4. periodical general overhaul of 900 MW reactors

In France 32 units are concerned by the 4. periodical general overhaul of 900 MW reactors whose purpose is to assess in which conditions their operating life can be extended. This overhaul is composed of works and a series of tests. The resistance test or hydraulic test in which the primary cooling system is submitted to a pressure 1.2 times higher than the pressure to which it was designed. The leakage testing of the containment building is also performed. The corrosion of the different components of the reactor is assessed and compared to what was expected. The configuration of the fuel in the reactor core is changed in order to limit the radiation impact on the pressure vessel. Concerning the main works to do: adding extra cooling systems for the spent fuel pool in order to reduce the drain-out risk, adding an extra system to remove heat from the containment building in case of core meltdown and implementing a device to confine the corium in case of core meltdown preventing the failure of the pressure vessel. (A.C.)