MINIMUM PRESSURIZATION-TEMPERATURE CURVES
If the limit of the MPT curve is exceeded during critical operation, the usual action is to scram
the reactor, cool down and depressurize the PCS, and conduct an engineering evaluation prior
to further plant operation.
During hydrostatic testing, minimum pressurization temperature precautions include making sure
that desired hydrostatic pressure is consistent with plant temperatures so that excessive stress does
not occur. Figure 5 shows MPT curves for hydrostatic testing of a PWR PCS. The safe
operating region is to the right of the MPT curves. Other special hydrostatic limits may also
apply during testing.
Figure 5 PCS Temperature vs. Hydrotest Pressure