“I think he is correct on this, containment appears to be a identified weakness in this circa 1971 design.”
—I’m just correcting the claim that the Fukushima reactors are BWR-1 types. They’re actually all BWR-3 and higher:
As for containment flaws with this design- could well be, I don’t know. I’ll defer to the experts here.
Here is a generic cutaway of this design:
That said, though, the author describes the first containment as the zircaloy tubes. Check, they have those which we cannot see in this diagram because they are contained inside the bronze colored vessel.
The second containment is the "pressure cooker (bronze colored vessel) in which all the tubes are contained...check, they have that.
The third is the containment vessel, and it appears to have that as well with the big toroidal looking structure at the bottom.
So my impression is this author is describing this type okay...