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NKS Programme Area:
Severe accidents and Reactor Physics
Three-dimensional Simulation of Hydrogen Detonations in the Olkiluoto BWR Reactor Building
Ari Silde, Reinhard Redlinger
This report describes the numerical simulations of hydrogen detonations in Olkiluoto reactor building room
B.60.80 using the DET3D code. The code is developed at Forschungszentrum Karlsruhe (FZK) and uses
the finite difference method based on three-dimensional Euler equations for a multicomponent reacting
gas. DET3D is mainly developed for modelling of gaseous detonations initiated by a direct ignition. DDT
phenomena are not treated.
The initial conditions of the detonation simulation were based on previous hydrogen spreading analyses
carried out with the FLUENT code. DET3D calculations continued the previous, rough estimates of shock
pressure loads performed with a simple DETO code. The DETO analyses were based on the strong
ignition theory with oblique and normal reflection relations of the adiabatic shock waves. Shock waves
were induced by point-like energy release without modelling of the propagating combustion front. In the
DETO modelling, only the first shock reflection was treated. The approach of the DET3D code enables the
more detailed assessment of detonation pressure loads in a real 3-D geometry.
The objective of the work was to assess the pressure loads on room structures under detonation
The initial conditions of detonation simulation were based on the previous hydrogen spreading analyses
performed with the FLUENT code. Two sizes of leakage from the containment to the reactor building were
considered: 2 mm2, which corresponds to the nominal leakage of containment, and a large leak of 20 mm2.
The DET3D simulation indicated that the highest pressure spikes occurred in the room corners due to
reflections and superposition of the shock waves. The highest pressure maximum in all simulation cases
was about 10.6 MPa. This value was obtained in the upper corner of the room beside the containment
wall. The highest pressure impulses to structures during the 150 ms simulation were about 30 - 35 kPa-s.