Renewable energy is unlikely to plug the gap left when Scotland's ageing nuclear stations cease production, the first minister has warned.
The UK is examining choices to power its future
But Jack McConnell told a conference in Edinburgh that the Scottish Executive would block new atomic plants until the issue of nuclear waste was resolved.
Delegates also heard a union's calls for new nuclear, to stop rising energy costs from crippling the industry.
The Scottish Greens hit out, insisting nuclear was not economically viable.
Mr McConnell said the government wanted to be confident it could protect future generations from "even the current legacy of nuclear waste."
But he explained that the government also had to consider options for when nuclear power ran out.
He said: "I do not believe it is beyond our abilities to be able to find a sustainable long-term solution to our future energy needs.
"The only way in which that solution can be developed is if we have a genuine debate and discussion that deals with facts and realities and considers all the options on their merits."
Derek Simpson, general secretary of Amicus, claimed the industry and the environment would suffer without moves towards a mix of nuclear power and clean coal technology.
He said rising energy costs were threatening thousands of jobs and he urged the UK Government to come up with a clear energy policy and urgent action to resolve the nuclear waste problem.
"British industry needs certainty. Thousands of jobs depend on it," he said.
However, Green MSP Mark Ballard said calls for more nuclear power stations were based on "misleading claims".
He said: "Nuclear power is only made to look economic because of the assumption that the taxpayers will bail out the companies and foot the bill for managing the waste and other liabilities.
"Rather than weep at the funeral of unsustainable, uneconomic and risky nuclear power, unions should be protesting about the failure of government to properly support the marine energy sector."
The issue of new nuclear power threatens to split Scotland's governing Labour/Lib Dem coalition.
There has been widespread speculation that Prime Minister Tony Blair will back new nuclear power stations as a solution to energy shortages, after a comprehensive UK review of energy policy reports later this year.
However, the coalition executive, particularly driven by its Liberal Democrat members, has said that it will not sanction a new generation of nuclear plants unless and until there is an acceptable solution to the issue of disposing of nuclear waste.