Study of the injection of water into the primary pipes of a nuclear power plant in case of a maximum hypothetical accident

Current calculations assume, in a very pessimistic way, that the passage of steam through a 'healthy' loop, is completely obstructed by the injected water. To answer this position, it is above all to evaluate the pressure losses at the injection. The different types of flow encountered as well as the phenomena related to injection are first examined, in a qualitative way. Then the pressure losses of the whole circuit are experimentally determined, on a reduced model divided into various zones including an 'injection zone' and another simulating the pipe that connects the injection to the reactor (called 'continuation of the injection'). The calculation of the pressure losses for the 'continuation of the injection' is done by a method inspired by Martinelli and Govier. Of the pressure losses of the entire circuit, all those that do not fit into the 'injection zone' are then deducted to finally retain only the pressure losses: it is shown that they represent a preponderant part, and are expressed in the form of a general law. The purpose of the second part of the paper is to determine the instabilities, namely the passage from one wave flow model to another one of the 'annular mist' or 'dispersed bubble' type. These instabilities are studied by a classical method (from Lamb and Giotof) surface waves. These waves are studied in a three-dimensional way, following a similar reasoning to that of Moureau. Finally, the influence of the injection angle on the pressure losses is examined together with the quantitative importance of the projections (drops of water) which bypass the reactor and are lost at the level of the rupture of the primary pipe