Preventing a hydrogen explosion
In the containment structure (closed steel sphere) at Borssele is a system that immediately converts into water any hydrogen that might develop. The system is passive, and requires no power or controls. It therefore works under all conditions. A catalyst (platinum) in the recombiners ensures a controlled chemical reaction, to rule out the danger of explosions.
 The greatest underpressure is in the area immediately surrounding the primary system.
 The other areas inside the steel sphere have slightly less underpressure.
 The space between the concrete dome and the steel sphere has less still.
 Ambient pressure.