Hydrogen Combustion with Concentration Gradients in Experiments and Simulations - Preliminary Results of ENACCEF Benchmark

If/when hydrogen is produced during the core melt down in a severe nuclear accident and released into the reactor containment, normally non-uniform combustible mixtures are generated. These concentration gradients have a severe influence on flame acceleration and deceleration and therefore flame propagation across concentration gradients was ranked as a high importance issue in the EURSAFE tables. In order to assess the ability of CFD codes to predict these phenomena, a benchmark has been initiated, based on the ENACCEF experimental tests. This paper presents the first results of the ENACCEF benchmark and it has two parts: one on the performed experiments and a second on the numerical modelling. In the first part experiments, which were made in the ENACCEF test facility will be described. The facility is a vertical stainless steel setup, which totalizes a length of 4.9m. It is constituted of two main parts: the acceleration tube (length 3.2 m, inner diameter 154mm), and the dome (length 1.7 m, inner diameter 750 mm). The unique vertical layout of the ENACCEF test facility allows generating stable hydrogen/air/steam mixtures with concentration gradients. In the second part, the numerical modelling of the experiments in the ENACCEF facility is described using the CFD (Computational Fluid Dynamics) codes REACFLOW, TONUS and FLUENT. CFD codes allow such fine nodalisation of the test facility that the influence of hydrogen gradient can be studied in detail.

BENTAIB Ahmed;  BLEYER Alexandre;  WILKENING Heinz;  BARALDI Daniele;  TAKASUO Eveliina;  HUHTANEN Risto; 

2009-01-29

IRSN

JRC43164

http://www.sar-net.org/upload/s3-3.pdf,    https://publications.jrc.ec.europa.eu/repository/handle/JRC43164,