Something along these* lines. But somewhat irrelevant since the scanning mechanism would have the same performance concerns. If it can't be done, nevermind.
View attachment 11836
Not sure if I want to refer to cores, or boilers, or both here. Perhaps instead of "Boiling" I should have put "Hot".
And since "critical" has special meaning in nuclear physics, I'd probably change that to something else as well.
But hopefully you get the idea: a color-coded grid indicating the temperature-status of the reactor.
* Initial screenshot stolen completely without permission from Reika's video demonstrating the beta version of he control block.