Severe accident in a light water reactor: Influence of elevated initial temperature on hydrogen combustion

The effect of initial temperature on turbulent flame acceleration and deflagration-detonation transition (DDT) was investigated experimentally in an explosion tube (length 6 m, diameter 66 mm) with various obstacle courses in the flame path. The experiments were performed at initial temperatures between 80 C and 300 C with H2/air/steam mixtures containing 8 to 20% H2 and up to 55% steam by volume. Flame speed measurements indicate that the mixture ranges allowing a turbulent flame acceleration and a DDT become wider as the initial temperature is increased. Depending on the geometric boundary conditions, however, also damping effects can come into force leading to lower flame speeds in a given mixture