Simulation of a small loss of coolant accident by using RETINA V1.0D code

RETINA has been developed for modeling of two-phase flow situations in full-scope simulators of nuclear power plants. A special feature of RETINA is that both RETINA V1.0D (drift-flux — 5 equations) and RETINA V1.0-2V (two-fluid — 6 equations) approach are available in the code and the same constitutive relations are used in both cases. The governing equations are discretized implicitly, and an automatic derivation algorithm determines the Jacobian matrix, which is partitioned taking into account the special structure of nuclear power plants. Partitioned inverse formula is used to solve the global equation system providing the possibility of multi-level parallelization. Heat structures are modeled in two dimensions and are coupled to the flow equations explicitly. Since the code will be used in real-time simulators, we paid special attention to time-effective solution. In this paper, we demonstrate the ability of our code by simulating a small loss of coolant accident Paks Model Circuit (PMK). The simulation results are compared to real measurements obtained by Paks Model Circuit.