DOE-HDBK-1017/2-93
Brittle Fracture
HEATUP AND COOLDOWN RATE LIMITS
HEATUP AND COOLDOWN RATE LIMITS
Personnel operating a reactor plant must be aware of the heatup and cooldown
rates for the system. If personnel exceed these rates, major damage could occur
under certain conditions.
EO 1.12
IDENTIFY the basis used for determining heatup and cooldown
rate limits.
EO 1.13
IDENTIFY the three components that will set limits on the heatup
and cooldown rates.
EO 1.14
STATE the action typically taken upon discovering the heatup or
cooldown rate has been exceeded.
EO 1.15
STATE the reason for using soak times.
EO 1.16
STATE when soak times become very significant.
Basis
Figure 6 Heatup and Cooldown Rate Limits
Heatup and cooldown rate limits, as
shown in Figure 6, are based upon the
impact on the future fatigue life of the
plant.
The heatup and cooldown
limits ensure that the plant's fatigue
life is equal to or greater than the
plant's
operational
life.
Large
components such as flanges, the
reactor vessel head, and even the
reactor vessel itself are the limiting
components.
Usually the most
limiting component will set the heatup
and cooldown rates.
Thermal stress imposed by a rapid
temperature change (a fast ramp or
even a step change) of approximately
20F (depending upon the plant) is
insignificant (106 cycles allowed
depending upon component) and has no effect on the design life of the plant.
Rev. 0
Page 11
MS-04
