It depends on the plant.It depends on whether it's a boiling-water reactor or a pressurized-water reactor.

When construction began in 1969, Metsamor was a VVER 440, Model 230, an example of one of the earliest pressurized-water nuclear plant designs, developed by the Soviets between 1956 and 1970.

Geologists therefore wondered whether the friction between the plates was being reduced by pockets of pressurized water within the fault that push the plates away from each other.