Use of RELAP50MOD3.3 Code to Get Fluid Dynamic Stability Maps

The analysis that has been carried out in the present paper shows the possibility to predict the onset of density wave oscillations by means of RELAP5/MOD3.3 code for simple geometry systems, whereas the difference between 1D and 3D approximations is not relevant for the purpose of the analysis; the shape of the boundary line in the stability maps is in agreement with the other authors prediction. The approximation used for helically coiled pipes in the multichannel systems seems not to affect the instability onset and the classical shape of the instability maps, that seem a powerful tool for the fluid dynamic instability prediction.