Abstract
Thermal striping is one of the most important safety concerns for liquid metal cooled fast reactor. In a fast reactor, the coolant that flows out of the reactor core subassemblies has different temperature, and the mixing of the coolants with different temperatures results in a temperature oscillation, which may cause a high cycle thermal fatigue of thermocouple protector, thus affecting the life of the reactor structural materials. In order to study the effect of thermocouple protector on thermal fatigue of central measurement column caused by thermal striping, a finite element model was established. The cumulative use factor used for thermal fatigue evaluation was calculated based on the design fatigue curve of the material and the linear cumulative damage criterion, and the thermal fatigue calculation results of a moving conduits model were also given for contrast. The results showed that the maximum stress appeared in the welding position between the thermocouple and the center measurement column, and the stress oscillated with time at high frequency and gradually decayed to a stable state. In addition, the cumulative use factor of the thermocouple protector model was much less than 1.0, which meant that the thermocouple protector would not suffer from high cycle fatigue failure during the design life.
