"In the meantime, the security of installations and checks on staff have been stepped up twice, but of course the details are unpublishable," she said in response to an enquiry.

Germany's 19 nuclear plants, which supply one third of the country's electricity, have been assessing safety intensely since the September 11 attacks on the United States.

As Germany has pledged support for the subsequent U.S. action against the Taliban in Afghanistan.

The spokeswoman said the industry wanted to preempt exaggerated fears but at the same time did not want to make light of possible risks, which also applied to other European countries with a high proportion of nuclear energy.

France relies on nuclear for three quarters of its power needs, Belgium for 60 percent and Sweden has a 45 percent share.

Replacing nuclear energy in the 500 billion kilowatt hour market with other energy sources such as coal would be more expensive and harm the environment, she said.

This would result in clashes with Germany's declared political target to reduce greenhouse gases emissions.

COMMISSION POINTS TO SECURITY RISKS

Her remarks came in the context of a preliminary report on recommended safety enhancements presented by a group of atomic scientists to environment minister Juergen Trittin this week.

Trittin, who commissioned the report in the wake of the September 11 events, has said nuclear plants could be switched off if there were signs of possible attacks.

The group, called the national commission on nuclear reactor safety (RSK), said there was only limited protection against deliberate suicide attacks as in the U.S.

Because only new plants were equipped to withstand military fighter plane crashes, it recommended the improvement of anti-aircraft defence systems as a measure to reduce risks.

Trittin this week commissioned further analysis of necessary physical enhancements to the plants' structure and of possible uncontrolled nuclear reactions.

The RSK had found that if endangered plants closed immediately, there would still be a risks of high radioactive contamination because the removal of fuel elements would take several months and container capacity was limited.

The Social-Democrat/Green government coalition has said the September events will not speed up German plans to phase out nuclear energy by the early 2020s.