Nuclear Energy Agency Online Bulletin

October 2000

Nuclear Safety Information

New state-of-the-art report on flame acceleration and deflagration-to-detonation

Flame acceleration (FA) and deflagration-to-detonation (DDT) are important phenomena in severe accidents because they can largely influence the maximum loads from hydrogen combustion sequences and the consequential structural damage to nuclear power plants. The ultimate goal in hydrogen mitigation is to design countermeasures that allow operators to avoid FA and DDT. In current nuclear power plants, the load-bearing capacity of the main internal structures is jeopardised by flame speeds in excess of about 100 meters per second. New containment designs could, in principle, be constructed to carry higher dynamic loads, but with additional costs. To judge the potential for fast flames and DDT, the causes and underlying processes have to be understood. Criteria may then be derived that can be used in three-dimensional numerical containment simulations, testing the effectiveness of hydrogen mitigation methods, to decide whether FA or even DDT is possible.

A new state-of-the-art report (SOAR) on flame acceleration and deflagration-to-detonation transition [NEA/CSNI/R(2000)7] was released by the NEA Committee on the Safety of Nuclear Installations (CSNI). It included information from very significant, new experimental and theoretical projects that had been run in the United States, Japan, Germany, France, Canada, the Russian Federation, and under the auspices of the European Commission.