Exceeding Heatup and Cooldown Rates:

Commonly, exceeding  heatup or cooldown  limits or another potential operational  thermal  transient limitations is not an immediate hazard to continued operation and only needs an assessment of the impact on the future fatigue life of the plant. Therefore, this might depend upon the individual plant and its limiting parts.

Individual  parts,  such  as  the  pressurizer,  might  have  specific  heatup  and  cooldown limitations in which, in most cases, are less restrictive than for the PCS.

Because of the cooldown transient limitations of the PCS then the reactor should be shut down in an orderly manner.  The Cooldown of the PCS from full operating temperature to 200ºF or less requires around 24 hours (depending upon cooldown limit rates) as a minimum. Needs might vary from plant to plant.