A European Commission report released in draft form yesterday says that there are many potentially huge and expensive problems with the safety of the majority of nuclear plants operating in the European Union.
"On the basis of the stress test results practically all [nuclear plants] need to undergo safety improvements," says the leaked draft. "Hundreds of technical upgrade measures have already been identified."
This survey was produced in response to the Fukushima accident in Japan last year.
It puts the cost of the safety upgrades at a total of between €10 and €25 billion, or €30 million to €200 million for each reactor.
134 nuclear reactors are in operation in 14 EU countries, of which 111, at 47 plants, have over 100,000 people living within a radius of 30km.
Most worryingly, the report finds that four reactors, located in two different nations, have less than one hour available to restore safety functions if electrical power is lost.
At the other extreme, four countries operate additional safety systems fully independent from the normal safety measures and located in areas well-protected against external events. A fifth nation is considering that option.
The draft report notes that two member states have still not provided information, but does not identify them.
The UK government commissioned its own report on existing British reactors in the wake of the Fukushima disaster, which gave them the all clear.
However the EU report points out that most UK reactors do not have an alternative control room that could be used in the event that the main one became unsafe.
A DECC spokesperson commented that there was no evidence that British nuclear reactors were unsafe, adding that "the Government is committed to the principle of continuous improvement".
The final version of the European report is to be published later this month, and the Commission will make its recommendations shortly afterwards, including proposing laws on insurance and liability to "improve the situation of potential victims in the event of a nuclear accident".
Environmental campaigners pointed out that, although it is comprehensive and devastating, the report misses out further risks in crucial areas, such as ageing technology, terrorist attacks or human error.
"If this exercise was serious, the Commission should be recommending the closure of unsafe or ageing reactors," said Rebecca Harms, co-president of the Greens/European Free Alliance at the European Parliament.