Factbox-Hurdles for Germany's planned nuclear winter reserve

(Reuters) - Germany wants to keep two southern nuclear plants, Isar 2 and Neckarwestheim 2 open in reserve mode beyond their scheduled closure at the end of 2022, to help avoid potential energy shortages in a winter when most Russian gas supply has dried up.

The move will be hard to implement within a coalition government in which the Green Party has to overcome its traditional anti-nuclear scepticism to justify it.

Meanwhile, parts of the pro-business Free Democrats (FDP), as well some of the political opposition are holding out for the return of more regulator nuclear operations, possibly stretching to even more reactors within the shrunken fleet. [POWER/DE]

Here are the pitfalls:

POLITICAL DISCORD

Economy minister Robert Habeck from the Greens stipulated that all three remaining nuclear reactors will still officially go offline by Dec. 31, but Isar 2, operated by E.ON and Neckarwestheim 2, operated by EnBW will be granted standby status until mid-April.

But sector peer RWE's Emsland reactor in the north will close.

"The only reason why the nuclear plant in Lingen in Emsland does not go into reserve operation is the left-wing state association of the Greens in Lower Saxony," wrote the leader of the FDP's parliamentary group leader, Konstantin Kuhle.

Lower Saxony state holds state elections on Oct. 9.

POWER GRIDS WANTED ALL THREE PLANTS TO BE IN RESERVE

Germany's four high voltage power transmission grid operators (TSOs) have stress-tested electricity supply scenarios in a task that provided the background for Habeck's decision.

They had wanted all three, including Emsland, to run longer.

They argued that European power networks are critically tight.

Some 5.1 gigawatts (GW) of power capacity could be missing where the contribution of Germany's two standby plants to flows on the grid would not weigh in with their full capacities of 1.4 GW each that producers maximising output would seek, they said.

Due to grid inadequacies, the two would only be able to provide 0.5 GW to the overall load.

LEGAL REQUIREMENTS

A simple regulation will not be sufficient to seal the deal.

Rather, the nuclear exit law will have to be amended to create certainty for the operators and ward off lawsuits from either side.

OPERATORS ARE LUKEWARM

EnBW and E.ON were less than enthusiastic although they have said the continued operations are technically imaginable.

Both said they will assess the requirement.

(Reporting by Tom Kaeckenhoff and Vera Eckert, editing by David Evans)