Methodology for Evaluation of Hydrogen Safety in a NPP Containment

A free volume of a NPP containment must be large enough to prohibit an occurrence of a containment-wise global detonation by limiting global averaged hydrogen concentration below 10 vol%. In the frame of a technology development to evaluate accident management strategy for containment hydrogen mitigation, it is on-going to develop an analytical tool, containmentFOAM, for a turbulence-resolved detail analysis of hydrogen behaviors in a NPP containment based on OpenFOAM. It is composed of h2MixingFoam for turbulent mixing of hydrogen with steam condensation, h2RecombinerFoam for PAR performance evaluation, h2FlameFoam for turbulent hydrogen combustion, and h2SprayFoam for spray effect on hydrogen behaviors. As such, containmentFOAM is designed to be modular in order to overcome numerical problems from length and time scales. A time period of hydrogen release to a NPP containment during a severe accident is in the order of 10,000 s, but the time scale to resolve turbulent flame propagation by hydrogen combustion is below 1 s. And the time scale is directly coupled with length scales. So the development of the analysis codes based on modular structure gives benefits in managing and using the codes. In the object-oriented modular libraries, physical models required for a simulation can be chosen at run-time and the model objects are constructed at that time.