* French reactors undergo yearly and once-a-decade works
* First results of French safety tests published end-2011
PARIS, April 21 (Reuters) - Maintenance periods at EDF's nuclear reactors may be extended slightly when the state-owned utility improves safety at its 19 plants after learning lessons from Japan's Fukushima disaster, its chief executive said.
French nuclear safety watchdog ASN will publish the first results of tests conducted on the country's 58 nuclear reactors by the end of 2011 as part of a European push to improve safety.
"This (safety changes) might lengthen a little maintenance periods," EDF CEO Henri Proglio told reporters on Thursday.
French nuclear reactors undergo annual one-month closure periods for refuelling and minor maintenance operations as well as once-a-decade full check-ups, which usually last around three months.
The French audit will test the reactors' capacity to resist flooding, earthquakes, power outages, failure of the cooling systems and operational management of accidents.
The tests will be carried out in coordination with the French institute for radiation protection and nuclear safety (IRSN) and should also bring in experts from other countries and members of the public.
Europe's energy chief said last week some European nuclear reactors could fail the most stringent safety norms in the stress testing the bloc is planning.
(Reporting by Marie Maitre; Writing by Muriel Boselli, editing by Jane Baird)