PHENOMENOLOGY & STABILITY ANALYSIS OF SELF-PRESSURIZED, NATURAL CIRCULATION, LOW THERMO-DYNAMIC QUALITY NUCLEAR REACTORS

MARCEL CHRISTIAN PABLO; DELMASTRO, DARÍO

Pisa

Conferencia; 15th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics (NURETH-15); 2013

The different phenomena involved in self-pressurized natural circulation, low quality nuclear reactors cause the resulting dynamics to be significantly different from that existing in PWRs, BWRs and also natural circulation BWRs. In order to understand the phenomenology of this type of reactors, an analytical approach of the reactor thermal-hydraulics is derived. In addition, the linear stability of such reactors is numerically investigated. As a result it is found that the flashing effect is crucial to correctly model the stability performance. Moreover, it is verified that the dominant destabilizing mechanism are density waves travelling through the chimney section corresponding to Type-I instabilities. It is also found the unstable region is only restricted to cases in which the two-phase boundary limit is located within a region bounded by the core outlet until the chimney middle. The model also shows the condensation occurring in the steam dome has a great impact in the reactor stability and thus can be used to improve the stability performance.