BORON
You are probably correct, boronated water for the ‘slick’ system. Not a coolant actually, a fission poison.
What I have read seems to indicate that the boronated water system is still intact though. I am guessing they don’t want to fire it off and poison the whole loop. I’m not sure that will do much anyway. If the control rods fully inserted, there shouldn’t be any fission activity. What they have is decay heat.
OTOH, if they have lost the core geometry and fission is still going on, then they aren’t saving anything and may as well fire the boron. The reactor is trashed already.
But then again, I’m no nuclear engineer (even though I did once stay at a Holiday Inn Express). If there is someone out there who actually knows the operational specifics and can educate me, I’m all ears.