Hydrogen deflagration experiments performed in a multi-compartment containment

In the event of a beyond-design accident in an LWR, large amounts of hydrogen may be generated by core degradation (Zircaloy oxidation) and released into the containment where it may lead to an explosion (deflagration in H2-lean mixtures, detonation in H2-rich mixtures). Therefore hydrogen behavior in a containment is an important concern in reactor safety. Former hydrogen explosion experiments in single-compartment test facilities suggested that deflagrations generally result in moderate pressure build-ups. Subsequently hydrogen research has been directed primarily at a possible transition from deflagration to detonation (DDT) from which safety-relevant pressure peaks are expected and which may occur at H2-concentration levels above 14 vol% H2. More recent multi-compartment hydrogen deflagration experiments in the 640-m3 Battelle-Frankfurt model containment, however, resulted in unexpectedly high local pressure loads acting on the internal containment structures with the potential to threaten containment integrity even at H2 concentration levels as low as 9 to 10 vol% H2. The present paper deals with typical test results and a summary of the findings from this extended experimental program