[chimera]

Can't we assume some criticality based on temperatures going up under circumstances of massive water infusion?

You can assume it, but it is likely an incorrect assumption. Criticality would manifest itself in ways other than just heat production, and those manifestations would be more immediately detectable than the thermal effects. IOW, you're going to get radiation effects a lot sooner than you are thermal effects. And there has been no evidence of these characteristic radiation effects.

[rottndog]

Criticality would manifest itself in ways other than just heat production, and those manifestations would be more immediately detectable than the thermal effects.

I would assume that they have some level of source range nuclear instruments functioning and monitoring each plant.

Just a thought...the recovery from this will be very long term. I wonder about the feasibility of building a new containment structure around the whole plant to assist in said recovery...