[GOPJ]

I assume that these hydrogen recombiners were installed in the secondary containment at Fukushima. However, recombiners require an electric power supply to operate the fans to draw in the hydrogen/steam mix. In my opinion, with no power at Fukushima, the hydrogen just accumulated until an explosive concentration was achieved.

Would this system - the recombiners - have backups?

[Fido969]

In my opinion, with no power at Fukushima, the hydrogen just accumulated until an explosive concentration was achieved.

Couldn't they just open a window?

One good thing I noted was that the steel superstructure of the first building to explode was still there. That makes the outer containment building more like a "blow-off" valve, and at least gives a limitation (although a high one) to the force of the explosion.