TRANSITION FROM SLOW DEFLAGRATION TO DETONATION
The report reviews external vapour cloud explosion phenomena, especially transition from deflagration to detonation, in the context of nuclear power plant safety, for explosions postulated according to the B.M.T. guideline Chemical Explosions. Damage analyses of recorded accidents show that fast deflagration, not detonation, explains their consequences. Subsequently, laboratory and large-scale trials are surveyed and safety related conclusions drawn. Large unconfined cloud field trials (Maplin Sands, China Lake), for propane - butane, evidence negligible overpressures (a few millibar). Balloon tests, for stoichiometric hydrogen - air mixture, up to 2000 m**3, yielded about 60 millibar max. Flame acceleration due to obstacles, nets, turbulence inducing structures was investigated. Small- to large- scale trials, with hydrogen - air mixtures, show that transition to detonation is restricted to jet ignition. Main safety related conclusions are: + detonation need not be postulated. Even a partially confined stoichiometric hydrogen - air cloud generates less than 0.3 bar; + jet ignition should be avoided by appropriate design; + turbulence inducing obstacles: gratings, pipes, corners merely produce local overpressures and cannot cause transition to detonation.
Bibliographic Reference: EUR 9354 EN (1984) MF, 59 P., BFR 120 BLOW-UP COPY BFR 295, EUROFFICE, LUXEMBOURG, POB 1003
Availability: Can be ordered online
Record Number: 1989122096300 / Last updated on: 1987-01-01
Available languages: en