Author(s): A. Alemberti; L. Barucca
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Abstract: The purpose of this work is to assess the capability of RELAP5/mod3 to predict the behaviour of liquid metal two-phase flow mixture in a vertical channel. To achieve the above goal, the data obtained during an experimental test campaign performed by SOLMECS – Israel (ETGAR-3 facility) have been compared with the results of RELAP5/mod3 simulations. The investigation of these specific aspects of two-phase flow is justified by the development of next generation liquid metal cooled nuclear reactors that in many cases use a gas injection in the vertical channels above the core (risers) to provide natural circulation enhancement. The comparison between Relap5 calculations and experimental data shows that the experimental measurements are well predicted by the code if the gas pressure used in the simulation takes into account the pressure difference between the liquid and gas phase due to surface tension effect and drag force. DESCRIPTION OF ETGAR-3 FACILITY The ETGAR-3 loop (Fig. 1) consists of two vertical pipes connected at the bottom by a liquid metal heater (LM HEATER) and sharing a separator tank at the top. The heated liquid metal flows upward in the riser of the facility to the separator; in the downcomer the lead-bismuth flows downward and produces electric power in a single-phase liquid-metal MHD generator. In ETGAR-3 water-steam is introduced at the riser bottom, through a mixer, to enhance the lead-bismuth natural circulation. The overall height of the riser is about 8 meters. Pressure is measured in the vertical riser with a vertical spacing of about two meters. Such measurements (indicated as PI23, PI6, PI9, PI24 in Fig. 1) define three different vertical sections of the riser named in the following “lower” (PI23-PI6), “middle” (PI6-PI9) and “upper” section (PI9-PI24) starting from the lowest measurement point. For each tested condition (a total of 80 experimental points) the pressure at the separator, the liquid metal mass flow as well as the injected steam mass flow have been measured and the knowledge of these quantities, together with the other geometrical characteristics of the facility, are sufficient to perform two-phase flow simulation and code assessment against the experimental data. T M D P V O L 7 0 0 P I P E 5 0 0 1 3 1 2 1 1 1 0 9 8 7 6 5 4 3 2 1 T M D P V O L 3 0 T M D P V O L 4 0 Figure 1 – The ETGAR-3 Facility Figure 2 – Riser section Relap5 noding RELAP5/MOD3 CODE MODIFICATIONS The main code modifications needed to perform the simulation of the facility are related to the
Year: 2007