A sensitivity study on the performance of a passive system

A procedure suitable for establishing the performance of a passive system was proposed in the past from ENEA, Polytechnic of Milan and University of Pisa. The general objective of the activity was to characterize the transient thermalhydraulic performance of the passive system in probabilistic terms. This procedure has been adopted in a sample application concerning a natural circulation loop including an Isolation Condenser and the Reactor Pressure Vessel where power production occurs. In the framework of the RMPS Project (EU 5th FWP), the University of Rome has carried out an application of the procedure performing several calculations using the RELAP5 mod. 3.1 and 3.2 code versions. In the evaluation of the indicators of system performance, a linear correlation between two of these (the energy transferred through the Isolation Condenser and the integrated mass flow at the IC inlet, normalized with respect to results of a reference calculation) has been evidenced. To better understand if these two parameters are actually correlated in all the hypothetical configurations, a sensitivity analysis on a design parameter (the initial RPV liquid collapsed level) has been performed. The results obtained show that some initial configurations of the system, not considered in the probability distributions adopted in the application of the procedure, may lead to a different correlation between the two indicators. The results are discussed and a quantitative analysis of the different correlations existing between the energy transferred and integrated mass flow has been attempted.