But the 1979 Three Mile Island accident in Pennsylvania that required an emergency evacuation of the surrounding area -- and a clean up that cost nearly US$1 billion -- still haunts the industry. The scare prompted companies to scrap billion-dollar plants that never provided power.

"I'm cautiously optimistic on nuclear, but public opinion turns on a dime," said Jim Rogers, chief executive of Duke Energy, which is considering building nuclear plants in North and South Carolina.

"One bad event anywhere in the world could impact the future of nuclear," he told reporters at an energy conference.

Other obstacles include high start-up costs of between US$2 billion and US$4 billion per new plant, and nuclear waste.

Ernie Moniz, co-chair of the physics department at the Massachusetts Institute of Technology, said nuclear power could be a top low-emissions solution, but safe disposal of nuclear waste must be ironed out.

Nevertheless, companies are forging ahead with plans to build or provide services to new plants.

The 2005 US energy bill offered loan guarantees and other incentives for building new nuclear plants but investors are cautious, said Dan Reicher, president of New Energy Capital, and former US Assistant Secretary for Energy.

"There is some interest on Wall Street, but I would not consider it deep and broad," he said.

Unless about 50 new nuclear plants are built in coming decades, nuclear could lose its current 20 percent slice of the power produced in the United States, according to the the Nuclear Industry Institute.

The US Department of Energy aims to have about 25 new nuclear plants built by 2020. Duke and 11 other companies have begun the permitting process for 31 new US nuclear plants.

General Electric Co. and Japan's Hitachi Ltd. said on Monday they will pool their nuclear power businesses in part to build new plants.

A private equity analyst on Wall Street said US loan guarantees could help ensure construction of six new nuclear units, or about 6,000 megawatts of capacity, in the next decade. But she said the lengthy permitting and construction process for nuclear could mean it would be a long time before investors see a return.

Reicher said that in a decade the US could have one or two new nuclear power plants. In comparison, he said wind power farms of up to 300 megawatts take only 18 months to build.