Fluid and pressure oscillations occuring at direct contact condensation of steam flow with cold water

Pressure and fluid oscillations at pressure suppression containment and cold leg flow oscillations at Emergency Core Cooling Water Injection in water-cooled nuclear power reactors are studied concerning flow oscillations occuring at direct contact condensation of steam flow with cold water. Classifications and mechanisms of these oscillation patterns are presented. Linear frequency analyses are developed in explaining the oscillation frequency and oscillation threshold of both condensation oscillation and plug oscillation. Oscillation frequencies at chugging and at ON-OFF oscillation are examined with analytical models developed for such large amplitude oscillations. Analytical results with these models are compared with the data by simulation experiments. Discussions are made focusing on the applicability of the analyses. (orig.)