Thermal-hydraulic test facility for nuclear reactor containment: Engineering design methodology and benchmarking

Abstract

The paper describes detailed thermal and mechanical design procedure of a CONtrolled FLOw (CONFLO) facility and a complimentary Thermal HYdraulic test facility for CONtainment (THYCON), to investigate the post-severe accident scenarios in Nuclear Power Plant (NPP) containments, involving condensation of steam in the presence of non-condensable gases (NCGs), such as air and hydrogen/helium. The former setup allows the study of flow condensation of steam on flat surfaces kept inside a rectangular flow section of 250 mm × 200 mm, under different inlet conditions of mixture concentration, pressure and temperature. The latter is a large cylindrical chamber of total height = 3.6 m and diameter = 0.96 m (vessel volume of 2.7 m3), mimicking a containment, wherein steam condensation and mixing transport of non-condensable gases can be experimentally simulated, as per conditions close to accident scenarios. Parameters of interest are local and average condensation heat transfer coefficient, NCG concentrations, flow Reynolds number, volumetric Richardson number, operating gas/vapour pressure, temperature and inclination angle of condensing surfaces. After due benchmarking of both the setups, the generated experimental data is being used for developing the design equation(s) to model steam condensation in containment environments and for suggesting locations for condensers and passive autocatalytic recombiners essential for containment safety. Ongoing experiments are also providing data for the validation of computer codes. The thermal-hydraulic experiments suggest that the condensation heat transfer inside NPP containments is primarily governed by several interlinked phenomena, such as stratification, mixing, turbulence and condensation.