* Nuclear supply gap in Germany, Belgium tightens outlook-report
* French supplies should remain secure this winter-RTE
* Severe cold could trigger 5,400 MW in power imports-RTE
By Muriel Boselli
PARIS, Nov 8 (Reuters) - The outlook for European power supplies appear tighter this winter due to hitches in Belgian nuclear reactors and after Germany stopped some reactors in 2011, according to preliminary findings of a European study cited by French power grid RTE.
The full European report, carried out by ENTSO-E, the European lobby for grid operators, is due to be released at the end of the month, RTE said in its own winter report released on Thursday.
Industry observers last month expressed concern over a potential electricity supply crisis this winter because of a tighter nuclear supply scenario in Belgium, Germany and France.
After Germany closed some of its oldest nuclear reactors following the 2011 Fukushima disaster, another big blow to supply were cracks at Belgian nuclear reactors Tihange 2 and Doel 3, which have grounded 2,000 MW when Belgium would typically be a net exporter to France.
Cross-border flows in Europe are meant to even out problems in individual countries. Electricity flows between France and Germany represent capacity equivalent to five nuclear reactors.
RTE, a fully-owned EDF subsidiary, did not elaborate on what could be the consequences of this supply tightness at the European level and instead said French supplies should remain secure this winter under normal weather conditions.
A severe cold patch, with temperatures 6 to 8 degrees Celsius below seasonal averages, would trigger a big jump in consumption and lead to imports of some 5,400 megawatts (MW), a capacity equal to five nuclear reactors but below the country's maximum import capacity.
Central Europe was hit by a cold snap in February when French consumption peaked at 102,100 megawatts (MW), pushing the network to its limits and obliging it to import a record 9,000 MW from its neighbours, including Germany.
On the production side, the grid predicts that between January and March, availability of production tools should be at a similar level than at the same period of 2012.
While France generally has steady power supplies thanks to its 58 nuclear reactors, it lacks flexible capacity - usually generated by gas, coal or oil-fired plants - to meet peak evening-time demand during cold snaps when workers return home and switch on heating and appliances.
France relies heavily on electric heating developed by successive governments to absorb supplies generated by its nuclear reactors. Germany uses mainly gas and fuel oil heaters. (Editing by William Hardy)