France declares level 2 nuclear event at Cattenom

* Reactors not shut down after the fault was found

* EDF given 10 days on Jan. 24 to make repairs

* There were four level two events in 2011

PARIS, Feb 6 (Reuters) - France's nuclear safety authority (ASN) said on Monday it had identified a problem with water pipes at one of EDF's nuclear plants and rated it a level two event out of a maximum seven on the international nuclear event scale (INES).

Level two ratings occur relatively rarely, but the watchdog said there was no impact on plant workers or the environment from the event.

In 2011, the ASN gave four incidents a level two rating. Japan's Fukushima disaster was rated a level seven event.

Pipes used to pump water into fuel rod cooling pools at reactors 2 and 3 at EDF's Cattenom nuclear plant were not equipped with a mechanism to prevent them from accidentally pumping water out of the basins.

In case water levels fall in rod cooling pools, the exposed fuel would heat up and release dangerous radioactive material.

"Due to the potential consequences, this event was placed on a level 2 of the INES scale," the watchdog said in a statement.

The nuclear reactors were not shut down after the fault was found as the fuel rods concerned were located in the storage pools rather than in the reactors themselves, an ASN spokeswoman said.

The nuclear watchdog asked EDF to put in place measures to prevent the pools from emptying quickly and to rectify the problem within 10 days from Jan. 24, when the watchdog first inspected the situation.

On Feb. 1 and Feb. 3, the operator fixed the pipes and an ASN inspector verified the changes were made appropriately.

Two other reactors at Cattenom in north-east France had the correct mechanism in place, ASN said. (Reporting by Karolin Schaps; Edited by Muriel Boselli and Jason Neely)