@SwiftOnSecurity As much as I love USCSB videos, this time they claim something that sounds nonsensical (that a gas's condensing will cause the temperature to fall further than if the substance was absent in the first place), so I'd dearly want to see an accident report in written form.
Eh, they don't mention anything like that in likely places in the report.
However, they do describe the heat exchanger setup: it was being fed gases from the reactor (and not liquids). Thus I expect that once it started to condense the vapor, it became much more effective at removing heat.
@robryk @SwiftOnSecurity
They're on their website:
https://www.csb.gov/file.aspx?DocumentId=6204