I’ve been told on here that can’t happen with a LWR. I was told to ‘educate myself’ on the matter.
“While the two previous explosions were hydrogen blasts, caused by a buildup of steam in the reactor unit, this time officials are not sure what the cause was.”
That, plus the fact that radiation is going on, seems to indicate another hydrogen blast.
The containment is still intact. If it were not, you’d expect to see radiation increasing.