Method for making orifices in the secondary casings of a pressurized water reactor steam generator

摘要

The method involves ensuring whether a steam generator (1) is filled with water, and forming a pre-orifice using a mechanical drilling tool (15), where the pre-orifice does not emerge on a part of thickness of a pressure envelope (2). Water level in the generator is reduced just above the pre-orifice, and drilling of an orifice (9) in the envelope is terminated by an electro-erosion tool. An orifice (10) is formed in a heat exchanging tube bundle envelope (3) by the electro-erosion tool, where the orifices are co-axial to each other and have equal diameter.