision buried in the Senate’s recently passed energy bill, inserted without debate at the urging of the nuclear power industry, could make builders of new nuclear plants eligible for tens of billions of dollars in government loan guarantees.

Lobbyists have told lawmakers and administration officials in recent weeks that the nuclear industry needs as much as $50 billion in loan guarantees over the next two years to finance a major expansion.

The biggest champion of the loan guarantees is Senator Pete V. Domenici of New Mexico, the ranking Republican on the Senate Energy Committee and one of the nuclear industry’s strongest supporters in Congress.

Senator Jeff Bingaman, Democrat of New Mexico and the energy bill’s author, has long argued that nuclear power plants do not need federal loan guarantees. Mr. Bingaman said that the industry was over-interpreting the provision and that it would provide loan guarantees for only the most innovative power plants.