Simulation of CCFL in a PWR hot-leg pipe facility with CFD-3D

ALARIO JOHAN SARACHE PIÑA; GODINO, DARIO M.; CORZO SANTIAGO F.; DAMIAN E. RAMAJO

Belo Horizonte

Congreso; Semana Nacional de Enngenharia Nuclear e da Energia e Ciências das Radiações; 2022

In the design and operation of nuclear plants, it is important to consider possible scenarios in theevent of cooling circuit depressurization by loss of coolant accident (LOCA) of the reactor. Dueto the high pressures in the coolant circuit, a break in any part of it could be crucial, causing thefast evaporation of the water in the core and the consequent dry-out of the fuel. In this scenario,the core has to be immediately reflooded by the Emergency Core Cooling System through theinjection of cold water in the coolant circuit. But, it is expected that, during core flooding, acounter current steam-water flow be established, with water trying to flow toward the core andhigh-velocity steam flow leaving it. At this point the water circulation could stop because of thesteam flow. This is known as the Onset of Counter Current Flow Limit (CCFL). In CCFLdifferent two-phase flow regimes are present, but the segregated flow is predominant. Manyresearchers have tried to predict the state in which the Onset of CCFL occurs both byexperimental test facilities, and also by numerical tools such as RELAP5 and detailed CFD-3D,mostly based on the two-fluid Eulerian method (TF). However, in a previous work we havedemonstrated that the classic Volume of Fluid (VOF) method and sophisticated high orderPiecewise Linear Interface Calculation (VOF-PLIC) techniques are significantly more accuratethan the TF method to capture the free surface in complex disperse and segregated water-airproblems. This work addresses the CCFL phenomenon with CFD-3D simulation in openFOAMusing the VOF method to reproduce a well known CCFL test reported in literature. Thecomparison of numerical and experimental results allow us to conclude about the capability ofthe numerical models to predict the CCFL and the flow inversion before applying these modelsto solve a full scale nuclear installation.