RPT-UPDATE 3-Germany to raise, redefine nuclear safety rules

(Repeats to widen distribution)

* New body to redefine nuclear safety guidelines

* Scenarios include air crashes, attacks and quakes

* Power firms say to cooperate with "ambitious" plan

* RWE says to sue against shutdown plans; E.ON won't sue (Adds RWE plan to sue)

By Stephen Brown and Hans-Edzard Busemann

FRANKFURT, March 31 (Reuters) - Germany said on Thursday it would raise security requirements at its 17 nuclear plants to ensure they can withstand plane crashes and earthquakes, after Japan's nuclear crisis sparked a U-turn in German policy.

Outlining the task of a new safety committee which presents its first findings in May, Environment Minister Norbert Roettgen said safety had to be completely reviewed.

"It's a question of whether safety has to be redefined in the light of new estimates," he told a news conference. "What would happen if an even bigger earthquake hit Germany?"

Experts doubt whether overhauling Germany's oldest nuclear reactors against such scenarios, also including extreme climate change impacts such as drought, would be cost effective, meaning a current moratorium on such plants could be made permanent.

Nuclear power has long been unpopular in Germany and Chancellor Angela Merkel's decision last year to extend the life of nuclear plants was a major factor in her party losing power after 60 years in a prosperous conservative state on Sunday. [ID:nLDE72T07N]

She reversed this after the massive earthquake and tsunami hit Japanese nuclear plants and now believes Germany must exit quickly from nuclear power. She imposed a 3-month moratorium on the oldest seven of Germany's 17 nuclear plants.

Utility RWE (RWEG.DE) said late on Thursday it would lodge a legal complaint against the German state of Hesse for ordering a 3-month shutdown of RWE's nuclear power plant Biblis A as part of the moratorium.

An RWE spokesman said the utility welcomed the planned security checks but said that a provisional stop needs a sound legal basis.

Senior conservatives doubt whether any of these plants dating from before 1980 will ever restart. [ID:nLDE72E0KG]

Germany's nuclear plants are also run by E.ON (EONGn.DE), EnBW (EBKG.DE) and Vattenfall [VATN.UL].

For its part, E.ON said it would not file a lawsuit against being forced to shut off two of its nuclear power plants.

The new reactor safety commission's head, Rudolf Wieland, presented a document at the news conference which said Japan had "clearly underestimated the consequences of natural disasters" on its nuclear reactors.

This meant Germany had to test whether reactors are or can be protected against terrorism, plane crashes and earthquakes, he said, although seismic activity in the region is very muted compared to Japan.

It would also consider the impact of power failures for longer periods rather than just a few hours, Wieland said.

Roettgen said the findings of the physicists, engineers and industry representatives on the commission would form the technical basis for political decisions to be taken by mid-June.

The minister said German power supply would need investments of hundreds of billions of euros in coming decades to cope with the infrastructure required for an accelerated conversion to renewable energy sources such as wind and solar power.

(Additional reporting by Joern Poltz and Peter Maushagen; Writing by Stephen Brown and Ludwig Burger; Editing by Louise Ireland and Richard Chang)