Overview of hydrogen combustion experiments performed in a large scale vented vessel at Canadian Nuclear Laboratories

Hydrogen combustion inside a post-accident containment environment may pose a threat to the integrity of the containment structure and equipment. In CANDU reactors, combustion-generated overpressures in an accident will be relieved by venting to adjacent from one compartment volumes through relief panels or existing openings. To have a better understanding of the fundamental mechanisms that control the overpressures resulting from a vented hydrogen deflagration, a 120 m3 large scale vented combustion test facility was constructed at Canadian Nuclear Laboratories. A number of experiments have been completed in this facility to investigate hydrogen combustion behavior simulated in a post-accident reactor containment environment. A selected number of experimental results are presented in this paper to demonstrate several parameter effects on vented combustion dynamics by varying the number of chambers (single, two or three interconnected), volume and vent size, initial turbulence (quiescent vs. turbulent), initial temperature and steam concentration, mixture uniformity (well mixed vs. highly stratified), vent locations, and number of igniters. These results have provided useful insights for hydrogen management for the Canadian nuclear industry and CANDU utilities participating in the CANDU Owners Group research program. Most experimental data have been used for validation of combustion models and development of user guidelines.