Background: Thermal stress will be occurred in the Sodium Cooled Fast Reactor when it starts or stops

after a number of cycles

thermal fatigue damages will be emerged

especially in the connection areas of tees.Purpose: To study the relations between the angles and the fatigue life in tees.Methods: The thermal fatigue life and fatigue damage coefficient of the tees of different angles are computed by the ANSYS software.Results: This paper gives a function charactering the relations between the fatigue allowable intensity and the tee angle.Conclusions: The fatigue strength is reducing with the decreasing of angle

which can provide certain valuable reference for designing tee nuclear reactor.