NUMERICAL ANALYSIS OF THE PHEBUS CONTAINMENT THERMAL HYDRAULICS

摘要

This paper describes numerical analysis of the PHEBUS FP containment thermal-hydraulics. PHEBUS FP is an international project undertaken with the aim of evaluating the behavior of radioactive fission products released from a LWR. pressure vessel into the containment vessel during a hypothetical severe accident. Six integral in-pile tests have been planned and are being carried out at Cadarache, France. The European Union, the United States, Canada, Korea and Japan are participating in this project. From Japan, the Nuclear Power Engineering Corporation and the Japan Atomic Energy Research Institute are collaborating the other parties involved in the project. Since the behaviour of fission products is strongly dependent on the surrounding environmental conditions: accurate prediction of the thermal-hydraulics in the containment vessel is essential to accurately evaluate the behavior. Characteristics of condensation heat transfer in the presence of noncondensible gases play a key role in the PHEBUS thermal-hydraulics, especially under the condition of high noncondensible gas mass fraction. Many models for condensation heat transfer in the presence of noncondensible gases have been proposed. However, these models were not found suitable for PHEBUS analysis, because they were focused on the low noncondensible gas mass fraction condition. In this study, a single-phase multi-component code. TFLOW-FP has been newly developed to predict thermal-hydraulics in the PHEBUS FP containment. Moreover, a nem degradation factor correlation for the condensation heat transfer coefficient due to the presence of noncondensible gases has also been developed and incorporated into the code. This code was applied for analysis of the thermal-hydraulic benchmark tests and the first in-pile test, FPTO. The results show that the code can predict the total pressure, gas temperature distributions, the relative humidity in the containment vessel and steam condensation rate on the surface of condenser rods very well. [References: 18]