Pilar Barreira’s scientific contributions

Containment Design Basis Accident analysis are usually performed using lumped-parameters models as this kind of models do not require high computational resources. Moreover, they offer overall good results of average pressure and temperature evolution. However, in order to perform a detailed local analysis, a thermal-hydraulic behavior study of every containment room may be necessary. To achieve this goal, a more detailed containment 3D model is imperative for capturing the local phenomena which occurs during a mass and energy release accident. During the last years in the collaborative project between the UPM and CNAT, several Almaraz NPP containment 3D models have been developed. The most precise one, called Detailed Integral Model, is able to obtain results with a very high resolution. However, this approach requires also high computational resources. For this reason two new models, called Multi-Zone Models, were developed with a coarser nodalization and therefore a lower computational requirement is needed. In this paper, the new modeling approach is described. A LBLOCA has been simulated in the Multi-Zone Model and it has been compared with the results obtained from the Detailed Integral Model. After analyzing the results, it can be concluded that the thermal-hydraulic evolutions are similar although the local variables differ in some cases. Taking into account the differences between models, a criteria in the use of the different approaches described has been stated depending on the analysis objective.

The Fukushima accident has drawn attention even more to the importance of external events and loss of energy supply on safety analysis. Since 2011, several Station Blackout (SBO) analyses have been done for all type of reactors. The most post-Fukushima studies analyze a pure and straight SBO transient, but the Fukushima accident was more complex than a standard SBO. At Fukushima accident, the SBO was a consequence of an external flooding from the tsunami and occurred 40 min after an emergency shutdown (SCRAM) caused by the earthquake. The first objective of this paper is to assume the consequences of an external flooding accident in a PWR site caused by a river flood, a dam break or a tsunami, where all the plant is damaged, not only the diesel generators. The second objective is to analyze possible actions to be performed in the time between the earthquake event (that causes a SCRAM) and the external flooding arrival, which could be applicable to accidents such as dam failures or river flooding in order to avoid more severe consequences, delay the core damage and improve the accident management. The results reveal how the actuation of the different systems and equipments affect the core damage time and how some actions could delay the core damage time enough to increase the possibility of AC power recovery.