EU Energy Commissioner Guenther Oettinger said Thursday the cost of necessary improvements at the 145 nuclear reactors in the European Union could be as high as euro25 billion ($32 billion) over the coming years.

A European Union report released Thursday says stress tests carried out in the wake of the March 2011 Fukushima accident in Japan show that almost all the plants need safety improvements. Officials said earlier that the tests did not reveal the need to close any plants immediately.

EU leaders agreed last year to put the reactors through the toughest security checks possible to gauge their ability to withstand accidents and natural disasters.

Oettinger said that `'nearly everywhere" there was potential for improvement to reach the highest level of safety, ranging from ensuring more time to react to an electricity blackout to adding more seismic equipment to detect earthquakes.

`'At least euro10 billion will need to be invested in the EU and possibly up to euro25 billion," Oettinger said.

The report also called for more consistency across the 27-nation EU in assessing and managing safety threats.

`'Hundreds of technical upgrade measures have been identified," the report said. EU leaders will now assess the report at their Oct. 18-19 summit in Brussels to chart the way ahead.

The report criticized the authorities for not taking the latest standards into account to assess risks.

For earthquake and flooding risk, standards now called for an assessment based on occurrences of the past 10,000 years, while many nuclear power plants use a shorter timeframe.

Equipment to fight severe accidents is not stored for quick retrieval in 56 percent of cases, and almost everywhere equipment to alert for earthquakes should be upgraded, or installed.

In case of an electricity blackout, five reactors would not be able to cope for more than an hour without intervention.

European nuclear plants are already regularly checked, but under the stress test system, the checks were toughened up and coordinated across the EU before facing peer review by a multinational teams of experts.