So traditional reactors like a pressurized water reactor or boiling water reactor, they're very, very hot water at very high pressures, and this means, essentially, in the event of an accident, if you had any kind of breach of this stainless steel pressure vessel, the coolant would leave the core.
Tradicionalni reaktori kao vodeni reaktor po pritiskom ili reaktor kipuće vode, su vrlo, vrlo  vruća voda pod vrlo velikim pritiskom, a to znači, u suštini, u slučaju nezgode, ako postoji bilo kakav proboj ovog spremnika od nehrđajućeg čelika pod pritiskom, rashladna tekućina bi napustila jezgru.