BRUSSELS, Belgium - Immediate safety upgrades costing billions of euros are needed in nuclear power plants "nearly everywhere" in Europe, according to the results of EU "stress tests" released yesterday.

Ordered in the aftermath of Japan's Fukushima disaster in March last year, the Europe-wide tests overall showed "satisfactory" safety, with no need for the immediate closure of a single European Union reactor, the bloc's Energy Commissioner Guenther Oettinger said.

"However, nearly everywhere there is a major potential for improvement," he said

at a news conference. "There is no reason for us to be complacent."

Saying many of the EU's 132 reactors failed even to meet international safety standards, Oettinger confirmed leaked reports that bringing plants up to scratch could cost anywhere between ¤10 billion ($1.16 trillion) and 25 billion.

The stress tests, the commissioner added, were "not a blank cheque", but "an incitement to action" to ensure the highest possible standards are applied soon.

"We would expect these steps to be taken immediately," he said as he urged governments to draw up timetables for action by year's end, with Brussels to review in June 2014 whether plants have been upgraded by then in line with safety requirements.

Oettinger also said he hoped to strengthen Brussels' say in the future on nuclear safety issues by tightening up existing rules next year while also calling for compulsory civil liability insurance.

With 111 European reactors located in built-up areas — that is, with more than 100,000 people living within 30 kilometres — Oettinger recognised that a next step would be to also evaluate risks to populations.

The stress tests, carried out in 15 EU states plus neighbouring Switzerland and Ukraine, aimed to establish whether plants could resist extreme natural disasters such as earthquakes and flooding, as well as airplane crashes.

They found that seismic instruments were either lacking or needed improvement in 121 reactors.

At 81 of the sites checked, equipment for use in the case of severe accidents was not stored in a protected place where it would be quickly available in case of a disaster.