Development of Evaluation Method for Impact of Aircraft Fuel Explosion and Fire on BWR Reactor Building

A method was studied to evaluate the influences of aircraft fuel explosion and consecutive fire that would be expected to occur after a postulated aircraft crash on a BWR reactor building. In addition to the classical semi-empirical method for vapor cloud explosion (VCE) to evaluate overpressure, The Fire Dynamics Simulator version 6 (FDS6) was applied to analyze the fireball evolution by combustion of the dispersed fuel droplets, and the consecutive pool fire. The FDS spray model was used to simulate the fuel droplet dispersal. Input parameters such as droplet initial velocity and initial dispersal direction were presumed on the basis of the observations from the IMPACT water missile experiment. Our calculation result was in good agreement with the experimental data in terms of the droplet ‘cloud’ expanding speed by approximately 20%. This modeling manner for the droplet dispersal was also applied to the analysis of explosion in a middle-size commercial aircraft crash to the sidewall of a building that assumed a BWR reactor building. The analysis predicted that approximately 60% of aircraft fuel would be consumed in the initial fireball and most of the residual fuel would attach to the ground area close to the wall. This result can be used for the realistic determination of the initial mass and position of the residual aircraft fuel to evaluate wall integrity against thermal attack and transport of the combustion products from the secondary fire.