From missing seismic devices to insufficient emergency systems, Europe's nuclear power plants face hundreds of problems requiring billions in new investment, a European Union report said Tuesday.

EU-sponsored stress tests conducted on 134 reactors point to a myriad of potential safety hazards, notably in Britain, France and Spain, according to a report obtained by AFP. But it does not go as far as recommending the closure of a single plant.

In the report, the European Commission estimates the cost of improving nuclear safety across the continent "in the order of 10-25 billion euros" ($13-$32 billion), and wants all upgrades to be closely monitored and then finalised by 2015.

The report is to be officially released by Energy Commissioner Guenther Oettinger on Thursday.

The recommendations, which will be put to European Union leaders for approval at an October 18-19 summit, are based on stress tests carried out on the heels of Japan's Fukushima disaster in March 2011.

With 111 European reactors located in built-up areas -- with more than 100,000 people living within 30 kilometres -- "the EU must learn the lessons of Fukushima to further reduce the risk of nuclear incidents in Europe," the report says.

The 25-page document was drafted with the participation of the 14 EU nations that operate nuclear power plants, as well as Lithuania, Switzerland, Ukraine and Croatia. The tests simulated safety in case of floods, earthquakes and airplane crashes when "normal safety and cooling functions" are shut down.

A separate study looking at the risk to a nuclear plant in the case of terror attacks is also under way.

On the basis of the stress tests, "practically all nuclear power plants need to undergo improvements as hundreds of technical upgrade measures have been identified," it said, lamenting that measures agreed after the accidents at Three Mile Island and Chernobyl are "still pending in some member states."

It notably cited the case of 10 reactors where on-site seismic instrumentation has yet to be installed. In some 50 others seismic instruments needed to be upgraded.

The presence -- and state -- of quake measuring instruments was one of 11 key requirements identified by nuclear experts.

The 19 power plants assessed in France, Europe's largest nuclear nation, were given poor marks on five to seven of those chapters, notably for lacking safety equipment in the case of severe flooding or a severe quake.

The French plants however are equipped with hydrogen "recombiners" to prevent hydrogen explosions. This is not the case in 10 British plants and in five of the six Spanish ones.

The 12 German plants on the other hand were slammed for failing to fully implement "severe accident management guidelines".

And two power plants in Finland and Sweden were criticised for having no automatic backup safety system in the event of a power cut.

But in a first response Greens MEP Yannick Jadot said the tests did not go far enough.

He called for a far wider inquiry into "the threat of fire, explosions, a plane crash, malicious behaviour, human error, a plane crash or a combination of several of these."